Vascularization Of Scaffolds Research Articles

Bioactive polymer composite scaffolds fabricated from 3D printed negative molds enable bone formation and vascularization

Scaffolds for bone defect treatment should ideally support vascularization and promote bone formation, to facilitate the translation into biomedical device applications. This study presents a novel approach utilizing 3D-printed water-dissolvable polyvinyl alcohol (PVA) sacrificial molds to engineer polymerized High Internal Phase Emulsion (polyHIPE) scaffolds with microchannels and distinct multiscale porosity. Two sacrificial mold variants (250 µm and 500 µm) were generated using fused deposition modeling, filled with HIPE, and subsequently dissolved to create polyHIPE scaffolds containing microchannels. In vitro assessments demonstrated significant enhancement in cell infiltration, proliferation, and osteogenic differentiation, underscoring the favorable impact of microchannels on cell behavior. High loading efficiency and controlled release of the osteogenic factor BMP-2 were achieved, with microchannels facilitating release of the growth factor. Evaluation in a mouse critical-size calvarial defect model revealed enhanced vascularization and bone formation in microchanneled scaffolds containing BMP-2. This study not only introduces an accessible method for creating multiscale porosity in polyHIPE scaffolds but also emphasizes its capability to enhance cellular infiltration, controlled growth factor release, and in vivo performance. The findings suggest promising applications in bone tissue engineering and regenerative medicine, and are expected to facilitate the translation of this type of biomaterial scaffold. Statement of significanceThis study holds significance in the realm of biomaterial scaffold design for bone tissue engineering and regeneration. We demonstrate a novel method to introduce controlled multiscale porosity and microchannels into polyHIPE scaffolds, by utilizing 3D-printed water-dissolvable PVA molds. The strategy offers new possibilities for improving cellular infiltration, achieving controlled release of growth factors, and enhancing vascularization and bone formation outcomes. This microchannel approach not only marks a substantial stride in scaffold design but also demonstrates its tangible impact on enhancing osteogenic cell differentiation and fostering robust bone formation in vivo. The findings emphasize the potential of this methodology for bone regeneration applications, showcasing an interesting advancement in the quest for effective and innovative biomaterial scaffolds to regenerate bone defects.

Enhanced vascularity in gelatin scaffolds via copper-doped magnesium–calcium silicates incorporation: In-vitro and ex-ovo insights

Addressing a critical challenge in current tissue-engineering practices, this study aims to enhance vascularization in 3D porous scaffolds by incorporating bioceramics laden with pro-angiogenic ions. Specifically, freeze-dried gelatin-based scaffolds were infused with sol-gel-derived powders of Cu-doped akermanite (Ca2MgSi2O7) and bredigite (Ca7MgSi4O16) at various concentrations (10, 20, and 30 wt%). The scaffolds were initially characterized for their structural integrity, biodegradability, swelling behavior, impact on physiological pH, and cytocompatibility with human umbilical vein endothelial cells (HUVECs). The silicate incorporation effectiveness in promoting vascularity was then assessed through HUVEC attachment, capillary tube formation, and ex-ovo chick embryo chorioallantoic membrane assays. The findings revealed significant improvements in both in-vitro and ex-ovo vascularity of the gelatin scaffolds upon the addition of Cu-doped akermanite. The most effective concentrations were determined to be 10 and 20 %, which led to notable HUVEC metabolic activity, a well-spread morphology with extensive peripheral filopodia and lamellipodia at 10 % and a cobblestone phenotype indicative of in-vivo endothelium at 20 % during cell attachment, the formation of complex networks of tubular structures, and robust vascularization in chick embryo development. Moving forward, the incorporation of Cu-doped akermanite into tissue-engineering scaffolds shows great potential for addressing the limitations of vascularization, especially for critical-sized bone defects, by facilitating the controlled release of pro-angiogenic and pro-osteogenic ions.

