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Keywords:

  • endothelialisation;
  • liver perfusion;
  • mesenchymal stem cells;
  • scaffold;
  • surface modification;
  • transplantation

Abstract

  1. Top of page
  2. Abstract
  3. Organ decellularization
  4. Organ recellularization
  5. Organ scaffold transplantation
  6. Critical challenges
  7. Conclusions
  8. Future perspective
  9. Acknowledgements
  10. References

End-stage hepatic failure is a potentially life-threatening condition for which orthotopic liver transplantation (OLT) is the only effective treatment. However, a shortage of available donor organs for transplantation each year results in the death of many patients waiting for liver transplantation. Cell-based therapies and hepatic tissue engineering have been considered as alternatives to liver transplantation. However, primary hepatocyte transplantation has rarely produced therapeutic effects because mature hepatocytes cannot be effectively expanded in vitro, and the availability of hepatocytes is often limited by shortages of donor organs. Decellularization is an attractive technique for scaffold preparation in stem cell-based liver engineering, as the resulting material can potentially retain the liver architecture, native vessel network and specific extracellular matrix (ECM). Thus, the reconstruction of functional and practical liver tissue using decellularized scaffolds becomes possible. This review focuses on the current understanding of liver tissue engineering, whole-organ liver decellularization techniques, cell sources for recellularization and potential clinical applications and challenges.

End-stage hepatic failure is a potentially life-threatening condition for which orthotopic liver transplantation (OLT) is currently the only available and curative therapy. However, the high expense, severe surgical complications, chronic rejection and critical shortage of donor organs limit the wide application of liver transplantation [1, 2]. The development of hepatocyte transplantation for treating end-stage hepatic failure is also limited by shortages in cell supplies and low engraftment efficacy. In addition, safety issues should be taken into serious consideration [3-5]. Bioartificial liver support systems (BALS) can serve as bridges to liver transplantation and have demonstrated some success in clinical applications [6]. However, BALS are not a permanent alternative to liver transplantation. With the rising concept of ‘tissue engineering,’ more researchers have begun concentrating their efforts on the construction of a functional tissue-engineered liver. Recently, many different scaffolds, such as collagen and polyesters, have been used to evaluate their capacity to support cell growth, liver-specific function and repopulation [7-15]. Among the main challenges now facing liver regenerative medicine are the requirements for more complex functionality and functional and biomechanical stability in laboratory-grown tissues transferred for clinical transplantation [16].

Many studies indicate that whole-organ decellularization technology can largely preserve both the native composition and the macroscopic three-dimensional architecture of the liver, ensuring biocompatibility and allowing for extensive recellularization to occur [17]. The blood vessels in the bioscaffold can promote the adhesion and distribution of endothelial cells (ECs), thus allowing neovascularization to occur. The extracellular matrix (ECM), primarily consisting of type I collagen, fibronectin, laminin and a diverse variety of growth factors, provides an important microenvironment necessary to support cell attachment, proliferation and differentiation and also provides appropriate biomechanical support [18]. Furthermore, ECM components can also participate in neovascularization [19]. Evidence shows that the differentiation of human hepatic stem cells into mature hepatocytes is more efficient in decellularized liver scaffolds [20, 21]. Armed with these advantages, decellularized scaffolds, rather than synthetic biomaterial, are attracting more attention in both research and clinical fields and are currently being exploited as scaffolds upon which to build functional liver tissue.

Organ decellularization

  1. Top of page
  2. Abstract
  3. Organ decellularization
  4. Organ recellularization
  5. Organ scaffold transplantation
  6. Critical challenges
  7. Conclusions
  8. Future perspective
  9. Acknowledgements
  10. References

The preparation of a three-dimensional scaffold from an intact organ requires removing all of the cells without adversely affecting its composition, biological activity or mechanical integrity by exposing the organ parenchymal cells to detergents, proteases or chemicals through the native vasculature. The decellularization technology has already been extensively applied to many other organs, such as the lung [22, 23], kidney [24, 25] and heart [26]. However, many studies indicate that the decellularization agents can inevitably damage the ECM materials, resulting in denaturation of the ECM materials and disruption of the ultrastructure [27]. Therefore, at this time, minimizing the damage the agents cause to the bioscaffolds is our utmost goal.

