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Updated: Sep 23, 2026
Modeling Hypoxia/Reoxygenation Injury in Proximal Tubular Epithelial Cells
Published on: November 21, 2025
Activation of mitochondrial apoptotic pathways in human renal allografts after ischemiareperfusion injury
M Patricia Castaneda1, Agnieszka Swiatecka-Urban, Mark M Mitsnefes
1Division of Nephrology, Children's Hospital at Montefiore, Bronx, New York, USA.
Background:
Ischemia-reperfusion injury in cadaveric (CAD) kidney allografts is associated with tubular cell injury, delayed graft function, and an increased incidence of acute and chronic rejection. We tested the hypothesis that activation of specific apoptotic pathways represents a mechanism for tubular cell death after CAD kidney transplantation.
Methods:
Serial tissue sections from paraffin-embedded needle biopsy specimens obtained at approximately 1 hr of reperfusion after transplantation of 13 CAD and 12 living-related donor (LRD) renal allografts were examined by using the terminal deoxynucleotide transferase-mediated dUTP nick-end labeling assay to detect apoptosis and by immunohistochemistry for expression of key pro-apoptotic molecules (Bax, Bak, tumor necrosis factor receptor [TNFR]-1, Fas, and cytochrome c).
Results:
Apoptosis was detected primarily in tubular cells, with a mean+/-standard deviation of 6.8+/-2.2 apoptotic cells per 100 cells examined in CAD renal allografts compared with 1.8+/-2.7 cells per 100 in LRD (P<0.001) renal allografts. There was a significant correlation between apoptosis rate and cold ischemia time in CAD (r=0.86, P<0.001) renal allografts. Bax was expressed in 100% of CAD versus 17% of LRD renal allografts (P<0.001), Bak in 92% of CAD versus 17% of LRD renal allografts (P<0.001), and TNFR-1 in 100% of CAD versus 58% of LRD renal allografts (P<0.05). Fas was expressed in only a small number of samples (23% of CAD and 17% of LRD renal allografts, P=not significant). Bax and Bak were expressed predominantly in apoptotic cells. Cytochrome c was detected as a mitochondrial pattern in LRD renal allografts, but in a diffuse cytosolic distribution in CAD renal allografts.
Conclusions:
Ischemia-reperfusion injury in CAD kidney transplants is associated with a duration-dependent increase in tubular cell apoptosis, mediated at least in part by activation of mitochondrial pathways.
Insights
Kidney transplants from deceased donors show increased tubular cell apoptosis, linked to longer cold ischemia times. This apoptosis is driven by the activation of mitochondrial pathways, contributing to organ injury.
Area of Science:
- Nephrology
- Transplantation immunology
- Cellular pathology
Background:
- Ischemia-reperfusion injury (IRI) in cadaveric (CAD) kidney allografts leads to tubular cell damage, delayed graft function, and heightened rejection risk.
- Specific apoptotic pathways are investigated as a mechanism for tubular cell death following CAD kidney transplantation.
Purpose of the Study:
- To test the hypothesis that specific apoptotic pathways are activated in tubular cells after CAD kidney transplantation.
- To compare apoptosis rates and pro-apoptotic molecule expression between CAD and living-related donor (LRD) kidney allografts.
Main Methods:
- Terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) assay to detect apoptosis in kidney biopsy sections.
- Immunohistochemistry to assess the expression of pro-apoptotic molecules: Bax, Bak, tumor necrosis factor receptor (TNFR)-1, Fas, and cytochrome c.
- Analysis of biopsy specimens from 13 CAD and 12 LRD renal allografts obtained approximately 1 hour post-reperfusion.
Main Results:
- Apoptosis was significantly higher in tubular cells of CAD allografts (6.8%) compared to LRD allografts (1.8%).
- Apoptosis rate in CAD allografts correlated significantly with cold ischemia time (r=0.86, P<0.001).
- Increased expression of Bax, Bak, and TNFR-1 was observed in CAD allografts compared to LRD allografts, with Bax and Bak predominantly in apoptotic cells. Cytochrome c shifted from mitochondrial to cytosolic distribution in CAD grafts.
Conclusions:
- Ischemia-reperfusion injury in CAD kidney transplants involves a duration-dependent increase in tubular cell apoptosis.
- The mitochondrial pathway plays a significant role in mediating this apoptosis in CAD kidney transplants.
