Capillary Formation Research Articles

Fibrin-Based Hydrogels with Reactive Amphiphilic Copolymers for Mechanical Adjustments Allow for Capillary Formation in 2D and 3D Environments.

This study focuses on enhancing controllable fibrin-based hydrogels for tissue engineering, addressing existing weaknesses. By integrating a novel copolymer, we improved the foundation for cell-based angiogenesis with adaptable structural features. Tissue engineering often faces challenges like waste disposal and nutrient supply beyond the 200 µm diffusion limit. Angiogenesis breaks through this limitation, allowing the construction of larger constructs. Our innovative scaffold combination significantly boosts angiogenesis, resulting in longer branches and more capillary network junctions. The copolymer attached to fibrin fibers enables precise adjustment of hydrogel mechanical dynamic properties for specific applications. Our material proves effective for angiogenesis, even under suppression factors like suramin. In our study, we prepared fibrin-based hydrogels with and without the copolymer PVP12400-co-GMA10mol%. Using a co-culture system of human umbilical vein endothelial cells (HUVEC) and mesenchymal stem cells (MSC), we analyzed angiogenetic behavior on and within the modified hydrogels. Capillary-like structures were reproducibly formed on different surfaces, demonstrating the general feasibility of three-dimensional endothelial cell networks in fibrin-based hydrogels. This highlights the biomaterial's suitability for in vitro pre-vascularization of biohybrid implants.

Ultralight anisotropic Ti3C2Tx MXene/Carbon nanotube hybrid aerogel for highly efficient solar steam generation

Solar steam generation (SSG) has been considered as a promising method to produce fresh water from seawater. Due to high light absorption and excellent chemical stability, carbon nanotube (CNT) has been widely used for SSG. However, it is still challenge to simultaneously realize high water evaporation rate and energy efficiency for CNT based solar steam generator. Herein, ultralight anisotropic Ti3C2Tx MXene/carbon nanotube (A-Ti3C2Tx/CNT) aerogels are designed and fabricated for highly efficient SSG. The combination of CNT and Ti3C2Tx MXene endows the hybrid aerogel with high light absorption and effective localized surface plasmon resonance (LSPR), resuting in enhanced light-to-heat conversion efficiency. The porous structure of aerogel leads to multiple scattering and absorption, further contributing to the photothermal conversion process. Moreover, the low thermal conductivity of aerogel structure effectively reduces the heat loss to environment. Through tailoring the anisotropic channel, the A-Ti3C2Tx/CNT hybrid aerogel with average channel size of 80 μm possesses most efficient water transport due to the capillary effect and formation of intermediate water. Therefore, the A-Ti3C2Tx/CNT hybrid aerogel exhibits high average light absorption of 95.68% in the wavelength range of 200–2500 nm, excellent water evaporation rate of 2.10 kg m−2 h−1 under 1 sun irradiation (1 kW m−2) with a high energy efficiency of 93.4%, and remarkable durability with 7 days continuous water evaporation. The A-Ti3C2Tx/CNT hybrid aerogel also shows high resistance to salt crystallization due to its high salt transport flux of 1.90 kg m−2 h−1. This work offers a prospective strategy for constructing highly efficient solar steam generator with stable performance for practical application in seawater desalination.

BAP31 Promotes Angiogenesis via Galectin-3 Upregulation in Neuroblastoma.

Neuroblastoma (NB) is one of the highly vascularized childhood solid tumors, and understanding the molecular mechanisms underlying angiogenesis in NB is crucial for developing effective therapeutic strategies. B-cell receptor-associated protein 31 (BAP31) has been implicated in tumor progression, but its role in angiogenesis remains unexplored. This study investigated BAP31 modulation of pro-angiogenic factors in SH-SY5Y NB cells. Through protein overexpression, knockdown, antibody blocking, and quantification experiments, we demonstrated that overexpression of BAP31 led to increased levels of vascular endothelial growth factor A (VEGFA) and Galectin-3 (GAL-3), which are known to promote angiogenesis. Conditioned medium derived from BAP31-overexpressing neuroblastoma cells stimulated migration and tube formation in endothelial cells, indicating its pro-angiogenic properties. Also, we demonstrated that BAP31 enhances capillary tube formation by regulating hypoxia-inducible factor 1 alpha (HIF-1α) and its downstream target, GAL-3. Furthermore, GAL-3 downstream proteins, Jagged 1 and VEGF receptor 2 (VEGFR2), were up-regulated, and blocking GAL-3 partially inhibited the BAP31-induced tube formation. These findings suggest that BAP31 promotes angiogenesis in NB by modulating GAL-3 and VEGF signaling, thereby shaping the tumor microenvironment. This study provides novel insights into the pro-angiogenic role of BAP31 in NB.

