TGFbeta Cross-linked to Microcarriers as Injectable IVD Therapy in Dogs and Humans

IntroductionStudies designed to use large canine models and translate the results to human practice must take into account the ex vivo and in vitro differences in the bone marrow derived stem cells(MSCs) and their response to a covalently bound growth factor. MethodsWe analyze the activity of transforming growth factor-β1 (TGF-β1) covalently immobilized on microcarriers either by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) or riboflavin/UV (RB/UV) light-mediated cross-linking. Collagen microcarriers cross-linked with TGF-β1 were used for chondrogenic differentiation of human or canine mesenchymal stem cells. Evaluation methods included cell viability test, chondrogenic marker expression (aggrecan and collagen type I and type II), histological detection of proteoglycans, and immunohistochemical analysis. ResultsCross-linking strengthened the collagen structure of the microcarriers and reduced collagenase-mediated degradation. Chondrogenic differentiation of MSCs was induced by TGF-β1 cross-linked on microcarriers, promoting gene expression and protein accumulation of aggrecan and collagen type I and type II, as well as proteoglycans. Cross-linking by RB/UV enhanced chondrogenesis more than any other group. In addition, cross-linking reduced scaffold shrinkage exerted by MSCs during chondrogenesis, a desirable feature for microcarriers if used as tissue defect filler. ConclusionCross-linking of TGF-β1 to collagen microcarriers supported chondrogenesis. Current veterinary clinical trial will show if such approach will lead a step closer to development of a cost-effective and locally acting device for cell-based therapy.