Expressions of Angiopoietin-1, Angiopoietin-2, and Tie2 and their roles in rat renal allografts with chronic allograft nephropathy

Objective

Angiopoietin-1 (Ang1) and −2(Ang2) are 2 ligands for the endothelium-specific tyrosine kinase Tie2. Previous studies have shown that reciprocal regulation of Ang1, Ang2, and Tie2 plays an important role in chronic cardiac allograft vasculopathy. This study investigated the expressions of Ang1, Ang2, and Tie2 in rat renal allografts undergoing chronic allograft nephropathy (CAN).

Materials and Methods

Renal transplantations following the procedure of Kamada with our modification were orthotopically performed using Fisher (F344, RT1^1v1) rats as both donors and recipients in the autograft group. Fisher and Lewis (LEW, RT1¹) rats were used as donors and recipients in the allograft group, respectively, which was treated with cyclosporine (CsA; 10 mg/kg/d × 10 d). At 4w, 8w, and 12 weeks posttransplantation, serum creatinine (SCr) was measured and pathologic changes assessed according to the Banff 97 criteria. The mRNA (Δct) and protein expressions of Ang1, Ang2, and Tie2 were localized by real-time fluorescence quantitative polymerase chain reaction (PCR) and by immunohistochemistry.

Results

The elevation in SCr and the pathologic changes in CAN were observed in all allografts at 8 and 12 weeks. The expressions of Ang1 and Ang2 were localized to epithelial cells and endothelium of the vascular bundles of the glomeruli; Tie2 was specifically expressed in endothelium of vessels both in auto- and allografts at all time points posttransplantation. At 4 weeks, the differences in mRNA expression of Ang1, Ang2, and Tie2 between the 2 groups were not significant (P > .05). Compared with autografts, the mRNA expression of Ang1 decreased significantly (P = .008 and .003 for 8 and 12 weeks, respectively), and the mRNA expressions of Ang2 and Tie2 significantly increased (P = .001/.006 and .005/.001 for 8 and 12 weeks, respectively). The changes in expression of all 3 genes showed significant correlation with the Banff score in the allografts.

Conclusion

This study suggested that the abnormal expression and reciprocal regulation of Ang1, Ang2, and Tie2 may play important roles in the development of CAN in rat renal allografts.