Progress 09/01/12 to 08/31/17
Outputs
Target Audience:Scientific community; practicing veterinarians; veterinary students Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?One PhD was awarded based in this research. How have the results been disseminated to communities of interest?The results of this research have been published in refereed journals and disseminated through conference proceedings and lectures to veterinary students What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Prior to this research, very little was known about the pathogenesis of exercise-induced pulmonary hemorrhage (EIPH). This research has elucidated important mechanisms of the disease. First we demonstrated that one of the distinctive histopathologic lesions in EIPH is remodeling of pulmonary veins. We also demonstrated that this lesion is pivotal in EIPH pathogenesis. We described remodeling of pulmonary veins in detail, and we have reasoned that this remodeling could result in increased pulmonary capillary pressure upstream from the veins. During exercise, these pulmonary capillary pressures may be sufficiently high to rupture, causing EIPH. One of the important unresolved questions about EIPH was why lesion occur primarily in the caudal dorsal lung region. We demonstrated that pulmonary veins from the caudal dorsal lung region had a greater degree of remodeling than veins from the cranial ventral region. Furthermore, we reported that these veins were physically stiffer. We speculate that that the remodeling and increased stiffness of the veins could result in higher upstream capillary pressure and EIPH. We finally demonstrated that endothelium -dependent dilation differs in veins harvested from cranial ventral and caudal dorsal regions of the lung. Veins from the caudal dorsal region exhibit less dilation in response to agonists, thereby potentially contributing to the caudal dorsal distribution of EIPH.
Publications
- Type: Journal Articles
Status: Accepted
Year Published: 2016
Citation:
Derksen F, Williams K, Stack A.(2011.Exercise-induced pulmonary hemorrhage in horses: the role of pulmonary veins. Compend Contin Educ Vet. 2011;33(4):E1-6.
(Not Available)N/A (Not Available)N/A
Williams KJ, Derksen FJ, Defeijter-Rupp HL, Robinson NE.Repeated blood instillation into the airway of the horse does not cause pulmonary fibrosis. Equine Vet J. 2011 May;43(3):354-358.
(Not Available)N/A (Not Available)N/A
No publications reported this period
(Not Available)N/A (Not Available)N/A
Effects of exercise on markers of venous remodeling in lungs of horses.
Stack A, Derksen FJ, Sordillo LM, Williams KJ, Stick JA, Brandenberger C, Steibel JP, Robinson NE.
Am J Vet Res. 2013 Sep;74(9):1231-8. doi: 10.2460/ajvr.74.9.1231.
Journal Articles 2013
Distribution of venous remodeling in exercise-induced pulmonary hemorrhage of horses follows reported blood flow distribution in the equine lung.
Williams KJ, Robinson NE, Defeijter-Rupp H, Millerick-May M, Stack A, Hauptman J, Derksen FJ.
J Appl Physiol (1985). 2013 Apr;114(7):869-78. doi: 10.1152/japplphysiol.01170.2012. Epub 2013 Jan 31.
Journal Articles 2013
Reply to Pancheva, Panchev, and Pancheva.
Robinson NE, Williams KJ, Stack A, Derksen FJ, Hauptman J, Millerick-May M, DeFeijter-Rupp H.
J Appl Physiol (1985). 2013 Aug 1;115(3):413. doi: 10.1152/japplphysiol.00544.2013.
Journal Articles 2013
J Appl Physiol (1985). 2014 Aug 15;117(4):370-6. doi: 10.1152/japplphysiol.00314.2014. Epub 2014 Jun 12.
Lung region and racing affect mechanical properties of equine pulmonary microvasculature.
Stack A1, Derksen FJ1, Williams KJ2, Robinson NE1, Jackson WF3.
Journal Articles 2014
J Appl Physiol (1985). 2016 Mar 15;120(6):599-607. doi: 10.1152/japplphysiol.00975.2015. Epub 2016 Jan 14.
Regional heterogeneity in the reactivity of equine small pulmonary blood vessels.
Stack A1, Derksen FJ2, Williams KJ3, Robinson NE2, Jackson WF4.
Author information
- Type: Journal Articles
Status: Accepted
Year Published: 2016
Citation:
Derksen FJ, Williams KJ, Uhal BD, Slocombe RF, de Feijter-Rupp H, Eberhart S, Berney C, and Robinson NE.(2007). Pulmonary response to airway instillation of autologous blood in horses.Equine Vet J.39(4):334-339.
(Not Available)N/A (Not Available)N/A
Williams KJ, Derksen FJ, de Feijter-Rupp H, Pannirselvam R, Steel CM, and Robinson NE. (2008).Regional Pulmonary Veno-occlusion: A Newly Identified Lesion of Equine Exercise-Induced Pulmonary Hemorrhage Americal Journal of Veterinary Pathology. In press.
(Not Available)N/A (Not Available)N/A
Derksen FJ, Robinson NE, Pannirselvam R, DeFeijter-Rupp H, Steel CM, and Williams KJ. (2007) Venous occlusion accompanies bleeding, hemosiderosis and fibrosis in horses with exercise-induced pulmonary hemorrhage.In proceedings American Association of Equine Practitioners meeting, Orlando Florida (P65-67)
(Not Available)N/A (Not Available)N/A
Williams KJ, Derksen FJ, de Feijter-Rupp H, Pannirselvam RR, Steel CM, Robinson NE.(2008)Regional pulmonary veno-occlusion: a newly identified lesion of equine exercise-induced pulmonary hemorrhage. Vet Pathol. 45(3):316-26.
