Keratinocytes inhibit expression of connective tissue growth factor in fibroblasts in vitro by an interleukin-1alpha-dependent mechanism.
The wound healing process concludes with downregulation of fibroblast activity. Clinical observations suggest that the regenerating epidermis suppresses this activity. An important regulator of fibroblast activity is the fibrogenic cytokine connective tissue growth factor. We hypothesized that epidermal keratinocytes may affect fibroblast activity via this cytokine. We demonstrate keratinocyte-mediated suppression of connective tissue growth factor at both the mRNA and protein levels by around 50% or more when fibroblasts were cultured in multiwell plates with keratinocyte cultures in accompanying semipermeable cell culture inserts, or stimulated by keratinocyte-conditioned media. Both basal and transforming-growth-factor-beta1-stimulated levels of connective tissue growth factor were inhibited. A 3 h coculture period with keratinocytes was sufficient to suppress connective tissue growth factor expression by fibroblasts, but the inhibition developed over a time period of around 16 h. The putative keratinocyte-derived factor(s) responsible for these effects was found to be soluble and stable. By analyzing cytokines secreted by keratinocytes we identified interleukin-1alpha as a potent inhibitor of connective tissue growth factor mRNA expression in fibroblasts. Involvement of this cytokine in keratinocyte-mediated connective tissue growth factor suppression was confirmed by using anti-interleukin-1alpha antibodies. Tumor necrosis factor alpha or prostaglandins did not appear to be involved. In conclusion, our results indicate that interleukin-1alpha secretion by keratinocytes provides a mechanism for the downregulation of connective tissue activity during the end-stage of wound healing, when epithelia coverage has developed over the wound area.
Department of Surgical Sciences, Plastic Surgery Unit, and Department of Medical Biochemistry and Microbiology, Uppsala University, Sweden.
Daniel
D
Nowinski
Patrik
P
Höijer
Thomas
T
Engstrand
Kristofer
K
Rubin
Bengt
B
Gerdin
Mikael
M
Ivarsson
D018920:Coculture Techniques; D055513:Connective Tissue Growth Factor; D005347:Fibroblasts / Q000378:metabolism; D006133:Growth Substances / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D017874:Immediate-Early Proteins / Q000096:biosynthesis / Q000235:genetics*; D007213:Indomethacin / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins; D007375:Interleukin-1 / Q000502:physiology*; D015603:Keratinocytes / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis
C526317:CCN2 protein, human; D006133:Growth Substances; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D007375:Interleukin-1; D012333:RNA, Messenger; D055513:Connective Tissue Growth Factor; D007213:Indomethacin