Prognostic correlation between specialized capillary endothelial cells and lung adenocarcinoma

BackgroundIn-depth analysis of the functional changes occurring in endothelial cells (ECs) involved in capillary formation can help to elucidate the mechanism of tumour vascular growth. MethodsAppropriate datasets were retrieved from the GEO database to obtain single-cell data on LUAD samples and adjacent normal tissue samples. ECs were selected by an automatic annotation program in R and further subdivided based on reported EC marker genes. Functional changes in different types of capillary ECs were then visualized, and the concrete expression was classified by genetic data in the TCGA. Finally, a prognostic model was constructed to predict immunoinfiltration status, survival and drug therapy effects. ResultsThe LUAD data contained in the GSE183219 dataset were suitable for our analysis. After dimensionality reduction analysis and cell annotation, EC general capillary and EC aerocyte subsets as capillary specialized phenotypes showed a series of functional changes in tumour samples, with a total of 108 genes found to undergo functional changes. Use of CellPhoneDB revealed a close interaction of activity between ECs. After integration of TCGA, GSE68465 and GSE11969 datasets, the genes obtained were analysed by cluster analysis and risk model construction, identifying 8 genes. Drug sensitivity, immune cell and molecular differences can be accurately predicted. ConclusionsEC general capillary and EC aerocyte subsets are recognized capillary ECs in the tumour microenvironment, and the functional changes between them are relevant to the prognosis and treatment of LUAD patients and have the potential to be used in target therapy.

Enhancement of Wound Healing and Angiogenesis Using Mouse Embryo Fibroblasts Loaded in Decellularized Skin Scaffold.

Synthetic and natural polymer scaffolds can be used to design wound dressing for repairing the damaged skin tissue. This study investigated acute wound healing process using a decellularized skin scaffold and mouse embryo fibroblast (MEF). Mouse skin fragments were decellularized and evaluated by DNA content, toxicity, H&E staining, Raman confocal microscopy, Masson’s trichrome staining, SEM, and biodegradation assays. The fragments were recellularized by the MEFs, and cell attachment and penetration were studied. De- and decellularized scaffolds were used wound dressings in mouse acute wound models as two experimental groups. Using morphological and immunohistochemical assessments, wound healing was evaluated and compared among the experimental and control groups. DNA content of the decellularized tissue significantly reduced compared to the native control group (7% vs. 100%; p < 0.05). extracellular matrix components, e.g. collagen types I, III, and IV, elastin, and glycosaminoglycan, were well preserved in the decellularized group. The porosity and fiber arrangement in the stroma had a structure similar to normal skin tissue. A significant reduction in healing time was observed in the group treated with a decellularized scaffold. A thicker epidermis layer was observed in the recovered tissue in both experimental groups compared to the control group. Immunostaining showed a positive reaction for CD31 as an endothelial marker in both experimental groups, confirming new vascularization in these groups. Using MEFs with decellularized skin as a wound dressing increases the rate of wound healing and also the formation of new capillaries. This system could be beneficial for clinical applications in the field of tissue engineering.

