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Bioscaffolds serve as structures for cells in building complex tissues and full organs including heart. Decellularizing cardiac tissue results in cell-free extracellular matrix (ECM) that can be used as a cardiac tissue bioscaffold. The field of whole-heart tissue engineering has been revolutionized since the 2008 publication of the first perfusion-decellularized whole heart, and since then, studies have shown how decellularized cardiac tissue retains its native architecture and biochemistry following recellularization. Chemical, enzymatic, and physical decellularization methods preserve the ECM to varying degrees with the widely accepted standard of less than 50 ng/mg of double-stranded DNA present in decellularized ECM. Following decellularization, replacement of cells occurs via recellularization: seeding cells into the decellularized ECM structure either via perfusion of cells into the vascular conduits, injection into parenchyma, or a combination of perfusion and injection. Endothelial cells are often perfused through existing vessel conduits to provide an endothelial lining of the vasculature, with cardiomyocytes and other parenchymal cells injected into the myocardium of decellularized ECM bioscaffolds. Uniform cell density and cell retention throughout the bioscaffold still needs to be addressed in larger animal models of the whole heart. Generating the necessary cell numbers and types remains a challenge. Still, recellularized cardiac tissue bioscaffolds offer therapeutic solutions to heart failure, heart valve replacement, and acute myocardial infarction. New technologies allow for decellularized ECM to be bioprinted into cardiac bioscaffolds or formed into a cardiac hydrogel patch. This chapter reviews the advances made in decellularization and recellularization of cardiac ECM bioscaffolds with a discussion of the potential clinical applications of ECM bioscaffolds.

Scaffolds, both natural and synthetic, used in tissue engineering provide mechanical support to cells. Tissue decellularization has been used to provide natural extracellular matrix scaffolds for tissue engineering purposes. In this chapter we focus on describing the methodology used to decellularize Wharton's jelly matrix, the mucous connective tissue that surrounds umbilical cord vessels, to obtain decellularized Wharton's jelly matrix (DWJM); an extracellular matrix that can be used for tissue engineering purposes. We also, briefly, describe our experience with processing DWJM for cell seeding and recellularization.

Decellularization of cartilage enables the use of cartilage allografts or xenografts as natural scaffolds for repair and regeneration of injured cartilage. The preservation of the extracellular matrix ultrastructure of the graft makes this a promising tool for cartilage tissue engineering. We have optimized the decellularization protocol by enzymatically digesting proteoglycans while preserving the native collagen architecture. Here we describe our methods for cartilage decellularization and cell labeling for the tracking of infiltration for recellularization in detail.

Severe liver disease is the 12th leading cause of death in the USA, with organ transplantation often being the only viable option for treatment. However, due to the shortage of viable donor livers, it is estimated that over 1200 patients died in 2015 while waiting for liver transplantation. This highlights the need for alternative sources of viable organs. In this study, we describe a method that provides the groundwork for the development of functional liver grafts. The approach described here is for removal of cells from intact livers and subsequently repopulating them with functional liver cells. Briefly, rat livers are harvested and subjected to a series of perfusion decellularization steps using an anionic detergent such that an intact decellularized liver matrix (DLM) scaffold with preserved vascular architecture is obtained. Further, we describe methods to recellularize DLM scaffolds with adult primary hepatocytes, creating a liver graft that exhibits hepatic functions in vitro.

Decellularized scaffolds present promising biomimetic approaches in various fields of tissue engineering. Different tissues have been selected for decellularization, among them extracellular matrix (ECM)-rich tissues such as tendons, ligaments and cartilage. The dense ECM of ligaments is particularly challenging to achieve a completely non-immunogenic ECM void of any cells. Here, the methods for decellularization adapted to ligamentous tissue of the iliotibial band (ITB) are presented along with cell isolation and several recolonization techniques using allogenic ITB-derived fibroblasts or mesenchymal stromal cells (MSCs).

The role of the cardiac extracellular matrix (cECM) in providing biophysical and biochemical cues to the cells housed within during disease and development has become increasingly apparent. These signals have been shown to influence many fundamental cardiac cell behaviors including contractility, proliferation, migration, and differentiation. Consequently, alterations to cell phenotype result in directed remodeling of the cECM. This bidirectional communication means that the cECM can be envisioned as a medium for information storage. As a result, the reprogramming of the cECM is increasingly being employed in tissue engineering and regenerative medicine as a method with which to treat disease. In this chapter, an overview of the composition and structure of the cECM as well as its role in cardiac development and disease will be provided. Additionally, therapeutic modulation of cECM for cardiac regeneration as well as bottom-up and top-down approaches to ECM-based cardiac tissue engineering is discussed. Finally, lingering questions regarding the role of cECM in tissue engineering and regenerative medicine are offered as a catalyst for future research.

