Origin of stromal cells associated with osteoclast recruitment in s.c. implants of bone particles in chimeric mice

Subcutaneous implantation of devitalized bone particles (BPs) in mice elicits a fibrovascular response with subsequent differentiation of multinucleated osteoclast-like cells. In bone marrow, stromal cells are known to play important roles in controlling hematopoiesis. Similarly, the stromal cells in the initial reaction to BPs may take part in supporting subsequent osteoclast recruitment and differentiation within the implants. Cross-gender chimeric mice were used to allow determination of whether these stromal cells were derived from local tissue or from hematopoietic stem cells. In radiation-chimeric mice, there was a 7-day delay in stromal recruitment and osteoclastic differentiation. Therefore cultures were established from the stromal tissue elicited 11 days after implantation, prior to osteoclastogenesis. Analysis of Y-chromatin DNA from these lines demonstrated that the majority (97%) of the lines were of recipient origin. It is possible that these fibroblast-like cells migrate to the site of BP implantation and play a role in the initiation of osteoclast development. This model can be used to define cellular interactions in osteoclastogenesis.