To optimize the decellularization procedure, many factors need to be taken into consideration, including the agents, the tissue characteristics and the decellularization technique. Among the numerous decellularization techniques [28-31], perfusion decellularization is the best choice for the construction of whole-liver scaffolds. By perfusing through vessels, the decellularizing agents can be easily transfer to cells and deliver cellular materials from the tissue. The liver is a thick organ, and some agents, such as enzymes, osmotic solutions and the zwitterionic detergent 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS), may be ineffective for decellularization [32]. Triton X-100 is a potent detergent that can effectively remove cell residues; however, the decellularized liver scaffold still retains traces of nuclear material when this detergent is used [33]. Sodium dodecyl sulphate (SDS) appears to be more effective than Triton X-100 for removing nuclei from dense tissues and organs. The addition of SDS can achieve a better decellularization but inevitably results in ultrastructure disruption [34] and growth factor elimination [35]. Based on the above studies, a combination of SDS and Triton X-100 was applied to the decellularization procedure [36-38], and the analysis of the scaffold revealed absence of cell materials and the preservation of major ECM components and ultrastructure. Apart from the methods stated above, a combination of enzymatic, detergent and mechanical methods was employed for liver decellularization [36-39]. Though this combination resulted in less ECM disruption, the procedure was time-consuming. In addition to the above factors that affect decellularization, the cytotoxicity of the residual agents after decellularization is also a critical issue for further clinical usage [40]. Thus, care must be taken to flush residual agents from the ECM after decellularization, particularly detergents such as SDS that penetrate into thick or dense tissues. Even thin tissues such as valve leaflets require multiple (more than six) agitated washes to completely remove detergents.

Currently, decellularization technology is mostly limited to small animals, such as rats, mice, ferrets or rabbits [18, 39, 41]. For future clinical applications, larger animal models (such as a porcine model) need to be decellularized to confirm potential therapeutic efficiency. The porcine liver scaffold was initially produced by decellularizing with SDS alone for 16 h at approximately 100 ml/min, which preserved the major organ architecture essential for organ function, viability and constructive host responses [42]. The biocompatibility of the scaffold was confirmed by the conclusion that the transplanted cells showed good expression of albumin and urea metabolism and demonstrated good viability at 45 days in culture [43]. Even so, better decellularization methods need to be employed to improve the decellularization efficiency.

With the number of studies undertaken, the technology behind decellularization is maturing. A bioscaffold derived from the whole-liver organ with minimal loss of matrix components will inevitably gain an upper hand in the development of whole-liver tissue engineering.

Organ recellularization

  1. Top of page
  2. Abstract
  3. Organ decellularization
  4. Organ recellularization
  5. Organ scaffold transplantation
  6. Critical challenges
  7. Conclusions
  8. Future perspective
  9. Acknowledgements
  10. References

After preparing whole-liver scaffolds with the perfusion decellularization technique, these decellularized organs with intact vascular networks and three-dimensional structures can then be readily recellularized with freshly isolated cells and maintained in bioreactors for cell expansion, differentiation and function. Prior to recellularization, optimal cell sources and reseeding strategies need to be chosen to guarantee redistribution of the reseeded cells and, thus, a functional engineered liver.

Cell sources

Primary hepatocytes offer the benefit of being fully functional and are therefore able to quickly replace damaged hepatocytes upon delivery. Some researchers have reported the use of primary hepatocytes to recellularize the liver scaffold to treat hepatic failure [36, 39]. However, this method only achieved short-term survival. The shortage of organ donors, limited proliferation capabilities and possible changes in physiological and functional characteristics during in vitro culture [44] limit their application in liver tissue engineering.

Stem cells, such as liver stem cells, embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs) and mesenchymal stem cells (MSCs), are a promising alternative for primary hepatocytes. The bipotent differentiation potential of liver stem cells makes them an ideal source for recellularization [45, 46]. In addition, Baptista [47] demonstrated that a bioscaffold is able to support the differentiation of fetal hepatoblasts into biliary and hepatocytic lineages on the basis of the detection of CK19+/CK18/ALB tubular structures and clusters of ALB+/CK18+ cells in the parenchyma. For clinical applications, studies have identified and confirmed the efficacy of fetal liver hepatic progenitors in end-stage liver diseases [48]. However, the difficulty involved in obtaining large numbers of fetal liver cells, along with ethical and immune rejection issues, limit the extent of clinical applications for this model. ESCs are attracting more and more attention in recent years because of their unlimited expansion, easy availability and less immunogenic properties. However, the safety and ethical issues involved in the use of ESCs are always the focus of controversy and are undoubtedly the major obstacle to clinical translation [49]. Recently, a breakthrough in generating iPSCs from somatic cells has overcome the ethical issues and immune rejection involved in the use of ESCs. The key advantages of iPSCs include that they constitute an unlimited potential cell source and that they are patient-specific and pluripotent [50]. Many studies showed that iPSCs can be differentiated into hepatocytes and restore liver function in an animal model of liver failure [51, 52]. iPSCs have also been used to recellularize a decellularized mouse heart [53]. Despite these advantages, several technical issues, such as the generation of iPSCs without viral integration and the elimination of tumour formation and genetic mutations, still need to be addressed. Fortunately, recent developments in transposon-mediated reprogramming and virus-free induction strategies provide optimism that safe iPS cells without any genomic modification could be used in future clinical applications [54, 55].