After being initially hailed as the ultimate solution to end-stage organ failure, such as end-stage liver disease (ESLD), engineering of vascularized tissues has stalled because of the need for a well-structured circulatory system that can maintain the cells to be seeded inside the construct.In the field of regenerative medicine, decellularized scaffolds, derived mainly from various non-autologous whole organs, have become an emerging treatment technique to overcome this obstacle. As a result of significant progress made in recent years, organogenesis through whole-organ decellularization scaffolds may now become more feasible than ever before. In this chapter, we describe in detail the necessary steps for liver organogenesis using a decellularized acellular scaffold (DAS), seed cell isolation, and recellularization in a bioreactor-like culture system. This new technique to re-engineer organs may have major implications for the fields of drug discovery, organ transplantation, and ultimately regenerative medicine.

Deaths due to end-stage liver diseases are increasingly registered annually in the world. Liver transplantation is the ultimate treatment for end-stage liver diseases to date, which has been hampered by a critical shortage of organs. The potential of decellularized liver scaffolds (DLS) derived from solid organs as a three-dimensional platform has been evolved as a promising approach in liver tissue engineering for translating functional liver organ replacements, but questions still exist regarding the optimal cell population for seeding in DLS and the preparation of the DLS themselves. The aim of our study was to utilize a sodium dodecyl sulfate decellularization procedure in combination with a low concentration of trypsin (0.005%)-ethylenediaminetetraacetic acid (0.002%) process to manufacture DLS from whole mouse livers and recellularized with hepatic stem/progenitors for use in liver tissue engineering and injured liver treatment. Results showed that the DLS generated with all the necessary microstructure and the extracellular components to support seeded hepatic stem/progenitor cell attachment, functional hepatic cell differentiation. Hepatic differentiation from stem/progenitor cells loaded by DLS was more efficient than that of the stem/progenitor cells in the two-dimensional cell culture model. In summary, the method of DLS loaded by hepatic stem/progenitor cells provided by this study was effective in maintaining DLS extracellular matrix to introduce seeded stem/progenitor cell differentiation, hepatic-like tissue formation and functional hepatic protein production in vitro that promoted functional recovery and survival in a mouse model of dimethylnitrosamine-induced liver cirrhosis after auxiliary heterotopic liver transplantation. Copyright © 2016 John Wiley & Sons, Ltd., (Copyright © 2016 John Wiley & Sons, Ltd.)

Objective: To create a bioengineered uterine patch for uterine repair of a partially defect uterus.Design: Three different decellularized uterine scaffolds were recellularized in vitro with primary uterine cells and green fluorescent protein- (GPF-) labeled bone marrow-derived mesenchymal stem cells (GFP-MSCs). The patches were transplanted in vivo to investigate their tissue adaptation and supporting capacity during pregnancy.Setting: Research laboratory.Animal(s): Female Lewis rats (n = 9) as donors to generate whole-uterus scaffolds using three different protocols (n = 3 per protocol); Sprague Dawley rats (n = 40) for primary uterus cell isolation procedures (n = 10) and for transplantation/pregnancy studies (n = 30); and male Sprague Dawley rats (n = 12) for mating.Intervention(s): Decellularization was achieved by whole-uterus perfusion with buffered or nonbuffered Triton-X100 and dimethyl sulfoxide (DMSO; group P1/P2) or with sodium deoxycholate (group P3). Primary uterine cells and GFP-MSCs were used to develop uterine tissue constructs, which were grafted to uteri with partial tissue defects.Main Outcome Measure(s): Recellularization efficiency and graft quality were analyzed morphologically, immunohistochemically, and by real-time quantitative polymerase chain reaction (PCR). The location and number of fetuses were documented during pregnancy days 16-20.Result(s): Pregnancy and fetal development were normal in groups P1 and P2, with fetal development over patched areas. Group P3 showed significant reduction of fetal numbers, and embryos were not seen in the grafted area. Quantitative PCR and immunohistochemistry revealed uterus-like tissue in the patches, which had been further reconstructed by infiltrating host cells after transplantation.Conclusion(s): Primary uterine cells and MSCs can be used to reconstruct decellularized uterine tissue. The bioengineered patches made from triton-X100+DMSO-generated scaffolds were supportive during pregnancy. These protocols should be explored further to develop suitable grafting material to repair partially defect uteri and possibly to create a complete bioengineered uterus. [ABSTRACT FROM AUTHOR]

