BACKGROUND The growing size of the end stage renal disease (ESRD) population highlights the need for effective dialysis access. Exhausted native vascular access options have led to increased use of catheters and prosthetic shunts, which are both associated with high risks of access failure and infection. Emerging alternatives include tissue-engineered vascular grafts (TEVG). Here we present the endpoint results for 10 ESRD patients with the scaffold-free tissue-engineered vascular access produced from sheets of extracellular matrix produced in vitro by human cells in culture. METHODS Grafts were implanted as arteriovenous shunts in 10 ESRD patients with a complex history of access failure. Follow-up included ultrasound control of graft morphology and function, dialysis efficiency, access failure, intervention rate, as well as immunohistochemical analysis of graft structure. RESULTS One patient died of unrelated causes and three shunts failed to become useable access grafts during the 3-month maturation phase. The 12-month primary and secondary patency for the other six shunts was 86%. Survival of six shunts functioning as the vascular access was 22 ± 12 months with longest primary patency of 38.6 months. The dialysis event rate of 3.34 per patient-year decreased significantly with the use of this TEVG to 0.67. CONCLUSIONS This living autologous tissue-engineered vascular graft seems to be an alternative to synthetic vascular access options, exhibiting advantages of native arteriovenous fistula.

Several tissue engineering approaches are based on the ability of mesenchymal cells to endogenously synthesize an extracellular matrix (ECM) in vitro, which can be seen as a form of biomaterial. Accordingly, the inter-donor variability of cell-assembled extracellular matrix (CAM) production is a key parameter to understand in order to progress towards clinical applications, especially for autologous strategies. In this study, CAMs were produced, under good manufacturing process conditions, from skin fibroblasts of 21 patients as part of a clinical trial to evaluate a tissue-engineered vascular graft. The inter-donor variability of CAM strength, thickness, hydroxyproline, and glycosaminoglycan was substantial (coefficient of variability of 33%, 19%, 24%, and 19%, respectively), but a significant correlation was observed between all four properties (Pearson r: 0.43 to 0.70; p-value ≤ 0.05). A CAM matrisome analysis, performed by mass spectrometry, revealed the presence of 70 ECM-related proteins. Our study shows that the relative abundance of 16 proteins (15 non-collagenous) correlated with CAM thickness. These proteins also correlated with CAM hydroxyproline content, as well as 21 other proteins that included fibrillar collagens and non-collagenous proteins. However, data demonstrated that only the relative abundance of type I collagen subunit alpha-1 was correlated to CAM strength. This study is the most extensive evaluation of CAM inter-donor variability to date and will help tissue engineers working with this type of biomaterial to design strategies that take into account this variability, especially for autologous tissue manufacturing.

In the field of tissue engineering, many groups have come to rely on the extracellular matrix produced by cells as the scaffold that provides structure and strength to the engineered tissue. We have previously shown that sheets of Cell-Assembled extracellular Matrix (CAM), which are entirely biological yet robust, can be mass-produced for clinical applications using normal, adult, human fibroblasts. In this article, we demonstrate that CAM yarns can be generated with a range of physical and mechanical properties. We show that this material can be used as a simple suture to close a wound or can be assembled into fully biological, human, tissue-engineered vascular grafts (TEVGs) that have high mechanical strength and are implantable. By combining this truly "bio" material with a textile-based assembly, this original tissue engineering approach is highly versatile and can produce a variety of strong human textiles that can be readily integrated in the body. Statement of Significance Yarn of synthetic biomaterials have been turned into textiles for decades because braiding, knitting and weaving machines can mass-produce medical devices with a wide range of shapes and mechanical properties. Here, we show that robust, completely biological, and human yarn can be produced by normal cells in vitro. This yarn can be used as a simple suture material or to produce the first human textiles. For example, we produced a woven tissue-engineered vascular grafts with burst pressure, suture retention strength and transmural permeability that surpassed clinical requirements. This novel strategy holds the promise of a next generation of medical textiles that will be mechanically strong without any foreign scaffolding, and will have the ability to truly integrate into the host's body. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The fields of cardiovascular tissue engineering and regenerative medicine have experienced tremendous expansion and progress over the past 20 years. Strategies have focused on the use of cells, tissues, scaffolds, 3D-printing and numerous combinations of these three components to address both scientific questions and clinical needs. This chapter will focus on the use of biomaterials in the development of cardiac constructs, cell delivery methods, and engineering of artificial vessels and heart valves. While not an exhaustive list of topics within the field of cardiovascular tissue engineering, this list covers major areas of research advancement over the past few decades. Whether cardiac or peripherally focused, progress in these areas of research has the potential to impact tissue and organ function throughout the body. Because the cardiovascular system is dispersed throughout the human body, cardiovascular tissue engineering advancements can be seen as a rate-limiting factor for the development of thick tissues to repair or replace every critical physiological system. In addition, this chapter will also touch upon the prerequisites for continued success in cardiovascular tissue-engineered technology, discussing the future regulatory, clinical, manufacturing, and economic hurdles that scientists will need to overlay.

