Small-caliber Blood Vessels Research Articles

Gelatin/heparin coated bio-inspired polyurethane composite fibers to construct small-caliber artificial blood vessel grafts

Long-term patency and ability for revascularization remain challenges for small-caliber blood vessel grafts to treat cardiovascular diseases clinically. Here, a gelatin/heparin coated bio-inspired polyurethane composite fibers-based artificial blood vessel with continuous release of NO and biopeptides to regulate vascular tissue repair and maintain long-term patency is fabricated. A biodegradable polyurethane elastomer that can catalyze S-nitrosothiols in the blood to release NO is synthesized (NPU). Then, the NPU core-shell structured nanofiber grafts with requisite mechanical properties and biopeptide release for inflammation manipulation are fabricated by electrospinning and lyophilization. Finally, the surface of tubular NPU nanofiber grafts is coated with heparin/gelatin and crosslinked with glutaraldehyde to obtain small-caliber artificial blood vessels (ABVs) with the ability of vascular revascularization. We demonstrate that artificial blood vessel grafts promote the growth of endothelial cells but inhibit the growth of smooth muscle cells by the continuous release of NO; vascular grafts can regulate inflammatory balance for vascular tissue remodel without excessive collagen deposition through the release of biological peptides. Vascular grafts prevent thrombus and vascular stenosis to obtain long-term patency. Hence, our work paves a new way to develop small-caliber artificial blood vessel grafts that can maintain long-term patency in vivo and remodel vascular tissue successfully.

Morphofunctional characteristics of the vessels of the small circle of blood circulation in those who died from severe and extremely severe forms of new coronavirus infection

BACKGROUND: An important feature of COVID-19 is the development of pronounced hypercoagulation with an increased risk of thrombotic damage to the pulmonary vascular bed, mainly the pulmonary arteries. Thrombosis of the pulmonary blood vessels causes a local violation of hemodynamics with the development of hyperemia, edema, which leads to a decrease in ventilation of the lung tissue area and serves as one of the causes of respiratory failure.
 AIM: This study aimed to conduct a morphological and morphometric analysis of the vascular bed of lung tissues in deceased with severe and extremely severe forms of new coronavirus infection who were on inpatient treatment in the period 2020-2022.
 METHODS: A pathomorphologic study of 129 autopsy cases with a confirmed diagnosis of a new coronavirus infection COVID-19 was performed. Morphometric analysis and statistical data processing of the pulmonary vascular system in histologic preparations stained with hematoxylin and eosin stain, orcein stain and Martius Scarlet Blue (MSB) stain was performed. The control group consisted of 14 patients who died of cardiovascular disease with bilateral focal confluent pneumonia.
 RESULTS: It was found that the proportion of thrombosed vessels in the lung tissues of the deceased was 27.6%. In 87.2% of cases, thrombosis develops in small arteries (lumen diameter 30-500 microns) and small veins (lumen diameter 40-500 microns). The vascular-functional indices of Kernogan and Vogenworth were statistically significantly increased in small arteries and small veins of the 4th order (p=0.001), small arteries (p=0.001) and small veins of the 5th order (p=0.014) compared with the control group.
 CONCLUSION: Diffuse involvement of small caliber blood vessels in the pathological process reflects the severity of specific hemocoagulopathic disorders in the lung tissue. Such disorders lead to the development of ventilation-perfusion disorders and entail an increase in right ventricular failure.

Primary central nervous system vasculitis: A diagnostic and therapeutic challenge. A series of 7 patients