Despite progress in the field of decellularization and recellularization, the outcome for pancreas has not been adequate. This might be due to the challenging dual nature of pancreas with both endocrine and exocrine tissues. We aimed to develop a novel and efficient cold-perfusion method for decellularization of porcine pancreas and recellularize acellular scaffolds with human fetal pancreatic stem cells. Decellularization of whole porcine pancreas at 4°C with sodium deoxycholate, Triton X-100 and DNase efficiently removed cellular material, while preserving the extracellular matrix structure. Furthermore, recellularization of acellular pieces with human fetal pancreatic stem cells for 14 days showed attached and proliferating cells. Both endocrine (C-peptide and PDX1) and exocrine (glucagon and α-amylase) markers were expressed in recellularized tissues. Thus, cold-perfusion can successfully decellularize porcine pancreas, which when recellularized with human fetal pancreatic stem cells shows relevant endocrine and exocrine phenotypes. Decellularized pancreas is a promising biomaterial and might translate to clinical relevance for treatment of diabetes., Competing Interests: Declaration of conflicting interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: S.S.H. holds shares in NovaHep AB, a biotechnology company in the field of regenerative medicine. The others have no conflicts of interest.

Articular cartilage (AC) possesses uniquely complex mechanical properties; for example its stiffness increases with depth through the tissue and it softens when compressed. These properties are integral to the function of AC and can be attributed to the tissue's collagen network and how it interacts with negatively charged proteoglycans. In this study, scaffolds containing arrays of channels were produced from decellularized AC explants derived from skeletally immature and mature pigs. These scaffolds were then repopulated with human infrapatellar fat pad derived stem cells (FPSCs). After 4 weeks in culture, FPSCs filled channels within the decellularized explants with a matrix rich in proteoglycans and collagen. Cellular and neo-matrix alignment within these scaffolds appeared to be influenced by the underlying collagen architecture of the decellularized cartilage. Repopulating scaffolds derived from decellularized skeletally mature cartilage with FPSCs led to the development of engineered cartilage with depth-dependent mechanical properties mimicking aspects of native tissue. Furthermore, these constructs displayed the characteristic strain softening behavior of AC. These findings highlight the importance of the collagen network to engineering mechanically functional cartilage grafts.

The tissue-engineered heart valve portends a new era in the field of valve replacement. Decellularized heart valves are of great interest as a scaffold for the tissue-engineered heart valve due to their naturally bioactive composition, clinical relevance as a stand-alone implant, and partial recellularization in vivo. However, a significant challenge remains in realizing the tissue-engineered heart valve: assuring consistent recellularization of the entire valve leaflets by phenotypically appropriate cells. Many creative strategies have pursued complete biological valve recellularization; however, identifying the optimal recellularization method, including in situ or in vitro recellularization and chemical and/or mechanical conditioning, has proven difficult. Furthermore, while many studies have focused on individual parameters for increasing valve interstitial recellularization, a general understanding of the interacting dynamics is likely necessary to achieve success. Therefore, the purpose of this review is to explore and compare the various processing strategies used for the decellularization and subsequent recellularization of tissue-engineered heart valves., Competing Interests: Declaration of conflicting interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Three-dimensional (3D) in vitro models have been established to study the physiology and pathophysiology of the endometrium. With emerging evidence that the native extracellular matrix (ECM) provides appropriate cues and growth factors essential for tissue homeostasis, we describe, a novel 3D endometrium in vitro model developed from decellularized human endometrial tissue repopulated with primary endometrial cells. Analysis of the decellularized endometrium using mass spectrometry revealed an enrichment of cell adhesion molecules, cytoskeletal proteins, and ECM proteins such as collagen IV and laminin. Primary endometrial cells within the recellularized scaffolds proliferated and remained viable for an extended period of time in vitro. In order to evaluate the hormonal response of cells within the scaffolds, the recellularized scaffolds were treated with a modified 28-day hormone regimen to mimic the human menstrual cycle. At the end of 28 days, the cells within the endometrial scaffold expressed both estrogen and progesterone receptors. In addition, decidualization markers, IGFBP-1 and prolactin, were secreted upon addition of dibutyryl cyclic AMP indicative of a decidualization response. This 3D model of the endometrium provides a new experimental tool to study endometrial biology and drug testing., (© The Authors 2017. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please journals.permissions@oup.com.)

