Spatial patterning of PCL µ-scaffolds directs 3D vascularized bio-construct morphogenesis in vitro

Modular tissue engineering (mTE) strategies aim to build three-dimensional tissue analogues in vitro by the sapient combination of cells, micro-scaffolds (μ-scaffs) and bioreactors. The translation of these newly engineered tissues into current clinical approaches is, among other things, dependent on implant-to-host microvasculature integration, a critical issue for cells and tissue survival in vivo. In this work we reported, for the first time, a computer-aided modular approach suitable to build fully vascularized hybrid (biological/synthetic) constructs (bio-constructs) with micro-metric size scale control of blood vessels growth and orientation. The approach consists of four main steps, starting with the fabrication of polycaprolactone μ-scaffs by fluidic emulsion technique, which exhibit biomimetic porosity features. In the second step, layers of μ-scaffs following two different patterns, namely ordered and disordered, were obtained by a soft lithography-based process. Then, the as obtained μ-scaff patterns were used as template for human dermal fibroblasts and human umbilical vein endothelial cells co-culture, aiming to promote and guide the biosynthesis of collagenous extracellular matrix and the growth of new blood vessels within the mono-layered bio-constructs. Finally, bi-layered bio-constructs were built by the alignment, stacking and fusion of two vascularized mono-layered samples featuring ordered patterns. Our results demonstrated that, if compared to the disordered pattern, the ordered one provided better control over bio-constructs shape and vasculature architecture, while minor effect was observed with respect to cell colonization and new tissue growth. Furthermore, by assembling two mono-layered bio-constructs it was possible to build 1-mm thick fully vascularized viable bio-constructs and to study tissue morphogenesis during 1 week of in vitro culture. In conclusion, our results highlighted the synergic role of μ-scaff architectural features and spatial patterning on cells colonization and biosynthesis, and pay the way for the possibility to create in silico designed vasculatures within modularly engineered bio-constructs.

Tri-culture of spatially organizing human skeletal muscle cells, endothelial cells, and fibroblasts enhances contractile force and vascular perfusion of skeletal muscle tissues

Constructing engineered human skeletal muscle tissues that resemble the function and microstructure of human skeletal muscles is key to utilizing them in a variety of applications such as drug development, disease modeling, regenerative medicine, and engineering biological machines. However, current in vitro skeletal muscle tissues are far inferior to native muscles in terms of contractile function and lack essential cues for muscle functions, particularly heterotypic cell-cell interactions between myoblasts, endothelial cells, and fibroblasts. Here, we develop an engineered muscle tissue with a coaxial three-layered tubular structure composed of an inner endothelial cell layer, an endomysium-like layer with fibroblasts in the middle, and an outer skeletal muscle cell layer, similar to the architecture of native skeletal muscles. Engineered skeletal muscle tissues with three spatially organized cell types produced thicker myotubes and lowered Young's modulus through extracellular matrix remodeling, resulting in 43% stronger contractile force. Furthermore, we demonstrated that fibroblasts localized in the endomysium layer induced angiogenic sprouting of endothelial cells into the muscle layer more effectively than fibroblasts homogeneously distributed in the muscle layer. This layered tri-culture system enables a structured spatial configuration of the three main cell types of skeletal muscle and promotes desired paracrine signaling, resulting in improved angiogenesis and increased contractile force. This research offers new insights to efficiently obtain new human skeletal muscle models, transplantable tissues, and actuators for biological machines.

The Vascularization Course of Labral Autograft and Its Effect on Tissue Healing: Acetabular Labral Augmentation Versus Labral Reconstruction in a Porcine Model

BACKGROUND

The preservation of the native labral vascularization is assumed to be the potential advantage of acetabular labral augmentation, the effect of which remains unknown.

PURPOSE

To identify the vascular distribution within the labral autograft and its effect on the healing process between labral augmentation (AUG) and reconstruction (RECON) in a porcine model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 36 pigs randomly underwent unilateral labral augmentation or reconstruction (AUG group, n = 18; RECON group, n = 18). The pigs were randomly sacrificed at 6, 12, and 24 weeks postoperatively. The labral autografts were harvested for macroscopic evaluation and histologic assessment. The labral autograft was zoned into 2 halves to observe the vascular distribution: the capsular half (zone I) and the articular half (zone II). Each zone was divided into 2 parts: the peripheral part (IA and IIA) and the part attached to the acetabulum (IB and IIB).

RESULTS

At 6 weeks, there existed more vascular ingrowth in zone I, whereas zone IIB appeared nearly avascular in both groups. At 12 weeks, the area with the greatest vascularity was zone II in the RECON group and zone IA in the AUG group. The vascularity was concentrated at zones IA and IIA in both groups at 24 weeks. The labral autografts were hypertrophic with sufficient filling of the labral defect in both groups at 6 weeks. At 12 weeks, an insufficient volume of the articular half was observed in 3 of 6 labral autografts in the RECON group, while all autografts remained well integrated with the chondrolabral junction in the AUG group. At 24 weeks, unsatisfactory merging of the labral autograft with the cartilage at the articular side was found in 2 of 6 labral autografts in the RECON group, which was not observed in the AUG group despite the sufficient volume of autografts labrum in both groups.

CONCLUSION

Slow vascular ingrowth within the articular half might account for the poor healing of the reconstructed labral autograft. Labral augmentation provides the possibility of better tissue healing because of the preservation of the original chondrolabral junction compared with labral reconstruction.

CLINICAL RELEVANCE

Labral augmentation might be a feasible alternative to labral reconstruction under the condition of viable labral remnants.

Dynamically Responsive Scaffolds from Microfluidic 3D Printing for Skin Flap Regeneration

Biological scaffolds hold promising perspectives for random skin flap regeneration, while the practical application is greatly limited by their insufficient vascularization ability and the lack of responsiveness during the dynamical healing process. Herein, a novel MXene-incorporated hollow fibrous (MX-HF) scaffold with dynamically responsive channels is presented for promoting vascularization and skin flap regeneration by using a microfluidic-assisted 3D printing strategy. Benefiting from the photothermal conversion capacity of the MXene nanosheets and temperature-responsive ability of poly(NIPAM) hydrogels in the MX-HF scaffolds, they display a near-infrared (NIR)-responsive shrinkage/swelling behavior, which facilitates the cell penetration into the scaffold channels from the surrounding environment. Moreover, by incorporating vascular endothelial growth factor (VEGF) into the hydrogel matrix for controllable delivery, the MX-HF scaffolds can achieve promoted proliferation, migration, and proangiogenic effects of endothelial cells under NIR irradiation. It is further demonstrated in vivo that the NIR-responsive VEGF@MX-HF scaffolds can effectively improve skin flap survival by promoting angiogenesis, decreasing inflammation, and attenuating apoptosis in skin flaps. Thus, it is believed that such responsive MX-HF scaffolds are promising candidates for clinical random skin flap regeneration as well as other diverse tissue engineering applications.

SDF-1 Functionalized Hydrogel Microcarriers for Skin Flap Repair

Critically sized skin flaps used to treat skin defects often suffer from necrosis due to insufficient blood supply. Hence there is an urgent need to improve the survival rate of skin flaps by promoting local angiogenesis. The delivery of growth factor loaded microcarriers have shown promise in enhancing defect repair, however, their rapid clearance from the defect site limits their regenerative potential. Thus, it is critical to develop microcarriers which can promote the sustained release of bioactive factors to effectively stimulate tissue repair. This study aimed to develop a stromal cell-derived factor 1 (SDF-1) loaded microcarrier coated with Matrigel (MC@SDF-1@Mat) to promote skin flap repair. SEM imaging showed that the surface of the microcarrier was coated by a porous Matrigel film. The drug release experiment showed that the Matrigel-coated microcarriers enhanced the sustained release of the model drug methylene blue when compared to uncoated group. MC@SDF-1@Mat significantly promoted the proliferation, migration, and angiogenesis of HUVECs via CCK-8, wound healing assay, and tube formation assay, respectively. Moreover, the murine random skin flap model was further established and treated. It was found that the flap necrosis area in the MC@SDF-1@Mat treated group was significantly reduced. H&E and Masson staining showed the histological structure and collagen organization exhibited a normal phenotype in the MC@SDF-1@Mat treated group. Additionally, CD31 immunohistochemical analysis showed that the MC@SDF-1@Mat treated group exhibited the greatest degree of neovascularization. In conclusion, our SDF-1 functionalized gelatin-based hydrogel microcarrier has potential clinical applications in promoting skin flap repair and drug delivery.