IntroductionPrimary central nervous system vasculitis (PCNSV) is a rare disease affecting medium- and small-calibre blood vessels of the central nervous system. ObjectiveThe aim of this study was to analyse clinical findings and diagnostic aspects, with special attention to histopathological findings, as well as the treatments used and treatment response in patients diagnosed with PCNSV at our hospital. Patients and methodsWe conducted a retrospective descriptive analysis of patients with a diagnosis of PCNSV at discharge from our centre and meeting the 1988 Calabrese criteria. To this end, we analysed the hospital discharge records of Hospital General Universitario de Castellón between January 2000 and May 2020. ResultsWe analysed a series of 7 patients who were admitted with transient focal alterations and other less specific symptoms such as headache or dizziness; diagnosis was based on histological findings in 5 cases and on suggestive arteriographic findings in the remaining 2. Neuroimaging results were pathological in all cases, and CSF analysis detected alterations in 3 of the 5 patients who underwent lumbar puncture. All patients received initial treatment with megadoses of corticosteroids followed by immunosuppressive treatment. Progression was unfavourable in 6 cases, with fatal outcomes in 4. ConclusionsDespite the diagnostic challenge of PCNSV, it is essential to attempt to reach a definitive diagnosis using such tools as histopathology and/or arteriography studies, in order to promptly establish appropriate treatment and thus reduce the morbidity and mortality of this condition.

Ischemic Stroke in Neurosarcoidosis: A Retrospective Cohort Analysis

Objective To provide a detailed analysis of the clinical features and course of ischemic stroke secondary to sarcoidosis of the CNS and to observe the effects of immunosuppression in the prevention of recurrent cerebrovascular disease. Background Cerebrovascular disease is rarely reported in neurosarcoidosis and constitutes one of its least well-described forms, though recognition for it has grown in the last decade with recent studies estimating a higher frequency of occurrence than previously known. Design/Methods Patients with ischemic stroke were included if the mechanism was directly attributable to sarcoidosis of the CNS. Patients were excluded if an alternative stroke etiology was of equal or higher likelihood than CNS sarcoidosis. Results Neurologic disease was the initial presenting manifestation of sarcoidosis in 8/11 (72.7%), and ischemic stroke was an inaugural manifestation of sarcoidosis in 4/11 (36.4%). Small vessel disease was the predominant ischemia subtype (10/11, 90.9%) with pontine perforating vessels (6/11, 54.5%) and lenticulostriate arteries (3/11, 27.3%) being the vessels most often affected. Vessels with a more rostral supratentorial distribution were uncommonly affected. Common neuroinflammatory accompaniments included leptomeningitis (10/11, 90.9%) and cranial nerve disease (4/11, 36.4%). Recurrent strokes occurred in 8/11 (72.7%), and recurrent neuroinflammation occurred in 7/11 (63.6%). Antiplatelet drugs were used in 6/11 (54.5%). Most patients (10/11, 90.9%) required at least two lines of immunosuppression to achieve inflammatory disease remission in this context; infliximab was the most successfully employed immunosuppressant (7/8 treatment courses, 87.5%). The presenting median modified Rankin Scale score of 4.0 improved to 2.0 over a median period of follow-up of 52.0 months. Conclusions Ischemic strokes in neurosarcoidosis occur in a caudal-to-rostral distribution, tend to affect small caliber blood vessels that lack collateral blood flow, and typically associate with inflammatory leptomeningeal disease.

Ischemic stroke in neurosarcoidosis: A retrospective cohort analysis

BackgroundCerebrovascular disease is rarely reported in neurosarcoidosis and constitutes one of its least well-described forms, though recognition for it has grown in the last decade with recent studies estimating a higher frequency of occurrence than previously known. MethodsPatients with ischemic stroke were included if the mechanism was directly attributable to sarcoidosis of the CNS. Patients were excluded if an alternative stroke etiology was of equal or higher likelihood than CNS sarcoidosis. ResultsNeurologic disease was the initial presenting manifestation of sarcoidosis in 8/11 (72.7%), and ischemic stroke was an inaugural manifestation of sarcoidosis in 4/11 (36.4%). Small vessel disease was the predominant ischemia subtype (10/11, 90.9%) with pontine perforating vessels (6/11, 54.5%) and lenticulostriate arteries (3/11, 27.3%) being the vasculature most often affected. Vessels with a more rostral supratentorial distribution were uncommonly affected. Common neuroinflammatory accompaniments included leptomeningitis (10/11, 90.9%) and cranial nerve disease (3/11, 27.3%). Recurrent strokes occurred in 8/11 (72.7%), and recurrent neuroinflammation occurred in 7/11 (63.6%). Antiplatelet drugs were used in 6/11 (54.5%) patients. Most (10/11, 90.9%) required at least two lines of immunosuppression to achieve inflammatory disease remission in this context; infliximab was the most successfully employed immunosuppressant (7/8 treatment courses, 87.5%). Recurrent strokes occurred in 8/11 (72.7%) patients, and a second inflammatory attack occurred in 7/11 (63.6%) patients. The presenting median modified Rankin Scale score of 4.0 improved to 2.0 over a median period of follow-up of 52.0 months. ConclusionIschemic strokes in neurosarcoidosis occur in a caudal-to-rostral distribution, tend to affect small caliber blood vessels that lack collateral blood flow, and typically associate with inflammatory leptomeningeal disease. The risk for relapse in the forms of stroke or neuroinflammation are high in this neurosarcoidosis phenotype.

