Thick PCL Fibers Improving Host Remodeling of PGS-PCL Composite Grafts Implanted in Rat Common Carotid Arteries.

Vasculopathy and the consequential ischemia are major medical challenges. Grafting is an effective treatment to vascular occlusion. However, autologous grafting, despite scarcity, is the only choice for small diameter blood vessels. Synthetic grafts can fill the gap if they can work satisfactorily in arterial circulation. Electrospun polycaprolactone (PCL) sheathed porous poly(glycerol sebacate) (PGS) vascular grafts have good performances in arterial circulation in abdominal aortas and carotid arteries in rats. However, a major issue associated with the graft remodeling in vivo is limited neo-tissue formation inside PCL sheaths. Small pores of PCL sheaths inhibit cell infiltration and migration. To increase porosity of PCL sheaths of PGS-PCL composite grafts, diameters of electrospun PCL fibers are increased. The thick PCL fibers encourage cell migration and elicit a higher degree of CD206+ cells. In addition, some of the CD206+ cells co-express vascular cell markers in the thick-fiber grafts. The thick-fiber grafts also show improved mechanical properties and a higher elastin and collagen content. The data demonstrate the feasibility of improving graft vascular remodeling by increasing PCL fiber diameters and the critical role of CD206+ cells during graft vascular remodeling.

Impact of surface plasmon polaritons on photorefractive effect in dye doped liquid crystal cells with ZnSe interlayers.

Great impact of surface plasmon polaritons (SPPs) on photorefractive effect in ZnSe/liquid crystal interface was observed and studied in dye pyrromethane 597 doped 4,4'-n-pentylcyanobiphenyl (5CB) liquid crystal (LC) cells sandwiched with ZnSe coated ITO glass plates. Locally electrostatic modification of ZnSe in charge carrier density makes possible visible light excitation of SPPs in the LC/ZnSe interfaces. A tentative physical picture of SPP mediation was proposed in elucidating associated findings, including photoinduced scattering enhancement at low electric field and then reduction at high field, stepwise up- and down-turns in exponential gain coefficient, and 2D diffraction patterns. This work may open a new way toward tunable low-loss visible excitation of SPPs for plasmonic applications, specifically for organic plasmonics.

Impact of thickness of liquid crystal layer on response rate and exponential gain coefficient with assistance of ZnSe film.

A response time as short as 5.4 ms and an exponential gain coefficient as large as 1795.0 cm(-1) were obtained in C(60) doped 4,4'-n-pentylcyanobiphenyl liquid crystal cells sandwiched with two indium tin oxide glass plates coated with nanoscale photoconductive ZnSe films, which is believed to be facilitating charge-carrier generation and transportation and, hence, to be responsible for the fast response rate. The surface-mediated photorefractive effect and the ZnSe interlayers were both behind the high gain coefficients. The two-dimensional diffraction patterns observed in our system are also discussed.

Adventitial delivery of miR-145 to treat intimal hyperplasia post vascular injuries through injectable and in-situ self-assembling peptide hydrogels.

Intimal hyperplasia is a common lesion that can be observed in diverse vascular diseases. Drug-eluting stents and drug-coated balloons, which can release anti-proliferative agents to inhibit smooth muscle cell (SMC) proliferation, are developed to prevent intimal hyperplasia. However, these intervention devices still cannot achieve satisfactory clinical outcomes. In contrast to endovascular drug delivery, vascular adventitial drug delivery is a new strategy. To develop a vascular adventitial drug delivery system to treat intimal hyperplasia post vascular injuries, we loaded miR-145-5p-agomir (miR-145) into an injectable and in-situ self-assembling RAD peptide hydrogel. In vitro data showed that the miR-145 could be well incorporated into the RAD peptide hydrogels and released in a slow and controlled manner. The released miR-145 could transfect SMCs successfully, and the transfected SMCs exhibited a reduced migration capacity and higher expressions of SMC contractile biomarkers as compared to the non-transfected SMCs. In vivo data showed that the retention of the miR-145 was greatly elongated by the RAD peptide hydrogels. In addition, the application of the miR-145-loaded RAD peptide hydrogels surrounding injured arteries decreased the proliferative SMCs, promoted the regeneration of endothelium, reduced the macrophage infiltration, inhibited the neointimal formation and prevented adverse ECM remodeling via downregulation of KLF4 expression. The RAD peptide hydrogels loaded with miR-145 can successfully inhibit intimal hyperplasia after vascular injuries and thus hold great potential as an innovative extravascular drug delivery approach to treat vascular diseases. STATEMENT OF SIGNIFICANCE: Intimal hyperplasia is a common lesion that can be observed in diverse vascular diseases. Drug-eluting stents and drug-coated balloons, which can release anti-proliferative agents to inhibit smooth muscle cell (SMC) proliferation, are developed to prevent intimal hyperplasia. However, these intervention devices still cannot achieve satisfactory clinical outcomes. In contrast to endovascular drug delivery, vascular adventitial drug delivery is a new strategy. Our work here demonstrates that the RAD peptide hydrogels loaded with miR-145-5p-agomir (miR-145) can successfully reverse intimal hyperplasia after vascular injuries and thus hold great potential as an innovative vascular adventitial drug delivery approach to treat vascular diseases. Our work proposes a possible paradigm shift from endovascular drug delivery to extravascular drug delivery for vascular disorder treatment.