Cell-based therapies and the field of regenerative medicine have been heralded as the next pillar of medical care for more than 20 years.While public marrow and cord blood banking have been unequivocal successes, triumphs beyond blood diseases and cancer have been slow to arrive. With the passing of the 21st Century Cures Act, which was driven in large part by a desire to broaden the therapeutic reach of stem cells, it is an appropriate time to objectively review the clinical efficacy of stem cell therapies, and perhaps contemplate strategies to improve their clinical impact. Here, we discuss some of the underlying assumptions that have driven the field with respect to cell sourcing, mechanism of action, and immunoprivilege. The debate on cell sourcing has been an enduring topic in regenerative medicine. While much of the attention originally focused on the ethical considerations associated with pluripotent embryonic stem cells, the vast majority of clinical trials have utilized multipotent stem cells, derived from either autologous marrow or fat, or allogeneic cells harvested from a young, healthy, master donor. The autologous stem cell approach has the advantage of being immunologically matched but is potentially limited by the fact that the cells are usually harvested from older patients, and their potency may be more limited. Autologous stem cell approaches also have the disadvantage of being difficult to standardize and scale, with quality assurance infrastructure hurdles that may limit widespread use. Because stem cells have relatively few surface antigens and do not trigger acute immune responses, allogeneic transplants provide an attractive alternative, with the presumed benefit of being sourced from younger, healthier donors. Improved manufacturing margins also make allogeneic approaches an appealing model from a commercial perspective. As allogeneic cells engraft and differentiate, however, they can begin to express surface markers that are recognized by the immune system. So, while allogeneic stem cells may provide a powerful, short-term paracrine signal that may not trigger significant acute immune responses, their longterm effect diminishes along with their immunoprivileged status. With the benefit of nearly two decades of clinical hindsight using both autologous and allogeneic cells, three overarching conclusions are clear. First, stem cell injections are overwhelmingly safe. While there have been some isolated cases of ectopic tissue formation or teratoma formation, these complications have been extraordinarily rare. In fact, the most relevant risks associated with stem cell therapy are infection and stroke, which can generally be avoided with the proper manufacture and delivery of the cells. Second, long-term cell engraftment and survival is extremely low, with most studies demonstrating significantly less than 1% cell engraftment at the target site. Third, while many studies have demonstrated promising results and encouraging trends, none have demonstrated dramatic improvements in pivotal trials. The question, then, is what can be done to help give stem cell therapies the final push to achieve clear clinical impact? Some would argue that it is simply a matter of time to find the right combination of cell type, dosage, delivery strategy, and perhaps even the appropriate patient population. There is some evidence to support this “incremental progress” approach, as we have observed noteworthy successes in cartilage repair and graft-versus-host disease after more than 20 years of academic and clinical development and several failed clinical trials. It is puzzling, however, that despite tens of thousands of treatments across an exhaustive spectrum of clinical parameters, we have not been able to focus in on effective approaches to some of the main therapeutic targets for regenerative medicine (e.g., heart disease, stroke, and neurodegenerative diseases). Over the last decade, there has been an increased emphasis on short-term paracrine signaling as the primary mechanism of action for stem cell therapies.While it is clear that stem cells can release a milieu of growth factors and chemoattractants and can also play a role in immunomodulation, the field may have been too quick to abandon efforts to facilitate long-term cell survival. It seems plausible that, by increasing cell survival and engraftment, we may prolong the paracrine signaling that triggers native healing mechanisms and may also provide differentiated cells capable of driving a functional repair. The conundrum, of course, is that neither highmileage autologous stem cells nor nonimmunomatched allogeneic cells are well suited to impart this prolonged therapeutic effect. EDITORIAL

