Background/Objectives: Whole-food plant-based diets (WFPBDs) are beneficial in managing hypertension in the general population but have not been well studied in chronic kidney disease (CKD), potentially due to concerns about hyperkalemia. We hypothesized that individuals with CKD 3 or 4 attending a 15-day WFPBD education program would achieve lower blood pressure compared to those who did not, without an increased risk of hyperkalemia. Methods: This was a pilot trial of 40 subjects with mild-to-moderate CKD and hypertension but without diabetes or proteinuria from a single academic center. The subjects were randomized to the 15-day education program or the control group. The changes in blood pressure, serum potassium, and other anthropometric and biochemical values were assessed. Results: Systolic blood pressure decreased from the baseline to day 15 in the intervention group by 8 mm Hg and increased in the control group by 2.7 mm Hg, although the difference in the blood pressure change did not reach statistical significance (p = 0.12). Diastolic blood pressure was not different between the two groups. Potassium changed by 0.01 mEq/L in the intervention group and -0.07 mEq/L in the control group (p = 0.52). The intervention subjects had significant decreases in body mass (-3.0 vs. -0.12 kg, p < 0.0001), total cholesterol (-39.4 vs. -5.0 mg/dL, p < 0.0001), low-density lipoprotein (-28.4 vs. -0.6 mg/dL, p < 0.0001), and high-density lipoprotein (-8.6 vs. -0.4 mg/dL, p = 0.006) compared to the controls. The changes in albumin and phosphorus were not different between the two groups. Conclusions: The subjects with mild-to-moderate CKD attending a 15-day WFPBD education program had a non-statistically significant reduction in systolic blood pressure without an increased risk of hyperkalemia compared to those who did not attend. The intervention subjects achieved significantly greater reductions in body mass and cholesterol without adverse effects on albumin or phosphorus. Larger and longer-duration trials using this approach in a diverse group of CKD patients are warranted.

Objective: Chronic kidney disease (CKD) affects 37 million Americans resulting in $87 billion healthcare cost annually. Impaired renal autoregulation in obesity, diabetes and hypertension causes elevated glomerular capillary pressure and whole-kidney hyperfiltration, leading to progressive glomerulosclerosis and CKD. In advanced CKD with less than 50% functional nephron mass, single-nephron hyperfiltration causes further nephron loss, ultimately leading to hypofiltration and end-state kidney disease. Increased renal perfusion pressure directly drives T cell infiltration to the kidney. We and others have shown that T helper (Th) 17 cells promote vascular stiffening in hypertension and renal interstitial fibrosis after ischemia-reperfusion injury, but their roles in glomerulosclerosis and CKD are poorly understood. We hypothesized that glomerular hypertension and hyperfiltration promote renal fibrosis through Th17-mediated immune responses. Methods: We investigated the causal roles of glomerular hyperfiltration and Th17 responses in a mouse CKD model induced by reduced kidney mass (RKM), which involved right kidney nephrectomy and partial renal artery ligation in the left kidney such that the functional renal mass is reduced by ~ 5/6. Male 129/S6 mice received sham or RKM surgery at 8 weeks of age, and blood pressure (BP, by radiotelemetry), glomerular filtration rate (GFR, by transcutaneous FITC-sinistrin) and serum/urine CKD markers were assessed at baseline (BL) and week 1, 2, 3, 4, 8, and 12 post-surgery. Results: BP and GFR of RKM mice were identical to sham controls at BL (n=4-6). Immediately after the RKM procedure, GFR dropped to 22% of BL, consistent with the extent of renal mass ablation. BP increased by 29 mmHg first week after 5/6 ablation (144 ± 8 vs BL 112 ± 2 mmHg, p<0.05, 2-way ANOVA), exposing the remnant nephrons to increased renal perfusion pressure. Serum creatinine, blood urea nitrogen and urinary albumin were significantly elevated by week 2. BP and CKD markers remained elevated through week 12 in the 5/6 ablation mice. The GFR of ablated mice gradually increased to 38% of BL at day 3, 57% at week 1 and 68% at week 