Purpose:Tissue-engineered vascular grafts (TEVG) have shown promise in advancing vascular reconstructions. However, precise in vivo implantation is challenging, and it is unclear how deviations in location and size affect hemodynamics. This study aims to 1) compare preoperative designs and postoperative anatomies of TEVG in an in vivo study to evaluate discrepancies and 2) investigate the impact of graft displacement and size on hemodynamics by virtually simulating implantation scenarios that are informed by in vivo postoperative results. Methods:Designed and postoperative geometries of four porcine aortas were compared to measure the mismatch in implantation location and graft shape. These results informed a virtual TEVG implantation study. TEVG location, orientation, and size were varied to investigate the effects on the final aorta shape and hemodynamics. Anastomosis of TEVG was simulated using finite element modeling. Key hemodynamic metrics were obtained from virtual implantations and actual postoperative anatomies using computational fluid dynamics. Results:Our in vivo study showed that TEVGs can experience up to 6.9 mm displacement and a 38° rotational shift post-implantation, leading to discrepancies in pressure drop (2.5 mmHg, 50%) and time-averaged wall shear stress (7.2 Pa, 72%) compared to predictions. Virtual TEVG implantation showed that peak systolic pressure drop (PSPD) was most sensitive to translation in the inferior-superior direction and rotation about the anterior-posterior axis. Size mismatch had a greater impact on time-averaged wall shear stress (TAWSS) (85%) than PSPD (23%). Additionally, virtual anastomosis simulations improved aortic shape predictions by 27.5%. Conclusion:Our results highlight the sensitivity of key hemodynamic metrics to graft implantation location and size mismatch. By quantifying displacement ranges and their impacts during surgery, surgeons can make informed decisions.

OBJECTIVE:Airway collapse is a life-threatening complication of tracheal grafting, yet no definitive strategy to prevent this exists. Composite tracheal grafts (CTG) that incorporate biodegradable splints can promote structural support and host integration. This study evaluated how electrospun splint composition modulates submucosal remodeling and collagen deposition in partially decellularized tracheal grafts (PDTG). STUDY DESIGN:Case-control study using a microsurgical mouse model. SETTING:Research institute affiliated with a tertiary pediatric hospital. METHODS:PDTG were orthotopically implanted onto mice trachea. To create CTG, electrospun splints composed of polyglycolic acid (PGA), poly(l-lactide-co-ε-caprolactone) (PLCL), or a PGA/PLCL hybrid were integrated onto PDTG. Grafts were harvested at 2 weeks. Splint resorption, submucosal thickness, and collagen deposition were accessed via quantification of Masson's trichrome images. Cellular infiltration and fibroblast recruitment were evaluated using DAPI and vimentin immunofluorescence, respectively. Quantification was completed in the midgraft region using ImageJ, and statistical analysis was performed using GraphPad Prism 10. RESULTS:Splints demonstrated clear differences in the degree of resorption at 2 weeks. PGA splints demonstrated the greatest resorption, PLCL the lowest, and hybrid PGA/PLCL an intermediate degree. Compared to PDTG alone, PGA and PLCL splints resulted in decreased submucosal thickness, while collagen deposition was increased only in the PGA splint composition. Vimentin staining confirmed fibroblast recruitment into the submucosal layer, which qualitatively varied with biomaterial type. CONCLUSION:Electrospun biodegradable splints exhibited degradation dynamics and influenced tissue remodeling of engineered tracheal grafts. Material selection may improve graft integration and long-term viability.