<i>In vivo</i> application of prevascularized bone scaffolds: A literature review

BACKGROUND: Despite expanding research, the development of materials for replacing bone defects remains an urgent problem in orthopedics and traumatology. Thus, one of the most important tasks is to create conditions for proper trophicity of the bone implant.
 AIM: To analyze modern approaches to bone scaffold vascularization and evaluate their adequacy in in vivo models.
 MATERIALS AND METHODS: The article presents a literature review dedicated to the methods of vascularization of bone scaffolds. A literature search was performed in PubMed, ScienceDirect, eLibrary, and Google Scholar databases from 2013 to 2023 using keywords, and 271 sources were identified. After exclusion, 95 articles were analyzed, and the results of 38 original studies and one literature review were presented.
 RESULTS: Regardless of the initial vascularization method of scaffolds, bone implants show distinct osteoinductive features and promote advanced bone tissue regeneration. Constructs based on solid polymers and calcium–phosphate compositions also perform osteoconductive functions. Mesenchymal stem cells are used as the main cell type, as well as vessel-type cells, which in cooperation also have a positive effect on bone-defect remodeling. Bone morphogenetic proteins are used for directed differentiation in the osteogenic direction, and vascular endothelial growth factor is used for differentiation in the vascular pathway.
 CONCLUSIONS: At present, no method for vascularization of scaffolds has been approved universally. In addition, no evidence supported the comparative effectiveness of vascularization methods, whereas animal model studies have demonstrated a positive effect of prevascularized patterns on the recovery rate of minor and critical defects.

Enhancing osteogenesis and angiogenesis functions for Ti-24Nb-4Zr-8Sn scaffolds with methacrylated gelatin and deferoxamine.

Repair of large bone defects remains challenge for orthopedic clinical treatment. Porous titanium alloys have been widely fabricated by the additive manufacturing, which possess the elastic modulus close to that of human cortical bone, good osteoconductivity and osteointegration. However, insufficient bone regeneration and vascularization inside the porous titanium scaffolds severely limit their capability for repair of large-size bone defects. Therefore, it is crucially important to improve the osteogenic function and vascularization of the titanium scaffolds. Herein, methacrylated gelatin (GelMA) were incorporated with the porous Ti-24Nb-4Zr-8Sn (Ti2448) scaffolds prepared by the electron beam melting (EBM) method (Ti2448-GelMA). Besides, the deferoxamine (DFO) as an angiogenic agent was doped into the Ti2448-GelMA scaffold (Ti2448-GelMA/DFO), in order to promote vascularization. The results indicate that GelMA can fully infiltrate into the pores of Ti2448 scaffolds with porous cross-linked network (average pore size: 120.2 ± 25.1μm). Ti2448-GelMA scaffolds facilitated the differentiation of MC3T3-E1 cells by promoting the ALP expression and mineralization, with the amount of calcium contents ∼2.5 times at day 14, compared with the Ti2448 scaffolds. Impressively, the number of vascular meshes for the Ti2448-GelMA/DFO group (∼7.2/mm2) was significantly higher than the control group (∼5.3/mm2) after cultivation for 9h, demonstrating the excellent angiogenesis ability. The Ti2448-GelMA/DFO scaffolds also exhibited sustained release of DFO, with a cumulative release of 82.3% after 28 days. Therefore, Ti2448-GelMA/DFO scaffolds likely provide a new strategy to improve the osteogenesis and angiogenesis for repair of large bone defects.

From Free Tissue Transfer to Hydrogels: A Brief Review of the Application of the Periosteum in Bone Regeneration.

The periosteum is a thin layer of connective tissue covering bone. It is an essential component for bone development and fracture healing. There has been considerable research exploring the application of the periosteum in bone regeneration since the 19th century. An increasing number of studies are focusing on periosteal progenitor cells found within the periosteum and the use of hydrogels as scaffold materials for periosteum engineering and guided bone development. Here, we provide an overview of the research investigating the use of the periosteum for bone repair, with consideration given to the anatomy and function of the periosteum, the importance of the cambium layer, the culture of periosteal progenitor cells, periosteum-induced ossification, periosteal perfusion, periosteum engineering, scaffold vascularization, and hydrogel-based synthetic periostea.

Effect of adipose-derived stem cells seeding and surgical prefabrication on composite scaffold vascularization.

