Challenges and Opportunities for the Clinical Translation of Spatial Transcriptomics Technologies.

Background: The first spatially resolved transcriptomics platforms, GeoMx (Nanostring) and Visium (10x Genomics) were launched in 2019 and were recognized as the method of the year by Nature Methods in 2020. The subsequent refinement and expansion of these and other technologies to increase -plex, work with formalin-fixed paraffin-embedded tissue, and analyze protein in addition to gene expression have only added to their significance and impact on the biomedical sciences. In this perspective, we focus on two platforms for spatial transcriptomics, GeoMx and Visium, and how these platforms have been used to provide novel insight into kidney disease. The choice of platform will depend largely on experimental questions and design. The application of these technologies to clinically sourced biopsies presents the opportunity to identify specific tissue biomarkers that help define disease etiology and more precisely target therapeutic interventions in the future. Summary: In this review, we provide a description of the existing and emerging technologies that can be used to capture spatially resolved gene and protein expression data from tissue. These technologies have provided new insight into the spatial heterogeneity of diseases, how reactions to disease are distributed within a tissue, which cells are affected, and molecular pathways that predict disease and response to therapy. Key Message: The upcoming years will see intense use of spatial transcriptomics technologies to better define the pathophysiology of kidney diseases and develop novel diagnostic tests to guide personalized treatments for patients.

Evaluation and Measurement Properties of a Patient-Reported Experience Measure for Home Dialysis.

BACKGROUND: No previously validated patient-reported experience measures exist for use among patients undergoing home dialysis. We tested the Home Dialysis Care Experience survey, a newly developed 26-item experience measure, among patients from 30 dialysis facilities in the United States. METHODS: Using mail and telephone survey modalities, we approached 1372 patients treated with peritoneal dialysis or home hemodialysis for participation. Using the results from completed surveys, we evaluated item calibration by assessing item floor and ceiling effects. We tested three sets of composite scores and used factor analysis to assess model fit for each. We evaluated associations of composite scores with global ratings and separately with patient and dialysis facility characteristics. Finally, we measured test-retest reliability in patients who completed the survey at two separate time points. RESULTS: Overall, 495 eligible patients completed at least one survey (response rate 36%). Of these, 49 completed the survey in Spanish and 61 completed a second survey within 30 days. We did not detect significant floor or ceiling effects, except for one item that demonstrated >90% responses at the top response option. Analyses supported one 12-item composite scale with high internal consistency reliability: Quality of Home Dialysis Care and Operations (Cronbach alpha=0.85). This scale strongly correlated with overall staff rating ( r =0.73) and overall center rating ( r =0.70). Patient demographic and dialysis facility characteristics were not consistently associated with composite scale scores or overall staff or center ratings. Intraclass correlation coefficients in the test-retest population were 0.74 for the Quality scale, 0.88 for overall staff rating, and 0.90 for overall center rating. CONCLUSIONS: The Home Dialysis Care Experience survey is a 26-item measure that includes one composite scale and two global rating scores and is an informative tool to evaluate patient experience of care for home dialysis.

Associations of Biomarkers of Tubular Injury and Inflammation with Biopsy Features in Type 1 Diabetes.

