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Perivascular niches in the kidney comprise heterogeneous cell populations, including pericytes and fibroblasts, with distinct functions. These perivascular cells have crucial roles in preserving kidney homeostasis as they maintain microvascular networks by stabilizing the vasculature and regulating capillary constriction. A subset of kidney perivascular cells can also produce and secrete erythropoietin; this ability can be enhanced with hypoxia-inducible factor-prolyl hydroxylase inhibitors, which are used to treat anaemia in chronic kidney disease. In the pathophysiological state, kidney perivascular cells contribute to the progression of kidney fibrosis, partly via transdifferentiation into myofibroblasts. Moreover, perivascular cells are now recognized as major innate immune sentinels in the kidney that produce pro-inflammatory cytokines and chemokines following injury. These mediators promote immune cell infiltration, leading to persistent inflammation and progression of kidney fibrosis. The crosstalk between perivascular cells and tubular epithelial, immune and endothelial cells is therefore a key process in physiological and pathophysiological states. Here, we examine the multiple roles of kidney perivascular cells in health and disease, focusing on the latest advances in this field of research. Perivascular cells have beneficial roles that maintain kidney homeostasis but can also contribute to kidney pathology. Here, the authors focus mainly on pericytes and fibroblasts to examine these roles, including the contribution of perivascular cells to the myofibroblast pool in kidney fibrosis, and their crosstalk with tubular, immune and endothelial cells. Key points: Perivascular niches in the kidney comprise heterogeneous cell populations, including pericytes and fibroblasts, with distinct functions. These perivascular cells have crucial roles in maintaining homeostasis in the kidney. Pericytes maintain microvascular networks by stabilizing the vasculature and modulating the constriction of capillaries. In pathological states, such as ischaemia–reperfusion, pericytes contribute to the 'no-reflow' phenomenon. A subset of kidney perivascular cells can produce and secrete erythropoietin; hypoxia-inducible factor-prolyl hydroxylase inhibitors can boost this secretion and are used for the treatment of anaemia in chronic kidney disease. Perivascular cells or platelet-derived growth factor receptor-β+ (PDGFRβ+) pericytes synthesize and secrete various intracellular complement proteins and contribute to expression of collagen and extracellular matrix observed during the development of kidney fibrosis. In pathophysiological states, kidney perivascular cells contribute to the progression of kidney fibrosis, partly by transdifferentiating into myofibroblasts. Perivascular cells are major innate immune sentinels in the kidney and produce pro-inflammatory cytokines and chemokines after injury; these mediators promote immune cell infiltration, leading to persistent inflammation and progression of kidney fibrosis. [ABSTRACT FROM AUTHOR]

Neural pathways regulate immunity and inflammation via the inflammatory reflex and specific molecular targets can be modulated by stimulating neurons. Neuroimmunomodulation by nonpharmacological methods is emerging as a novel therapeutic strategy for inflammatory diseases, including kidney diseases and hypertension. Electrical stimulation of vagus neurons or treatment with pulsed ultrasound activates the cholinergic anti-inflammatory pathway (CAP) and protects mice from acute kidney injury (AKI). Direct innervation of the kidney, by afferent and efferent neurons, might have a role in modulating and responding to inflammation in various diseases, either locally or by providing feedback to regions of the central nervous system that are important in the inflammatory reflex pathway. Increased sympathetic drive to the kidney has a role in the pathogenesis of hypertension, and selective modulation of neuroimmune interactions in the kidney could potentially be more effective for lowering blood pressure and treating inflammatory kidney diseases than renal denervation. Use of optogenetic tools for selective stimulation of specific neurons has enabled the identification of neural circuits in the brain that modulate kidney function via activation of the CAP. In this Review we discuss evidence for a role of neural circuits in the control of renal inflammation as well as the therapeutic potential of targeting these circuits in the settings of AKI, kidney fibrosis and hypertension. [ABSTRACT FROM AUTHOR]

Early diagnosis has been the 'Achilles heel' of acute kidney injury (AKI) that has prevented successful implementation of treatment strategies. To date, pharmacological intervention has been largely unsuccessful or equivocal, and morbidity and mortality associated with AKI have remained unacceptably high. Despite their well-known limitations, the most widely used biomarkers for the early diagnosis of AKI are serum creatinine, blood urea nitrogen and urine output. Development of new biomarkers is imperative. A variety of methods have been employed to discover new biomarkers of AKI, including transcriptomics, proteomics, gene arrays, lipidomics and imaging technologies. Clinical trials are underway to establish the validity of the biomarkers discovered using these techniques. This Review summarizes the importance of biomarkers of AKI, from their discovery to clinical practice, from the current perspective and that of what to expect in the future. Great strides forward are being made in breaking down important barriers to the successful prevention and treatment of this devastating disorder. [ABSTRACT FROM AUTHOR]