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. (C) 2011 Elsevier B.V. All rights reserved

Bioengineering of living renal membranes consisting of hierarchical, bioactive supramolecular meshes and human tubular cells

Maintenance of polarisation of epithelial cells and preservation of their specialized phenotype are great challenges for bioengineering of epithelial tissues Mimicking the basement membrane and underlying extracellular matrix (ECM) with respect to its hierarchical fiber-like morphology and display of bioactive signals is prerequisite for optimal epithelial cell function in vitro We report here on a bottom-up approach based on hydrogen-bonded supramolecular polymers and ECM-peptides to make an electro-spun bioactive supramolecular mesh which can be applied as synthetic basement membrane The supramolecular polymers used self-assembled into nano-meter scale fibers while at micro-meter scale fibers were formed by electro-spinning We introduced bioactivity into these nano-fibers by intercalation of different ECM-peptides designed for stable binding Living kidney membranes were shown to be bioengineered through culture of primary human renal tubular epithelial cells on these bioactive meshes Even after a long-term culturing period of 19 days we found that the cells on bioactive membranes formed tight monolayers while cells on non-active membranes lost their monolayer integrity Furthermore the bioactive membranes helped to support and maintain renal epithelial phenotype and function Thus incorporation of ECM-peptides Into electro-spun meshes via a hierarchical supramolecular method is a promising approach to engineer bioactive synthetic membranes with an unprecedented structure This approach may in future be applied to produce living bioactive membranes for a I:no-artificial kidney (C) 2010 Elsevier Ltd All rights reserve