Beneficial reciprocal effects of bone marrow stromal cells and Schwann cells from adult rats in a dynamic co-culture system in vitro without intercellular contact

In order to examine how implanted bone marrow stromal cells (BMSCs) encourage peripheral nerve regeneration, the present study investigated the interaction of BMSCs and Schwann cells (SCs) using an indirect in vitro co-culture model. SCs and BMSCs were obtained from adult Sprague-Dawley rats. The passaged BMSCs were CD29- and CD44-positive but CD45-negative and were co-cultured with the primary SCs using a Millicell system, which allows BMSCs and SCs to grow in the same culture medium but without direct contact. Expression of the typical SC markers S-100 and glial fibrillary acidic protein (GFAP) of the treated BMSCs as well as the proliferation capacity of the co-cultured SCs was evaluated by immunocytochemical staining on the 3rd and 5th day of co-culture. Immunocytochemical staining showed that >75% of the BMSCs in the indirect co-culture model were GFAP- and S-100-positive on the 3rd and 5th day after co-culture, as opposed to <5% of the BMSCs in the control group. On the 3rd day after co-culture, only a few co-cultured BMSCs showed the typical SC-like morphology, while most BMSCs still kept their native appearance. By contrast, on the 5th day after co-culture, almost all of the co-cultured BMSCs appeared with the typical SC-like morphology. Furthermore, 70.71% of the SCs in the indirect co-culture model were S-100-positive on the 5th day of co-culture, as opposed to >30.43% of the SCs in the control group. These results indicated that BMSCs may interact synergistically with SCs with regard to promoting peripheral nerve regeneration.