Dissecting recipient from donor contribution in experimental kidney transplantation: focus on endothelial proliferation and inflammation

Time- and Gender-Dependent Alterations in Mice during the Aging Process

Compared to young people and adults, there are differences in the ability of elderly people to resist diseases or injuries, with some noticeable features being gender-dependent. However, gender differences in age-related viscera alterations are not clear. To evaluate a potential possibility of gender differences during the natural aging process, we used three age groups to investigate the impact on spleens, kidneys, and adrenal glands. The immunofluorescence results showed that male-specific p21 proteins were concentrated in the renal tubule epithelial cells of the kidney. Histological staining revealed an increase in the frequencies of fat vacuoles located in the renal tubule epithelial cells of the cortex, under the renal capsule in the kidneys of male mice with age. In female mice, we found that the width of the globular zone in the adrenal gland cortex was unchanged with age. On the contrary, the male displayed a reduction in width. Compared to females, the content of epinephrine in adrenal gland tissue according to ELISA analysis was higher in adults, and a greater decline was observed in aged males particularly. These data confirmed the age-dependent differences between female and male mice; therefore, gender should be considered one of the major factors for personalized treatment in clinical diagnosis and treatment.

Long-Term Protection of CHBP Against Combinational Renal Injury Induced by Both Ischemia-Reperfusion and Cyclosporine A in Mice

Renal ischemia–reperfusion (IR) injury and cyclosporine A (CsA) nephrotoxicity affect allograft function and survival. The prolonged effects and underlying mechanisms of erythropoietin derived cyclic helix B peptide (CHBP) and/or caspase-3 small interfering RNA (CASP-3siRNA) were investigated in mouse kidneys, as well as kidney epithelial cells (TCMK-1), subjected to transplant-related injuries. Bilateral renal pedicles were clamped for 30 min followed by reperfusion for 2 and 8 weeks, with/without 35 mg/kg CsA gavage daily and/or 24 nmol/kg CHBP intraperitoneal injection every 3 days. The ratio of urinary albumin to creatinine was raised by IR injury, further increased by CsA and lowered by CHBP at 2, 4, 6 and 8 weeks, whereas the level of SCr was not significantly affected. Similar change trends were revealed in tubulointerstitial damage and fibrosis, HMGB1 and active CASP-3 protein. Increased apoptotic cells in IR kidneys were decreased by CsA and CHBP at 2 and/or 8 weeks. p70 S6 kinase and mTOR were reduced by CsA with/without CHBP at 2 weeks, so were S6 ribosomal protein and GSK-3β at 8 weeks, with reduced CASP-3 at both time points. CASP-3 was further decreased by CHBP in IR or IR + CsA kidneys at 2 or 8 weeks. Furthermore, in TCMK-1 cells CsA induced apoptosis was decreased by CHBP and/or CASP-3siRNA treatment. Taken together, CHBP predominantly protects kidneys against IR injury at 2 weeks and/or CsA nephrotoxicity at 8 weeks, with different underlying mechanisms. Urinary albumin/creatinine is a good biomarker in monitoring the progression of transplant-related injuries. CsA divergently affects apoptosis in kidneys and cultured kidney epithelial cells, in which CHBP and/or CASP-3siRNA reduces inflammation and apoptosis.

Cardiac Protection by Oral Sodium Thiosulfate in a Rat Model of L-NNA-Induced Heart Disease