Blending with transition metals improves bioresorbable zinc as better medical implants.

Zinc (Zn) is a new class of bioresorbable metal that has potential for cardiovascular stent material, orthopedic implants, wound closure devices, etc. However, pure Zn is not ideal for these applications due to its low mechanical strength and localized degradation behavior. Alloying is the most common/effective way to overcome this limitation. Still, the choice of alloying element is crucial to ensure the resulting alloy possesses sufficient mechanical strength, suitable degradation rate, and acceptable biocompatibility. Hereby, we proposed to blend selective transition metals (i.e., vanadium-V, chromium-Cr, and zirconium-Zr) to improve Zn's properties. These selected transition metals have similar properties to Zn and thus are beneficial for the metallurgy process and mechanical property. Furthermore, the biosafety of these elements is of less concern as they all have been used as regulatory approved medical implants or a component of an implant such as Ti6Al4V, CoCr, or Zr-based dental implants. Our study showed the first evidence that blending with transition metals V, Cr, or Zr can improve Zn's properties as bioresorbable medical implants. In addition, three in vivo implantation models were explored in rats: subcutaneous, aorta, and femoral implantations, to target the potential clinical applications of bioresorbable Zn implants.

Polydopamine (PDA) coatings with endothelial vascular growth factor (VEGF) immobilization inhibiting neointimal formation post zinc (zn) wire implantation in rat aortas.

BACKGROUND: Bioresorbable stents are designed to provide temporary mechanical support to the coronary arteries and then slowly degrade in vivo to avoid chronic inflammation. Zinc (Zn) is a promising material for bioresorbable stents; However, it can cause inflammation and neointimal formation after being implanted into blood vessels. METHODS: To improve biocompatibility of Zn, we first coated it with polydopamine (PDA), followed by immobilization of endothelial vascular growth factor (VEGF) onto the PDA coatings. Adhesion, proliferation, and phenotype maintenance of endothelial cells (ECs) on the coated Zn were evaluated in vitro. Then, a wire aortic implantation model in rats mimicking endovascular stent implantation in humans was used to assess vascular responses to the coated Zn wires in vivo. Thrombosis in aortas post Zn wire implantation, degradation of Zn wires in vivo, neointimal formation surrounding Zn wires, and macrophage infiltration and extracellular matrix (ECM) remodeling in the neointimas were examined. RESULTS: In vitro data showed that the PDA-coated Zn encouraged EC adhesion, spreading, proliferation, and phenotype maintenance on its surfaces. VEGF functionalization on PDA coatings further enhanced the biocompatibility of Zn to ECs. Implantation of PDA-coated Zn wires into rat aortas didn't cause thrombosis and showed a faster blood flow than pure Zn or the Zn wires coated with VEGF alone. In addition, the PDA coating didn't affect the degradation of Zn wires in vivo. Besides, the PDA-coated Zn wires reduced neointimal formation, increased EC coverage, decreased macrophage infiltration, and declined aggrecan accumulation in ECM. VEGF immobilization onto PDA coatings didn't cause thrombosis and affect Zn degradation in vivo as well, and further increased the endothelization percentage as compared to PDA coating alone, thus resulting in thinner neointimas. CONCLUSION: These results indicate that PDA coatings with VEGF immobilization would be a promising approach to functionalize Zn surfaces to increase biocompatibility, reduce inflammation, and inhibit neointimal formation after Zn implantation in vivo.

