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Columbus, OH, United States

Lee Y.-U.,Tissue Engineering Program | Lee A.Y.,Tissue Engineering Program | Humphrey J.D.,Yale University | Rausch M.K.,Yale University
Biorheology | Year: 2015

BACKGROUND: Deep vein thrombosis and the risk of pulmonary embolism are significant causes of morbidity and mortality. Much remains unclear, however, about the mechanisms by which a venous thrombus initiates, progresses, or resolves. In particular, there is a pressing need to characterize the evolving mechanical properties of a venous thrombus for its mechanical integrity is fundamental to many disease sequelae. OBJECTIVE: The primary goal of the present study was to initiate a correlation between evolving histological changes and biomechanical properties of venous thrombus. METHODS: We employed an inferior vena cava ligation model in mice to obtain cylindrical samples of thrombus that were well suited for mechanical testing and that could be explanted at multiple times following surgery. Using uniaxial micro-mechanical testing, we collected stress-stretch data that were then fit with a microstructurally-inspired material model before submitting the samples to immunohistological examination. RESULTS: We found that venous thrombus underwent a radially inward directed replacement of fibrin with collagen between 2 weeks and 4 weeks of development, which was accompanied by the infiltration of inflammatory and mesenchymal cells. These histological changes correlated with a marked increase in material stiffness. CONCLUSIONS: We demonstrated that 2 to 4 week old venous thrombus undergoes drastic remodeling from a fibrin-dominated mesh to a collagen-dominated microstructure and that these changes are accompanied by dramatic changes in biomechanical behavior. © 2015 - IOS Press and the authors. Source


Wu Y.,Tissue Engineering Program | Wen F.,National University of Singapore | Gouk S.S.,National University of Singapore | Lee E.H.,Tissue Engineering Program | Kuleshova L.,National University of Singapore
Cryo letters | Year: 2015

BACKGROUND: The development of vitrification strategy for cell-biomaterial constructs, particularly biologically inspired nanoscale materials and hydrogels mimicking the in vivo environment is an active area. A cryopreservation strategy mimicking the in vivo environment for cell-hydrogel constructs may enhance cell proliferation and biological function.OBJECTIVE: To demonstrate the efficacy of vitrification as a platform technology involving tissue engineering and human mesenchymal stem cells (hMSCs).MATERIALS AND METHODS: Microcarriers made from alginate coated with chitosan and collagen are used. Conventional freezing and vitrification were compared. The vitrification strategy includes 10 min step-wise exposure to a vitrification solution (40% v/v EG, 0.6M sucrose) and immersion into liquid nitrogen.RESULTS: Confocal imaging of live/dead staining of hMSCs cultured on the surface of microcarriers demonstrated that vitrified cells had excellent appearance and prolonged spindle shape morphology. The proliferation ability of post-vitrified cells arbitrated to protein Ki-67 gene expression was not significantly different in comparison to untreated control, while that of post-freezing cells was almost lost. The ability of hMSCs cultured on the surface of microcarriers to proliferate has been not affected by vitrification and it was significantly better after vitrification than after conventional freezing during continuous culture. Collagen II related mRNA expression by 4 weeks post-vitrification and post-freezing showed that ability to differentiate into cartilage was sustained during vitrification and reduced during conventional freezing. No significant difference was found between control and vitrification groups only.CONCLUSION: Vitrification strategy coupled with advances in hMSC-expansion platform that completely preserves the ability of stem cells to proliferate and subsequently differentiate allows not only to reach a critical cell number, but also demonstrate prospects for effective utilization and transportation of cells with their support system, creating demand for novel biodegradable materials. Source


Hibino N.,Yale University | Mejias D.,Yale University | Pietris N.,Yale University | Dean E.,Yale University | And 4 more authors.
FASEB Journal | Year: 2015

The first clinical trial of tissue-engineered vascular grafts (TEVGs) identified stenosis as the primary cause of graft failure. In this study, we aimed to elucidate the role of the host immune response in the development of stenosis using a murine model of TEVG implantation. We found that the C.B-17 wild-type (WT) mouse (control) undergoes a dramatic stenotic response, which is nearly completely abolished in the immunodeficient SCID/beige (bg) variant. SCID mice, which lack an adaptive immune system due to the absence of T and B lymphocytes, experienced rates of stenosis comparable to WT controls (average luminal diameter, WT: 0.0716 0.035 mm, SCID: 0.13760.032mm, SCID/bg: 0.80460.039mm; P<0.001). The bg mutation is characterized by NK cell and platelet dysfunction, and systemic treatment of WT mice with either NK cell-neutralizing (anti-NK 1.1 antibody) or antiplatelet (aspirin/Plavix [clopidogrel bisulfate]; Asp/Pla) therapy achieved nearly half the patency observed in the SCID/bg mouse (NK Ab: 0.356 ± 0.151 mm, Asp/Pla: 0.452 ± 0.130 mm). Scaffold implantation elicited a blunted immune response in SCID/bg mice, as demonstrated by macrophage number and mRNA expression of proinflammatory cytokines in TEVG explants. Implicating the initial innate immune response as a critical factor in graft stenosis may provide a strategy for prognosis and therapy of second-generation TEVGs. © FASEB. Source


Tara S.,Tissue Engineering Program | Tara S.,Heart Center | Kurobe H.,Tissue Engineering Program | Kurobe H.,Heart Center | And 14 more authors.
Arteriosclerosis, Thrombosis, and Vascular Biology | Year: 2015

Objective - Despite successful translation of bioresorbable vascular grafts for the repair of congenital heart disease, stenosis remains the primary cause of graft failure. In this study, we investigated the efficacy of long-term treatment with the antiplatelet drugs, aspirin and cilostazol, in preventing stenosis and evaluated the effect of these drugs on the acute phase of inflammation and tissue remodeling. Approach and Results - C57BL/6 mice were fed a drug-mixed diet of aspirin, cilostazol, or normal chow during the course of follow-up. Bioresorbable vascular grafts, composed of poly(glycolic acid) mesh sealed with poly(l-lactide-co-ε-caprolactone), were implanted as inferior vena cava interposition conduits and followed up for 2 weeks (n=10 per group) or 24 weeks (n=15 per group). Both aspirin and cilostazol suppressed platelet activation and attachment onto the grafts. On explant at 24 weeks, well-organized neotissue had developed, and cilostazol treatment resulted in 100% graft patency followed by the aspirin (67%) and no-treatment (60%) groups (P<0.05). Wall thickness and smooth muscle cell proliferation in the neotissue of the cilostazol group were decreased when compared with that of the no-treatment group at 24 weeks. In addition, cilostazol was shown to have an anti-inflammatory effect on neotissue at 2 weeks by regulating the recruitment and activation of monocytes. Conclusions - Cilostazol prevents stenosis of bioresorbable vascular graft in a mouse inferior vena cava implantation model up to 24 weeks and is accompanied by reduction of smooth muscle cell proliferation and acute inflammation. © 2015 American Heart Association, Inc. Source

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