Effects of growth factors on aspirin-induced inhibition of wound repair in a rabbit gastric epithelial cell model

Insulin-like growth factor I improves aspects of mycophenolate mofetil-impaired anastomotic healing in an experimental model

Background

Patients taking immunosuppressants after transplantation may require intestinal surgery. Mycophenolate mofetil (MMF) has been found to impair the healing of colonic anastomoses in rats. This study examined whether insulin-like growth factor (IGF) I prevents MMF impairment of anastomotic healing.

Methods

Sixty-three rats were divided into three groups (MMF, MMF/IGF and control). Animals underwent a sigmoid colon anastomosis with a 6/0 suture, and were killed on days 2, 4 and 6 after surgery. Investigations included bursting pressure measurement, morphometric analysis, and assessment of mucosal proliferation by 5-bromo-2′-deoxyuridine and Ki67 immunohistochemistry of the anastomoses.

Results

The leak rate was three of 21, one of 20 and two of 20 in the MMF, MMF/IGF-I and control groups respectively. Anastomotic bursting pressures were significantly lower in the MMF group than in the control group on days 2 and 4, but there was no significant difference by day 6. Values in the MMF/IGF-I and control groups were similar. Colonic crypt depth was significantly reduced in MMF-treated animals on days 2 and 4, but this impairment was attenuated by IGF-I on day 4. Similarly, IGF-I reduced the negative impact of MMF on mucosal proliferation on days 2 and 6.

Conclusion

Exogenous IGF-I improves some aspects of MMF-impaired anastomotic healing.

Inhibition of proliferation of gastric epithelial cells by a cyclooxygenase 2 inhibitor, JTE522, is also mediated by a PGE2-independent pathway

BACKGROUND

Cyclooxygenase-2 (COX-2) is one of the rate-limiting enzymes for prostaglandin synthesis from arachidonic acid. Although it is known that inhibition of cyclooxygenase activity delays ulcer healing, the regulatory relationship between COX-2 and its metabolites in gastric epithelial cell proliferation is not well known.

AIM

To investigate whether COX-2 has an effect on gastric mucosal cell proliferation and further studied whether such effect is mediated only by prostaglandin E2 (PGE2), a representative metabolite of arachidonates in the gastric mucosa.

METHODS

Artificial wounds of defined area size were created on complete monolayer cell sheets of isolated rat gastric epithelial cells and rat gastric cell line RGM1 under the addition of arachidonic acid or a COX-2 selective inhibitor, JTE522. Repair of wounds was assessed by monitoring wound size, with cell proliferation detected using 5-bromodeoxyuridine staining. Quantity of secreted PGE2 was measured by enzyme immunoassay.

RESULTS

Stimulation of foetal calf serum increased the expression of COX-2 protein and inhibition of COX-2 retarded wound healing with reduction of cell proliferation. Arachidonic acid increased PGE2 production and accelerated restoration. Combination of JTE522 and arachidonic acid resulted in a marked retardation of wound healing compared to the control, but JTE522 did not completely suppress the increase in cellular PGE2 content following the addition of arachidonate.

CONCLUSIONS

The difference in the effects of JTE522 on PGE2 production and on wound healing suggest that the involvement of COX-2 in gastric epithelial cell proliferation is not mediated solely by PGE2.