Arnaud Lyon1,2; Thomas Agius2; Sènan D’Almeida3; Kevin Kiesworo2; Sophie De Seigneux4; Thomas Verissimo4; Sébastien Déglise2; Florent Allagnat2; Michael MacArthur5, Sarah J. Mitchell5, Alejandro Ocampo6, Alban Longchamp2#; Déla Golshayan1#
1Transplantation Centre, Lausanne University Hospital and UNIL, Lausanne Switzerland.
2Division of Vascular Surgery, Lausanne University Hospital and UNIL, Lausanne, Switzerland.
3Flow Cytometry Core Facility, EPFL, Lausanne, Switzerland.
4Division of Nephrology, Geneva University Hospitals, Geneva, Switzerland.
5Department of Health Sciences and Technology, ETH, Zurich, Switzerland.
6Department of Biomedical Sciences, UNIL, Lausanne, Switzerland.
# Contributed equally
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Background. Substantial ischemia-reperfusion injury (IRI) occurs in 30% to 50% of kidney transplantations from deceased donor organs. During ischemia, damaged epithelial and endothelial cells secrete danger signals which activate local innate immune cells and recruit circulating immune cells which accumulate in the circulation at the time of reperfusion. This inflammatory process increases the risk of delayed graft function and can promote acute rejection and the evolution towards chronic allograft dysfunction. Previous experimental and clinical studies have highlighted sex-specific susceptibility to IRI in multiple organs. While sex hormones seem to be important, their precise effects on the immune regulation in the context of IRI still need to be investigated.
Methods. IRI was modelled in mouse kidneys using unilateral nephrectomy, followed by 23min ischemia and reperfusion of the controlateral kidney. Post-operative kidney function was evaluated over time by transcutaneous assessment of FITC-Sinistrin clearance. Histology, immunohistochemistry and Spatial total mRNA sequencing was carried out on paraffin-embedded tissue. qPCR was performed on RNA extracted from flash-frozen organ samples. Time-course CyTOF was applied on PBMCs isolated from whole blood.
Results. Following IRI, female mice had significantly better renal function. Renal histology showed increased tubulointerstitial lesions in males, together with significantly increased expression of IL-6 and TNF-α. In males, the secretion of pro-inflammatory cytokines was followed by a higher increase of blood neutrophils in males at postoperative day 2 (p value = 0.0062). In male kidneys, the increased damage was associated with the infiltration of an immune cluster at the corticomedullary junction and downregulation of metabolism, proliferation and survival related genes in proximal tubules. On the other hand, in females only, a subpopulation of Siglec F+ neutrophils expressed CD39 which has anti-inflammatory properties in the context of IRI.
Conclusions. Our data show an increased expression of IL-6 and TNF-α, with subsequent recruitment of neutrophils at the onset of IRI, particularly in male kidneys and peripheral blood. In females, the SiglecF+ neutrophils subpopulation was found to express the anti-inflammatory marker CD39. IL-6 and TNF- α seem to be sex-specific key regulators of this early immune response. Therapeutic targeting of these pathways could improve graft outcome in the context of kidney transplantation.