Bioengineering kidneys for transplantation

Early-Phase Clinical Trials of Bio-Artificial Organ Technology: A Systematic Review of Ethical Issues

Regenerative medicine has emerged as a novel alternative solution to organ failure which circumvents the issue of organ shortage. In preclinical research settings bio-artificial organs are being developed. It is anticipated that eventually it will be possible to launch first-in-human transplantation trials to test safety and efficacy in human recipients. In early-phase transplantation trials, however, research participants could be exposed to serious risks, such as toxicity, infections and tumorigenesis. So far, there is no ethical guidance for the safe and responsible design and conduct of early-phase clinical trials of bio-artificial organs. Therefore, research ethics review committees will need to look to related adjacent fields of research, including for example cell-based therapy, for guidance. In this systematic review, we examined the literature on early-phase clinical trials in these adjacent fields and undertook a thematic analysis of relevant ethical points to consider for early-phase clinical trials of transplantable bio-artificial organs. Six themes were identified: cell source, risk-benefit assessment, patient selection, trial design, informed consent, and oversight and accountability. Further empirical research is needed to provide insight in patient perspectives, as this may serve as valuable input in determining the conditions for ethically responsible and acceptable early clinical development of bio-artificial organs.

Human Endothelial Cell Seeding in Partially Decellularized Kidneys

The excessive demand for organ transplants has promoted the development of strategies that increase the supply of immune compatible organs, such as xenotransplantation of genetically modified pig organs and the generation of bioartificial organs. We describe a method for the partial replacement of rat endothelial cells for human endothelial cells in a rat's kidney, obtaining as a final result a rat-human bioartificial kidney. First, in order to maintain parenchymal epithelial cells and selectively eliminate rat endothelial cells, three methods were evaluated in which different solutions were perfused through the renal artery: 0.1% sodium dodecyl sulfate (SDS), 0.01% SDS, and hyperosmolar solutions of sucrose. Then, partially decellularized kidneys were recellularized with human endothelial cells and finally transplanted in an anesthetized rat. The solution of 0.1% SDS achieved the highest vascular decellularization but with high degree of damage in the parenchyma side. On the contrary, 0.01% SDS and hyperosmolar solutions achieved a partial degree of endothelial decellularization. TUNEL assays reveal that hyperosmolar solutions maintained a better epithelial cell viability contrasting with 0.01% SDS. Partially decellularized kidneys were then recellularized with human endothelial cells. Histological analysis showed endothelial cells attached in almost all the vascular bed. Recellularized kidney was transplanted in an anesthetized rat. After surgery, recellularized kidney achieved complete perfusion, and urine was produced for at least 90 min posttransplant. Histological analysis showed endothelial cells attached in almost all the vascular bed. Therefore, endothelial decellularization of grafts and recellularization with human endothelial cells derived from transplant recipients can be a feasible method with the aim to reduce the damage of the grafts.

Optimizing Decellularization Strategies for the Efficient Production of Whole Rat Kidney Scaffolds

BACKGROUND

Renal dysfunction remains a global issue, with chronic kidney disease being the 18th most leading cause of death, worldwide. The increased demands in kidney transplants, led the scientific society to seek alternative strategies, utilizing mostly the tissue engineering approaches. Unlike to perfusion decellularization of kidneys, we proposed alternative decellularization strategies to obtain acellular kidney scaffolds. The aim of this study was the evaluation of two different decellularization approaches for producing kidney bioscaffolds.

METHODS

Rat kidneys from Wistar rats, were submitted to decellularization, followed two different strategies. The decellularization solutions used in both approaches were the same and involved the use of 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate and sodium dodecyl sulfate buffers for 12 h each, followed by incubation in a serum medium. Both approaches involved 3 decellularization cycles. Histological analysis, biochemical and DNA quantification were performed. Cytotoxicity assay and repopulation of acellular kidneys were also applied.

RESULTS

Histological, biochemical and DNA quantification confirmed that the 2nd approach had the best outcome regarding the kidney composition and cell elimination. Acellular kidneys from both approaches were successfully recellularized.

CONCLUSION

Based on the above data, the production of kidney scaffolds with the proposed cost- effective decellularization approaches, was efficient.