In Situ Synchrotron Investigations of Beam Diameter Influence on Vapor Capillary Formation during Laser Beam Welding of Copper Alloy with a Blue Laser Beam Source

Laser beam welding as a reliable tool for high-precision joining of batteries or microelectronics is more and more the choice for achieving reproducible results in production processes. In addition to a high automation capability, the precise control of the energy deposition into the material plays an important role, especially when highly reflective materials, such as copper or aluminum, must be welded together. Alongside the use of highly brilliant fiber lasers in the near-infrared range with a focal diameter of a few tens of micrometers, diode lasers in the wavelength range of 445 nm are increasingly being used. Here, beam diameters of a few hundred micrometers can be achieved. With a wavelength of 445 nm, the absorptivity in copper can be increased by more than a factor of 10 compared to a near-infrared laser beam sources in solid state at room temperature. This paper presents the in situ X-ray observation of laser welding processes on CuSn6 with a laser beam source with a wavelength of 445 nm using synchrotron radiation at DESY Petra III Beamline P07 EH4 in Hamburg, Germany. For the experiments, the laser radiation was focused via two separate optics to focal diameters of 362 µm and 609 µm. To characterize the dynamics of the vapor capillaries depending on the different focal diameters dF, the parameters were varied with respect to laser power PL and feed rate v. For the investigations, a synchrotron beam of 2 × 2 mm2 in size with a photon energy of 89 keV was used, and the material samples were analyzed by means of phase-contrast videography to show the boundaries between solid, liquid, and gaseous material phases. The results of this paper show the welding depths achieved and how the geometry of the vapor capillary behaves by changing the focal diameter, laser power and feed rate.

Effects of Gas Layer Thickness on Capillary Interactions at Superhydrophobic Surfaces.

Strongly attractive forces act between superhydrophobic surfaces across water due to the formation of a bridging gas capillary. Upon separation, the attraction can range up to tens of micrometers as the gas capillary grows, while gas molecules accumulate in the capillary. We argue that most of these molecules come from the pre-existing gaseous layer found at and within the superhydrophobic coating. In this study, we investigate how the capillary size and the resulting capillary forces are affected by the thickness of the gaseous layer. To this end, we prepared superhydrophobic coatings with different thicknesses by utilizing different numbers of coating cycles of a liquid flame spraying technique. Laser scanning confocal microscopy confirmed an increase in gas layer thickness with an increasing number of coating cycles. Force measurements between such coatings and a hydrophobic colloidal probe revealed attractive forces caused by bridging gas capillaries, and both the capillary size and the range of attraction increased with increasing thickness of the pre-existing gas layer. Hence, our data suggest that the amount of available gas at and in the superhydrophobic coating determines the force range and capillary growth.

3D-bioprinted hydrogels with instructive niches for dental pulp regeneration

Infections to dental pulp commonly result in pulpitis and pulp necrosis, and surgical removal of the infected tissues is the only therapeutic approach. Dental pulp injury remains a challenging medical issue due to the limited regenerative capability of dental pulp. In this work, a dental pulp guidance construct (DPGC) with the instructive niche was bioprinted to mimic native teeth for dentin and neovascular-like structure reconstruction. GelMA-Dextran aqueous emulsion was used as an ink for in situ printing of porous DPGC to induce predominant nuclear localization of Yes-associated protein (YAP) in the encapsulated dental pulp stem cells (DPSCs) and enhance their stemness properties. Furthermore, the DPSCs encapsulated in DPGC with microporous structures exhibited enhanced viability, migration, and spreading. Meanwhile, we found that DPGC could promote capillary tube formation and induce neurogenesis. In a mouse subcutaneous implant model, the DPGC consisted of porous structures, such as odontoblasts and newly formed vascular structures, that mimic dental pulp characteristics. This study demonstrated a new strategy to design DPGC with instructive niche for dental pulp regeneration, presenting a potential treatment alternative to root canal therapy.

Co-treatment with bone marrow-derived mesenchymal stem cells and curcumin improved angiogenesis in myocardium in a rat model of MI.

