Esophageal tissue engineering:A new approach for esophageal replacement

A number of congenital and acquired disorders require esophageal tissue replacement.Various surgical techniques,such as gastric and colonic interposition,are standards of treatment,but frequently complicated by stenosis and other problems.Regenerative medicine approaches facilitate the use of biological constructs to replace or regenerate normal tissue function.We review the literature of esophageal tissue engineering,discuss its implications,compare the methodologies that have been employed and suggest possible directions for the future.Medline,Embase,the Cochrane Library,National Research Register and ClinicalTrials.gov databases were searched with the following search terms:stem cell and esophagus,esophageal replacement,esophageal tissue engineering,esophageal substitution.Reference lists of papers identified were also examined and experts in this field contacted for further information.All full-text articles in English of all potentially relevant abstracts were reviewed.Tissue engineering has involved acellular scaffolds that were either transplanted with the aim of being repopulated by host cells or seeded prior to transplantation.When acellular scaffolds were used to replace patch and short tubular defects they allowed epithelial and partial muscular migration whereas when employed for long tubular defects the results were poor leading to an increased rate of stenosis and mortality.Stenting has been shown as an effective means to reduce stenotic changes and promote cell migration,whilst omental wrapping to induce vascularization of the construct has an uncertain benefit.Decellularized matrices have been recently suggested as the optimal choice for scaffolds,but smart polymers that will incorporate signalling to promote cell-scaffold interaction may provide a more reproducible and available solution.Results in animal models that have used seeded scaffolds strongly suggest that seeding of both muscle and epithelial cells on scaffolds prior to implantation is a prerequisite for complete esophageal replacement.Novel approaches need to be designed to allow for peristalsis and vascularization in the engineered esophagus.Although esophageal tissue engineering potentially offers a real alternative to conventional treatments for severe esophageal disease,important barriers remain that need to be addressed.

Tissue engineering for neuromuscular disorders of the gastrointestinal tract

The digestive tract is designed for the optimal processing of food that nourishes all organ systems.The esophagus,stomach,small bowel,and colon are sophisticated neuromuscular tubes with specialized sphincters that transport ingested food-stuffs from one region to another.Peristaltic contractions move ingested solids and liquids from the esophagus into the stomach;the stomach mixes the ingested nutrients into chyme and empties chyme from the stomach into the duodenum.The to-and-fro movement of the small bowel maximizes absorption of fat,protein,and carbohydrates.Peristaltic contractions are necessary for colon function and defecation.

Adenosine-treated bioprinted muscle constructs prolong cell survival and improve tissue formation

It is crucial to maintaining the viability of biofabricated human-sized tissues to ensure their successful survival and function after transplantation.Adenosine is a purine nucleoside that has the function to suppress cellular metabolism and has been previously proposed as a method to prolong cell viability under hypoxia.In this study,we optimized the dose concentration of adenosine for incorporation into bioprinted constructs to preserve long-term cell viability in vitro.Our results showed that muscle cells(C2C12)containing 6,7,or 8 mM adenosine maintained high cell viability for 20 days under hypoxic conditions(0.1%O2),whereas cells without adenosine treatment showed 100%cell death after 11 days.After 20 days under hypoxic conditions,muscle cells treated with adenosine proliferated and differentiated when transferred to normoxic conditions.From these adenosine concentrations,6 mM was picked as the optimized adenosine concentration for further investigations due to its most effective results on improving cell viability.The bioprinted muscle constructs containing adenosine(6 mM)maintained high cell viability for 11 days under hypoxic conditions,while the control constructs without adenosine had no live cells.For in vivo validation,the bioprinted constructs with adenosine implanted under the dorsal subcutaneous space in mice,showed the enhanced formation of muscle tissue with minimal central necrosis and apoptosis,when compared to the constructs without adenosine.These positive in vitro and in vivo results demonstrate that the use of adenosine is an effective approach to preventing the challenge of hypoxia-induced necrosis in bioprinted tissues for clinical translation.

Bioreactor design and validation for manufacturing strategies in tissue engineering

The fields of regenerative medicine and tissue engineering offer new therapeutic options to restore,maintain or improve tissue function following disease or injury.To maximize the biological function of a tissue-engineered clinical product,specific conditions must be maintained within a bioreactor to allow the maturation of the product in preparation for implantation.Specifically,the bioreactor should be designed to mimic the mechanical,electrochemical and biochemical environment that the product will be exposed to in vivo.Real-time monitoring of the functional capacity of tissue-engineered products during manufacturing is a critical component of the quality management process.The present review provides a brief overview of bioreactor engineering considerations.In addition,strategies for bioreactor automation,in-line product monitoring and quality assurance are discussed.

