From kidney development to drug delivery and tissue engineering strategies in renal regenerative medicine.

Deterioration of renal function is typically slow but progressive, and therefore renal disease is often diagnosed in a late stage when already serious complaints occur. Ultimately when renal function has dropped below 10%, renal replacement is required. Renal transplantation provides a long-term solution but due to shortage of donor kidneys most patients receive hemodialysis therapy. Although hemodialysis is an effect method to correct disturbances in water and electrolyte balances in the body, it does not substitute for the important endocrine and metabolic renal functions that are critical for homeostasis. Among these functions are, the renal production of renin which controls blood pressure, the secretion of erythropoietin which stimulates the synthesis of red blood cells, and the excretion of protein bound waste products. As a consequence, many dialysis patients remain in poor health. With the development of regenerative medicine, and particularly tissue engineering and novel drug delivery strategies, alternative routes for renal replacement are emerging. Increasing understanding of (stem) cells, growth factors and regeneration in the kidney has contributed to a whole new view on restoration and reconstruction of (parts of) renal tissue that may be used to improve current renal replacement therapies. Here, an overview of critical interactions between cells, growth factors and extracellular matrix molecules in kidney development and regeneration will be described. Ultimately, we will discuss how these interactions can be translated to strategies for in-vivo regeneration and in-vitro reconstruction of the kidney.