Effects of human fibroblasts from myelometaplasic and non-myelometaplasic hematopoietic tissues on CD34+ stem cells

Fibroblasts demonstrate different phenotypes and functions according to the tissue of origin and its physiopathologic state. We previously showed that fibroblasts isolated in culture from myelometaplasic (MM) spleen differed phenotypically from fibroblasts from normal bone marrow (BM). We compared the influence of each type of fibroblasts on the behavior of CD34+ stem cells. Expansion of nucleated cells was observed when blood CD34+ cells were co-cultured for 3 weeks with MM spleen-derived fibroblasts in monolayers. Myeloid cell differentiation was also observed as indicated by a decline in CD34+ cells and increases in CD14+, CD15+ and CD41+ cells. This myeloid differentiation was enhanced in the presence of MM spleen compared with normal BM-derived fibroblasts. Similarly, proliferation and differentiation of BM CD34+ cells was better in the presence of BM rather than MM spleen-derived fibroblasts. In addition, fibroblasts from MM spleen also induced a differentiation of CD56+ natural killer (NK) cells whereas BM-derived fibroblasts did not. Overall, the data indicate that cultured fibroblasts from diseased tissue have distinct growth and differentiation regulatory characteristics. They also suggest a role for these cells in hematopoietic disorders.