Expression of laminin and collagen genes by cells cultured from developing human sciatic nerves

The expression of laminin alpha1, alpha2, beta1, beta2 and gamma1 subunits and proalpha1(I), proalpha1(III), alpha1(IV), alpha1(VI), alpha2(VI) and alpha3(VI) collagen chains was studied by Northern hybridizations, RNase protection assays and indirect immunofluorescence (IIF) labellings in cell cultures initiated from sciatic nerves of 14-27-wk-old human fetuses. The cultures represented mixed populations of Schwann cells, perineurial cells and fibroblasts, as estimated by morphology and S 100 protein immunolabellings. The mRNAs for certain basement membrane (BM) components, laminin beta1 and gamma1 chains and collagen alpha1(IV) chain, were readily detectable by Northern analyses in all cultures. In contrast, laminin alpha1, alpha2 and beta2 chain mRNAs were expressed at markedly lower levels. The expression of laminin alpha1 chain was detectable only by RNase protection assay. RNase protection analysis also demonstrated that the expression of laminin alpha2 chain increased with the developmental stage of the nerve used as the source for cell cultures. The expression of laminin beta2 chain was detected only at the protein level by IIF which demonstrated a faint immunosignal in a small subpopulation of cells. The mRNAs for type I, III and VI collagens were readily detectable in the cultures by Northern hybridizations. In summary, the extracellular matrix genes expressed in fetal human peripheral nerves and corresponding cell cultures display marked similarities. Cell cultures characterized here may prove useful in analyses elucidating potential roles of selected growth factors and cytokines in the induction of e.g. laminin alpha1 and beta2 chain expression by cells of developing peripheral nerves.