Detection of the residual concentration of sodium dodecyl sulfate in the decellularized whole rabbit kidney extracellular matrix

To optimize rabbit kidney decellularization protocol, using sodium dodecyl sulfate (SDS) as a commonly used detergent, a methylene blue based assay was employed for detecting the minimum nontoxic SDS level for future cell seeding. The rabbit kidney tissues were decellularized with the perfusion-based method and underwent several investigations to determine the efficacy of decellularization in preserving the extracellular matrix (ECM) and cell removal. SDS detection was performed by incubating with methylene blue and subsequent extraction with chloroform. MTT (3-(4, 5-dimethylthiazol-2-yr)-2,5-diphenyltetrazolium bromide) assay and SDS release were also evaluated during the entire process. After the first washing cycle, SDS concentration was 0.036, in 500 mL of the washing liquid, which slowly decreased and reached to 0.009 % after at the end of seventh washing cycle. In the 9th cycle, SDS was gradually decreased and reached to 0.003 %. SDS was significantly released after one week of incubation which ceased after ten washing cycles. The results of MTT assay demonstrated that different cells exhibited various sensitivity levels when exposed to serial concentrations of SDS. Human embryonic kidney cells (HEK293) with 0.003 % threshold for cellular toxicity and 87.4 % cell viability were more resistant compared with mesenchymal stem cells with 0.001 % threshold and 85.4 % cell viability. Colorimetric assay with methylene blue is a straightforward and non-invasive method to detect residual SDS present in tissue and can also prevent ECM destruction after several washings for detergent removal from decellularized tissues.

Kidney tissue engineering using a well-preserved acellular rat kidney scaffold and mesenchymal stem cells

The aim of this study was to acquire an effective method for preparation of rat decellularized kidney scaffolds capable of supporting proliferation and differentiation of human adipose tissue derived mesenchymal stem cells (AD-MSCs) into kidney cells. We compared two detergents, the sodium dodecyl sulfate (SDS) and triton X-100 for decellularization. The efficiency of these methods was assessed by Hematoxylin and Eosin (H&E), 4', 6 diamidino-2-phenylindole and immunohistochemistry (IHC) staining. In the next step, AD-MSCs were seeded into the SDS-treated scaffolds and assessed after three weeks of culture. Proliferation and differentiation of AD-MSCs into kidney-specific cell types were then analyzed by H&E and IHC staining. The histological examinations revealed that SDS was more efficient in removing kidney cells at all-time points compared to triton X-100. Also, in the SDS-treated sections the native extracellular matrix was more preserved than the triton-treated samples. Laminin was completely preserved during decellularization procedure using SDS. Cell attachment in the renal scaffold was observed after recellularization. Furthermore, differentiation of AD-MSCs into epithelial and endothelial cells was confirmed by expression of Na-K ATPase and vascular endothelial growth factor receptor 2 (VEGFR-2) in seeded rat renal scaffolds, respectively. Our findings illustrated that SDS was more effective for decellularization of rat kidney compared to triton X-100. We presented an optimized method for decellularization and recellularization of rat kidneys to create functional renal natural scaffolds. These natural scaffolds supported the growth of AD-MSCs and could also induce differentiation of these cells into epithelial and endothelial cells.

Kidney regeneration with biomimetic vascular scaffolds based on vascular corrosion casts