BACKGROUND: Whether biomarkers of tubular injury and inflammation indicate subclinical structural kidney pathology early in type 1 diabetes remains unknown. METHODS: We investigated associations of biomarkers of tubular injury and inflammation with kidney structural features in 244 adults with type 1 diabetes from the Renin-Angiotensin System Study, a randomized, placebo-controlled trial testing effects of enalapril or losartan on changes in glomerular, tubulointerstitial, and vascular parameters from baseline to 5-year kidney biopsies. Biosamples at biopsy were assessed for kidney injury molecule 1 (KIM-1), soluble TNF receptor 1 (sTNFR1), arginine-to-citrulline ratio in plasma, and uromodulin and epidermal growth factor (EGF) in urine. We examined cross-sectional correlations between biomarkers and biopsy features and baseline biomarker associations with 5-year changes in biopsy features. RESULTS: Participants' mean age was 30 years (SD 10) and diabetes duration 11 years (SD 5); 53% were women. The mean GFR measured by iohexol disappearance was 128 ml/min per 1.73 m 2 (SD 19) and median urinary albumin excretion was 5 µ g/min (interquartile range, 3-8). KIM-1 was associated with most biopsy features: higher mesangial fractional volume (0.5% [95% confidence interval (CI), 0.1 to 0.9] greater per SD KIM-1), glomerular basement membrane (GBM) width (14.2 nm [95% CI, 6.5 to 22.0] thicker), cortical interstitial fractional volume (1.1% [95% CI, 0.6 to 1.6] greater), fractional volume of cortical atrophic tubules (0.6% [95% CI, 0.2 to 0.9] greater), and arteriolar hyalinosis index (0.03 [95% CI, 0.1 to 0.05] higher). sTNFR1 was associated with higher mesangial fractional volume (0.9% [95% CI, 0.5 to 1.3] greater) and GBM width (12.5 nm [95% CI, 4.5 to 20.5] thicker) and lower GBM surface density (0.003 µ m 2 / µ m 3 [95% CI, 0.005 to 0.001] lesser). EGF and arginine-to-citrulline ratio correlated with severity of glomerular and tubulointerstitial features. Baseline sTNFR1, uromodulin, and EGF concentrations were associated with 5-year glomerular and tubulointerstitial feature progression. CONCLUSIONS: Biomarkers of tubular injury and inflammation were associated with kidney structural parameters in early type 1 diabetes and may be indicators of kidney disease risk. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: Renin Angiotensin System Study (RASS/B-RASS), NCT00143949.

Randomized crossover clinical trial of coenzyme Q10 and nicotinamide riboside in chronic kidney disease.

BackgroundCurrent studies suggest mitochondrial dysfunction is a major contributor to impaired physical performance and exercise intolerance in chronic kidney disease (CKD). We conducted a clinical trial of coenzyme Q10 (CoQ10) and nicotinamide riboside (NR) to determine their impact on exercise tolerance and metabolic profile in patients with CKD.MethodsWe conducted a randomized, placebo-controlled, double-blind, crossover trial comparing CoQ10, NR, and placebo in 25 patients with an estimated glomerular filtration rate (eGFR) of less than 60mL/min/1.73 m2. Participants received NR (1,000 mg/day), CoQ10 (1,200 mg/day), or placebo for 6 weeks each. The primary outcomes were aerobic capacity measured by peak rate of oxygen consumption (VO2 peak) and work efficiency measured using graded cycle ergometry testing. We performed semitargeted plasma metabolomics and lipidomics.ResultsParticipant mean age was 61.0 ± 11.6 years and mean eGFR was 36.9 ± 9.2 mL/min/1.73 m2. Compared with placebo, we found no differences in VO2 peak (P = 0.30, 0.17), total work (P = 0.47, 0.77), and total work efficiency (P = 0.46, 0.55) after NR or CoQ10 supplementation. NR decreased submaximal VO2 at 30 W (P = 0.03) and VO2 at 60 W (P = 0.07) compared with placebo. No changes in eGFR were observed after NR or CoQ10 treatment (P = 0.14, 0.88). CoQ10 increased free fatty acids and decreased complex medium- and long-chain triglycerides. NR supplementation significantly altered TCA cycle intermediates and glutamate that were involved in reactions that exclusively use NAD+ and NADP+ as cofactors. NR decreased a broad range of lipid groups including triglycerides and ceramides.ConclusionsSix weeks of treatment with NR or CoQ10 improved markers of systemic mitochondrial metabolism and lipid profiles but did not improve VO2 peak or total work efficiency.Trial registrationClinicalTrials.gov NCT03579693.FundingNational Institutes of Diabetes and Digestive and Kidney Diseases (grants R01 DK101509, R03 DK114502, R01 DK125794, and R01 DK101509).