The study aimed to evaluate an angiogenic effect of adipose-derived stem cells (ASCs) seeding and surgical prefabrication (placing a vascular pedicle inside the scaffold) on developed composite scaffolds made of poly-ε-caprolactone (PCL), β-tricalcium phosphate (β-TCP), and poly (lactic-co-glycolic acid) (PLGA) (PCL+β-TCP+PLGA). Moreover, we aimed to compare our data with previously tested PCL scaffolds to assess whether the new material has better angiogenic properties. The study included 18 inbred male WAG rats. There were three scaffold groups (six animals each): with non-seeded PCL+β-TCP+PLGA scaffolds, with PCL+β-TCP+PLGA scaffolds seeded with ASCs and with PCL+β-TCP+PLGA scaffolds seeded with ASCs and osteogenic-induced. Each rat was implanted with two scaffolds in the inguinal region (one prefabricated and one non-prefabricated). After 2months from implantation, the scaffolds were explanted, and vessel density was determined by histopathological examination. Prefabricated ASC-seeded PCL+β-TCP+PLGA scaffolds promoted greater vessel formation than non-seeded scaffolds (19.73 ± 5.46 vs 12.54 ± 0.81; p = .006) and those seeded with osteogenic-induced ASCs (19.73 ± 5.46 vs 11.87±2.21; p = .004). The developed composite scaffold promotes vessel formation more effectively than the previously described PCL scaffold.

Microporous Hydroxyapatite-Based Ceramics Alter the Physiology of Endothelial Cells through Physical and Chemical Cues.

Incorporation of silicate ions in calcium phosphate ceramics (CPC) and modification of their multiscale architecture are two strategies for improving the vascularization of scaffolds for bone regenerative medicine. The response of endothelial cells, actors for vascularization, to the chemical and physical cues of biomaterial surfaces is little documented, although essential. We aimed to characterize in vitro the response of an endothelial cell line, C166, cultivated on the surface CPCs varying either in terms of their chemistry (pure versus silicon-doped HA) or their microstructure (dense versus microporous). Adhesion, metabolic activity, and proliferation were significantly altered on microporous ceramics, but the secretion of the pro-angiogenic VEGF-A increased from 262 to 386 pg/mL on porous compared to dense silicon-doped HA ceramics after 168 h. A tubulogenesis assay was set up directly on the ceramics. Two configurations were designed for discriminating the influence of the chemistry from that of the surface physical properties. The formation of tubule-like structures was qualitatively more frequent on dense ceramics. Microporous ceramics induced calcium depletion in the culture medium (from 2 down to 0.5 mmol/L), which is deleterious for C166. Importantly, this effect might be associated with the in vitro static cell culture. No influence of silicon doping of HA on C166 behavior was detected.

Microtube embedded hydrogel bioprinting for vascularization of tissue-engineered scaffolds.

Vascular tissue engineering has been considered promising as one of the alternatives for viable artificial tissues and organs. Macro- and microscale hollow tubes fabricated with various techniques have been widely studied to mimic blood vessels. To date, the fabrication of biomimetic capillary vessels with sizes ranging from 1 to 10 µm is still challenging. In this paper, core-sheath microtubes were electrospun to mimic capillary vessels and were embedded in carboxymethyl cellulose/sodium alginate hydrogel for bioprinting. The results showed improved printing fidelity and promoted cell attachment. The tube concentration and tube length both had significant influences on filament size and merging area. Printed groups with higher microtube concentration showed higher microtube density, with filament/nozzle size ratio, and printed/designed grid area ratio closer to 100%. In the in vitro experiments, microtubes were not only compatible with human umbilical vein endothelial cells but also provided microtopographical cues to promote cell proliferation and morphogenesis in three-dimensional space. In summary, the microtubes fabricated by our groups have the potential for the bioprinting of vascularized soft tissue scaffolds.

Biomimetic hydrogel scaffolds embedded with porous microtubes as perfusion channels

Despite the remarkable progress in biofabrication, the vascularization of large-sized tissue scaffolds remains a great challenge for tissue engineering. The lack of effective capillary vessels in the scaffold can result in cellular necrosis due to the lack of oxygen and nutrients. Integrating capillary vessels in scaffolds is critical to maintaining cellular metabolic functions and the ultimate success of engineering large-scale tissues and organs. This paper demonstrates a novel hybrid biofabrication method that combines coaxial electrospinning and extrusion-based bioprinting to fabricate microtube-embedded hydrogel scaffolds. The porous microtubes mimicked the capillary morphology and were embedded between layers of 3D printed sodium alginate scaffold to function as a microchannel diffusion system. The dye diffusion test showed that the microtubes enhanced the mass transport within the scaffold.

Angiogenic and immunomodulation role of ions for initial stages of bone tissue regeneration.