2, suggesting that systemic hypertension and impaired renal autoregulation may have caused substantial single-nephron hyperfiltration in the remnant kidney mass. GFR plateaued at ~ 70% of BL in week 3-4 then declined to 48% at week 8-12 when glomerular, interstitial, and microvascular fibrosis developed as evidence by Periodic Acid Schiff and Picro Sirius Red staining. Supporting a causal role of hemodynamic derangements in CKD progression, calcium channel blocker amlodipine, a potent vasodilator, dose dependently (5-10 mg/kg/day, n=7-9) exacerbated glomerular hyperfiltration, glomerulosclerosis and mortality despite marked BP-lowering effects. Importantly, the adaptive increase of GFR in the first 2 weeks post 5/6 ablation was accompanied by significant increase of renal Th17 cells, which not only preceded the infiltration of CD11b+ myeloid cells, F4/80+ monocyte/macrophages and T regulatory cells, but also the glomerulosclerosis and GFR decline in week 8. Conclusions: Our data suggest that glomerular hyperfiltration causes progressive nephron loss and kidney fibrosis, at least in part, through Th17-mediated renal inflammation. To further establish causality, ongoing studies will assess if Th17 blockade ameliorates glomerulosclerosis and retard CKD progression. Funding: This work was supported by NIDDK R01 DK094907, R01 DK113632, R01 DK128677 to THL, and K01 DK126972 to JW. JW is also supported by an American Heart Association Second Century Early Faculty Independence Award (23SCEFIA1148464), a University of Rochester Environmental Health Science Center pilot award (Prime sponsor: NIEHS P30ES001247), and a University of Rochester Program for Advanced Immune Bioimaging Pilot Award (Prime Sponsor: NIAID P01AI102851). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Impaired renal autoregulation in obesity, diabetes and hypertension (HTN) causes elevated glomerular capillary pressure and glomerular hyperfiltration, initiating progressive glomerulosclerosis (GS), nephron loss and chronic kidney disease (CKD). Increased renal perfusion pressure drives renal T cell infiltration. T helper (Th) 17 cells promote vascular stiffening in HTN and renal interstitial fibrosis post AKI, but their roles in GS and CKD are poorly understood. We hypothesized that glomerular hyperfiltration promotes CKD through Th17-mediated GS and tested the hypothesis in 129S6 mice using the reduced kidney mass model (RKM) induced by uninephrectomy and partial renal artery ligation in the remaining kidney (functional renal mass reduced by ~ 5/6). BP (radiotelemetry) and GFR (FITC-sinistrin) of RKM mice were identical to sham controls at baseline (BL, n=4-6). Immediately after the RKM procedure, GFR dropped to 22% of BL, consistent with the extent of renal mass ablation. Mean BP increased by 29 mmHg first week after 5/6 ablation (144 ± 8 vs BL 112 ± 2 mmHg, p<0.05, 2-way ANOVA) and remained elevated through week 12, exposing the remnant nephrons to increased renal perfusion pressure. Serum creatinine, BUN and urinary albumin were significantly elevated after 5/6 ablation. In RKM mice, GFR gradually increased to 38% of BL at day 3, 57% at week 1 and 68% at week 2, suggesting that systemic HTN and impaired renal autoregulation may have caused substantial single-nephron hyperfiltration in the remnant kidney. GFR plateaued at ~ 70% of BL in week 3-4 then declined to 48% at week 8 when glomerular, interstitial, and microvascular fibrosis developed as evidence by Periodic Acid Schiff and Picro Sirius Red staining. Importantly, the early adaptive increase of GFR in the first 2 weeks post 5/6 ablation was accompanied by a striking increase of renal interleukin (IL)-17A+ T cells, which preceded the late infiltration of CD11b+ myeloid cells, F4/80+ monocyte/macrophages, and T regulatory cells. Anti-IL17A antibodies (eBioMM17F3, 100 μg i.p. twice weekly) attenuated the early hyperfiltration, abolished aortic/renal inflammation, and prevented GFR decline and GS at week 8 in male but not female RKM mice, likely due to the anti-hypertensive and anti-inflammatory effects of IL-17A neutralization. We conclude that glomerular hyperfiltration causes progressive nephron loss and kidney fibrosis in CKD, at least in part, through IL-17A mediated renal inflammation.