MSCs, which can be isolated from bone marrow and other tissues, including cord blood (CB-MSC), placenta, adipose tissue (AT-MSC), brain, liver, lung and kidney, are an ideal cell source for tissue engineering [56]. Compared to primary hepatocytes, MSCs are characterized by adequate availability, easy accessibility, rapid proliferation, multipotent differentiation and successful integration and immunological tolerance in host tissues. MSCs can typically give rise to many types of mesodermal tissues, such as bone, cartilage, smooth muscle and fat. Further, their immunomodulatory properties have generated great interest in applying MSCs to tissue generation and cell-based therapies for various liver diseases [57]. In addition, their safety and efficacy have been confirmed via human bone marrow MSC (hBMSC) transplantation in pigs through the intraportal route for the treatment of fulminant hepatic failure [58]. Meanwhile, the decellularized liver scaffold was demonstrated to promote the hepatic differentiation of MSCs, which eventually exhibit the ultrastructural and functional characteristics of mature hepatocytes [59]. Above all, MSCs can be considered an ideal cell source for liver tissue engineering when compared to other types of stem cells.

Cell numbers for recellularization

The liver is estimated to contain approximately 4 × 109 cells per kilogram of body weight in adults [60]. Some success has been achieved with the transplantation of 1–10% of native liver mass in pigs and humans [61], though the cell number required to support an animal model of hepatic failure still cannot be systematically determined. For some organs, such as the liver, the transplantation of a high concentration of cells could lead to extensive cell death or occlusion of the vascular spaces. Based on these factors, 5–10 × 107 cells have been used for the recellularization of decellularized rat liver scaffolds [36, 38, 39, 47]; analyses of the transplanted cells’ viability and function demonstrated the feasibility of using decellularized liver scaffolds in liver tissue engineering and fuelled enthusiasm for more ambitious regenerative approaches. In addition, seeding the bioscaffold with nonparenchymal cell types (i.e. endothelial, stellate or cholangiocyte cells) and hepatocytes in a ratio of 1:3 is critical for the formation of liver structures and may extend the potential long-term efficacy of a liver-assist device by approximately 7 days [62]. According to the coseeding theory, the seeding strategy might be helpful for the generation of a vascularized liver organoid. Further studies are underway to determine the accurate number of cells that would be sufficient for various liver diseases.

Reseeding strategies

Many studies have confirmed that a decellularized liver scaffold with natural ECM components in a three-dimensional structure could be an ideal carrier for transplanted cells. A major obstacle in producing large-volume tissues is the redistribution of adequate numbers of cells to their original locations. The commonly used method for recellularization includes direct parenchymal injection, multistep infusion and continuous perfusion. Alejandro et al. [41] evaluated three methods by perfusing 1–5 × 107 cells with these three methods and then determined the cell numbers and the viability retained in the liver with each method. The results demonstrated that the engraftment efficiency using the multistep infusion method was significantly higher than the efficiencies with the direct injection and pump perfusion methods. Uygun et al. [39] reported a similar result by introducing 5 × 107 cells with a four-step seeding method and a single-step infusion method. In addition, multistep injection enables better rearrangement of seeded cells in whole-organ scaffolds and results in fewer complications, such as obstruction, thrombosis and embolism. Based on these ideas, we can perform repeated infusions at intervals until the reseeded cell number reaches 10% of the total cell numbers, but with less than 1% of the liver mass being infused at each infusion [61].