Despite an increasing list of clinically impactful products in cancer, wound care, and graft versus host disease, cellular therapeutics have yet to be fully embraced by large pharma and biotech. While there have been several high-profile investments in the past 5 years, the list of clinically and commercially successful products is still a short one. Here, we highlight some of the critical considerations to increase the likelihood of commercial success.

Event Abstract Back to Event Human ECM particles produced in vitro are injectable and support angiogenesis and adipogenesis in vivo Nicolas L'Heureux1, 2*, Adam D. Young3*, Nathalie Dusserre1*, Sonya B. Sonnenberg3*, Todd D. Johnson3*, Ricardo L. Rodriguez4*, Todd N. Mcallister1* and Karen L. Christman3* 1 Cytograft Tissue Engineering, United States 2 Université de Bordeaux, U1026 BioTis, France 3 University of California, San Diego, Department of Bioengineering, Sanford Consortium for Regenerative Medicine, United States 4 CosmeticSurg, United States Cell-synthesized ECM assembled by cultured cells has emerged as a promising biological scaffold for tissue engineering[1]. Tissue-engineered blood vessels built using rolled sheets of cell-assembled matrix (CAM) have shown unprecedented long-term patency in humans[2]. In this study, the CAM was mechanically processed into particles to produce an injectable form of the material suitable for many applications including aesthetic treatments. The goal of this study was to assess 1) the composition, 2) the injectability, 3) the stability, and 4) the host’s response to the CAM. Adult human dermal fibroblasts were cultured to promote ECM production and assembly in sheets for 8 weeks as previously described[3]. Dried sheets were milled into particles that passed through a #60 sieve (250µm mesh) and sterilized by gamma irradiation. Particles composition was analyzed using mass spectroscopy, immunolabeling and biochemical testing. Particle suspensions in saline were injected subcutaneously in nude mice along with two commercially available dermal fillers: Juvéderm Ultra XC® (cross-linked hyaluronic acid-based product) and Radiesse® (hydroxyapatite-based product). Each of 12 animals received four injections (upper shoulders and thighs) and was sacrificed after 2, 4, 8 and 12 weeks (4 biopsies per material per time point). Analysis of the ECM revealed that the particles contained numerous components including fibrillar and other collagens, elastic fiber components, fibrogenesis-associated and signaling components as well as glycosaminoglycans. The particle at 175 mg/ml produced a thick solution that could be injected through a 25 Ga needle. Subcutaneous injections were easily performed and, after diffusion of the excess injected fluids (≈24hrs), a palpable and localized bolus was observed. Histologically, the collagen rich particles were easily recognizable and generated a very mild inflammatory reaction with a generally thin fibrous layer around the injection site and only sparse immune cells. Rapid fibroblastic cell migration (2 weeks) was observed between the particles followed by progressive (2-12 week) perfusion by small blood vessels (also between particles). Adipocytes were also observed between particles within the injection bolus as early as 2 weeks but were more abundant as time went by. Cells did not appear to penetrate the particles and no signs of active degradation were observed. On the other hand, Juvéderm® did not form a well-delineated injection bolus and did not elicit an active remodeling process. Radiesse generated a very significant inflammatory response throughout the study period with abundant immune cell migration, giant cell formation, thicker fibrous capsule formation and extensive angiogenesis. These results clearly demonstrate the feasibility of injecting human CAM particles, at a clinically relevant concentration, using a clinically relevant system. Further more, these results support the idea that CAM is not targeted by the non-specific immune system. Finally, CAM particles supported both angiogenesis and adipogenesis. As a whole, these results illustrate the potential of this injectable material as a new tool for