Urine-derived stem cells:A novel and versatile progenitor source for cell-based therapy and regenerative medicine

Engineered functional organs or tissues,created with autologous somatic cells and seeded on biodegradable or hydrogel scaffolds,have been developed for use in individualswith tissue damage suffered fromcongenital disorders,infection,irradiation,or cancer.However,in those patients,abnormal cells obtained by biopsy fromthe compromised tissue could potentially contaminate the engineered tissues.Thus,an alternative cell source for construction of the neo-organ or functional recovery of the injured or diseased tissues would be useful.Recently,we have found stem cells existing in the urine.These cells are highly expandable,and have self-renewal capacity,paracrine properties,and multi-differentiation potential.As a novel cell source,urine-derived stem cells(USCs)provide advantages for cell therapy and tissue engineering applications in regeneration of various tissues,particularly in the genitourinary tract,because they originate from the urinary tract system.Importantly,USCs can be obtained via a non-invasive,simple,and low-cost approach and induced with high efficiency to differentiate into three dermal cell lineages.

Multi-Organ Pathogenesis and Therapeutic Strategies for Cystic Fibrosis

Cystic Fibrosis (CF) is the most common lethal autosomal inherited disorder that affects all races and ethnicities in the United States. However, it is mostly predominant in the Caucasian populace accounting for about 80% of all CF cases. CF most severe complication can be referred to as pulmonary bronchiectasis and infections of the airways, nonetheless, the devastating effects of the disease have far-reaching consequences beyond lung damage. CF is a heterogeneous disease that is caused by mutations in Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. The impairment or absence of this gene can affect multiple organs and systems and is characterized not only by chronic lung blockage, infections, and inflammation but also by exocrine gland dysfunction, intestinal obstruction, liver pathology, elevated sweat chloride concentration, and in males, infertility due to the congenital bilateral absence of the vas deferens. To this end, we briefly explore the pathological effects of CF and how CF mediates the destruction of several critical organs in the body and some of the gene therapeutical approaches such as gene editing and viral-based strategies available for the treatment of this multi-organ disease.

肿瘤坏死因子-α抑制剂己酮可可碱对糖尿病大鼠阴茎海绵体RhoA/Rho激酶信号通路的影响

目的:研究糖尿病大鼠阴茎海绵体组织中RhoA/Rho激酶信号通路改变以及肿瘤坏死因子(TNF)吨抑制剂己酮可可碱(PTX)对该信号通路和阴茎勃起功能的影响。方法:SD大鼠分为对照组、糖尿病组和糖尿病药物干预组;高脂喂养联合低剂量链脲佐菌素注射诱导糖尿病;腹腔埋置微渗透泵持续慢性给药;在体记录阴茎海绵体窦内压(ICP):ELISA检测血清TNF-α浓度;Western blot检测海绵体组织中内皮型一氧化氮合酶(eNOS)和神经型一氧化氮合酶(nNOS)以及RhoA/Rho激酶信号通路分子的蛋白表达水平。结果:与糖尿病组比,糖尿病药物干预组血清TNF-α浓度明显下降(P<0.01),阴茎海绵体组织中RhoA、ROCK1和p-MYPT1表达下调(P<0.05),eNOS和nNOS表达增加(P<0.05),阴茎ICP指数显著升高(P<0.05)。结论:TNF-α促进阴茎海绵体组织RhoA/Rho激酶信号通路的激活与表达上调,参与糖尿病性勃起功能障碍的发病机制:PTX对糖尿病大鼠的勃起功能有保护作用。

De novo malignancies after liver transplantation: The effect of immunosuppression-personal data and review of literature

