Human iPSCs Stretch to Improve Tissue-Engineered Vascular Grafts
2020; Elsevier BV; Volume: 26; Issue: 2 Linguagem: Inglês
10.1016/j.stem.2020.01.011
ISSN1934-5909
AutoresNadia O. Abutaleb, George A. Truskey,
Tópico(s)3D Printing in Biomedical Research
ResumoHuman induced pluripotent stem cells (hiPSCs) provide a potentially unlimited cell source for producing autologous tissue-engineered vascular grafts (TEVGs), which currently suffer from low mechanical strength. In this issue of Cell Stem Cell, Luo et al., 2020Luo J. Qin L. Zhao L. Gui L. Ellis M.W. Huang Y. Kural M.H. Clark J.A. Ono S. Wang J. et al.Tissue Engineered Vascular Grafts with Advanced Mechanical Strength from Human Induced Pluripotent Stem Cells.Cell Stem Cell. 2020; 26 (this issue): 251-261Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar describe optimized culture media and a mechanical stretching regimen to produce hiPSC-derived TEVGs with mechanical behavior similar to that of natural vessels. Human induced pluripotent stem cells (hiPSCs) provide a potentially unlimited cell source for producing autologous tissue-engineered vascular grafts (TEVGs), which currently suffer from low mechanical strength. In this issue of Cell Stem Cell, Luo et al., 2020Luo J. Qin L. Zhao L. Gui L. Ellis M.W. Huang Y. Kural M.H. Clark J.A. Ono S. Wang J. et al.Tissue Engineered Vascular Grafts with Advanced Mechanical Strength from Human Induced Pluripotent Stem Cells.Cell Stem Cell. 2020; 26 (this issue): 251-261Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar describe optimized culture media and a mechanical stretching regimen to produce hiPSC-derived TEVGs with mechanical behavior similar to that of natural vessels. With cardiovascular disease ranked as a leading cause of death worldwide, functional vascular grafts are an urgent clinical demand (Wu et al., 2018Wu J. Hu C. Tang Z. Yu Q. Liu X. Chen H. Tissue-engineered Vascular Grafts: Balance of the Four Major Requirements.Colloids Interface Sci. Commun. 2018; 23: 34-44Crossref Scopus (25) Google Scholar). Autologous and synthetic grafts are the clinical standard but suffer from several challenges. While often the best choice at present, autologous vascular grafts have limited availability, can undergo restenosis, and cause donor site morbidity (Pashneh-Tala et al., 2016Pashneh-Tala S. MacNeil S. Claeyssens F. The Tissue-Engineered Vascular Graft-Past, Present, and Future.Tissue Eng. Part B Rev. 2016; 22: 68-100Crossref PubMed Scopus (305) Google Scholar). Synthetic vascular grafts made of polytetrafluoroethylene and polyurethane suffer from long-term calcification and occlusion from thrombosis and are limited to large vessels where thrombosis is minimized (Pashneh-Tala et al., 2016Pashneh-Tala S. MacNeil S. Claeyssens F. The Tissue-Engineered Vascular Graft-Past, Present, and Future.Tissue Eng. Part B Rev. 2016; 22: 68-100Crossref PubMed Scopus (305) Google Scholar). These challenges have driven interest in tissue-engineered vascular grafts (TEVGs) as an attractive alternative to create functional blood vessel replacements in vitro that maintain function after implantation. TEVGs have been fabricated using primary human vascular smooth muscle cells (VSMCs), but these cells are limited in quantity and proliferation potential which affects extracellular matrix (ECM) synthesis and the mechanical strength of TEVGs (Poh et al., 2005Poh M. Boyer M. Solan A. Dahl S.L. Pedrotty D. Banik S.S. McKee J.A. Klinger R.Y. Counter C.M. Niklason L.E. Blood vessels engineered from human cells.Lancet. 