Effect of Hydrogel Contact Angle on Wall Thickness of Artificial Blood Vessel.

Vascular replacement is one of the most effective tools to solve cardiovascular diseases, but due to the limitations of autologous transplantation, size mismatch, etc., the blood vessels for replacement are often in short supply. The emergence of artificial blood vessels with 3D bioprinting has been expected to solve this problem. Blood vessel prosthesis plays an important role in the field of cardiovascular medical materials. However, a small-diameter blood vessel prosthesis (diameter < 6 mm) is still unable to achieve wide clinical application. In this paper, a response surface analysis was firstly utilized to obtain the relationship between the contact angle and the gelatin/sodium alginate mixed hydrogel solution at different temperatures and mass percentages. Then, the self-developed 3D bioprinter was used to obtain the optimal printing spacing under different conditions through row spacing, printing, and verifying the relationship between the contact angle and the printing thickness. Finally, the relationship between the blood vessel wall thickness and the contact angle was obtained by biofabrication with 3D bioprinting, which can also confirm the controllability of the vascular membrane thickness molding. It lays a foundation for the following study of the small caliber blood vessel printing molding experiment.

Construction of spider silk protein small-caliber tissue engineering vascular grafts based on dynamic culture and its performance evaluation.

Tissue engineering is an alternative method for preparing small-caliber (<6 mm) vascular grafts. Dynamic mechanical conditioning is being researched as a method to improve mechanical properties of tissue engineered blood vessels. This method attempts to induce unique reaction in implanted cells that regenerate the matrix around them, thereby improving the overall mechanical stability of the grafts. In this study, we used a bioreactor to seed endothelial cells and smooth muscle cells into the inner and outer layers of the electrospun spider silk protein scaffold respectively to construct vascular grafts. The cell proliferation, mechanical properties, blood compatibility and other indicators of the vascular grafts were characterized in vitro. Furthermore, the vascular grafts were implanted in Sprague Dawley rats, and the vascular grafts' patency, extracellular matrix formation, and inflammatory response were evaluated in vivo. We aimed to construct spider silk protein vascular grafts with the potential for in vivo implantation by using a pulsating flow bioreactor. The results showed that, when compared with the static culture condition, the dynamic culture condition improved cell proliferation on vascular scaffolds and enhanced mechanical function of vascular scaffolds. In vivo experiments also showed that the dynamic culture of vascular grafts was more beneficial for the extracellular matrix deposition and anti-thrombogenesis, as well as reducing the inflammatory response of vascular grafts. In conclusion, dynamic mechanical conditioning aid in the resolution of challenges impeding the application of electrospun scaffolds and have the potential to construct small-caliber blood vessels with regenerative function for cardiovascular tissue repair.

Transcriptomic Profile of Blood-Brain Barrier Remodeling in Cerebral Amyloid Angiopathy.