It is widely known that bone has intrinsic capacity to self-regenerate after injury. However, the physiological regeneration process can be impaired when there is an extensive damage. One of the main reasons is due to the inability to establish a new vascular network that ensures oxygen and nutrient diffusion, leading to a necrotic core and non-junction of bone. Initially, bone tissue engineering (BTE) emerged to use inert biomaterials to just fill bone defects, but it eventually evolved to mimic bone extracellular matrix and even stimulate bone physiological regeneration process. In this regard, the stimulation of osteogenesis has gained a lot of attention especially in the proper stimulation of angiogenesis, being critical to achieve a successful osteogenesis for bone regeneration. Besides, the immunomodulation of a pro-inflammatory environment towards an anti-inflammatory one upon scaffold implantation has been considered another key process for a proper tissue restoration. To stimulate these phases, growth factors and cytokines have been extensively used. Nonetheless, they present some drawbacks such as low stability and safety concerns. Alternatively, the use of inorganic ions has attracted higher attention due to their higher stability and therapeutic effects with low side effects. This review will first focus in giving fundamental aspects of initial bone regeneration phases, focusing mainly on inflammatory and angiogenic ones. Then, it will describe the role of different inorganic ions in modulating the immune response upon biomaterial implantation towards a restorative environment and their ability to stimulate angiogenic response for a proper scaffold vascularization and successful bone tissue restoration. STATEMENT OF SIGNIFICANCE: The impairment of bone tissue regeneration when there is excessive damage has led to different tissue engineered strategies to promote bone healing. Significant importance has been given in the immunomodulation towards an anti-inflammatory environment together with proper angiogenesis stimulation in order to achieve successful bone regeneration rather than stimulating only the osteogenic differentiation. Ions have been considered potential candidates to stimulate these events due to their high stability and therapeutic effects with low side effects compared to growth factors. However, up to now, no review has been published assembling all this information together, describing individual effects of ions on immunomodulation and angiogenic stimulation, as well as their multifunctionality or synergistic effects when combined together.

129. Micropuncture Vascularization of Intraoperative Bioprinted Scaffolds

129. Micropuncture Vascularization of Intraoperative Bioprinted Scaffolds

PC34. Micropuncture Induced Scaffold Vascularization and Macrophage Quantification Across Vascular Origins

PURPOSE: Vascularization is a major barrier to tissue engineering and macrophages are believed to be integral. We have developed a microsurgical approach which rapidly vascularizes an adjacent scaffold. In micropuncture (MP), the recipient blood vessel wall is precisely disrupted providing an immediate route for cell extravasation. Here, we evaluated scaffold vascularization and macrophage infiltration across vascular origins. We hypothesized that concurrent artery/vein MP results in greatest macrophage infiltration and vascularization. METHODS: MP was tested in the rat femoral artery (MPA), vein (MPV), artery and vein (MPA/V), and no MP (control). MPs were created just prior to scaffold implantation. At post-operative day (POD) 3 and 10, samples were analyzed using whole mount angiography and histology. Vascular density was computed using artificial intelligence. Endothelial cell (EC) and macrophage infiltration were quantified. RESULTS: Vascular density appeared concordant with EC infiltration with MPA/V resulting in the greatest increase. Maximum macrophage infiltration was noted in MPV at both timepoints followed by MPA/V. Both conditions hastened macrophage accumulation when compared to MPA and the control. CONCLUSION: Micropuncture creates a localized pro-angiogenic environment. Although MPA/V led to greatest vascularization, it is noteworthy that MPV is also substantially pro-angiogenic. This suggests that the vein primarily drives cellular and vascular changes. MP appears to offer a tailored microsurgical approach for angiogenic induction which may prove beneficial to reconstructive surgery and tissue engineering.

3D-printed vascularized biofunctional scaffold for bone regeneration.

