KIDNEY STONE DISEASE AND OSTEOPOROSIS - TOPIC ISSUES OF COMORBIDITY

the prevalence of kidney stone disease (KSD) and osteoporosis (OP) increases every year. In the prevention of osteoporosis, it is important to consume a sufficient amount of calcium-rich foods in the daily diet, as well as the use of calcium. One of the important reasons for the insufficient use of calcium-containing products and medicines is the anxiety not only of patients, but, very importantly, of doctors as much as possible. This has serious justification, as nephrolithiasis occurs in approximately 5% of the population, and the risk of developing kidney stones during life is 8-10%. It is believed that secondary hyperparathyroidism, which is caused by hypocalcemia due to insufficient consumption of calcium-containing products and impaired renal function, leads to increased bone resorption, formation of kidney stone disease. It is important to consider that against the background of hypertensive, atherosclerotic kidney disease, tubulo-interstitial lesions of the kidneys with decreasing glomerular filtration rate decreases the synthesis of 1α-hydroxylase - an enzyme by which 25-hydroxycholecalciferol (25 (OH) active D3, calcium) form of vitamin D3–1.25 dihydroxycholecalciferol (1.25 (OH) 2D3, calcitriol - D-hormone) and secondary hyperparathyroidism develops. In this case, the purpose of correction along with the treatment of urolithiasis (spa treatment, given the attendance of the presence of KSD, to carry out the distance lithotripsy), intake of active metabolites of vitamin D (should be started with low doses, independent of the initial PTH concentration, and then titrated based on the PTH response) conducting X-ray densitometry.

The developing kidney actively negotiates geometric packing conflicts to avoid defects

The physiological functions of several organs rely on branched tubular networks, but little is known about conflicts in development between building enough tubules for adequate function and geometric constraints imposed by organ size. We show that the mouse embryonic kidney epithelium negotiates a physical packing conflict between tubule tip duplication and limited area at the organ surface. Imaging, computational, and soft material modeling of tubule 'families' identifies six geometric packing phases, including two defective ones. Experiments in kidney explants show that a retrograde tension on tubule families is necessary and sufficient for them to avoid defects by switching to a vertical orientation that increases packing density. These results reveal developmental contingencies in response to physical limitations, and create a framework for classifying kidney defects.

The laminin-binding integrins regulate nuclear factor kappa-β-dependent epithelial cell polarity and inflammation

The main laminin (LM)-binding integrins α3β1, α6β1 and α6β4 are co-expressed in the developing kidney collecting duct (CD) system. We previously showed that deleting the integrin α3 or α6 subunit in the ureteric bud (UB), which gives rise to the kidney collecting system, caused either a mild or no branching morphogenesis phenotype, respectively. To determine whether these two integrin subunits co-operate in kidney CD development, we deleted α3 and α6 in the developing UB. The collecting system of the double knockout phenocopied the α3 integrin conditional knockout. However, with age the mice developed severe inflammation and fibrosis around the CDs resulting in kidney failure. Integrin α3α6 null CD epithelial cells showed increased secretion of pro-inflammatory cytokines and displayed mesenchymal characterisitcs causing loss of barrier function. These features resulted from increased NF-κB activity, which regulated the Snail/Slug transcription factors and their downstream targets. These data suggest that LM-binding integrins play a key role in the maintenance of kidney tubule epithelial cell polarity and decrease pro-inflammatory cytokine secretion by regulating NF-κB-dependent signaling.

Single-cell RNA sequencing reveals differential cell cycle activity in key cell populations during nephrogenesis

The kidney is a complex organ composed of more than 30 terminally differentiated cell types that all are required to perform its numerous homeostatic functions. Defects in kidney development are a significant cause of chronic kidney disease in children, which can lead to kidney failure that can only be treated by transplant or dialysis. A better understanding of molecular mechanisms that drive kidney development is important for designing strategies to enhance renal repair and regeneration. In this study, we profiled gene expression in the developing mouse kidney at embryonic day 14.5 at single-cell resolution. Consistent with previous studies, clusters with distinct transcriptional signatures clearly identify major compartments and cell types of the developing kidney. Cell cycle activity distinguishes between the “primed” and “self-renewing” sub-populations of nephron progenitors, with increased expression of the cell cycle-related genes Birc5, Cdca3, Smc2 and Smc4 in “primed” nephron progenitors. In addition, augmented expression of cell cycle related genes Birc5, Cks2, Ccnb1, Ccnd1 and Tuba1a/b was detected in immature distal tubules, suggesting cell cycle regulation may be required for early events of nephron patterning and tubular fusion between the distal nephron and collecting duct epithelia.

The origin and role of the renal stroma

ABSTRACT The postnatal kidney is predominantly composed of nephron epithelia with the interstitial components representing a small proportion of the final organ, except in the diseased state. This is in stark contrast to the developing organ, which arises from the mesoderm and comprises an expansive stromal population with distinct regional gene expression. In many organs, the identity and ultimate function of an epithelium is tightly regulated by the surrounding stroma during development. However, although the presence of a renal stromal stem cell population has been demonstrated, the focus has been on understanding the process of nephrogenesis whereas the role of distinct stromal components during kidney morphogenesis is less clear. In this Review, we consider what is known about the role of the stroma of the developing kidney in nephrogenesis, where these cells come from as well as their heterogeneity, and reflect on how this information may improve human kidney organoid models.

