Role of epithelial-mesenchymal transition in repair of the lacrimal gland after experimentally induced injury.
OBJECTIVE
Ongoing studies demonstrate that the murine lacrimal gland is capable of repair after experimentally induced injury. It was recently reported that repair of the lacrimal gland involved the mobilization of mesenchymal stem cells (MSCs). These cells expressed the type VI intermediate filament protein nestin whose expression was upregulated during the repair phase. The aim of the present study was to investigate the roles of vimentin, a type III intermediate filament protein and a marker of epithelial-mesenchymal transition (EMT) in repair of the lacrimal gland.


METHODS
Injury was induced by direct injection of interleukin (IL)-1 into the exorbital lacrimal gland. MSCs were prepared from injured glands using tissue explants. Expression of vimentin and the transcription factor Snai1, a master regulator of EMT, was determined by RT-PCR, Western blotting analysis, and immunofluorescence.


RESULTS
These data show that vimentin expression, at both the mRNA and the protein levels, was upregulated during the repair phase (2-3 days postinjury) and returned to the control level when repair ended. Temporal expression of Snai1 mirrored that of vimentin and was localized in cell nuclei. Cultured MSCs isolated from injured lacrimal glands expressed Snai1 and vimentin alongside nestin and alpha smooth muscle actin (another biomarker of EMT). There was a strong positive correlation between Snai1 expression and vimentin expression.


CONCLUSIONS
It was found that EMT is induced during repair of the lacrimal gland to generate MSCs to initiate repair, and that mesenchymal-epithelial transition is then activated to form acinar and ductal epithelial cells.
Department of General Dentistry, Tufts University School of Dental Medicine, Boston, Massachusetts 02111, USA.
Samantha
S
You
Orna
O
Avidan
Ayesha
A
Tariq
Ivy
I
Ahluwalia
Paul C
PC
Stark
Claire L
CL
Kublin
Driss
D
Zoukhri
D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D002469:Cell Separation; D002478:Cells, Cultured; D004195:Disease Models, Animal; D058750:Epithelial-Mesenchymal Transition / Q000502:physiology*; D005131:Eye Injuries / Q000378:metabolism / Q000503:physiopathology*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000502:physiology; D007381:Intermediate Filament Proteins / Q000235:genetics / Q000378:metabolism; D007765:Lacrimal Apparatus / Q000293:injuries*; D059630:Mesenchymal Stem Cells; D051379:Mice; D008807:Mice, Inbred BALB C; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D064231:Nestin; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000378:metabolism; D014746:Vimentin / Q000235:genetics / Q000378:metabolism; D014945:Wound Healing / Q000502:physiology*
C558396:Acta2 protein, mouse; D000199:Actins; D015415:Biomarkers; D007381:Intermediate Filament Proteins; D009419:Nerve Tissue Proteins; C577485:Nes protein, mouse; D064231:Nestin; D012333:RNA, Messenger; C000604429:Snai1 protein, mouse; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D014746:Vimentin