Renal autoregulation maintains renal blood flow and glomerular filtration rate (GFR) in a wide range of renal perfusion pressure (RPP). This mechanism is impaired in diabetes and chronic kidney disease (CKD), such that even modest increases in arterial pressure (AP) are transmitted to glomerular capillaries resulting in glomerular injury. Elevated RPP drives renal immune cell infiltration ( Hypertens. 76: 849-858, 2020). We showed that hypertensive mechanical stretch and T cell cytokine interleukin (IL)-17A synergistically promote vascular fibrosis ( Wu, Circ. Res. 114: 616-625, 2014). However, the mechanisms by which hemodynamic and inflammatory stimuli cause CKD remain poorly understood. We sought to investigate the contributions of glomerular hyperfiltration (GHF) and inflammation on glomerular damage in a mouse CKD model induced by reduced kidney mass (RKM). This model is characterized by impaired autoregulation, early onset hypertension and subsequent lymphocytic inflammation, albuminuria and glomerulosclerosis. We hypothesize that the initial rise in AP post RKM surgery promotes kidney injury through both GHF and renal inflammation. Eight-week old male 129/S6 mice were implanted with radiotelemeters. After a 10-day recovery, mice underwent sham surgery or RKM which involved uninephrectomy and partial renal artery ligation in the remaining kidney, such that the functional renal mass is reduced by ~ 2/3. AP, urine albumin, and transcutaneous GFR were measured at baseline, day (D) 3, D7, D14, D21, D28, and D56 after RKM.Immediately after RKM, GFR dropped to 30% of sham levels (Mean ± SEM in μL/min/100 g: RKM 279 ± 59 vs Sham 913 ± 61, n = 4 – 6, p < 0.05, two-way ANOVA RM), consistent with the extent of renal mass ablation. The mean AP of RKM mice was identical to sham controls at baseline (115 ± 2 vs 116 ± 2 mmHg) but increased by 29 mmHg by D5 (144 ± 8 vs 112 ± 2 mmHg, p < 0.05), and remained significantly elevated through D56, albeit a declining trend. Compared to GFR of sham mice (100%), the GFR of RKM mice gradually increased to 36% at D3, 43% at D7 and 69% at D14. By D21 post surgery, the GFR of RKM mice rose to 71% of sham (800 ± 106 vs 1121 ± 47 μL/min/100 g, p > 0.05) and plateaued through day 28 (69% of sham), suggesting that the early rise in AP and impaired autoregulation may have caused GHF in the RKM mice. The adaptive increase in GFR post RKM surgery was associated with a trend towards increased renal leukocytes, monocyte/macrophages, CD3 T cells and CD4/CD8 subsets at D14 and significantly elevated albuminuria at D28 (832 ± 227 vs 341 ± 15 μg/day, p < 0.05), implying hyperfiltration-induced renal inflammation and glomerular damage. Importantly, the GFR declined to 57% of sham levels by day 56 (597 ± 86 vs 1047 ± 80 μL/min/100 g, p < 0.05), suggesting progressive glomerular injury. We conclude that impaired autoregulation exposes the kidney to both inflammation and GHF, causing glomerular injury, albuminuria, and CKD progression. This work is supported by a NIDDK K01 DK126792 and a University of Rochester Environmental Health Science Center Pilot award (as part of a NIEHS P30ES001247) to JW. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Background: Glutathione-S-transferase Mu1( Gstm1 ) gene encodes an enzyme that functions in the detoxification of electrophilic compounds. The common GSTM1 deletion variant in humans is associated with increased risks of chronic kidney disease progression. We reported that deletion of Gstm1 in mice increases oxidative stress, kidney inflammation and injury in angiotensin II induced hypertension (Ang II-HTN). Bone marrow cross-transplantation suggested a chemotaxis signal originating from the kidney. Moreover, we recently found that global deletion of Gstm1 significantly increased neutrophil chemotaxis response to CXCL1 and CXCL2 in vitro and kidney neutrophil populations early in Ang II-HTN by day 4. To test whether early activation of neutrophil mediates inflammation and kidney injury in Gstm1 KO mice, we depleted neutrophils using Ly6G antibody. Methods: Gstm1 KO male mice (12 weeks old) on 129S6 background were used for the study. After a 2-week training period, baseline systolic blood pressure (SBP) was measured by tail cuff daily for 2 weeks. For neutrophil depletion, Ly6G antibody (1A8, BioXcell ) (n=3) or control IgG (2A3)(n=2) were injected IP (200 μg/mouse) at 48hr and 24hr before Ang II mini-osmotic pump was implanted (1000 ng/kg/minute). A third IP injection was performed at day 4 after the Ang II. SBP was measured for 8 days during Ang II-HTN. FACS analysis was performed at day 8 post Ang II to determine the efficiency of neutrophil depletion. Results: Compared to control IgG, Ly6G antibody significantly depleted neutrophil populations in the kidney, bone marrow, and spleen by 95%, 97%, and 93%, respectively. Baseline SBP was similar between the two groups (129.5 ± 6.7 vs 128.3 ± 0.8 mm Hg, p = 0.9). In Ang II-HTN, depletion of neutrophils with Ly6G antibody in Gstm1 KO mice resulted in a trend in decrease in SBP compared to control antibody (154.7 ± 17.9 vs 182.6 ± 2.6 mm Hg; p = 0.13). Conclusion: Loss of Gstm1 activates neutrophils early in Ang II-HTN. Successful depletion of neutrophils in Gstm1 KO mice decreased blood pressure in response to Ang II. Further studies are underway to confirm the pressor response and to determine whether depletion of neutrophils early in Ang II-HTN can ameliorate kidney inflammation and injury in GSTM1 deficiency.

