From human pluripotent stem cells to functional kidney organoids and models of renal disease
In health, the mature human kidney contains on average 1.4 million nephrons (1). Each of these epithelial tubes begins in the cortex of the organ with a glomerulus that ultrafilters blood, clearing water and small molecules but retaining large proteins and blood cells. The two kidneys receive around 20% of the cardiac output, a high pressure and high volume arterial flow needed to generate daily the 200 litres of ultrafiltrate. The nephron tubule segments modify this ultrafiltrate, for example reclaiming some sodium and water. The nascent urine then flows into collecting ducts that executes concentration and further acidification. The branched collecting ducts converge towards the papilla where urine, around one to two litres a day, enters the renal pelvis and then the ureters, in which it is propelled towards the urinary bladder by peristaltic waves.