Background: Rotator cuff repair surgeries often face high failure rates, particularly in cases involving tendon degeneration. Traditional repair techniques and devices frequently fail to adequately restore a healthy native enthesis and strong tendon-bone integration. This study investigates the efficacy of a novel, fully synthetic, bioresorbable nanofiber scaffold in restoring the native enthesis and enhancing the biomechanical properties and overall success of rotator cuff repairs, particularly in the context of chronically degenerated tendons. Methods: This study used an ovine model to simulate chronic tendon degeneration with subsequent rotator cuff transection and repair. All repairs were performed using the standard double-row configuration with suture tape; half of the repairs were augmented with the bioresorbable nanofiber scaffold. Nondestructive biomechanical testing was conducted to assess the strength of the repair constructs, followed by histological analysis of all tendon samples to evaluate tissue regeneration and integration at the repair site. Results: Results demonstrated that the scaffold group achieved significantly improved biomechanical properties (peak force, peak stress, equilibrium force, and equilibrium stress) compared to the suture only group, indicating enhanced repair strength and native enthesis restoration. Scaffold samples exhibited significantly decreased cross-sectional areas (ie, less fibrosis) which were similar to healthy tendons. Histological findings indicated the scaffold did not impede re-establishment of Sharpey-like fibers at the tendon insertion. Conclusion: This study provides compelling evidence that the use of a fully synthetic, bioresorbable nanofiber scaffold in rotator cuff repair significantly improves biomechanical outcomes and enthesis regeneration. These improvements were achieved while retaining close to native tendon thickness. The findings suggest that this scaffold represents a significant advancement in rotator cuff repair technology, offering a promising solution to enhance repair strength and quality of bone-tendon integration, especially in challenging cases of tendon degeneration.

Adipose tissue is crucial for medical applications such as tissue reconstruction, cosmetic procedures, and correcting soft tissue deformities. Significant advances in the use of adipose tissue have been achieved through Coleman's studies in fat grafting, which gained widespread acceptance due to its effectiveness and safety. Despite its benefits, adipose tissue grafting faces several limitations, including high absorption rates due to insufficient support or anchorage, replacement by fibrous tissue, migration from the intended site, and loss of the initial desired morphology post-administration. To counteract these constraints, there is a need for improved grafting techniques that enhance the predictability and consistency of outcomes. Biomaterials are extensively used in tissue engineering to support cell adhesion, proliferation, and growth. Both natural and synthetic materials have shown promise in creating suitable microenvironments for adipose tissue regeneration. PLGA, a synthetic copolymer, is particularly notable for its biocompatibility, biodegradability, and tunable mechanical properties. Here, we describe a protocol using milled electrospun poly(lactic-co-glycolic acid) (PLGA) fibers combined with lipoaspirated tissue to create a fibrous slurry for injection. By pulverizing PLGA fiber mats to create fiber fragments with increased pore size and porosity, we can influence key cellular responses and enhance the success of adipose tissue-grafting procedures. This approach improves anchorage and support for adipocytes, thereby increasing cell viability. This method aims to enhance vascularity, perfusion, and volume retention in adipose tissue grafts, which addresses many of the limitations of current approaches to adipose tissue grafting and holds promise for more consistent and successful outcomes.

Background and Purpose: The results of the preclinical study of a novel polymer coil in treatment of elastase induced aneurysms will be presented in this paper. Material and Methods: We induced 16 aneurysms in 16 New Zealand white rabbits at the origin of the right common carotid artery at the brachiocephalic trunk. Newly developed polymer coils in both groups for six aneurysms each and platinum coils for two aneurysms each were used. Control angiographies followed in both groups immediately after coiling as well as in the first eight animals 30 days after intervention (30 days group) and in the other eight animals 90 days after (90 days group). An explanation and histological evaluation of the treated aneurysms followed. Results: The 12 animals in which the aneurysms were treated with polymer coils showed a complete occlusion (grade IV) in only 6 out of 12 aneurysms (50%), an almost complete occlusion (grade III) in 5 out of 12 (42%) and an incomplete occlusion in the treatment of one aneurysm (8%). Histologically, we observed a significantly more pronounced inflammatory response and neoangiogenesis in aneurysms treated with polymer coils only in the 30 days group. Conclusion: Most difficulties and concerns with the polymer coils were related to the flexibility and detachment behaviour. Therefore, and due to the technical challenges of delivery, the novel polymer coil cannot be considered an alternative to the current platinum coils.