2005; 365: 2122-2124Abstract Full Text Full Text PDF PubMed Scopus (166) Google Scholar). Human induced pluripotent stem cells (hiPSCs) present a potentially unlimited source of cells for TEVGs, but previously reported hiPSC-TEVGs suffer from limited differentiation of VSMCs (Atchison et al., 2017Atchison L. Zhang H. Cao K. Truskey G.A. A Tissue Engineered Blood Vessel Model of Hutchinson-Gilford Progeria Syndrome Using Human iPSC-derived Smooth Muscle Cells.Sci. Rep. 2017; 7: 8168Crossref PubMed Scopus (41) Google Scholar), which affects ECM synthesis, mechanical strength, and radial dilation after implantation (Elliott et al., 2019Elliott M.B. Ginn B. Fukunishi T. Bedja D. Suresh A. Chen T. Inoue T. Dietz H.C. Santhanam L. Mao H.Q. et al.Regenerative and durable small-diameter graft as an arterial conduit.Proc. Natl. Acad. Sci. USA. 2019; 116: 12710-12719Crossref PubMed Scopus (25) Google Scholar, Gui et al., 2016Gui L. Dash B.C. Luo J. Qin L. Zhao L. Yamamoto K. Hashimoto T. Wu H. Dardik A. Tellides G. et al.Implantable tissue-engineered blood vessels from human induced pluripotent stem cells.Biomaterials. 2016; 102: 120-129Crossref PubMed Scopus (67) Google Scholar, Sundaram et al., 2014Sundaram S. One J. Siewert J. Teodosescu S. Zhao L. Dimitrievska S. Qian H. Huang A.H. Niklason L. Tissue-engineered vascular grafts created from human induced pluripotent stem cells.Stem Cells Transl. Med. 2014; 3: 1535-1543Crossref PubMed Scopus (41) Google Scholar). In a study published in this issue of Cell Stem Cell, Luo et al., 2020Luo J. Qin L. Zhao L. Gui L. Ellis M.W. Huang Y. Kural M.H. Clark J.A. Ono S. Wang J. et al.Tissue Engineered Vascular Grafts with Advanced Mechanical Strength from Human Induced Pluripotent Stem Cells.Cell Stem Cell. 2020; 26 (this issue): 251-261Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar addressed these concerns by combining optimized culture media with cyclic mechanical stretching to produce hiPSC-TEVGs with high mechanical strength. The work represents a significant step forward for the field in the ability to generate functional TEVGs using hiPSC-derived cells. Luo et al., 2020Luo J. Qin L. Zhao L. Gui L. Ellis M.W. Huang Y. Kural M.H. Clark J.A. Ono S. Wang J. et al.Tissue Engineered Vascular Grafts with Advanced Mechanical Strength from Human Induced Pluripotent Stem Cells.Cell Stem Cell. 2020; 26 (this issue): 251-261Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar began by optimizing a method to produce functional hiPSC-derived VSMCs for TEVG production. hiPSC-VSMCs expressed VSMC markers, including α-smooth muscle actin, calponin, smooth muscle myosin heavy chain 11, and smoothelin, and relevant ECM markers, including collagen 1, collagen 3, and elastin. Cell yield from this differentiation method was ∼9-fold higher than the group’s previously reported approach, and VSMC marker expression was comparable to that in primary VSMCs. Based on previous work in which TEVGs cultured in media containing transforming growth factor-β1 (TGF-β1) and platelet-derived growth factor-BB (PDGF-BB) had limited mechanical strength (Gui et al., 2016Gui L. Dash B.C. Luo J. Qin L. Zhao L. Yamamoto K. Hashimoto T. Wu H. Dardik A. Tellides G. et al.Implantable tissue-engineered blood vessels from human induced pluripotent stem cells.Biomaterials. 2016; 102: 120-129Crossref PubMed Scopus (67) Google Scholar), the authors modified the TEVG culture medium to enhance differentiation. hiPSC-VSMCs seeded onto polyglycolic acid (PGA) meshes and cultured in media containing TGF-β1 deposited more collagen, while hiPSC-VSMCs on PGA meshes cultured in media containing PDGF-BB had a higher proportion of apoptotic cells, indicating a detrimental effect on hiPSC-VSMC survival. Thus, TEVG medium containing TGF-β1 without PDGF-BB was chosen for optimal TEVG maturation. To further mature the hiPSC-VSMCs, Luo et al., 2020Luo J. Qin L. Zhao L. Gui L. Ellis M.W. Huang Y. Kural M.H. Clark J.A. Ono S. Wang J. et al.Tissue