Marrow microenvironment transfer by heterotopic transplantation of freshly isolated and cultured cells in porous sponges.

Cells for study were obtained from mouse bone marrow by three methods: 1) Mechanical dissociation; 2) Trypsin release; and 3) Passage through a syringe and needle. The ratio of the fibroblast colony-forming cells in these suspensions was, respectively, 1:13:1. Of the colonies formed by cells obtained by trypsin release, 70% were alkaline phosphatase positive fibroblasts. Freshly isolated marrow cells and cells harvested, by trypsin treatment, from cultures established from the differently obtained bone marrow cell suspensions, were absorbed into porous sponges for transplantation under the renal capsule of mice. Ossicles containing bone marrow formed after transplantation of either freshly isolated cells, or cultured cells obtained from marrow by trypsin treatment, but not after the transplantation of cells cultured from marrow obtained by mechanical dissociation. The size of the bone marrow "organs" that formed was determined by both the number of cells grafted and the size of the sponge in which they had been absorbed for grafting.