Cerebral amyloid angiopathy (CAA) is a small vessel disease characterized by amyloid β (Aβ) peptide deposition within the walls of medium to small-caliber blood vessels, cerebral microhemorrhage, and blood–brain barrier (BBB) leakage. It is commonly associated with late-stage Alzheimer’s disease. BBB dysfunction is indicated as a pathological substrate for CAA progression with hyperpermeability, enhancing the extravasation of plasma components and inducing neuroinflammation, further worsening BBB injury and contributing to cognitive decline. Although significant effort has been made in defining the gene mutations and risk factors involved in microvascular alterations with vascular dementia and Alzheimer’s disease, the intra- and intercellular pathogenic mechanisms responsible for vascular hyperpermeability are still largely unknown. The present study aimed to elucidate the transcriptional profile of the cerebral microvessels (BBB) in a murine model with CAA vasculopathy to define potential causes and underlying mechanisms of BBB injury. A comprehensive RNA sequencing analysis was performed of CAA vasculopathy in Tg-SwDI mice at 6 and 18 months in comparison to age-matched wildtype controls to examine how age and amyloid accumulation impact the transcriptional signature of the BBB. Results indicate that Aβ has a critical role in triggering brain endothelial cell and BBB dysfunction in CAA vasculopathy, causing an intense proinflammatory response, impairing oxidative metabolism, altering the coagulation status of brain endothelial cells, and remodeling barrier properties. The proinflammatory response includes both adaptive and innate immunity, with pronounced induction of genes that regulate macrophage/microglial activation and chemokines/adhesion molecules that support T and B cell transmigration. Age has an important impact on the effects of Aβ, increasing the BBB injury in CAA vasculopathy. However, early inflammation, particularly microglia/macrophage activation and the mediators of B lymphocytes’ activities are underlying processes of BBB hyperpermeability and cerebral microbleeds in the early stage of CAA vasculopathy. These findings reveal a specific profile of the CAA-associated BBB injury that leads to a full progression of CAA.

Silk Vascular Grafts with Optimized Mechanical Properties for the Repair and Regeneration of Small Caliber Blood Vessels.

As the incidence of cardiovascular diseases has been growing in recent years, the need for small-diameter vascular grafts is increasing. Considering the limited success of synthetic grafts, vascular tissue engineering/repair/regeneration aim to find novel solutions. Silk fibroin (SF) has been widely investigated for the development of vascular grafts, due to its good biocompatibility, tailorable biodegradability, excellent mechanical properties, and minimal inflammatory reactions. In this study, a new generation of three-layered SF vascular scaffolds has been produced and optimized. Four designs of the SILKGraft vascular prosthesis have been developed with the aim of improving kink resistance and mechanical strength, without compromising the compliance with native vessels and the proven biocompatibility. A more compact arrangement of the textile layer allowed for the increase in the mechanical properties along the longitudinal and circumferential directions and the improvement of the compliance value, which approached that reported for the saphenous and umbilical veins. The higher braid density slightly affected the grafts’ morphology, increasing surface roughness, but the novel design mimicked the corrugation approach used for synthetic grafts, causing significant improvements in kink resistance.

Optical Coherence Tomography Angiography and Attenuation Imaging for Label-Free Observation of Functional Changes in the Intestine after Sympathectomy: A Pilot Study

We present in this study optical coherence tomography angiography (OCTA) and OCT attenuation imaging (OCTAI) for in vivo non-destructive visualization of intramural blood and lymphatic vessels of the intestine wall. Rabbit small intestine in the norm and after thoracolumbar sympathectomy served as the object of the intraoperative study. Compared to OCTA real-time imaging, OCTAI takes several minutes and can be termed as “nearly real time”. OCTAI signal processing was modified to take into account the signal-to-noise ratio and the final thickness of the intestine wall. The results showed that, after sympathectomy, changes in functioning of intramural blood and lymphatic vessels were observed with a high statistical significance. The occurrence of trauma-induced constriction of the blood and lymphatic vessels led to an especially pronounced decrease in the length of small-caliber (&lt;30 µm) blood vessels (p &lt; 10−5), as well as in the volumetric density of lymphatic vessels (on average by ~50%) compared to their initial state. Remarkably, OCTA/OCTAI modalities provide the unique ability for “nearly-instant detection” of changes in functional status of the tissues, long before they become visible on histology. The proposed approach can be used in further experiments to clarify the mechanisms of changes in intestinal blood and lymph flows in response to trauma of the nervous system. Furthermore, potentially it can be used intraoperatively in patients requiring express diagnosis of the state of intramural blood and lymph circulation.