A pDNA/rapamycin nanocomposite coating on interventional balloons for inhibiting neointimal hyperplasia.

Drug-coated balloon (DCB) is a therapeutic method that can effectively deliver antiproliferative drugs such as paclitaxel and rapamycin (RAPA) with no permanent implants left behind. However, delayed reendothelialization due to the toxicity of the delivered drugs leads to poor therapeutic effects. Here, we propose a new design of DCB coating, which incorporates both vascular endothelial growth factor (VEGF)-encoding plasmid DNA (pDNA) that can promote endothelial repair and RAPA into protamine sulfate (PrS). We demonstrate that the PrS/pDNA/RAPA coating had stability and good anticoagulation properties in vitro. We further show that the coating exhibited excellent transfer capacity from balloon substrates to vessel walls both in vitro and in vivo. Furthermore, the PrS/pDNA/RAPA coating effectively inhibited neointimal hyperplasia after balloon-induced vascular injuries through the down-regulation of the mammalian target of Rapamycin (mTOR) and promoted endothelium regeneration through increased expression of VEGF in vivo. These data indicate that our nanocomposite coating has great potential for use as a novel coating of DCB to treat neointimal hyperplasia after vascular injuries.

Association between electronic cigarettes use and whole blood cell among adults in the USA-a cross-sectional study of National Health and Nutrition Examination Survey analysis.

Electronic cigarettes (E-cigarettes) use is an emerging public health problem. Trying to assess the independent associations between E-cigarettes use and whole blood cell in a nationally representative sample of the US adults is very important for the smoking population. Using E-cigarettes data from NHANES (National Health and Nutrition Examination Survey) 2013-2018, 17,180 adults were included in this cross-sectional analysis. All participants were stratified into four different groups (non-smoke group N=10087, E-cigarettes group N=52, dual-smoke group N=249, cigarettes group N=6792) based on questions SMQ020 (smoked at least 100 cigarettes in life) and SMQ690H (used last 5 days E-cigarettes). Whole blood cell tests included white blood cell (WBC) with differentials, red blood cell (RBC) with characteristics, and platelet variables. With adjusted by age, gender, and race ethnicity, multivariate logistic regression analyses were used to assess independent associations between E-cigarettes group and other groups for different whole blood cell variables. A total of 17,180 participants were included in the study; 47.9% were males, with a mean age of 46.99 (±0.29). In WBC-related variables, non-smoke group had the lowest value in WBC counts (7.15±0.05), lymphocyte (2.15±0.02), and monocyte (0.57±0.01), among the four different groups. In RBC-related variables, non-smoke group had the lowest value in mean cell volume (MCV, 88.46±0.14, p<0.05) and mean cell hemoglobin (MCH, 29.73±0.06, p<0.05), among the four different groups. In adjusted analysis, WBC (OR = 0.97, 95% CI: 0.96-0.98, p<0.001), especially lymphocyte (OR = 0.97, 95% CI: 0.96-0.98, p<0.001) and monocyte (OR = 0.11, 95% CI: 0.02-0.66, p<0.001) of non-smoke group, showed negative significant effect for E-cigarettes group. Meanwhile, lower odds of MCV (OR = 0.91, 95% CI: 0.81-1.04, p<0.05) and MCH (OR = 0.81, 95% CI: 0.65-1.00, p<0.05) in non-smoke group were observed compared to E-cigarettes group. Conversely, for dual-smoke group and cigarette group, there was no significant results in all whole blood cell variables compared to E-cigarettes group. E-cigarettes use might be associated with a systemic response that could lead to an increase in WBC, especially lymphocytes and monocytes, in the US adults. Meanwhile, the properties of RBC might also be influenced simultaneously; MCV and MCH in E-cigarettes population were bigger than the non-smoke population.

Improved mechanical, degradation, and biological performances of Zn-Fe alloys as bioresorbable implants.