The cardioprotective properties of mesenchymal stem cells and the therapeutic potential of curcumin (CUR) have been explored. Combining these approaches may enhance stem cell effectiveness and expedite healing. This study aimed to investigate the synergistic effects of co-treating bone marrow mesenchymal stem cells (BMSCs) with curcumin on vascular endothelial growth factor (VEGF) levels, in a rat model of myocardial ischemia (MI). Sixty-five male rats were divided into four groups: G1 (healthy control), G2 (MI induced by isoproterenol hydrochloride), G3 (treated with BMSCs), and G4 (co-treated with curcumin and BMSCs). Blood and tissue samples were collected at specific time points (day 1, 7, 15 and 21) after MI induction. Serum levels of lactate dehydrogenase (LDH), creatine kinase (CK), cardiac troponin I (cTnI), aspartate aminotransferase (AST), CK-MB and VEGF were measured. VEGF mRNA and protein expression were evaluated using RT-qPCR and Western blot techniques. Histopathological assessments were performed using H&E staining and CD31 immunofluorescence staining. VEGF expression significantly increased on days 7 and 15 in the CUR-BMSCs group, peaking on day 7. Western blot analysis confirmed elevated VEGF protein expression on days 7 and 15 post-MI. ELISA results demonstrated increased serum VEGF levels on days 7 and 15, reaching the highest level on day 7 in CUR-BMSCs-treated animals. Treated groups showed lower levels of LDH, AST, CK, CK-MB and cTnI compared to the untreated MI group. H&E staining revealed improved myocardial structure, increased formation of new capillaries, in both treatment groups compared to the MI group. Combining curcumin with BMSCs promotes angiogenesis in the infarcted myocardium after 15days of MI induction. These findings suggest the potential of this combined therapy approach for enhancing cardiac healing and recovery.

Energizing the Lung Vasculature in the Premature Infant to Promote Alveolar Formation

Background/Objective: Chronic lung disease of prematurity, bronchopulmonary dysplasia (BPD) occurs when infants born with underdeveloped immature lungs are forced to navigate the expansion of future air spaces, with irregular vascular formation proceeding development of BPD. Lung development has distinct and dynamic metabolic requirements. We recently identified by mass spectrometry that nicotinamide adenine dinucleotide (NAD+), generated from vitamin B3 ‘Nicotinamide’ (NAM), was significantly reduced in a hyperoxia murine model of BPD. As NAM/NAD+ are dynamic regulators of tissue regenerating neovascularization in otherdisease processes, we hypothesized that NAM/NAD+ metabolic deficiencies contribute to compromised angiogenesis formation and alveolar formation.&#x0D; Methods: Impact of NAM supplementation on circulating human neonatal endothelial colonyforming cells (ECFCs) were assessed for differential capillary formation properties of angiogenesis (Matrigel), migration (wound healing), proliferation (WST1 and crystal violetstaining), and mitochondrial function in normoxia and hyperoxia (85% oxygen) conditions.&#x0D; Results: Hyperoxia suppresses ECFC angiogenesis, while NAM supplementation in hyperoxia significantly rescued vascular networks, branched nodes, and branch points (p&lt;0.001). Wound healing assays suggest that NAM promotes cell migration in normoxia and hyperoxia (p&lt;0.0001). Although NAM increased WST1 activity in hyperoxia, crystal violet analysis determined that NAM had no impact on ECFC proliferation. Lastly, NAM significantly reduced hyperoxia induced mitochondrial oxidative stress in a dose dependent manner (p&lt;0.05).&#x0D; Conclusion and Clinical Implications: Lung development has specific metabolic needs during different stages of development that are disrupted by premature birth. Replenishment of NAM promotes angiogenesis and migration in hyperoxia while reducing mitochondrial activity. Future studies are necessary to explore the role of NAM/NAD+ axis in the developing lung.

G protein subunit alpha i2's pivotal role in angiogenesis.

