The extracellular matrix is a biologically critical entity that has historically been poorly understood. Here we discuss how new tools for characterizing matrix composition and function enable us to ...design and deliver advanced matrices in vitro, to optimize regeneration, and in vivo, within a variety of tissues and organs.
The extracellular matrix is a biologically critical entity that has historically been poorly understood. Here we discuss how new tools for characterizing matrix composition and function enable us to design and deliver advanced matrices in vitro, to optimize regeneration, and in vivo, within a variety of tissues and organs.
Bioengineered human blood vessels Niklason, Laura E.; Lawson, Jeffrey H.
Science (American Association for the Advancement of Science),
10/2020, Letnik:
370, Številka:
6513
Journal Article
Recenzirano
Evolution of bioengineered blood vessels
Biotechnology approaches to repair and replace arteries have been under development for more than a century. Early synthetic approaches used rubber-based ...replacements, which then evolved into the use of polymer fabrics and, more recently, into biological approaches that permit the growth of blood vessels in the laboratory. Niklason and Lawson review the scientific and technological advances that allow the regeneration of a patient's own blood vessels. The authors discuss how blood vessel cells, when combined with suitable substrates for tissue growth under conditions that mimic human physiology, can produce functional bioengineered arteries. These biological approaches pave the way to advancing how vascular disease is managed and treated in the future.
Science
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BACKGROUND
Vascular replacement and repair for the treatment of atherosclerotic disease, infection, and traumatic injury are some of the most commonly performed surgical procedures in the Western world. In the United States alone, hundreds of thousands of coronary and peripheral arteries are repaired, replaced, or bypassed every year. But despite the enormity of the clinical need for engineered arterial replacements, the equally enormous simultaneous challenges of immune acceptance, requisite tissue mechanics, low thrombogenicity, and immediate availability have made the broad clinical application of engineered arteries quite difficult to achieve. In this regard, recent years have seen the fusion of cell biology, physiology, and engineering to now allow for the creation of human tissues that can truly function in the setting of vascular repair and replacement.
ADVANCES
For a biological engineered artery to function successfully without requiring immunosuppression, the following objectives should be met: (i) The engineered artery should have an extracellular matrix of sufficient quality to provide suitable tensile, suture retention, and rupture strength properties. A focus on production of suitable amounts of high-quality cross-linked vascular collagens type I and III is probably necessary for any biological engineered artery to be successful. (ii) To minimize risks of inflammation, foreign-body response, and immune recognition, the vascular tissue matrix should be of human origin and without substantial synthetic material additives or artificial covalent cross-linking. (iii) If the engineered artery is cellular, even if the cells are nonviable, those cells should be autologous to prevent immune recognition, degradation, and aneurysm formation in the implanted vessels. (iv) Once implanted, the engineered arteries should have the potential to be remodeled, repopulated, and rejuvenated by the host. (v) For small-caliber or low-flow arterial bypass applications, it is likely that a suitable nonthrombogenic luminal surface is required. This surface may be either cellular or biochemical, but it should prevent blood coagulation contact activation, platelet adhesion and activation, and thrombosis in the arterial system.
OUTLOOK
Guided by the design criteria above, engineered blood vessels have been developed by several groups that have progressed to clinical trials. Recent clinical studies have demonstrated the feasibility of using human tissue–engineered blood vessels in the settings of vascular trauma, peripheral arterial disease, and vascular access for hemodialysis. Engineered arteries reaching the clinical domain have been composed of autologous cells or allogeneic cells, or have been engineered from allogeneic cells or tissues and then decellularized. Vascular functionality in patients has been demonstrated in both low-pressure environments (pediatric cardiac surgery) and high-pressure environments (peripheral arterial surgery in adults).
Autologous cell approaches have shown some promise, particularly in clinical settings of venous reconstruction and low pressure and in pediatric populations. However, scaling production of engineered arteries to tens of thousands of vessels per year, as would be needed to treat arterial atherosclerosis at large scale, presents enormous logistical challenges if autologous cell sources are used. Hence, it is likely that future successes of engineered arteries will employ allogeneic human cells or cell banks to generate tissues at clinically relevant scales, and suitable strategies will be required to prevent adaptive immunity and rejection of these vessels. Furthermore, next-generation techniques such as three-dimensional bioprinting of both cells and matrix may one day allow vessel production at accelerated speeds, possibly producing usable tissues in hours or days, rather than weeks or months. Microvascular and cardiac tissue engineering are also making important strides, pointing toward a future that could enable revascularization of solid organs. The evolution of scientific thinking and approaches that have brought us to this point is summarized in this review.
An engineered human artery cultured from human vascular cells and implanted into a patient.
Immunostaining for smooth muscle (red), progenitor cells (green), and cell nuclei (blue) shows extensive cellular repopulation of the engineered vessel. Engineered cells were implanted into the patient for 4 years. The layer of red-staining cells at the bottom of the image shows the repopulated engineered vessel wall. Blue staining at the top shows the nuclei of skin cells.