Zinc (Zn) is a promising bioresorbable implant material with more moderate degradation rate compared to magnesium (Mg) and iron (Fe). However, the low mechanical strength and localized degradation behavior of pure Zn limit its clinical applications. Alloying is one of the most effective ways to overcome these limitations. After screening the alloying element candidates regarding their potentials for improvement on the degradation and biocompatibility, we proposed Fe as the alloying element for Zn, and investigated the in vitro and in vivo performances of these alloys in both subcutaneous and femoral tissues. Results showed that the uniformly distributed secondary phase in Zn-Fe alloys significantly improved the mechanical property and facilitated uniform degradation, which thus enhanced their biocompatibility, especially the Zn-0.4Fe alloy. Moreover, these Zn-Fe alloys showed outstanding antibacterial property. Taken together, Zn-Fe alloys could be promising candidates as bioresorbable medical implants for various cardiovascular, wound closure, and orthopedic applications.

Inhibition of neointimal hyperplasia in balloon-induced vascular injuries in a rat model by miR-22 loading Laponite hydrogels.

Percutaneous coronary intervention (PCI) is the mainstream treatment to widen narrowed or obstructed coronary arteries due to pathological conditions. However, the post-operational neointimal hyperplasia occurs because of endothelium denudation during surgical procedures and the following inflammation. MicroRNAs (miRs) are new therapeutics of great potential for cardiovascular diseases. However, miRs easily degrade in vivo. A vehicle that can maintain their bioactivities and extend their retention at the site of delivery is prerequisite for miRs to play their roles as therapeutic reagents. Here, we reported the use of the Laponite hydrogels to deliver miR-22 that are modulators of phenotypes of smooth muscle cells (SMCs). The Laponite hydrogels allow a homogenous distribution of miR-22 within the gels, which had the capacity to transfect SMCs in vitro. Upon the injection of the miR-22 incorporated in the Laponite hydrogels in vivo, miR-22 could be well retained surrounding arteries for at least 7 days. Moreover, the miR-22 loading Laponite hydrogels inhibited the neointimal formation, reduced the infiltration of the macrophages, and reversed the adverse vascular ECM remodeling after the balloon-induced vascular injuries by upregulation of miR-22 and downregulation of its target genes methyl-CpG binding protein 2 (MECP2). The application of the Laponite hydrogels for miR local delivery may offer a novel strategy to treat cardiovascular diseases.

Mir-22-incorporated polyelectrolyte coating prevents intima hyperplasia after balloon-induced vascular injury.

Drug-coated balloons (DCBs) offer potential to deliver drugs to treat coronary lesions but without leaving permanent implants behind. Paclitaxel and sirolimus are anti-proliferation drugs that are commonly used in commercially available DCBs. However, these drugs present significant cytotoxicity concern and low efficacy in vivo. Here, we use microRNA-22 (miR-22) as balloon loaded drugs and polyelectrolyte complexes (PECs) polyethyleneimine/polyacrylic acid (PEI/PAA) as balloon coatings to establish a new DCB system through the ultrasonic spray method. The PEI/PAA forms a stable and thin coating on the balloon, which resulted in a good transfer capacity to the vessel wall both in vitro and in vivo. miR-22 that could modulate smooth muscle cell (SMC) phenotype switching is incorporated into the PEI/PAA coating and shows a sustained release profile. The PEI/PAA/miR-22 coated balloon successfully inhibits intima hyperplasia after balloon-induced vascular injury in a rat model through decreasing proliferative SMCs via the miR-22-methyl-CpG binding protein 2 (MECP2) axis. Our findings indicate that balloons coated with PEI/PAA/miR-22 have great potential to be promising DCBs in the treatment of cardiovascular disease.

[Betulinic acid ameliorates impairment of endothelium-dependent relaxation induced by oxidative stress in rat aorta].

OBJECTIVE: To investigate the effect of betulinic acid (BA) on relaxation in isolated rat aortic rings and its antioxidant property on oxidative stress of blood vessels. METHODS: Aortic rings were isolated and BA was cumulatively added into organ bath. Isometric tension of endothelium intact or endothelium denuded thoracic aortic rings previously contracted by phenylephrine (PE) was recorded. Then aortic rings were randomly divided into normal control group, BA control group, H(2)O(2) group and BA+H(2)O(2) group, after being previously contracted by PE, isometric tension of endothelium-dependent relaxation induced by Ach was recorded. RESULT: Exposure of intact endothelium rings previously contracted by PE to BA at the concentrations of 10(-7) mol/L-10(-4) mol/L evoked a significant concentration dependent relaxation, which was inhibited by pretreatment with N omega-nitro-L-arginine methyl ester (L-NAME, 10(-4)mol/L), but not by indometacin (10(-5)mol/L). The pD2 value of BA was 5.24 ± 0.04, and the EC(50)value was 2.45 x 10(-6)mol/L. Exposure of endothelium denuded rings previously contracted by PE to BA did not affect the relaxation in isolated aortic rings. ACh induced a dose-dependent relaxation that was weakened by pretreatment with H(2)O(2) (5 10(-4) mol/L) for 15 min. The EC(50) of BA markedly attenuated the inhibition of relaxation induced by H(2)O(2). CONCLUSION: BA can evoke a concentration-dependent relaxation in aortic rings previously contracted by PE, which may be mediated by NO. And the decrease of endothelium-dependent relaxation in rat aortic rings exposed to H(2)O(2) can be markedly attenuated by BA, which may be mediated by reducing oxidative stress and maintaining the activity of NO in aortic rings.

