Aims/Hypothesis: Diabetic kidney disease (DKD) remains a significant cause of morbidity and mortality in people with diabetes. Though animal models have taught us much about the molecular mechanisms of DKD, translating these findings to human disease requires greater knowledge of the molecular changes caused by diabetes in human kidneys. Establishing this knowledge base requires building carefully curated, reliable, and complete repositories of human kidney tissue, as well as tissue proteomics platforms capable of simultaneous, spatially resolved examination of multiple proteins. Methods: We used the multiplexed immunofluorescence platform CO-Detection by indexing (CODEX) to image and analyze the expression of 21 proteins in 23 tissue sections from 12 individuals with diabetes and healthy kidneys (DM, 5 individuals), DKD classes IIA, and IIB (2 individuals per class), IIA-B intermediate (2 individuals), and III (one individual). Results: Analysis of the 21-plex immunofluorescence images revealed 18 cellular clusters, corresponding to 10 known kidney compartments and cell types, including proximal tubules, distal nephron, podocytes, glomerular endothelial and peritubular capillaries, blood vessels, including endothelial cells and vascular smooth muscle cells, macrophages, cells of the myeloid lineage, broad CD45+ inflammatory cells and the basement membrane. DKD progression was associated with co-localized increase in collagen IV deposition and infiltration of inflammatory cells, as well as loss of native proteins of each nephron segment at variable rates. Compartment-specific cellular changes corroborated this general theme, with compartment-specific variations. Cell type frequency and cell-to-cell adjacency highlighted (statistically) significant increase in inflammatory cells and their adjacency to tubular and aSMA+ cells in DKD kidneys. Finally, DKD progression was marked by substantial regional variability within single tissue sections, as well as variability across patients within the same DKD class. The sizable intra-personal variability in DKD severity impacts pathologic classifications, and the attendant clinical decisions, which are usually based on small tissue biopsies. Conclusions/Interpretations: High-plex immunofluorescence images revealed changes in protein expression corresponding to differences in cellular phenotypic composition and microenvironment structure with DKD progression. This initial dataset demonstrates the combined power of curated human kidney tissues, multiplexed immunofluorescence and powerful analysis tools in revealing pathophysiology of human DKD.

Background and Objective Chronic kidney disease (CKD) is associated with loss of muscle quality leading to mobility limitation and decreased independence. Identifying predictors of gait speed decline may help target rehabilitative therapies to those at highest risk of mobility impairment. Design, setting and participants, and measurements The current prospective cohort study recruited ambulatory patients with stage 1-4 CKD (eGFR 15-89 ml/min/1.73m2) from nephrology clinics. Predictors included demographic and clinical variables including GFR estimated using serum cystatin C. Outcomes were average change in gait speed (m/s) per year and inclusion in the top tertile of gait speed decline over 3 years. Linear mixed models and relative risk regression were used to estimate associations with annual gait speed changes and fastest tertile of decline. Results Among 213 participants, 81% were male, 22% were black and 43% had diabetes. Mean age was 57 years, median follow-up 3.15 years, mean baseline eGFRcysc 47.9 ml/min/1.73 m2, and median baseline gait speed 0.95m/s [IQR 0.81, 1.10]. Lower baseline eGFRcysc was associated with more rapid loss of gait speed (-0.029 m/s/year [95% CI -0.042, -0.015] per 30 ml/min/1.73 m2 lower eGFR; p<0.001). Diabetes was associated with -0.024m/s/year faster change (95% CI -0.042, -0.007; p=.007). Lower eGFRcysc was associated with a 49% greater risk of rapid gait speed decline (IRR 1.49; 95% CI 1.11, 2.00, p=.008) after adjustment. Prevalent cardiovascular disease and African American race were associated with a 45% greater (IRR 1.45; 95% CI 1.04, 2.01, p=.03) and 58% greater rate of rapid gait speed decline (IRR 1.58; 95% CI 1.09, 2.29, p=.02), respectively. Conclusions Among ambulatory, disability-free patients with CKD, lower eGFRcysc and diabetes status were associated with faster gait speed decline. Lower eGFRcysc, cardiovascular disease, and African American race were associated with rapid gait speed decline.

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