Background and objectives: Black patients have a higher incidence of kidney failure but lower rate of deceased- and living-donor kidney transplantation compared with White patients, even after taking differences in comorbidities into account. We assessed whether social determinants of health (e.g., demographics, cultural, psychosocial, knowledge factors) could account for race differences in receiving deceased- and living-donor kidney transplantation. Design, setting, participants, & measurements: Via medical record review, we prospectively followed 1056 patients referred for kidney transplant (2010–2012), who completed an interview soon after kidney transplant evaluation, until their kidney transplant. We used multivariable competing risk models to estimate the cumulative incidence of receipt of any kidney transplant, deceased-donor transplant, or living-donor transplant, and the factors associated with each outcome. Results: Even after accounting for social determinants of health, Black patients had a lower likelihood of kidney transplant (subdistribution hazard ratio, 0.74; 95% confidence interval, 0.55 to 0.99) and living-donor transplant (subdistribution hazard ratio, 0.49; 95% confidence interval, 0.26 to 0.95), but not deceased-donor transplant (subdistribution hazard ratio, 0.92; 95% confidence interval, 0.67 to 1.26). Black race, older age, lower income, public insurance, more comorbidities, being transplanted before changes to the Kidney Allocation System, greater religiosity, less social support, less transplant knowledge, and fewer learning activities were each associated with a lower probability of any kidney transplant. Older age, more comorbidities, being transplanted before changes to the Kidney Allocation System, greater religiosity, less social support, and fewer learning activities were each associated with a lower probability of deceased-donor transplant. Black race, older age, lower income, public insurance, higher body mass index, dialysis before kidney transplant, not presenting with a potential living donor, religious objection to living-donor transplant, and less transplant knowledge were each associated with a lower probability of living-donor transplant. Conclusions: Race and social determinants of health are associated with the likelihood of undergoing kidney transplant.

Cilia are microtubule-based organelles that project from the cell surface. In humans and other vertebrates, possession of a single cilium structure enables an assortment of cellular processes ranging from mechanosensation to fluid propulsion and locomotion. Interestingly, cells can possess a single cilium or many more, where so-called multiciliated cells (MCCs) possess apical membrane complexes with several dozen or even hundreds of motile cilia that beat in a coordinated fashion. Development of MCCs is, therefore, integral to control fluid flow and/or cellular movement in various physiological processes. As such, MCC dysfunction is associated with numerous pathological states. Understanding MCC ontogeny can be used to address congenital birth defects as well as acquired disease conditions. Today, researchers used both in vitro and in vivo experimental models to address our knowledge gaps about MCC specification and differentiation. In this review, we summarize recent discoveries from our lab and others that have illuminated new insights regarding the genetic pathways that direct MCC ontogeny in the embryonic kidney using the power of the zebrafish animal model.

Knowledge about the genetic pathways that control nephron development is essential for better understanding the basis of congenital malformations of the kidney. The transcription factors Osr1 and Hand2 are known to exert antagonistic influences to balance kidney specification. Here, we performed a forward genetic screen to identify nephrogenesis regulators, where whole genome sequencing identified an osr1 lesion in the novel oceanside (ocn) mutant. The characterization of the mutant revealed that osr1 is needed to specify not renal progenitors but rather their maintenance. Additionally, osr1 promotes the expression of wnt2ba in the intermediate mesoderm (IM) and later the podocyte lineage. wnt2ba deficiency reduced podocytes, where overexpression of wnt2ba was sufficient to rescue podocytes and osr1 deficiency. Antagonism between osr1 and hand2 mediates podocyte development specifically by controlling wnt2ba expression. These studies reveal new insights about the roles of Osr1 in promoting renal progenitor survival and lineage choice.

Despite significant advances in understanding nephron segment patterning, many questions remain about the underlying genes and signaling pathways that orchestrate renal progenitor cell fate choices and regulate differentiation. In an effort to identify elusive regulators of nephron segmentation, our lab conducted a high-throughput drug screen using a bioactive chemical library and developing zebrafish, which are a conserved vertebrate model and particularly conducive to large-scale screening approaches. 17β-estradiol (E2), which is the dominant form of estrogen in vertebrates, was a particularly interesting hit from this screen. E2 has been extensively studied in the context of gonad development, but roles for E2 in nephron development were unknown. Here, we report that exogenous estrogen treatments affect distal tubule composition, namely, causing an increase in the distal early segment and a decrease in the neighboring distal late. These changes were noted early in development but were not due to changes in cell dynamics. Interestingly, exposure to the xenoestrogens ethinylestradiol and genistein yielded the same changes in distal segments. Further, upon treatment with an estrogen receptor 2 (Esr2) antagonist, PHTPP, we observed the opposite phenotypes. Similarly, genetic deficiency of the Esr2 analog, esr2b, revealed phenotypes consistent with that of PHTPP treatment. Inhibition of E2 signaling also resulted in decreased expression of essential distal transcription factors, irx3b and its target irx1a. These data suggest that estrogenic compounds are essential for distal segment fate during nephrogenesis in the zebrafish pronephros and expand our fundamental understanding of hormone function during kidney organogenesis.

The ability of the adult zebrafish to replace damaged nephrons in the kidney depends on renal progenitor cells and renal interstitial cells working closely together.