Vasculitis primarias del sistema nervioso central: reto diagnóstico y terapéutico. Serie de 7 pacientes

IntroductionPrimary central nervous system vasculitis (PCNSV) is a rare disease affecting medium- and small-calibre blood vessels of the central nervous system. ObjectiveThe aim of this study was to analyse clinical findings and diagnostic aspects, with special attention to histopathological findings, as well as the treatments used and treatment response in patients diagnosed with PCNSV at our hospital. Patients and methodsWe conducted a retrospective descriptive analysis of patients with a diagnosis of PCNSV at discharge from our centre and meeting the 1988 Calabrese criteria. To this end, we analysed the hospital discharge records of Hospital General Universitario de Castellón between January 2000 and May 2020. ResultsWe analysed a series of 7 patients who were admitted with transient focal alterations and other less specific symptoms such as headache or dizziness; diagnosis was based on histological findings in 5 cases and on suggestive arteriographic findings in the remaining 2.Neuroimaging results were pathological in all cases, and CSF analysis detected alterations in 3 of the 5 patients who underwent lumbar puncture.All patients received initial treatment with megadoses of corticosteroids followed by immunosuppressive treatment.Progression was unfavorable in 6 cases, with fatal outcomes in 4. ConclusionsDespite the diagnostic challenge of PCNSV, it is essential to attempt to reach a definitive diagnosis using such tools as histopathology and/or arteriography studies, in order to promptly establish appropriate treatment and thus reduce the morbidity and mortality of this condition.

Cardiovascular ACE2 receptor expression in patients undergoing heart transplantation.

AimsMembrane‐bound angiotensin‐converting enzyme (ACE)2 is the main cellular access point for SARS‐CoV‐2, but its expression and the effect of ACE inhibition have not been assessed quantitatively in patients with heart failure. The aim of this study was to characterize membrane‐bound ACE2 expression in the myocardium and myocardial vasculature in patients undergoing heart transplantation and to assess the effect of pharmacological ACE inhibition.Methods and resultsLeft ventricular (LV) tissue was obtained from 36 explanted human hearts from patients undergoing heart transplantation. Immunohistochemical staining with antibodies directed against ACE2 co‐registered with cardiac troponin T (cTnT) and α‐smooth muscle cell actin (SMA) was performed across the entire cohort. ACE2 receptor expression was quantitatively assessed throughout the myocardium and vasculature. ACE2 was consistently expressed throughout the LV myocardium (28.3% ± 22.2% of cardiomyocytes). ACE2 expression was also detected in small calibre blood vessels (range, 2–9 μm), albeit at quantitatively much lower levels (5% ± 9% of blood vessels). There was no significant difference in ACE2 expression between patients receiving ACE inhibitors prior to transplantation and ACE inhibitor‐negative controls (P > 0.05). ACE2 expression did not differ significantly between the different diagnostic groups as the underlying reason for heart transplantation (ANOVA > 0.05). N‐terminal pro‐brain natriuretic peptide (NT‐proBNP) (R 2 = 0.37, P = 0.0006) and pulmonary capillary wedge pressure (PCWP) (R 2 = 0.13, P = 0.043) assessed by right heart catheterization were significantly correlated with greater ACE2 expression in cardiomyocytes.ConclusionsThese data provide a comprehensive characterization of membrane‐bound cardiac ACE2 expression in patients with heart failure with no demonstrable effect exerted by ACE inhibitors.

Improved Performance of Bacterial Nanocellulose Conduits by the Introduction of Silk Fibroin Nanoparticles and Heparin for Small-Caliber Vascular Graft Applications.