Slow degrading poly(glycerol sebacate) derivatives improve vascular graft remodeling in a rat carotid artery interposition model.

Porous synthetic grafts made of poly (glycerol sebacate) (PGS) can transform into autologous vascular conduits in vivo upon degradation of PGS. A long-held doctrine in tissue engineering is the necessity to match degradation of the scaffolds to tissue regeneration. Here, we tested the impact of degradation of PGS and its derivative in an interposition model of rat common carotid artery (CCA). Previous work indicates a complete degradation of PGS within approximately 2 weeks, likely at the fast end of the spectrum. Thus, the derivation of PGS focuses on delay degradation by conjugating the free hydroxy groups in PGS with a long chain carboxylic acid: palmitic acid, one of the most common lipid components. We evaluated two of the resultant palmitate-PGS (PPGS) in this study: one containing 9% palmitate (9-PPGS) and the other16% palmitate (16-PPGS). 16-PPGS grafts had the highest patency. Ultrasound imaging showed that the lumens of 16-PPGS grafts were similar to CCA and smaller than 9-PPGS and PGS grafts 12 weeks post-operation. Immunohistological and histological examination showed an endothelialized lumens in all three types of grafts within 4 weeks. Inflammatory responses to 16-PPGS grafts were limited to the adventitial space in contrast to a more diffusive infiltration in 9-PPGS and PGS grafts in week 4. Examination of calponin+ and αSMA+ cells revealed that 16-PPGS grafts remodeled into a distinctive bi-layered wall, while the walls of 9-PPGS grafts and PGS grafts only had one thick layer of smooth muscle-like cells. Correspondingly, the expression of collagen III and elastin displayed an identical layered structure in the remodeled 16-PPGS grafts, in contrast to a more spread distribution in 9-PPGS and PGS grafts. All the three types of grafts exhibited the same collagen content and burst pressure after 12 weeks of host remodeling. However, the compliance and elastin content of 16-PPGS grafts in week 12 were closest to those of CCA. Overall, placing the degradation of PGS derived elastomer to a window of 4-12 weeks results in vascular conduits closer to arteries in a rat carotid artery interposition model over a 12-week observation period.

Evolution of metallic cardiovascular stent materials: A comparative study among stainless steel, magnesium and zinc.

A cardiovascular stent is a small mesh tube that expands a narrowed or blocked coronary artery. Unfortunately, current stents, regardless metallic or polymeric, still largely fall short to the ideal clinical needs due to late restenosis, thrombosis and other clinical complications. Nonetheless, metallic stents are preferred clinically thanks to their superior mechanical property and radiopacity to their polymeric counterparts. The emergence of bioresorbable metals opens a window for better stent materials as they may have the potential to reduce or eliminate late restenosis and thrombosis. In fact, some bioresorbable magnesium (Mg)-based stents have obtained regulatory approval or under trials with mixed clinical outcomes. Some major issues with Mg include the too rapid degradation rate and late restenosis. To mitigate these problems, bioresorbable zinc (Zn)-based stent materials are being developed lately with the more suitable degradation rate and better biocompatibility. The past decades have witnessed the unprecedented evolution of metallic stent materials from first generation represented by stainless steel (SS), to second generation represented by Mg, and to third generation represented by Zn. To further elucidate their pros and cons as metallic stent materials, we systematically evaluated their performances in vitro and in vivo through direct side-by-side comparisons. Our results demonstrated that tailored Zn-based material with proper configurations could be a promising candidate for a better stent material in the future.

Co-culture of human umbilical vein endothelial cells and human bone marrow stromal cells into a micro-cavitary gelatin-methacrylate hydrogel system to enhance angiogenesis.