We have developed a biomimetic renal vascular scaffold based on a vascular corrosion casting technique. This study evaluated the feasibility of using this novel biomimetic scaffold for kidney regeneration in a rat kidney cortical defect model. Vascular corrosion casts were prepared from normal rat kidneys by perfusion with 10% polycaprolactone (PCL) solution, followed by tissue digestion. The corrosion PCL cast was coated with collagen, and PCL was removed from within the collagen coating, leaving only a hollow collagen-based biomimetic vascular scaffold. The fabricated scaffolds were pre-vascularized with MS1 endothelial cell coating, incorporated into 3D renal constructs, and subsequently implanted either with or without human renal cells in the renal cortex of nude rats. The implanted collagen-based vascular scaffold was easily identified and integrated into native kidney tissue. The biomimetic vascular scaffold coated with endothelial cells (MS1) showed significantly enhanced vascularization, as compared to the uncoated scaffold and hydrogel only groups (P < 0.001). Along with the improved vascularization effects, the MS1-coated scaffolds showed a significant renal cell infiltration from the neighboring host tissue, as compared to the other groups (P < 0.05). Moreover, addition of human renal cells to the MS1-coated scaffold resulted in further enhancement of vascularization and tubular structure regeneration within the implanted constructs. The biomimetic collagen vascular scaffolds coated with endothelial cells are able to enhance vascularization and facilitate the formation of renal tubules after 14 days when combined with human renal cells. This study shows the feasibility of bioengineering vascularized functional renal tissues for kidney regeneration. STATEMENT OF SIGNIFICANCE: Vascularization is one of the major hurdles affecting the survival and integration of implanted three-dimensional tissue constructs in vivo. A novel, biomimetic, collagen-based vascular scaffold that is structurally identical to native kidney tissue was developed and tested. This biomimetic vascularized scaffold system facilitates the development of new vessels and renal cell viability in vivo when implanted in a partial renal defect. The use of this scaffold system could address the challenges associated with vascularization, and may be an ideal treatment strategy for partial augmentation of renal function in patients with chronic kidney disease.

The use of stem cells in aesthetic dermatology and plastic surgery procedures. A compact review of experimental and clinical applications

The aim of this paper was to collect currently available data related to the use of stem cells in aesthetic dermatology and plastic surgery based on a systemic review of experimental and clinical applications. We found that the use of stem cells is very promising but the current state of art is still not effective. This situation is connected with not fully known mechanisms of cell interactions, possible risks and side effects. We think that there is a big need to create and conduct different studies which could resolve problems of stem cells use for implementation into aesthetic dermatology and plastic surgery.

Mesenchymal Stem Cell-based Therapy as a New Horizon for Kidney Injuries

Today, the prevalence of kidney diseases is increasing around the world, but there has still been no effective medical treatment. The therapeutic choices are confined to supportive cares and preventive strategies. Currently, mesenchymal stem cells (MSCs)-based cell therapy was proposed for the treatment of kidney injuries. However, after the transplantation of MSCs, they are exposed to masses of cytotoxic factors involving an inflammatory cytokine storm, a nutritionally-poor hypoxic environment and oxidative stresses that finally lead to minimize the efficacy of MSCs based cell therapy. Therefore, several innovative strategies were developed in order to potentiate MSCs to withstand the unfavorable microenvironments of the injured kidney tissues and improve their therapeutic potentials. This review aims to introduce MSCs as a new modality in the treatment of renal failure. Here, we discuss the clinical trials of MSCs-based therapy in kidney diseases as well as the in vivo studies dealing with MSCs application in kidney injuries mainly from the proliferation, differentiation, migration and survival points of view. The obstacles and challenges of this new modality in kidney injuries are also discussed.

Bioartificial Kidneys

Purpose of Review

Historically, there have been many advances in the ways in which we treat kidney diseases. In particular, hemodialysis has set the standard for treatment since the early 1960s and continues today as the most common form of treatment for acute, chronic, and end-stage conditions. However, the rising global prevalence of kidney diseases and our limited understanding of their etiologies have placed significant burdens on current clinical management regimens. This has resulted in a desperate need to improve the ways in which we treat the underlying and ensuing causes of kidney diseases for those who are unable to receive transplants.

Recent Findings

One way of possibly addressing these issues is through the use of improved bioartificial kidneys. Bioartificial kidneys provide an extension to conventional artificial kidneys and dialysis systems, by incorporating aspects of living cellular and tissue function, in an attempt to better mimic normal kidneys. Recent advancements in genomic, cellular, and tissue engineering technologies are facilitating the improved design of these systems.

Summary

In this review, we outline various research efforts that have focused on the development of regenerated organs, implantable constructs, and whole bioengineered kidneys, as well as the transitions from conventional dialysis to these novel alternatives. As a result, we envision that these pioneering efforts can one day produce bioartificial renal technologies that can either perform or reintroduce essential function, and thus provide practical options to treat and potentially prevent kidney diseases.

[Renal transplantation in 2046: Future and perspectives]

OBJECTIVES

To report major findings that may build the future of kidney transplantation.

