New type of matrix support for bone marrow cell cultures: In vitro cultureand in vivo transplantation experiments

A new type of bone marrow cell culture system was developed by using a high ly porous substrate matrix, i.e., porous polyvinyl formal (PVF) resin. Muri ne bone marrow (BM) cells were cultured without the use of exogenous growth factors in a three-dimensional matrix support made of collagen coated poro us PVF resin. To examine the optimal conditions for highest stromal cell de nsity, short-term and long-term in vitro culture experiments using PVF were performed. In the shortterm culture experiments, it was found that cubes o f PVF (10 x 10 x 2 mm and 130 mu m in pore size) coated with type I collage n with a seeding density of 2 x 10(7) BM cells offered the most appropriate culture conditions. In the long-term cultures, BM cells in PVF maintained their viability for up to 6 weeks. In another series of re-inoculation expe riments, freshly isolated BM cells were inoculated onto the already develop ed stromal layer. In this study, a higher cell density of the stromal layer was obtained in the PVF culture compared with those in the control dish cu lture. Based upon the results of in vitro experiments, in vivo transplantat ion studies were also performed. Histologic examinations of the subcutaneou sly transplanted PVF with stroma revealed host derived hematopoiesis inside the PVF matrix. Moreover, survival of approximately 15% of the transplante d BM cells that were cultured in PVF were confirmed in X-ray irradiated rec ipients. From these results, it is suggested that PVF resin is a promising three-dimensional substrate for BM cell culture and that it can maintain he matopoietic stem cells or progenitor cells after transplantation.