Bacterial nanocellulose (BNC) is a promising material for small-caliber artificial blood vessels, although promoting its anticoagulant properties with more rapid endothelialization would improve long-term patency. Silk fibroin nanoparticles (SFNP) were introduced into the luminal wall surface of BNC conduits both with and without heparin (Hep) through pressurization followed by fixation. Hep was introduced in two ways: (1) embedded within SF nanoparticles to form SF-HepNPs for construction of the BNC-SF-HepNP conduit and (2) chemically grafted onto BNC and BNC-SFNP to form BNC-Hep and BNC-SFNP-Hep conduits. Fourier transform infrared spectroscopy confirmed the formation of SF-HepNPs, although they did not incorporate into the fibrillar network due to their large size. Hep was successfully grafted onto BNC and BNC-SFNP, verified by toluidine blue staining. The hemocompatibility and cytocompatibility of the five samples (BNC, BNC-SFNP, BNC-SF-HepNP, BNC-Hep, and BNC-SFNP-Hep conduits) were compared in vitro. The heparinized BNC-Hep and BNC-SFNP-Hep conduits improved the anticoagulant properties, and BNC-SFNP-Hep promoted human umbilical vein endothelial cell proliferation but also controlled excessive human arterial smooth muscle cell proliferation, assisting rapid endothelialization and improving lumen patency. No significant inflammatory reaction or material degradation was observed after subcutaneous implantation for 4 weeks. Autogenous tissues were observed around the conduits, and cells infiltrated into the edges of all samples, the BNC-SFNP conduit causing the deepest infiltration, providing an appropriate microenvironment for angiogenesis when used in small-caliber blood vessel applications. Few inflammatory cells were found around the BNC-Hep and BNC-SFNP-Hep conduits. Thus, the anticoagulant properties of the BNC-SFNP-Hep conduit and its stimulation of endothelialization suggest that it has great potential in clinical applications as a small-caliber artificial blood vessel.

Elastomeric Electrospun Scaffolds of a Biodegradable Aliphatic Copolyester Containing PEG-Like Sequences for Dynamic Culture of Human Endothelial Cells.

In the field of artificial prostheses for damaged vessel replacement, polymeric scaffolds showing the right combination of mechanical performance, biocompatibility, and biodegradability are still demanded. In the present work, poly(butylene-co-triethylene trans-1,4-cyclohexanedicarboxylate), a biodegradable random aliphatic copolyester, has been synthesized and electrospun in form of aligned and random fibers properly designed for vascular applications. The obtained materials were analyzed through tensile and dynamic-mechanical tests, the latter performed under conditions simulating the mechanical contraction of vascular tissue. Furthermore, the in vitro biological characterization, in terms of hemocompatibility and cytocompatibility in static and dynamic conditions, was also carried out. The mechanical properties of the investigated scaffolds fit within the range of physiological properties for medium- and small-caliber blood vessels, and the aligned scaffolds displayed a strain-stiffening behavior typical of the blood vessels. Furthermore, all the produced scaffolds showed constant storage and loss moduli in the investigated timeframe (24 h), demonstrating the stability of the scaffolds under the applied conditions of mechanical deformation. The biological characterization highlighted that the mats showed high hemocompatibility and low probability of thrombus formation; finally, the cytocompatibility tests demonstrated that cyclic stretch of electrospun fibers increased endothelial cell activity and proliferation, in particular on aligned scaffolds.

ANGIOLYMPHOID HYPERPLASIA WITH EOSINOPHILIA: A CASE REPORT OF A RARE BENIGN VASCULAR TUMOR

Oral vascular lesions present a variety of clinicopathologic aspects and often lead to diagnostic difficulties. We describe the case of a 27-year-old male patient referred to our service for evaluation of an asymptomatic lesion in the oral cavity. Intraoral examination revealed a sessile, red nodule of soft consistency in lateral border of tongue, measuring approximately 0.5 cm in diameter. Based on clinical diagnosis of inflammatory fibrous hyperplasia, an excisional biopsy was performed. Histopathologic analysis revealed a benign vascular lesion characterized by proliferation of epithelioid endothelial cells, mostly constituting small-caliber tortuous blood vessels. Mononuclear inflammatory infiltrate with remarkable presence of eosinophils was also evident. Proliferating cells demonstrated diffuse immunopositivity for CD31, CD34, and S100. These findings led to the histopathologic diagnosis of angiolymphoid hyperplasia with eosinophilia. This report emphasizes the importance of knowledge regarding clinicopathologic features of oral vascular lesions for a correct diagnosis and management of the patient.

