Fetal hemopoiesis in diffusion chamber cultures. I. The pattern of pluripotent stem cell growth.

The growth pattern of fetal liver (FL), normal adult bone marrow (NABM) and regenerating (post Velban treatment) adult bone marrow (RABM) colony forming units (CFU) cultured in diffusion chambers (DC) was studied. When twenty CFU were implanted into DC the recovery of CFU after 4 days with FL, NABM or RABM was 133 +/- 7, 19 +/- 2 and 34 +/- 2 CFU, respectively. The transplantation fraction of CFU from NABM decreased from 10-4% on day 0 to 6-9% on day 4; that of FL did not change from the initial 6-2%. The growth rate of CFU derived from FL was substantially greater than that from NABM. The relative growth of FL and RABM CFU was clearly inhibited when the concentration of cells cultured was increased. Spleen colonies from FL cells before culture were larger (P less than 0-005) than colonies from NABM but after 7 days of culture there was no difference between the two groups. Histological examination of spleen colonies showed that after DC culture FL and NABM CFU were differentiating along the three normal pathways. These data suggest that intrinsic differences exist between fetal and adult stem cells in the in vivo diffusion chamber culture system.