Studies of the hemopoietic microenvironment. IV. In vivo microscopic and histochemical study of allografts of bone marrow in the hamster cheek pouch chamber.

Within a transparent chamber enclosing subcutaneous tissue of the hamster cheek pouch, allogeneic femoral marrow was grafted. This permitted in vivo microscopic study of the grafts for 14 days. Five to seven days after grafting, blood flow was established within sinusoids arranged in interconnecting polygonal networks, a pattern characteristic of marrow. All vessels appeared to have a complete and continuous endothelial lining. The graft contained foci of erythropoiesis, granulopoiesis, and megakaryocytopoiesis, but no osteogenic activity. Degeneration of the grafts began to occur between days 9 and 13 after implantation. Generally, this was preceded by infection within the chamber, fibroblastic proliferation, and an accumulation of acid mucopolysaccharide in the stroma. The concomitant loss of hemopoiesis and accumulation of acid mucopolysaccharides was consistent with our hypothesis reported previously that excessive concentrations of acid mucopolysaccharide in the hemopoietic microenvironment are not conducive to supporting hemopoiesis, especially erythropoiesis. Degeneration of the grafts probably was the result of infection since there was no evidence of an immunologic response to the graft, and in chambers not containing grafts, similar infections and changes in the connective tissue were observed. The technique of grafting marrow into the hamster cheek pouch chamber provides a model for long-term, in vivo microscopic study of bone marrow. However, methodologic improvements, especially in the control of infections, are needed.