Since the advent of the vascular anastomosis by Alexis Carrel in the early 20th century, the repair and replacement of blood vessels have been key to treating acute injuries, as well as chronic atherosclerotic disease. Arteries serve diverse mechanical and biological functions, such as conducting blood to tissues, interacting with the coagulation system, and modulating resistance to blood flow. Early approaches for arterial replacement used artificial materials, which were supplanted by polymer fabrics in recent decades. With recent advances in the engineering of connective tissues, including arteries, we are on the cusp of seeing engineered human arteries become mainstays of surgical therapy for vascular disease. Progress in our understanding of physiology, cell biology, and biomanufacturing over the past several decades has made these advances possible.
Abstract Current limitations of exogenous scaffolds or extracellular matrix based materials have underlined the need for alternative tissue-engineering solutions. Scaffolds may elicit adverse host ...responses and interfere with direct cell–cell interaction, as well as assembly and alignment of cell-produced ECM. Thus, fabrication techniques for production of scaffold-free engineered tissue constructs have recently emerged. Here we report on a fully biological self-assembly approach, which we implement through a rapid prototyping bioprinting method for scaffold-free small diameter vascular reconstruction. Various vascular cell types, including smooth muscle cells and fibroblasts, were aggregated into discrete units, either multicellular spheroids or cylinders of controllable diameter (300–500 μm). These were printed layer-by-layer concomitantly with agarose rods, used here as a molding template. The post-printing fusion of the discrete units resulted in single- and double-layered small diameter vascular tubes (OD ranging from 0.9 to 2.5 mm). A unique aspect of the method is the ability to engineer vessels of distinct shapes and hierarchical trees that combine tubes of distinct diameters. The technique is quick and easily scalable.
Using biodegradable scaffold and a biomimetic perfusion system, our lab has successfully engineered small-diameter vessel grafts using endothelial cells (ECs) and smooth muscle cells (SMCs) obtained ...from vessels in various species. However, translating this technique into humans has presented tremendous obstacles due to species and age differences. SMCs from elderly persons have limited proliferative capacity and a reduction in collagen production, which impair the mechanical strength of engineered vessels. As an alternative cell source, adult human bone marrow-derived mesenchymal stem cells (hMSCs) were studied for their ability to differentiate into SMCs in culture plates as well as in a bioreactor system. In the former setting, immunofluorescence staining showed that MSCs, after induction for 14 days, expressed smooth muscle α-actin (SMA) and calponin, early and mid-SMC phenotypic markers, respectively. In the latter setting, vessel walls were constructed with MSC-derived SMCs. Various factors (i.e., matrix proteins, soluble factors, and cyclic strain) in the engineering system were further investigated for their effects on hMSC cell proliferation and differentiation into SMCs. Based on a screening of multiple factors, the engineering system was optimized by dividing the vessel culture into proliferation and differentiation phases. The vessel walls engineered under the optimized conditions were examined histologically and molecularly, and found to be substantially similar to native vessels. In conclusion, bone marrow-derived hMSCs can serve as a new cell source of SMCs in vessel engineering. Optimization of the culture conditions to drive SMC differentiation and matrix production significantly improved the quality of the hMSC-derived engineered vessel wall.--Gong, Z., Niklason, L. E. Small-diameter human vessel wall engineered from bone marrow-derived mesenchymal stem cells (hMSCs).
Advances in standards of care have extended the life expectancy of patients with kidney failure. However, options for chronic vascular access for haemodialysis - an essential part of kidney ...replacement therapy - have remained unchanged for decades. The high morbidity and mortality associated with current vascular access complications highlights an unmet clinical need for novel techniques in vascular access and is driving innovation in vascular access care. The development of devices, biological approaches and novel access techniques has led to new approaches to controlling fistula geometry and manipulating the underlying cellular and molecular pathways of the vascular endothelium, and influencing fistula maturation and formation through the use of external mechanical methods. Innovations in arteriovenous graft materials range from small modifications to the graft lumen to the creation of completely novel bioengineered grafts. Steps have even been taken to create new devices for the treatment of patients with central vein stenosis. However, these emerging therapies face difficult hurdles, and truly creative approaches to vascular access need resources that include well-designed clinical trials, frequent interaction with regulators, interventionalist education and sufficient funding. In addition, the heterogeneity of patients with kidney failure suggests it is unlikely that a 'one-size-fits-all' approach for effective vascular access will be feasible in the current environment.