Integrated Analysis of Blood and Urine Biomarkers to Identify Acute Kidney Injury Subphenotypes and Associations With Long-term Outcomes.

RATIONALE & OBJECTIVE: Acute kidney injury (AKI) is a heterogeneous clinical syndrome with varying causes, pathophysiology, and outcomes. We incorporated plasma and urine biomarker measurements to identify AKI subgroups (subphenotypes) more tightly linked to underlying pathophysiology and long-term clinical outcomes. STUDY DESIGN: Multicenter cohort study. SETTING & PARTICIPANTS: 769 hospitalized adults with AKI matched with 769 without AKI, enrolled from December 2009 to February 2015 in the ASSESS-AKI Study. PREDICTORS: 29 clinical, plasma, and urinary biomarker parameters used to identify AKI subphenotypes. OUTCOME: Composite of major adverse kidney events (MAKE) with a median follow-up period of 4.7 years. ANALYTICAL APPROACH: Latent class analysis (LCA) and k-means clustering were applied to 29 clinical, plasma, and urinary biomarker parameters. Associations between AKI subphenotypes and MAKE were analyzed using Kaplan-Meier curves and Cox proportional hazard models. RESULTS: Among 769 AKI patients both LCA and k-means identified 2 distinct AKI subphenotypes (classes 1 and 2). The long-term risk for MAKE was higher with class 2 (adjusted HR, 1.41 [95% CI, 1.08-1.84]; P=0.01) compared with class 1, adjusting for demographics, hospital level factors, and KDIGO stage of AKI. The higher risk of MAKE among class 2 was explained by a higher risk of long-term chronic kidney disease progression and dialysis. The top variables that were different between classes 1 and 2 included plasma and urinary biomarkers of inflammation and epithelial cell injury; serum creatinine ranked 20th out of the 29 variables for differentiating classes. LIMITATIONS: A replication cohort with simultaneously collected blood and urine sampling in hospitalized adults with AKI and long-term outcomes was unavailable. CONCLUSIONS: We identify 2 molecularly distinct AKI subphenotypes with differing risk of long-term outcomes, independent of the current criteria to risk stratify AKI. Future identification of AKI subphenotypes may facilitate linking therapies to underlying pathophysiology to prevent long-term sequalae after AKI. PLAIN-LANGUAGE SUMMARY: Acute kidney injury (AKI) occurs commonly in hospitalized patients and is associated with high morbidity and mortality. The AKI definition lumps many different types of AKI together, but subgroups of AKI may be more tightly linked to the underlying biology and clinical outcomes. We used 29 different clinical, blood, and urinary biomarkers and applied 2 different statistical algorithms to identify AKI subtypes and their association with long-term outcomes. Both clustering algorithms identified 2 AKI subtypes with different risk of chronic kidney disease, independent of the serum creatinine concentrations (the current gold standard to determine severity of AKI). Identification of AKI subtypes may facilitate linking therapies to underlying biology to prevent long-term consequences after AKI.

Value Placed on Comfort vs Life Prolongation Among Patients Treated With Maintenance Dialysis.