(Not Available)N/A (Not Available)N/A
Derksen, F. J., Williams K. J., Pannirselvam, R.R., De Feijter-Rupp H., Steel, C. M.,Robinson, N. E.(2008)Regional Distribution of Collagen and Hemosiderin in the Lungs of Horses with Exercise-induced Pulmonary Hemorrhage, Equine Veterinary Journal (in press)
(Not Available)N/A (Not Available)N/A
Derksen F.J., (2008)Pulmonary Venous Remodeling in Equine Exercise Induced Pulmonary Hemorrhage. Page 12 in Proc. Havemeyer Foundation workshop on EIPH, San Diego CA.
(Not Available)N/A (Not Available)N/A
Derksen FJ, Williams KJ, Pannirselvam RR, de Feijter-Rupp H, Steel CM, Robinson NE. Regional distribution of collagen and haemosiderin in the lungs of horses with exercise-induced pulmonary haemorrhage. Equine Vet J. 2009 Jul;41(6):586-91.
(Not Available)N/A (Not Available)N/A
No publications reported this period
(Not Available)N/A (Not Available)N/A
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Progress 10/01/15 to 09/30/16
Outputs
Target Audience:Target audience includes veterinary academicians, practicing veterinarians, veterinary students and the horse owning public. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?The results of this research has been published in refereed journals and disseminated through conference proceedings and lectures to veterinary students. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Regional differences in large equine pulmonary artery reactivity exist. It is not known if this heterogeneity extends into small vessels. The hypothesis that there is regional heterogeneity in small pulmonary artery and vein reactivity to sympathomimetics (phenylephrine and isoproterenol) and a parasympathomimetic (methacholine) was tested using wire myography on small vessels from caudodorsal (CD) and cranioventral (CV) lung of 12 horses [9 mares, 3 geldings, 8.67 ± 0.81 (age ± SE) yr, of various breeds that had never raced]. To study relaxation, vessels were precontracted with U46619 (10(-6) M). Methacholine mechanism of action was investigated using L-nitroarginine methylester (L-NAME, 100 μM) and indomethacin (10 μM). Phenylephrine did not contract any vessels. Isoproterenol relaxed CD arteries more than CV arteries (maximum relaxation 28.18% and 48.67%; Log IC50 ± SE -7.975 ± 0.1327 and -8.033 ± 0.1635 for CD and CV, respectively, P < 0.0001), but not veins. Methacholine caused contraction of CD arteries (maximum contraction 245.4%, Log EC50 ± SE -6.475 ± 0.3341), and relaxation of CV arteries (maximum relaxation 40.14%, Log IC50 ± SE -6.791 ± 0.1954) and all veins (maximum relaxation 50.62%, Log IC50 ± SE -6.932 ± 0.1986) in a nonregion-dependent manner. L-NAME (n = 8, P < 0.0001) and indomethacin (n = 7, P < 0.0001) inhibited methacholine-induced relaxation of CV arteries, whereas indomethacin augmented CD artery contraction (n = 8, P < 0.0001). Our data demonstrate significant regional heterogeneity in small blood vessel reactivity when comparing the CD to the CV region of the equine lung.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
J Appl Physiol (1985). 2016 Mar 15;120(6):599-607. doi: 10.1152/japplphysiol.00975.2015. Epub 2016 Jan 14.
Regional heterogeneity in the reactivity of equine small pulmonary blood vessels.
Stack A1, Derksen FJ2, Williams KJ3, Robinson NE2, Jackson WF4.
Author information
|
Progress 10/01/14 to 09/30/15
Outputs
Target Audience:The target audience include veterinarians, veterinary students, scientists, and the public. Changes/Problems:During the next reporting period, I plan to shift my emphasis to the Borlaug Higher Education Agricultural Research and Development Program (BHEARD), for which I served as principal investigator. As part of the U.S. Government's Feed the Future Initiative, the BHEARD program is funded by the United States Agency for International Development (USAID), through the International Maize and Wheat Improvement Center (CIMMYT) in Mexico. Honoring the legacy of Nobel Peace Prize Laureate Norman Borlaug, the BHEARD program is a major new effort to increase the number of agricultural scientists and strengthen scientific institutions in developing countries. The BHEARD program also aims to develop, test and evaluate new models of capacity development. The program will support long-term training of agricultural researchers at the master's and doctoral levels and will link scientific and higher education communities in Feed the Future countries and the United States. BHEARD scholarships will support course work (2 years for MS and 3 years of PhD) at U.S. or other universities, and field research in the student's home country, as well as providing a variety of allowances to cover related training costs. In addition, the BHEARD program allows for a broader set of human and institutional capacity-building, particularly if additional USAID mission or leveraged funds can be mobilized. What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period, I plan to shift my emphasis to the Borlaug Higher Education Agricultural Research and Development Program (BHEARD), for which I served as principal investigator. As part of the U.S. Government's Feed the Future Initiative, the BHEARD program is funded by the United States Agency for International Development (USAID), through the International Maize and Wheat Improvement Center (CIMMYT) in Mexico. Honoring the legacy of Nobel Peace Prize Laureate Norman Borlaug, the BHEARD program is a major new effort to increase the number of agricultural scientists and strengthen scientific institutions in developing countries. The BHEARD program also aims to develop, test and evaluate new models of capacity development. The program will support long-term training of agricultural researchers at the master's and doctoral levels and will link scientific and higher education communities in Feed the Future countries and the United States. BHEARD scholarships will support course work (2 years for MS and 3 years of PhD) at U.S. or other universities, and field research in the student's home country, as well as providing a variety of allowances to cover related training costs. In addition, the BHEARD program allows for a broader set of human and institutional capacity-building, particularly if additional USAID mission or leveraged funds can be mobilized. BHEARD
Impacts
What was accomplished under these goals?