Metabolic acidosis (MET) stimulates bone resorption through inhibition of osteoblast (OB) bone formation and stimulation of osteoclast (OC) bone resorption. We found that OGR1, a G protein-coupled proton (H+)-sensing receptor, was critical for initial H+ signaling in the OB. In mice with a global deletion of OGR1, we demonstrated that loss of OGR1 impairs H+-induced bone resorption, leading to increased bone density through effects on both the OB and OC. Using an OC-specific deletion of OGR1, we found that MET directly activates OGR1 in the OC. To determine if the response of OGR1 to MET in the OB is independent of a response in OCs and to characterize direct activation of OGR1 in the OB, we studied female mice with an OB-specific deletion of OGR1 (OB-cKO) and differentiated osteoblasts derived from marrow of OB-cKO and wild-type (WT) mice. In OB-cKO mice, we found increased bone area in both tibial and femoral cortical bone. Specific loss of OB OGR1 increased in vitro mineralization, alkaline phosphatase activity, and expression of osteoblast-specific genes compared with WT with no alteration in OC activity. MET stimulation of OB cox2 and fgf23 gene expression was inhibited in OB-cKO OB. These results indicate that MET activation of OGR1 in the OB is independent of the response in the OC and that OGR1 in both cell types is required for a complete response to MET. Characterization of the role of OGR1 in MET-induced bone resorption will improve our understanding of bone loss associated with metabolic acidosis in patients with chronic kidney disease. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Background Transmembrane protein 27 (TMEM27/collectrin), a glycoprotein and homolog of angiotensin-converting enzyme 2 (ACE2), is a regulator of renal amino acid uptake in the proximal tubule and may have a protective role in hypertension. Two previous reports have shown that the absence of TMEM27 expression in clear cell renal cell carcinoma (ccRCC) correlates with poorer cancer-related survival. We report our findings of TMEM27 expression in ccRCC and clinical outcomes in an independent third cohort. Material and Methods We conducted a retrospective analysis to identify all 321 cases of ccRCC diagnosed between 2010 and 2015 at the University of Rochester Medical Center. The intensity of TMEM27 immunostaining on tumor tissue was semi-quantitatively graded on a scale of 0, 0.5, 1, 1.5, 2, 2.5, and 3 by a single pathologist, and correlated with tumor characteristics and survival. Results There was evidence of metastasis at time of nephrectomy in 36 (11.2%) cases, and at the latest follow-up in 70 (21.8%) cases. As of Spring 2021, 82 (25.5%) had died. TMEM27 staining intensity correlated inversely with various tumor characteristics. Kaplan-Meier survival analysis showed worse overall all-cause mortality (p = 0.02) and disease-free survival (p = 0.028) for tumors without any TMEM27 staining (0) compared to 0.5 or higher by log-rank test. Conclusion The absence of TMEM27 expression is associated with more aggressive tumor characteristics and poorer all-cause mortality and disease-free survival in ccRCC. TMEM27 may be a useful biomarker to assess cancer prognosis. Further studies are needed to better assess if TMEM27 is protective in RCC, and its potential role in active surveillance and prediction of response to target therapy.