Dynamic Alterations of Metabolites Revealed the Vascularization Progression of Bioengineered Liver

Vascularization is a critical but challenging process in developing functional bioengineered liver with the decellularized liver scaffolds (DLSs), and the process is accompanied by cell-specific metabolic alterations. To elucidate the dynamic alterations of metabolites during vascularization, rat DLSs were vascularized with human umbilical vein endothelial cells, and a liquid chromatography mass spectrometry-based metabolomics was performed on culture supernatants collected at 0, 1, 3, 7, 14 and 21 days. Overall, 1698 peak pairs or metabolites were detected in the culture supernatants, with 309 metabolites being positively identified. The orthogonal partial least-squares discriminant analysis and functional enrichment analysis revealed three phases that could be clearly discriminated, including phase D1 (cell proliferation and migration), phase D3D7 (vascular lumen formation), and phase D14D21 (functional endothelial barrier formation). Seventy-two common differentially abundant metabolites of known identity were detected in these three phases when compared to day 0. Of these metabolites, a high level of beta-Alanine indicated a better degree of vascularization, and 14 days of in-vitro dynamic culture is required to develop a functionalized vascular structure. These results enriched our understanding of the metabolic mechanism of DLS vascularization, and indicated that beta-Alanine could function as a potential predictor of the patency of vascularized bioengineered livers. This article is protected by copyright. All rights reserved.

Temporal Control over Macrophage Phenotype and the Host Response via Magnetically Actuated Scaffolds

Cyclic strain generated at the cell-material interface is critical for the engraftment of biomaterials. Mechanosensitive immune cells, macrophages regulate the host-material interaction immediately after implantation by priming the environment and remodeling ongoing regenerative processes. This study investigated the ability of mechanically active scaffolds to modulate macrophage function in vitro and in vivo. Remotely actuated magnetic scaffolds enhance the phenotype of murine classically activated (M1) macrophages, as shown by the increased expression of the M1 cell-surface marker CD86 and increased secretion of multiple M1 cytokines. When scaffolds were implanted subcutaneously into mice and treated with magnetic stimulation for 3 days beginning at either day 0 or day 5 post-implantation, the cellular infiltrate was enriched for host macrophages. Macrophage expression of the M1 marker CD86 was increased, with downstream effects on vascularization and the foreign body response. Such effects were not observed when the magnetic treatment was applied at later time points after implantation (days 12-15). These results advance our understanding of how remotely controlled mechanical cues, namely, cyclic strain, impact macrophage function and demonstrate the feasibility of using mechanically active nanomaterials to modulate the host response in vivo.

VEGF Overexpression Significantly Increases Nanoparticle-Mediated siRNA Delivery and Target-Gene Downregulation

The availability of nanoparticles (NPs) to deliver small interfering RNA (siRNA) has significantly expanded the specificity and range of ‘druggable’ targets for precision medicine in cancer. This is especially important for cancers such as triple negative breast cancer (TNBC) for which there are no targeted treatments. Our purpose here was to understand the role of tumor vasculature and vascular endothelial growth factor (VEGF) overexpression in a TNBC xenograft in improving the delivery and function of siRNA NPs using in vivo as well as ex vivo imaging. We used triple negative MDA-MB-231 human breast cancer xenografts derived from cells engineered to overexpress VEGF to understand the role of VEGF and vascularization in NP delivery and function. We used polyethylene glycol (PEG) conjugated polyethylenimine (PEI) NPs to deliver siRNA that downregulates choline kinase alpha (Chkα), an enzyme that is associated with malignant transformation and tumor progression. Because Chkα converts choline to phosphocholine, effective delivery of Chkα siRNA NPs resulted in functional changes of a significant decrease in phosphocholine and total choline that was detected with ¹H magnetic resonance spectroscopy (MRS). We observed a significant increase in NP delivery and a significant decrease in Chkα and phosphocholine in VEGF overexpressing xenografts. Our results demonstrated the importance of tumor vascularization in achieving effective siRNA delivery and downregulation of the target gene Chkα and its function.

Sex-Differences and Associations Between Complement Activation and Synovial Vascularization in Patients with Late-Stage Knee Osteoarthritis

Purpose

Synovial inflammation in knee osteoarthritis (OA) causes disorganized synovial angiogenesis and complement activation in synovial fluid, but links between complement and synovial microvascular pathology have not been established. Since complement causes vascular pathology in other diseases and since sex-differences exist in complement activation and in OA, we investigated sex differences in synovial fluid complement factors, synovial tissue vascular pathology, and associations between complement and synovial vascular pathology in patients with late-stage knee OA.

Methods

Patients with symptomatic, late-stage radiographic knee OA undergoing total knee arthroplasty or high tibial osteotomy provided matched synovial fluid and tissue biopsies during surgery. Complement factors (C2, C5, adipsin, MBL, and CFI) and terminal complement complex (sC5b-C9) were measured in synovial fluid by multiplex or enzyme-linked immunosorbent assay, respectively. Features of synovial vascular pathology (vascularization, perivascular edema, and vasculopathy) were assessed by histopathology. Multivariate linear regression models were used to assess associations between synovial fluid complement factors and histopathological features of vascular pathology, with adjustment for age, sex, body mass index, and sex interaction. Sex-disaggregated comparisons were completed.

Results

Synovial fluid biomarker and histopathology data were included from 97 patients. Most synovial fluid complement factors and synovial tissue histopathological features were similar between sexes. Synovial fluid C5 trended to lower levels in males (-20.93 ng/mL [95%CI -42.08, 0.23] p=0.05). Median vasculopathy scores (0.42 [95%CI 0.07, 0.77] p=0.02) were higher in males. In the full cohort, C5 concentration was associated with lower vascularization scores (-0.005 [95%CI -0.010, -0.0001] p=0.04) while accounting for sex*C5 interaction. In sex-disaggregated analyses, increased C5 concentration was associated with lower vascularization scores (-0.005 [95%CI –0.009, -0.0001] p=0.04) in male patients, but not in female patients. Males had higher sC5b-C9 compared to females. Additionally, males with high C5 had a higher synovial fluid concentration of sC5b-C9 compared to males with low C5. No differences were found in females.

Conclusion

Higher synovial fluid C5 levels were associated with increased complement activation and decreased synovial vascularization in males but not in females with OA. Future studies should test whether synovial fluid complement activation suppresses synovial angiogenesis and identify mechanisms accounting for C5-related sex-differences in synovial fluid complement activation in patients with knee OA.

Vascularization of Cell-Laden Microfibres by Femtosecond Laser Processing

To face the increasing demand for organ transplantation, currently the development of tissue engineering appears as the best opportunity to effectively regenerate functional tissues and organs. However, these approaches still face the lack of an efficient method to produce an efficient vascularization system. To answer these issues, the formation of an intra-volume channel within a three-dimensional, scaffold free, mature, and cell-covered collagen microfibre is here investigated through laser-induced cavitation. An intra-volume channel was formed upon irradiation with a near-infrared, femtosecond laser beam, focused with a high numerical aperture lens. The laser beam directly crossed the surface of a dense and living-cell bilayer and was focused behind the bilayer to induce channel formation in the hydrogel core while preserving the cell bilayer. Channel formation was assessed through confocal microscopy. Channel generation inside the hydrogel core was enhanced by the formation of voluminous cavitation bubbles with a lifetime longer than 30 s, which also improved intra-volume channel durability. Twenty-four hours after laser processing, cellular viability dropped due to a lack of sufficient hydration for processing longer than 10 min. However, the processing automation could drastically reduce the cellular mortality, this way enabling the formation of hollowed microfibres with a high density of living-cell outer bilayer.

SMAD 3, Integrin and VEGF Expression in a Periodontal Ligament During Orthodontic Tooth Movement Induced by Hyperbaric Oxygen Therapy and Stichopus hermanii

Purpose

The aim of this study is to analyze SMAD 3, integrin and VEGF expressions in the periodontal ligament during orthodontic tooth movement induced by hyperbaric oxygen therapy and Stichopus hermanii.

Materials and Methods

Thirty Cavia cobaya were divided into 5 groups, namely, a normal control group (KN) without installation of helical springs or administration of HBOT and Stichopus hermanii gel. The negative control K(-) had helical spring without administration of HBOT and Stichopus hermanii gel for 14 days, while P1 had helical spring for 14 days then on day 3–14, Stichopus hermanii gel was added. Also, the helical spring was installed in P2 for 14 days then on day 8–14, HBOT 2.4 ATA was added 3 × 30 minutes a day, while P3 had helical spring for 14 days then on day 3–14, the gel was applied, and on day 8–14, HBOT 2.4 ATA was administered 3 × 30 minutes a day. Furthermore, SMAD3, integrin, and VEGF expressions were examined using immunohistochemical staining.

Results

SMAD3, integrins, and VEGF expressions showed significant differences within the groups. The combination of HBOT and Stichopus hermanii increased the expression of SMAD3 and VEGF compared to the single administration of Stichopus hermanii. The combination treatment also decreased integrin expression compared to a single HBOT administration.

