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Osteogenesis of renal tubular epithelial cells (RTEC) is an important trigger for calcium oxalate (CaOx) kidney stone formation, but whether macrophages are involved in RTEC osteogenesis is unclear. The purpose of this study was to investigate the role and mechanism of macrophages in CaOx kidney stones on RTEC osteogenesis. Oxalate or ethylene glycol was used to construct in vitro and in vivo CaOx kidney stone models, respectively. Macrophage-derived conditioned medium was used to induce osteogenesis in HK-2 cells, and genetic controls and pharmacological interventions were used to investigate the underlying mechanism. The results demonstrated that macrophage-conditioned medium under oxalate intervention facilitated the increase of alkaline phosphatase and calcium salts as well as the upregulation of osteogenic marker genes (BMP2 and RUNX2) expression in HK-2 cells. On the one hand, the knockdown of the JAK2 gene in HK-2 cells reverses the role of macrophage-derived conditioned medium in promoting osteogenesis in HK-2 cells. On the other hand, inhibition of prostaglandin E2 (PGE2) generation in macrophages reverses osteogenesis in HK-2 cells. Moreover, inhibition of PGE2 generation would cure ethylene glycol-induced renal injury and calcium salt deposition, as well as osteogenesis of RTEC. This study illustrates that in the presence of oxalate, macrophages secret PGE2 to activate JAK2/STAT3 signaling in RTEC, which could trigger osteogenesis. It provides new insights into the mechanism of CaOx kidney stone formation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier Inc. All rights reserved.)

Oxalate-induced damage to renal tubular epithelial cells (RTECs) is an essential factor in the incident kidney stone, but the specific mechanism is unclear. Recent research has pinpointed interacting areas within the endoplasmic reticulum and mitochondria, called mitochondria-associated membranes (MAMs). These studies have linked endoplasmic reticulum stress (ERS) and oxidative imbalance to kidney disease development. The sigma-1 receptor (S1R), a specific protein found in MAMs, is involved in various physiological processes, but its role in oxalate-induced kidney stone formation remains unclear. In this study, we established cellular and rat models of oxalate-induced kidney stone formation to elucidate the S1R's effects against ERS and apoptosis and its mechanism in oxalate-induced RTEC injury. We found that oxalate downregulated S1R expression in RTECs and escalated oxidative stress and ERS, culminating in increased apoptosis. The S1R agonist dimemorfan up-regulated S1R expression and mitigated ERS and oxidative stress, thereby reducing apoptosis. This protective effect was mediated through S1R inhibition of the CHOP pathway. Animal experiments demonstrated that S1R's activation attenuated oxalate-induced kidney injury and alleviated kidney stone formation. This is the first study to establish the connection between S1R and kidney stones, suggesting S1R's protective role in inhibiting ERS-mediated apoptosis to ameliorate kidney stone formation.

Renal tubular epithelial cell damage is the basis for the formation of kidney stones. Oxalate can induce human proximal tubular (HK-2) cells to undergo autophagy and ferroptosis. The present study was aimed at investigating whether the ferroptosis of HK-2 cells induced by oxalate is caused by the excessive activation of autophagy. We treated HK-2 cells with 2 mmol/L of oxalate to establish a kidney stone model. First, we tested the degree of oxidative damage and the level of autophagy and ferroptosis in the control group and the oxalate intervention group. We then knocked down and overexpressed the BECN1 gene and knocked down the NCOA4 gene in HK-2 cells, followed by redetection of the above indicators. We confirmed that oxalate could induce autophagy and ferroptosis in HK-2 cells. Moreover, after oxalate treatment, overexpression of the BENC1 gene increased cell oxidative damage and ferroptosis. In addition, knockdown of NCOA4 reversed the effect of oxalate-induced ferroptosis in HK-2 cells. Our results show that the effects of oxalate on the ferroptosis of HK-2 cells are caused by the activation of autophagy, and knockdown of the NCOA4 could ameliorate this effect., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2021 Qianlin Song et al.)

