Cross-sex transplantation alters gene expression and enhances inflammatory response in the transplanted kidneys

Abstract

Kidney transplantation (KTX) is a life-saving procedure for patients with end-stage renal disease. Expression levels of many genes in the kidney vary between males and females, which may play an essential role in the sex differences in graft function. However, whether these differences are affected after cross-sex-KTX is unknown. In the present study, we assessed postoperative changes in genotype, function, and inflammatory responses of the grafts in same-sex- and cross-sex-KTX. Single kidney transplants were performed between same and different sex C57BL/6 mice paired into four combination groups: female donor/female recipient (F/F); male donor/male recipient (M/M); female donor/male recipient (F/M); and male donor/female recipient (M/F). The remnant native kidney was removed 4 days posttransplant. Expression levels of genes related to the contractility of the afferent arteriole and tubular sodium reabsorption were assessed. Same-sex-KTX did not significantly alter the magnitude or sex difference pattern of gene expression in male or female grafts. Cross-sex-KTX showed an attenuated sex difference in gene expressions. The measurements of endothelin 1, endothelin ET_A receptor, Na⁺-K^--2Cl cotransporter 2 (NKCC2), and epithelial Na⁺ channels (ENaC) subunits exhibited decreases in M/F compared with M/M and increases in F/M compared with F/F. There were no significant differences in hemodynamics or sodium excretion in response to acute volume expansion for any sex combinations. Cross-sex-KTX stimulated more robust inflammatory responses than same-sex-KTX. IL-6 and KC mRNA levels elevated 5- to 20-fold in cross-sex-KTX compared with same-sex-KTX. In conclusion, cross-sex-KTX alters gene expression levels and induces inflammatory responses, which might play an important role in long-term graft function.

Keywords: mouse kidney transplantation; receptors and sodium transporter; sex difference.

Fig. 1.

The relative renal gene expression of the components in renin-angiotensin system (RAS) and endothelin (ET) system. M, male; F, female; FC, female control; MC, male control; AT₁R and AT₂R, angiotensin II receptors. Renal gene expression of AT₁R (A; *P < 0.01 vs. FC; #P < 0.01 vs. F/F; %P < 0.05 vs. F/F); AT₂R (B; *P < 0.01 vs. FC; #P < 0.01 vs. F/F; &P < 0.05 vs. M/M); ET-1 (C; *P < 0.01 vs. FC; #P < 0.01 vs. F/F and M/F; %P < 0.01 vs. F/F); ET_A (D; *P < 0.01 vs. FC; #P < 0.01 vs. F/F; &P < 0.05 vs. F/M); and ET_B (E; #P < 0.05 vs. F/F; %P < 0.05 vs. F/F) of the transplanted kidneys at 4 wk after transplantation (donor/recipient; M, male, F, female; n = 6).

Fig. 2.

The relative renal gene expression of the sodium transporters. Renal gene expression of Na⁺/H⁺ exchanger 3 (NHE3; A; *P < 0.01 vs. M/M; &P < 0.01 vs. M/M and F/M; @P < 0.05 vs. F/F). Protein levels showed the similar pattern as mRNA expression. Na⁺-K⁻-2Cl cotransporter 2 (NKCC2; B; *P < 0.01 vs. FC; #P < 0.01 vs. F/F); Na⁺-Cl⁻ cotransporter (NCC; C; *P < 0.01 vs. FC; #P < 0.01 vs. F/F; &P < 0.01 vs. F/M); and α (E)-, β (D)- and γ (F)-epithelial Na⁺ channels (ENaC) (*P < 0.01 vs. FC; #P < 0.01 vs. F/F;) of the transplanted kidneys at 4 wk after transplantation. Protein levels of NHE3 and NKCC2 showed the similar sex difference pattern as mRNA expression, respectively (donor/recipient; M, male, F, female; n = 6).

Fig. 2.