Construction and performance evaluation of Hep/silk-PLCL composite nanofiber small-caliber artificial blood vessel graft

To meet the growing clinical demand for small-caliber blood vessel grafts to treat cardiovascular diseases, it is necessary to develop safe and long-term unobstructed grafts. In this study, a biodegradable graft made of composite nanofibers is introduced. A composite nanofiber core-shell structure was prepared by a combination of conjugate electrospinning and freeze-dry technology. The core fiber was poly(l-lactide-co-caprolactone) (PLCL)-based and the core fibers were coated with heparin/silk gel, which acted as a shell layer. This special structure in which the core layer was made of synthetic materials and the shell layer was made of natural materials took advantage of these two different materials. The core PLCL nanofibers provided mechanical support during vascular reconstruction, and the shell heparin/silk gel layer enhanced the biocompatibility of the grafts. Moreover, the release of heparin in the early stage after transplantation could regulate the microenvironment and inhibit the proliferation of intima. All of the graft materials were biodegradable and safe biomaterials, and the degradation of the graft provided space for the growth of regenerated tissue in the late stage of transplantation. Animal experiments showed that the graft remained unobstructed for more than eight months in vivo. In addition, the regenerated vascular tissue provided a similar function to that of autogenous vascular tissue when the graft was highly degraded. Thus, the proposed method produced a graft that could maintain long-term patency in vivo and remodel vascular tissue successfully.

Cellular attachment behavior on biodegradable polymer surface immobilizing endothelial cell-specific peptide

Small-caliber artificial blood vessels with inner diameters of smaller than 4 mm have not been put into practical use because of early thrombus formation and graft occlusion. To realize small-caliber artificial blood vessels with anti-thrombus property and long-term patency, one of the promising approaches is endothelialization of the lumen by tissue engineering approaches. Integrin α4β1 on the endothelial cell membrane is known to act as a receptor for Arg-Glu-Asp-Val (REDV) tetra-peptide, and this peptide can be used as a specific ligand to introduce endothelial cell attachment onto the surfaces of polymer scaffold. In this study, biodegradable polymer surface immobilizing REDV peptide were prepared, and the specific attachment of endothelial cells on it was investigated as a preliminary study for tissue-engineered small-caliber blood vessels in a future application. We synthesized copolymer of ε-caprolactone and depsipeptide having reactive carboxylic acid side-chain groups (PGDCL), and REDV peptide was attached to the copolymer to give PGDCL-REDV. The attachment of human umbilical vein endothelial cells (HUVECs) were investigated for the blend polymer film prepared by mixing PGDCL and PGDCL-REDV. The obtained blend polymer films exhibited sequence- and cell-specific HUVECs attachment through REDV peptide recognition. This technique should be useful not only to obtain artificial blood vessels which induce endothelialization and but also to provide biodegradable scaffolds with specific ligands immobilized surfaces for tissue regeneration.

Local Delivery of Dual MicroRNAs in Trilayered Electrospun Grafts for Vascular Regeneration.

Globally growing problems related to cardiovascular diseases lead to a considerable need for synthetic vascular grafts. For small-caliber vascular prosthesis, it remains essential to fulfill rapid endothelialization, inhibit intimal hyperplasia, and prevent calcification for keeping patency. To modulate vascular regeneration, herein, we developed a bioactive trilayered tissue-engineered vascular graft encapsulating both microRNA-126 and microRNA-145 in the fibrous inner and middle layers, respectively. In vitro cell activities demonstrated that the trilayered electrospun membranes had significant biological advantages in enhanced growth and intracellular nitric oxide production of vascular endothelial cells, modulation of phenotypes of vascular smooth muscle cells (SMCs), and restraint of calcium deposition through fast-releasing microRNA-126 and slow-releasing microRNA-145. Histological and immunofluorescent analyses of in vivo implantation in a rat abdominal aorta interposition model suggested that the dual-microRNA-loading trilayered electrospun graft exerted a positive effect on accelerating endothelialization, improving contractile SMC regeneration, and promoting normal extracellular matrix formation. Meanwhile, the local bioactivity of microRNA-126 and microRNA-145 in the trilayered vascular graft could regulate inflammation and depress calcification possibly by facilitating transformation of macrophages into the anti-inflammatory M2 phenotype. These findings indicated that the trilayered electrospun graft by local delivery of dual microRNAs could be possibly used as a bioactive substitute for replacement of artificial small-caliber blood vessels.