Here we explored the potential role of Gαi2 (G protein subunit alpha i2) in endothelial cell function and angiogenesis. Methods: Genetic methodologies such as shRNA, CRISPR/Cas9, dominant negative mutation, and overexpression were utilized to modify Gαi2 expression or regulate its function. Their effects on endothelial cell functions were assessed in vitro. In vivo, the endothelial-specific Gαi2 shRNA adeno-associated virus (AAV) was utilized to silence Gαi2 expression. The impact of this suppression on retinal angiogenesis in control mice and streptozotocin (STZ)-induced diabetic retinopathy (DR) mice was analyzed. Results: Analysis of single-cell RNA sequencing data revealed Gαi2 (GNAI2) was predominantly expressed in retinal endothelial cells and expression was increased in retinal endothelial cells following oxygen-induced retinopathy (OIR) in mice. Moreover, transcriptome analysis linking Gαi2 to angiogenesis-related processes/pathways, supported by increased Gαi2 expression in experimental OIR mouse retinas, highlighted its possible role in angiogenesis. In various endothelial cell types, shRNA-induced silencing and CRISPR/Cas9-mediated knockout (KO) of Gαi2 resulted in substantial reductions in cell proliferation, migration, invasion, and capillary tube formation. Conversely, Gαi2 over-expression in endothelial cells induced pro-angiogenic activities, enhancing cell proliferation, migration, invasion, and capillary tube formation. Furthermore, our investigation revealed a crucial role of Gαi2 in NFAT (nuclear factor of activated T cells) activation, as evidenced by the down-regulation of NFAT-luciferase reporter activity and pro-angiogenesis NFAT-targeted genes (Egr3, CXCR7, and RND1) in Gαi2-silenced or -KO HUVECs, which were up-regulated in Gαi2-overexpressing endothelial cells. Expression of a dominant negative Gαi2 mutation (S48C) also down-regulated NFAT-targeted genes, slowing proliferation, migration, invasion, and capillary tube formation in HUVECs. Importantly, in vivo experiments revealed that endothelial Gαi2 knockdown inhibited retinal angiogenesis in mice, with a concomitant down-regulation of NFAT-targeted genes in mouse retinal tissue. In contrast, Gαi2 over-expression in endothelial cells enhanced retinal angiogenesis in mice. Single-cell RNA sequencing data confirmed increased levels of Gαi2 specifically in retinal endothelial cells of mice with streptozotocin (STZ)-induced diabetic retinopathy (DR). Importantly, endothelial Gαi2 silencing ameliorated retinal pathological angiogenesis in DR mice. Conclusion: Our study highlights a critical role for Gαi2 in NFAT activation, endothelial cell activation and angiogenesis, offering valuable insights into potential therapeutic strategies for modulating these processes.

Fabrication and film-forming mechanism of PCTFE films with exceptional water-vapor barrier and mechanical properties via solvent-assisted method

Polychlorotrifluoroethylene (PCTFE) has the outstanding water-vapor barrier performances among thermoplastics, and is with excellent transparency, high cryogenic toughness, and ultralow dielectric constant/loss. It plays an important role in high-performance packaging, electric circuit constructions, anti-corrosion coatings, cryogenic sealing, and so forth. Nevertheless, due to its borderline thermal stability and sensitivity to shearing effect, the melt-processing of PCTFE is rather difficult. Herein, a solvent-assisted method, which contained fabrication, coating, drying, and sintering of PCTFE suspension, was proposed for the fabrication of PCTFE films. The influence of processing parameters, including particle shape, drying temperature, and sintering time on the film-forming process was investigated. The as-prepared PCTFE films exhibited exceptional mechanical properties, with a tensile strength and failure strain of ∼42 MPa and ∼108 %, respectively. The water vapor transmission rate, light transmittance, and haze reached ∼0.02 g/(m2·24 h), ∼91 %, and ∼3 %, respectively. Finally, the potential film-forming mechanism was explained by the densification of PCTFE particles via capillary force, neck formation and particles coalescence driven by surface tension and viscous flow, and co-crystallization across the initial particle interfaces. In summary, the solvent-assisted method opened a new pathway for the processing of PCTFE films and is conducive to broadening their application fields.

Decomposition Solution of a Mathematical Model for Capillary Formation

We compare the numerically calculated solution of a mathematical model for capillary formation in tumor angiogenesis with the one that is obtained by Adomian’s decompostion method. This methods requires no additional assumptions and linearization. Numerical comparison indicates that there is a close agreement between the two solutions.