Engineered Vascular Grafts with Advanced Mechanical Strength from Human Induced Pluripotent Stem Cells.Cell Stem Cell. 2020; 26 (this issue): 251-261Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar found that, as with primary VSMCs, uniaxial mechanical stretching of hiPSC-VSMCs enhanced VSMC and ECM marker expression, collagen deposition, focal adhesion marker expression, and adherens junction marker expression. Stretching also increased formation of filamentous actin bundles and promoted actin alignment perpendicular to the direction of stretching as expected for VSMCs. Stretched VSMCs produced higher levels of ATP, increased glucose consumption, and expressed higher levels of genes related to glucose metabolism. These benefits were further enhanced when the stretching regimen was coupled with the optimized TGF-β1-containing culture medium. Next, Luo et al., 2020Luo J. Qin L. Zhao L. Gui L. Ellis M.W. Huang Y. Kural M.H. Clark J.A. Ono S. Wang J. et al.Tissue Engineered Vascular Grafts with Advanced Mechanical Strength from Human Induced Pluripotent Stem Cells.Cell Stem Cell. 2020; 26 (this issue): 251-261Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar used the optimized hiPSC-VSMC differentiation protocol, culture medium, and mechanical maturation regimen to fabricate TEVGs. PGA scaffolds were seeded with hiPSC-VSMCs and cultured statically for 1 week, then pulsatile radial stress was applied for 7 weeks. At the end of this regimen, hiPSC-TEVG opaqueness, rupture pressure, and suture retention strength were comparable to that of native human saphenous veins used for autologous grafts and higher than human umbilical arteries (HUAs). hiPSC-TEVG wall thickness and collagen content was comparable to that in both HUAs and primary human TEVGs. hiPSC-TEVGs were also highly cellularized, expressed VSMC marker levels similar to those of native HUAs, and did not show any evidence of calcium deposition. They did not contain mature ELN fibers, which is consistent with previous reports of TEVGs made with both primary and hiPSC-derived VSMCs (Gui et al., 2016Gui L. Dash B.C. Luo J. Qin L. Zhao L. Yamamoto K. Hashimoto T. Wu H. Dardik A. Tellides G. et al.Implantable tissue-engineered blood vessels from human induced pluripotent stem cells.Biomaterials. 2016; 102: 120-129Crossref PubMed Scopus (67) Google Scholar, Niklason et al., 1999Niklason L.E. Gao J. Abbott W.M. Hirschi K.K. Houser S. Marini R. Langer R. Functional arteries grown in vitro.Science. 1999; 284: 489-493Crossref PubMed Scopus (1434) Google Scholar). In comparison with previously reported hiPSC-TEVGs, these engineered vessels exhibit marked improvement in suture retention strength, nearly two-fold increase in rupture pressure, and ∼3.5-fold increase in collagen content (Gui et al., 2016Gui L. Dash B.C. Luo J. Qin L. Zhao L. Yamamoto K. Hashimoto T. Wu H. Dardik A. Tellides G. et al.Implantable tissue-engineered blood vessels from human induced pluripotent stem cells.Biomaterials. 2016; 102: 120-129Crossref PubMed Scopus (67) Google Scholar, Sundaram et al., 2014Sundaram S. One J. Siewert J. Teodosescu S. Zhao L. Dimitrievska S. Qian H. Huang A.H. Niklason L. Tissue-engineered vascular grafts created from human induced pluripotent stem cells.Stem Cells Transl. Med. 2014; 3: 1535-1543Crossref PubMed Scopus (41) Google Scholar). To evaluate in vivo potential, hiPSC-TEVGs were implanted as interpositional grafts into the abdominal aorta of nude rats. After 30 days, explanted grafts were all patent with minimal thrombosis and no evidence of rupture, aberrant deformation, radial dilation, longitudinal elongation, or wall thickening. No significant differences were observed in mechanical properties of explanted TEVGs compared with TEVGs prior to implantation, including