The findings of our study are significant in several ways: 1) loss of an amino acid chaperone in the proximal tubule is sufficient to cause hypertension, 2) the results in global and proximal tubule-specific collectrin knockout mice support the notion that vascular dysfunction is required for salt sensitivity or that impaired renal tubule function causes hypertension but is not sufficient to cause salt sensitivity, and 3) our study is the first to implicate a role of collectrin in human hypertension.

Wang, Yves T.; Chen, Luojing; Beane, Timothy J.; Nguyen, Nhu; Le, Thu H. Author Information

Background: Glutathione-S-transferase Mu1( Gstm1 ) gene, a member of Glutathione-S-transferases (GST) superfamily, encodes an enzyme that functions in the detoxification of electrophilic compounds. The common GSTM1 deletion variant in humans is associated with increased risks of chronic kidney disease (CKD) progression and incident end stage kidney failure. We reported that deletion of Gstm1 increases oxidative stress, kidney inflammation and injury in angiotensin II induced hypertension (Ang II-HTN) in mice. At 4 weeks of Ang II-HTN, neutrophils, CD4+T cells, and F4/80+ cells were significantly increased in Gstm1 knockout (KO) kidney. While a link between oxidative stress and immune activation in hypertension has been well documented, the molecular mechanism by which Gstm1 regulates immune cell activation in hypertension is unknown. Methods: To further characterize the inflammatory response in GSTM1 deficiency, Gstm1 KO and wild-type (WT) male mice at ~ 12 weeks of age were subjected to Angiotensin II at 1000 ng/kg per minute for 4 days via a mini osmotic pump. The kidney cells and bone marrow cells were isolated for flow cytometry analysis. Results: At baseline, there were no differences in inflammatory cell populations including neutrophils between WT and Gstm1 KO mice. At Day 4 of Ang II-HTN, Gstm1 KO kidneys exhibited about a 2.3 fold increase in neutrophil population (CD45 + Ly6G + CD11b + ), compared to WT control mice (10 WT and 8 Gstm1 KO mice, p=0.0075). Interestingly, CD45+ bone marrow cells isolated from both Gstm1 KO and WT mice have similar percentile of neutrophil populations ; however, neutrophils in Gstm1 KO bone marrow express relatively higher levels of CXCR2. Unlike at 4 weeks, there was no difference in other inflammatory cells at Day 4. Conclusion: Deletion of Gstm1 increases renal neutrophil population early in Ang II-HTN and CXCR2 expression in bone marrow neutrophils. Gstm1 may play a role in regulating neutrophil migration and recruitment. Further studies are needed to delineate whether GSTM1 deficiency drives kidney injury via early neutrophil migration, which could shed light on potential therapeutic target for CKD progression in those genetically susceptible.

To study human idiopathic hypercalciuria we developed an animal model, genetic hypercalciuric stone-forming rats, whose pathophysiology parallels that of human idiopathic hypercalciuria. Fed the oxalate precursor, hydroxyproline, every rat in this model develops calcium oxalate stones. Using this rat model, we tested whether chlorthalidone and potassium citrate combined would reduce calcium oxalate stone formation and improve bone quality more than either agent alone. These rats (113 generation) were fed a normal calcium and phosphorus diet with hydroxyproline and divided into four groups: diets plus potassium chloride as control, potassium citrate, chlorthalidone plus potassium chloride, or potassium citrate plus chlorthalidone. Urine was collected at six, 12, and 18 weeks and kidney stone formation and bone parameters were determined. Compared to potassium chloride, potassium citrate reduced urinary calcium, chlorthalidone reduced it further and potassium citrate plus chlorthalidone even further. Potassium citrate plus chlorthalidone decreased urine oxalate compared to all other groups. There were no significant differences in calcium oxalate supersaturation in any group. Neither potassium citrate nor chlorthalidone altered stone formation. However, potassium citrate plus chlorthalidone significantly reduced stone formation. Vertebral trabecular bone increased with chlorthalidone and potassium citrate plus chlorthalidone. Cortical bone area increased with chlorthalidone but not potassium citrate or potassium citrate plus chlorthalidone. Mechanical properties of trabecular bone improved with chlorthalidone, but not with potassium citrate plus chlorthalidone. Thus in genetic hypercalciuric stone-forming rats fed a diet resulting in calcium oxalate stone formation, potassium citrate plus chlorthalidone prevented stone formation better than either agent alone. Chlorthalidone alone improved bone quality, but adding potassium citrate provided no additional benefit.