Objective(s): The complexity of aortic arch reconstruction due to diverse 3dimensional geometrical abnormalities is a major challenge. This study introduces 3-dimensional printed tissue-engineered vascular grafts, which can fi t patient- specific fi c dimensions, optimize hemodynamics, exhibit antithrombotic and anti- infective properties, and accommodate growth. Methods: We procured cardiac magnetic resonance imaging with 4-dimensional fl ow for native porcine anatomy (n 1 / 4 10), from which we designed tissue- engineered vascular grafts for the distal aortic arch, 4 weeks before surgery. An optimal shape of the curved vascular graft was designed using computer-aided design informed by computational fl uid dynamics analysis. Grafts were manufactured and implanted into the distal aortic arch of porcine models, and postoperative cardiac magnetic resonance imaging data were collected. Pre- and postimplant hemodynamic data and histology were analyzed. Results: Postoperative magnetic resonance imaging of all pigs with 1:1 ratio of polycaprolactone and poly-L-lactide-co-s-caprolactone s-caprolactone demonstrated no specific dilatation or stenosis of the graft, revealing a positive growth trend in the graft area from the day after surgery to 3 months later, with maintaining a similar shape. The peak wall shear stress of the polycaprolactone/poly-L-lactide-co-s-caprolactone s-caprolactone graft portion did not change significantly fi cantly between the day after surgery and 3 months later. Immunohistochemistry showed endothelization and smooth muscle layer formation without calcification fi cation of the polycaprolactone/poly-L-lactide-co-s-caprolactone s-caprolactone graft. Conclusions: Our patient-specific fi c polycaprolactone/poly-L-lactide-co-s-caprolac- s-caprolac- tone tissue-engineered vascular grafts demonstrated optimal anatomical fi t maintaining ideal hemodynamics and neotissue formation in a porcine model. This study provides a proof of concept of patient-specific fi c tissue-engineered vascular grafts for aortic arch reconstruction. (JTCVS Open 2024;18:209-20)

Autologous adipose tissue is commonly used for tissue engraftment for the purposes of soft tissue reconstruction due to its relative abundance in the human body and ease of acquisition using liposuction methods. This has led to the adoption of autologous adipose engraftment procedures that allow for the injection of adipose tissues to be used as a "filler" for correcting cosmetic defects and deformities in soft tissues. However, the clinical use of such methods has several limitations, including high resorption rates and poor cell survivability, which lead to low graft volume retention and inconsistent outcomes. Here, we describe a novel application of milled electrospun poly(lactic-co-glycolic acid) (PLGA) fibers, which can be co-injected with adipose tissue to improve engraftment outcomes. These PLGA fibers had no significant negative impact on the viability of adipocytes in vitro and did not elicit long-term proinflammatory responses in vivo. Furthermore, co-delivery of human adipose tissue with pulverized electrospun PLGA fibers led to significant improvements in reperfusion, vascularity, and retention of graft volume compared to injections of adipose tissue alone. Taken together, the use of milled electrospun fibers to enhance autologous adipose engraftment techniques represents a novel approach for improving upon the shortcomings of such methods.

Background:Patient-specific, 3-dimensional printed, tissue engineered vascular grafts (3DTEVGs) are manufactured to optimize hemodynamic performance and to accommodate growth. We evaluate growth outcomes of 3DTEVGs compared with standard grafts for pulmonary artery reconstruction in porcine models. Methods:Magnetic resonance imaging (MRI) with 4-dimensional flow data was acquired in porcine models (n = 8). 3DTEVGs guided in design by computational flow dynamics were implanted (n = 4), with polytetrafluorethylene grafts used as controls (n = 4). Postoperative MRI and histologic features of explanted grafts were evaluated after 10 weeks. Results:All pigs survived, with evidence of patent grafts on postoperative MRI. Graft inner diameter changes were 0.47 ± 2.31 mm in 3DTEVGs and -4.61 ± 2.15 mm in controls (P = .018). Mean main pulmonary artery wall shear stress was significantly lower in 3DTEVGs (7.12 ± 4.21 Pa) than in controls (18.15 ± 8.37 Pa; P = .0396). Histologic evaluation of 3DTEVGs showed a single layer of endothelial cells, an organized smooth muscle layer, and collagen deposition with a remaining scaffold area of 21.37% ± 20.46%. Conclusions:Our patient-specific 3DTEVGs demonstrated optimal anatomic fit while maintaining ideal flow dynamics and promoting appropriate neovessel formation.

