Georges Makhoul

Hyaluronic acid-based hydrogel induces neovascularization and improves cardiac function in a rat model of myocardial infarction

OBJECTIVES The use of stem cells in cardiac regeneration is still limited due to low cellular integration and engraftment rates. Consequently, there has been a spurt in research on developing alternative regenerative therapies. Hyaluronic acid (HA) is a major component of the extracellular matrix that is non-immunogenic, and has been implicated in various wound-healing functions such as angiogenesis and inflammation modulation, making it an ideal candidate for regenerative biomaterials. In this study, we examine the potential of acellular hyaluronic acid-based hydrogel in improving cardiac function post-myocardial infarction in a rat model. METHODS Hyaluronic acid-based hydrogel was injected into the peri-infarct region post-myocardial infarction induction in Lewis rats. Cardiac function in control (n = 10) and gel-injected groups (n = 10) was evaluated up to 4 weeks post-myocardial infarction. Evaluation of cardiac function was conducted using transthoracic echocardiography. Histological analysis of scar area was evaluated via haematoxylin and eosin (H & E), and Sirius red staining. Neovascularization was detected using vascular endothelial growth factor (VEGF) staining. RESULTS Evaluation of cardiac function using transthoracic echocardiography revealed a 18.2% (P < 0.01) increase in ejection fraction in gel-injected groups when compared with the control group, almost returning the ejection fraction to baseline levels (preop). Histological analysis of scar area by haematoxylin and eosin (H&E), and Sirius red staining demonstrated decreased scarring, and a 22.6% (P < 0.01) decrease in collagen deposition in the gel-injected group compared with the control group. VEGF staining indicated a significant increase in novel vasculature formation in hydrogel-injected groups when compared with control. CONCLUSIONS Due to its regenerative potential, hyaluronic acid-based hydrogel provides a promising novel therapy to be used alone, or as a scaffold delivering a variety of drugs or cells to combat heart disease in a multifaceted approach.

Tough, In‐Situ Thermogelling, Injectable Hydrogels for Biomedical Applications

Injectable hydrogels are extensively used in drug delivery and tissue engineering to administer drugs, genes, growth factors and live cells. We report a method to produce tough, in-situ thermogelling, non-toxic, injectable hydrogels made of chitosan and hyaluronic acid co-crosslinked with β-glycerophophate and genipin. The gels are highly homogeneous and form within 32 min, i.e., faster than gels crosslinked with either genipin or β-glycerophophate. The shear strength of co-crosslinked hydrogels is 3.5 kPa, higher than any chitosan-based gel reported. Chondrocytes and nucleus pulposus cells thrive inside the gels and produce large amounts of collagen II. Injection in rats shows that the gels form in-vivo within a short time and remain well localized for more than one week while the rats remain healthy and active. The excellent mechanical properties, fast in-situ gelation, good biocompatibility and the ability to encapsulate live cells at physiological conditions make these hydrogels ideal for tissue engineering, especially cartilage regeneration.

Curcumin loaded NIPAAM/VP/PEG-A nanoparticles: physicochemical and chemopreventive properties

This study aims at modifying the synthesis method of preparing N-isopropylacrylamide (NIPAAM)/N-vinyl-2-pyrrolidone (VP)/Polyethylene glycol monoacrylate (PEG-A) polymeric nanoparticles encapsulating curcumin as a model drug. The optimal concentration of nanoparticle reagents was determined using Fourier Transform Infrared Spectroscopy. Curcumin nanoparticles mean hydrodynamic size was found to be 104 nm with zeta potential of 3 ± 13 mV. The release kinetic study of curcumin nanoparticles indicates that a maximum release of curcumin at 24 h positively correlates with increase in temperature; however, change in pH did not produce any substantial drug release. In vitro cell viability assay performed on cancer cells exposed to various concentrations of model compound displayed the IC50 ranging between 100 and 200 μg/mL for human prostate cancer cells (PC3 cells) and 50 and 200 μg/mL for epidermoid carcinoma (A431 cell line). The Hoechst staining and phase contrast micrographs for 48 h exposure of curcumin nanoparticles at a concentration of 400 μg/mL resulted in almost 92% of cells death in both cell lines. This study concludes that the physiochemical characteristics of NIPAAM/VP/PEG-A polymer with key features of water solubility, sustained drug release, small particle size make these nanoparticles a prominent drug delivery device.