long-term tissue reconstruction and rejuvenation. While previous studies have shown great clinical successes using CAM-based tissue engineering[2], this is the first study to provide safety and remodeling data in a controlled setting. Marissa Peck, David Gebhart, Sunny Virk, Casey Mount, and Heinz Scheuenstuhl; Sophia Suarez; Rebecca Braden; Jessica Ungerleider; Dr. Kent Osborn; ASEE/NSF Engineering Innovation Fellows Program; National Science Foundation Graduate Research Fellowship ProgramReferences:[1] Peck, M., Dusserre, N., McAllister, T.N. & L'Heureux, N. Tissue engineering by self-assembly. Materials Today 14, 218-224 (2011).[2] McAllister, T.N., et al. Effectiveness of haemodialysis access with an autologous tissue-engineered vascular graft: a multicentre cohort study. Lancet 373, 1440-1446 (2009).[3] L'Heureux, N., et al. Human tissue-engineered blood vessels for adult arterial revascularization. Nat. Med. 12, 361-365 (2006). Keywords: Extracellular Matrix, Biocompatibility, Tissue Regeneration, acellullar matrix Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Regenerative medicine: biomaterials for control of tissue induction Citation: L'Heureux N, Young AD, Dusserre N, Sonnenberg SB, Johnson TD, Rodriguez RL, Mcallister TN and Christman KL (2016). Human ECM particles produced in vitro are injectable and support angiogenesis and adipogenesis in vivo. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.01758 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. * Correspondence: Dr. Nicolas L'Heureux, Cytograft Tissue Engineering, Novato, CA, United States, Email1 Dr. Adam D Young, University of California, San Diego, Department of Bioengineering, Sanford Consortium for Regenerative Medicine, La Jolla, CA, United States, adam.young08@gmail.com Dr. Nathalie Dusserre, Cytograft Tissue Engineering, Novato, CA, United States, Nathduss@yahoo.com Dr. Sonya B Sonnenberg, University of California, San Diego, Department of Bioengineering, Sanford Consortium for Regenerative Medicine, La Jolla, CA, United States, sseifnar@ucsd.edu Dr. Todd D Johnson, University of California, San Diego, Department of Bioengineering, Sanford Consortium for Regenerative Medicine, La Jolla, CA, United States, nso@ucsd.edu Dr. Ricardo L Rodriguez, CosmeticSurg, Baltimore, MD, United States, dr.rodriguez@me.com Dr. Todd N Mcallister, Cytograft Tissue Engineering, Novato, CA, United States, Todd@cytograft.com Dr. Karen L Christman, University of California, San Diego, Department of Bioengineering, Sanford Consortium for Regenerative Medicine, La Jolla, CA, United States, christman@eng.ucsd.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Nicolas L'Heureux Adam D Young Nathalie Dusserre Sonya B Sonnenberg Todd D Johnson Ricardo L Rodriguez Todd N Mcallister Karen L Christman Google Nicolas L'Heureux Adam D Young Nathalie Dusserre Sonya B Sonnenberg Todd D Johnson Ricardo L Rodriguez Todd N Mcallister Karen L Christman Google Scholar Nicolas L'Heureux Adam D Young Nathalie Dusserre Sonya B Sonnenberg Todd D Johnson Ricardo L Rodriguez Todd N Mcallister Karen L Christman PubMed Nicolas L'Heureux Adam D Young Nathalie Dusserre Sonya B Sonnenberg Todd D Johnson Ricardo L Rodriguez Todd N Mcallister Karen L Christman Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

With age, or after injury, subcutaneous adipose and conjunctive tissue loss can cause poor aesthetic appearance. Current injectable tissue fillers trigger foreign body responses that eventually lead to their degradation or encapsulation. The ideal dermal filler would provide initial structural support but also trigger a regenerative process and lead to the creation of a new permanent tissue. The goal of this project is to develop a new class of fillers that provides long‐term results by triggering the regeneration of a stable, living and vascularized adipose tissue.

The clinical and physiological issues specific to the coronary application will be introduced, as well as current medical treatments. The evolution of tissue-engineered vascular grafts will then be summarized, followed by a discussion on the use of TESA (TM) Finally, novel cardiac applications for TESA (TM) will be discussed.