Purpose Patients presenting with coarctation of the aorta (CoA) may also suffer from co-existing transverse arch hypoplasia (TAH). Depending on the risks associated with the surgery and the severity of TAH, clinicians may decide to repair only CoA, and monitor the TAH to see if it improves as the patient grows. While acutely successful, eventually hemodynamics may become suboptimal if TAH is left untreated. The objective of this work aims to develop a patient-specific surgical planning framework for predicting and assessing postoperative outcomes of simple CoA repair and comprehensive repair of CoA and TAH. Methods The surgical planning framework consisted of virtual clamp placement, stenosis resection, and design and optimization of patient-specific aortic grafts that involved geometrical modeling of the graft and computational fluid dynamics (CFD) simulation for evaluating various surgical plans. Time-dependent CFD simulations were performed using Windkessel boundary conditions at the outlets that were obtained from patient-specific non-invasive pressure and flow data to predict hemodynamics before and after the virtual repairs. We applied the proposed framework to investigate optimal repairs for six patients ( n = 6) diagnosed with both CoA and TAH. Design optimization was performed by creating a combination of a tubular graft and a waterslide patch to reconstruct the aortic arch. The surfaces of the designed graft were parameterized to optimize the shape. Results Peak systolic pressure drop (PSPD) and time-averaged wall shear stress (TAWSS) were used as performance metrics to evaluate surgical outcomes of various graft designs and implantation. The average PSPD improvements were 28% and 44% after the isolated CoA repair and comprehensive repair, respectively. Maximum values of TAWSS were decreased by 60% after CoA repair and further improved by 22% after the comprehensive repair. The oscillatory shear index was calculated and the values were confirmed to be in the normal range after the repairs. Conclusion The results showed that the comprehensive repair outperforms the simple CoA repair and may be more advantageous in the long term in some patients. We demonstrated that the surgical planning and patient-specific flow simulations could potentially affect the selection and outcomes of aorta repairs.

OBJECTIVE:Composite tracheal grafts (CTG) combining decellularized scaffolds with external biomaterial support have been shown to support host-derived neotissue formation. In this study, we examine the biocompatibility, graft epithelialization, vascularization, and patency of three prototype CTG using a mouse microsurgical model. STUDY DESIGN:Tracheal replacement, regenerative medicine, biocompatible airway splints, animal model. METHOD:CTG electrospun splints made by combining partially decellularized tracheal grafts (PDTG) with polyglycolic acid (PGA), poly(lactide-co-ε-caprolactone) (PLCL), or PLCL/PGA were orthotopically implanted in mice (N = 10/group). Tracheas were explanted two weeks post-implantation. Micro-Computed Tomography was conducted to assess for graft patency, and histological analysis was used to assess for epithelialization and neovascularization. RESULT:Most animals (greater than 80%) survived until the planned endpoint and did not exhibit respiratory symptoms. MicroCT confirmed the preservation of graft patency. Grossly, the PDTG component of CTG remained intact. Examining the electrospun component of CTG, PGA degraded significantly, while PLCL+PDTG and PLCL/PGA + PDTG maintained their structure. Microvasculature was observed across the surface of CTG and infiltrating the pores. There were no signs of excessive cellular infiltration or encapsulation. Graft microvasculature and epithelium appear similar in all groups, suggesting that CTG did not hinder endothelialization and epithelialization. CONCLUSION:We found that all electrospun nanofiber CTGs are biocompatible and did not affect graft patency, endothelialization and epithelialization. Future directions will explore methods to accelerate graft regeneration of CTG. LEVEL OF EVIDENCE:N/A Laryngoscope, 134:1155-1162, 2024.

