RESUMEN
The effects of low temperature preservation on morphology, viability and differentiation capacity of different human fetal organs were studied using transmission (TEM) and scanning (SEM) electron microscopy, in vitro cultivation as well as xenogeneic transplantation. For this purpose fragments of lung, kidney, small intestine, thyroid, brain, liver and spleen from 10 human fetuses (aged 9 to 14 weeks of gestation) were frozen by a three step cooling procedure. After 3 to 12 months the specimens were thawed rapidly and processed for TEM and/or in vitro cultivation and/or transplantation into nude mice. TEM studies on frozen lung, kidney and intestine revealed generally a well preserved ultrastructure whereas liver and spleen fragments appeared highly necrotic. From three fetuses, frozen intestine and lung specimens were used for the establishment of monolayer cultures. Following trypsinization, both epithelial and mesenchymal cells formed a continuous layer on the bottom of plastic bottles. During further subpassages the number of epithelial cells decreased resulting in the formation of pure fibroblast cultures. Frozen brain tissue from one fetus was also successfully cultivated forming cell clusters and fiber bundles of variable size at the surface of glass cover slips. Following subcutaneous implantation into nude mice, the vast majority of fragments from lung, kidney, intestine and thyroid was found to grow in the recipients. The growth of xenografts was accompanied by persistence (kidney, intestine) or even increase (lung, thyroid) in cellular differentiation studied by TEM or autoradiography. Transplanted liver and spleen fragments, however, regularly regressed forming solid scars in the subcutaneous tissue of nude mice.(ABSTRACT TRUNCATED AT 250 WORDS)