The relationship of peritubular capillary density with glomerular volume and kidney function in living kidney donors

BACKGROUND

Peritubular capillary rarefaction plays an important role in the progression of chronic kidney disease. Little is known about the relation between peritubular capillary density, glomerular volume and filtration rate in the healthy kidney.

METHODS

In this single-center study, we included 69 living kidney donors who donated between 2005 and 2008 and had representative renal biopsies available. In all donors, glomerular filtration rate was measured using 125I-Iothalamate before donation and at five years after donation. Before donation, the increase in glomerular filtration rate after dopamine stimulation was measured. Glomerular volume and peritubular capillary density were determined in biopsies taken at the time of transplantation. Pearson's correlation coefficient and linear regression were used to assess relations between parameters.

RESULTS

Mean donor age was 52 ± 11 years and mean measured glomerular filtration rate was 119 ± 22 mL/min before donation and 82 ± 15 mL/min at five years after donation. While peritubular capillary density (measured by either number of peritubular capillaries/50,000 μm2 or number of peritubular capillaries/tubule) was not associated with measured glomerular filtration rate before or after donation, number of peritubular capillaries/tubule was associated with the increase in measured glomerular filtration rate after dopamine stimulation (St.β = 0.33, p = 0.004), and correlated positively with glomerular volume (R = 0.24, p = 0.047). Glomerular volume was associated with unstimulated measured glomerular filtration rate before donation (St.β = 0.31, p = 0.01) and at five years (St.β = 0.30, p = 0.01) after donation, independent of age.

CONCLUSIONS

In summary, peritubular capillary density was not related to unstimulated kidney function before or after kidney donation, in contrast to glomerular volume. However, number of peritubular capillaries/tubule correlated with the increase in glomerular filtration rate after dopamine stimulation in healthy kidneys, and with glomerular volume. These findings suggest that peritubular capillary density and glomerular volume differentially affect kidney function in healthy living kidney donors.

The Association between Glomerular Diameter and Secondary Focal Segmental Glomerulosclerosis in Chronic Kidney Disease

INTRODUCTION

When nephron loss occurs, the glomerular filtration rate (GFR) is suggested to be maintained by glomerular hypertrophy, but excessive hypertrophy can rather lead to the formation of focal segmental glomerulosclerosis (FSGS), thereby causing progressive kidney damage. However, it is not clear how much glomerular hypertrophy leads to the formation of FSGS. We examined the association between glomerular diameter and FSGS lesions in chronic kidney disease (CKD) patients.

METHODS

We recruited 77 patients who underwent renal biopsy during 2016-2017; however, those identified with primary FSGS and glomerulonephritis with active glomerular lesion were excluded. We evaluated the maximal glomerular diameter (Max GD), an indicator of glomerular size, in each renal biopsy specimen and examined its association with FSGS lesion.

RESULTS

The median age, blood pressure, and estimated GFR of the patients were 53 years, 122/70 mm Hg, and 65 mL/min/1.73 m2, respectively. The optimal cutoff threshold of Max GD for predicting the presence of FSGS lesions, assessed by receiver operating characteristic curve analysis, was determined to be at 224 μm (area under the curve, 0.81; sensitivity, 81%; specificity, 72%). Multivariate logistic regression analyses demonstrated that Max GD ≥224 μm was significantly associated with the presence of FSGS lesions, independent of other confounding factors (odds ratio, 11.70; 95% confidence interval, 1.93-70.84).

DISCUSSION/CONCLUSION

Glomerular hypertrophy (Max GD ≥224 μm) has been associated with FSGS lesions in CKD patients and may reflect the limits of the compensatory process.

Efficacy of a Si-based agent against developing renal failure in a rat remnant kidney model

Chronic renal failure is exacerbated by oxidative stress, and this condition is difficult to treat in advanced stages. Because of the lack of effective treatments, the disease is a global public health concern. We developed a Si-based agent that continuously generates hydrogen for more than 24 h by reacting with water under conditions similar to those in the gastrointestinal tract. Given the efficacy of hydrogen in the treatment of conditions associated with oxidative stress, we examined whether the Si-based agent had beneficial effects on the development of renal failure. The Si-based agent was orally administered to rats that were developing renal failure. Rats underwent 5/6 nephrectomy to establish a remnant kidney model. Specifically, on day -7, rats underwent right 2/3 nephrectomy, followed by light nephrectomy on day 0. Starting on day -3, the rats were administered a control or Si-based agent-containing diet for 8 weeks. Compared with the findings in control rats, the Si-based agent greatly suppressed the increases of both serum creatinine and urinary protein levels. All analyzed parameters of oxidative stress were significantly suppressed in the Si-based agent groups. Histopathological examination illustrated that glomerular hypertrophy was suppressed by the treatment. Quantitative real-time reverse transcription-polymerase chain reaction revealed that sirtuin 1 and heme oxygenase-1 expression was increased in the Si-based agent groups, suggesting improved antioxidant activity and reduced hypoxia. In addition, caspase-3 and interleukin-6 expression was suppressed in the Si-based agent groups, indicating the alleviation of apoptosis and inflammation. In conclusion, oral administration of a Si-based agent resulted in renoprotective effects, presumably by suppressing oxidative stress via hydrogen generation.