BACKGROUND Immunosuppression has undoubtedly raised the overall positive outcomes in the post-operative management of solid organ transplantation. However, long-term exposure to immunosuppression is associated with critical systemic morbidities. De novo malignancies following orthotopic liver transplants (OLTs) are a serious threat in pediatric and adult transplant individuals. Data from different experiences were reported and compared to assess the connection between immunosuppression and de novo malignancies in liver transplant patients. AIM To study the role of immunosuppression on the incidence of de novo malignancies in liver transplant recipients. METHODS A systematic literature examination about de novo malignancies and immunosuppression weaning in adult and pediatric OLT recipients was described in the present review. Worldwide data were collected from highly qualified institutions performing OLTs. Patient follow-up, immunosuppression discontinuation and incidence of de novo malignancies were reported. Likewise, the review assesses the differences in adult and pediatric recipients by describing the adopted immunosuppression regimens and the different type of diagnosed solid and blood malignancy.RESULTS Emerging evidence suggests that the liver is an immunologically privileged organ able to support immunosuppression discontinuation in carefully selected recipients. Malignancies are often detected in liver transplant patients undergoing daily immunosuppression regimens. Post-transplant lymphoproliferative diseases and skin tumors are the most detected de novo malignancies in the pediatric and adult OLT population, respectively. To date, immunosuppression withdrawal has been achieved in up to 40% and 60% of well-selected adult and pediatric recipients, respectively. In both populations, a clear benefit of immunosuppression weaning protocols on de novo malignancies is difficult to ascertain because data have not been specified in most of the clinical experiences. CONCLUSION The selected populations of tolerant pediatric and adult liver transplant recipients greatly benefit from immunosuppression weaning. There is still no strong clinical evidence on the usefulness of immunosuppression withdrawal in OLT recipients on malignancies. An interesting focus is represented by the complete reconstitution of the immunological pathways that could help in decreasing the incidence of de novo malignancies and may also help in treating liver transplant patients suffering from cancer.

Liver bioengineering:Current status and future perspectives

The present review aims to illustrate the strategies that are being implemented to regenerate or bioengineer livers for clinical purposes.There are two general pathways to liver bioengineering and regeneration.The first consists of creating a supporting scaffold,either synthetically or by decellularization of human or animal organs,and seeding cells on the scaffold,where they will mature either in bioreactors or in vivo.This strategy seems to offer the quickest route to clinical translation,as demonstrated by the development of liver organoids from rodent livers which were repopulated with organ specific cells of animal and/or human origin.Liver bioengineering has potential for transplantation and for toxicity testing during preclinical drug development.The second possibility is to induce liver regeneration of dead or resected tissue by manipulating cell pathways.In fact,it is well known that the liver has peculiar regenerative potential which allows hepatocyte hyperplasia after amputation of liver volume.Infusion of autologous bone marrow cells,which aids in liver regeneration,into patients was shown to be safe and to improve their clinical condition,but the specific cells responsible for liver regeneration have not yet been determined and the underlying mechanisms remain largely unknown.A complete understanding of the cell pathways and dynamics and of the functioning of liver stem cell niche is necessary for the clinical translation of regenerative medicine strategies.As well,it will be crucial to elucidate the mechanisms through which cells interact with the extracellular matrix,and how this latter supports and drives cell fate.

Selective serotonin re-uptake inhibitor sertraline inhibits bone healing in a calvarial defect model

Bone wound healing is a highly dynamic and precisely controlled process through which damaged bone undergoes repair and complete regeneration. External factors can alter this process, leading to delayed or failed bone wound healing. The findings of recent studies suggest that the use of selective serotonin reuptake inhibitors(SSRIs) can reduce bone mass, precipitate osteoporotic fractures and increase the rate of dental implant failure. With 10% of Americans prescribed antidepressants, the potential of SSRIs to impair bone healing may adversely affect millions of patients' ability to heal after sustaining trauma. Here, we investigate the effect of the SSRI sertraline on bone healing through pre-treatment with(10 mg·kg^(-1) sertraline in drinking water, n = 26) or without(control, n = 30) SSRI followed by the creation of a 5-mm calvarial defect. Animals were randomized into three surgical groups:(a) empty/sham,(b) implanted with a DermaMatrix scaffold soak-loaded with sterile PBS or(c) DermaMatrix soak-loaded with542.5 ng BMP2. SSRI exposure continued until sacrifice in the exposed groups at 4 weeks after surgery. Sertraline exposure resulted in decreased bone healing with significant decreases in trabecular thickness, trabecular number and osteoclast dysfunction while significantly increasing mature collagen fiber formation. These findings indicate that sertraline exposure can impair bone wound healing through disruption of bone repair and regeneration while promoting or defaulting to scar formation within the defect site.

Stress urinary incontinence in women and cell therapy: What can we expect from the future?