Phenylephrine did not contract smooth muscle in any vessels, whereas isoproterenol relaxed arteries pre-contracted with U46619 (CD to a greater degree than CV), but not veins. Methacholine caused contraction of CD arteries, and relaxation of CV arteries and all veins in a non-region dependent manner. L-NAME and indomethacin inhibited methacholine-induced relaxation of CV arteries, whereas indomethacin augmented CD artery contraction. Our data demonstrate significant regional heterogeneity in the reactivity of small blood vessels in the equine lung. Extrapolation of these data to increased sympathetic and decreased parasympathetic tone during exercise predicts that highest capillary pressures occur in CD lung, which is also the region to which blood flow is preferentially distributed both at rest and during exercise.
Publications
|
Progress 10/01/13 to 09/30/14
Outputs
Target Audience: The target audience include veterinarians, veterinary students, scientists, and the public. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The project provided an opportunity for PhD level training for Dr. Alice Stack. Dr. Stack obtained her PhD during the reporting period. How have the results been disseminated to communities of interest? The results of this project have been disseminated to research scientist through the publication of a refereed journal article, to practicing veterinarians through continuing education programs offered by the college of veterinary medicine at Michigan State University, and to veterinary students through the incorporation of the new material in lectures. What do you plan to do during the next reporting period to accomplish the goals? During the next reporting period, I plan to shift my emphasis to the Borlaug Higher Education Agricultural Research and Development Program (BHEARD), for which I served as principal investigator. As part of the U.S. Government’s Feed the Future Initiative, the BHEARD program is funded by the United States Agency for International Development (USAID), through the International Maize and Wheat Improvement Center (CIMMYT) in Mexico. Honoring the legacy of Nobel Peace Prize Laureate Norman Borlaug, the BHEARD program is a major new effort to increase the number of agricultural scientists and strengthen scientific institutions in developing countries. The BHEARD program also aims to develop, test and evaluate new models of capacity development. The program will support long-term training of agricultural researchers at the master's and doctoral levels and will link scientific and higher education communities in Feed the Future countries and the United States. BHEARD scholarships will support course work (2 years for MS and 3 years of PhD) at U.S. or other universities, and field research in the student’s home country, as well as providing a variety of allowances to cover related training costs. In addition, the BHEARD program allows for a broader set of human and institutional capacity-building, particularly if additional USAID mission or leveraged funds can be mobilized. BHEARD
Impacts
What was accomplished under these goals?
Exercise-induced pulmonary hemorrhage (EIPH) is a ubiquitous, performance-limiting condition of racehorses that results in severe pulmonary pathology. Pathologic changes include venous remodeling of small intralobular pulmonary veins. Pathology is limited to the caudodorsal (CD) lung, which is also the region to which blood flow is preferentially distributed. Mechanical properties of the equine pulmonary microvasculature have not been studied. We tested the following hypotheses: regional differences in pulmonary artery and vein mechanical characteristics do not exist in control animals; and racing, and associated venous remodeling impact pulmonary vein mechanical properties in CD lung only. Pulmonary arteries and veins (mean internal diameter range 207 – 386 µm) were harvested from 8 control (unraced) and 7 raced horses. Vessels from CD and cranioventral (CV) lung were mounted on a wire myograph and passively stretched in 10 µm diameter increments until failure. Peak wall tension was recorded and plotted against changes in vessel diameter (length). Length-tension data were compared between vessel type (artery and vein), lung region (CD and CV), and horse status (control and raced). Pulmonary veins are stiffer-walled than pulmonary arteries. In control and raced horses, caudodorsal pulmonary arteries are stiffer than cranioventral arteries, while cranioventral pulmonary veins are stiffer than caudodorsal veins. Racing was associated with increased stiffness of caudodorsal pulmonary veins, and, to a lesser extent, cranioventral arteries. This study is the first to document regional differences in small pulmonary vessel wall mechanics in any species, and provides support for a significant role of pulmonary vein remodeling in EIPH pathogenesis.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
J Appl Physiol (1985). 2014 Aug 15;117(4):370-6. doi: 10.1152/japplphysiol.00314.2014. Epub 2014 Jun 12.
Lung region and racing affect mechanical properties of equine pulmonary microvasculature.
Stack A1, Derksen FJ1, Williams KJ2, Robinson NE1, Jackson WF3.
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Scientific community; practicing veterinarians; veterinary students. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The project has served as the basis for a PhD thesis by Dr. Alice Stack. Furthermore, the open lung biopsy technique used in this study was performed by veterinary surgeons in training supervised by senior veterinary surgeons. The open lung biopsy technique provided a unique training opportunity for these surgical residents. How have the results been disseminated to communities of interest? The results of this project have been disseminated to research scientist through the publication of a refereed journal article, to practicing veterinarians through continuing education programs offered by the college of veterinary medicine at Michigan State University, and to veterinary students through the incorporation of the new material in lectures. What do you plan to do during the next reporting period to accomplish the goals? During the next reporting period, we plan to use Wire Myography to study pulmonary veins harvested from control horses and horses affected with EIPH. Vessels will be mounted as a cylinder on 2 stainless steel 40-μm diameter wires, the wires secured, and all vessels will be submerged throughout the experiment. The bath fluid will be heated slowly to 37°C. Vessel length will be recorded using a previously calibrated microscope, and the micrometer reading at which the wires are barely touching (parallel) will be recorded. Wires will then be separated by use of the micrometer until the transducer registered a force. The micrometer reading will again be recorded. From that point, wires will be separated from one another in 10-μm increments. The peak force achieved at each micrometer adjustment will be recorded. Vessels will be stretched in this stepwise manner until stretching resulted in no further increase, or a decrease in force (interpreted as vessel failure).