Organ transplantation is an effective treatment for chronic organ dysfunctioning conditions. However, a dearth of available donor organs for transplantation leads to the death of numerous patients waiting for a suitable organ donor. The potential of decellularized scaffolds, derived from native tissues or organs in the form of scaffolds has been evolved as a promising approach in tissue-regenerative medicine for translating functional organ replacements. In recent years, donor organs, such as heart, liver, lung and kidneys, have been reported to provide acellular extracellular matrix (ECM)-based scaffolds through the process called 'decellularization' and proved to show the potential of recellularization with selected cell populations, particularly with stem cells. In fact, decellularized stem cell matrix (DSCM) has also emerged as a potent biological scaffold for controlling stem cell fate and function during tissue organization. Despite the proven potential of decellularized scaffolds in tissue engineering, the molecular mechanism responsible for stem cell interactions with decellularized scaffolds is still unclear. Stem cells interact with, and respond to, various signals/cues emanating from their ECM. The ability to harness the regenerative potential of stem cells via decellularized ECM-based scaffolds has promising implications for tissue-regenerative medicine. Keeping these points in view, this article reviews the current status of decellularized scaffolds for stem cells, with particular focus on: (a) concept and various methods of decellularization; (b) interaction of stem cells with decellularized scaffolds; (c) current recellularization strategies, with associated challenges; and (iv) applications of the decellularized scaffolds in stem cell-driven tissue engineering and regenerative medicine. Copyright © 2015 John Wiley & Sons, Ltd., (Copyright © 2015 John Wiley & Sons, Ltd.)

Due to the complex function and structure of the liver, resourceful solutions for treating end-stage liver disease are required. Currently, liver transplantation is the only curative therapeutic option. However, due to a worldwide donor shortage, researchers have been looking in other fields for alternative sources of transplantable liver tissue. Recent advances in our understanding of liver physiology, stem cell and matrix biology, have accelerated tissue engineering research. Most notable is the discovery of a culture system to grow liver-like organoids from human hepatic stem cells. The extensive expansion capacity of these stem cells has contributed greatly to the availability of hepatocyte-like cells for tissue engineering. In addition, new techniques are explored to obtain biological liver scaffolds from full size donor organs. This review summarizes these state-of-art techniques which may lay the groundwork towards re-creating transplantable tissue from autologous or allogenic stem cells in the coming decade., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

One of the main challenges currently faced by tissue engineers is the loss of tissues postimplantation due to delayed neovascularization. Several strategies are under investigation to create vascularized tissue, but none have yet overcome this problem. In this study, we produced a decellularized natural vascular scaffold from rat intestine to use as an in vitro platform for neovascularization studies for tissue-engineered constructs. Decellularization resulted in almost complete (97%) removal of nuclei and DNA, while collagen, glycosaminoglycan, and laminin content were preserved. Decellularization did, however, result in the loss of elastin and fibronectin. Some proangiogenic factors were retained, as fragments of decellularized intestine were able to stimulate angiogenesis in the chick chorioallantoic membrane assay. We demonstrated that decellularization left perfusable vascular channels intact, and these could be repopulated with human dermal microvascular endothelial cells. Optimization of reendothelialization of the vascular channels showed that this was improved by continuous perfusion of the vasculature and further improved by infusion of human dermal fibroblasts into the intestinal lumen, from where they invaded into the decellularized tissue. Finally we explored the ability of the perfused cells to form new vessels. In the absence of exogenous angiogenic stimuli, Dll4, a marker of endothelial capillary-tip cell activation during sprouting angiogenesis, was absent, indicating that the reformed vasculature was largely quiescent. However, after addition of vascular endothelial growth factor A, Dll4-positive endothelial cells could be detected, demonstrating that this engineered vascular construct maintained its capacity for neovascularization. In summary, we have demonstrated how a natural xenobiotic vasculature can be used as an in vitro model platform to study neovascularization and provide information on factors that are critical for efficient reendothelialization of decellularized tissue., Competing Interests: Statement No competing financial interests exist.