Conclusion

The combination of HBOT and Stichopus hermanii increases the expression of SMAD3, integrins, and VEGF compared to control but did not show significant differences compared to single HBOT treatment.

In vitro dynamic perfusion of prevascularized OECs-DBMs (outgrowth endothelial progenitor cell - demineralized bone matrix) complex fused to recipient vessels in an internal inosculation manner

The current research on seed cells and scaffold materials of bone tissue engineering has achieved milestones. Nevertheless, necrosis of seed cells in center of bone scaffold is a bottleneck in tissue engineering. Therefore, this study aimed to investigate the in vivo inosculation mechanism of recipient microvasculature and prevascularized outgrowth endothelial progenitor cells (OECs)-demineralized bone matrix (DBM) complex. A dorsal skinfold window-chamber model with tail vein injection of Texas red-dextran was established to confirm the optimal observation time of microvessels. OECs-DBM complex under static and dynamic perfusion culture was implanted into the model to analyze vascularization. OECs-DBM complex was harvested on 12th day for HE staining and fluorescent imaging. The model was successfully constructed, and the most appropriate time to observe microvessels was 15 min after injection. The ingrowth of recipient microvessels arcoss the border of OECs-DBM complex increased with time in both groups, and more microvessels across the border were observed in dynamic perfusion group on 3rd, 5th, 7th day. Fluorescent integrated density of border in dynamic perfusion group was higher at all-time points, and the difference was more significant in central area. Fluorescent imaging of OECs-DBM complex exhibited that no enhanced green fluorescent protein-positive cells were found beyond the verge of DBM scaffold in both groups. In vitro prevascularization by dynamic perfusion culture can increase and accelerate the blood perfusion of OECs-DBM complex obtained from recipient microvasculature by internal inosculation. Accordingly, this approach may markedly contribute to the future success of tissue engineering applications in clinical practice.

Malignant pleural mesothelioma nodules remodel their surroundings to vascularize and grow

Background

The microanatomical steps of malignant pleural mesothelioma (MPM) vascularization and the resistance mechanisms to anti-angiogenic drugs in MPM are unclear.

Methods

We investigated the vascularization of intrapleurally implanted human P31 and SPC111 MPM cells. We also assessed MPM cell's motility, invasion and interaction with endothelial cells in vitro.

Results

P31 cells exhibited significantly higher two-dimensional (2D) motility and three-dimensional (3D) invasion than SPC111 cells in vitro. In co-cultures of MPM and endothelial cells, P31 spheroids permitted endothelial sprouting (ES) with minimal spatial distortion, whereas SPC111 spheroids repealed endothelial sprouts. Both MPM lines induced the early onset of submesothelial microvascular plexuses covering large pleural areas including regions distant from tumor colonies. The development of these microvascular networks occurred due to both intussusceptive angiogenesis (IA) and ES and was accelerated by vascular endothelial growth factor A (VEGF-A)-overexpression. Notably, SPC111 colonies showed different behavior to P31 cells. P31 nodules incorporated tumor-induced capillary plexuses from the earliest stages of tumor formation. P31 cells deposited a collagenous matrix of human origin which provided "space" for further intratumoral angiogenesis. In contrast, SPC111 colonies pushed the capillary plexuses away and thus remained avascular for weeks. The key event in SPC111 vascularization was the development of a desmoplastic matrix of mouse origin. Continuously invaded by SPC111 cells, this matrix transformed into intratumoral connective tissue trunks, providing a route for ES from the diaphragm.

Conclusions

Here, we report two distinct growth patterns of orthotopically implanted human MPM xenografts. In the invasive pattern, MPM cells invade and thus co-opt peritumoral capillary plexuses. In the pushing/desmoplastic pattern, MPM cells induce a desmoplastic response within the underlying tissue which allows the ingrowth of a nutritive vasculature from the pleura.

Application Status of Sacrificial Biomaterials in 3D Bioprinting

Additive manufacturing, also known as three-dimensional (3D) printing, relates to several rapid prototyping (RP) technologies, and has shown great potential in the manufacture of organoids and even complex bioartificial organs. A major challenge for 3D bioprinting complex org unit ans is the competitive requirements with respect to structural biomimeticability, material integrability, and functional manufacturability. Over the past several years, 3D bioprinting based on sacrificial templates has shown its unique advantages in building hierarchical vascular networks in complex organs. Sacrificial biomaterials as supporting structures have been used widely in the construction of tubular tissues. The advent of suspension printing has enabled the precise printing of some soft biomaterials (e.g., collagen and fibrinogen), which were previously considered unprintable singly with cells. In addition, the introduction of sacrificial biomaterials can improve the porosity of biomaterials, making the printed structures more favorable for cell proliferation, migration and connection. In this review, we mainly consider the latest developments and applications of 3D bioprinting based on the strategy of sacrificial biomaterials, discuss the basic principles of sacrificial templates, and look forward to the broad prospects of this approach for complex organ engineering or manufacturing.

The Relationship between Osteoinduction and Vascularization: Comparing the Ectopic Bone Formation of Five Different Calcium Phosphate Biomaterials

Objective: The objective of this study is to compare the bone induction of five kinds of calcium phosphate (Ca-P) biomaterials implanted in mice and explore the vascularization and particle-size-related osteoinductive mechanism. Methods: The following five kinds of Ca-P biomaterials including hydroxyapatite (HA) and/or tricalcium phosphate (TCP) were implanted in the muscle of 30 BALB/c mice (n = 6): 20 nm HA (20HA), 60 nm HA (60HA), 12 µm HA (12HA), 100 nm TCP (100TCP) and 12 µm HA + 100 nm TCP (HATCP). Then, all animals were put on a treadmill to run 30 min at a 6 m/h speed each day. Five and ten weeks later, three mice of each group were killed, and the samples were harvested to assess the osteoinductive effects by hematoxylin eosin (HE), Masson’s trichrome and safranine−fast green stainings, and the immunohistochemistry of the angiogenesis and osteogenesis markers CD31 and type I collagen (ColI). Results: The numbers of blood vessels were 139 ± 29, 118 ± 25, 78 ± 15, 65 ± 14 in groups HATCP, 100TCP, 60HA and 20HA, respectively, which were significantly higher than that of group 12HA (12 ± 5) in week 5 (p < 0.05). The area percentages of new bone tissue were (7.33 ± 1.26)% and (8.49 ± 1.38)% in groups 100TCP and HATCP, respectively, which were significantly higher than those in groups 20HA (3.27 ± 0.38)% and 60HA (3.43 ± 0.27)% (p < 0.05); however, no bone tissue was found in group 12HA 10 weeks after transplantation. The expression of CD31 was positive in new blood vessels, and the expression of ColI was positive in new bone tissue. Conclusions: Nanoscale Ca-P biomaterials could induce osteogenesis in mice muscle, and the osteoinductive effects of TCP were about 124% higher than those of 20HA and 114% higher than those of 60HA. The particle size of the biomaterials affected angiogenesis and osteogenesis. There was a positive correlation between the number of blood vessels and the area percentage of new bone tissue; therefore, osteoinduction is closely related to vascularization. Our results provide an experimental basis for the synthesis of calcium−phosphorus matrix composites and for further exploration of the osteoinductive mechanism.

The Structure and Function of Next-Generation Gingival Graft Substitutes-A Perspective on Multilayer Electrospun Constructs with Consideration of Vascularization

There is a shortage of suitable tissue-engineered solutions for gingival recession, a soft tissue defect of the oral cavity. Autologous tissue grafts lead to an increase in morbidity due to complications at the donor site. Although material substitutes are available on the market, their development is early, and work to produce more functional material substitutes is underway. The latter materials along with newly conceived tissue-engineered substitutes must maintain volumetric form over time and have advantageous mechanical and biological characteristics facilitating the regeneration of functional gingival tissue. This review conveys a comprehensive and timely perspective to provide insight towards future work in the field, by linking the structure (specifically multilayered systems) and function of electrospun material-based approaches for gingival tissue engineering and regeneration. Electrospun material composites are reviewed alongside existing commercial material substitutes’, looking at current advantages and disadvantages. The importance of implementing physiologically relevant degradation profiles and mechanical properties into the design of material substitutes is presented and discussed. Further, given that the broader tissue engineering field has moved towards the use of pre-seeded scaffolds, a review of promising cell options, for generating tissue-engineered autologous gingival grafts from electrospun scaffolds is presented and their potential utility and limitations are discussed.