Clinical features and outcomes of patients with microscopic polyangiitis: experience of two centers

Background and Aim: Microscopic polyangiitis (MPA) is a rare necrotizing vasculitis that involves predominantly the small-caliber blood vessels. In this retrospective study, we aimed to evaluate the clinical findings, prognostic factors, and outcomes of MPA patients followed in two different centers. Material and Method: In this retrospective study, a total of 38 patients diagnosed and followed with MPA in two different centers between January 2005 and December 2019 were included. Medical records of the patients were reviewed retrospectively. The diagnoses were based on the definition of MPA in the Chapel Hill consensus conference (CHCC-2012). In addition to the socio-demographic characteristics, clinical features, laboratory and immunological parameters; time passed for the diagnosis, treatment, outcomes, and follow-up time were recorded for each patient. The Five Factor Scores (FFS; Revised FFS 2009) and Birmingham Vasculitis Activity Score (BVAS; Version 3) were applied in all patients. Results: In a total of 38 patients (10 females, 28 male) were included in the study. The mean age of the participants was 54.52 ± 8.21 (range: 32-74) years. The mean time passed for the diagnosis was 2.93 ± 2.03 (0.50-11) months and the mean follow-up period was 55.0 ± 30.51 (2-124) months. At admission, the mean BVAS was 18.28 ± 5.73 (8-35). The FFS results were as follows; 0 in 4 (10.5%) patients, 1 in 27 (71.1%) patients, 2 in 7 (18.4%) patients. The most common symptoms at admission were dyspnea, cough, and hemoptysis. Renal failure was present in 31 (81.5%) of the patients, at admission. The most common immunologic finding was the p-ANCA positivity in 26 (68.4%) patients. Among all patients, 25 (65.8 %) did not have any other attacks after the diagnosis. In follow-ups, 12 (31.5%) patients were passed away and vasculitis associated mortality rate was 18.4%. The effects of some factors on mortality including age ≥ 65 years, male gender, renal involvement, p-ANCA positivity, decreased oxygen saturation (&lt; 90%), having anemia at admission, having FEV1/FVC &lt; 70 in spirometry, having a FFS score of 2, and having a BVAS &gt; 18 were examined (Table 6). Only having an FFS score of 2 and BVAS &gt; 18 were determined as the factors significantly affecting mortality (P: 0.01). Conclusion: Pulmonary symptoms are more predominant in MPA. Though many patients did not have any other attacks after the diagnosis, the vasculitis associated mortality may reach about 20%. BVAS and FFS are still the best determinants of mortality.

Three-Layered Silk Fibroin Tubular Scaffold for the Repair and Regeneration of Small Caliber Blood Vessels: From Design to in vivo Pilot Tests.

Silk fibroin (SF) is an eligible biomaterial for the development of small caliber vascular grafts for substitution, repair, and regeneration of blood vessels. This study presents the properties of a newly designed multi-layered SF tubular scaffold for vascular grafting (SilkGraf). The wall architecture consists of two electrospun layers (inner and outer) and an intermediate textile layer. The latter was designed to confer high mechanical performance and resistance on the device, while electrospun layers allow enhancing its biomimicry properties and host's tissues integration. In vitro cell interaction studies performed with adult Human Coronary Artery Endothelial Cells (HCAECs), Human Aortic Smooth Muscle Cells (HASMCs), and Human Aortic Adventitial Fibroblasts (HAAFs) demonstrated that the electrospun layers favor cell adhesion, survival, and growth. Once cultured in vitro on the SF scaffold the three cell types showed an active metabolism (consumption of glucose and glutamine, release of lactate), and proliferation for up to 20 days. HAAF cells grown on SF showed a significantly lower synthesis of type I procollagen than on polystyrene, meaning a lower fibrotic effect of the SF substrate. The cytokine and chemokine expression patterns were investigated to evaluate the cells' proliferative and pro-inflammatory attitude. Interestingly, no significant amounts of truly pro-inflammatory cytokines were secreted by any of the three cell types which exhibited a clearly proliferative profile. Good hemocompatibility was observed by complement activation, hemolysis, and hematology assays. Finally, the results of an in vivo preliminary pilot trial on minipig and sheep to assess the functional behavior of implanted SF-based vascular graft identified the sheep as the more apt animal model for next medium-to-long term preclinical trials.