Recipient Organization
UNIVERSITY OF ILLINOIS
2001 S. Lincoln Ave.
URBANA,IL 61801
Performing Department
Veterinary Research & Extension
Non Technical Summary
A large number of strategies have been developed to accelerate bone repair in people and veterinary patients. These approaches include autologous bone grafting (currently considered to be the gold standard), allo- and xeno-graft materials, ceramic scaffolds, and more recently, biologic therapies such as recombinant bone morphogenetic proteins (BMP) and platelet-rich plasma. All of these agents carry strengths and liabilities, associated with access/availability, bio-compatibility and costs. Over the past four decades, demineralized bone matrix (DBM) has been established as a clinically useful material for bone repair. Because the inorganic mineralized component of bone is removed during processing, DBM has little or no load-bearing capacity. However, it has both osteo-conductive (provides a substrate for bone deposition) and osteoinductive (stimulates bone formation) properties. DBM's osteo-inductivity is derived from BMPs and other growth factors that are retained in the collagenous matrix and released after implantation. Further, DBM grafts can be trimmed and shaped to fit irregular osseous defects or can be manufactured in a granular or powdered formulation and impacted into defects. This versatility has made DBM a valuable graft material in human orthopaedics and DMB is also commercially available (through Veterinary Transplant Services Inc.), for veterinary applications.Several groups have documented the highly variable degree of osteo-inductivity of human DBM preparations. Donor age affects this activity, but differences in DBM processing, both within and between facilities, are also critical. Experimental studies have demonstrated that supplementing DBM with recombinant BMP-2 protein significantly increases osteogenesis at implantation sites. However, recombinant BMP-2 is prohibitively expensive for most veterinary applications (several thousand dollars per 'single use' package) and excessive heterotopic bone formation is now a recognized complication of recombinant protein use, as a consequence of the rapid release of supraphysiological levels of BMP at the implantation site.To mitigate the cost issue and to avoid the potential for excessive heterotopic bone formation, we propose to use BMP-2 expression constructs to augment the osteo-inductive activity of DBM grafts. Expression plasmids are far less expensive to produce than recombinant proteins, are stable for prolonged periods of time, and have demonstrated efficacy in experimental orthopaedic repair contexts. Because generation of BMP-2 requires host cell uptake and local expression, the risks of excessive, transient release of active protein is very low.
Animal Health Component
70%
Research Effort Categories
Basic
30%
Applied
70%
Developmental
(N/A)
Goals / Objectives
The aim of this project is to determine whether loading DBM matrices with a BMP-2 expression construct will improve the rate of cortical bone healing in a caprine unicortical defect model.
Project Methods
Demineralized bone matrix scaffolds (provided by Veterinary Transplant Services) will be loaded with eqBMP-2 expression vectors or LacZ control vectors and implanted in 6-mm circular defects created in the lateral cortices of the fused metacarpal bones.Repair of the cortical bone defects will be assessed at 4 and 8 weeks, using microCT imaging and quantitative analyses of bone volume in the defects, as a function of total volume. The defects and surrounding bone will then be processed for histomorphometry and the tissue infill and characteristics of the cortical bone defects will be measured at both time points.