To achieve full repopulation in the scaffold, Baptista [47] determined that cells seeded through the vena cava predominantly distribute in the pericentral area, while cells seeded through the portal vein selectively deposited in the periportal area. This ‘selective seeding’ brings out a hypothesis that the simultaneous utilization of both vascular routes for cell seeding enables complete access to the entire length of the vascular network, which is essential for the prevention of blood clot formation.

To improve the reseeding efficiency, the flow rate also needs to be considered. According to Kim S, the flow rate needed for the survival of the initial cell mass is estimated to be at least 1 ml/min [63]. To further optimize the flow rate for the cell attachment and population of the bioscaffold, Ji R et al. [59] recycled the medium at flow rates of 0.5, 1, 2, 4 and 6 ml/min with a peristaltic pump. Determination of the dsDNA amounts and percentages of TUNEL+ cells indicated that a 4 ml/min flow rate was a better choice to ensure adequate oxygen and nutrition delivery for the transplanted cells. Our task is to determine whether the flow rate of 4 ml/min is the best choice.

Organ scaffold transplantation

  1. Top of page
  2. Abstract
  3. Organ decellularization
  4. Organ recellularization
  5. Organ scaffold transplantation
  6. Critical challenges
  7. Conclusions
  8. Future perspective
  9. Acknowledgements
  10. References

The ultimate aim of liver tissue engineering is in vivo transplantation, which could substitute for the non-functional liver and could help to improve the quality of the patient's life. The method used for transplanting the tissue-engineered liver (TEL) is of utmost importance, and potentially feasible ideas are well worth trying.

Studies indicate that liver tissues can be engineered and maintained at extrahepatic sites while retaining their capacity for regeneration in vivo and thus can be used to successfully treat genetic disorders [64]. This approach is further supported by the recent interest in the capacity to generate mature hepatocytes from embryonic, hematopoietic and somatic stem cells as alternative cell sources [65]. Based on this theory, Uygun et al. [39] operated on a unilateral nephrectomy to prepare a viable site for auxiliary liver graft transplantation, with the renal vein and artery as ports to create blood flow within the graft. However, the recipient rat survived only 8 h after transplantation. One possible reason behind the short-term survival may be the loss of nutrients from the hepatic portal vein (PV), as ectopic sites do not normally offer sufficient hepatotrophic factors and result in transplanted hepatocytes being prone to necrosis [66]. Further experiments should be undertaken to determine the cause of this short-term survival.

The PV, a blood vessel which is formed by the union of the superior mesenteric vein and the splenic vein, delivers approximately 75% of the hepatic blood supply from the gastrointestinal tract and spleen to the liver. This blood is rich in nutrients and hepatotrophic factors [66]; for these reasons, the PV system could serve as a better graft site. Baptista et al. [18] put forward a scenario in which both the PV and the vena cava of the bioscaffold were end-to-side anastomosed with the superior mesenteric vein and the native vena cava, respectively, of the host rat using a microsurgery microscope. This proposal was elegant, but it was not put into practice. Ji Bao et al. [36] performed an end-to-end anastomosis of the donor PV and the suprahepatic inferior vena cava to the recipient rat's inferior and superior PV incisions, respectively, to treat 90% hepatectomy rats. The recipient rats died from small-for-size syndrome at 72 h post-operation. Although TELs did not support long-term survival, they still significantly prolonged the mean life span of the rats that underwent 90% hepatectomies from 16 to 72 h. Analysis of the TEL indicated that hepatocytes in the TEL exhibited enhanced capabilities in proliferation, colonization and biofunction.

During the transplantation procedure, blood volume is an issue that we often encounter. With the depletion of all cells in the liver, the liver scaffolds need more blood to be fully filled. The general formula for the rat's blood volume (BV) is closely related to body weight (BW). The relationship between these two variables can be described as BV (ml) = 0.06 × BW (g) + 0.77 [67]. Whereas the whole-liver scaffold generally needs approximately 4 ml blood to be fully filled, several attempts have failed to fulfil whole-liver perfusion. Partial liver scaffold transplantation or fluid infusion prior to transplantation might be able to solve this puzzle. Except for blood volume, the pressure gradient between the inflow and outflow ports of the whole-liver scaffold is also of great significance and should be well considered.

