CircRSPRY1 regulates calcium oxalate crystal-induced necrotic apoptosis in renal tubules via miR-21-5p/PTEN

Circular RNAs (circRNAs) constitute a recently discovered class of evolutionarily conserved and robust regulatory RNAs. Their potential as diagnostic biomarkers and therapeutic targets for various diseases is a subject of growing interest. Nevertheless, the precise regulatory roles and underlying mechanisms of circRNAs in the context of kidney stone formation remain largely unexplored. Utilizing RNA high-throughput sequencing technology and quantitative real-time polymerase chain reaction (qRT-PCR), we conducted a comprehensive screen for calcium oxalate crystals (CaOx)-induced differential expression of circular RNA (circRSPRY1) in the human renal tubular epithelial cells (HK-2) kidney injury model. Subsequently, we employed a combination of RNA and protein expression analyses, luciferase activity assays, and immunohistochemistry (IHC) to elucidate the regulatory role of circRSPRY1 in targeting the miR-21-5p/PTEN axis, influencing the processes of necroptosis and apoptogenesis. In this investigation, we observed a notable downregulation of circRSPRY1 expression in both the CaOx-stimulated HK-2 renal tubular epithelial cell injury model and a glyoxalate-induced mouse model of renal calcinosis. Notably, overexpressing circRSPRY1 led to reduced crystalline deposition in our in vitro model. Mechanistically, circRSPRY1 overexpression was associated with the downregulation of cleaved-caspase-8, p-MLKL, P-RIPK1, and P-PIPK3 levels, consequently inhibiting necrotic apoptosis. Furthermore, circRSPRY1 appeared to act as a miR-21-5p sponge, resulting in reduced miR-21-5p availability for PTEN binding and, subsequently, increased PTEN expression, thus impeding the progression of necrotic apoptosis and kidney injury. Additionally, inhibiting miR-21-5p levels demonstrated the ability to suppress necrotic apoptosis in renal calcinosis by downregulating the PTEN/MLKL pathway. Our findings suggest that circRSPRY1 represents a novel candidate circRNA implicated in the pathogenesis of kidney stones. circRSPRY1 acts as a sponge, sequestering miR-21-5p to modulate PTEN expression, thereby regulating necrotic apoptosis and contributing to the formation of calcium oxalate stones.