Basic fibroblast growth factor corrects proliferative derangement of bone marrow stroma and CD34+ population following allogeneic stem cell transplantation

Objectives Following stem cell transplantation (SCT), the integrity of the hematopoietic microenvironment is important for the recovery of bone marrow. We studied the effects of basic fibroblast growth factor (bFGF) on the proliferation of clonogenic progenitors and bone marrow stroma from patients receiving cytokine-mobilized allogeneic stem cell transplants (SCT). Materials and Methods Patient bone marrow mononuclear cells were studied at a minimum of 6 months after transplantation. Control and patient samples were divided into two fractions, one to establish the adherent stroma layers (SL) and the other to select for the progenitor population. SL from normal subjects or from patients were supplemented with 0 (control), 2, or 20 ng/mL bFGF in combination with heparan sulfate, and the resulting area of the dish covered by stroma was quantitated in each group. At 3 weeks of culture, a monocellular suspension was prepared by exposing SL to 0.1% trypsin. Cells then were cultured in the colony-forming unit fibroblast (CFU-F) assay, which was supplemented with 0 (control), 2, or 20 ng/mL bFGF. With the second fraction, CD34+ cells were selected with paramagnetic beads, and 1 × 104 cells were incubated in cross-culture studies on preformed SL from patient or control origin (with or without the addition of bFGF). SL adherent CD34+ cells were covered with agar and cultured for 6 days. Aggregates of >20 cells were scored as blastic colonies (CFU-bl). Results At 3 weeks of culture, the median surface area of dishes covered by monoloayers from 13 patients was 40% (range 10–50% vs normal 55%, range 30–60%; p = 0.00006) and improved significantly, matching control values, in dishes supplemented with bFGF. Addition of bFGF to stroma monolayers had no effect on the number of CFU-F in both patient and control samples. Selected CD34+ cells from patients receiving transplants and cultured on normal stroma gave significantly fewer CFU-bl than control samples (median 36, range 3–121 vs 147, range 10–184; p = 0.006), but colony numbers corrected following exposure to bFGF. Normal CD34+ cells proliferated poorly on stroma from patients (median CFU-bl 37.5, range 6–84; p = 0.02), but also expanded significantly following bFGF supplementation (104, range 6–117; p = 0.001). Conclusions Following SCT, poor SL and CD34+ proliferation can be corrected by addition of bFGF.