During the global spread of COVID-19, high demand and limited availability of melt-blown filtration material led to a manufacturing backlog of N95 Filtering Facepiece Respirators (FFRs). This shortfall prompted the search for alternative filter materials that could be quickly mass produced while meeting N95 FFR filtration and breathability performance standards. Here, an unsupported, nonwoven layer of uncharged polystyrene (PS) microfibers was produced via electrospinning that achieves N95 performance standards based on physical parameters (e.g., filter thickness) alone. PS microfibers 3-6 mu m in diameter and deposited in an ~5mm thick filter layer are favorable for use in FFRs, achieving high filtration efficiencies (>= 97.5%) and low pressure drops (<= 15mm H2O). The PS microfiber filter demonstrates durability upon disinfection with hydroxyl radicals (center dot OH), maintaining high filtration efficiencies and low pressure drops over six rounds of disinfection. Additionally, the PS microfibers exhibit antibacterial activity (1-log removal of E. coli) and can be modified readily through integration of silver nanoparticles (AgNPs) during electrospinning to enhance their activity (>= 3-log removal at 25wt% AgNP integration). Because of their tunable performance, potential reusability with disinfection, and antimicrobial properties, these electrospun PS microfibers may represent a suitable, alternative filter material for use in N95 FFRs.

Introduction: Complex vascular reconstruction such as that of the right ventricle to pulmonary artery (RVPA) and the aortic arch remains challenging due to the various 3D geometry of each patient. Tissue-engineered vascular grafts (TEVG) possess not only excellent antithrombotic and anti-infective properties but also the ability to grow as the patient matures. 3D printed patient-specific TEVG can maintain optimal hemodynamics with the growth of the patient and may improve surgical outcomes. We applied our unique 3D printing technology to create patient-specific TEVG for RVPA and the aortic arch. Methods: We acquired MRI and 4-dimensional flow data for the native anatomy of pigs (n=8) to design a patient-specific TEVG of the pulmonary artery (n=5) and the aortic arch (n=3) 4 weeks prior to surgery. The optimal shape of the branched vascular graft (n=8) was designed using a computer-aided design informed by computational flow dynamics analysis. We manufactured and implanted the grafts into the RVPA or aortic arch in the porcine model. The grafts were explanted after surgery at 8 - 12 weeks for evaluation. Pre- and post-op implant flow dynamics data in MRI and histology were analyzed. Results: The local neointimal thickness of TEVG in histology and the corresponding area of wall shear stress in 4D MRI were measured. Low wall shear stress, an aspect of MRI flow analysis, demonstrated a significant correlation with decreased neointimal thickness through histology (R2=0.65, P=0.016), which suggested optimal shape and design is important for appropriate neotissue formation. Conclusions: Our 3D printed custom designed TEVG demonstrated optimal anatomical fit maintaining ideal flow dynamics can attenuate neointimal hyperplasia and appropriate neovessel formation.

Objective:Many patients who require hemodialysis treatment will often require a prosthetic graft after multiple surgeries. However, the patency rate of grafts currently available commercially has not been satisfactory. Tissue engineering vascular grafts (TEVGs) are biodegradable scaffolds created to promote autologous cell proliferation and functional neotissue regeneration and, accordingly, have antithrombogenicity. Therefore, TEVGs can be an alternative prosthesis for small diameter grafts. However, owing to the limitations of the graft materials, most TEVGs are rigid and can easily kink when implanted in limited spaces, precluding future clinical application. Previously, we developed a novel corrugated nanofiber graft to prevent graft kinking. Reinforcement of these grafts to ensure their safety is required in a preclinical study. In the present study, three types of reinforcement were applied, and their effectiveness was examined using large animals.Methods:In the present study, three different reinforcements for the graft composed of corrugated poly-ε-caprolactone (PCL) blended with poly(L-lactide-co-ε-caprolactone) (PLCL) created with electrospinning were evaluated: 1) a polydioxanone suture, 2) a 2-0 polypropylene suture, 3) a polyethylene terephthalate/polyurethane (PET/PU) outer layer, and PCL/PLCL as the control. These different grafts were then implanted in a U-shape between the carotid artery and jugular vein in seven ovine models for a total of 14 grafts during a 3-month period. In evaluating the different reinforcements, the main factors considered were cell proliferation and a lack of graft dilation, which were evaluated using ultrasound examinations and histologic and mechanical analysis.Results:No kinking of the grafts occurred. Overall, re-endothelialization was observed in all the grafts at 3 months after surgery without graft rupture or calcification. The PCL/PLCL grafts and PCL/PLCL grafts with a polydioxanone suture showed high cell infiltration; however, they had become dilated 10 weeks after surgery. In contrast, the PCL/PLCL graft with the 2-0 suture and the PCL/PLCL graft covered with a PET/PU layer did not show any graft expansion. The PCL/PLCL graft covered with a PET/PU layer showed less cell infiltration than that of the PCL/PLCL graft.Conclusions:Reinforcement is required to create grafts that can withstand arterial pressure. Reinforcement with suture materials has the potential to maintain cell infiltration into the graft, which could improve the neotissue formation of the graft.