Secondhand smoke increases the risk of developing kidney stone disease

Research indicates smoking increases the risk of various kidney diseases, although the risk of developing kidney stone disease in non-smokers exposed to secondhand smoke is unknown. This study analyzed a total of 19,430 never-smokers with no history of kidney stone disease who participated in the Taiwan Biobank from 2008 to 2019. They were divided into two groups by secondhand smoke exposure; no exposure and exposure groups; the mean age of participants was 51 years, and 81% were women. Incident kidney stone development was observed in 352 (2.0%) and 50 (3.3%) participants in the no exposure and exposure groups during a mean follow-up of 47 months. The odds ratio (OR) of incident kidney stone was significantly higher in the exposure group than the no exposure group [OR, 1.64; 95% confidence interval (95% CI) 1.21 to 2.23]. Participants with > 1.2 h per week exposure were associated with almost twofold risk of developing kidney stones compared with no exposure (OR, 1.92; 95% CI 1.29 to 2.86). Our study suggests that secondhand smoke is a risk factor for development of kidney stones and supports the need for a prospective evaluation of this finding.

Renal biomarkers of acute kidney injury in response to increasing intermittent hypoxia episodes in the neonatal rat

Background We tested the hypotheses that: 1) early exposure to increasing episodes of clinically relevant intermittent hypoxia (IH) is detrimental to the developing kidneys; and 2) there is a critical number of daily IH episodes which will result in irreparable renal damage that may involve angiotensin (Ang) II and endothelin (ET)-1. Methods At birth (P0), neonatal rat pups were exposed to brief IH episodes from the first day of life (P0) to P7 or from P0-P14. Pups were either euthanized immediately or placed in room air (RA) until P21. RA littermates served as controls. Kidneys were harvested at P7, P14, and P21 for histopathology; angiotensin converting enzyme (ACE), ACE-2, ET-1, big ET-1, and malondialdehyde (MDA) levels; immunoreactivity of ACE, ACE-2, ET-1, ET-2, ET receptors (ETAR, ETBR), and hypoxia inducible factor (HIF)1α; and apoptosis (TUNEL stain). Results Histopathology showed increased renal damage with 8–12 IH episodes/day, and was associated with Ang II, ACE, HIF1α, and apoptosis. ACE-2 was not expressed at P7, and minimally increased at P14. However, a robust ACE-2 response was seen during recovery with maximum levels noted in the groups recovering from 8 IH episodes/day. ET-1, big ET-1, ETAR, ETBR, and MDA increased with increasing levels of neonatal IH. Conclusions Chronic neonatal IH causes severe damage to the developing kidney with associated elevations in vasoconstrictors, suggesting hypertension, particularly with 8 neonatal IH episodes. ACE-2 is not activated in early postnatal life, and this may contribute to IH-induced vasoconstriction. Therapeutic targeting of ACE and ET-1 may help decrease the risk for kidney injury in the developing neonate to prevent and/or treat neonatal acute kidney injury and/or chronic kidney disease.

Abstract 39: Fate Of Renin Cell Progenitors In The Developing Kidney Vasculature

The unique spatial arregement of the kidney arterioles is an essential event for its development. However, the mechanisms that govern this process are still poorly understood. During nephrogenesis, a group of stromal cells expressing the Forkhead Box D1 ( FoxD1 ) transcription factor (TF) will give rise to the metanephric progenitors for the mural cells of the kidneys arteries and arterioles. We aim to identify the core TFs involved in the cell fate along the differentiaton pathways of the developing kidney vasculature. Therefore, we generated Foxd1-cre; mTmG mice, whose Foxd1 derivative cells are labeled with green fluorescent protein (GFP). GFP+ cells were isolated from 5 (P5) or 30 (P30) days old mice kidneys, and processed either for single-cell RNA-Seq (scRNA-Seq) or for single-cell Assay for Transposase-Accessible Chromatin (scATAC-Seq ). The top5 highly expressed TFs on scRNA-Seq at P5 are: Tcf21, Zeb2, Meis2, Cebpd and Nme3 (p_adjusted_value(padj)= 0, 3.8E-187, 3.9E-180, 4E-172, 4.1E-172 and 3.2E-154, respectively). They are involved in developmental processes and cell proliferation. At P30, the top5 highly expressed TFs are: Atf3, klf2, Fos, Nr4a2 and Junb (padj= 4.2E-294, 2.1E-200, 3.5E-182, 1.7E-52 and 0.2E-24, respectively). They are implicated with calcium-signaling pathway and inflammation. Additionally, scATAC-Seq identifies regions of accessible chromatin for pontential TFs binding, leading to changes in gene expression content and cell identity. At P30, scATAC-Seq showed differential accessible regions with subsequent putative motif enrichment analysis for the TF N4a2 (padj: 4E-297). This is in accordance with our scRNA-Seq results and might play a role in the Foxd1 progenitors cell fate decisions. Our results tracks the fate of the Foxd1+ cells during the kidney vasculature assembly and suggest a new transcription factors network that might play a role to orchestrate cell fate decisions during kidney vascular development.

Resistive index of ophthalmic artery as an imaging biomarker of hypertension-related vascular and kidney damage

Aim: Resistive index of ophthalmic artery (RI-OA) is associated with atherosclerotic diseases. The aim of this study was to evaluate the association of RI-OA and hypertension-related vascular and kidney damage. Materials and methods: Two-hundred and eighty hypertensive patients underwent evaluation of RI-OA, carotid atherosclerosis and level of 24 h albuminuria. Results: Albuminuria and carotid atherosclerosis were positively associated with RI-OA independently of other cardiovascular risk factors. Receiver-operating characteristic curve analysis allowed us to calculate a cut-off value of RI-OA >0.625, which would be suspicious about the existence of atherosclerotic disease. Conclusion: The ophthalmic vascular circulation allows to study connections between macro- and microcirculation in vivo. RI-OA could be a useful marker for a better stratification of the risk of developing kidney and cardiovascular disease.