Comparison of cell cycle kinetics and regulators between CD34⁺ progenitors cultured on FN- versus BSA-coated plates. Human bone marrow CD34⁺ progenitors were cultured in the presence of IL-3, IL-6, and SCF for 48 hours on either FN- or BSA-coated plates prior to analysis. (A) Ki67/7-AAD staining was performed to identify the percentage of G₀, G₁, and S/G₂M cells after 48 hours on FN- (□) and BSA- (▪) coated plates. (B) Subcellular fractionations were performed on 10⁶ cells recovered from FN- and BSA-coated plates and immunoblotted with an antibody against p21Cip1 and p27Kip1. Freshly isolated CD34⁺ progenitors and mononuclear cells were subfractionated and immunoblotted with an antibody against p21Cip1 (left) and compared with cells harvested after 48-hour culture on FN- versus BSA-coated plates (right). Total protein lysates were immunoblotted to assess for p57Kip2 (lower left). MNC indicates mononuclear cells. Error bars indicate standard deviation.