Critical challenges

  1. Top of page
  2. Abstract
  3. Organ decellularization
  4. Organ recellularization
  5. Organ scaffold transplantation
  6. Critical challenges
  7. Conclusions
  8. Future perspective
  9. Acknowledgements
  10. References

In vitro preservation

The use of stem or progenitor cells for recellularization requires long-term in vitro culturing for cellular proliferation, maturation and attachment; otherwise, the reseeded cells may experience up to 95% unattachment in the first 24 h post-implantation [68]. To guarantee the viability and function of the reseeded cells in the scaffold, a suitable environment is needed, such as 37°C, 5% CO2. However, long-term preservation in this environment may result in the deterioration of the ECM components. These issues not only emphasize the problem of applicability of the bioscaffold but also affect the normal physiological activities of the transplanted cells. Thus, improved preservation methods and technologies are urgently needed. Normothermic machine perfusion by bioreactor with modifications is now receiving renewed interest as a strategy to preserve recellularized whole-liver scaffolds. A bioreactor is a type of extracorporeal organ perfusion device that can provide a constant supply of nutrients and oxygen while simultaneously removing harmful wastes [69]. Bioreactors have long been used in organ preservation, and significant advancements have been achieved. Early reports in recellularized whole-heart scaffolds have reported successful preservation on the order of 4 weeks [28]. It is still unknown whether existing bioreactor systems are capable of maintaining a fully recellularized three-dimensional liver scaffold in terms of temperature, perfusate, chemical factors and the mechanical environment; several factors, including flow rate and perfusion, all need to be well considered, as each of these factors individually can have a dramatic impact on tissue growth. One innovative idea that was brought forth by Badylak was that instead of transplanting the recellularized tissue-engineered liver, simply transplanting the acellular organ scaffold into the patient and letting it grow with the patient's own cells might aid in avoiding long-term ex vivo culturing in bioreactors, if this strategy is feasible [19].

Anticoagulation

The decellularized liver scaffold retains an intact vascular network and major ECM materials. Collagen is the main component of the ECM, but it activates the extrinsic coagulation system when it contacts blood. Naturally, the major problem we encounter in bioscaffold transplantation is thrombogenicity. Several attempts have been made to reduce thrombosis. Systemic pharmacologic approaches, including the use of anticoagulant and antiplatelet agents, have significant untoward side effects and have not dramatically improved failure rates in many applications [70]. Novel anticoagulants currently being explored do have advantages over traditional anticoagulants, such as fewer side effects, minimal drug-drug interactions and others. However, the newer anticoagulants do not have specific antidotes [71]. Alternative treatments need to be explored. Recently, surface modifications of materials are of primary importance for biomedical applications [72, 73], and polyelectrolyte multilayer (PEM) deposition has emerged as a very easy-handling and versatile tool [74]. Ji Bao et al. [36] employed the layer-by-layer (LbL) self-assembly technique to accomplish matrix internal surface anticoagulant modification, and they confirmed the feasibility of the LbL self-assembly technique. In terms of biocompatibility, the polyelectrolyte poly (diallyldimethylammonium chloride) (PDADMAC) they used as the positively charged material was not an ideal choice, though protamine sulphate, a good biocompatible material, can serve as a sufficient substitute for PDADMAC [75]. The reseeding efficiency might be improved when protamine sulphate is employed to form heparin-modified inner surfaces.

The endothelial coverage of the vasculature's lumen is essential to prevent thrombosis and to provide proper vascular function. Many papers have reported the application of endothelialization with human umbilical vein endothelial cells in liver tissue engineering [47, 76]. In this method, the anticoagulant effect was confirmed by perfusing seeded and unseeded bioscaffolds with fresh rat heparinized blood. Enhancing the endothelialization efficiency is another major challenge that will need to be overcome.

The anticoagulation issue has been a rate-limiting step for tissue engineering. Although significant advancements have been achieved in anticoagulation in animal models, further research is still urgently needed to enhance the anticoagulant effect. A combination of the LbL self-assembly technique and endothelialization result in a better anticoagulant effect and thus needs to be explored with further studies.

