Platelet-derived growth factor(s) mitogenic activity in patients with myeloproliferative disease

Summary. Platelet-derived growth factor has been invoked in the pathogenesis of medullary fibrosis during myeloproliferative disorders. In this study we compared the mitogenic activity of heat-stable platelet-derived growth factor(s) from 13 patients suffering from myeloproliferative disorders with that of a normal group. The test was carried out on G0 growth arrested Balb/c 3T3 fibroblasts incubated with various concentrations of platelet extracts, determining the entrance into the S phase by means of [14C]thymidine uptake. The incorporation curves of [14C]thymidine by the fibroblast culture, under the effect of pathological extracts, were consistently lower than the control curve, indicating a lower level of PDGF(s) in platelets from patients. The greatest depression of this activity was found to be associated with highest degree of medullary fibrosis (agnogenic myeloid metaplasia patient group), in agreement with the hypothesis that fibroblast activation within bone marrow during myeloproliferative disorders might be correlated with a PDGF(s) release in the bone marrow environment.