Stress urinary incontinence(SUI)is a common disorder that affects a large number of women and their quality of life.The aim of SUI therapy is to restore the existing urethral function via physical therapy,biofeedback,pelvic floor rehabilitation,pharmacological therapy,bulking agents and surgical approaches.Currently,the gold standard for the management of SUI is the tensionfree vaginal sling,which provides structural support to the female urethra.However,even minimally invasive surgical procedure such as"slings"carries risks for the patients,lost efficacy over the time and has long-term complications.For this reason,new therapeutic modalities are needed.Cell therapy has been emerged as an alternative to be used on the treatment of different diseases.The use of stem cells as a therapeutic option for SUI is an attractive alternative because,theoretically,injected cells could restore functional muscle cells and aid in sphincter closure in women with sphincterassociated incontinence.This study aims to review the current literature regarding evidences for using stem cell therapy on stress urinary incontinence in women.

Skin 3D Bioprinting. Applications in Cosmetology

Tissue engineering has been used for the treatment of several skin diseases and lesions;however, tissue engineering and regenerative medicine also have a huge potential in cosmetology. They include skin substitutes, cell therapy and wound-healing treatments based on biomaterial-based replacements and 3D systems. This review focuses on the bioprinting technology and how it can improve skin functions, restoring pigmentation or helping hair follicles to develop.

Biocompatibility Pathways in Tissue-Engineering Templates

组织工程通过系统结合分子信号和力学信号对特定靶细胞进行有意可控刺激以组建新的组织,通常需要借助由生物材料构建的结构传递这些信号,并对生成的组织块塑形。这些结构之前被称为支架,如今被更准确地命名为模板,其规范却难以定义,主要因为该规范必须涉及为细胞组建新组织提供适宜的微环境,以及细胞与模板材料的相互作用符合构建新型可存活组织的需求。这些特点统称为生物相容性。然而,传统生物相容性的理论和公认机制(大多通过可移植的医学装置进行实验得出)不足以解释在组织工程过程中的现象。本文作者近期在特定的基于材料、生物学的途径方面重新定义了生物相容性。本文以上述途径为前提讨论了组织工程生物相容性的机制。

Leading Approaches to Vascularize Kidney Constructs in Tissue Engineering

There is an unprecedented need for new treatments for renal failure,as the incidence of this disease is increasing disproportionately to advancements in therapies.Current treatments are limited by the availability of viable organs,for which there is a worldwide lack.These treatment modalities also require a substantial amount of infrastructure,significantly limiting the access to care in most countries.Kidney tissue engineering approaches promise to develop alternative solutions that address many of the inadequacies in current care.Although many advancements have been made—primarily in the past decade—in biofabrication and whole-organ tissue engineering,many challenges remain.One major hindrance to the progress of current tissue engineering approaches is establishing successful vascularization of developed engineered tissue constructs.This review focuses on the recent advancements that address the vascular challenge,including the biofabrication of vasculature,whole-organ engineering through decellularization and recellularization approaches,microscale organogenesis,and vascularization using organoids in the context of kidney tissue engineering.We also highlight the specific challenges that remain in developing successful strategies capable of clinical translation.

Composite hepatocellular and hemangiosarcomatous tumor: The prognosis is determined by the sarcomatous component

Nowadays, mixed liver tumors are more frequently diagnosed due to better imaging, advanced immunohistochemistry (IHC) staining techniques and better knowledge of hepatic tumorigene- sis [1–3] . Such tumors represent a mosaic of components with dis- tinct histogenesis and carcinogenic pathways. As their occurrence in the liver is very rare, their behavior and natural history are difficult to determine, and their management remains empirical. An uncommon case of a composite tumor harboring hepatocellular carcinoma (HCC) and hepatic hemangiosarcoma (HHS) components in a liver transplant (LT) recipient is reported herein.