3D-printed biofunctional scaffolds have promising applications in bone tissue regeneration. However, the development of bioinks with rapid internal vascularization capabilities and relatively sustained osteoinductive bioactivity is the primary technical challenge. In this work, we added rat platelet-rich plasma (PRP) to a methacrylated gelatin (GelMA)/methacrylated alginate (AlgMA) system, which was further modified by a nanoclay, laponite (Lap). We found that Lap was effective in retarding the release of multiple growth factors from the PRP-GelMA/AlgMA (PRP-GA) hydrogel and sustained the release for up to 2 weeks. Our in vitro studies showed that the PRP-GA@Lap hydrogel significantly promoted the proliferation, migration, and osteogenic differentiation of rat bone marrow mesenchymal stem cells, accelerated the formation of endothelial cell vascular patterns, and promoted macrophage M2 polarization. Furthermore, we printed hydrogel bioink with polycaprolactone (PCL) layer-by-layer to form active bone repair scaffolds and implanted them in subcutaneous and femoral condyle defects in rats. In vivo experiments showed that the PRP-GA@Lap/PCL scaffolds significantly promoted vascular inward growth and enhanced bone regeneration at the defect site. This work suggests that PRP-based 3D-bioprinted vascularized scaffolds will have great potential for clinical translation in the treatment of bone defects.

In vitro angiogenesis in response to biomaterial properties for bone tissue engineering: a review of the state of the art.

Bone tissue engineering (BTE) aims to improve the healing of bone fractures using scaffolds that mimic the native extracellular matrix. For successful bone regeneration, scaffolds should promote simultaneous bone tissue formation and blood vessel growth for nutrient and waste exchange. However, a significant challenge in regenerative medicine remains the development of grafts that can be vascularized successfully. Amongst other things, optimization of physicochemical conditions of scaffolds is key to achieving appropriate angiogenesis in the period immediately following implantation. Calcium phosphates and collagen scaffolds are two of the most widely studied biomaterials for BTE, due to their close resemblance to inorganic and organic components of bone, respectively, and their bioactivity, tunable biodegradability and the ability to produce tailored architectures. While various strategies exist to enhance vascularization of these scaffolds in vivo, further in vitro assessment is crucial to understand the relation between physicochemical properties of a biomaterial and its ability to induce angiogenesis. While mono-culture studies can provide evidence regarding cell-material interaction of a single cell type, a co-culture procedure is crucial for assessing the complex mechanisms involved in angiogenesis. A co-culture more closely resembles the natural tissue both physically and biologically by stimulating natural intercellular interactions and mimicking the organization of the in vivo environment. Nevertheless, a co-culture is a complex system requiring optimization of various parameters including cell types, cell ratio, culture medium and seeding logistics. Gaining fundamental knowledge of the mechanism behind the bioactivity of biomaterials and understanding the contribution of surface and architectural features to the vascularization of scaffolds, and the biological response in general, can provide an invaluable basis for future optimization studies. This review gives an overview of the available literature on scaffolds for BTE, and trends are extracted on the relationship between architectural features, biochemical properties, co-culture parameters and angiogenesis.

Effect of Co-culture of mesenchymal stem cell and glomerulus endothelial cell to promote endothelialization under optimized perfusion flow rate in whole renal ECM scaffold.

In recent era, many researches on implantable bio-artificial organs has been increased owing to large gap between donors and receivers. Comprehensive organ based researches on perfusion culture for cell injury using different flow rate have not been conducted at the cellular level. The present study investigated the co-culture of rat glomerulus endothelial cell (rGEC) and rat bone marrow mesenchymal stem cells (rBMSC) to develop micro vascularization in the kidney scaffolds culturing by bioreactor system. To obtain kidney scaffold, extracted rat kidneys were decellularized by 1% sodium dodecyl sulfate (SDS), 1% triton X-100, and distilled water. Expanded rGECs were injected through decellularized kidney scaffold artery and cultured using bioreactor system. Vascular endothelial cells adhered and proliferated on the renal ECM scaffold in the bioreactor system for 3, 7 and 14 days. Static, 1​ml/min and 2​ml/min flow rates (FR) were tested and among them, 1​ml/min flow rate was selected based on cell viability, glomerulus character, inflammation/endothelialization proteins expression level. However, the flow injury was still existed on primary cell cultured at vessel in kidney scaffold. Therefore, co-culture of rGEC​+​rBMSC found suitable to possibly solve this problem and resulted increased cell proliferation and micro-vascularization in the glomerulus, reducing inflammation and cell death which induced by flow injury. The optimized perfusion rate under rGEC​+​rBMSC co-culture conditions resulted in enhanced endocellularization to make ECM derived implantable renal scaffold and might be useful as a way of treatment of the acute renal failure.

Perimeter and carvacrol-loading regulate angiogenesis and biofilm growth in 3D printed PLA scaffolds.