Spindle-Like Zinc Silicate Nanoparticles Accelerating Innervated and Vascularized Skin Burn Wound Healing

The treatment of severe burn injuries is a crucial challenge in skin tissue engineering. Severe burns are always accompanied with large-area neurovascular networks damage, leading to the lack of excitation functions and difficulty in self-healing. Therefore, it is of great importance to develop biomaterials which can not only promote wound healing but also simultaneously reconstruct cutaneous neurovascular networks. In this study, Zn₂ SiO₄ (ZS) nanoparticles-incorporated bioactive nanofibrous scaffolds are designed for innervated and vascularized skin burn wound healing. ZS nanoparticles with spindle-like morphology are synthesized via a facile hydrothermal method. The incorporation of ZS nanoparticles endows the scaffolds with excellent angiogenic and neurogenic activities in vitro. Additionally, in vivo results show that the ZS nanoparticles-incorporated scaffolds have favorable re-epithelialization, innervation, and vascularization abilities through local release of bioactive Zn and Si ions from ZS nanoparticles, leading to rapid wound healing featuring with newly formed blood vessels and nerve fibers. Taken together, this study suggests that the spindle-like ZS nanoparticles are useful bioactive agents for stimulating vascularization and innervation of functional skin repair. The bioactive inorganic nanoparticles may be used for multifunctional tissue regeneration.

Kidney Decellularized Extracellular Matrix Enhanced the Vascularization and Maturation of Human Kidney Organoids

Kidney organoids derived from human pluripotent stem cells (hPSCs) have extensive potential for disease modelling and regenerative medicine. However, the limited vascularization and immaturity of kidney organoids have been still remained to overcome. Extracellular matrix (ECM) can provide mechanical support and a biochemical microenvironment for cell growth and differentiation. Here in vitro methods using a kidney decellularized extracellular matrix (dECM) hydrogel to culture hPSC-derived kidney organoids, which have extensive vascular network and their own endothelial cells, are reported. Single-cell transcriptomics reveal that the vascularized kidney organoids cultured using the kidney dECM have more mature patterns of glomerular development and higher similarity to human kidney than those cultured without the kidney dECM. Differentiation of α-galactosidase A (GLA)-knock-out hPSCs generated using CRISPR/Cas9 into kidney organoids by the culture method using kidney dECM efficiently recapitulate Fabry nephropathy with vasculopathy. Transplantation of kidney organoids with kidney dECM into kidney of mouse accelerates the recruitment of endothelial cells from the host mouse kidney and maintains vascular integrity with the more organized slit diaphragm-like structures than those without kidney dECM. The kidney dECM methodology for inducing extensive vascularization and maturation of kidney organoids can be applied to studies for kidney development, disease modeling, and regenerative medicine.

[No infected union of subtrochanteric fracture of femur, treated with autograft and plate]

Hip fractures are considered a public health problem in the world. Among hip fractures we find subtrochanteric fractures that are defined as proximal femur fractures located in the trochanteric region within 5 cm below the lesser trochanter; and they have an approximate incidence of 15 to 20 per 100,000 people. The objective of this case is to report the success of the reconstruction of an infected subtrochanteric fracture, with a non-vascularized fibular segment and a distal femur condylar support plate. Clinical case: 41-year-old male patient suffering from a right subtrochanteric fracture as a result of a traffic accident that required the use of osteosynthesis material. With subsequent rupture of the cephalomedullary nail in its proximal third, non-union of the fracture and infections at the fracture site. He was treated with multiple surgical lavages, antibiotic therapy, and an unconventional orthopedic and surgical procedure, such as the use of a distal femur condylar support plate and an endomedullary bone graft with a 10-cm segment of non-vascularized fibula. Patient with satisfactory and favorable evolution.

Customizable Microfluidic Origami Liver-on-a-Chip (oLOC)

The design and manufacture of an origami-based liver-on-a-chip device are presented, together with demonstrations of the chip's effectiveness at recapitulating some of the liver's key in vivo architecture, physical microenvironment, and functions. Laser-cut layers of polyimide tape are folded together with polycarbonate nanoporous membranes to create a stack of three adjacent flow chambers separated by the membranes. Endothelial cells are seeded in the upper and lower flow chambers to simulate sinusoids, and hepatocytes are seeded in the middle flow chamber. Nutrients and metabolites flow through the simulated sinusoids and diffuse between the vascular pathways and the hepatocyte layers, mimicking physiological microcirculation. Studies of cell viability, metabolic functions, and hepatotoxicity of pharmaceutical compounds show that the endothelialized liver-on-a-chip model is conducive to maintaining hepatocyte functions and evaluation of the hepatotoxicity of drugs. Our unique origami approach speeds chip development and optimization, effectively simplifying the laboratory-scale fabrication of on-chip models of human tissues without necessarily reducing their structural and functional sophistication.

Microvascular development in the rat arteriovenous loop model in vivo-A step by step intravital microscopy analysis

The arteriovenous (AV) loop model is a key technique to solve one of the major problems of tissue engineering-providing adequate vascular support for a tissue construct of significant size. However, the molecular and cellular mechanisms of vascularization and factors influencing the generation of new tissue in the AV loop are still poorly understood. We previously established a novel intravital microscopy approach to study these events. In this study, we implanted our observation chamber filled with two types of hydrogels such as fibrin and methacrylate gelatin (GelMA) and performed intravital microscopy (IVM) on days 7, 14, and 21. Initial microvessel formation was observed in GelMA on day 14, while the vessel network showed clear indicators of network rearrangement and maturation on day 21. No visible microvessels were observed in fibrin. The chambers were explanted on day 21. Histological examination revealed higher numbers of microvessels in GelMA compared to fibrin, while the AV loop was thrombosed in all fibrin constructs, possibly due to matrix degradation. GelMA proved to be an ideal matrix for IVM studies in the AV loop model due to its slow degradation and transparency. This IVM model can be employed as a novel tool for live and thus faster comprehension of crucial events in the tissue regeneration process, which can improve tissue engineering application.

Signature of the vascular tumor microenvironment as a marker of the therapeutic response to doxorubicin in a preclinical model of osteosarcoma

Predicting a response of osteosarcoma patients to chemotherapy, such as doxorubicin or high-dose methotrexate cocktail, remains a challenge in the clinic. Moreover, the prognostic value of currently used necrosis analysis is debatable. New markers of the therapeutic response or the prognostic response are urgently needed. The microenvironment plays a key role in the vascularization of highly heterogeneous tumors. Using the syngeneic MOS-J mouse model of osteosarcoma, we focused our study on the immunohistochemistry of tumor vascularization in order to identify new vessel markers, and to search for potential markers of the therapeutic response. Endomucin+, CD31+, and α-SMA+-positive elements were quantified in control (n=6) and doxorubicin-treated (n=6) mice in three different intra-tumor locations. We also used co-labeling to assess CD31+/Endomucin+ and CD31+/α-SMA+ co-expression. We identified a central tumor zone with a low vascularization profile for all of these markers. We identified two distinct types of vessels: CD31+/Endomucin+ vessels with a sprouting, neo-angiogenic, interlaced appearance, and CD31+/α-SMA+ vessel with a well-defined, mature structure. Doxorubicin appeared to reduce CD31+ expression in the tumor invasion front. In the doxorubicin-sensitive model, there were four times more CD31+/α-SMA+ elements than in the poorly responsive model. Therefore, we propose a methodology based on immunohistochemistry and multiplexed immunofluorescence to use endomucin as a promising new vascular marker in the osteosarcoma model. Moreover, our results suggest that CD31+/α-SMA+ vessels could be considered to be indicators of vasculature normalization and they may be used as specific markers of a good therapeutic response.

Integrating Additive Manufacturing Techniques to Improve Cell-Based Implants for the Treatment of Type 1 Diabetes

The increasing global prevalence of endocrine diseases like type 1 diabetes mellitus (T1DM) elevates the need for cellular replacement approaches, which can potentially enhance therapeutic durability and outcomes. Central to any cell therapy is the design of delivery systems that support cell survival and integration. In T1DM, well-established fabrication methods have created a wide range of implants, ranging from 3D macro-scale scaffolds to nano-scale coatings. These traditional methods, however, are often challenged by their inherent limitations in reproducible and discrete fabrication, particularly when scaling to the clinic. Additive manufacturing (AM) techniques provide a means to address these challenges by delivering improved control over construct geometry and microscale component placement. While still early in development in the context of T1DM cellular transplantation, the integration of AM approaches serves to improve nutrient material transport, vascularization efficiency, and the accuracy of cell, matrix, and local therapeutic placement. This review highlights current methods in T1DM cellular transplantation and the potential of AM approaches to overcome these limitations. In addition, emerging AM technologies and their broader application to cell-based therapy are discussed.