maximum modulus, ultimate tensile strength, failure strain, and contractile function. Explanted TEVGs showed no signs of calcification, maintained cellularity, expressed VSMC markers, and contained abundant collagen. However, mature ELN fibers were not detected and require further study. Contrary to pre-implantation TEVGs, most cells in explanted TEVGs were not positive for proliferation marker Ki67, indicating a shift to quiescence after implantation. Very few CD68+ cells were observed near explanted TEVGs, indicating minimal to no macrophage infiltration. To resist thrombosis and improve biocompatibility, TEVGs should promote luminal endothelialization (Wu et al., 2018Wu J. Hu C. Tang Z. Yu Q. Liu X. Chen H. Tissue-engineered Vascular Grafts: Balance of the Four Major Requirements.Colloids Interface Sci. Commun. 2018; 23: 34-44Crossref Scopus (25) Google Scholar). Notably, while implanted grafts were not pre-endothelialized, some portions of the luminal surface of explanted TEVGs showed coverage by host endothelial cells. Successful endothelialization is needed for longer-term function of the TEVGs. The study by Luo et al., 2020Luo J. Qin L. Zhao L. Gui L. Ellis M.W. Huang Y. Kural M.H. Clark J.A. Ono S. Wang J. et al.Tissue Engineered Vascular Grafts with Advanced Mechanical Strength from Human Induced Pluripotent Stem Cells.Cell Stem Cell. 2020; 26 (this issue): 251-261Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar represents the most mechanically robust hiPSC-TEVGs reported to date, with properties approaching those of native human vessels. A high-yield differentiation protocol combined with optimized culture medium and a cyclic stretching regimen enhanced mechanical properties of the engineered grafts far beyond the field standard. This mechanical strength contributed to the success of the implanted TEVGs, showing high patency, no dilation or elongation, and maintained morphology and function after 30 days. To take the work a step further, Luo et al., 2020Luo J. Qin L. Zhao L. Gui L. Ellis M.W. Huang Y. Kural M.H. Clark J.A. Ono S. Wang J. et al.Tissue Engineered Vascular Grafts with Advanced Mechanical Strength from Human Induced Pluripotent Stem Cells.Cell Stem Cell. 2020; 26 (this issue): 251-261Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar included data showing successful differentiation of VSMCs from an HLA-engineered universally immunocompatible hiPSC line, with differentiated cells exhibiting VSMC and ECM marker expression, contractile function, and collagen deposition. Fully developing a ready supply of immune-compatible cells would further advance this technology. Future studies should compare the gene expression profile of the hiPSC-VSMCs in the TEVGs with primary VSMCs to identify which pathways may need to be stimulated to more closely mimic the in vivo state. Because of the importance of the construct, these hiPSC-VSMCs should be examined in TEVGs made with synthetic or ECM scaffold. Nonetheless, this work represents an important advance for functional TEVGs using hiPSC-derived cells and illuminates the possibility of large-scale production of hiPSC-TEVGs as an effective clinical therapy. Tissue-Engineered Vascular Grafts with Advanced Mechanical Strength from Human iPSCsLuo et al.Cell Stem CellJanuary 16, 2020In BriefLuo et al. generated tissue-engineered vascular grafts (TEVGs) using human induced pluripotent stem cell (hiPSC)-derived vascular smooth muscle cells. These hiPSC-derived TEVGs displayed mechanical strength comparable to that of native vessels used clinically as vascular grafts and maintained excellent patency and mechanical function following implantation into a rat model. Full-Text PDF Open Archive
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