Carvacrol is a natural low-cost compound derived from oregano which presents anti-bacterial properties against both Gram-positive and Gram-negative bacteria. In this work, carvacrol-loaded PLA scaffolds were fabricated by 3D printing as platforms to support bone tissue regeneration while preventing biofilm development. Scaffolds were printed with or without a perimeter (lateral wall) mimicking the cortical structure of bone tissue to further evaluate if the lateral interconnectivity could affect the biological or antimicrobial properties of the scaffolds. Carvacrol incorporation was performed by loading either the PLA filament prior to 3D printing or the already printed PLA scaffold. The loading method determined carvacrol localization in the scaffolds and its release profile. Biphasic profiles were recorded in all cases, but scaffolds loaded post-printed released carvacrol much faster, with 50-80% released in the first day, compared to those containing carvacrol in PLA filament before printing which sustained the release for several weeks. The presence or absence of the perimeter did not affect the release rate, but total amount released. Tissue integration and vascularization of carvacrol-loaded scaffolds were evaluated in a chorioallantoic membrane model (CAM) using a novel quantitative micro-computed tomography (micro-CT) analysis approach. The obtained results confirmed the CAM tissue ingrowth and new vessel formation within the porous structure of the scaffolds after 7days of incubation, without leading to hemorrhagic or cytotoxic effects. The absence of lateral wall facilitated lateral integration of the scaffolds in the host tissue, although increased the anisotropy of the mechanical properties. Scaffolds loaded with carvacrol post-printing showed antibiofilm activity against Staphylococcus aureus and Pseudomonas aeruginosa as observed in a decrease in CFU counting after biofilm detachment, changes in metabolic heat measured by calorimetry, and increased contact killing efficiency. In summary, this work demonstrated the feasibility of tuning carvacrol release rate and the amount released from PLA scaffolds to achieve antibiofilm protection without altering angiogenesis, which was mostly dependent on the perimeter density of the scaffolds.

Development of fibroblast/endothelial cell-seeded collagen scaffolds for in vitro prevascularization.

The development of vascularized scaffolds remains one of the major challenges in tissue engineering, and co-culturing with endothelial cells is known as one of the possible approaches for this purpose. In this approach, optimization of cell culture conditions, scaffolds, and fabrication techniques is needed to develop tissue equivalents that will enable in vitro formation of a capillary network. Prevascularized equivalents will be more physiologically comparable to the native tissues and potentially prevent insufficient vascularization after implantation. This study aimed to culture human umbilical vein endothelial cells (HUVECs), alone or in co-culture with fibroblasts, on collagen scaffolds prepared by simple fabrication approaches for in vitro prevascularization. Different concentrations and ratios of HUVECs and fibroblasts seeded on collagen gel and sponge scaffolds under several culture conditions were examined. Cell viability, scaffolds morphology, and structure were analyzed. Collagen gel scaffolds showed good cell proliferation and viability, with higher proliferation rates for cells cultured in a 2:1 (fibroblasts: HUVECs) ratio and kept in endothelial cell growth medium. However, these matrices were unable to support endothelial cell sprouting. Collagen sponges were highly porous and showed good cell viability. However, they became fragile over time in culture, and they still lack signs of vascularization. Collagen scaffolds were a good platform for cell growth and viability. However, under the experimental conditions of this study, the HUVEC/fibroblast-seeded scaffolds were not suitable platforms to generate in vitro prevascularized equivalents. Our findings will be a valuable starting point to optimize culture microenvironments and scaffolds during fabrication of prevascularized scaffolds.

A Medical-Grade Polycaprolactone and Tricalcium Phosphate Scaffold System With Corticoperiosteal Tissue Transfer for the Reconstruction of Acquired Calvarial Defects in Adults: Protocol for a Single-Arm Feasibility Trial.