Interest in decellularized tissues has steadily gained as potential solutions for degenerative diseases and traumatic events, replacing sites of missing tissue, and providing the relevant biochemistry and microstructure for tissue ingrowth and regeneration. Osteoarthritis, a progressive and debilitating disease, is often initiated with the formation of a focal defect in the otherwise smooth surface of articular cartilage. Decellularized cartilage tissue, which maintains the structural complexity of the native extracellular matrix, has the potential to provide a clinically relevant solution to focal defects or large tissue damage, possibly even circumventing or complementing current techniques such as microfracture and mosaicplasty. However, it is currently unclear whether implantation of decellularized cartilage in vivo may provide a mechanically and biochemically relevant platform to promote cell remodeling and repair. We examined whole decellularized osteochondral allografts implanted in the ovine trochlear groove to investigate cellular remodeling and repair tissue quality compared to empty defects and contralateral controls (healthy cartilage). At 3 months postsurgery, cells were observed in both the decellularized tissue and empty defects, although both at significantly lower levels than healthy cartilage. Qualitative and quantitative histological analysis demonstrated maintenance of cartilage features of the decellularized implant similar to healthy cartilage groups. Noninvasive analysis by quantitative magnetic resonance imaging showed no difference in T 1ρ and T 2 * between all groups. Investigation of the mechanical properties of repair tissue showed significantly lower elasticity in decellularized implants and empty defects compared to healthy cartilage, but similar tribological quantities. Overall, this study suggests that decellularized cartilage implants are subject to cellular remodeling in an in vivo environment and may provide a potential tissue engineering solution to cartilage defect interventions., Competing Interests: Statement No competing financial interests exist.

Objectives: Because therapeutic options for severe diabetes are currently limited, there is a continuing need for new therapeutic strategies, especially in the field of regenerative medicine. Collaborative efforts across the fields of tissue engineering technology and islet biology may be able to create functionally engineered islets capable of restoring endocrine function in patients with insulin-dependent diabetes., Methods: This engineered scaffold was seeded with isolated primary porcine islets via the pancreatic duct using a multi-step infusion technique. Endocrine function of perfusion-cultured islets in the native scaffold was analyzed by immunohistochemical staining of insulin and glucagon as well as by the insulin stimulation test., Results: The pancreas in this large animal could be uniformly decellularized by perfusion with trypsin and TritonX-100 via the pancreatic duct, as shown by positive staining of extracellular matrix (ECM) components. These scaffolds derived from porcine pancreas were able to maintain the cellular integrity of islets that had repopulated the parenchymal space, which is fundamental for the restoration of endocrine function. Insulin release up to four days after islet infusion was maintained., Conclusions: This scaffold from a large animal maintained islet survival and function in the short-term, retaining the cells as a solid organ in the parenchymal space after infusion through the pancreatic duct. These results suggest that this scaffold is suitable for further fabrication of fully functional bioengineered endocrine pancreases when implanted in vivo. Therefore, it may represent a key improvement in the field of beta-cell replacement therapy. Nonetheless, the facilitation of longer-term islet survival and studies of implantation in vivo is required for successful clinical translation., (Copyright © 2016 IAP and EPC. Published by Elsevier B.V. All rights reserved.)

End stage renal disease (ESRD) is a progressive loss of kidney function with a high rate of morbidity and mortality. Transplantable organs are hard to come by and hold a high risk of recipient immune rejection. We intended to establish a more effective and faster method to decellularize and recellularize the kidney scaffold for transplant and regeneration. We successfully produced renal scaffolds by decellularizing rat kidneys with 0.5% sodium dodecyl sulfate (SDS), while still preserving the extracellular matrix (ECM) 3D architecture, an intact vascular tree and biochemical components. We recellularized the kidney scaffolds with mouse embryonic stem (ES) cells that then populated and proliferated within the glomerular, vascular, and tubular structures. After in vivo implantation, these recellularized scaffolds were easily reperfused, tolerated blood pressure and produced urine with no blood leakage. Our methods can successfully decellularize and recellularize rat kidneys to produce functional renal ECM scaffolds. These scaffolds maintain their basic components, retain intact vasculature and show promise for kidney regeneration.