Biodegradable Inks in Indirect Three-Dimensional Bioprinting for Tissue Vascularization

Mature vasculature is important for the survival of bioengineered tissue constructs, both in vivo and in vitro; however, the fabrication of fully vascularized tissue constructs remains a great challenge in tissue engineering. Indirect three-dimensional (3D) bioprinting refers to a 3D printing technique that can rapidly fabricate scaffolds with controllable internal pores, cavities, and channels through the use of sacrificial molds. It has attracted much attention in recent years owing to its ability to create complex vascular network-like channels through thick tissue constructs while maintaining endothelial cell activity. Biodegradable materials play a crucial role in tissue engineering. Scaffolds made of biodegradable materials act as temporary templates, interact with cells, integrate with native tissues, and affect the results of tissue remodeling. Biodegradable ink selection, especially the choice of scaffold and sacrificial materials in indirect 3D bioprinting, has been the focus of several recent studies. The major objective of this review is to summarize the basic characteristics of biodegradable materials commonly used in indirect 3D bioprinting for vascularization, and to address recent advances in applying this technique to the vascularization of different tissues. Furthermore, the review describes how indirect 3D bioprinting creates blood vessels and vascularized tissue constructs by introducing the methodology and biodegradable ink selection. With the continuous improvement of biodegradable materials in the future, indirect 3D bioprinting will make further contributions to the development of this field.

The Evolution of Complex Muscle Cell In Vitro Models to Study Pathomechanisms and Drug Development of Neuromuscular Disease

Many neuromuscular disease entities possess a significant disease burden and therapeutic options remain limited. Innovative human preclinical models may help to uncover relevant disease mechanisms and enhance the translation of therapeutic findings to strengthen neuromuscular disease precision medicine. By concentrating on idiopathic inflammatory muscle disorders, we summarize the recent evolution of the novel in vitro models to study disease mechanisms and therapeutic strategies. A particular focus is laid on the integration and simulation of multicellular interactions of muscle tissue in disease phenotypes in vitro. Finally, the requirements of a neuromuscular disease drug development workflow are discussed with a particular emphasis on cell sources, co-culture systems (including organoids), functionality, and throughput.

An exceptional neurovascular system in abelisaurid theropod skull: New evidence from Skorpiovenator bustingorryi

Abelisaurids were one of the most successful theropod dinosaurs during Cretaceous times. They are featured by numerous derived skull traits, such as heavily ornamented bones, short and tall snout, and a strongly thickened cranial roof. Furthermore, nasals are distinctive on having two distinct nasal patterns: strongly transversely convex and heavily sculptured (e.g., Carnotaurus), and transversely concave, with marked bilateral crests and poorly sculptured surfaces (e.g., Rugops). Independently of the pattern, some abelisaurid nasals (e.g., Rugops) show a distinctive row of large foramina on the dorsal surface, which were in general associated to skin structures (scales). Skorpiovenator bustingorryi is a derived abelisaurid coming from the upper Cretaceous beds of northwestern Patagonia, represented by an almost complete skeleton including a well-preserved skull. Particularly, the skull of Skorpiovenator shows nasal bones characterized by being transversely concave, rimmed by lateral crests and with a conspicuous row of foramina on the dorsal surface. But more interesting is that the skull roof also exhibits a row of large foramina that seem to be continuous with the previous nasal foramina. CT scans made on the skull corroborates a novel feature within theropods: the nasal foramina on the external surface are linked to an internal canal that runs across the nasal bones. We compared this feature with CT scans of Carnotaurus and revealed that it also possess an internal system as in Skorpiovenator, but being notably smaller. The symmetry and disposition of the foramina in the nasal and skull roof bones of Skorpiovenator would indicate a neurovascular correlate (i.e., blood vessels and nerves), probably to the lateral nasal and supraorbital vessels and the trigeminal nerve. The biological significance of such neurovascular system can be conjectured from several hypotheses. A possible one involves an enhanced blood volume in these bones linked to a zone of thermal exchange, which may help avoid overheat of encephalic tissues. Another plausible hypothesis takes into account the presence of display skin structures in which blood volume nourished the mineralized skin, which would have a role in intraspecific communication. However, other more speculative explanations should not be discarded such as a correlation with integumentary sensory organs.

State of the field: cellular and exosomal therapeutic approaches in vascular regeneration

Pathologies of the vasculature including the microvasculature are often complex in nature, leading to loss of physiological homeostatic regulation of patency and adequate perfusion to match tissue metabolic demands. Microvascular dysfunction is a key underlying element in the majority of pathologies of failing organs and tissues. Contributing pathological factors to this dysfunction include oxidative stress, mitochondrial dysfunction, endoplasmic reticular (ER) stress, endothelial dysfunction, loss of angiogenic potential and vascular density, and greater senescence and apoptosis. In many clinical settings, current pharmacologic strategies use a single or narrow targeted approach to address symptoms of pathology rather than a comprehensive and multifaceted approach to address their root cause. To address this, efforts have been heavily focused on cellular therapies and cell-free therapies (e.g., exosomes) that can tackle the multifaceted etiology of vascular and microvascular dysfunction. In this review, we discuss 1) the state of the field in terms of common therapeutic cell population isolation techniques, their unique characteristics, and their advantages and disadvantages, 2) common molecular mechanisms of cell therapies to restore vascularization and/or vascular function, 3) arguments for and against allogeneic versus autologous applications of cell therapies, 4) emerging strategies to optimize and enhance cell therapies through priming and preconditioning, and, finally, 5) emerging strategies to bolster therapeutic effect. Relevant and recent clinical and animal studies using cellular therapies to restore vascular function or pathologic tissue health by way of improved vascularization are highlighted throughout these sections.

Internal vascular channel architecture in human auditory ossicles

The vascular supply of the human auditory ossicles has long been of anatomical and clinical interest. While the external blood supply has been well‐described, there is only limited information available regarding the internal vascular architecture of the ossicles, and there has been little comparison of this between individuals. Based on high‐resolution micro‐CT scans, we made reconstructions of the internal vascular channels and cavities in 12 sets of ossicles from elderly donors. Despite considerable individual variation, a common basic pattern was identified. The presence of channels within the stapes footplate was confirmed. The long process of the incus and neck of the stapes showed signs of bony erosion in all specimens examined. More severe erosion was associated with interruption of some or all of the main internal vascular channels which normally pass down the incudal long process; internal excavation of the proximal process could interrupt vascular channels in ossicles which did not appear to be badly damaged from exterior inspection. An awareness of this possibility may be helpful for surgical procedures that compromise the mucosal blood supply. We also calculated ossicular densities, finding that the malleus tends to be denser than the incus. This is mainly due to a lower proportion of vascular channels and cavities within the malleus.

Strategies for Enhancing Vascularization of Biomaterial-Based Scaffold in Bone Regeneration

Despite the recent advances in reconstructive orthopedics; fracture union is a challenge to bone regeneration. Concurrent angiogenesis is a complex process governed by events, delicately entwined with osteogenesis. However, poorly perfused scaffolds have lower success rates; necessitating the need for a better vascular component, which is important for the delivery of nutrients, oxygen, waste elimination, recruitment of cells for optimal bone repair. This review highlights the latest strategies to promote biomaterial-based scaffold vascularization by incorporation of cells, growth factors, inorganic ions, etc. into natural or synthetic polymers, ceramic materials, or composites of organic and inorganic compounds. Furthermore, it emphasizes structural modifications, biophysical stimuli, and natural molecules to fabricate scaffolds aiding the genesis of dense vascularization following their implantation to manifest a compatible regenerative microenvironment without graft rejection.

3D bioprinted, vascularized neuroblastoma tumor environment in fluidic chip devices for precision medicine drug testing

Neuroblastoma is an extracranial solid tumor which develops in early childhood and still has a poor prognosis. One strategy to increase cure rates is the identification of patient-specific drug responses in tissue models that mimic the interaction between patient cancer cells and tumor environment. We therefore developed a perfused and micro-vascularized tumor-environment model that is directly bioprinted into custom-manufactured fluidic chips. A gelatin-methacrylate/fibrin-based matrix containing multiple cell types mimics the tumor-microenvironment that promotes spontaneous micro-vessel formation by embedded endothelial cells. We demonstrate that both, adipocyte- and iPSC-derived mesenchymal stem cells can guide this process. Bioprinted channels are coated with endothelial cells post printing to form a dense vessel - tissue barrier. The tissue model thereby mimics structure and function of human soft tissue with endothelial cell-coated larger vessels for perfusion and micro-vessel networks within the hydrogel-matrix. Patient-derived neuroblastoma spheroids are added to the matrix during the printing process and grown for more than two weeks. We demonstrate that micro-vessels are attracted by and grow into tumor spheroids and that neuroblastoma cells invade the tumor-environment as soon as the spheroids disrupt. In summary, we describe the first bioprinted, micro-vascularized neuroblastoma - tumor-environment model directly printed into fluidic chips and a novel medium-throughput biofabrication platform suitable for studying tumor angiogenesis and metastasis in precision medicine approaches in future.