Engineering a separation membrane containing a gel layer with backbone support effect and bionic-inspired capillary effect for the efficient separation of dyes/salts

Accurate separation of dyes/salts is a crucial step in the treatment of dye-containing wastewater. Therefore, separation membranes with high permeability and high dye/salt selectivity are urgently required. In this study, an ultrathin gel layer of carboxymethyl cellulose was constructed on a poly(vinylidene fluoride) membrane surface. This gel layer contains a backbone support structure and provides the bionic-inspired capillary effect, which endows the membrane with the capability to realize the efficient separation of dyes and salts. The introduction of silver nanoparticles (Ag NPs) into the gel layer provides a skeleton support structure, which prevents the collapse of the gel layer, reduces the actual separation layer thickness, and decreases the mass transfer resistance. Moreover, the formation of capillaries between the numerous Ag NPs facilitates the rapid penetration of water molecules. Interestingly, this membrane exhibited excellent selectivity for dye/salt separation (dye removal >99.5 %, salt removal <10 %) while maintaining an exceptionally high water permeate flux (244.5 L/m2h). Moreover, the membrane exhibited excellent stability. This study demonstrates that the construction of organic/inorganic three-dimensional structures with capillary and skeletal support effects show promise potential for modification of dye/salt separation membranes.

Jet from a very large, axisymmetric, surface-gravity wave

We demonstrate that gravity acting alone at large length scales (compared to the capillary length) can produce a jet from a sufficiently steep, axisymmetric surface deformation imposed on a quiescent, deep pool of liquid. Mechanistically, the jet owes it origin to the focusing of a concentric, surface wave towards the axis of symmetry, quite analogous to such focusing of capillary waves and resultant jet formation observed during bubble collapse at small scales. A weakly nonlinear theory based on the method of multiple scales in the potential flow limit is presented for a modal (single-mode) initial condition representing the solution to the primary Cauchy–Poisson problem. A pair of novel, coupled, amplitude equations are derived governing the modulation of the primary mode. For moderate values of the perturbation parameter $\epsilon$ (a measure of the initial perturbation steepness), our second-order theory captures the overshoot (incipient jet) at the axis of symmetry quite well, demonstrating good agreement with numerical simulation of the incompressible, Euler equation with gravity (Popinet 2014, Basilisk. http://basilisk.fr) and no surface tension. We demonstrate that the underlying wave focusing mechanism may be understood in terms of radially inward motion of nodal points of a linearised, axisymmetric, standing wave. This explanation rationalises the ubiquitous observation of such jets accompanying cavity collapse phenomena, spanning length scales from microns to several metres. Expectedly, our theory becomes inaccurate as $\epsilon$ approaches unity. In this strongly nonlinear regime, slender jets form with surface accelerations exceeding gravity by more than an order of magnitude. In this inertial regime, we compare the jets in our simulations with the inertial, self-similar, analytical solution by Longuet-Higgins (J. Fluid Mech., 1983, vol. 127, pp. 103–121) and find qualitative agreement with the same. This analysis demonstrates, from first principles, an example of a jet created purely under gravity from a smooth initial perturbation and provides support to the analytical model of Longuet-Higgins (J. Fluid Mech., 1983, vol. 127, pp. 103–121).

Structured wound angiogenesis instructs mesenchymal barrier compartments in the regenerating nerve

Organ injury stimulates the formation of new capillaries to restore blood supply raising questions about the potential contribution of neoangiogenic vessel architecture to the healing process. Using single-cell mapping, we resolved the properties of endothelial cells that organize a polarized scaffold at the repair site of lesioned peripheral nerves. Transient reactivation of an embryonic guidance program is required to orient neovessels across the wound. Manipulation of this structured angiogenic response through genetic and pharmacological targeting of Plexin-D1/VEGF pathways within an early window of repair has long-term impact on configuration of the nerve stroma. Neovessels direct nerve-resident mesenchymal cells to mold a provisionary fibrotic scar by assembling an orderly system of stable barrier compartments that channel regenerating nerve fibers and shield them from the persistently leaky vasculature. Thus, guided and balanced repair angiogenesis enables the construction of a "bridge" microenvironment conducive for axon regrowth and homeostasis of the regenerated tissue.

