Alexander, Mariam P.

Key Points Increased protein expression of tissue inhibitor of metalloproteinase-3, glypican 6, synuclein γ , apolipoprotein A-4, and Ecto-5′-nucleotidase was observed in old adults compared with young adults. In old adults, overexpressed proteins were enriched in mitochondrial processes while under expressed proteins enriched in RNA metabolism. Validated differentially expressed proteins were not significantly correlated with kidney pathology after adjusting for age. Background Kidney aging is characterized by a loss of glomeruli, predominantly in the superficial cortex, with a resultant decline in GFR and an increased risk of various kidney-related diseases. The early molecular alterations in glomeruli associated with the aging process are not well studied. Methods We combined laser capture microdissection and mass spectrometry–based unbiased proteomic analysis of nonsclerosed, nonischemic glomeruli in the superficial cortex from young and old adults who underwent a radical nephrectomy for a tumor to understand the age-related molecular changes in glomeruli. Twenty-four young and 30 old adults were used for the discovery dataset, and the significant differentially expressed proteins were further validated using an independent set comprising six young and eight old adults. Results Kidneys from old adults had lower eGFR, less kidney parenchyma on computed tomography imaging, and more glomerulosclerosis and arteriosclerosis on histology. Quantitative proteomic analysis of nonsclerosed, nonischemic glomeruli identified increased expression of tissue inhibitor of metalloproteinase-3, glypican 6, synuclein γ , apolipoprotein A-4, and Ecto-5′-nucleotidase in old adults that were further validated in an independent set. Pathway analysis indicated that proteins with increased expression in old adults were enriched in mitochondrial translational processes, aerobic respiration, and TCA cycle, whereas proteins with decreased expression in old adults were enriched in mRNA splicing, mRNA processing, and nonsense mediated decay. Furthermore, validated differentially expressed proteins did not show any significant correlation with the kidney pathology independent of age group. Conclusions Overall, this study identified proteins that are specifically associated with the aging process in otherwise normal-appearing glomeruli.

Background: Vascular endothelial growth factor inhibitors (VEGF-I) are frequently used for cancer treatment. VEGF-I can cause proteinuria and acute kidney injury (AKI) with thrombotic microangiopathy (TMA) as a commonly described pathology, but other glomerular pathologies are not well characterized. We aim to describe the clinical characteristics and glomerular lesions associated with VEFG-I in a single center cohort. Methods: We performed a retrospective chart review of patients treated with VEGF-I and underwent kidney biopsies from 2010 to 2022 at the Mayo Clinic, Rochester, MN. Biopsy findings were reviewed by our pathologists. Data on patients’ characteristics, clinical course, and outcomes were abstracted. Descriptive statistics were used to report relevant patient characteristics and findings. Results: From 2010 to 2022, 19 kidney biopsies were performed for kidney dysfunction in patients on VEGF-I. Eleven had complete data, with a median age of 62 years (interquartile range 58–66 years); renal cell carcinoma (RCC) was the most common cancer (4 of 11 patients). TMA was noted in 8 of the 11 biopsies, with proteinuria as the most frequent indication for biopsy in these cases. Three patients had findings other than TMA. One developed anti-phospholipase A2 receptor negative membranous nephropathy; VEGF-I and pembrolizumab were discontinued, and prednisone improved proteinuria. Another patient had known cryoglobulinemia with nephrotic range proteinuria which was exacerbated by VEGF-I peaking at 11 g/day. Despite stopping VEGF-I and treating with prednisone and rituximab, kidney dysfunction progressed to end stage kidney disease (ESKD). A third patient had IgA nephropathy with concurrent diabetic changes, but proteinuria progressed even after stopping VEGF-I. Conclusion: In this case-series of patients treated with VEGF-I undergoing kidney biopsy, we describe the pathological characteristics, clinical course, and outcomes of patients with pathologies other than TMA. Our study adds information to the sparse literature on patients with renal dysfunction after receiving VEGF-I.