Different thymosin Beta 4 immunoreactivity in foetal and adult gastrointestinal tract.

Background: Thymosin beta 4 (Tb4) is a member of beta-thymosins, a family of peptides that play essential roles in many cellular functions. A recent study from our group suggested a role for Tb4 in the development of human salivary glands. The aim of this study was to analyze the expression of Tb4 in the human gut during development, and in the adult. Methodology/Principal Findings: Immunolocalization of Tb4 was studied in autoptic samples of tongue, oesophagus, stomach, ileum, colon, liver and pancreas obtained from two human foetuses and two adults. Tb4 appeared unevenly distributed, with marked differences between foetuses and adults. In the stomach, superficial epithelium was positive in foetuses and negative in adults. Ileal enterocytes were strongly positive in the adult and weakly positive in the foetuses. An increase in reactivity for Tb4 was observed in superficial colon epithelium of adults as compared with the foetuses. Striking differences were found between foetal and adult liver: the former showed a very low reactivity for Tb4 while in the adult we observed a strong reactivity in the vast majority of the hepatocytes. A peculiar pattern was found in the pancreas, with the strongest reactivity observed in foetal and adult islet cells. Significance: Our data show a strong expression of Tb4 in the human gut and in endocrine pancreas during development. The observed differential expression of Tb4 suggests specific roles of the peptide in the gut of foetuses and adults. The observed heterogeneity of Tb4 expression in the foetal life, ranging from a very rare detection in liver cells up to a diffuse reactivity in endocrine pancreas, should be taken into account when the role of Tb4 in the development of human embryo is assessed. Future studies are needed to shed light on the link between Tb4 and organogenesis.