Impacts
What was accomplished under these goals?
Venous remodeling of small pulmonary veins in caudodorsal lung is a characteristic lesion of exercise-induced pulmonary hemorrhage, a ubiquitous, performance-limiting condition of racehorses. Study objective was to determine effects of a 2-week intense exercise regimen on mRNA and protein expression of markers associated with venous remodeling in pulmonary veins harvested from 2 regions of horse lung. Thoracoscopically-guided wedge biopsies of caudodorsal and cranioventral lung tissue were retrieved from one lung. Horses were conditioned and then exercised on a high-speed treadmill over 2 weeks. The biopsy procedure was repeated. Pulmonary veins dissected from lung were analyzed for mRNA expression of matrix metalloproteinases (MMP-2, MMP-9), tissue inhibitors of matrix metalloproteinases (TIMP-1, TIMP-2), collagen, tenascin-C, endothelin-1, platelet derived growth factor, transforming growth factor beta (TGF-b) and vascular endothelial growth factor (VEGF). Protein expression of collagen, tenascin-C, TGF-b and VEGF was evaluated using morphometry and immunohistochemistry. EIPH incidence was 33.3% based on endoscopic observation. Exercise caused down-regulation of MMP-2, MMP-9, TIMP-2, TGF-b and VEGF mRNA expression, irrespective of location. Collagen content of tissue was greater in caudodorsal lung and unaffected by exercise. Exercise did not alter protein expression of tenascin-C, TGF-b and VEGF. A 2-week intense exercise regimen did not alter mRNA and protein expression of remodeling markers in a manner that favors venous remodeling. This work highlights the complexity of the remodeling process and suggests that more than two weeks of intense exercise may be required to induce remodeling.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Effects of exercise on markers of venous remodeling in lungs of horses.
Stack A, Derksen FJ, Sordillo LM, Williams KJ, Stick JA, Brandenberger C, Steibel JP, Robinson NE.
Am J Vet Res. 2013 Sep;74(9):1231-8. doi: 10.2460/ajvr.74.9.1231.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Distribution of venous remodeling in exercise-induced pulmonary hemorrhage of horses follows reported blood flow distribution in the equine lung.
Williams KJ, Robinson NE, Defeijter-Rupp H, Millerick-May M, Stack A, Hauptman J, Derksen FJ.
J Appl Physiol (1985). 2013 Apr;114(7):869-78. doi: 10.1152/japplphysiol.01170.2012. Epub 2013 Jan 31.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Reply to Pancheva, Panchev, and Pancheva.
Robinson NE, Williams KJ, Stack A, Derksen FJ, Hauptman J, Millerick-May M, DeFeijter-Rupp H.
J Appl Physiol (1985). 2013 Aug 1;115(3):413. doi: 10.1152/japplphysiol.00544.2013.
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: Eight unraced horses 6.4 2.3 (mean SEM) years of age were treated with intravenous heparin sodium (50,000 IU) and euthanized. Sections of CD and CV lung were collected and placed in chilled Ca2+- free HEPES-buffered PSS. Pulmonary arteries and veins 228.9 19.6 and 183.4 13.9 micro m diameters (mean SEM) respectively were microdissected under a stereomicroscope and mounted in a 4-chamber wire myograph (DMT 620M) for generation of length-tension curves. Data were fit to the exponential growth equation (y=y0ckx) and best-fit curves compared by ANOVA (P < 0.05). Following analysis, vessels were mounted in "Histogel" and sections stained with hematoxlyin-eosin and Verhoeff-Van Gieson to confirm their identity as artery or vein. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Rationale Exercise-induced pulmonary hemorrhage (EIPH) occurs in the majority of equine athletes. During exercise, horses experience mean pulmonary arterial and venous pressures in excess of 100 mmHg and 60 mmHg respectively. Pressure-mediated stress failure of pulmonary vessels is a likely cause of EIPH. EIPH pathology occurs primarily within the caudodorsal (CD), but not the cranioventral (CV) lung, following the known preferential distribution of blood flow to the CD region. Remodeling of small diameter pulmonary veins within the CD but not the CV lung is central to the pathogenesis of EIPH. Mechanical properties of small equine pulmonary vessels have not been reported. We hypothesize that there are no regional differences in the mechanical properties of pulmonary arteries and veins in normal, unraced, equine lung. Methods Eight unraced horses 6.4 2.3 (mean SEM) years of age were treated with intravenous heparin sodium (50,000 IU) and euthanized. Sections of CD and CV lung were collected and placed in chilled Ca2+- free HEPES-buffered PSS. Pulmonary arteries and veins 228.9 19.6 and 183.4 13.9 micro m diameters (mean SEM) respectively were microdissected under a stereomicroscope and mounted in a 4-chamber wire myograph (DMT 620M) for generation of length-tension curves. Data were fit to the exponential growth equation (y=y0ckx) and best-fit curves compared by ANOVA (P < 0.05). Following analysis, vessels were mounted in "Histogel" and sections stained with hematoxlyin-eosin and Verhoeff-Van Gieson to confirm their identity as artery or vein. Results 21 arteries (10 CV and 11 CD) and 21 veins (10 CV and 11 CD) were studied. Internal diameters of arteries and veins did not differ (P > 0.05). When all arteries were compared to all veins, veins were significantly stiffer than arteries (curves different P < 0.0001) (Fig. 1). Arteries from the CD region were stiffer than those from the CV region (P < 0.0001), whereas CV veins were stiffer than CD veins (P < 0.0001) (Fig 2). Conclusions Diverse mechanical properties of arteries and veins must be a reflection of vessel wall structure. Differences in vessel wall mechanics between CD and CV regions are likely an adaptation to the inhomogeneous distribution of blood flow in the equine lung. Considering the regional nature of EIPH pathology, these differences in vessel wall mechanics and structure may also be important in EIPH pathogenesis.
