Abstract
Purpose: :
Ongoing studies from our laboratory demonstrate that murine lacrimal gland is capable of repair following experimentally induced injury. We recently reported that repair of the lacrimal gland involved the mobilization of mesenchymal stem cells (MSCs). These cells expressed the type VI intermediate filament (IF) protein nestin whose expression was up regulated during the repair phase. The aim of the present study was to investigate the roles of vimentin, a type III IF protein, and epithelial-mesenchymal transition (EMT) in repair of the lacrimal gland.
Methods: :
Injury was induced experimentally by direct injection of interleukin-1 (IL-1) into the exorbital lacrimal gland. MSCs were derived from tissue explants, cultured in complete DMEM with 10% fetal bovine serum, and were used in passages 3-4. Vimentin expression was determined by RT-PCR, western blotting and immunofluorescence. The expression of E-cadherin (a marker of epithelial phenotype), snail and twist (2 transcription factors known to repress E-cadherin expression and are marker of EMT) was also determined.
Results: :
Our data show that, similar to nestin, vimentin expression was upregulated during the repair phase (2-3 days post injury) and returned to control level when repair ended. MSCs isolated from injured lacrimal glands and propagated in vitro expressed vimentin alongside nestin and alpha smooth muscle actin. E-cadherin expression was lost in cultured MSCs while expression of snail and twist was upregulated suggestive of induction of EMT.
Conclusions: :
We concluded from these studies that, similar to nestin, vimentin protein is upregulated during lacrimal gland repair after experimentally induced inflammation. We hypothesize that re-expression of nestin and vimentin and inhibition of E-cadherin expression in MSCs is necessary for their migration to repair the injured lacrimal gland.
Keywords: lacrimal gland • cornea: tears/tear film/dry eye • regeneration