Importance: Patients receiving maintenance dialysis experience intensive patterns of end-of-life care that might not be consistent with their values. Objective: To evaluate the association of patients' health care values with engagement in advance care planning and end-of-life care. Design, Setting, and Participants: Survey study of patients who received maintenance dialysis between 2015 and 2018 at dialysis centers in the greater metropolitan areas of Seattle, Washington, and Nashville, Tennessee, with longitudinal follow-up of decedents. Logistic regression models were used to estimate probabilities. Data analysis was conducted between May and October 2022. Exposures: A survey question about the value that the participant would place on longevity-focused vs comfort-focused care if they were to become seriously ill. Main Outcomes and Measures: Self-reported engagement in advance care planning and care received near the end of life through 2020 using linked kidney registry data and Medicare claims. Results: Of 933 patients (mean [SD] age, 62.6 [14.0] years; 525 male patients [56.3%]; 254 [27.2%] identified as Black) who responded to the question about values and could be linked to registry data (65.2% response rate [933 of 1431 eligible patients]), 452 (48.4%) indicated that they would value comfort-focused care, 179 (19.2%) that they would value longevity-focused care, and 302 (32.4%) that they were unsure about the intensity of care they would value. Many had not completed an advance directive (estimated probability, 47.5% [95% CI, 42.9%-52.1%] of those who would value comfort-focused care vs 28.1% [95% CI, 24.0%-32.3%] of those who would value longevity-focused care or were unsure; P < .001), had not discussed hospice (estimated probability, 28.6% [95% CI, 24.6%-32.9%] comfort focused vs 18.2% [95% CI, 14.7%-21.7%] longevity focused or unsure; P < .001), or had not discussed stopping dialysis (estimated probability, 33.3% [95% CI, 29.0%-37.7%] comfort focused vs 21.9% [95% CI, 18.2%-25.8%] longevity focused or unsure; P < .001). Most respondents wanted to receive cardiopulmonary resuscitation (estimated probability, 78.0% [95% CI, 74.2%-81.7%] comfort focused vs 93.9% [95% CI, 91.4%-96.1%] longevity focused or unsure; P < .001) and mechanical ventilation (estimated probability, 52.0% [95% CI, 47.4%-56.6%] comfort focused vs 77.9% [95% CI, 74.0%-81.7%] longevity focused or unsure; P < .001). Among decedents, the percentages of participants who received an intensive procedure during the final month of life (estimated probability, 23.5% [95% CI, 16.5%-31.0%] comfort focused vs 26.1% [95% CI, 18.0%-34.5%] longevity focused or unsure; P = .64), discontinued dialysis (estimated probability, 38.3% [95% CI, 32.0%-44.8%] comfort focused vs 30.2% [95% CI, 23.0%-37.8%] longevity focused or unsure; P = .09), and enrolled in hospice (estimated probability, 32.2% [95% CI, 25.7%-38.7%] comfort focused vs 23.3% [95% CI, 16.4%-30.5%] longevity focused or unsure; P = .07) were not statistically different. Conclusions and Relevance: This survey study found that there appeared to be a disconnect between patients' expressed values, which were largely comfort focused, and their engagement in advance care planning and end-of-life care, which reflected a focus on longevity. These findings suggest important opportunities to improve the quality of care for patients receiving dialysis.

A Patient Decision Aid About Conservative Kidney Management in Advanced Kidney Disease: A Randomized Pilot Trial.

RATIONALE & OBJECTIVE: Available decision aids for patients about treatment of advanced chronic kidney disease (CKD) often lack information on conservative kidney management (CKM). We assessed the feasibility and acceptability of a decision aid on CKM among patients with advanced CKD and their family members. STUDY DESIGN: Randomized pilot trial. SETTING & PARTICIPANTS: Patients aged≥75 years with stage 4 or 5 CKD and their family members at 4 medical centers in the greater Seattle area between August 2020 and December 2021. INTERVENTIONS: Usual care with or without a decision aid on CKM. OUTCOME: Acceptability was assessed by attrition rates between the initial study visit (T1) and the 3-month follow-up evaluation (T3). The primary outcome and measure of feasibility was the proportion of participants who discussed CKM with a health care provider between T1 and T3. RESULTS: We randomized 92 patients of whom 86 (55.8% male; age 82±6 years; 82.6% White) completed T1-42 in the usual care arm and 44 in the usual care plus decision aid arm-and 56 family members of whom 53 (18.9% male; age 71±11 years; 86.8% White) completed T1-20 in usual care arm and 33 in the usual care plus decisions aid arm. The attrition rates were 21% versus 21% (P=1.0) for patients, and 10% versus 18% (P=0.46) for family members in the usual care versus usual care plus decisions aid arms. Receipt of the decision aid significantly increased discussion of CKM with a health care provider for patients (26.4% vs 3.0%, P=0.007) and family members (26.9% vs 0, P=0.02). LIMITATIONS: Possible limited generalizability because participants were a relatively homogenous group. The decision aid focuses on CKM and may be less applicable to those with limited knowledge of kidney replacement therapies. CONCLUSIONS: A CKM decision aid was feasible and acceptable, and increased discussion of this treatment option with health care providers. This aid may serve as a useful adjunct to the currently available educational tools on treatments for advanced CKD. FUNDING: Grant from a not-for-profit entity (National Palliative Care Research Center). TRIAL REGISTRATION: Registered at ClinicalTrials.gov with study number NCT04919941.