Publications
- No publications reported this period
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: This year's studies of veno-occlusive remodeling (VOR) in exercise induced pulmonary hemorrhage (EIPH) suggest that 1) VOR is the first lesion of EIPH to develop 2) VOR is most severe in the caudodorsal lung region 3) VOR can occur alone, and 4) Other EIPH lesions are always accompanied by VOR. Based on this information it is highly likely that VOR is the most important EIPH lesion, and is pivotal in EIPH pathogenesis The lungs from 9 EIPH-affected horses that had been retired from racing because of persistent severe bleeding were studied, and compared to 9 unraced controls. The lungs were inflation-fixed with formalin at 30 cm H2O, and sliced from caudal to cranial in sixteen 1.5 cm thick slabs. Examination of these slabs revealed grossly-evident pulmonary pathology that was much more severe than previously reported. An average of 6 histologic sections were harvested from each slab (192 sections per horse) by use of the smooth fractionator technique, a statistically rigorous approach to sampling. Histologic scores were assigned based upon the presence and severity of venous remodeling, hemosiderin accumulation, and interstitial, pleural and septal fibrosis. Control horses had no EIPH lesions. In EIPH-affected horses, remodeling of the intra-lobular veins sometimes occurred alone, indicating that this lesion likely develops first. The other lesions of EIPH including hemosiderosis, and interstitial fibrosis were always co-localized with venous remodeling. Histopathologic lesions were most extensive in the caudodorsal region, becoming less extensive in a cranioventral direction. Furthermore, a mean of up to 70 % of histologic sections in the caudodorsal regions had EIPH lesions, while in the cranioventral regions fewer than 20 % of sections had lesion. The gross pathology and histopathology data both demonstrate that EIPH lesions involve significant portions of the lungs, especially in the caudodorsal regions. Because venous remodeling may be found in the absence of the other EIPH lesions, but the other lesions are always co-localized with venous remodeling, the data presented here support the hypothesis that venous remodeling is the initiating lesion of EIPH, and that the other changes within the lung, as well as the bleeding, occur as a consequence of primary venous disease. Results of this study were reported at an international conference on EIPH in Lexington Kentucky. This important new information on EIPH is also disseminated to MSU veterinary scientists, veterinary students, and graduate students. A paper is being prepared for publication in the refereed literature. PARTICIPANTS: Dr. Alice Stack in now a Ph.D. student on this project TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
EIPH is a highly prevalent and performance-limiting disease of racehorses. Further, it is an aspect of racing that may be viewed negatively by the media and the race-going public. The pathogenesis of the disease is incompletely understood, and effective treatments do not exist. Results from our study suggest that VR contributes to the pathogenesis of EIPH as follows: Repeated bouts of high pulmonary venous pressure during strenuous exercise result in regional vein wall remodeling. The resultant decrease in vein compliance causes increased resistance to blood flow in these veins. The latter leads to regional increases in pulmonary capillary pressures that are sufficient to cause capillary wall failure and bleeding. This is followed by hemosiderin accumulation, and subsequently, fibrosis in the lung. This information will further understanding of the pathogenic mechanisms of the disease, and provide direction for future development of targeted therapeutic interventions in EIPH. The ability to prevent EIPH or mitigate the resulting lung damage through modification or prevention of venous remodeling would be of tremendous benefit to both horse welfare and the racehorse industry.
Publications
- Derksen F, Williams K, Stack A.(2011.Exercise-induced pulmonary hemorrhage in horses: the role of pulmonary veins. Compend Contin Educ Vet. 2011;33(4):E1-6.
