Characterization and transfusion of in vitro cultivated hematopoietic progenitor cells

Our study is to show the safety of transfusion and the number, phenotype, and proliferative potential of in vitro cultivated autologous hematopoietic peripheral blood progenitor/stem cells (PBPCs). An in vitro long-term liquid culture using PBPC suspension from consenting patients with metastatic breast cancer was established. The medium was supplemented with a variety of hematopoietic growth factors. The mononuclear cells (MNCs), their viability, CD34+ subsets, clonogenic cells, and neutrophil function were measured prior to, during, and after liquid culture for 14 days. The total cell number increased during incubation in vitro from 2.5 × 10⁸ to 5 × 10⁹. The clonogenic and CD34+ cells increased during the first week 6- and 3.5-fold, respectively, and were almost undetectable after 2 weeks. Maturation into the myeloid cell series was demonstrated by standard cytology and increase of CD33+ and CD38+ cell numbers. On average, 1.5 × 10⁹ cells were transfused to consenting patients with metastatic breast cancer after high-dose chemotherapy and PBPC transplantation at nadir of WBC ≤0.1/nL. One hour later, the mean WBC was measurable at 0.3/nL. Subsequently, WBC counts dropped to 0.2/nL and 0.1/ nL at 6 and 24 h post transfusion. No side effects and complications were observed. In summary, an in vitro expansion can produce a ≥20-fold increase of maturing PBPCs for an effective and safe autologous transfusion. This unique approach, when refined, could lead to a safer post-transplant period and a decrease of complications due to neutropenic fever.