With the advent of whole organ decellularization, extracellular matrix scaffolds suitable for organ engineering were generated from numerous tissues, including the heart, lung, liver, kidney, and pancreas, for use as alternatives to traditional organ transplantation. Biomedical researchers now face the challenge of adequately and efficiently recellularizing these organ scaffolds. Herein, an overview of whole organ decellularization and a thorough review of the current literature for whole organ recellularization are presented. The cell types, delivery methods, and bioreactors employed for recellularization are discussed along with commercial and clinical considerations, such as immunogenicity, biocompatibility, and Food and Drug Administartion regulation.

Introduction: Selection of a biomaterial-based scaffold that mimics native myocardial extracellular matrix (ECM) architecture can facilitate functional cell attachment and differentiation. Although decellularized myocardial ECM accomplishes these premises, decellularization processes may variably distort or degrade ECM structure., Materials and Methods: Two decellularization protocols (DP) were tested on porcine heart samples (epicardium, mid myocardium and endocardium). One protocol, DP1, was detergent-based (SDS and Triton X-100), followed by DNase I treatment. The other protocol, DP2, was focused in trypsin and acid with Triton X-100 treatments. Decellularized myocardial scaffolds were reseeded by embedding them in RAD16-I peptidic hydrogel with adipose tissue-derived progenitor cells (ATDPCs)., Results: Both protocols yielded acellular myocardial scaffolds (~82% and ~94% DNA reduction for DP1 and DP2, respectively). Ultramicroscopic assessment of scaffolds was similar for both protocols and showed filamentous ECM with preserved fiber disposition and structure. DP1 resulted in more biodegradable scaffolds (P = 0.04). Atomic force microscopy revealed no substantial ECM stiffness changes post-decellularization compared to native tissue. The Young's modulus did not differ between heart layers (P = 0.69) or decellularization protocols (P = 0.15). After one week, recellularized DP1 scaffolds contained higher cell density (236 ± 106 and 98 ± 56 cells/mm(2) for recellularized DP1 and DP2 scaffolds, respectively; P = 0.04). ATDPCs in both DP1 and DP2 scaffolds expressed the endothelial marker isolectin B4, but only in the DP1 scaffold ATDPCs expressed the cardiac markers GATA4, connexin43 and cardiac troponin T., Conclusions: In our hands, DP1 produced myocardial scaffolds with higher cell repopulation and promotes ATDPCs expression of endothelial and cardiomyogenic markers.

