Cells capable of bone production engraft from whole bone marrow transplants in nonablated mice

Allogeneic and autologous marrow transplants are routinely used to correct a wide variety of diseases. In addition, autologous marrow transplants pote ntially provide opportune means of delivering genes in transfected, engraft ing stem cells. However, relatively little is known about the mechanisms of engraftment in transplant recipients, especially in the nonablated setting and with regard to cells not of hemopoietic origin. In particular, this in cludes stromal cells and progenitors of the osteoblastic lineage. We have d emonstrated for the first time that a whole bone marrow transplant contains cells that engraft and become competent osteoblasts capable of producing b one matrix. This was done at the individual cell level in situ, with signif icant numbers of donor cells being detected by fluorescence in situ hybridi zation in whole femoral sections. Engrafted cells were functionally active as osteoblasts producing bone before being encapsulated within the bone lac unae and terminally differentiating into osteocytes. Transplanted cells wer e also detected as flattened bone lining cells on the periosteal bone surfa ce.