Role of p38 MAP kinase in regulation of cell migration and proliferation in healing corneal epithelium.
OBJECTIVE
The purpose of the present study was to examine the roles of signaling pathways potentially activated by TGFbeta (i.e., Smad and p38 mitogen-activated kinase [MAPK]) in regulation of cell migration and proliferation of healing mouse corneal epithelium.


METHODS
Activation of Smads or p38MAPK was evaluated by immunohistochemistry in healing mouse corneal epithelium after debridement. The role of endogenous TGFbeta or p38MAPK in epithelial healing was determined in organ-cultured mouse corneas with an epithelial defect, in the presence or absence of a TGFbeta-neutralizing antibody or p38MAPK inhibitors, respectively. Cell proliferation was evaluated by incorporation of bromodeoxyuridine.


RESULTS
Migrating mouse corneal epithelium had minimal cell proliferation. Smad3 and -4 were found in nuclei of normal corneal epithelium, whereas they were absent in nuclei of migrating cells in association with Smad7 upregulation on epithelial debridement. Administration of TGFbeta-neutralizing antibody reduced the protein expression of Smad7 in vivo after a corneal injury. In contrast, phosphorylation and nuclear translocation of p38MAPK were markedly evident in migrating epithelium during healing, but not in uninjured epithelium. In organ culture, addition of p38MAPK inhibitors blocked cell migration more markedly than neutralizing TGFbeta-antibody and enhanced cell proliferation in the injured corneal epithelium, in association with phosphorylation of Erk.


CONCLUSIONS
Endogenous TGFbeta enhances migration of corneal epithelium during wound healing in mice. The p38MAPK, but not the Smad, cascade plays a major role in promoting cell migration and in suppressing cell proliferation in migrating epithelium.
Saika
Shizuya
S
Department of Ophthalmology, Wakayama Medical University, Wakayama, Japan. shizuya@wakayama-med.ac.jp
Okada
Yuka
Y
Miyamoto
Takeshi
T
Yamanaka
Osamu
O
Ohnishi
Yoshitaka
Y
Ooshima
Akira
A
Liu
Chia-Yang
CY
Weng
Daniel
D
Kao
Winston W-Y
WW
D000818:Animals; D002455:Cell Division / Q000502:physiology; D002465:Cell Movement / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019573:Epithelium, Corneal / Q000166:cytology* / Q000201:enzymology; D007124:Immunoenzyme Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D009924:Organ Culture Techniques; D010766:Phosphorylation; D015398:Signal Transduction / Q000502:physiology; D051785:Smad Proteins; D015534:Trans-Activators / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000502:physiology; D014945:Wound Healing / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D051785:Smad Proteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases