Comparison of equine tendon-, muscle-, and bone marrow-derived cells cultured on tendon matrix

Objective - To compare viability and biosynthetic capacities of cells isolated from equine tendon, muscle, and bone marrow grown on autogenous tendon matrix. Sample Population - Cells from 4 young adult horses. Procedures - Cells were isolated, expanded, and cultured on autogenous cell-free tendon matrix for 7 days. Samples were analyzed for cell viability, proteoglycan synthesis, collagen synthesis, and mRNA expression of collagen type I, collagen type III, and cartilage oligomeric matrix protein (COMP). Results - Tendon- and muscle-derived cells required less time to reach confluence (approx 2 weeks) than did bone marrow-derived cells (approx 3 to 4 weeks); there were fewer bone marrow-derived cells at confluence than the other 2 cell types. More tendon- and muscle-derived cells were attached to matrices after 7 days than were bone marrow-derived cells. Collagen and proteoglycan synthesis by tendon- and muscle-derived cells was significantly greater than synthesis by bone marrow-derived cells. On a per-cell basis, tendon-derived cells had more collagen synthesis, although this was not significant. Collagen type I mRNA expression was similar among groups. Tendon-derived cells expressed the highest amounts of collagen type III and COMP mRNAs, although the difference for COMP was not significant. Conclusions and Clinical Relevance - Tendon- and muscle-derived cells yielded greater cell culture numbers in shorter time and, on a per-cell basis, had comparable biosynthetic assays to bone marrow-derived cells. More in vitro experiments with higher numbers may determine whether tendon-derived cells are a useful resource for tendon healing.