- Williams KJ, Derksen FJ, Defeijter-Rupp HL, Robinson NE.Repeated blood instillation into the airway of the horse does not cause pulmonary fibrosis. Equine Vet J. 2011 May;43(3):354-358.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Regional veno-occlusive remodeling of pulmonary veins in exercise-induced pulmonary hemorrhage (EIPH)-affected horses, suggests that pulmonary veins may be central to the pathogenesis of EIPH. During the reporting period, we quantify site-specific changes in vein walls, collagen and hemosiderin accumulation, and pleural vascular profiles in the lungs of EIPH horses. In the caudodorsal lung regions of EIPH-affected horses, there is veno-occlusive remodeling with hemosiderosis, angiogenesis, and fibrosis of the interstitium, interlobular septa, and pleura. Tissues were collected, semi-quantitative histopathology was performed, and morphometric methods were used to analyze the distribution and accumulation of pulmonary collagen, and hemosiderin, and to count pleural vascular profiles in the lungs of 5 EIPH-affected and 2 control horses. Results of this study were reported at an international conference on EIPH in Salt Lake City Utah. This important new information on EIPH is also disseminated to MSU veterinary scientists, veterinary students, and graduate students. A paper was prepared for publication in the refereed literature. To further this work, we also collected lung tissues from an additional 10 EIPH- affected horses and 9 control horses. The goal of this study is to systematically describe, and map, the gross pathology and histologic lesions in the lungs of Thoroughbred racehorses with a history of EIPH relative to age-matched control horses.Thoroughbreds were identified by collaborating racetrack veterinarians and obtained by donation. Following euthanasia of the animals, the entire cardiopulmonary system was removed from the thoracic cavity and the lungs photographed. Both lungs were perfused via the lobar bronchi with 10 % formalin under a constant pressure of 30 cm of water for 24 hours. Subsequently, starting at the most caudal edge, lungs were cut in 1.5 cm thick slabs in the transverse plane. Using 1.5 cm thick transverse slabs, the entire lung (without the apical lobe) was sectioned into approximately 20 slabs. Using an annotation tool and computer software (Olympus FluoView software, OlympusAmerica, Center Valley PA.), the extent of the gross EIPH lesion was mapped in 3 dimensions by assembling images from the consecutive slices. Tissue samples for histologic, morphometric, and immunohistochemical studies were selected using the smooth fractionator technique. All of the slides were evaluated by a board certified veterinary pathologist without knowledge of sampling location, using brightfield microscopy, except for the Picrosirius Red-stained slides, which were evaluated using polarized light. Each of the slides was assigned a histopathologic score. With these data, we will systematically describe, and map, the distribution of VOR, and its relationship to the gross pathology and histologic lesions of EIPH Data analysis is currently ongoing. PARTICIPANTS: Collaborators on this project include Dr. N. E. Robinson and Dr. Kurt Williams. Dr. Robinson and Dr. Williams have provided physiology and pathology expertise respectively TARGET AUDIENCES: Target audience are veterinarians horse owners and trainers who deal with sport horses or racehorses. The information generated by this project has been disseminated by speaking at a national meeting and through publication in a refereed journal. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The prevailing hypothesis about EIPH pathogenesis is capillary stress failure in response pulmonary hypertension during exercise. The observations we made this year suggest that stress failure may be exacerbated by venous remodeling. Inward venous remodeling, and the resultant increased resistance downstream from the alveolar capillaries, will result in elevated pulmonary capillary pressures, especially during exercise. We suggest that the resultant bleeding leads to co-localization of hemosiderin, fibrosis, and angiogenesis.The co-localization of the venous remodeling, hemosiderin, fibrosis, and angiogenesis was apparent in lung regions sorted by histopathologic score (HS). In tissues with the highest score, most intra-lobular veins had excess collagen in the adventitia, often interposed between the elastic lamina and the lumen. Compared to normal regions, vein collagen concentration in the high score regions was increased by 48%, while the total collagen content more than doubled. Consequently, mean intra-lobular vein wall thickness in high score regions was 83% greater than in normal tissues. Interestingly, venous outer wall perimeter did not differ between groups, but compared to normal tissues, lumen perimeter was reduced by 33% in high score regions. This inward remodeling results in increased vascular resistance that leads to increased upstream pulmonary capillary and arterial pressure, and diverts blood flow to other regions. When we examined the distribution of lesions by region, the highest HS was in region 3, but HS in other dorsal regions, although lower, did not differ significantly from region 3. By contrast, HS in the two most ventral parts of the lung (regions 4 and 5) was significantly less than in region 3. Vein wall thickness and hemosiderin had the same regional distribution and were highly correlated giving further support to their co-localization and to the presence of veno-occlusion as the underlying cause of hemosiderosis. The strikingly smaller vein wall thickness and the lack of regional variability in the young, unraced control horses increases our confidence that regional changes in EIPH-affected horses are related to the disease and not to regional variability in normal Thoroughbred lungs. If venous hypertension causes venous wall thickening, why is the change restricted to the dorso-caudal region of the lung This might occur if caudodorsal veins experience a higher intraluminal pressure as a consequence of the preferential caudodorsal distribution of blood flow during exercise. Furthermore, even within an isogravimetric plane, pulmonary blood flow can vary considerably suggesting that, within the caudodorsal region, lesions of EIPH may well be focal. In summary, our data support the following hypothesis for the pathogenesis of EIPH. Repeated bouts of pulmonary venous hypertension during strenuous exercise result in regional vein wall remodeling. The resultant venous occlusion leads to capillary hypertension, capillary stress failure, bleeding, hemosiderin accumulation, and lung fibrosis.
