Skeletal muscle and bone marrow derived stromal cells: a comparison of tenocyte differentiation capabilities.

This study investigated the comparative ability of bone marrow and skeletal muscle derived stromal cells (BMSCs and SMSCs) to express a tenocyte phenotype, and whether this expression could be augmented by growth and differentiation factor-5 (GDF-5). Tissue harvest was performed on the hind limbs of seven dogs. Stromal cells were isolated via serial expansion in culture. After four passages, tenogenesis was induced using either ascorbic acid alone or in conjunction with GDF-5. CD44, tenomodulin, collagen I, and collagen III expression levels were compared for each culture condition at 7 and 14 days following induction. Immunohistochemistry (IHC) was performed to evaluate cell morphology and production of tenomodulin and collagen I. SMSCs and BMSCs were successfully isolated in culture. Following tenocytic induction, SMSCs demonstrated an increased mean relative expression of tenomodulin, collagen I, and collagen III at 14 days. BMSCs only showed increased mean relative expression of collagen I, and collagen III at 14 days. IHC revealed positive staining for tenomodulin and collagen I at 14 days for both cell types. The morphology of skeletal muscle derived stromal cells at 14 days had an organized appearance in contrast to the haphazard arrangement of the bone marrow derived cells. GDF-5 did not affect gene expression, cell staining, or cell morphology significantly. Stromal cells from either bone marrow or skeletal muscle can be induced to increase expression of matrix genes; however, based on expression of tenomodulin and cell culture morphology SMSCs may be a more ideal candidate for tenocytic differentiation.