Ischemia-reperfusion injury (IRI) in renal transplant recipients is a risk factor of allograft dysfunction and reduced survival. Although tubular epithelial cells (TEC) are classically considered the main cellular target of IRI, mounting evidence identifies microvascular injury as an important contributor. Caspase-3 (Casp3) activation, a read-out of apoptotic cell death, has been reported in TEC and endothelial cells after acute kidney injury (AKI). The functional and relative importance of Casp3 activation in tubular and microvascular demise post-IRI remains ill defined.

Unilateral renal artery clamping for 30 min with contra-lateral nephrectomy was performed in WT(C57Bl/6) or Casp3 KO mice. Mice were sacrificed and serum, urine, kidneys were collected at days 1, 2, 3, 7 or 21days post-IRI. Blood urea nitrogen (BUN), renal histopathology (kidney injury score), immunohistochemical staining for CD34, Sirius red and α-smooth muscle actin (α-SMA) were analyzed. Serum levels of connective tissue growth factor(CTGF) and urine levels of cystatin C were determined by ELISA.

Casp3 KO mice showed higher BUN levels at 1 day (p<0.05), higher levels of urine cystatin C at 1 day and higher tubular injury scores at 1, 2, 7 days (p<0.05) post-IRI compared with WT. Microvascular congestion however was reduced in Casp3 KO mice at 2 days post-IRI (p<0.05) and this was associated with higher numbers of CD34 positive peritubular capillaries at 1, 2 and 7 days post-surgery in Casp3 KO mice, suggesting reduced microvascular involution. Casp-3 KO mice also showed lower serum levels of CTGF at 2 days, reduced expression of the pro-fibrotic marker α-SMA within peritubular capillaries at 3 days and less collagen deposition at 21 days post-IRI (p<0.05), indicating an important role for caspase-3 in IRI induced fibrosis.

Collectively these observations suggest that Casp3 deficiency protects the renal microvasculature and reduces fibrosis but accentuates tubular epithelial injury post-IRI. These results also demonstrate a predominant role for microvascular over epithelial injury in controlling the development of fibrosis following renal IRI.

CITATION INFORMATION: Yang B, Lan S, Patey N, Turgeon J, Dieudé M, Hébert M.-J. Dual Role for Caspase-3 in the Regulation of Tubular and Microvascular Damage Post-Renal Ischemia-Reperfusion Injury. Am J Transplant. 2017;17 (suppl 3).

« Back to 2017 American Transplant Congress