Electron microscopy of human fetal erythroid cells before and after cryopreservation

Fetal erythropoiesis was studied in human livers at 10 to 12 weeks of gestation. The most primitive blood cells were often observed in large indentations of the surface of hepatocytes and the plasma membranes of the two cell types were adherent at sites of attachment. Erythroid cell maturation occurred predominantly in the lumen of the sinusoids. Cell suspensions obtained from fetal livers were centrifuged, frozen at -196 degrees C, thawed and studied by electron microscopy. The primitive cells were morphologically altered by these procedures. Changes included damage to mitochondria and cell membranes and vacuole formation. Erythroblasts, by comparison, were virtually intact and even displayed some indications of reestablished functions within 10 minutes after thawing.