Myofibroblast proliferation, fibrosis, and defective pancreatic repair induced by cyclosporin in rats.
BACKGROUND
Full recovery is always achieved after caerulein induced pancreatitis. Cyclosporin stimulates transforming growth factor beta (TGF-beta) and may interfere with pancreatic regeneration.


OBJECTIVE
To investigate the effects of cyclosporin after caerulein induced pancreatitis or after caerulein injury.


METHODS
Protocol A: rats received cyclosporin daily (20 mg/kg) and caerulein pancreatitis was induced on days 2 and 8. Protocol B: six courses of caerulein pancreatitis were induced at weekly intervals. Cyclosporin was administered on induction and the day before. Rats recovered for two weeks before being killed. Control groups received saline, cyclosporin, or caerulein alone.


RESULTS
Protocol A: plasma TGF-beta1 and tissue collagenase rose after pancreatitis but decreased towards baseline values on day 15, matching a low collagen content. Morphology disclosed minimal inflammatory infiltration and some interstitial cells immunoreactive for smooth muscle alpha-actin (SMA). TGF-beta1 increased, and remained high in cyclosporin treated groups (cyclosporin alone and cyclosporin plus caerulein). Rats treated with cyclosporin and caerulein showed severe pancreatic weight reduction, abundant inflammatory infiltrates, increased SMA immunoreactive interstitial cells, high collagen content, and delayed collagenase response. No SMA immunoreactive cells were detected in normal rats. Cyclosporin alone also increased SMA immunoreactive cells, despite the absence of inflammatory infiltration and fairly conserved pancreatic structure. Protocol B: the combined pulse treatment induced appreciable collagen deposition and resulted in a smaller pancreas than controls. Morphological examination showed atrophy, fibrosis, fibroblast proliferation, and mononuclear infiltrates.


CONCLUSIONS
Cyclosporin greatly distorts pancreatic repair, transforming caerulein induced pancreatitis into a fibrotic chronic-like disease. The mechanism involves TGF-beta, myofibroblasts, and defective collagenase activation.
Vaquero
E
E
Digestive System Research Unit, Hospital General Universitari Vall d'Hebron, Barcelona, Spain.
Molero
X
X
Tian
X
X
Salas
A
A
Malagelada
J R
JR
D000199:Actins / Q000378:metabolism; D000208:Acute Disease; D000818:Animals; D002455:Cell Division; D002108:Ceruletide; D017364:Collagenases / Q000378:metabolism; D016572:Cyclosporine / Q000009:adverse effects*; D005355:Fibrosis / Q000139:chemically induced; D005765:Gastrointestinal Agents; D006909:Hydroxyproline / Q000378:metabolism; D007166:Immunosuppressive Agents / Q000009:adverse effects*; D008297:Male; D010179:Pancreas / Q000187:drug effects / Q000502:physiology*; D010195:Pancreatitis / Q000139:chemically induced / Q000473:pathology / Q000628:therapy*; D051381:Rats; D017208:Rats, Wistar; D012038:Regeneration / Q000187:drug effects*; D016212:Transforming Growth Factor beta / Q000097:blood
D000199:Actins; D005765:Gastrointestinal Agents; D007166:Immunosuppressive Agents; D016212:Transforming Growth Factor beta; D016572:Cyclosporine; D002108:Ceruletide; D017364:Collagenases; D006909:Hydroxyproline