Selectively increased growth of fetal hemoglobin-expressing adult erythroid progenitors after brief treatment of early progenitors with transforming growth factor beta.

We have studied the effect of transforming growth factor beta (TGFbeta) on erythropoiesis in cultures from adult peripheral blood, using flow cytometric enumeration of fetal hemoglobin (HbF)-containing cells. TGFbeta caused a dramatic increase in the proportions of cells that accumulated HbF together with adult hemoglobin (HbA) (F+A+ cells). This highly significant (P <.0001) increase in F+ cell proportion was achieved by TGFbeta treatment during the first 4 days of culture and was sustained during further culture expansion in the absence of TGFbeta. The increase in F+ cell proportions did not depend on the cytokine combination (EPO+SCF+IL3, EPO+SCF, EPO+IL3, SCF+IL3) used during the phase of TGFbeta treatment. Increased F+ cell proportions were paralleled by an increased molecular ratio of HbF/ HbF+ HbA, measured by cation exchange high-performance liquid chromatography (HPLC). In addition to the effect on F+ cell proportions, TGFbeta caused a dramatic increase in overall cell division potential. By the time cultures reached terminal growth arrest (12-14 days in controls and 18-26 days after TGFbeta), the overall numbers of F+ cells produced per initially seeded clonogenic cell was approximately 10 times higher in the TGFbeta-treated cultures than in the controls. We propose to investigate whether the TGFbeta-induced increase in relative and absolute numbers of nucleated F+ cells, as demonstrated in vitro, can be translated into increased F+ erythrocytes in vivo, allowing therapeutic application for some beta-hemoglobinopathies. (Blood. 2000;95:2967-2974)