Consequences of Glomerular Hyperfiltration: The Role of Physical Forces in the Pathogenesis of Chronic Kidney Disease in Diabetes and Obesity

BACKGROUND

Glomerular hyperfiltration (GH) is a hallmark of renal dysfunction in diabetes and obesity. Recent clinical trials demonstrated that SGLT2 inhibitors are renoprotective, possibly by abating hyperfiltration. The present review considers the current evidence for a cause-to-effect relationship between hyperfiltration-related physical forces and the development of chronic kidney disease (CKD).

SUMMARY

Glomerular hyperfiltration is associated with glomerular and tubular hypertrophy. Hyperfiltration is mainly due to an increase in glomerular capillary pressure, which increases tensile stress applied to the capillary wall structures. In addition, the increased ultrafiltrate flow into Bowman's space heightens shear stress on the podocyte foot processes and body surface. These mechanical stresses lead to an increase in glomerular basement membrane (GBM) length and to podocyte hypertrophy. The ability of the podocyte to grow being limited, a mismatch develops between the GBM area and the GBM area covered by foot processes, leading to podocyte injury, detachment of viable podocytes, adherence of capillaries to parietal epithelium, synechia formation and segmental sclerosis. Mechanical stress is also applied to post-filtration structures, resulting in dilation of glomerular and tubular urinary spaces, increased proximal tubular sodium reabsorption by hypertrophied epithelial cells and activation of mediators leading to tubulointerstitial inflammation, hypoxia and fibrosis Key Messages: GH-related mechanical stress leads to both adaptive and maladaptive glomerular and tubular changes. These flow-related effects play a central role in the pathogenesis of glomerular disease. Attenuation of hyperfiltration is thus an important therapeutic target in diabetes and obesity-induced CKD.

Cobalt treatment does not prevent glomerular morphological alterations in type 1 diabetic rats

Early renal morphological alterations including glomerular hypertrophy and mesangial expansion occur in diabetic kidney disease and correlate with various clinical manifestations of diabetes. The present study was designed to investigate the influence of pharmacological modulation of HIF-1α (hypoxia inducible factor-1 alpha) protein levels, on these glomerular changes in rodent model of type 1 diabetes. Male wistar rats were made diabetic (Streptozotocin 45 mg/kg; i.p.) and afterwards treated with HIF activator cobalt chloride for 4 weeks. Renal function was assessed by serum creatinine, albumin, proteinuria levels, oxidative stress: reduced glutathione levels and catalase activity, and renal tissue HIF-1α protein levels were determined by ELISA assay. Histological analysis of kidney sections was done by haematoxylin and eosin (glomeruli diameter), periodic acid Schiff (mesangial expansion and glomerulosclerosis) and sirius red (fibrosis, tubular dilation) staining. Diabetes rats displayed reduced serum albumin levels, marked proteinuria, lower kidney reduced glutathione content, glomerular hypertrophy, glomerulosclerosis, mesangial expansion, tubular dilation and renal fibrosis. Cobalt chloride treatment normalised renal HIF-1α protein levels, reduced development of proteinuria and tubulo-interstitial fibrosis, but the glomerular morphological alterations such as glomerulosclerosis, mesangial expansion, increased glomerular diameter and tubular vacoulations were not abrogated in diabetic kidneys. Glomerular morphological abnormalities might precede the development of proteinuria and renal fibrosis in experimental model of type 1 diabetes. Pharmacological modulation of renal HIF-1α protein levels does not influence glomerular and tubular dilatory changes in diabetic kidney disease.

Measurement of glomerulus diameter and Bowman's space width of renal albino rats

Glomerulus diameter and Bowman's space width in renal microscopic images indicate various diseases. Therefore, the detection of the renal corpuscle and related objects is a key step in histopathological evaluation of renal microscopic images. However, the task of automatic glomeruli detection is challenging due to their wide intensity variation, besides the inconsistency in terms of shape and size of the glomeruli in the renal corpuscle. Here, a novel solution is proposed which includes the Particles Analyzer technique based on median filter for morphological image processing to detect the renal corpuscle objects. Afterwards, the glomerulus diameter and Bowman's space width are measured. The solution was tested with a dataset of 21 rats' renal corpuscle images acquired using light microscope. The experimental results proved that the proposed solution can detect the renal corpuscle and its objects efficiently. As well as, the proposed solution has the ability to manage any input images assuring its robustness to the deformations of the glomeruli even with the glomerular hypertrophy cases. Also, the results reported significant difference between the control and affected (due to ingested additional daily dose (14.6mg) of fructose) groups in terms of glomerulus diameter (97.40±19.02μm and 177.03±54.48μm, respectively).