Evaluation of the antitumoral effects of the mesoionic compound MI-D: Implications for endothelial cells viability and angiogenesis inhibition

Angiogenesis is considered one of the hallmarks of cancer, assisting tumor progression and metastasis. The mesoionic compound, MI-D, can induce cell death and provoke cytoskeletal and metabolic changes in cancer cells. Using in vitro and in vivo models, this study aimed to evaluate the effects of MI-D on the viability of human endothelial cells (EC) and its ability to inhibit tumor-induced angiogenesis induced by tumoral cells. For in vitro analysis, colon carcinoma (HT29) and endothelial (EA.hy926) cells were used as the tumoral and angiogenesis models, respectively. To evaluate cytotoxicity, methylene blue viability stain and annexin-V/7AAD tests were performed with both cell types. For the angiogenesis experiments, scratch wound healing and capillary tube-like formation assays were performed with the EC. The in vivo tests were performed with the chorioallantoic membrane (HET-CAM) methodology, wherein gelatin sponge implants containing MI-D (5, 25, and 50 μM), HT29 cells, or both were grafted in the CAM. Our data showed that MI-D induced apoptosis in both endothelial and colon carcinoma cells, with a strong cytotoxic effect on the tumoral lineage. The drug inhibited the EC's migration and capillary-like structure formation in vitro. In the HET-CAM assays, MI-D reduced the number of blood vessels in the membrane when grafted alone and accompanied by tumor cells. In this study, MI-D interfered in important steps of angiogenesis, such as maintenance of endothelial cell viability, migration, formation of capillary-like structures, as well tumor-induced neovascularization, reinforcing the hypothesis that MI-D might act as an inhibitor of angiogenesis, and a potential antitumor agent.

Abstract 15509: “Root” Endothelial Cells: A Novel Population That Regulates Lung Capillary and Artery Maintenance and Repair

Introduction: Pulmonary capillary endothelial cells (ECs) are vital for various lung functions, such as maintaining the capillary network, promoting angiogenesis and facilitating gas and nutrient exchange. Recent advancements in single-cell transcriptomics have uncovered novel populations of general capillary ECs (gCaps) in the lungs. Understanding specialized EC types provides valuable insights into pulmonary vascular diseases. We aimed to challenge current understanding of the regenerative capabilities of lung resident ECs. Methods: Highly enriched ECs isolated from rat and mouse lungs underwent single-cell transcriptomics to explore EC population diversity. Results: UMAP annotation of ECs identified five novel general capillary cell populations (gCaps A-E). Lineage confirmation was achieved by Apelin receptor expression. Two distinct zonations (AV-zonation) were observed between pulmonary artery and vein ECs, with specific gCaps phenotypes (A: Clic4+, B: Flot1+, D: Scn7a+, E: Lingo2+), indicating a gradual phenotypic transition from arterial to vein ECs. Within the AV-zonation, a small population of gCapB (Flot1+) cells, resided at the interface of small artery ECs and gCap A and D, exhibiting characteristics of Root cells. RNA velocity analysis suggested Root cells as the origin of capillary and arterial cell lineages. PAGA analysis revealed high transcriptional similarity between gCapB and gCaps A, D, E and arterial cells, suggesting gCapB's role in capillary and arteriole formation and repair. Root cells exhibited upregulation of transcription factors Fos and Jun, promoting EC proliferation and angiogenesis, along with the Foxo and associated cell cycle regulation pathways. Root cells also displayed high G2M and S scores, indicating mitotic activity, supporting their role as the origin of capillary and arterial ECs. Elevated expression of CDKn1a and 1c, crucial for stem cell maintenance and differentiation further implied the repair potential of Root cells. Conclusions: Root Cells (gCapB) play a crucial role in regulating capillary and arteriole formation and repair by serving as a source of capillary and arterial ECs. These findings enhance our understanding of pulmonary vascular maintenance and repair mechanisms.