Purpose: To evaluate the in vivo biocompatibility of grafts composed of sheets of decellularized human corneal stroma with or without the recellularization of human adipose derived adult stem cells (h-ADASC) into the rabbit cornea., Methods: Sheets of human corneal stroma of 90 μm thickness were decellularized, and their lack of cytotoxicity was assayed. The recellularization was achieved by the injection of 2 × 10(5) labeled h-ADASC in the graft followed by five days of cell culture. The grafts were implanted in vivo into a stromal pocket at 50% depth. After a triple-masked three-month follow-up, the animals were euthanized and the biointegration of the graft, the viability of the stem cells and the expression of keratocan (human keratocyte-specific protein) were assessed., Results: The decellularized stromal sheets showed an intact extracellular matrix with a decellularization rate of 92.8% and an excellent recellularization capacity in vitro with h-ADASC. A complete and stable graft transparency was observed during the full follow-up, with absence of any clinical sign of rejection. The postmortem analysis demonstrated the survival of the transplanted human stem cells inside the graft and their differentiation into functional keratocytes, as assessed by the expression of human keratocan., Conclusions: We report a new model of lamellar keratoplasty that requires only a simple and safe procedure of liposuction and a donor allogeneic cornea to provide an optically transparent autologous stromal graft with excellent biocompatibility and integration into the host tissue in a rabbit model., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Engineering tissues with comparable structure, composition and mechanical functionality to native articular cartilage remains a challenge. One possible solution would be to decellularize xenogeneic articular cartilage in such a way that the structure of the tissue is maintained, and to then repopulate this decellularized matrix with human chondroprogenitor cells that will facilitate the reconstitution, maintenance and eventual turnover of the construct following implantation. The overall objective of this study was to develop a protocol to efficiently decellularize porcine articular cartilage grafts and to identify a methodology to subsequently repopulate such explants with human chondroprogenitor cells. To this end, channels were first introduced into cylindrical articular cartilage explants, which were then decellularized with a combination of various chemical reagents including sodium dodecyl sulfate (SDS) and nucleases. The decellularization protocol resulted in a ~90% reduction in porcine DNA content, with little observed effect on the collagen content and the collagen architecture of the tissue, although a near-complete removal of sulfated glycosaminoglycans (sGAG) and a related reduction in tissue compressive properties was observed. The introduction of channels did not have any detrimental effect on the biochemical or the mechanical properties of the decellularized tissue. Next, decellularized cartilage explants with or without channels were seeded with human infrapatellar fat pad derived stem cells (FPSCs) and cultured chondrogenically under either static or rotational conditions for 10 days. Both channeled and non-channeled explants supported the viability, proliferation and chondrogenic differentiation of FPSCs. The addition of channels facilitated cell migration and subsequent deposition of cartilage-specific matrix into more central regions of these explants. The application of rotational culture appeared to promote a less proliferative cellular phenotype and led to an increase in sGAG synthesis within the explants. Rotational culture also appeared to promote higher cell viability and led to a more even distribution of cells within the channels of decellularized explants. To conclude, this study describes an effective protocol for the decellularization of porcine articular cartilage grafts and a novel methodology for the partial recellularization of such explants with human stem cells. Decellularized soft tissue explants that maintain their native collagen architecture may represent promising scaffolds for musculoskeletal tissue engineering applications., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Organ transplantation can offer a curative option for patients with end stage organ failure. Unfortunately the treatment is severely limited by the availability of donor organs. Organ bioengineering could provide a solution to the worldwide critical organ shortage. The majority of protocols to date have employed the use of decellularization-recellularization technology of naturally occurring tissues and organs with promising results in heart, lung, liver, pancreas, intestine and kidney engineering. Successful decellularization has provided researchers with suitable scaffolds to attempt cell reseeding. Future work will need to focus on the optimization of organ specific recellularization techniques before organ bioengineering can become clinically translatable. This review will examine the current progress in organ bioengineering and highlight future challenges in the field.

The major goal of regenerative medicine is to determine experimental techniques that take maximal advantage of reparative processes that occur naturally in the animal body. Injection of mesenchymal stem cells into the core of a damaged tendon represents such an approach. Decellularization of native tendons as potential targets and seeding protocols are currently under investigation. The aim of our study was to manufacture a recellularized biocompatible scaffold from cadaveric tissue for use in total or partial tendon injuries. Results showed that it was possible to introduce proliferating cells into the core of a decellularized tendon to treat the scaffold with a collagen gel. The method was effective in maintaining scaffold extracellular matrix and for expressing collagen type I and cartilage oligomeric matrix protein by injecting mesenchymal stem cells., (Copyright © 2012 John Wiley & Sons, Ltd.)

The shortage of donor lungs for transplantation causes a significant number of patient deaths. The availability of laboratory engineered, functional organs would be a major advance in meeting the demand for organs for transplantation. The accumulation of information on biological scaffolds and an increased understanding of stem/progenitor cell behavior has led to the idea of generating transplantable organs by decellularizing an organ and recellularizing using appropriate cells. Recellularized solid organs can perform organ-specific functions for short periods of time, which indicates the potential for the clinical use of engineered solid organs in the future.   The present review provides an overview of progress and recent knowledge about decellularization and recellularization-based approaches for generating tissue engineered lungs. Methods to improve decellularization, maturation of recellularized lung, candidate species for transplantation and future prospects of lung bioengineering are also discussed.

We are now well entering the exciting era of stem cells. Potential stem cell therapy holds great promise for the treatment of many diseases such as stroke, traumatic brain injury, Alzheimer's disease, Parkinson's disease, amyotrophic lateral-sclerosis, myocardial infarction, muscular dystrophy, diabetes, and etc. It is generally believed that transplantation of specific stem cells into the injured tissue to replace the lost cells is an effective way to repair the tissue. In fact, organ transplantation has been successfully practiced in clinics for liver or kidney failure. However, the severe shortage of donor organs has been a major obstacle for the expansion of organ transplantation programs. Toward that direction, generation of transplantable organs using stem cells is a desirable approach for organ replacement and would be of great interest for both basic and clinical scientists. Here we review recent progress in the field of organ generation using various methods including single adult tissue stem cells, a blastocyst complementation system, tissue decellularization/recellularization and a combination of stem cells and tissue engineering.