You have accessJournal of UrologyStone Disease: Basic Research & Pathophysiology I (PD04)1 Apr 2020PD04-01 ANTIBIOTICS AFFECT THE GUT MICROBIOME AND ALTER KIDNEY STONE FORMATION IN GENETIC HYPERCALCIURIC STONE-FORMING RATS Joshua Stern*, John Asplin, Nancy Krieger, Sylvia Suadicani, Luojing Chen, Jennifer Becker, Michaela Chan, Justin Lee, Yi Wang, and David Bushinsky Joshua Stern*Joshua Stern* More articles by this author , John AsplinJohn Asplin More articles by this author , Nancy KriegerNancy Krieger More articles by this author , Sylvia SuadicaniSylvia Suadicani More articles by this author , Luojing ChenLuojing Chen More articles by this author , Jennifer BeckerJennifer Becker More articles by this author , Michaela ChanMichaela Chan More articles by this author , Justin LeeJustin Lee More articles by this author , Yi WangYi Wang More articles by this author , and David BushinskyDavid Bushinsky More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000000824.01AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Recent evidence suggests both antibiotic exposure and the gut microbiome (GMB) are associated with stone disease. Antibiotics can cause rapid alterations in the GMB. We utilized genetic hypercalciuric stone-forming (GHS) rats that form calcium phosphate (CaP) stones, to determine the effect of antibiotics on the gut microbiome, urine ion excretion and stone formation. METHODS: 116th generation GHS rats were fed a fixed amount of a normal Ca (1.2%) and P (0.65%) diet, housed in metabolic cages and divided into 3 groups (n=10): control (CTL) diet, or supplemented with ciprofloxacin (Cipro, 5 mg/d) or Bactrim (250 mg/d). Urine and fecal pellets were collected at 6, 12 and 18 wks for analyses. DNA from fecal pellets were amplified on the 16S rRNA V4 region using primers on an Illumina platform. QIIME was used for analysis. At 18 wks kidney stone formation was determined by Faxitron analysis and assessed by 3 blinded reviewers. RESULTS: After 18 wks, urine Ca decreased with Bactrim (CTL=13.7± 0.4, Bactrim=12.1±0.4 mg/d, p<0.05) as did urine oxalate (CTL=1.2±0.04, Bactrim=0.8±0.02 mg/d, p<0.05). CaP supersaturation increased with Bactrim (CTL=6.8±0.4, Bactrim=8.4±0.5, p<0.05) while CaOx supersaturation fell (CTL=16.2± 0.6, Bactrim=12.0±0.4, p<0.05). Calcification was increased with Bactrim (CTL=1.0±0.2, Bactrim=2.98±0.3, p<0.05). Cipro was not different from CTL for any parameter. Principal component analysis of the GMB showed the Bactrim group and controls clustered separately (p=0.001). Microbial diversity negatively correlated with urinary oxalate in all animals (R=-0.46, p=0.006) and positively correlated with urinary pH in the Bactrim group (R=0.76, p=0.01). CONCLUSIONS: Bactrim altered the GMB of GHS rats, decreased urine Ca, increased CaP supersaturation and increased calcification, while Cipro had no effects. Whether the alteration in the GMB is mechanistically related to the changes in urine ion excretion and calcification remains to be determined. Source of Funding: NIDDK © 2020 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 203Issue Supplement 4April 2020Page: e78-e78 Advertisement Copyright & Permissions© 2020 by American Urological Association Education and Research, Inc.MetricsAuthor Information Joshua Stern* More articles by this author John Asplin More articles by this author Nancy Krieger More articles by this author Sylvia Suadicani More articles by this author Luojing Chen More articles by this author Jennifer Becker More articles by this author Michaela Chan More articles by this author Justin Lee More articles by this author Yi Wang More articles by this author David Bushinsky More articles by this author Expand All Advertisement PDF downloadLoading ...