Endothelialization

For whole-liver scaffolds that retain intact vessel networks, the ECs, which cover the vascular lumen, are considered to be major participants in the angiogenesis process in physiological and pathological conditions. ECs are responsible for reducing the possibility of thrombosis and for protecting the parenchymal cells from shear stress [77]. Thus, it is of great importance to sufficiently prepare an endothelialization. Several studies have indicated that ECs can adhere to the internal surfaces of blood vessel structures within 24 h. Furthermore, ECs do not leak outside of blood vessel structures [78]. Based upon these observations, accomplishing endothelialization using the blood vessel network template originally in the native liver should be possible. Thus, enhancing the endothelialization efficiency is of great importance. The electrostatic seeding technique might be helpful for establishing adequate EC adherence on the graft in a relatively short time period prior to implantation [79]. Recent advances in therapeutic angiogenesis have demonstrated the power of angiogenic factors in inducing endothelialization [80-82]. Surface-modifying prosthetic devices with either vascular endothelial growth factor (VEGF) or fibroblast growth factor (FGF) and both in vitro and animal data suggest a potent stimulation of surface re-endothelialization [83]. All of the studies cited above help to provide new excitement in promoting angiogenesis via the local delivery of angiogenic factors and therefore help to attain better endothelialization and prevent thrombosis. However, a combination of concentrations and exposure times to the angiogenic factors should be tested to optimize conditions for high-efficiency endothelialization. In addition to angiogenic factors, the coculturing of ECs with target tissue cells is another conventional method for spontaneously inducing angiogenesis inside tissue-engineered constructs [84]. MSCs have been shown to be helpful in the recruitment of endothelial progenitor cells (EPCs)/ECs and the promotion of angiogenesis because of their paracrine effects [85]. Based on these data, the coculturing of vascular cell types (ECs, EPCs) with MSCs is very effective in the production of vascularized tissue constructs. In addition, the coculturing of ECs with MSCs has also been shown to enhance the vascularization of tissue-engineered vascular grafts in vivo [86]. To achieve the full endothelialization of a three-dimensional scaffold, effective stimulation, such as with pulsatile flow rather than continuous flow, may be required. And the flow rate also needs to be taken into careful consideration. Naturally, physiological or near-physiological flow rates are common and logical first options [87].

Conclusions

  1. Top of page
  2. Abstract
  3. Organ decellularization
  4. Organ recellularization
  5. Organ scaffold transplantation
  6. Critical challenges
  7. Conclusions
  8. Future perspective
  9. Acknowledgements
  10. References

The decellularized scaffolds are currently attractive to the liver tissue engineering. To date, numerous papers have defined the process of decellularization, but most of them cannot fully meet the requirements for the maximal absence of cells and the preservation of the ECM components without any damage to them. Among the numerous types of cell sources, the hBMSCs might be considered as an optimal cell for recellularization. Considering the future clinical application of TEL, some critical issues need to be solved, such as anticoagulation, endothelialization and so on.

Future perspective

  1. Top of page
  2. Abstract
  3. Organ decellularization
  4. Organ recellularization
  5. Organ scaffold transplantation
  6. Critical challenges
  7. Conclusions
  8. Future perspective
  9. Acknowledgements
  10. References

To realize the potential benefits of decellularized liver scaffolds in clinical applications, combinations of perfusate concentrations, perfusion times and flow rates need to be well designed. In addition, vascularization is also a critical determinant for clinical success. Advances in the comprehension of the biology behind neovascularization provide basic data on which we can build and optimize the normal growth and development of vessels within scaffolds. Innovative liver tissue engineering using a decellularized natural platform with anticoagulant surface modification is in its early stages of development, but success in the treatment of acute liver failure in rats has inspired us with enthusiasm [36, 39]. Further studies in a large animal model will be needed to confirm potential therapeutic efficiency, which would then be ultimately applied to future clinical transplantations. Porcine organs are attractive for xenotransplantation, and the three-dimensional bioengineered scaffolds of porcine organs may have tremendous potential for producing both non-immunogenic transplantable organs and beneficial tools for biomedical studies on organ re-engineering and repair.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Organ decellularization
  4. Organ recellularization
  5. Organ scaffold transplantation
  6. Critical challenges
  7. Conclusions
  8. Future perspective
  9. Acknowledgements
  10. References

This article was supported by the Zhejiang Provincial and National Natural Science Foundation of China (LR13H030001, 81271708), Chinese High Tech Research and Development (863) Program (2013AA020102), and National S&T Major Project (2012ZX10004503-006, 2012ZX10002004-001).

Financial support: The authors declare that no competing financial interests exist.

Conflict of interest: The authors do not have any disclosures to report.

References

  1. Top of page
  2. Abstract
  3. Organ decellularization
  4. Organ recellularization
  5. Organ scaffold transplantation
  6. Critical challenges
  7. Conclusions
  8. Future perspective
  9. Acknowledgements
  10. References