Hypertension contributes to cardiac damage and remodeling. Despite the availability of renin-angiotensin system inhibitors and other antihypertensive therapies, some patients still develop heart failure. Novel therapeutic approaches are required that are effective and without major adverse effects. Sodium Thiosulfate (STS), a reversible oxidation product of hydrogen sulfide (H₂S), is a promising pharmacological entity with vasodilator and anti-oxidant potential that is clinically approved for the treatment of calciphylaxis and cyanide poisoning. We hypothesized that Sodium Thiosulfate improves cardiac disease in an experimental hypertension model and sought to investigate its cardioprotective effects by direct comparison to the ACE-inhibitor lisinopril, alone and in combination, using a rat model of chronic nitric oxide (NO) deficiency. Systemic nitric oxide production was inhibited in Sprague Dawley rats by administering N-ω-nitro-l-arginine (L-NNA) with the food for three weeks, leading to progressive hypertension, cardiac dysfunction and remodeling. We observed that STS, orally administered via the drinking water, ameliorated L-NNA-induced heart disease. Treatment with STS for two weeks ameliorated hypertension and improved systolic function, left ventricular hypertrophy, cardiac fibrosis and oxidative stress, without causing metabolic acidosis as is sometimes observed following parenteral administration of this drug. STS and lisinopril had similar protective effects that were not additive when combined. Our findings indicate that oral intervention with a H₂S donor such as STS has cardioprotective properties without noticeable side effects.

A plasma creatinine- and urea-based equation to estimate glomerular filtration rate in rats

Monitoring renal function is a vital part of kidney research involving rats. The laborious measurement of glomerular filtration rate (GFR) with administration of exogenous filtration markers does not easily allow serial measurements. Using an in-house database of inulin clearances, we developed and validated a plasma creatinine- and plasma urea-based equation to estimate GFR in a large cohort of male rats [development cohort n = 325, R² = 0.816, percentage of predictions that fell within 30% of the true value (P30) = 76%] that had high accuracy in the validation cohort (n = 116 rats, R² = 0.935, P30 = 79%). The equation was less accurate in rats with nonsteady-state creatinine, in which the equation should therefore not be used. In conclusion, applying this equation facilitates easy and repeatable estimates of GFR in rats.NEW & NOTEWORTHY This is the first equation, that we know of, which estimates glomerular filtration rate in rats based on a single measurement of body weight, plasma creatinine, and plasma urea.

Complement C3 deficiency ameliorates aging related changes in the kidney

AIMS

Complement C3 (C3) has been shown to be involved in the aging process. However, the role of C3 in kidney aging has not been fully elucidated. This study aimed to investigate the effect of C3 on senescence related kidney disorders in mice.

MATERIALS AND METHODS

Two-, 8-, and 16-month-old C3-deficient male mice (KO) (n = 6) and age-, gender-, and strain- matched wild type (WT) C57BL/6 mice (n = 6) were selected to represent young, middle-aged and aging mice. Renal, blood and urine samples were collected. Hematoxylin-eosin (HE), Masson, and immunohistochemistry (IHC) staining as well as ELISA and Western blotting were used to explore the mechanisms involved in renal aging.

KEY FINDINGS

The level of C3 was upregulated during aging in WT mice. The glomerular sclerosis index and tubulointerstitial fibrosis index were increased significantly in WT mice during aging. Renal function was not significantly different between the young and aged groups. Compared with those in WT mice, the levels of inflammation and fibrosis were decreased, while the expression of CD31 was significantly increased in the KO group.

SIGNIFICANCE

Our data demonstrated that age-related changes in renal structure occur earlier than functional changes and that complement C3 is involved in aging-related kidney disorder.

Is interleukin-6 receptor blockade (tocilizumab) beneficial or detrimental to pig-to-baboon organ xenotransplantation?

The interleukin (IL)-6/IL-6 receptor-α (IL-6Rα)/signal transduction and activation of the transcription 3 (STAT3) pathway plays an important role in inflammation. Anti-human IL-6Rα blockade by tocilizumab (TCZ) has been used in pig-to-baboon organ xenotransplant models, but whether it is beneficial remains uncertain. After xenotransplant, there were significant increases in both baboon and pig IL-6 in the baboon serum, especially in baboons that received TCZ before xenotransplant. In vitro observations demonstrated that human, baboon, and pig IL-6 can activate the IL-6/IL-6Rα/STAT3 pathway in human, baboon, and pig cells, respectively. Activation of the IL-6/IL-6Rα/STAT3 pathway was blocked by TCZ in human and baboon cells but not in pig cells (ie, pig IL-6R). Siltuximab (human IL-6 inhibitor) bound to both human and baboon, but not pig, IL-6 and suppressed activation of the IL-6/IL-6Rα/STAT3 pathway. These results indicate that TCZ and siltuximab do not cross-react with pig IL-6R and pig IL-6, respectively. Rapamycin partially inhibited human, baboon, and pig IL-6/IL-6Rα/STAT3 pathways and suppressed inflammatory gene expression. TCZ treatment increased serum IL-6 because it could no longer bind to baboon IL-6Rα. We suggest that increased serum IL-6 may be detrimental to the pig xenograft because it is likely to bind to pig IL-6R, resulting in activation of pig cells.