Background Many esophageal pathologies are clinically treated by resection and reconstruction of the esophagus. Surgical esophagectomy remains a morbid procedure and despite minimally invasive advances, has changed little in decades. Novel approaches to esophageal segmental resection and reconstruction are an unmet need. Methods Circumferential thoracic esophageal transection was performed in both male and female pigs and the defects reconstructed using 5 or 10 cm polyurethane (PU) tubular grafts and stented. A subset were treated with stent only. Animals were survived to 14, 30, 60, and 399 days. Tissues were evaluated histologically, and via non-invasive serial endoscopy and contrast swallowing studies in long-term animals. Results Luminal patency was achieved in all animals with no clinical evidence of leak. In short-term animals, there was healing noted in all cases with a variably sized region of ulceration remaining at the most central part of the repaired tube (between the proximal and distal anastomosis). In four long-term animals following stent removal, two resumed normal diet and thrived, while two animals were euthanized prior to the proposed endpoint because of stricture formation and inability to tolerate a normal diet. Re-epithelialization was observed in all groups, and more complete over time. Conclusions The PU scaffold provides a matrix across which formation of new tissue can occur. The mechanisms through which this happens remain unclear, but likely a combination of fibrosis and tissue contraction, in conjunction with new tissue formation.

Objective: Although surgical simulation using computational fluid dynamics has advanced, little is known about the accuracy of cardiac surgical procedures after patient-specific design. We evaluated the effects of discrepancies in location for patient-specific simulation and actual implantation on hemodynamic performance of patient-specific tissue-engineered vascular grafts (TEVGs) in porcine models. Methods: Magnetic resonance angiography and 4-dimensional (4D) flow data were acquired in porcine models (n = 11) to create individualized TEVGs. Graft shapes were optimized and manufactured by electrospinning bioresorbable material onto a metal mandrel. TEVGs were implanted 1 or 3 months postimaging, and postoperative magnetic resonance angiography and 4D flow data were obtained and segmented. Displacement between intended and observed TEVG position was determined through center of mass analysis. Hemodynamic data were obtained from 4D flow analysis. Displacement and hemodynamic data were compared using linear regression. Results: Patient-specific TEVGs were displaced between 1 and 8 mm during implantation compared with their surgically simulated, intended locations. Greater offset between intended and observed position correlated with greater wall shear stress (WSS) in postoperative vasculature (P < .01). Grafts that were implanted closer to their intended locations showed decreased WSS. Conclusions: Patient-specific TEVGs are designed for precise locations to help optimize hemodynamic performance. However, if TEVGs were implanted far from their intended location, worse WSS was observed. This underscores the importance of not only patient-specific design but also precision-guided implantation to optimize hemodynamics in cardiac surgery and increase reproducibility of surgical simulation.