Vascular tissue engineering seeks to develop functional blood vessels that comprise of both endothelial cells and pericytes for translational medicine and is often faced with numerous challenges such as nutrients and wastes diffusion problem in the centre of the scaffolds. Various strategies have been adopted to solve the diffusion problem in thick engineered scaffolds. Typically, microchannels or dissolvable microspheres are introduced into three-dimensional (3D) scaffolds as an alternative way to improve the infiltration of scaffolds and endothelial cells are usually incorporated into the biomaterials. While some research groups now focus on finding supporting cells to build further vascularized structures in the scaffolds. In this study, a bioinspired 3D gelatin-methacrylate (Gel-MA) hydrogel with dissolvable microspheres was created to encapsulate human bone marrow stromal cells (HMSCs) and human umbilical vein endothelial cells (HUVECs) which was used to investigate whether HMSCs could play a pericytes-like role and enhance vascularization within the engineered scaffolds. The results showed co-culture of HMSCs and HUVECs demonstrated significantly improved vascularization when compared to either HUVECs or HMSCs monoculture. Angiogenic genes were expressed significantly higher in co-culture group. Moreover, when implanting the pre-vascularized scaffolds in vivo, co-culture system integrated more successfully with host tissue and showed higher host tissue invasion than any other groups. More importantly, both the qPCR and immunofluorescence results indicated MSCs differentiated towards pericytes to enhance vascularization in this study. This paper highlights the enhanced capability of 3D micro-cavitary Gel-MA hydrogel for co-culturing HUVECs and HMSCs to promote vascularization which presents a potential strategy for future tissue repair and regeneration.

Mechanical Strength, Biodegradation, and in Vitro and in Vivo Biocompatibility of Zn Biomaterials.

Zn-based biomaterials have emerged as promising new types of bioresorbable metallics applicable to orthopedic devices, cardiovascular stents, and other medical applications recently. Compared to other degradable metallic biomaterials (i.e., Mg- or Fe-based), Zn biomaterials have a more appropriate corrosion rate without hydrogen gas evolution. Here, we evaluated the potential of Zn-based metallics as medical implants, both in vitro and in vivo, alongside a standard benchmark Mg alloy, AZ31. The mechanical properties of the pure Zn were not strong enough but were significantly enhanced (microhardness > 70 kg/mm2, strength > 220 MPa, elongation > 15%) after alloying with Sr or Mg (1.5 at. %), surpassing the minimal design criteria for load-bearing device applications. The corrosion rate of Zn-based biomaterials was about 0.4 mm/year, significantly slower than that of AZ31. The measured cell viability and proliferation of three different human primary cells fared better for Zn-based biomaterials than AZ31 using both direct and indirect culture methods. Platelet adhesion and activation on Zn-based materials were minimal, significantly less than on AZ31. The hemolysis ratio of red cells (<0.5%) after incubation with Zn-based materials was also well below the ISO standard of 5%. Moreover, Zn-based biomaterials promoted stem cell differentiation to induce the extracellular matrix mineralization process. In addition, in vivo animal testing using subcutaneous, bone, and vascular implantations revealed that the acute toxicity and immune response of Zn-based biomaterials were minimal/moderate, comparable to that of AZ31. No extensive cell death and foreign body reactions were observed. Taken together, Zn-based biomaterials may have a great potential as promising candidates for medical implants.

In Situ Organ-Specific Vascularization in Tissue Engineering.

Other than a few avascular tissues, almost all human tissues are connected to the systemic circulation via blood vessels that promote metabolism and function. Accordingly, engineered vascularization is a vital goal in tissue engineering for regenerative medicine. Endothelial cells (ECs) play a central role in vascularization with two significant specificities: physical interfaces between vascular stroma and blood, and phenotypic organ-specificity. Biomaterial scaffolding technologies that address these unique properties of ECs have been developed to promote the vascularization of various engineered tissues, and these have advanced from mimicking vascular architectures ex situ towards promoting spontaneous angiogenic remodeling in situ. Simultaneously, endothelial progenitor cells (EPCs) and organ-specific ECs are attracting more and more attention with the increasing awareness of the diversity of ECs in different organs.

Respective Effects of Gelatin-Coated Polydimethylsiloxane (PDMS) Substrates on Self-renewal and Cardiac Differentiation of Induced Pluripotent Stem Cells (iPSCs).