BackgroundLarge skull defects present a reconstructive challenge. Conventional cranioplasty options include autologous bone grafts, vascularized bone, metals, synthetic ceramics, and polymers. Autologous options are affected by resorption and residual contour deformities. Synthetic materials may be customized via digital planning and 3D printing, but they all carry a risk of implant exposure, failure, and infection, which increases when the defect is large. These complications can be a threat to life. Without reconstruction, patients with cranial defects may experience headaches and stigmatization. The protection of the brain necessitates lifelong helmet use, which is also stigmatizing.ObjectiveOur clinical trial will formally study a hybridized technique's capacity to reconstruct large calvarial defects.MethodsA hybridized technique that draws on the benefits of autologous and synthetic materials has been developed by the research team. This involves wrapping a biodegradable, ultrastructured, 3D-printed scaffold made of medical-grade polycaprolactone and tricalcium phosphate in a vascularized, autotransplanted periosteum to exploit the capacity of vascularized periostea to regenerate bone. In vitro, the scaffold system supports cell attachment, migration, and proliferation with slow but sustained degradation to permit host tissue regeneration and the replacement of the scaffold. The in vivo compatibility of this scaffold system is robust—the base material has been used clinically as a resorbable suture material for decades. The importance of scaffold vascularization, which is inextricably linked to bone regeneration, is underappreciated. A variety of methods have been described to address this, including scaffold prelamination and axial vascularization via arteriovenous loops and autotransplanted flaps. However, none of these directly promote bone regeneration.ResultsWe expect to have results before the end of 2023. As of December 2020, we have enrolled 3 participants for the study.ConclusionsThe regenerative matching axial vascularization technique may be an alternative method of reconstruction for large calvarial defects. It involves performing a vascularized free tissue transfer and using a bioresorbable, 3D-printed scaffold to promote and support bone regeneration (termed the regenerative matching axial vascularization technique). This technique may be used to reconstruct skull bone defects that were previously thought to be unreconstructable, reduce the risk of implant-related complications, and achieve consistent outcomes in cranioplasty. This must now be tested in prospective clinical trials.Trial RegistrationAustralian New Zealand Clinical Trials Registry ACTRN12620001171909; https://tinyurl.com/4rakccb3International Registered Report Identifier (IRRID)DERR1-10.2196/36111

Engineering a Hierarchical Biphasic Gel for Subcutaneous Vascularization.

Implanted cell-containing grafts require a robust and functional vasculature to supply oxygen and nutrients, as well as clear metabolic waste products. However, it remains challenging to fabricate tunable, vascular-promoting scaffolds without incorporating additional biologics. Here, a biphasic gel consisting of a highly porous aerogel and a degradable fibrin hydrogel for inducing vascularization is presented. The highly porous (>90%) and stable aerogel is assembled from short microfibers by being dispersed in an aqueous solution that can be 3D printed into various configurations. The biphasic gel demonstrates good compression-resistance: 70.30% Young's modulus is recovered over 20 cycles of 65% compression under water. Furthermore, it is confirmed that tissue cells and blood vessels can penetrate a thick (≈3mm) biphasic gel in the subcutaneous space of mice. Finally, the biphasic gel doubles the vascular ingrowth compared to a composite of a commercial surgical polyester felt and a fibrin hydrogel upon subcutaneous implantation in mice after 4 weeks. The design of this biphasic gel may advance the development of vascularized scaffolds.

Biomimetic Surface Topography from the Rubus fruticosus Leaf as a Guidance of Angiogenesis in Tissue Engineering Applications.

The promotion of angiogenesis is a fundamental step for efficient organ/tissue reconstitution and replacement. Thus, several strategies to promote vascularization of scaffolds were studied to satisfy this unsolved clinical need. The interface between cells and substrates is a determinant for the success of tissue engineering (TE) strategies. Substrate's topography is reported to play a key role in influencing endothelial cell behavior, namely, on its proliferation, metabolic activity, morphology, migration, and secretion of cytokines and chemokines. Therefore, surface topography of the biomaterial-based grafts is a crucial property that is considered in the development of a new TE approach. Herein, we hypothesize that the surface of Rubus fruticosus leaf plays a crucial role in driving angiogenesis since its architecture resembles the vascular structures at a biologically relevant size scale. For this, we produced biomimetic polycaprolactone (PCL) membranes (BpMs) replicating the surface topography of a R. fruticosus leaf by replica molding and nanoimprint lithography. Our results showed an enhanced performance in terms of proliferation of the human endothelial cell line on top of the BpM. Moreover, an asymmetric cellular spatial distribution among the surface of the BpM was observed. These cells seem to have higher density for longer time periods in the region that replicates the leaf veins. Finally, we assess the angiogenic capacity through a chick chorioallantoic membrane assay, revealing that BpMs are more prone to support angiogenesis than flat PCL membranes. We strongly believe that this strategy can bring new insights into developing TE strategies with an enhanced performance in terms of the vascular integration between the host and the scaffolds implanted.