MATERIAL AND METHODS

Relevant publications were identified through Medline (http://www.ncbi.nlm.nih.gov) and Embase (http://www.embase.com) database from 1960 to 2016 using the following keywords, in association, "bio-engineering; heterotransplantation; immunomodulation; kidney; regenerative medicine; xenotransplantation". Articles were selected according to methods, language of publication and relevance. A total of 5621 articles were identified including 2264 for xenotransplantation, 1058 for regenerative medicine and 2299 for immunomodulation; after careful selection, 86 publications were eligible for our review.

RESULTS

Despite genetic constructs, xenotransplantation faces the inevitable obstacle of species barrier. Uncertainty regarding xenograft acceptance by recipients as well as ethical considerations due to the debatable utilization of animal lives, are major limits for its future. Regenerative medicine and tridimensional bioprinting allow successful implantation of organs. Bioengineering, using decellularized tissue matrices or synthetic scaffold, seeded with pluripotent cells and assembled using bioreactors, provide exciting results but remain far for reconstituting renal complexity and vascular patency. Immune tolerance may be achieved through a tough initial T-cell depletion or a combined haplo-identical bone marrow transplant leading to lymphohematopoietic chimerism.

CONCLUSION

Current researches aim to increase the pool of organs available for transplantation (xenotransplants and bio-artificial kidneys) and to increase allograft survival through the induction of immune tolerance. Reported results suggest the onset of a thrilling new era for renal transplantation providing end-stage renal disease-patients with an improved survival and quality of life.

Decellularized scaffolds in regenerative medicine

Allogeneic organ transplantation remains the ultimate solution for end-stage organ failure. Yet, the clinical application is limited by the shortage of donor organs and the need for lifelong immunosuppression, highlighting the importance of developing effective therapeutic strategies. In the field of regenerative medicine, various regenerative technologies have lately been developed using various biomaterials to address these limitations. Decellularized scaffolds, derived mainly from various non-autologous organs, have been proved a regenerative capability in vivo and in vitro and become an emerging treatment approach. However, this regenerative capability varies between scaffolds as a result of the diversity of anatomical structure and cellular composition of organs used for decellularization. Herein, recent advances in scaffolds based on organ regeneration in vivo and in vitro are highlighted along with aspects where further investigations and analyses are needed.

Short term ex vivo storage of kidneys cause progressive nuclear ploidy changes of renal tubular epitheliocytes

In renal transplantation, there has been considerable success, mainly in term of post-transplant graft function. However, upon closer scrutiny, it is known that severe dysfunction, including persistence of renal failure is seen after transplantation. The major condition that potentially cause significant lesion may be hypothesized to be related to the hypothermic approach to storage. To systematically examine these issues, we stored mammalian (sheep) kidneys in UWS at 4 °C for four different time points (0, 1, 3 and 6 hours). We obtained renal histological sections and examined tubular architecture as well as nuclear characteristics of tubular epitheliocytes. The results of our preliminary investigations suggest that there are temporal changes of tubular epitheliocytes, as well as genomic changes. These changes were also seen in tissues stored at room temperature. Our observations suggest the need for additional studies for redesigning of improvised storage solutions. Pilot studies using Celsior also revealed similar kind of nuclear changes, suggesting that storage conditions are contributory, including perfusion versus static conditions. The results may explain persistence of tubular injury several days after orthotopic transplantation, and may potentially be contributory to delayed graft function (DGF).

The potential of the combination of CRISPR/Cas9 and pluripotent stem cells to provide human organs from chimaeric pigs

Clinical organ allotransplantation is limited by the availability of deceased human donors. However, the transplantation of human organs produced in other species would provide an unlimited number of organs. The pig has been identified as the most suitable source of organs for humans as organs of any size would be available. Genome editing by RNA-guided endonucleases, also known as clustered regularly interspaced short palindromic repeat (CRISPR/Cas9), in combination with induced pluripotent stem cells (iPSC), may have the potential to enable the creation of human organs from genetically-modified chimaeric pigs. These could potentially provide an unlimited supply of organs that would not be rejected by the recipient's immune system. However, substantial research is needed to prove that this approach will work. Genetic modification of chimaeric pigs could also provide useful models for developing therapies for various human diseases, especially in relation to drug development.