The effects of substrate stiffness on the development of cardiomyocytes have been investigated extensively. Polydimethylsiloxane (PDMS) elastomer is one of biomaterials that are commonly used to explore the effects of substrate compliance on stem cell differentiation. Although the effects of substrate stiffness on cardiac differentiation of pluripotent stem cells, such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), have been reported, whether the stiffness of PDMS-based substrates could enhance differentiation of iPSCs toward cardiomyocyte lineage or not remains unknown. In this study, we found that a denser gelatin distribution and a higher gelatin adsorption on the stiffer PDMS. In addition, nanotopographies on PDMS substrates with different stiffness were distinct. iPSCs on the stiffer PDMS substrates showed higher pluripotency marker but lower cardiac gene expressions. In contrast, iPSCs on the softer PDMS substrates revealed lower pluripotency marker but higher cardiac gene expressions. These results indicate that stiffer PDMS substrates with gelatin coating could be used to support iPSC self-renewal and softer PDMS substrates coated with gelatin could be used for enhanced cardiac differentiation of iPSCs.

Improvement of endothelial progenitor outgrowth cell (EPOC)-mediated vascularization in gelatin-based hydrogels through pore size manipulation.

In addition to chemical compositions, physical properties of scaffolds, such as pore size, can also influence vascularization within the scaffolds. A larger pore has been shown to improve host vascular tissue invasion into scaffolds. However, the influence of pore sizes on vascularization by endothelial cells directly encapsulated in hydrogels remains unknown. In this study, micro-cavitary hydrogels with different pore sizes were created in gelatin-methacrylate hydrogels with dissolvable gelatin microspheres (MS) varying in sizes. The effect of pore sizes on vascular network formation by endothelial progenitor outgrowth cells (EPOCs) encapsulated in hydrogels was then investigated both in vitro and in vivo. When cultured in vitro, vascular networks were formed around pore structures in micro-cavitary hydrogels. The middle pore size supported best differentiation of EPOCs and thus best hydrogel vascularization in vitro. When implantation in vivo, functional connections between encapsulated EPOCs and host vasculature micro-cavitary hydrogels were established. Vascularization in vivo was promoted best in hydrogels with the large pore size due to the increased vascular tissue invasion. These results highlight the difference between in vitro and in vivo culture conditions and indicate that pore sizes shall be designed for in vitro and in vivo hydrogel vascularization respectively. Pore sizes for hydrogel vascularization in vitro shall be middle ones and pore sizes for hydrogel vascularization in vivo shall be large ones. STATEMENT OF SIGNIFICANCE: This study reveals that the optimal pore size for hydrogel vascularization in vitro and in vivo is different. The middle pore size supported best differentiation of EPOCs and thus best hydrogel vascularization in vitro, while vascularization in vivo was promoted best in hydrogels with the large pore size due to the increased vascular tissue invasion. These results highlight the difference between in vitro and in vivo culture conditions and indicate that pore sizes shall be designed for in vitro and in vivo hydrogel vascularization respectively. Pore sizes for hydrogel vascularization in vitro shall be middle ones and pore sizes for hydrogel vascularization in vivo shall be large ones.

Real-time and non-invasive monitoring of embryonic stem cell survival during the development of embryoid bodies with smart nanosensor.

Embryonic stem cells (ESCs)-derived embryoid body (EB) is a powerful model for the study of early embryonic development and the discovery of therapeutics for tissue regeneration. This article reports a smart nanosensor platform for labeling and tracking the survival and distribution of ESCs during the EB development in a real-time and non-invasive way. Compared with the cell tracker (i.e. DiO) and the green fluorescent protein (GFP), nanosensors provide the homogenous and highly-efficient ESC labeling. Following the internalization, intracellular nanosensors gradually release the non-fluorescent molecules that become fluorescent only in viable cells. This allows a continuous monitoring of ESC survival and distribution during the process of EB formation. Finally, we confirm that nanosensor labeling does not cause the significant influences to biological properties of the ESCs and EBs. STATEMENT OF SIGNIFICANCE: The distribution pattern of viable embryonic stem cells (ESCs) within embryoid body (EB) is closely related with the maturation of EBs. Noninvasive and real-time monitoring of viable ESC distribution in EBs would allow researchers to optimize the culturing condition in time during the EB development and to select the suitable EBs for subsequent applications.