Postnatal development of the renal medulla; role of the renin-angiotensin system

Adverse events during foetal development can predispose the individual for cardiovascular disease later in life, a correlation known as foetal programming of adult hypertension. The 'programming' events have been associated with the kidneys due to the significant role in extracellular volume control and long-term blood pressure regulation. Previously, nephron endowment and functional consequences of a low nephron number have been extensively investigated without achieving a full explanation of the underlying pathophysiological mechanisms. In this review, we will focus on mechanisms of postnatal development in the renal medulla with regard to the programming effects. The renin-angiotensin system is critically involved in mammalian kidney development and impaired signalling gives rise to developmental renal lesions that have been associated with hypertension later in life. A consistent finding in both experimental animal models and in human case reports is atrophy of the renal medulla with developmental lesions to both medullary nephron segments and vascular development with concomitant functional disturbances reaching into adulthood. A review of current knowledge of the role of the renin-angiotensin system for renal medullary development will be given.