Hematopoiesis on cellulose ester membranes (CEM): III. Long-term histologic changes between 6 and 12 months after...

Cellulose ester membranes (CEM) of pore size 0.45 mu were enriched on their inner surfaces with spleen or bone marrow or bone or regenerating primitive endosteal tissue folded into a tubular configuration and implanted i.p. Although CEM with enrichment with bone or marrow or spleen supported trilineal hematopoiesis 3 to 6 months after i.p. implantation, CEM at 8 and 9 months were progressively fibrotic and involuted with minimal hematopoietic support capacity. CEM of pore size 3 mu were enriched with bone marrow or bone or regenerating endosteal tissue. These CEM after 9 and 12 months supported excellent trilineal hematopoiesis and were always associated with osteogenesis. Regenerating primitive endosteal tissue is an equally effective source of stroma to regenerate the hematopoietic microenvironment. Unenriched CEM became progressively more fibrotic after 6 months.