Objectives/HypothesisTissue‐engineered tracheal grafts (TETGs) offer a potential solution for repair of long‐segment airway defects. However, preclinical and clinical TETGs have been associated with chronic inflammation and macrophage infiltration. Macrophages express great phenotypic heterogeneity (generally characterized as classically activated [M1] vs. alternatively activated [M2]) and can influence tracheal repair and regeneration. We quantified and characterized infiltrating host macrophages using mouse microsurgical tracheal replacement models.Study DesignTranslational research, animal model.MethodsWe assessed macrophage infiltration and phenotype in animals implanted with syngeneic tracheal grafts, synthetic TETGs, or partially decellularized tracheal scaffolds (DTSs).ResultsMacrophage infiltration was observed following tracheal replacement with syngeneic trachea. Both M1 and M2 macrophages were present in native trachea and increased during early tracheal repair (P = .014), with an M1/M2 ratio of 0.48 ± 0.15. In contrast, orthotopic implantation of synthetic TETGs resulted in a shift to M1 predominant macrophage phenotype with an increased M1/M2 ratio of 1.35 ± 0.41 by 6 weeks following implant (P = .035). Modulation of the synthetic scaffold with the addition of polyglycolic acid (PGA) resulted in a reduction of M1/M2 ratio due to an increase in M2 macrophages (P = .006). Using systemic macrophage depletion, the M1/M2 ratio reverted to native values in synthetic TETG recipients and was associated with an increase in graft epithelialization. Macrophage ratios seen in DTSs were similar to native values.ConclusionsM1 and M2 macrophages are present during tracheal repair. Poor epithelialization with synthetic TETG is associated with an elevation of the M1/M2 ratio. Macrophage phenotype can be altered with scaffold composition and host‐directed systemic therapies. DTSs exhibit M1/M2 ratios similar to those seen in native trachea and syngeneic tracheal replacement.Level of EvidenceNA Laryngoscope, 132:737–746, 2022

Tissue-engineered vascular grafts (TEVGs) require adequate extracellular matrix (ECM) to withstand arterial pressure. Tissue transglutaminase (TG2) and lysyl oxidase (LOX) are enzymes that cross-link ECM proteins and play a pivotal role in the development of vascular stiffness associated with aging. The purpose of this study is to investigate the expression of ECM cross-linking enzymes and mechanisms of scaffold degeneration leading to vascular stiffness in TEVG remodeling. Fast- and slow-degrading electrospun TEVGs were fabricated using polydioxanone (PDO) and poly(L-lactide-co-caprolactone) (PLCL) copolymer, with a PDO/PLCL ratio of 9:1 for fast-degrading and 1:1 for slow-degrading graft. These grafts were implanted in rats (n = 5/group) as abdominal aortic interposition conduits. The grafts were harvested at 1 month to evaluate patency, mechanical properties, vascular neotissue formation, and the expression of ECM cross-linking enzymes. All TEVGs were patent without any aneurysmal formation at 1 month. ECM area, TG2-positive area, and LOX-positive area were significantly greater in fast-degrading TEVGs compared to slow-degrading TEVGs, with significantly less remaining scaffold. The mechanical properties of fast-degrading TEVGs were similar to that of native aorta, as demonstrated by strain-stress curve. In conclusion, at 1 month, fast-degrading TEVGs had rapid and well-organized ECM with greater TG2 and LOX expression and native-like mechanical properties, compared to slow-degrading TEVGs. Impact statement Around 1.4 million patients in the United States require arterial prostheses each year due to cardiovascular diseases. Current synthetic vascular grafts suffer from increased risk of infection, thrombosis, a lack of endothelialization, and compliance mismatch to the native vasculature. Tissue-engineered vascular graft (TEVGs) presented in this study exhibited tunable biodegradation profiles by controlling the polymer ratio of polydioxanone/poly(L-lactide-co-caprolactone). One month after implantation, the fast-degrading TEVGs exhibited mechanical properties similar to that of native aorta, formation of endothelium, and well-organized extracellular matrix (ECM) with increased expression of tissue transglutaminase and lysyl oxidases, which are critical to the ECM remodeling process.

Synthetic scaffolds for the repair of long-segment tracheal defects are hindered by insufficient biocompatibility and poor graft epithelialization. In this study, we determined if extracellular matrix (ECM) coatings improved the biocompatibility and epithelialization of synthetic tracheal grafts (syn-TG). Porcine and human ECM substrates (pECM and hECM) were created through the decellularization and lyophilization of lung tissue. Four concentrations of pECM and hECM coatings on syn-TG were characterized for their effects on scaffold morphologies and on in vitro cell viability and growth. Uncoated and ECM-coated syn-TG were subsequently evaluated in vivo through the orthotopic implantation of segmental grafts or patches. These studies demonstrated that ECM coatings were not cytotoxic and, enhanced the in vitro cell viability and growth on syn-TG in a dose-dependent manner. Mass spectrometry demonstrated that fibrillin, collagen, laminin, and nephronectin were the predominant ECM components transferred onto scaffolds. The in vivo results exhibited similar robust epithelialization of uncoated and coated syn-TG patches; however, the epithelialization remained poor with either uncoated or coated scaffolds in the segmental replacement models. Overall, these findings demonstrated that ECM coatings improve the seeded cell biocompatibility of synthetic scaffolds in vitro; however, they do not improve graft epithelialization in vivo.