Metabolomic Profiling Identifies New Endogenous Markers of Tubular Secretory Clearance.

BACKGROUND: The proximal tubules eliminate protein-bound toxins and drugs through secretion. Measurements or estimates of GFR do not necessarily reflect the physiologically distinct process of secretion. Clinical assessment of this important intrinsic kidney function requires endogenous markers that are highly specific for secretory transport. METHODS: We used metabolomics profiling to identify candidate markers of tubular secretory clearance in 50 participants from a kidney pharmacokinetics study. We measured metabolites in three sequential plasma samples and a concurrent 10-hour timed urine sample using hydrophilic interaction liquid chromatography/high-resolution mass spectrometry. We quantified the association between estimated kidney clearance and normalized plasma peak height of each candidate solute to the clearance of administered furosemide, a protein-bound, avidly secreted medication. RESULTS: We identified 528 metabolites present in plasma and urine, excluding pharmaceuticals. We found seven highly (>50%) protein-bound and 49 poorly bound solutes with clearances significantly associated with furosemide clearance and 18 solute clearances favoring an association with furosemide clearance by the 90th percentile compared with GFR. We also found four highly bound and 42 poorly bound plasma levels that were significantly associated with furosemide clearance. CONCLUSIONS: We found several candidate metabolites whose kidney clearances or relative plasma levels are highly associated with furosemide clearance, an avidly secreted tracer medication of the organic anion transporters, highlighting their potential as endogenous markers of proximal tubular secretory clearance.

Tubular Secretion and Estimated GFR Decline in the Jackson Heart Study.

Introduction: Secretion of solutes by the proximal tubules represents an intrinsic kidney function not directly reflected by the glomerular filtration rate (GFR). The early loss of secretory clearance may reflect unrecognized kidney dysfunction, portending future disease progression. Methods: We designed a nested case-control study within the Jackson Heart Study (JHS), a prospective study of African American adults in Mississippi, to associate baseline differences in proximal tubular secretion of 5 endogenously produced solutes with future estimated glomerular rate (eGFR) decline. We matched 127 pairs by creatinine-eGFR, age, diabetes, and sex among the patients who provided a 24-hour urine collection; cases had a ≥25% decline in eGFR compared to <10% in controls over 10 years of follow-up. We measured baseline plasma and urine concentrations of secretory solutes using liquid chromatography-mass spectrometry to determine the odds ratio of kidney disease progression. Results: Mean age was 60 years; 76% were women; 30% had diabetes; mean baseline eGFR was 94±20 ml/min per 1.73 m2. The eGFR decline over 10 years was 38±13% in cases and 0±10% in controls. After adjustment for the matching variables plus albuminuria, systolic blood pressure, body mass index, and smoking, each 50% lower kidney clearance of isovalerylglycine, kynurenic acid, and xanthosine were associated with 1.4 to 2.2 greater odds of eGFR decline. Kynurenic acid exhibited the strongest association; each 50% lower clearance of this secretory solute was associated with 2.20-fold higher odds of eGFR decline (95% confidence interval [CI] 1.32-3.67). Conclusion: We found that in this community-based study of adults without significant kidney disease, lower proximal tubular secretory solute clearance is associated with future eGFR decline.

Population-Based Limits of Urine Creatinine Excretion.