Publications
- No publications reported this period
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Does repeated administration of autologous blood cause pulmonary fibrosis To answer this question, blood or saline were instilled in predetermined lung regions once, twice, 3 times, 4 times, and 5 times as follows: On day 1 of the study, blood or saline were instilled in the first principal and control lung regions respectively. Fourteen days later, blood or saline were instilled in the same principal and control regions, and also in a second principal and control region. This process was repeated at two-week intervals until the first regions received 5 instillations, the second regions 4, the third regions 3, the fourth regions 2, and the final regions 1 instillation. Two weeks after the last instillation, horses were euthanized using an overdose of pentobarbital. We found that the equine lung is capable of effectively clearing blood and that no fibrosis resulted. In some instances we found bronchiolitis obliterans, but this lesion is not characteristic of EIPH. There are many differences between naturally occurring exercise-induced pulmonary hemorrhage (EIPH) and instillation of autologous blood into airways. In EIPH, there are red blood cells in the pulmonary parenchyma as well as the airways. Furthermore, rupture of capillaries may elicit inflammation. Finally in EIPH, bleeding occurs over many years giving time for mechanisms involved in injury and repair to play out. For these reasons, it is clear that airway instillation of autologous blood is not a good model to study EIPH pathology. What is the spatial distribution of the EIPH lesion To answer this question we studied the lungs of10 horses with known EIPH as compared to 10 non-racing breed control horses. Lungs were formalin fixed at an airway opening pressure of 30 cm of water. Subsequently lungs were sliced in a caudal to cranial direction into 1.5-cm thick slabs. The slabs were photographed and the visible EIPH lesion was map by use of digital software. Next the slabs were sampled for histological evaluation by use of the smooth fractionation technique. Tissues were stained with H&E, picrosirius red, and trichrome stains and the lesions were scored. Currently we are in the process of analyzing these data. Results of these studies were reported at the World Equine Airway Symposium held in August, in Bern Switzerland. PARTICIPANTS: My collaborators on this project are Drs. Kurt Williams and Ed Robinson. Dr. Williams, a board-certified veterinary pathologist, is instrumental in the evaluation of EIPH tissues. Dr. Robinson contributes his vast knowledge of equine pulmonary diseases and physiology for this project. TARGET AUDIENCES: TARGET AUDIENCES: Target audience for this research includes veterinary scientists, graduates students, veterinary students, veterinary practitioners, and horse owners. New information generated by this research was disseminated to these groups through the World Equine Airway Symposium held in Bern, Switserland, graduate level and graduate-professional level teaching, and by numerous telephone contacts with practicing veterinarians. PROJECT MODIFICATIONS: PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Gross lesions of EIPH include bilaterally symmetrical dark discoloration of the pleura of the dorsocaudal lung, which is firmer than normal lung. In the older literature, the primary histologic findings were described as scattered bronchiolitis, hemosiderophage accumulation, fibrosis, and angiogenesis. Recently, we have identified a novel histological lesion, venoocclusive remodeling (VOR) of intralobular veins, as an important and characteristic lesion within the lungs of EIPH horses. Our data suggest that VOR has important implications regarding the pathogenesis of EIPH. Whereas VOR can occur alone and therefore is probably the earliest lesion of EIPH, VOR occurs most severely in the caudodorsal lung, and rarely occurs in the cranial and ventral lung fields. Furthermore, significant accumulation of pulmonary hemosiderin and lung fibrosis do not occur without co-incidental VOR. The mechanism responsible for VOR, and the reason for its caudodorsal distribution are unknown. Based upon our preliminary findings, we propose that VOR is the key lesion of EIPH. While at this time we do not know what causes this lesion, we propose the following sequence of events leading to EIPH. Regional VOR, especially within the caudodorsal lung fields, underlies the pathogenesis of EIPH as follows: High-intensity exercise results in high pulmonary vascular pressures. Because in exercising horses pulmonary blood flow is preferentially distributed to the caudodorsal regions, pulmonary vascular pressures are particularly high in these lung regions. Repeated bouts of high vascular pressure result in pulmonary vein wall remodeling, including fibrosis of the adventitial wall layer. This remodeling causes narrowing of the vein lumen and regional venous occlusion. During exercise, venous occlusion in turn results in regionally severe increases in pulmonary capillary pressure, capillary rupture, and bleeding. The resulting hemosiderin causes interstitial, septal, and pleural fibrosis. We further suggest that because of the preferential caudodorsal distribution of blood flow in exercising horses, vein wall remodeling occurs preferentially in the caudodorsal lung region. The identification of venoocclusive remodeling as the key lesion of EIPH is a major step forward in our understanding of the pathogenesis of the disease. This discovery focuses our attention on pulmonary venous hypertension during intense exercise, and will lead us, and other research groups, to investigate therapeutic methods that may be employed to reduce high vascular pressures in pulmonary veins. Interestingly, the type V phosphodiesterase inhibitor E4021 has been reported to significantly reduce EIPH in experimental treadmill and racetrack studies, suggesting that pulmonary venodilation during intense exercise may prove to be effective in the treatment for EIPH. Therapy such as this, if proven to be effective, could prevent the veno-occlusive remodeling that we hypothesize is the cause of EIPH.
Publications
