Kidney stem cells found in adult zebrafish

Disruption of the lipolysis pathway results in stem cell death through a sterile immunity-like pathway in adult Drosophila

We previously showed that the Arf1-mediated lipolysis pathway sustains stem cells and cancer stem cells (CSCs); its ablation resulted in necrosis of stem cells and CSCs, which further triggers a systemic antitumor immune response. Here we show that knocking down Arf1 in intestinal stem cells (ISCs) causes metabolic stress, which promotes the expression and translocation of ISC-produced damage-associated molecular patterns (DAMPs; Pretaporter [Prtp] and calreticulin [Calr]). DAMPs regulate macroglobulin complement-related (Mcr) expression and secretion. The secreted Mcr influences the expression and localization of enterocyte (EC)-produced Draper (Drpr) and LRP1 receptors (pattern recognition receptors [PRRs]) to activate autophagy in ECs for ATP production. The secreted ATP possibly feeds back to kill ISCs by activating inflammasome-like pyroptosis. We identify an evolutionarily conserved pathway that sustains stem cells and CSCs, and its ablation results in an immunogenic cascade that promotes death of stem cells and CSCs as well as antitumor immunity.

Aggarwal et al. show that disruption of Arf1-mediated lipolysis results in stem cell death through a sterile immunity-like pathway in adult Drosophila. They identify an evolutionarily conserved pathway that specifically sustains stem cells and cancer stem cells (CSCs), and its ablation results in an immunogenic cascade that promotes death of stem cells and CSCs as well as antitumor immunity.

Regenerating the kidney using human pluripotent stem cells and renal progenitors

INTRODUCTION

Chronic kidney disease is a major health-care problem worldwide and its cost is becoming no longer affordable. Indeed, restoring damaged renal structures or building a new kidney represents an ambitious and ideal alternative to renal replacement therapy. Streams of research have explored the possible application of pluripotent stem cells (SCs) (embryonic SCs and induced pluripotent SCs) in different strategies aimed at regenerate functioning nephrons and at understanding the mechanisms of kidney regeneration.

AREAS COVERED

In this review, we will focus on the main potential applications of human pluripotent SCs to kidney regeneration, including those leading to rebuilding new kidneys or part of them (organoids, scaffolds, biological microdevices) as well as those aimed at understanding the pathophysiological mechanisms of renal disease and regenerative processes (modeling of kidney disease, genome editing). Moreover, we will discuss the role of endogenous renal progenitors cells in order to understand and promote kidney regeneration, as an attractive alternative to pluripotent SCs.

EXPERT OPINION

Opportunities and pitfalls of all these strategies will be underlined, finally leading to the conclusion that a deeper knowledge of the biology of pluripotent SCs is mandatory, in order to allow us to hypothesize their clinical application.

Renal progenitors: an evolutionary conserved strategy for kidney regeneration

Following kidney injury, repair can result in functional tissue becoming a patch of cells and disorganized extracellular matrix--a scar--or it can recapitulate the original tissue architecture through the process of regeneration. Regeneration can potentially occur in all animal species and humans. Indeed, the repair of portions of the existing nephron after tubular damage, a response that has been designated classically as cellular regeneration, is conserved in all animal species from the ancestral phases of evolution. By contrast, another type of regenerative response--nephron neogenesis--has been described in lower branches of the animal kingdom, but does not occur in adult mammals. Converging evidence suggests that a renal progenitor system is present in the adult kidney across different stages of evolution, with renal progenitors having been identified as the main drivers of kidney regenerative responses in fish, insects, rodents and humans. In this Review, we describe similarities and differences between the renal progenitor systems through evolution, and propose explanations for how progressive kidney adaptation to environmental changes both required and permitted neonephrogenesis to be given up and for cellular regeneration to be retained as the main regenerative strategy. Understanding the mechanisms that drive renal progenitor growth and differentiation represent the key step for modulating this potential for therapeutic purposes.