Kidney regeneration: Where we are and future perspectives

In 2012,about 16487 people received kidney transplants in the United States,whereas 95022 candidates were on the waiting list by the end of the year.Despite advances in renal transplant immunology,approximately 40%of recipients will die or lose graft within10 years.The limitations of current therapies for renal failure have led researchers to explore the development of modalities that could improve,restore,or replace the renal function.The aim of this paper is to describe a reasonable approach for kidney regeneration and review the current literature regarding cell sources and mechanisms to develop a bioengineering kidney.Due to kidneys peculiar anatomy,extracellular matrix based scaffolds are rational starting point for their regeneration.The perfusion of detergents through the kidney vasculature is an efficient method for delivering decellularizing agents to cells and for removing of cellular material from the tissue.Many efforts have focused on the search of a reliable cell source to provide enrichment for achieving stable renal cell systems.For an efficient bioengineered kidney,these cells must be attached to the organ and then maturated into the bioractors,which simulates the human body environment.A functional bioengineered kidney is still a big challenge for scientists.In the last ten years we have got many improvements on the field of solid organ regeneration;however,we are still far away from the main target.Currently,regenerative centers worldwide have been striving to find feasible strategies to develop bioengineered kidneys.Cell-scaffold technology gives hope to end-stage renal disease patients who struggle with morbidity and mortality due to extended periods on dialysis or immunosupression.The potential of bioengineered organ is to provide a reliable source of organs,which can be refunctionalized and transplanted.

SNL fibroblast feeder layers support derivation and maintenance of human induced pluripotent stem cells

Induced pluripotent stem(iPS) cells can be derived from human somatic cells by cellular reprogramming.This technology provides a potential source of non-controversial therapeutic cells for tissue repair,drug discovery,and opportunities for studying the molecular basis of human disease.Normally,mouse embryonic fibroblasts(MEFs) are used as feeder layers in the initial derivation of iPS lines.The purpose of this study was to determine whether SNL fibroblasts can be used to support the growth of human iPS cells reprogrammed from somatic cells using lentiviral expressed reprogramming factors.In our study,iPS cells expressed common pluripotency markers,displayed human embryonic stem cells(hESCs) morphology and unmethylated promoters of NANOG and OCT4.These data demonstrate that SNL feeder cells can support the derivation and maintenance of human iPS cells.

Skin bioprinting:the future of burn wound reconstruction?

Burns are a significant cause of trauma,and over the years,the focus of patient care has shifted from just survival to facilitation of improved functional outcomes.Typically,burn treatment,especially in the case of extensive burn injuries,involves surgical excision of injured skin and reconstruction of the burn injury with the aid of skin substitutes.Conventional skin substitutes do not contain all skin cell types and do not facilitate recapitulation of native skin physiology.Three-dimensional(3D)bioprinting for reconstruction of burn injuries involves layer-by-layer deposition of cells along with scaffolding materials over the injured areas.Skin bioprinting can be done either in situ or in vitro.Both these approaches are similar except for the site of printing and tissue maturation.There are technological and regulatory challenges that need to be overcome for clinical translation of bioprinted skin for burn reconstruction.However,the use of bioprinting for skin reconstruction following burns is promising;bioprinting will enable accurate placement of cell types and precise and reproducible fabrication of constructs to replace the injured or damaged sites.Overall,3D bioprinting is a very transformative technology,and its use for wound reconstruction will lead to a paradigm shift in patient outcomes.In this review,we aim to introduce bioprinting,the different stages involved,in vitro and in vivo skin bioprinting,and the various clinical and regulatory challenges in adoption of this technology.

Decellularized extracellular matrix mediates tissue construction and regeneration

Contributing to organ formation and tissue regeneration,extracellular matrix(ECM)constituents provide tissue with three-dimensional(3D)structural integrity and cellular-function regulation.Containing the crucial traits of the cellular microenvironment,ECM substitutes mediate cell–matrix interactions to prompt stem-cell proliferation and differentiation for 3D organoid construction in vitro or tissue regeneration in vivo.However,these ECMs are often applied generically and have yet to be extensively developed for specific cell types in 3D cultures.Cultured cells also produce rich ECM,particularly stromal cells.Cellular ECM improves 3D culture development in vitro and tissue remodeling during wound healing after implantation into the host as well.Gaining better insight into ECM derived from either tissue or cells that regulate 3D tissue reconstruction or organ regeneration helps us to select,produce,and implant the most suitable ECM and thus promote 3D organoid culture and tissue remodeling for in vivo regeneration.Overall,the decellularization methodologies and tissue/cell-derived ECM as scaffolds or cellular-growth supplements used in cell propagation and differentiation for 3D tissue culture in vitro are discussed.Moreover,current preclinical applications by which ECM components modulate the wound-healing process are reviewed.

自体组织重建膀胱可用于膀胱成形术患者

外伤可导致膀胱的损伤甚至摘除，部分先天异常的儿童，如膀胱外翻、脊髓脊膜膨出或者尿道瓣膜发育延迟患儿，会出现高压、高渗、低顺应性膀胱。这些患者在药物治疗无效后常需要膀胱成形术，因此器官修复或移植势在必行。