A critical role of serum response factor in myofibroblast differentiation during experimental oesophageal ulcer healing in rats.
BACKGROUND
Myofibroblast differentiation is a key event during wound healing and is triggered primarily by transforming growth factor beta (TGFbeta). Serum response factor (SRF) is a TGFbeta-inducible transcription factor that is important for wound healing. Injection of SRF expression plasmid into rat gastric ulcers significantly accelerated restoration of epithelium and smooth muscle structures.


OBJECTIVE
To determine the role of SRF in oesophageal ulcer healing, especially in myofibroblast differentiation.


METHODS
Rats (in vivo), oesophageal epithelial cells (Het1A) and fibroblasts (Rat1-R12) (in vitro) were used.


METHODS
Oesophageal ulcers were induced in rats with acetic acid and subsequently treated by local injection of plasmids expressing either SRF or SRF antisense sequence. Rats were killed at 1, 3, 6, 9 and 14 days after treatment and tissues collected. For in vitro studies, both Het1A and Rat1-R12 cells were transfected with the plasmids used in ulcer treatment.


RESULTS
Upregulation of SRF increased the myofibroblast population in ulcer granulation tissue; knockdown of SRF suppressed this event. In addition, ulceration induced SRF and TGFbeta expression coordinately. In vitro studies showed that overexpression of SRF in either oesophageal epithelial cells or fibroblasts was sufficient to induce myofibroblast phenotype. Furthermore, the TGFbeta-induced myofibroblast phenotype required integrin-linked kinase (ILK)-mediated SRF activation, as either knockdown of SRF or inactivation of ILK prevented this action.


CONCLUSIONS
SRF is indispensable for myofibroblast differentiation during oesophageal ulcer healing and is required for TGFbeta-induced myofibroblast transition from either epithelial cells or fibroblasts. ILK is a mediator in TGFbeta-induced SRF activation and subsequent myofibroblast differentiation. ILK is associated with SRF, and TGFbeta enhances this association.
Chai
Jianyuan
J
Department of Research (151), VA Long Beach Healthcare System, 5901 E 7th St, Long Beach, CA 90822, USA. jianyuan.chai@med.va.gov
Norng
Manith
M
Tarnawski
Andrzej S
AS
Chow
Justine
J
D019342:Acetic Acid; D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D004935:Esophageal Diseases / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D015316:Genetic Therapy / Q000379:methods*; D008297:Male; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000494:pharmacology; D026362:Serum Response Factor / Q000235:genetics / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology; D014456:Ulcer / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D014945:Wound Healing; D000099200:Scaffold Protein ILK
D019342:Acetic Acid; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins; D026362:Serum Response Factor; D016212:Transforming Growth Factor beta; D000099200:Scaffold Protein ILK