Introduction: The validity of a timed urine collection is typically judged by measurement of urine creatinine excretion, but prevailing limits may be unreliable. We sought to empirically derive population-based limits of excretion for evaluating the validity of a timed urine collection. Methods: Covariate and 24-hour urine data were obtained from 3582 participants in the Chronic Renal Insufficiency Cohort (CRIC) study, 814 participants in the Modification of Diet in Renal Disease (MDRD) study, 1010 participants in the Jackson Heart Study (JHS), and 8536 participants in the Prevention of Renal Vascular End Stage Disease (PREVEND) study. Weight, height, age, sex, and serum creatinine concentrations were evaluated as potential predictors of urine creatinine excretion using Akaike Information Criteria, R-squared values, and deviance. Bias and precision of the fitted models were assessed by analyses of residuals. Agreement between 24-hour creatinine clearance and 125I-iothalamate clearance was assessed before and after exclusion of potentially invalid urine samples. Results: A best-fitting model to predict 24-hour urine creatinine excretion among the 9199 discovery cohort members included sex-specific terms for weight, height, and age (R-squared = 0.328). This model had a median bias of +4.3 mg creatinine/day (95% confidence interval -5.6, +13.3 mg/day) in 4599 validation cohort members, and 82% of observed values were within 30% of predicted model. Serum creatinine concentrations only marginally improved model precision but reduced bias in persons with advanced chronic kidney disease (CKD). Conclusion: The limits of urine creatinine excretion derived here represent the most valid and representative data for appraising the adequacy of a timed urine collection.

Rates of Cardiovascular Disease and CKD Progression in Young Adults with CKD across Racial and Ethnic Groups.

Background: Significant racial and ethnic disparities in cardiovascular (CV) and kidney function outcomes in older adults with chronic kidney disease (CKD) have been reported. However, little is known about the extent to which these disparities exist in patients with CKD during the foundational period of young adulthood. The objective of this study was to determine risk factors and rates of CV disease and CKD progression in young adults with CKD across racial and ethnic groups. Methods: We studied all participants aged 21-40 years of age enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study (n=317). Baseline CV risk factors were described across racial and ethnic groups. Results: Outcomes included CV events or death (first incidence of heart failure, myocardial infarction, and stroke or death) and CKD progression (>50% decline in eGFR from baseline or end stage kidney disease [ESKD]). Incidence rate ratios (IRRs) were compared as a secondary analysis for participants identifying as Black or Hispanic with those identifying as White or another race and ethnicity. Adjusted models included age, sex, and per APOL1 high-risk allele. CV risk factors were higher in Black and Hispanic participants, including mean SBP, BMI, median UACr, and LDL. Black and Hispanic participants had higher incidence rates of HF (17.5 versus 5.1/1000 person-years), all-cause mortality (15.2 versus 7.1/1000 person-years), and CKD progression (125 versus 59/1000 person-years). Conclusions: In conclusion, we found a higher prevalence of CV risk factors, some modifiable, in young adults with CKD who identify as Black or Hispanic. Future strategies to ameliorate the racial and ethnic inequality in health outcomes earlier in life for patients with CKD should be prioritized.

Association of rheumatoid arthritis with mortality in chronic kidney disease: a cohort study.