Arterial tissue-engineering techniques that have been reported previously typically involve long waiting times of several months while cells from the recipient are cultured to create the engineered ...vessel. In this study, we developed a different approach to arterial tissue engineering that can substantially reduce the waiting time for a graft. Tissue-engineered vessels (TEVs) were grown from banked porcine smooth muscle cells that were allogeneic to the intended recipient, using a biomimetic perfusion system. The engineered vessels were then decellularized, leaving behind the mechanically robust extracellular matrix of the graft wall. The acellular grafts were then seeded with cells that were derived from the intended recipient—either endothelial progenitor cells (EPC) or endothelial cell (EC)—on the graft lumen. TEV were then implanted as end-to-side grafts in the porcine carotid artery, which is a rigorous testbed due to its tendency for graft occlusion. The EPC- and EC-seeded TEV all remained patent for 30 d in this study, whereas the contralateral control vein grafts were patent in only 3/8 implants. Going along with the improved patency, the cell-seeded TEV demonstrated less neointimal hyperplasia and fewer proliferating cells than did the vein grafts. Proteins in the mammalian target of rapamycin signaling pathway tended to be decreased in TEV compared with vein grafts, implicating this pathway in the TEV's resistance to occlusion from intimal hyperplasia. These results indicate that a readily available, decellularized tissue-engineered vessel can be seeded with autologous endothelial progenitor cells to provide a biological vascular graft that resists both clotting and intimal hyperplasia. In addition, these results show that engineered connective tissues can be grown from banked cells, rendered acellular, and then used for tissue regeneration in vivo.
Summary Background For patients with end-stage renal disease who are not candidates for fistula, dialysis access grafts are the best option for chronic haemodialysis. However, polytetrafluoroethylene ...arteriovenous grafts are prone to thrombosis, infection, and intimal hyperplasia at the venous anastomosis. We developed and tested a bioengineered human acellular vessel as a potential solution to these limitations in dialysis access. Methods We did two single-arm phase 2 trials at six centres in the USA and Poland. We enrolled adults with end-stage renal disease. A novel bioengineered human acellular vessel was implanted into the arms of patients for haemodialysis access. Primary endpoints were safety (freedom from immune response or infection, aneurysm, or mechanical failure, and incidence of adverse events), and efficacy as assessed by primary, primary assisted, and secondary patencies at 6 months. All patients were followed up for at least 1 year, or had a censoring event. These trials are registered with ClinicalTrials.gov , NCT01744418 and NCT01840956. Findings Human acellular vessels were implanted into 60 patients. Mean follow-up was 16 months (SD 7·6). One vessel became infected during 82 patient-years of follow-up. The vessels had no dilatation and rarely had post-cannulation bleeding. At 6 months, 63% (95% CI 47–72) of patients had primary patency, 73% (57–81) had primary assisted patency, and 97% (85–98) had secondary patency, with most loss of primary patency because of thrombosis. At 12 months, 28% (17–40) had primary patency, 38% (26–51) had primary assisted patency, and 89% (74–93) had secondary patency. Interpretation Bioengineered human acellular vessels seem to provide safe and functional haemodialysis access, and warrant further study in randomised controlled trials. Funding Humacyte and US National Institutes of Health.
Over the past 40 years, remarkable advances have been made in our understanding of successful blood vessel regeneration, starting with the failures of early tissue-engineered vascular grafts designed ...using isolated components or molecules, such as collagen gels. The vascular tissue engineers are today better educated and have steered ongoing research developments toward clinical developments of more complete vascular grafts that replicate the multitude of specialized arterial aspects required for function.
Yang et al.1 generate tissue engineered blood vessels from hiPSC-derived smooth muscle cells harboring a mutation found in Loeys-Dietz syndrome. In vitro and in vivo data from these vessels provide ...new insight into the molecular physiology of aortic aneurysms and may create a paradigm for understanding a suite of vascular diseases.
Yang et al. generate tissue engineered blood vessels from hiPSC-derived smooth muscle cells harboring a mutation found in Loeys-Dietz syndrome. In vitro and in vivo data from these vessels provide new insight into the molecular physiology of aortic aneurysms and may create a paradigm for understanding a suite of vascular diseases.
The development of a tracheal graft to replace long-segment defects has thwarted clinicians and engineers alike for over 100 years. To better understand the challenges facing this field today, we ...have consolidated all published reports of engineered tracheal grafts used to repair long-segment circumferential defects in humans, from the first in 1898 to the most recent in 2018, totaling 290 clinical cases. Distinct trends emerge in the types of grafts used over time, including repair using autologous fascia, rigid tubes of various inert materials, and pretreated cadaveric allografts. Our analysis of maximum clinical follow-up, as a proxy for graft performance, revealed that the Leuven protocol has a significantly longer clinical follow-up time than all other methods of airway reconstruction. This method involves transplanting a cadaveric tracheal allograft that is first prevascularized heterotopically in the recipient. We further quantified graft-related causes of mortality, revealing failure modes that have been resolved, and those that remain a hurdle, such as graft mechanics. Finally, we briefly summarize recent preclinical work in tracheal graft development. In conclusion, we synthesized top clinical care priorities and design criteria to inform and inspire collaboration between engineers and clinicians toward the development of a functional tracheal replacement graft.
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