Extracellular vesicles in urine of women with but not without kidney stones manifest patterns similar to men: a case control study.
BACKGROUND
The lifetime incidence of kidney stones is about two times greater in men compared to women. Extracellular vesicles (EVs) shed from activated cells are present in the urine and may reflect or even mediate renal physiology and/or pathology. This study was designed to standardize methodology to characterize urinary EVs by digital flow cytometry and to identify possible sex differences in EVs in persons with and without their first symptomatic kidney stones.


METHODS
Twenty-four-hour urine collections were obtained from persons presenting with their first kidney stone episode (n = 50 women, 60 men; age 19-76 years) and sex- and age-matched controls from the general population (n = 24 women, 36 men).


RESULTS
Standardization: Size of EV was variable within all groups. EV positivity was verified with two fluorophores for surface phosphatidylserine and/or using two different protein markers specific for renal-specific cells. The number of phosphatidylserine- and exosome marker-positive EVs did not correlate with urine osmolality and were similar in fresh vs. frozen and between two sequential urine collections from the same individual. Sex differences: Urine from women controls contained greater (P < 0.05) numbers of EVs positive for phosphatidylserine, exosomes, inflammatory factors and adhesion molecules, and cell-specific markers from different segments of the nephron, renal pelvis, and bladder compared to control men. In contrast, urine from women with kidney stones contained significantly (P < 0.05) lower numbers of EVs derived from podocytes, parietal cells, proximal convoluted tubule, thin and thick loop of Henle, distal tubule, collecting duct, renal pelvis, and bladder compared to control women and contained similar quantities of these types of EVs in men with and without kidney stones. There were also no sex differences in EVs positive for cell adhesion (E-cadherin and inter-cellular adhesion molecule-1 [ICAM-1]) molecules.


CONCLUSIONS
Unlike women who do not have kidney stones, EVs in urine from women with nephrolithiasis are similar to men with and without kidney stones. Thus, EVs may mediate or reflect aspects of kidney stone pathogenesis and perhaps provide clues regarding sex differences in kidney stone incidence rates.
Department of Surgery, College of Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA ; Department of Physiology & Biomedical Engineering, College of Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA.
Muthuvel
M
Jayachandran
Department of Surgery, College of Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA.
Ghiara
G
Lugo
Department of Surgery, College of Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA.
Hillary
H
Heiling
Department of Surgery, College of Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA ; Department of Physiology & Biomedical Engineering, College of Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA.
Virginia M
VM
Miller
Department of Internal Medicine, Division of Nephrology and Hypertension, College of Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA.
Andrew D
AD
Rule
Department of Internal Medicine, Division of Nephrology and Hypertension, College of Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA ; Laboratory Medicine and Pathology, College of Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA.
John C
JC
Lieske
Exosomes; Flow cytometry; Microparticles; Microvesicles; Sex differences; Urinary vesicles; Vesicles