Graphene Oxide Framework Structures and Coatings: Impact on Cell Adhesion and Pre-Vascularization Processes for Bone Grafts

Graphene oxide (GO) is a promising material for bone tissue engineering, but the validation of its molecular biological effects, especially in the context of clinically applied materials, is still limited. In this study, we compare the effects of graphene oxide framework structures (F-GO) and reduced graphene oxide-based framework structures (F-rGO) as scaffold material with a special focus on vascularization associated processes and mechanisms in the bone. Highly porous networks of zinc oxide tetrapods serving as sacrificial templates were used to create F-GO and F-rGO with porosities >99% consisting of hollow interconnected microtubes. Framework materials were seeded with human mesenchymal stem cells (MSC), and the cell response was evaluated by confocal laser scanning microscopy (CLSM), deoxyribonucleic acid (DNA) quantification, real-time polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and alkaline phosphatase activity (ALP) to define their impact on cellular adhesion, osteogenic differentiation, and secretion of vascular growth factors. F-GO based scaffolds improved adhesion and growth of MSC as indicated by CLSM and DNA quantification. Further, F-GO showed a better vascular endothelial growth factor (VEGF) binding capacity and improved cell growth as well as the formation of microvascular capillary-like structures in co-cultures with outgrowth endothelial cells (OEC). These results clearly favored non-reduced graphene oxide in the form of F-GO for bone regeneration applications. To study GO in the context of a clinically used implant material, we coated a commercially available xenograft (Bio-Oss® block) with GO and compared the growth of MSC in monoculture and in coculture with OEC to the native scaffold. We observed a significantly improved growth of MSC and formation of prevascular structures on coated Bio-Oss®, again associated with a higher VEGF binding capacity. We conclude that graphene oxide coating of this clinically used, but highly debiologized bone graft improves MSC cell adhesion and vascularization.

Biomaterial Scaffolds Made of Chemically Cross-Linked Gelatin Microsphere Aggregates (C-GMSs) Promote Vascularized Bone Regeneration

Various scaffolding systems have been attempted to facilitate vascularization in tissue engineering by optimizing biophysical properties (e.g., vascular-like structures, porous architectures, surface topographies) or loading biochemical factors (e.g., growth factors, hormones). However, vascularization during ossification remains an unmet challenge that hampers the repair of large bone defects. In this study, reconstructing vascularized bones in situ against critical-sized bone defects is endeavored using newly developed scaffolds made of chemically cross-linked gelatin microsphere aggregates (C-GMSs). The rationale of this design lies in the creation and optimization of cell-material interfaces to enhance focal adhesion, proliferation, and function of anchorage-dependent functional cells. In vitro trials are carried out by coculturing human aortic endothelial cells (HAECs) and murine osteoblast precursor cells (MC3T3-E1) within C-GMS scaffolds, in which endothelialized bone-like constructs are yielded. Angiogenesis and osteogenesis induced by C-GMSs scaffold are further confirmed via subcutaneous-embedding trials in nude mice. In situ trials for the repair of critical-sized femoral defects are subsequently performed in rats. The acellular C-GMSs with interconnected macropores, exhibit the capability to recruit the endogenous cells (e.g., bone-forming cells, vascular forming cells, immunocytes) and then promote vascularized bone regeneration as well as integration with host bone.

Characteristic Assessment of Angiographies at Different Depths with AS-OCTA: Implication for Functions of Post-Trabeculectomy Filtering Bleb

This study aimed to analyze the quantitative vascular biomarkers of filtering bleb function at different depths using anterior segment optical coherence tomography angiography (AS-OCTA). This cross-sectional study is registered on Clinicaltrails.gov (NCT 04515017). Forty-six eyes with primary open-angle glaucoma that had undergone trabeculectomy with mitomycin-C for more than six months were included. Vessel density (VD) and vessel diameter index (VDI) in the superficial layer (SL), Tenon’s layer (TL), and deep layer (DL) of the bleb were obtained. The VD and VDI were higher in the failure group (both p = 0.000). Significant correlations were found between the SL, TL, DL’s VDI, and IOP in the success group (p = 0.013, 0.016, 0.031, respectively). The VD of the TL and DL were related to IOP in the failure group (p = 0.012, 0.009). Tenon’s VD (TVD) and Tenon’s VDI (TVDI) correlated with IOP adjusting for TVD, TVDI, and the Indiana Bleb Appearance Grading Scale (IBAGS) (p = 0.009, 0.043) or Kenfeld grading system (KGS) (p = 0.011, 0.016). The area under curve (AUC) of the TVD, TVDI, IBAGS, and KGS to predict surgery failure were 0.960, 0.925, 0.770, and 0.850. AS-OCTA realized the quantitative evaluation of vessels, especially the invisible vascularity beneath the conjunctiva. TVD and TVDI as detected by AS-OCTA better reflected bleb function than conventional grading systems.

Vascularized Lung Cancer Model for Evaluating the Promoted Transport of Anticancer Drugs and Immune Cells in an Engineered Tumor Microenvironment

The tumor microenvironment (TME) is the environment around the tumor, including blood vessels, immune cells, fibroblasts, signaling molecules, and the extracellular matrix (ECM). Owing to its component interactions, the TME influences tumor growth and drug delivery in a highly complex manner. Although several vascularized cancer models are developed to mimic the TME in vitro, these models cannot comprehensively reflect blood vessel-tumor spheroid interactions. Here, a method for inducing controlled tumor angiogenesis by engineering the microenvironment is presented. The interstitial flow direction regulates the direction of capillary sprouting, showing that angiogenesis occurs in the opposite direction of flow, while the existence of lung fibroblasts affects the continuity and lumen formation of sprouted capillaries. The vascularized tumor model shows enhanced delivery of anticancer drugs and immune cells to the tumor spheroids because of the perfusable vascular networks. The possibility of capillary embolism using anticancer drug-conjugated liquid metal nanoparticles is investigated using the vascularized tumor model. This vascularized tumor platform can aid in the development of effective anticancer drugs and cancer immunotherapy.

Impact of Endothelial Progenitor Cells in the Vascularization of Osteogenic Scaffolds

The microvascular endothelial network plays an important role in osteogenesis, bone regeneration and bone tissue engineering. Endothelial progenitor cells (EPCs) display a high angiogenic and vasculogenic potential. The endothelialization of scaffolds with endothelial progenitor cells supports vascularization and tissue formation. In addition, EPCs enhance the osteogenic differentiation and bone formation of mesenchymal stem cells (MSCs). This study aimed to investigate the impact of EPCs on vascularization and bone formation of a hydroxyapatite (HA) and beta-tricalcium phosphate (ß-TCP)–fibrin scaffold. Three groups were designed: a scaffold-only group (A), a scaffold and EPC group (B), and a scaffold and EPC/MSC group (C). The HA/ß–TCP–fibrin scaffolds were placed in a porous titanium chamber permitting extrinsic vascularization from the surrounding tissue. Additionally, intrinsic vascularization was achieved by means of an arteriovenous loop (AV loop). After 12 weeks, the specimens were explanted and investigated by histology and CT. We were able to prove a strong scaffold vascularization in all groups. No differences regarding the vessel number and density were detected between the groups. Moreover, we were able to prove bone formation in the coimplantation group. Taken together, the AV loop is a powerful tool for vascularization which is independent from scaffold cellularization with endothelial progenitor cells’ prior implantation.

Changes in peripapillary and macular vascular density after laser selective trabeculoplasty: an optical coherence tomography angiography study

OBJECTIVES

To determine the effect of laser trabeculoplasty on peripapillary retinal nerve fibre layer thickness (RNFL), fovea avascular zone (FAZ), peripapillary and macular vessel density (VD) in glaucoma using with optical coherence tomography angiography (OCT-A).

METHODS

This was a prospective observational study performed at the Glaucoma Research Centre, Montchoisi Clinic, Lausanne, Switzerland. Thirty-seven eyes with primary open-angle glaucoma from 21 patients were included. Optical coherence tomography angiography (OCT-A) scans were performed before laser trabeculoplasty and at 2 and 6 months after the procedure. AngioVue AngioAnalytic (Optovue Inc, Fremont, CA, USA) software was used to analyse the RNFL, FAZ, peripapillary and macular VD. Changes were analysed using mixed models, controlling for intraocular pressure (IOP) and signal strength index (SSI) variations.

RESULTS

Mean IOP decreased from 18.5 (±3.7) mmHg at baseline to 15.6 (±2.7) mmHg after 2 months (-15.3%; p < 0.001). No significant changes in RNFL thickness were noted following laser trabeculoplasty. Changes in peripapillary VD were mostly nonsignificant. Parafoveal (p = 0.001) and perifoveal VD (p = 0.025) significantly increased at 2 months, before reverting to near-baseline values at 6 months. No significant changes were observed in foveal parameters. Retinal nerve fibre layer thickness (RNFL) and VD changes were independent from IOP, but SSI had a significant influence on VD.

