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      Renal Bioengineering with Scaffolds Generated from Human Kidneys

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          Background: In 2012, about 16,487 people received kidney transplants in the USA whereas 95,022 candidates were on the waiting list at the end of the year. Moreover, more than 2,600 kidneys procured annually for transplantation are discarded for a variety of reasons. We hypothesize that this pool of discarded kidneys could in part meet the growing, urgent need for transplantable kidneys using current methods for organ bioengineering and regeneration and surgical transplantation. The recellularization of extracellular matrix (ECM) scaffolds has the potential to meet the uniquely ambitious engineering challenges posed by complex solid organs such as the kidney. Summary: Attempts to manufacture and implant simpler, hollow structures such as bladders, vessels, urethras, and segments of the upper airways have been successful in the short and mid terms. However, the bioengineering of complex solid organs such as the kidney is a more challenging task that requires a different approach. In previous studies, we showed that decellularized porcine kidneys yield renal ECM scaffolds that preserve their basic architecture and structural components, support cell growth in vivo and in vitro, and maintain a patent vasculature capable of sustaining physiological blood pressure. In a subsequent report, using the same methods, we found that detergent-based decellularization of discarded human renal kidneys preserved their innate ECM framework, biochemical properties, and angiogenic capacity and - importantly - a patent vascular network. Furthermore, the process resulted in the clearance of immunogenic antigens, which has monumental implications for clinical outcomes in the long term in terms of graft rejection. Consequently, these kidneys show promise in bioengineering and transplantation. We refer to this avenue of research and development as ‘cell-scaffold technology'. Key Messages: In 2011, more than 4,700 patients died while on the waiting list for a kidney transplant. In this context, we believe that cell-scaffold technology has the potential to form a bridge between regenerative medicine and transplantation surgery. These methods, in theory, could provide a potentially inexhaustible source of transplantable organs. Unfortunately, current investigations are still in their very early stages and clinical translation is not immediately available in the short term. Thus, identifying the most important obstacles confronting cell-scaffold technology and focusing research efforts in this direction will be important for advancing the state of the art and meeting the clinical needs. We believe that cell-scaffold technology research and development would benefit greatly from a deeper understanding of the physiological mechanisms underlying the natural organogenesis, regeneration, and repair that characterize embryonic humans and simpler organisms. Furthermore, the importance of vascularization - the fundamental caveat of modern surgery - cannot be overstated, especially when discussing the implantation of de novo organs.

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          Most cited references 18

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          Whole-organ tissue engineering: decellularization and recellularization of three-dimensional matrix scaffolds.

          The definitive treatment for end-stage organ failure is orthotopic transplantation. However, the demand for transplantation far exceeds the number of available donor organs. A promising tissue-engineering/regenerative-medicine approach for functional organ replacement has emerged in recent years. Decellularization of donor organs such as heart, liver, and lung can provide an acellular, naturally occurring three-dimensional biologic scaffold material that can then be seeded with selected cell populations. Preliminary studies in animal models have provided encouraging results for the proof of concept. However, significant challenges for three-dimensional organ engineering approach remain. This manuscript describes the fundamental concepts of whole-organ engineering, including characterization of the extracellular matrix as a scaffold, methods for decellularization of vascular organs, potential cells to reseed such a scaffold, techniques for the recellularization process and important aspects regarding bioreactor design to support this approach. Critical challenges and future directions are also discussed.
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            Regeneration and Experimental Orthotopic Transplantation of a Bioengineered Kidney

            Over 100,000 individuals in the United States currently await kidney transplantation, while 400,000 individuals live with end-stage kidney disease requiring hemodialysis. The creation of a transplantable graft to permanently replace kidney function would address donor organ shortage and the morbidity associated with immunosuppression. Such a bioengineered graft must have the kidney’s architecture and function, and permit perfusion, filtration, secretion, absorption, and drainage of urine. We decellularized rat, porcine, and human kidneys by detergent perfusion, yielding acellular scaffolds with vascular, cortical and medullary architecture, collecting system and ureters. To regenerate functional tissue, we seeded rat kidney scaffolds with epithelial and endothelial cells, then perfused these cell-seeded constructs in a whole organ bioreactor. The resulting grafts produced rudimentary urine in vitro when perfused via their intrinsic vascular bed. When transplanted in orthotopic position in rat, the grafts were perfused by the recipient’s circulation, and produced urine via the ureteral conduit in vivo.
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              Mechanisms of progression and regression of renal lesions of chronic nephropathies and diabetes.

              The incidence of chronic kidney diseases is increasing worldwide, and these conditions are emerging as a major public health problem. While genetic factors contribute to susceptibility and progression of renal disease, proteinuria has been claimed as an independent predictor of outcome. Reduction of urinary protein levels by various medications and a low-protein diet limits renal function decline in individuals with nondiabetic and diabetic nephropathies to the point that remission of the disease and regression of renal lesions have been observed in experimental animals and even in humans. In animal models, regression of glomerular structural changes is associated with remodeling of the glomerular architecture. Instrumental to this discovery were 3D reconstruction studies of the glomerular capillary tuft, which allowed the quantification of sclerosis volume reduction and capillary regeneration upon treatment. Regeneration of capillary segments might result from the contribution of resident cells, but progenitor cells of renal or extrarenal origin may also have a role. This review describes recent advances in our understanding of the mechanisms and mediators underlying renal tissue repair ultimately responsible for regression of renal injury.

                Author and article information

                Nephron Exp Nephrol
                Cardiorenal Medicine
                S. Karger AG
                May 2014
                19 May 2014
                : 126
                : 2
                : 119-124
                aWake Forest School of Medicine, Winston-Salem, N.C., USA; bGeneral Surgery, Fondazione IRCCS Policlinico San Matteo Pavia and University of Pavia, Pavia, Italy
                Author notes
                *Giuseppe Orlando, MD, PhD, Wake Forest School of Medicine, Winston-Salem, NC 27157 (USA), E-Mail
                360684 Nephron Exp Nephrol 2014;126:119-124
                © 2014 S. Karger AG, Basel

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                Page count
                Figures: 2, Pages: 6
                Further Section

                Cardiovascular Medicine, Nephrology

                Scaffolds, Kidney, Renal bioengineering


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