The relative renal gene expression of the sodium transporters. Renal gene expression of Na⁺/H⁺ exchanger 3 (NHE3; A; *P < 0.01 vs. M/M; &P < 0.01 vs. M/M and F/M; @P < 0.05 vs. F/F). Protein levels showed the similar pattern as mRNA expression. Na⁺-K⁻-2Cl cotransporter 2 (NKCC2; B; *P < 0.01 vs. FC; #P < 0.01 vs. F/F); Na⁺-Cl⁻ cotransporter (NCC; C; *P < 0.01 vs. FC; #P < 0.01 vs. F/F; &P < 0.01 vs. F/M); and α (E)-, β (D)- and γ (F)-epithelial Na⁺ channels (ENaC) (*P < 0.01 vs. FC; #P < 0.01 vs. F/F;) of the transplanted kidneys at 4 wk after transplantation. Protein levels of NHE3 and NKCC2 showed the similar sex difference pattern as mRNA expression, respectively (donor/recipient; M, male, F, female; n = 6).

Fig. 3.

The relative renal gene expression of the inflammation factors. Renal gene expression of the inflammation factors: IL-6 (A; &P < 0.01 vs. M/M and F/M; % P < 0.01 vs. F/F); keratinocyte-derived chemokine (KC; B; *P < 0.01 vs FC; #P < 0.01 vs. F/F; &P < 0.01 vs. M/M and %P < 0.01 vs. F/F); TGF-β (C; #P < 0.01 vs. F/F; $P < 0.01 vs. F/M); TNF-α (D; #P < 0.01 vs. F/F in D1; *P < 0.01 vs. FC; #P < 0.01 vs. F/F; &P < 0.01 vs. F/M in D3); INF-γ (E); IL-17 (F; #P < 0.01 vs. MC and F/F; &P < 0.01 vs. MC); CCL2 (G; &P < 0.01 vs. M/M and F/M); and CCL5 (H; &P < 0.01 vs. M/M and F/M) of the transplanted kidneys at 4 wk after transplantation. (donor/recipient; M, male, F, female; n = 6).

Fig. 3.

The relative renal gene expression of the inflammation factors. Renal gene expression of the inflammation factors: IL-6 (A; &P < 0.01 vs. M/M and F/M; % P < 0.01 vs. F/F); keratinocyte-derived chemokine (KC; B; *P < 0.01 vs FC; #P < 0.01 vs. F/F; &P < 0.01 vs. M/M and %P < 0.01 vs. F/F); TGF-β (C; #P < 0.01 vs. F/F; $P < 0.01 vs. F/M); TNF-α (D; #P < 0.01 vs. F/F in D1; *P < 0.01 vs. FC; #P < 0.01 vs. F/F; &P < 0.01 vs. F/M in D3); INF-γ (E); IL-17 (F; #P < 0.01 vs. MC and F/F; &P < 0.01 vs. MC); CCL2 (G; &P < 0.01 vs. M/M and F/M); and CCL5 (H; &P < 0.01 vs. M/M and F/M) of the transplanted kidneys at 4 wk after transplantation. (donor/recipient; M, male, F, female; n = 6).

Fig. 4.

Histology The kidney grafts in all groups demonstrated preserved architecture, normal intrarenal arteries. No significant tubular injuries, interstitial fibrosis, or vascular abnormalities were evident in the kidney grafts.

Fig. 5.

Renal clearance function of transplanted kidneys in response to acute volume expansion. Renal clearance function was measured at basal and during 0–60 and 60–90 min after an acute volume expansion (AVE) by infusion of 3% body wt of 0.9% NaCl saline. A: mean arterial pressure (MAP); B: glomerular filtration rate (GFR); C: urinary flow rate; D: Na⁺ excretion. GFR rose by ≈30% during 60 min after AVE and returned almost to baseline 90 min after AVE. The urinary flow rates and sodium excretion rates increased ~25–35% in all groups of animals within 60 min after AVE (*P < 0.01 vs. basal and 60–90 min, n = 6).