RESUMO
BackgroundSmad4,a key intracellular mediator in transforming growth factor-β (TGF-β)signaling,plays a critical role in the normal development of many tissues/organs.However,its functional role in the development of lacrimal gland has rarely been reported.ObjectiveThe aim of this study was to investigate the role that Smad4 may play in the development of lacrimal glands using Smad4 conditional knockout (CKO) mice( C57BL/6 mouse line),MethodsSmad4 in lacrimal glands,as well as in the lens,cornea and ectoderm of the eyelids,was conditionally inactivated by the Pax6 promoter-driven Cre transgenic mice and Smad4 conditional gene mice,LacZ reporter was used to visualize the developing lacrimal gland by X-gal staining,and standard histological approaches were used to reveal morphological changes.Six or more mice or embryos in each group were used for comparisons at the same stage.ResultsLacZ staining showed that E15.0,Smad4 CKO mice could still develop primary lacrimal bud,but much shorter than the wild-type ones.At E16.5,the primary lacrimal bud in wild-type mice began branching,but no branching was found in Smad4 CKO mice except that the primary lacimal bud became blunt at the tip.At E18.0,although Smad4 CKO mice develop some acini,the branching and size and number of acini were obviously less than ones in Smad4 wild-type mice.Based on histological findings,lacrimal glands in Smad4 CKO mice developed slowly,and the size was considerably smaller,and the numbers of lobes as well as the numbers of acini were much fewer than those of Smad4 wild-type mice lacrimal glands at various stages.Pigment and adipose tissue were also observed within the lacrimal glands starting from P7 in Smad4 CKO mice and increased with age growing.Lacrimal glands in mutant adult mice were eventually replaced by adipose tissue and accumulation of pigments.Conclusions These results support the notion that Smad4 is essential for the normal development and maintenance of the mouse LG and may be involved in the metabolism of pigment and adipose tissue in LG.