Amniotic Membrane Enhances the Characteristics and Function of Stem Cell-Derived Retinal Pigment Epithelium Sheets by Inhibiting the Epithelial-Mesenchymal Transition.

Human pluripotent stem cell-derived retinal pigment epithelium (iRPE) is an attractive cell source for disease modeling and cell replacement therapy of retinal disorders with RPE defects. However, there are still challenges to develop appropriate culture conditions close to in vivo microenvironment to generate iRPE sheets, which mimic more faithfully the characteristics and functions of the human RPE cells. Here, we developed a simple, novel platform to construct authentic iRPE sheets using human amniotic membrane (hAM) as a natural scaffold. The decellularized hAM (dAM) provided a Bruch's membrane (BM)-like bioscaffold, supported the iRPE growth and enhanced the epithelial features, polarity distribution and functional features of iRPE cells. Importantly, RNA-seq analysis was performed to compare the transcriptomes of iRPE cells cultured on different substrates, which revealed the potential mechanism that dAM supported and promoted iRPE growth was the inhibition of epithelial-mesenchymal transition (EMT). The tissue-engineered iRPE sheets survived and kept monolayer when transplanted into the subretinal space of rabbits. All together, our results indicate that the dAM imitating the natural BM allows for engineering authentic human RPE sheets, which will provide valuable biomaterials for disease modeling, drug screening and cell replacement therapy of retinal degenerative diseases. STATEMENT OF SIGNIFICANCE: Engineered RPE sheets have a great advantage over RPE cell suspension for transplantation as they support RPE growth in an intact monolayer which RPE functions are dependent on. The substrates for RPE culture play a critical role to maintain the physiological functions of the RPE in stem cell therapies for patients with retinal degeneration. In this study, we constructed engineered iRPE sheets on the decellularized human amniotic membrane scaffolds, which contributed to enhancing epithelial features, polarity distribution and functional features of iRPE. dAM exhibited the ability of anti-epithelial mesenchymal transition to support iRPE growth. Furthermore, the results of transplantation in vivo demonstrated the feasibility of iRPE sheets in retina regenerative therapy. Engineering RPE sheets on dAM is a promising strategy to facilitate the development of iRPE replacement therapy and retinal disease modeling.

Dual functionalization of poly(ε-caprolactone) film surface through supramolecular assembly with the aim of promoting in situ endothelial progenitor cell attachment on vascular grafts.

In this study, we developed a method for the dual functionalization of a poly(ε-caprolactone) (PCL) surface by means of the supramolecular assembly technology. Polyethylene glycol (PEG), with resistance to protein adsorption, and TPSLEQRTVYAK (TPS) peptide, which can specifically bind endothelial progenitor cells (EPCs), were immobilized on the PCL surface through host-guest inclusion complexation. The chemical composition as well as the hydrophilic/hydrophobic property of the functionalized surface was characterized by X-ray photoelectron spectroscopy and water contact angle measurements. The relative composition of two functional molecules on the dually functionalized surface was further analyzed by fluorescence quantification. Finally, the fibrinogen adsorption, platelet adhesion and activation, and selective attachment of cells were systematically evaluated on the functionalized surface. The results show that the presence of PEG evidently inhibited the adsorption of plasma protein and platelet adhesion, thus reducing the possibility of thrombus formation on the functionalized surface. At the same time, the TPS-functionalized surface demonstrated enhanced attachment toward EPC compared with the surfaces in the absence of TPS functionalization. For the surface functionalized by both PEG and TPS, the functions provided by each component have been well demonstrated. The relative composition of the PEG and TPS could be further fine-tuned by adjusting the feeding ratio. All these results indicate that the dually functionalized surface developed in this study is a suitable candidate for vascular graft to induce and promote in situ endothelialization.

Functionalization of the surface of electrospun poly(epsilon-caprolactone) mats using zwitterionic poly(carboxybetaine methacrylate) and cell-specific peptide for endothelial progenitor cells capture.

A novel approach for vascular grafts to achieve rapid endothelialization is to attract endothelial progenitor cells (EPCs) from peripheral blood onto grafts via EPC-specific antibodies, aptamer, or peptides that specifically bind to EPCs. Inspired by this idea, the electrospun poly(epsilon-caprolactone) (PCL) mats were modified with zwitterionic poly(carboxybetaine methacrylate) (PCBMA) and phage display-selected-EPC-specific peptide, TPSLEQRTVYAK (TPS). We tested the physical and chemical properties, cyto-compatibility, and platelet adhesion of the modified material, and investigated the specificity of the functionalized surface for capturing EPCs. The results indicated that PCL modified with zwitterionic PCBMA and TPS peptide showed improved hydrophilicity without morphology change and damage of the mats. Furthermore, the modified material supported adherence and growth of vascular cells and resisted platelets adhesion. The surfaces also specifically captured EPCs rather than bone marrow mesenchymal stem cells and human umbilical vein endothelial cells. This surface-functionalized PCL graft may offer new opportunities for designing new vascular grafts.

