Involvement of S100A4 in stromal fibroblasts of the regenerating cornea.
OBJECTIVE
S100A4 is a member of the S100 family of calcium-binding proteins. Members of the S100 family have been implicated in a variety of cellular events, including growth, signaling, differentiation, and motility. It has been suggested that S100A4 modulates cell shape and motility by interacting with components of the cytoskeleton. In the present study, the distribution patterns of S100A4 were investigated in normal and regenerating mouse corneas.


METHODS
Rabbit cDNA libraries were prepared from cultures of corneal fibroblasts. S100A4 was identified as the most abundant message present. Expression of S100A4 in the cornea was determined using Northern blot analysis, in situ hybridization, and immunohistochemistry. Distribution patterns of S100A4 in primary corneal fibroblast cultures treated with either FGF-2/heparin or TGFbeta1 were analyzed by immunofluorescence.


RESULTS
S100A4 mRNA was rarely detected in keratocytes or epithelial cells of the normal rabbit cornea. Likewise, S100A4 antigen was not found in normal mouse corneas. However, after removal of the corneal epithelium, fibroblasts are activated and had readily detectable S100A4 expression 6 days after wounding. In the in vitro equivalent of activated keratocytes, cultured rabbit corneal fibroblasts, S100A4 was restricted to the cytoplasm. In contrast, in cultures treated with TGFbeta1, which induces a myofibroblast phenotype, more than 90% of the cells showed a nuclear localization of S100A4.


CONCLUSIONS
The findings show that S100A4 is expressed in the keratocyte phenotypes that appear in stromal tissue of corneas recovering from damage, the fibroblasts, and myofibroblasts. Its expression and distinct subcellular redistribution patterns suggest that S100A4 may be involved in the interconversions that occur between keratocytes, fibroblasts, and myofibroblasts during corneal wound healing.
D000818:Animals; D015152:Blotting, Northern; D002478:Cells, Cultured; D003319:Corneal Stroma / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D006493:Heparin / Q000494:pharmacology; D007124:Immunoenzyme Techniques; D017403:In Situ Hybridization; D008856:Microscopy, Fluorescence; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D012038:Regeneration; D009418:S100 Proteins / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D053773:Transforming Growth Factor beta1; D014945:Wound Healing / Q000502:physiology*
D012333:RNA, Messenger; D009418:S100 Proteins; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D016222:Fibroblast Growth Factor 2; D006493:Heparin