Читать книгу Genetic Disorders and the Fetus - Группа авторов - Страница 119

The distinctiveness of the AFC types received support in a series of ultrastructural and cell secretion studies.^{566, 568–572} Hormones such as hCG, estrogen and progesterone are produced by AF‐type cells, some of which must originate from (placental) trophoblast tissue.^{572, 573} In contrast, F‐type AFCs failed to show hormone production, which is consistent with their likely mesenchymal origin.^{571, 574, 575} Human CVS cultures show higher levels of hCG secretion than AF‐type AFC cultures.⁵⁷⁶ Both AF‐ and F‐type AFCs express human lymphocyte antigen (HLA) class I (HLA‐ABC) but not class II (HLA‐DR) surface antigens.⁵⁷⁷

Extracellular matrix (ECM) studies and other work^{63, 578–580} defined a number of qualitative differences between AF‐ and F‐type AFCs. The differences in the types of procollagens produced were such that Bryant et al.⁵⁸¹ could use these as markers in fusion studies involving AFCs and postnatally derived skin fibroblasts. Johnston et al.⁵⁸² provided additional evidence for the distinctiveness of the AF cell type (Figure 3.6). Several polypeptide spots were qualitatively different among F and AF clones (see arrows in Figure 3.6). It furthermore provides convincing evidence for a close ontogenetic relationship between E and AF cells, since their two‐dimensional polypeptide patterns are nearly identical (see Figure 3.6).

Figure 3.6 Selected landscapes from two‐dimensional ³⁵S‐methionine‐labeled polypeptide maps of F‐, AF‐, and E‐type total cell homogenates. All three clone types are derived from a single amniotic fluid specimen to exclude genotypic differences as a source of the apparent protein map differences. Horizontal dimension: isoelectric focusing; vertical dimension: polyacrylamide gradient gel electrophoresis. For technical details, see Johnston et al.⁵⁸² Arrowheads mark consistent differences of polypeptide spot patterns in the vicinity of the easily identifiable actin cluster (A).