Transforming growth factor-alpha (TGF-alpha) mRNA is expressed in several pancreatic cancer cell lines, but its expression during normal fetal pancreas development has not been studied. We investigated the expression of TGF-alpha, its receptor (EGF-R) and insulin mRNA and their corresponding peptides in human fetal pancreata (15–20 gestation weeks). Polymerase chain reaction (PCR) and RNAase protection analysis revealed that TGF-alpha and insulin mRNAs were detectable in pancreas during the developmental span studied. In northern blot analysis a single band of 4.8 kilobases (kb) corresponding to the TGF-alpha transcript and a 0.6 kb for the insulin mRNA were detected in the pancreas. Using in situ hybridization, TGF-alpha mRNA expression was seen in a low copy number in both the exo- and endocrine pancreas. By immunohistochemistry TGF-alpha-immunoreactive cells were detected in the ducts, acini and islets showing that the mRNA was translated into protein. By contrast, insulin transcripts were detected in a high copy number, restricted to the islets of Langerhans. However, monoclonal insulin antibody detected less insulin containing cells than could be expected from the mRNA pattern suggesting that fetal beta-cells rapidly secrete insulin instead of storing it in the secretory granules. Alternatively, the translation of insulin mRNA could be inefficient. By double labeling the pancreas sections with polyclonal TGF-alpha antiserum and monoclonal insulin antibody the TGF-alpha- and insulin-like immunoreactivity was localized to beta-cells. Furthermore, mRNA for the TGF-alpha receptor, EGF-R, together with EGF-R-immunoreactive cells were also present in pancreas.(ABSTRACT TRUNCATED AT 250 WORDS)
Testicular sertoli cells protect islet beta-cells from autoimmune destruction in NOD mice by a transforming growth factor-beta1-dependent mechanism