CONCLUSIONS

Following laser trabeculoplasty, peripapillary and macular VD temporarily increased before returning to near-baseline values by 6 months. No correlation was found between microvascular fluctuations and IOP, and no significant effect of laser trabeculoplasty on VD or RNFL was observed at 6 months despite persistent IOP reduction. Further research is warranted to understand its exact causes and clinical relevance.

Influence of Genotype on Endometrial Angiogenesis during Early Pregnancy in Piau and Commercial Line Gilts

This study aimed to evaluate the endometrial angiogenesis of pregnant commercial line and Piau gilts during early pregnancy. We used 27 gilts, divided into three groups according to the type of mating: Commercial (n = 9), commercial line females mated with commercial line males; Cross-mated (n = 9), Piau females mated with commercial line males; and Piau (n = 9), Piau females mated with Piau males. Each group was divided into three subgroups based on gestational age at the time of slaughter (7, 15, and 30 days of pregnancy). Immediately after slaughter, endometrial samples were obtained for histological evaluation and for analysis of the relative transcript abundance (RTA) of angiogenesis-related genes (HIF1α, FGF9, ANG1, TEK, VEGFA, ANGPT1, and ANGPT2). The number of endometrial glands was similar among groups but decreased with gestational age (p < 0.05). Piau females showed a higher number of blood vessels (p < 0.05) at 7 and 15 days of pregnancy, but no differences were observed among groups at 30 days, suggesting an influence of the male genotype on the pattern of uterine vascularization. There were no differences among groups for RTA of the FGF9, HIF1α, TEK, VEGFA, ANGPT1, and ANGPT2 genes. The HIF1α-gene RTA was higher at 7 and 15 days of pregnancy; for TEK and ANGPT1, the RTA was higher at 15 days of pregnancy; and the RTA of VEGFA and ANGPT2 genes were higher at 30 days of pregnancy. The ANG1 RTA was similar for pregnancies in the commercial and Piau groups but was higher (p < 0.05) at 15 days in the Cross-mated group, suggesting an interaction between genotypes. Overall, the pattern found for the RTA of angiogenesis-related genes was similar among the groups in this study, although some phenotypic differences could be noted, such as the highest number of blood vessels being found during early pregnancy of Piau gilts. The results of the gene RTA when crossed with phenotypic data led to conclusions that are conflicting with those reported in the literature. However, noteworthy is that angiogenesis is a complex process in which the balance between stimulatory and inhibitory factors may be related to time.

A multi-scale/multi-physics model for the theoretical study of the vascular configuration of retinal capillary plexuses based on OCTA data

The retinal tissue is highly metabolically active and is responsible for translating the visual stimuli into electrical signals to be delivered to the brain. A complex vascular structure ensures an adequate supply of blood and oxygen, which is essential for the function and survival of the retinal tissue. To date, a complete understanding of the configuration of the retinal vascular structures is still lacking. Optical coherence tomography angiography has made available a huge amount of imaging data regarding the main retinal capillary plexuses, namely the superficial capillary plexuses (SCP), intermediate capillary plexuses (ICP) and deep capillary plexuses (DCP). However, the interpretation of these data is still controversial. In particular, the question of whether the three capillary plexuses are connected in series or in parallel remains a matter of debate. In this work, we address this question by utilizing a multi-scale/multi-physics mathematical model to quantify the impact of the two hypothesized vascular configurations on retinal hemodynamics and oxygenation. The response to central retinal vein occlusion (CRVO) and intraocular pressure (IOP) elevation is also simulated depending on whether the capillary plexuses are connected in series or in parallel. The simulation results show the following: (i) in the in series configuration, the plexuses exhibit a differential response, with DCP and ICP experiencing larger pressure drops than SCP; and (ii) in the in parallel configuration, the blood flow redistributes uniformly in the three plexuses. The different vascular configurations show different responses also in terms of oxygen profiles: (i) in the in series configuration, the outer nuclear layer, outer plexiform layer and inner nuclear layer (INL) are those most affected by CRVO and IOP elevation; and (ii) in the in parallel configuration the INL and ganglion cell layer are those most affected. The in series results are consistent with studies on paracentral acute middle maculopathy, secondary to CRVO and with studies on IOP elevation, in which DCP and ICP and the retinal tissues surrounding them are those most affected by ischemia. These findings seem to suggest that the in series configuration better describes the physiology of the vascular retinal capillary network in health and disease.

Blood Vessels: The Pathway Used by Schwann Cells to Colonize Nerve Conduits

The repair of severe nerve injuries requires an autograft or conduit to bridge the gap and avoid axon dispersion. Several conduits are used routinely, but their effectiveness is comparable to that of an autograft only for short gaps. Understanding nerve regeneration within short conduits could help improve their efficacy for longer gaps. Since Schwann cells are known to migrate on endothelial cells to colonize the “nerve bridge”, the new tissue spontaneously forming to connect the injured nerve stumps, here we aimed to investigate whether this migratory mechanism drives Schwann cells to also proceed within the nerve conduits used to repair large nerve gaps. Injured median nerves of adult female rats were repaired with 10 mm chitosan conduits and the regenerated nerves within conduits were analyzed at different time points using confocal imaging of sequential thick sections. Our data showed that the endothelial cells formed a dense capillary network used by Schwann cells to migrate from the two nerve stumps into the conduit. We concluded that angiogenesis played a key role in the nerve conduits, not only by supporting cell survival but also by providing a pathway for the migration of newly formed Schwann cells.

Intracameral Microimaging of Maturation of Human iPSC Derivatives into Islet Endocrine Cells

We exploited the anterior chamber of the eye (ACE) of immunodeficient mice as an ectopic site for both transplantation and microimaging of engineered surrogate islets from human induced pluripotent stem cells (hiPSC-SIs). These islets contained a majority of insulin-expressing cells, positive or negative for PDX1 and NKX6.1, and a minority of glucagon- or somatostatin-positive cells. Single, non-aggregated hiPSC-SIs were satisfactorily engrafted onto the iris. They underwent gradual vascularization and progressively increased their light scattering signals, reflecting the abundance of zinc-insulin crystal packaged inside mature insulin secretory granules. Intracameral hiPSC-SIs retrieved from recipients showed enhanced insulin immunofluorescence in correlation with the parallel increase in overall vascularization and light backscattering during the post-transplantation period. This approach enables longitudinal, nondestructive and intravital microimaging of cell fates, engraftment, vascularization and mature insulin secretory granules of single hiPSC-SI grafts, and may offer a feasible and reliable means to screen compounds for promoting in vivo hiPSC-SI maturation.

Left Ventricular Wall Reconstruction with Autologous Vascularized Gastric Graft in a Porcine Pilot Model

INTRODUCTION

Surgical replacement of dysfunctional cardiac muscle with regenerative tissue is an important option to combat heart failure. But current available myocardial prostheses like a Dacron or a pericardium patch neither have a regenerative capacity nor do they actively contribute to the heart`s pump function. This study aimed to show the feasibility of utilizing a vascularized stomach patch for transmural left ventricular wall reconstruction.

METHODS

A left ventricular transmural myocardial defect was reconstructed by performing transdiaphragmatic autologous transplantation of a vascularized stomach segment in six Lewe minipigs. Three further animals received a conventional Dacron patch as a control treatment. The first three animals were followed up for 3 months until planned euthanasia, whereas the observation period for the remaining three animals was scheduled 6 months following surgery. Functional assessment of the grafts was carried out via cardiac magnetic resonance tomography (MRI) and angiography. Physiological remodeling was evaluated histologically and immunohistochemically after heart explanation.

RESULTS

Five out of six test animals and all control animals survived the complex surgery and completed the follow-up without clinical complications. One animal died intraoperatively due to excessive bleeding. No animal experienced a rupture of the stomach graft. Functional integration of the heterotopically transplanted stomach into the surrounding myocardium was observed. Angiography showed the development of connections between the gastric graft vasculature and the coronary system of the host cardiac tissue.

CONCLUSIONS

The clinical results and the observed physiological integration of gastric grafts into the cardiac structure demonstrate the feasibility of vascularized stomach tissue as a myocardial prosthesis. The physiological remodeling indicates a regenerative potential of the graft. Above all, the connection of the gastric vessels with the coronary system constitutes a rationale for the use of vascularized and therefore viable stomach tissue for versatile tissue engineering applications.