BACKGROUND: Rheumatoid arthritis (RA) is associated with an increased risk of cardiovascular disease (CVD) as well as with an increased risk of chronic kidney disease (CKD), also a known cardiovascular risk factor. However, it is not known if RA is a predictor of adverse outcomes in patients with CKD. We hypothesized that among a cohort of patients with CKD, RA would be associated with an increased risk of mortality. MATERIALS AND METHODS: We conducted a retrospective study of 3939 participants with CKD from the prospective Chronic Renal Insufficiency Cohort (CRIC) study. The primary outcome of interest was all-cause mortality. Secondary outcomes included CKD progression (defined as end-stage kidney disease or 50% decline in estimated glomerular filtration rate), cardiovascular endpoints, and composite of myocardial infarction, cerebrovascular accident, heart failure, or death. Multivariable Cox proportional hazards regression was utilized, adjusting for potential confounders including age, sex, race/ethnicity, body mass index, current smoker, and education. RESULTS: The study cohort included 83 participants with RA on a disease modifying anti-rheumatic drug (DMARD). In the adjusted analysis, CKD-RA status was significantly associated with an increased risk of death (adjusted HR, aHR, 1.73 (1.27, 2.35)) and composite outcome (aHR 1.65 (1.27-2.15)) even after adjusting for traditional risk factors. Similar statistically significant associations were observed between CKD-RA and other secondary outcomes except for CKD progression. CONCLUSION: RA was associated with higher mortality among individuals with CKD but not progressive renal decline. Further studies evaluating the mechanisms behind this association are needed. Key Points • Rheumatoid arthritis (RA) is associated with an increased risk of cardiovascular disease (CVD) as well as with an increased risk of chronic kidney disease (CKD), also a known cardiovascular risk factor. However, it is not known if RA is an independent predictor of adverse outcomes in patients with CKD • In this study, we observed that CKD patients with RA experience higher mortality as well as an increased risk of CVD compared to patients with CKD without comorbid RA • These data provide rationale for more aggressive monitoring for CVD in patients with CKD and RA. They also underscore the need for determining which interventions can help decrease the burden of mortality in these patients.

Digital spatial profiling of collapsing glomerulopathy.

Collapsing glomerulopathy is a histologically distinct variant of focal and segmental glomerulosclerosis that presents with heavy proteinuria and portends a poor prognosis. Collapsing glomerulopathy can be triggered by viral infections such as HIV or SARS-CoV-2. Transcriptional profiling of collapsing glomerulopathy lesions is difficult since only a few glomeruli may exhibit this histology within a kidney biopsy and the mechanisms driving this heterogeneity are unknown. Therefore, we used recently developed digital spatial profiling (DSP) technology which permits quantification of mRNA at the level of individual glomeruli. Using DSP, we profiled 1,852 transcripts in glomeruli isolated from formalin fixed paraffin embedded sections from HIV or SARS-CoV-2-infected patients with biopsy-confirmed collapsing glomerulopathy and used normal biopsy sections as controls. Even though glomeruli with collapsing features appeared histologically similar across both groups of patients by light microscopy, the increased resolution of DSP uncovered intra- and inter-patient heterogeneity in glomerular transcriptional profiles that were missed in early laser capture microdissection studies of pooled glomeruli. Focused validation using immunohistochemistry and RNA in situ hybridization showed good concordance with DSP results. Thus, DSP represents a powerful method to dissect transcriptional programs of pathologically discernible kidney lesions.

Clinical and biomarker modifiers of vitamin D treatment response: the Multi-Ethnic Study of Atherosclerosis.

BACKGROUND: Different 25-hydroxyvitamin D [25(OH)D] thresholds for treatment with vitamin D supplementation have been suggested and are derived almost exclusively from observational studies. Whether other characteristics, including race/ethnicity, BMI, and estimated glomerular filtration rate (eGFR), should also influence the threshold for treatment is unknown. OBJECTIVES: The aim was to identify clinical and biomarker characteristics that modify the response to vitamin D supplementation. METHODS: A total of 666 older adults in the Multi-Ethnic Study of Atherosclerosis (MESA) were randomly assigned to 16 wk of oral vitamin D3 (2000 IU/d; n = 499) or placebo (n = 167). Primary outcomes were changes in serum parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D [1,25(OH)2D] concentrations from baseline to 16 wk. RESULTS: Among 666 participants randomly assigned (mean age: 72 y; 53% female; 66% racial/ethnic minority), 611 (92%) completed the study. The mean (SD) change in PTH was -3 (16) pg/mL with vitamin D3 compared with 2 (18) pg/mL with placebo (estimated mean difference: -5; 95% CI: -8, -2 pg/mL). Within the vitamin D3 group, lower baseline 25-hydroxyvitamin D [25(OH)D] was associated with a larger decline in PTH in a nonlinear fashion. With baseline 25(OH)D ≥30 ng/mL as the reference, 25(OH)D <20 ng/mL was associated with a larger decline in PTH with vitamin D3 supplementation (-10; 95% CI: -15, -6 pg/mL), whereas 25(OH)D of 20-30 ng/mL was not (-2; 95% CI: -6, 1 pg/mL). A segmented threshold model identified a baseline 25(OH)D concentration of 21 (95% CI: 13, 31) ng/mL as an inflection point for difference in change in PTH. Race/ethnicity, BMI, and eGFR did not modify vitamin D treatment response. There was no significant change in 1,25(OH)2D in either treatment group. CONCLUSIONS: Of characteristics most commonly associated with vitamin D metabolism, only baseline 25(OH)D <20 ng/mL modified the PTH response to vitamin D supplementation, providing support from a clinical trial to use this threshold to define insufficiency. This trial was registered at clinicaltrials.gov as NCT02925195.