Abstract 18998: Deletion of the Duffy Antigen Receptor for Chemokines Impairs Blood Flow Recovery in the Mouse Hindlimb Ischemia Model: Role of CCL11

Introduction: Peripheral Artery Disease (PAD) is characterized by obstruction of the arteries in the lower extremities. Impaired angiogenesis plays a major role in the progression of PAD. Pro-angiogenic and anti-angiogenic chemokines are modulated by binding to the Duffy antigen receptor for chemokines (DARC), a non-signaling receptor expressed primarily on erythrocytes. Incidence and severity of PAD is greater in Blacks, ~70% of whom do not express DARC on their erythrocytes due to a common gene variant. Here, we tested the hypothesis that hematopoietic-specific deletion of DARC impairs blood flow recovery in mouse hindlimb ischemia model. Methods: Twelve week old female DARC Flox/Vav1-Cre+ (DARC HKO ) and littermate Vav1-Cre- (wild type, WT) mice underwent unilateral femoral artery ligation and excision. Ischemic muscle tissue and plasma were analyzed at early ischemic phase (day three post ligation) and late ischemic phase (day fourteen post ligation). Blood flow recovery was measured weekly via laser Doppler imaging. Results: DARC HKO mice had poor blood flow recovery compared to WT mice (p&lt;0.05), along with reduced capillary formation and increased inflammation, necrosis and fibrosis in the ischemic gastrocnemius muscles. Amongst the various DARC-bound chemokines assayed, levels of CCL11 (a pro-angiogenic strong DARC-bound chemokine) were significantly reduced in the plasma of DARC HKO mice, both at early and late ischemic phases (p&lt;0.01). CCL11 levels strongly correlated with capillary formation in ischemic hindlimb. CCL11 levels in ischemic muscle tissue were significantly reduced in the DARC HKO mice in the early, but not late, ischemic phase. Conclusions: Loss of DARC on hematopoietic cells has a negative impact on the recovery of perfusion and angiogenesis in the murine hindlimb ischemia model, possibly due to reduced levels of CCL11 consequent to DARC deletion. These findings may be relevant to ethnic differences in susceptibility to PAD and suggest that therapies directed towards increasing CCL11 may be beneficial in Blacks with PAD.

Abstract 14173: Generation and Characterization of Clinically Relevant Disease Models for Port Wine Birthmark Using Induced Pluripotent Stem Cells

Introduction: Port Wine Birthmark (PWB) is a congenital vascular malformation with a progressive development. The current treatments for PWB are Pulse Dye Laser and Photodynamic Laser Treatment. However, the efficacy of blanching the birthmark is inadequate, and the reoccurrence after treatment is a major clinical barrier. Developing clinically relevant disease models that can be used for mechanistic and therapeutic development studies is the critical unmet need. Induced pluripotent stem cell (iPSC) is a powerful tool in different disease models and drug discovery. Besides, iPSC-derived cells can retain and exhibit the disease phenotypes from donors. Therefore, iPSCs and their-derived vascular cells could be potential models for PWB study. Hypothesis: It was hypothesized that PWB iPSC-derived endothelial cell (EC) could retain the disease phenotypes, thus serving as clinically relevant disease models. Methods: PWB lesions and normal skin biopsies were cultured for outgrowths of fibroblasts, followed by reprogramming using CytoTune-iPS Kit. The induction of PWB and normal iPSC into EC was performed using reported protocols with tailored modifications. Bulk RNA and ATAC-seq were performed on both iPSC and iPSC-derived EC. The functional phenotypes of iPSC-derived ECs were characterized using in vitro capillary formation and in vivo Matrigel plug-in assays. Results: PWB EC showed impaired tube formation in vitro with larger perimeters (p=6.22x10 -24 ) and thicker branches (p=1.07x10 -77 ) comparing with normal EC. In plug-in assay, the perfused human vasculatures were characterized by using UEA1 and anti-human CD31 antibodies. Perfused vasculature formed by PWB EC showed larger perimeters (p=8.45x10 -6 ) and greater densities (p=7.34x10 -8 ) than those formed by normal EC. Additionally, 16.6% of perfused vessels formed by PWB EC showed perimeters over 300 μm. KEGG analysis of RNA-seq DEGs showed significantly dysregulated pathways related to cell differentiation, organ development, and lipid metabolism in PWB iPSCs and ECs as compared with normal ones. Conclusions: PWB-derived EC retained critical disease related phenotypes including forming enlarged vessels and thick branches in vitro and in vivo, which can be utilized as valuable PWB models.