- Derksen FJ, Williams KJ, Pannirselvam RR, de Feijter-Rupp H, Steel CM, Robinson NE. Regional distribution of collagen and haemosiderin in the lungs of horses with exercise-induced pulmonary haemorrhage. Equine Vet J. 2009 Jul;41(6):586-91.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Research results were disseminated by presentations at two international meetings. The first meeting held in St. Louis, Missouri involved approximately 200 veterinarians and 100 graduates students as well as representatives from industry. The practical implications of our research findings on exercise-induced pulmonary hemorrhage (EIPH) were discussed. At the second meeting, held in San Diego, California research results were presented to a small group (25) of investigators active in the field of EIPH research. During this 3-day workshop the scientific aspects of our findings were thoroughly discussed and put into context with other research on EIPH. The information presented at these meetings is captured in meeting proceedings. Furthermore, I have telephone consultations about EIPH with equine veterinarians from Michigan and other states on a weekly basis. During these conversations I emphasized the practical implications of our research finding for management practices, and prevention and treatment of EIPH. Finally, research findings on EIPH are incorporated in lectures to veterinary students, undergraduate students, and equine residence at Michigan State University. PARTICIPANTS: My collaborators on this project are Drs. Kurt Williams and Ed Robinson. Dr. Williams, a board-certified veterinary pathologist, is instrumental in the evaluation of EIPH tissues. Dr. Robinson contributes his vast knowledge of equine pulmonary diseases and physiology for this project. TARGET AUDIENCES: Target audience for this research includes veterinary scientists, graduates students, veterinary students, veterinary practitioners, and horse owners. New information generated by this research was disseminated to these groups through the Havemeyer workshop on EIPH held in San Diego, California, graduate level and graduate-professional level teaching, and by numerous telephone contacts with practicing veterinarians. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The pathogenesis of exercise-induced pulmonary hemorrhage (EIPH), and the cause of the caudodorsal distribution of the hemorrhage are poorly understood. This year we described the regional distribution and co-localization of pulmonary veno-occlusive remodeling with fibrosis, hemosiderin accumulation, and angiogenesis within the lungs of EIPH horses. In 7 horses with EIPH, 6 sections were collected from both the right and left lung, representing the cranial, middle, and caudal region of the dorsal and ventral lung. Histologic scores were assigned to each region, based upon the presence and severity of interstitial fibrosis, hemosiderin accumulation, pleural/interlobular septal thickness, arterial and venous wall thickness and evidence of angiogenesis. 46% of the sections were histologically normal, 39% were moderately affected, while 14%, primarily from the dorso-caudal lung, had severe lesions. In the latter, veno-occlusive remodeling of the intra-lobular veins was colocalized with hemosiderosis, fibrosis, hypertrophy of vessels within the pleura and interlobular septa, and bronchial neovascularization. We also utilized morphometric methods to analyze the distribution and accumulation of pulmonary collagen, hemosiderin, and pleural vasculature in the lungs of 5 of these EIPH horses and 2 control horses. The data were analyzed based upon lung region, as well as upon the severity of the histopathology. In EIPH affected horses, vein wall collagen thickness was greatest in the dorsocaudal lung, and significantly correlated with hemosiderin accumulation. When data were analyzed based on lesion severity, increased venous, interstitial, pleural, and septal collagen, lung hemosiderin and pleural vascular profiles occurred together, and were most common in the dorsocaudal lung. Further, hemosiderin accumulation co-localized with decreased pulmonary vein lumen size. When data from all regions were evaluated, vein wall thickening, hemosiderin accumulation, and histological score were highly correlated and these changes occurred only in the dorsal part of the lung. No regional differences in vein wall thickness or hemosiderin content were observed in the lungs of control horses. On average, vein wall thickness was less in these horses, and in caudodorsal regions, was half that in EIPH-affected animals. The data presented here suggest that regional pulmonary venous remodeling is central to the pathogenesis of EIPH. We propose the following hypothesis: exercise-induced venous hypertension, primarily within the caudodorsal lung, leads to venous remodeling and collagen accumulation. This leads to local increases in pulmonary capillary pressure, capillary stress failure, bleeding, hemosiderin accumulation, and subsequently fibrosis in the lung.
Publications
- Derksen F.J., (2008)Pulmonary Venous Remodeling in Equine Exercise Induced Pulmonary Hemorrhage. Page 12 in Proc. Havemeyer Foundation workshop on EIPH, San Diego CA.
- Williams KJ, Derksen FJ, de Feijter-Rupp H, Pannirselvam RR, Steel CM, Robinson NE.(2008)Regional pulmonary veno-occlusion: a newly identified lesion of equine exercise-induced pulmonary hemorrhage. Vet Pathol. 45(3):316-26.
- Derksen, F. J., Williams K. J., Pannirselvam, R.R., De Feijter-Rupp H., Steel, C. M.,Robinson, N. E.(2008)Regional Distribution of Collagen and Hemosiderin in the Lungs of Horses with Exercise-induced Pulmonary Hemorrhage, Equine Veterinary Journal (in press)
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Exercise-induced pulmonary hemorrhage (EIPH)is an important health problem of racehorses. The purpose of this investigation is to elucidate the pathobiology of this disease. Results of this project has been presented at a national meeting (American Association of equine practitioners December 2007) and published in the form of refereed journal articles.
PARTICIPANTS: Collaborators on this project include Dr. N. E. Robinson and Dr. Kurt Williams. Dr. Robinson and Dr. Williams have provided physiology and pathology expertise respectively
TARGET AUDIENCES: Target audience are veterinarians horse owners and trainers who deal with sport horses or racehorses. The information generated by this project has been disseminated by speaking at a national meeting and through publication in a refereed journal.
Impacts
The investigation started by evaluating if instillation of autologous blood into the airways of horses causes pulmonary fibrosis. This information is important because if true, therapeutic strategies can be developed to prevent this fibrosis. Our experiments conclusively demonstrated that autologous blood instillation into the airway of horses is not associated with fibrosis. This information has significantly changed our thinking about the pathogenesis of EIPH. Next we studied the pathology of naturally occurring EIPH. We gathered tissues from EIPH affected horses that had been deleted from racing in Singapore because of this condition. Extensive pathologic and morphometric studies were undertaken to describe the pathology of EIPH in detail. Novel findings of this study allowed for the generation of new hypotheses about EIPH pathogenesis.
Publications
- Derksen FJ, Williams KJ, Uhal BD, Slocombe RF, de Feijter-Rupp H, Eberhart S, Berney C, and Robinson NE.(2007). Pulmonary response to airway instillation of autologous blood in horses.Equine Vet J.39(4):334-339.
- Williams KJ, Derksen FJ, de Feijter-Rupp H, Pannirselvam R, Steel CM, and Robinson NE. (2008).Regional Pulmonary Veno-occlusion: A Newly Identified Lesion of Equine Exercise-Induced Pulmonary Hemorrhage Americal Journal of Veterinary Pathology. In press.
- Derksen FJ, Robinson NE, Pannirselvam R, DeFeijter-Rupp H, Steel CM, and Williams KJ. (2007) Venous occlusion accompanies bleeding, hemosiderosis and fibrosis in horses with exercise-induced pulmonary hemorrhage.In proceedings American Association of Equine Practitioners meeting, Orlando Florida (P65-67)
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