Background: The purpose of this study was to evaluate the mechanical, structural, and histologic quality of rotator cuff repairs augmented with an interposition electrospun nanofiber scaffold composed of polyglycolic acid (PGA) and poly-L-lactide-co-epsilon-caprolactone (PLCL) in an acute sheep model. Methods: Forty acute infraspinatus tendon detachment and repair procedures were performed in a sheep infraspinatus model using a double-row transosseous-equivalent anchor technique either with an interposition nanofiber scaffold composed of polyglycolic acid-poly-L-lactide-co-epsilon-caprolactone or with no scaffold. Animals were euthanized at the 6-week (20 samples) and 12-week (20 samples) postoperative time points to assess the biomechanical and histologic properties of the repairs and to compare differences within each group. Results: Within the scaffold-treated group, there was a significant increase in ultimate failure force (in newtons) from 6 to 12 weeks (P < .01), a significant increase in ultimate failure load from 6 to 12 weeks (P < .01), and a significant increase in ultimate failure stress (in megapascals) from 6 to 12 weeks (P < .01). At 6 weeks, the tendon-bone attachment was most consistent with an "indirect" type of insertion, whereas at 12 weeks, a visible difference in the progression and re-formation of the enthesis was observed. Compared with controls, animals in the scaffold-treated group displayed an insertion of the fibrous tendon with the humeral footprint that was beginning to be organized in a manner similar to the "native" direct/fibrocartilaginous insertion of the ovine infraspinatus tendon. In the majority of these animals treated with the scaffold, prominent perforating collagen fibers, similar to Sharpey fibers, were present and extending through a region of calcified fibrocartilage and attaching to the humeral footprint. No surgical complications occurred in any of the 40 sheep, including delayed wound healing or infection. Conclusions: In a sheep acute rotator cuff repair model, securing a nanofiber scaffold between the tendon and the bone using a double-row transosseous-equivalent anchor fixation technique resulted in greater failure strength. Additionally, at the enthesis, Sharpey fiber-like attachments (ie, collagen fibers extending from the tendon into the calcified fibrocartilage of the humerus) were observed, which were not seen in the control group. (C) 2021 The Authors.

Tissue-engineered vascular grafts (TEVGs) require adequate extracellular matrix (ECM) to withstand arterial pressure. Tissue transglutaminase (TG2) and lysyl oxidase (LOX) are enzymes that cross-link ECM proteins and play a pivotal role in the development of vascular stiffness associated with aging. The purpose of this study is to investigate the expression of ECM cross-linking enzymes and mechanisms of scaffold degeneration leading to vascular stiffness in TEVG remodeling. Fast- and slow-degrading electrospun TEVGs were fabricated using polydioxanone (PDO) and poly(L-lactide-co-caprolactone) (PLCL) copolymer, with a PDO/PLCL ratio of 9:1 for fast-degrading and 1:1 for slow-degrading graft. These grafts were implanted in rats (n=5/group) as abdominal aortic interposition conduits. The grafts were harvested at one month to evaluate patency, mechanical properties, vascular neotissue formation and the expression of ECM cross-linking enzymes. All TEVGs were patent without any aneurysmal formation at one month. ECM area, TG2 positive area and LOX positive area were significantly greater in fast-degrading TEVGs compared to slow-degrading TEVGs, with significantly less remaining scaffold. The mechanical properties of fast-degrading TEVGs were similar to that of native aorta, as demonstrated by strain-stress curve. In conclusion, at one month, fast-degrading TEVGs had rapid and well-organized ECM with greater TG2 and LOX expression and native-like mechanical properties, compared to slow-degrading TEVGs.