BP in Young Adults with CKD and Associations with Cardiovascular Events and Decline in Kidney Function.

BACKGROUND: BP is an important modifiable risk factor for cardiovascular events and CKD progression in middle-aged or older adults with CKD. However, studies describing the relationship between BP with outcomes in young adults with CKD are limited. METHODS: In an observational study, we focused on 317 young adults (aged 21-40 years) with mild to moderate CKD enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study. Exposures included baseline systolic BP evaluated continuously (per 10 mm Hg increase) and in categories (<120, 120-129, and ≥130 mm Hg). Primary outcomes included cardiovascular events (heart failure, myocardial infarction, stroke, or all-cause death) and CKD progression (50% decline of eGFR or ESKD). We used Cox proportional hazard models to test associations between baseline systolic BP with cardiovascular events and CKD progression. RESULTS: Cardiovascular events occurred in 52 participants and 161 had CKD progression during median follow-up times of 11.3 years and 4.1 years, respectively. Among those with baseline systolic BP ≥130 mm Hg, 3%/yr developed heart failure, 20%/yr had CKD progression, and 2%/yr died. In fully adjusted models, baseline systolic BP ≥130 mm Hg (versus systolic BP<120 mm Hg) was significantly associated with cardiovascular events or death (hazard ratio [HR], 2.13; 95% confidence interval [95% CI], 1.05 to 4.32) and CKD progression (HR, 1.68; 95% CI, 1.10 to 2.58). CONCLUSIONS: Among young adults with CKD, higher systolic BP is significantly associated with a greater risk of cardiovascular events and CKD progression. Trials of BP management are needed to test targets and treatment strategies specifically in young adults with CKD.

The Multi-Ethnic Study of Atherosclerosis individual response to vitamin D trial: Building a randomized clinical trial into an observational cohort study.

The INdividual response to VITamin D (INVITe) trial was a randomized, placebo-controlled, parallel group trial of vitamin D3 supplementation (2000 IU daily) designed to determine clinical and genetic characteristics that modify the response to vitamin D supplementation. To enhance internal and external validity and reduce cost, the INVITe trial was nested within the Multi-Ethnic Study of Atherosclerosis (MESA), an ongoing prospective observational cohort study. The INVITe trial enrolled a community-based population of 666 racially and ethnically diverse participants from January 2017 to April 2019. This represents 30% of 2210 MESA participants approached for screening, and 96% of those found to be eligible. Barriers to enrollment included delayed initiation of the trial relative to scheduled MESA study visits, a lower number of available MESA participants than expected, and a high prevalence (18%) of high-dose vitamin D supplementation (>1000 IU daily, an exclusion criterion). The final study visit was attended by 611 participants (92%), and median adherence was 98%. Our experience suggests that integration of a randomized trial into an existing observational cohort study may leverage strengths of the source population and enhance enrollment, retention, and adherence, although with limited enrollment capacity. The INVITe trial will use rigorously-collected data to advance understanding of individual determinants of vitamin D response.