Injury to the renal tubular epithelium has emerged as a leading factor underlying the formation of kidney stones. Indeed, epithelial cell damage contributes to the adherence and aggregation of crystals, thereby accelerating the formation of renal stones. Meanwhile, exosomes play an instrumental role in cellular communication, including DNA, RNA, mRNA, etc. In this study, homogenous cells were treated with exosomes derived from damaged cells in an attempt to establish "positive feedback" of cell damage, and the desired results were achieved. To begin, a serum-free medium and supersaturated concentrations of oxalate were added to the HK-2 cell line, and then exosomes were isolated from the two groups for analysis and comparison, and the autophagy-related gene Ambra1 (autophagy and beclin-1 regulator 1) was detected. Subsequently, normal HK-2 cells were treated with exosomes, and the related indexes of autophagy, ferroptosis and mitophagy were determined. Thereafter, Ambra1 was knocked down in exosome-derived HK-2 cells, resulting in the down-regulation of Ambra1 expression in exosomes produced by HK-2 cells following oxalate intervention. Thereafter, the ability of exosomes to stimulate autophagy, mitophagy and ferroptosis was re-evaluated in HK-2 cells after Ambra1 knockdown. The results corroborated that exosomes secreted by oxalate-treated HK-2 can directly elevate autophagy, ferroptosis and mitophagy levels in normal cells, and this effect was significantly mitigated following Ambra1 knockdown within exosomes. Meanwhile, exosomes-induced autophagy and ferroptosis were alleviated after knockdown of beclin-1 in recipient HK-2 cells. These results further suggest that beclin-1 plays a critical role in the process of exosome-induced autophagy-ferroptosis. • Exosomes secreted by HK-2 cells damaged by supersaturated oxalate can be ingested by normal cells and cause damage to them. • Normal cell damage is caused by excessive mitophagy, autophagy and ferroptosis. • Ambra1 is the key gene in this phenomenon. [ABSTRACT FROM AUTHOR]

Abstract: Background: Clinically, using ileal conduit for urinary diversion often caused many serious complications. Tissue engineering technology may offer an alternative method for urinary diversion after radical cystectomy. In this study, we aimed to make a tissue-engineered tubular graft (TETG) using bladder epithelial cells and bladder acellular matrix (BAM) for urinary diversion in rabbits. Methods: Bladder epithelial cells of rabbit were cultivated and expanded in vitro, which were then seeded on BAM and cultured for 7 d. Then, cell-seeded grafts of 4 cm length and 0.8 cm diameter were used to make TETGs and transferred into the omentum for 2 wk before urinary diversion. In the experimental group, bladders of the rabbits were removed. The proximal ends of TETGs were anastomosed with ureters, and the distal ends were anastomosed with the abdominal stomas. In the control group, TETGs were constructed using unseeded BAM. Newly formed tissue structures were functionally and microscopically evaluated using urography and immunohistochemistry at 1, 2, 4, and 8 wk after operation, respectively. Histologic examination with hematoxylin and eosin staining was conducted to assess tissue regeneration. Immunohistochemistry was performed with AE1/AE3, uroplakin Ⅲa, and zonula occludens 1 (ZO-1) antibodies. Results: All animals were alive in the experimental group. Hematoxylin and eosin staining showed epithelial coverage in TETG. Immunohistochemistry showed positive stain with AE1/AE3, uroplakin Ⅲa, and ZO-1, which indicated mature and functional epithelial cells on the lumen of TETG. Intravenous urography showed that there were no obstructions in TETGs. In the control group, four rabbits were dead within 2 wk, and scar formation, atresia, and severe hydronephrosis were found. Conclusions: It was feasible that TETG constructed using bladder epithelial cells and BAM for urinary diversion after radical cystectomy in rabbits. [Copyright &y& Elsevier]