Although this description of a model system for cell differentation and organogenesis emphasizes the mammalian kidney, detailed coverage is also given to the development of the transient excretory organs.

Today, more than 900,000 patients in the United States live with end-stage renal disease, with many more suffer from poor renal regeneration. Current methods commonly use synthetic tissue-engineered constructs to deliver cells, drugs, or as scaffolds for reconstruction of injured tissues. However, these constructs usually lack vascularization in vivo, and have poor nutrient diffusion abilities that limit their effectiveness. On the other hand, we have found that extracellular matrix (ECM) hydrogels can be used as scaffolds to facilitate the repair and reconstruction of various tissues. The objective of this study is to fabricate and characterize the mechanics and cell response in vitro of ECM hydrogels prepared from decellularized human kidney tissues. Our preliminary data indicate that Sodium dodecyl sulfate (SDS) decellularization of human kidney tissue sections gives the most optimal results in terms of cellular material removal and ECM structure preservation; decellularized human kidney ECM, when mixed with collagen gel on a 1:1 ratio, shows similar mechanical properties as commonly used type I collagen gel. These data suggest that decellularized human kidney ECM hydrogels are able to provide the structural support necessary for cellular activities. Given these findings and the fact that ECM hydrogels are derived from naturally occurring kidney materials, I hypothesize that decellularized human kidney ECM hydrogel is able to not only provide structural support for cell growth and proliferation, but also to enhance bioactivity and vascularization. To test this hypothesis, I performed angiogenesis and tubulogenesis studies by seeding human umbilical vein endothelial cells and human kidney microvascular endothelial cells onto or in the decellularized human kidney ECM hydrogel as well as type I collagen gel.

Regenerative approaches for congenital and acquired kidney disease have the potential to repair and restore critical cell populations, renal structures, and ultimately function of damaged kidneys. The overriding objective of the studies described in this dissertation was the development, characterization, and recellularization of a three-dimensional (3D) scaffold from rhesus monkey kidneys from different age groups. This was accomplished by optimization of decellularization methods for monkey kidney transverse sections followed by characterization of extracellular matrix (ECM) proteins and biomechanical properties. It was shown that decellularized kidney scaffolds retain expression of major ECM proteins, do not contain residual cell nuclei, and show alterations in biomechanical properties as a result of the decellularization process. Age-related differences in decellularization rate and recellularization capacity using kidney explant culture were assessed. It was found that scaffolds and renal cells from younger donors provided the best outcomes in terms of recellularization potential under the culture conditions described. Recellularization was further explored by utilizing fetal renal glomerular and tubular fractions, which demonstrated that the renal tubular fraction was more effective in recellularizing tubular structures than the glomerular fraction for recellularizing glomerular structures. Proteomics analysis of decellularized kidney scaffolds revealed the presence of several non-ECM proteins. The tissue specificity of kidney and lung scaffolds were compared and showed that the decellularized scaffolds have the ability to spatially organize cells into tissue-specific structures but do not drive tissue-specific gene expression. Lastly, recellularization of kidney scaffolds using NIH-approved human embryonic stem cells (hESC) and a dynamic culture system resulted in the generation of renal constructs that contained tubules with enzymatic activity. The research addressed in this dissertation provides key approaches to using decellularized kidney scaffolds to answer meaningful questions regarding age-related differences, tissue specificity, and tissue engineering strategies for generation of renal constructs for potential regenerative strategies.