An arteriovenous fistula is the current gold standard for chronic hemodialysis access. Tunneled catheters or synthetic grafts have poorer outcomes and much higher risks of infection. This report presents the first clinical use of a completely biological, allogeneic, nonliving, and human tissue-engineered vascular graft. Tissue-engineered vascular grafts built from allogeneic fibroblasts were implanted as shunts in three hemodialysis patients. The tissue-engineered vascular graft was stored for 9 months, without loss of mechanical strength. Implanted grafts showed no signs of degradation or dilation, with time points up to 11 months. Results of panel-reactive antibody and cross-reactivity tests showed no evidence of immune responses.

31 ©2013 Society For Biomaterials

The vast majority of arteriovenous grafts (AVG) have been constructed using expanded polytetrafluoroethylene (ePTFE). While ePTFE grafts have the advantage of being relatively inexpensive and easy to manufacture, distribute, ship, and store, their primary patency rates are disappointing when compared with the native AVF. Though use of arteriovenous fistulas (AVF) in the United States has increased substantially, approximately 25% of hemodialysis patients continue to use AVG as their vascular access. We present here a comprehensive review of biological grafts and their use in hemodialysis vascular access. In this review, we discuss the use of synthetics and then explore the evolution of biological grafts over the past 20 years, their clinical impact, and future challenges in widespread clinical use in hemodialysis patients. Provided are in depth descriptions of currently used nonbiological arteriovenous grafts and the recent approaches in increasing the patency of synthetic grafts. Recent technological advances using tissue-engineered AVGs have shown promise for patients receiving hemodialysis and their potential to provide an attractive, viable option for vascular access have been discussed.

Abstract Clinically available transcatheter aortic valve replacement (TAVR) technologies typically use chemically fixed bovine or equine tissues for the valve leaflets. While these fixed, xenogeneic materials have been used with success in devices placed by open surgical access, the tissue thickness (>500 microns) adds significantly to the overall crossing profile of the delivery device. Complications associated with device diameter are generally reported in at least 10-20% of clinical cases, making a reduced crossing profile one of the most critical targets for second generation TAVR devices. Another limitation associated with pericardium is fatigue induced delamination. Previously we have reported clinical results with a completely autologous tissue engineered vascular graft built using a process termed sheet-based tissue engineering. Using this approach, we were able to build small diameter blood vessels with supraphysiologic burst pressures, and demonstrated clinical durability with time points out to 3 years. Importantly, this tissue engineering approach requires no chemical fixation or exogenous biomaterials. More recently, we reported initial human use with an allogeneic version of the vessel. With time points out to 1 year, the allogeneic tissue engineered material demonstrated no evidence of immune reaction. This transition to an off-the shelf, allogeneic approach enables use the material in a variety of new clinical indications, including valve reconstruction. Valve leaflets built from a single sheet, demonstrated ultimate tensile strength in excess of that for bovine valve leaflets. Of note, the thickness of the sheet was less than 200 microns, roughly 30 percent that of bovine pericardium. The tissue can also be compressed, further reducing the thickness to approximately 75 microns. This thin, durable, single layered tissue can be assembled onto commercially available TAVR devices resulting in a reduction in crossing profile of approximately 2 Fr. The valve leaflets can be sutured easily, coapt normally, and can withstand arterial backpressure. Given the non-laminated structure of the tissue engineered leaflet, the lack of synthetic materials, and the durability demonstrated in other clinical indications, this approach may provide not only a reduced crossing profile, but also improved long term clinical results.

Cell-based therapies (CBTs) have been hailed for the last two decades as the next pillar of healthcare, yet the clinical and commercial potential of regenerative medicine has yet to live up to the hype. While recent analysis has suggested that regenerative medicine is maturing into a multibillion dollar industry, examples of clinical and commercial success are still relatively rare. With 30 years of laboratory and clinical efforts fueled by countless billions in public and private funding, one must contemplate why CBTs have not made a greater impact. The current regulatory environment, with its zero-risk stance, stymies clinical innovation while fueling a potentially risky medical tourism industry. Here, we highlight the challenges the US FDA faces and present talking points for an improved regulatory framework for autologous CBTs.