Down-regulation of miR-34a alleviates mesangial proliferation in vitro and glomerular hypertrophy in early diabetic nephropathy mice by targeting GAS1

AIMS

Diabetic nephropathy (DN) is a major diabetic complication characterized by mesangial proliferation and glomerular hypertrophy. MicroRNAs might play an important role in these pathological processes. The aim of this study is to examine the possible association of miR-34a as one of the microRNAs with DN and underlying mechanisms in vitro and in vivo.

METHODS

According to previous results of microarray which compared the different microRNAs between diabetic and normal control mice, miR-34a was chosen and its expression was detected by qRT-PCR. Cell viability was then assessed using Cell Counting Kit-8 (CCK8) and 5-ethynyl-20-deoxyuridine (EDU) incorporation. Antagomir was injected in db/db mice to down regulate miR-34a. Average diameter of glomeruli was analyzed by periodic acid-Schiff (PAS) stain of kidney. Luciferase gene report assay was then performed to identify the target gene of miR-34a. Additional immunoblotting and immunohistochemical analyses were implemented to verify the expression level of growth arrest-specific 1 (GAS1).

RESULTS

MiR-34a expression level was increased under high glucose condition in vitro and in vivo. Down-regulation of miR-34a inhibits mice mesangial cells (MMCs) proliferation in vitro and alleviates glomerular hypertrophy in vivo. GAS1 was proved to be the target of miR-34a through luciferase report. Moreover, up-regulation of GAS1 expression was observed in the presence of miR-34a antagomir as compared with miR-34a antagomir-NC in high-glucose-treated MMCs and db/db mice, respectively.

CONCLUSIONS

MiR-34a regulated mesangial proliferation and glomerular hypertrophy by directly inhibiting GAS1 in early DN.

Early chronic low-level lead exposure produces glomerular hypertrophy in young C57BL/6J mice

Early chronic lead exposure continues to pose serious health risks for children, particularly those living in lower socioeconomic environments. This study examined effects on developing glomeruli in young C57BL/6J mice exposed to low (30 ppm), higher (330 ppm) or no lead via dams' drinking water from birth to sacrifice on post-natal day 28. Low-level lead exposed mice [BLL mean (SD); 3.19 (0.70) μg/dL] had an increase in glomerular volume but no change in podocyte number compared to control mice [0.03 (0.01) μg/dL]. Higher-level lead exposed mice [14.68 (2.74) μg/dL] had no change in either glomerular volume or podocyte number. The increase in glomerular volume was explained by increases in glomerular capillary and mesangial volumes with no change in podocyte volume. Early chronic lead exposure yielding very low blood lead levels alters glomerular development in pre-adolescent animals.

Hyperglycemia and renal mass ablation synergistically augment albuminuria in the diabetic subtotally nephrectomized rat: implications for modeling diabetic nephropathy

Background/AimsBackground/Aims

While experimental models that emulate diabetic nephropathy are valuable tools for elucidating pathogenetic mechanisms and developing novel therapies, existing models imperfectly recapitulate human disease. In diabetes, hyperglycemia and hemodynamic forces act in concert to induce renal injury. Accordingly, in the present study, we combined streptozotocin-induced diabetes with surgical ablation of 5/6 of the kidney mass with the aim of evaluating their additive effects on renal function and glomerular morphology.

Methods

Female F344 rats were randomized to undergo subtotal nephrectomy (SNx) either at baseline or following 4 weeks of diabetes.

Results

In comparison to sham rats, rats with diabetes or rats after SNx surgery, diabetic subtotally nephrectomized (DM-SNx) rats demonstrated an increase in systolic blood pressure, glomerular volume and mesangial matrix. Albuminuria was synergistically increased by hyperglycemia and renal mass ablation associated with decreased nephrin expression. In contrast, glomerular capillary rarefaction and glomerular filtration rate were similarly reduced in SNx and DM-SNx rats.

Conclusion

The DM-SNx rat recapitulates some of the features of human disease, most notably augmented albuminuria. Since this model avoids the deletion or overexpression of gene(s) linked to the pathogenesis of nephropathy, the DM-SNx rat model represents a complementary tool for the trial of novel therapies.