Podocytes and the quest for precision medicines for kidney diseases.

In this review, I describe a 30-year journey in the quest for precision medicines for patients with kidney diseases. In 1987, when I started my reseach career, most scientists studying glomerular disease biology were focused on mesangial cells. The crucial role of the podocyte in many kidney diseases characterized by proteinuria, including focal segmental glomerulosclerosis (FSGS) and diabetic nephropathy, had not yet been recognized. We were not aware of genetic causes or drivers of kidney diseases nor of molecular markers and cell culture systems for mechanistic studies of podocyte biology. Tools for generating podocyte-specific knockout mice did not exist, and the key role of the podocyte actin cytoskeleton in the pathogenesis of proteinuria had not yet been identified. Clinically, treatment options for proteinuric kidney diseases were empiric, non-specific, and restricted to steroids and cyclosporine, without an understanding of their underlying mechanism of action. Since then, we have come a long way: a host of genetic causes for FSGS affecting podocytes has been identified, and with the advent of next generation sequencing approaches, the number of genetic causes continues to increase. Thinking "outside the box," empowered me to turn my attention to podocytes, develop the first differentiated podocyte cell culture system, and pioneer studies on the critical role of the podocyte actin cytoskeleton. Now, with the advent of iPSCs, we can build on these efforts by generating human podocytes and kidney organoids from patient cells, which, in combination with CRISPR-Cas9 gene editing and big data analyses, represent important next generation tools for bringing urgently needed precision medicines to patients with kidney disease. These new directions in kidney research should also increase the feasibility of much needed clinical trials in the kidney space. From Heidelberg to Boston, it has been an amazing scientific adventure. I will close with my thoughts about the path forward in making precision medicines for kidney diseases a reality.