To study human idiopathic hypercalciuria (IH), we developed an animal model, genetic hypercalciuric stone-forming (GHS) rats, whose pathophysiology parallels that in IH. All GHS rats form kidney stones and have decreased BMD and bone quality compared with the founder Sprague-Dawley (SD) rats. To understand the bone defect, we characterized osteoclast and osteoblast activity in the GHS compared with SD rats. Bone marrow cells were isolated from femurs of GHS and SD rats and cultured to optimize differentiation into osteoclasts or osteoblasts. Osteoclasts were stained for TRAcP (tartrate resistant acid phosphatase), cultured to assess resorptive activity, and analyzed for specific gene expression. Marrow stromal cells or primary neonatal calvarial cells were differentiated to osteoblasts, and osteoblastic gene expression as well as mineralization was analyzed. There was increased osteoclastogenesis and increased resorption pit formation in GHS compared with SD cultures. Osteoclasts had increased expression of cathepsin K, Tracp, and MMP9 in cells from GHS compared with SD rats. Osteoblastic gene expression and mineralization was significantly decreased. Thus, alterations in baseline activity of both osteoclasts and osteoblasts in GHS rats, led to decreased BMD and bone quality, perhaps because of their known increase in vitamin D receptors. Better understanding of the role of GHS bone cells in decreased BMD and quality may provide new strategies to mitigate the low BMD and increased fracture risk found in patients with IH. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Metabolic acidosis induces osteoclastic bone resorption and inhibits osteoblastic bone formation. Previously we found that mice with a global deletion of the proton receptor OGR1 had increased bone density although both osteoblast and osteoclast activity were increased. To test whether direct effects on osteoclast OGR1 are critical for metabolic acidosis stimulated bone resorption, we generated knockout mice with an osteoclast-specific deletion of OGR1 (knockout mice). We studied bones from three-month old female mice and the differentiated osteoclasts derived from bone marrow of femurs from these knockout and wild type mice. MicroCT demonstrated increased density in tibiae and femurs but not in vertebrae of the knockout mice. Tartrate resistant acid phosphatase staining of tibia indicated a decrease in osteoclast number and surface area/bone surface from knockout compared to wild type mice. Osteoclasts derived from the marrow of knockout mice demonstrated decreased pit formation, osteoclast staining and osteoclast-specific gene expression compared to those from wild type mice. In response to metabolic acidosis, osteoclasts from knockout mice had decreased nuclear translocation of NFATc1, a transcriptional regulator of differentiation, and no increase in size or number compared to osteoclasts from wild type mice. Thus, loss of osteoclast OGR1 decreased both basal and metabolic acidosis-induced osteoclast activity indicating osteoclast OGR1 is important in mediating metabolic acidosis-induced bone resorption. Understanding the role of OGR1 in metabolic acidosis-induced bone resorption will provide insight into bone loss in acidotic patients with chronic kidney disease.

Antibiotics can alter the gut microbiome (GMB), which may be associated with stone disease. We sought to determine the effect that antibiotics have on the GMB, urine ion excretion and stone formation in genetic hypercalciuric stone-forming (GHS) rats. 116th generation GHS rats were fed a fixed amount of a normal calcium (1.2%) and phosphate (0.65%) diet, and divided into three groups (n = 10): control (CTL) diet, or supplemented with ciprofloxacin (Cipro, 5 mg/day) or Bactrim (250 mg/day). Urine and fecal pellets were collected over 6, 12 and 18 weeks. Fecal DNA was amplified across the 16S rRNA V4 region. At 18 weeks, kidney stone formation was visualized by Faxitron and blindly assessed by three investigators. After 18 weeks, urine calcium and oxalate decreased with Bactrim compared to CTL and Cipro. Urine pH increased with Bactrim compared to CTL and Cipro. Urine citrate increased with Cipro compared to CTL and decreased by half with Bactrim. Calcification increased with Bactrim compared to CTL and Cipro. Increased microbial diversity correlated with decreased urinary oxalate in all animals (R = − 0.46, p = 0.006). A potential microbial network emerged as significantly associated with shifts in urinary pH. Bactrim and Cipro differentially altered the GMB of GHS rats. The Bactrim group experienced a decrease in urine calcium, increased CaP supersaturation and increased calcification. The GMB is likely a contributing factor to changes in urine chemistry, supersaturation and stone risk. Further investigation is required to fully understand the association between antibiotics, the GMB and kidney stone formation.