Direct isolation and expansion of human CD34+ hematopoietic stem cells.

The isolation and expansion of CD34+ cells has numerous applications as supportive therapy for cytopenias that occur postchemotherapy. In this report, we describe a simple system to directly isolate and culture human CD34+ cells. Using this system, CD34+ cells isolated from bone marrow were cultured in the presence of GM-CSF, G-CSF, erythropoietin, stem cell factor, IL-1, IL-3, and IL-6. Cell expansions up to 100-fold were noted during the first 2 weeks of culture with high maintenance of CD34+ cells during the first week of culture. Maximal expansions of progenitors were observed at one week of culture, with, on average, 20-fold increases in CFU-GM number. The results support the feasibility of CD34+ cell expansion for clinical application.