Hypoxia modulates cell migration and proliferation in placenta-derived mesenchymal stem cells

Objectives For more than a decade, stem cells isolated from different tissues have been evaluated in cell therapy. Among them, the human bone marrow–derived mesenchymal stem cells (hBM‐MSCs) were investigated extensively in the treatment of myocardial infarction. Recently, the human placenta–derived mesenchymal stem cells (hPD‐MSCs), which are readily available from a biological waste, appear to be a viable alternative to hBM‐MSCs. Methods C‐X‐C chemokine receptor type 4 (CXCR4) gene expression and localization were detected and validated in hPD‐MSCs and hBM‐MSCs via polymerase chain reaction and immunofluorescence. Subsequently, cell culture conditions for CXCR4 expression were optimized in stromal‐derived factor‐1 alpha (SDF1‐&agr;), glucose, and cobalt chloride (CoCl2) by the use of cell viability, proliferation, and migration assays. To elucidate the cell signaling pathway, protein expression of CXCR4, hypoxia‐inducible factor‐1&agr;, interleukin‐6, Akt, and extracellular signal‐regulated kinase were analyzed by Western blot. CXCR4‐positive cells were sorted and analyzed by florescence‐activated cell sorting. Results CXCR4 was expressed on both hPD‐MSCs and hBM‐MSCs at the basal level. HPD‐MSCs were shown to have a greater sensitivity to SDF‐1&agr;–dependent cell migration compared with hBM‐MSCs. In addition, CXCR4 expression was significantly greater in both hPD‐MSCs and hBM‐MSCs with SDF‐1&agr; or CoCl2‐induced hypoxia treatment. However, CXCR4+ hPD‐MSCs population increased by 10‐fold in CoCl2‐induced hypoxia. In contrast, only a 2‐fold increase was observed in the CXCR4+ hBM‐MSCs population in similar conditions. After CoCl2‐induced hypoxia, the CXCR4/mitogen‐activated protein kinase kinase/extracellular signal‐regulated kinase signaling pathway was activated prominently in hPD‐MSCs, whereas in hBM‐MSCs, the CXCR4/phosphatidylinositol 3‐kinase/Akt pathway was triggered. Conclusions Our current results suggest that hPD‐MSCs could represent a viable and effective alternative to hBM‐MSCs for translational studies in cardiocellular repair.

Placental Mesenchymal Stem Cells: A Unique Source for Cellular Cardiomyoplasty

In coronary heart disease, the use of stem cells for regeneration purposes has been broadly studied. Whereas bone marrow mesenchymal stem cells remain the most extensively investigated, other cell sources have been reported. Here we discuss and compare the characteristics of placenta-derived mesenchymal stem cells as a novel alternative cell source for cellular cardiomyoplasty. These cells are isolated from the human term placenta, which is normally discarded post partum. With their lack of ethical conflicts and young age, the readily available placenta-derived mesenchymal stem cells could be more suitable for myocardial regenerative therapy.

Conditioned medium of H9c2 triggers VEGF dependent angiogenesis by activation of p38/pSTAT3 pathways in placenta derived stem cells for cardiac repair

AIMS Cardiomyocytes are understood to possess a limited regenerative capacity. Any myocardial insult leads to an irreversible injury. Mesenchymal stem cell differentiation into cardiomyocyte-like cells stands as one of the leading experimental therapies. However, a candidate cell source has yet to be defined. Here, we examined the in vitro and in vivo cardiac differentiation potential of human placenta derived stem cells (hPDSCs); a unique, abundant, and non-immunogenic cell source. MAIN METHODS H9c2 cell culture medium was applied to hPDSCs at different ratios for a period of 4weeks. In parallel, hPDSCs, human bone marrow stem cells, or cell free culture medium was injected in peri-infarcted regions induced in rat hearts. KEY FINDINGS In vitro, hPDSCs pre-conditioned with H9c2 cell culture medium proportionally over-expressed alpha sarcoplasmic actinin and displaced connexin 43 from the cytoplasm to the cell membrane. Additionally, pre-conditioning promoted hPDSCs survival and triggered vascular endothelial growth factor (VEGF) dependent angiogenesis by activating the pAkt and p38MAPK/pSTAT3 pathways. In vivo, echocardiography analysis showed a significant improvement in cardiac parameters in the rats injected with hPDSCs, similar to the human bone marrow stem cells injected group. Moreover, hPDSCs detected within rat cardiac tissues expressed troponin I and myosin heavy chain. In accordance with the pre-conditioning findings, VEGF positive neovessels were observed in hearts injected with hPDSCs. SIGNIFICANCE hPDSCs have the potential to differentiate into cardiac-like cells and induce angiogenesis via paracrine effects. With the advantages of easy availability and young age, these cells could be more suitable for clinical translation.