Peptide-Modified Nano-Bioactive Glass for Targeted Immobilization of Native VEGF

A limiting factor in large bone defect regeneration is the slow and disorganized formation of a functional vascular network in the defect area, often resulting in delayed healing or implant failure. To overcome this, strategies that induce angiogenic processes should be combined with potent bone graft substitutes in new bone regeneration approaches. To this end, we describe a unique approach to immobilize the pro-angiogenic growth factor VEGF₁₆₅ in its native state on the surface of nanosized bioactive glass particles (nBGs) via a binding peptide (PR1P). We demonstrate that covalent coupling of the peptide to amine functional groups grafted on the nBG surface allows immobilization of VEGF with high efficiency and specificity. The amount of coupled peptide could be controlled by varying amine density, which eventually allows tailoring the amount of bound VEGF within a physiologically effective range. In vitro analysis of endothelial cell tube formation in response to VEGF-carrying nBG confirmed that the biological activity of VEGF is not compromised by the immobilization. Instead, comparable angiogenic stimulation was found for lower doses of immobilized VEGF compared to exogenously added VEGF. The described system, for the first time, employs a binding peptide for growth factor immobilization on bioactive glass nanoparticles and represents a promising strategy to overcome the problem of insufficient neovascularization in large bone defect regeneration.

Engineered Customizable Microvessels for Progressive Vascularization in Large Regenerative Implants

Inspired by the rapid angiogenesis of natural microvessels in vivo, engineered customizable microvessels (ECMVs) are developed which can naturally angiogenic sprout and induce vascular network formation via combing a celluar coaxial microfluidic extrusion technique with microsurgery post-process. ECMVs can be used for customization of primarily pre-vascularized soft tissue regenerative implants with personalized shape and vascular density with the aid of sacrificial printing technology. After collaborating with surrounding cells, ECMVs angiogenic sprouted and formed daughter vascular networks. Through techniques such as injection and suturing, ECMVs can also be introduced into large bone repair implants for pre-vascularization and osteogenesis promotion. Furthermore, the microvessel networks with personalized shapes are customized by connecting the coaxial microfluidic system to a 3D printer. It is further demonstrated that the vascularization promotion and anastomose with host vessels of the ECMVs in vivo. Thus, ECMVs provide a simple engineering strategy for rapid vascularization of clinically large regenerative soft/hard tissue implants.

Biomimetic Trachea Engineering via a Modular Ring Strategy Based on Bone-Marrow Stem Cells and Atelocollagen for Use in Extensive Tracheal Reconstruction

The fabrication of biomimetic tracheas with a architecture of cartilaginous rings alternately interspersed between vascularized fibrous tissue (CRVFT) has the potential to perfectly recapitulate the normal tracheal structure and function. Herein, the development of a customized chondroitin-sulfate-incorporating type-II atelocollagen (COL II/CS) scaffold with excellent chondrogenic capacity and a type-I atelocollagen (COL I) scaffold to facilitate the formation of vascularized fibrous tissue is described. An efficient modular ring strategy is then adopted to develop a CRVFT-based biomimetic trachea. The in vitro engineering of cartilaginous rings is achieved via the recellularization of ring-shaped COL II/CS scaffolds using bone marrow stem cells as a mimetic for native cartilaginous ring tissue. A CRVFT-based trachea with biomimetic mechanical properties, composed of bionic biochemical components, is additionally successfully generated in vivo via the alternating stacking of cartilaginous rings and ring-shaped COL I scaffolds on a silicone pipe. The resultant biomimetic trachea with pedicled muscular flaps is used for extensive tracheal reconstruction and exhibits satisfactory therapeutic outcomes with structural and functional properties similar to those of native trachea. This is the first study to utilize stem cells for long-segmental tracheal cartilaginous regeneration and this represents a promising method for extensive tracheal reconstruction.

雪旺细胞调控骨组织再生的研究进展

OBJECTIVE

To review the research progress on the role of Schwann cells in regulating bone regeneration.

METHODS

The domestic and foreign literature about the behavior of Schwann cells related to bone regeneration, multiple tissue repair ability, nutritional effects of their neurotrophic factor network, and their application in bone tissue engineering was extensively reviewed.

RESULTS

As a critical part of the peripheral nervous system, Schwann cells regulate the expression level of various neurotrophic factors and growth factors through the paracrine effect, and participates in the tissue regeneration and differentiation process of non-neural tissues such as blood vessels and bone, reflecting the nutritional effect of neural-vascular-bone integration.

CONCLUSION

Taking full advantage of the multipotent differentiation ability of Schwann cells in nerve, blood vessel, and bone tissue regeneration may provide novel insights for clinical application of tissue engineered bone.

Strategies for extremity reconstruction with exposed bones and tendons using acellular dermal matrices: concept of sequential vascularization

We report 3 cases of patients treated with Bilayer Wound Matrix over exposed structures. In all patients, dermal matrices revascularization occurred sequentially over the course of 6–12 weeks, leading to successful wound closure. Acellular dermal matrices allow more difficult areas with poor vascularity to be covered from the ‘inside-out’.

Vascular and hormonal interactions in the adrenal gland

Primary aldosteronism is the most common form of secondary arterial hypertension, due to excessive aldosterone production from the adrenal gland. Although somatic mutations have been identified in aldosterone producing adenoma, the exact mechanisms leading to increased cell proliferation and nodule formation remain to be established. One hypothesis is that changes in vascular supply to the adrenal cortex, due to phenomena of atherosclerosis or high blood pressure, may influence the morphology of the adrenal cortex, resulting in a compensatory growth and nodule formation in response to local hypoxia. In this review, we will summarize our knowledge on the mechanisms regulating adrenal cortex development and function, describe adrenal vascularization in normal and pathological conditions and address the mechanisms allowing the cross-talk between the hormonal and vascular components to allow the extreme tissue plasticity of the adrenal cortex in response to endogenous and exogenous stimuli. We will then address recent evidence suggesting a role for alterations in the vascular compartment that could eventually be involved in nodule formation and the development of primary aldosteronism.

Development and Characterization of Gelatin-Norbornene Bioink to Understand the Interplay between Physical Architecture and Micro-Capillary Formation in Biofabricated Vascularized Constructs

The principle challenge for engineering viable, cell-laden hydrogel constructs of clinically-relevant size, is rapid vascularization, in order to moderate the finite capacity of passive nutrient diffusion. A multiscale vascular approach, with large open channels and bulk microcapillaries may be an admissible approach to accelerate this process, promoting overall pre-vascularization for long-term viability of constructs. However, the limited availability of bioinks that possess suitable characteristics that support both fabrication of complex architectures and formation of microcapillaries, remains a barrier to advancement in this space. In this study, gelatin-norbornene (Gel-NOR) is investigated as a vascular bioink with tailorable physico-mechanical properties, which promoted the self-assembly of human stromal and endothelial cells into microcapillaries, as well as being compatible with extrusion and lithography-based biofabrication modalities. Gel-NOR constructs containing self-assembled microcapillaries are successfully biofabricated with varying physical architecture (fiber diameter, spacing, and orientation). Both channel sizes and cell types affect the overall structural changes of the printed constructs, where cross-signaling between both human stromal and endothelial cells may be responsible for the reduction in open channel lumen observed over time. Overall, this work highlights an exciting three-way interplay between bioink formulation, construct design, and cell-mediated response that can be exploited towards engineering vascular tissues.

Improved Vascularization and Survival of White Compared to Brown Adipose Tissue Grafts in the Dorsal Skinfold Chamber

Fat grafting is a frequently applied procedure in plastic surgery for volume reconstruction. Moreover, the transplantation of white adipose tissue (WAT) and brown adipose tissue (BAT) increasingly gains interest in preclinical research for the treatment of obesity-related metabolic defects. Therefore, we herein directly compared the vascularization capacity and survival of WAT and BAT grafts. For this purpose, size-matched grafts isolated from the inguinal WAT pad and the interscapular BAT depot of C57BL/6N donor mice were syngeneically transplanted into the dorsal skinfold chamber of recipient animals. The vascularization and survival of the grafts were analyzed by means of intravital fluorescence microscopy, histology, and immunohistochemistry over an observation period of 14 days. WAT grafts showed an identical microvascular architecture and functional microvessel density as native WAT. In contrast, BAT grafts developed an erratic microvasculature with a significantly lower functional microvessel density when compared to native BAT. Accordingly, they also contained a markedly lower number of CD31-positive microvessels, which was associated with a massive loss of perilipin-positive adipocytes. These findings indicate that in contrast to WAT grafts, BAT grafts exhibit an impaired vascularization capacity and survival, which may be due to their higher metabolic demand. Hence, future studies should focus on the establishment of strategies to improve the engraftment of transplanted BAT.

Progress and challenges in preclinical stroke recovery research

Significant innovations in the management of acute ischemic stroke have led to an increased incidence in the long-term complications of stroke. Therefore, there is an urgent need for improvements in and refinement of rehabilitation interventions that can lead to functional and neuropsychological recovery. The goal of this review is to summarize the current progress and challenges involved with preclinical stroke recovery research. Moving forward, stroke recovery research should be placing an increased emphasis on the incorporation of comorbid diseases and biological variables in preclinical models in order to overcome translational roadblocks to establishing successful clinical rehabilitation interventions.