Aerobic Endurance Exercise Ameliorates Renal Vascular Sclerosis in Aged Mice by Regulating PI3K/AKT/mTOR Signaling Pathway

Renal vascular sclerosis caused by aging plays an important role in the occurrence and development of chronic kidney disease. Clinical studies have confirmed that endurance exercise is able to delay the aging of skeletal muscle and brain tissue. However, to date, few studies have assessed whether endurance exercise is able to improve the occurrence of renal vascular sclerosis caused by natural aging and its related mechanisms. In this study, we investigated the protective effect of aerobic endurance exercise on renal vascular sclerosis in aged mice and its effect on the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway. The results suggested that aerobic endurance exercise preserved kidney morphology and renal function. Glomerular basement membrane thickness was evidently increased, podocyte foot processes were effaced in aged mice, and aerobic endurance exercise significantly ameliorated the overall lesion range. The protein expression of vascular endothelial growth factor (VEGF) and JG12 was lower in the senile control group (OC group). The protein expression of VEGF and JG12 was significantly increased after aerobic endurance exercise. Furthermore, aerobic endurance exercise resulted in downregulation of Bax, Caspase 3, IL-6, and senescent cells and upregulation of Bcl-2. The upregulation of PI3K and its downstream signal molecules AKT and mTOR after aerobic endurance exercise was further observed. Our observations indicated that aerobic endurance exercise may inhibit renal vascular sclerosis in aged mice by regulating the PI3K/AKT/mTOR signaling pathway.

Dissociation between hypertrophy and fibrosis in the left ventricle early after experimental kidney transplantation

OBJECTIVE

Left ventricular (LV) hypertrophy is the most common cardiac alteration in patients with chronic kidney disease (CKD). Normalization of hypertension in CKD patients receiving a healthy kidney allograft often reverses LV hypertrophy, but effects on LV fibrosis remain unclear. To study causal interactions between graft and environment on LV hypertrophy, fibrosis and inflammation, we applied cross-kidney transplantation METHODS:: Orthotopic transplantation was performed after inducing CKD in rats by two-third bilateral ablation of kidney mass: Healthy kidney (K) donor to healthy heart (H) recipient (healthy-K→healthy-H); CKD-K→healthy-H; healthy-K→CKD-H; CKD-K→CKD-H; N= 6 per group.

RESULTS

At week 6 after transplantation, mean arterial pressure (MAP) and LV mass index (LVMI) increased in CKD-K versus healthy-K irrespective of recipient. Contrarily, LV fibrosis was more severe in CKD-H versus healthy-H recipients irrespective of graft. Indeed, MAP and plasma creatinine correlated with LVMI but not with LV fibrosis. Increased LVMI in CKD-K→CKD-H not accompanied by cardiomyocyte cross-sectional area gain is consistent with eccentric remodelling. Cardiac RNA sequencing found a strong transcriptional response associated with LV fibrosis but only sparse changes associated with LV hypertrophy. This response was, among others, characterized by changes in extracellular matrix (ECM) and inflammatory gene expression.

CONCLUSION

LVMI reversed and MAP and renal function were normalized early after transplantation of a healthy kidney. However, LV fibrosis persisted, dissociating LV hypertrophy from LV fibrosis within 6 weeks. Elucidating cardiac ECM dynamics in CKD patients, although challenging, appears promising.