The potential role of local voltage potentials in right ventricular outflow tract arrhythmias: 47 cases with ventricular arrhythmias originating from right ventricular outflow tract.

OBJECTIVE: The object of this study was to investigate the possible role of local voltage potentials (LVPs) in mapping the ventricular arrhythmias originating from right ventricular outflow (RVOT). METHODS: Forty-seven patients with RVOT VAs (ventricular arrhythmias), referred for radiofrequency catheter ablation to our hospital, were analysed retrospectively for the prevalence, characteristics and electrophysiological evaluation of the LVPs recorded in successful and unsuccessful ablation sites. RESULTS: Radiofrequency ablation was successful immediately in all the 47 cases. Catheter ablation was performed at a mean of 8 +/- 6 sites per patient. There were 58 effective ablation sites, 5 cases with changing morphology of ventricular arrhythmias (VAs), and 318 invalid ablation sites. Activation times at effective ablation sites were slightly earlierthan those at invalid ablation sites (-28 +/- 8 ms vs-24 +/- 7 ms, P < 0.05). The LVPs appeared during VAs in 47 sites of the 58 effective ablation sites (81.0%), far more than the 22 sites of the 318 invalid ablation sites (6.9%) (P < 0.01). In two cases VAs recurred during follow-up. They received a second catheter ablation. CONCLUSIONS: Local ventricular potentials can be recorded in most patients with idiopathic VAs originating from the right outflow tract.The local potentials may facilitate successful radiofrequency ablation.

Poly(ε-caprolactone) modified with fusion protein containing self-assembled hydrophobin and functional peptide for selective capture of human blood outgrowth endothelial cells.

Human blood outgrowth endothelial cells (HBOECs)-specific binding peptide, TPSLEQRTVYAK (TPS), was proposed to be applied on autologous cell therapy for treating cardiovascular diseases. Hydrophobins, as a family of self-assembly proteins originated from fungi, have demonstrated unique characteristics to modulate surface properties of other materials coated with these amphiphilic proteins in previous studies. In this report, a fusion protein which was composed of class I hydrophobin HGFI originated from Grifola frondosa and functional peptide TPS was expressed by Pichia pastoris expression system. Then, we purified this fusion protein by ultrafiltration and reverse-phase high performance liquid chromatography. Water contact angle, X-ray photoelectron spectroscopy measurements indicated that the surface properties of hydrophobin were greatly preserved by this fusion protein while comparing with wild HGFI. Cell binding assay showed that this fusion protein demonstrated specific binding property to HBOECs while coating on biodegradable poly(ε-caprolactone) (PCL) grafts in the presence of fetal bovine serum, whereas HGFI-coated PCL non-selectively enhanced all types of cells attachments. Methylthiazol tetrazolium assay was employed to verify the cytocompatibility of this fusion protein-based material. This work presented a new perspective to apply hydrophobin in tissue engineering and regenerative medicine and provided an alternative approach to study endothelial progenitor cells.

Biodegradable polymer-curcumin conjugate micelles enhance the loading and delivery of low-potency curcumin.

PURPOSE: To utilize a novel type of polymer-drug conjugate micelle to enhance the delivery of low-potency curcumin. METHODS: Multiple curcumin molecules were conjugated to poly(lactic acid) (PLA) via tris(hydroxymethyl)aminomethane (Tris) linker producing the hydrophobic drug-binding block; methoxy-poly(ethylene glycol) (mPEG) was employed as the hydrophilic block. Micelles were characterized by size, loading capacity, stability, and critical micelle concentration (CMC). Human hepatocellular carcinoma (HepG2) cells were employed to assess cytotoxicity and intracellular targeting ability of micelles. RESULTS: mPEG-PLA-Tris-Cur micelles were within nanorange (<100 nm). CMC of such micelles (2.3 ± 0.4 µg/mL) was 10 times lower than mPEG-PLA micelles (27.4 ± 0.8 µg/mL). Curcumin loading in mPEG-PLA-Tris-Cur micelles reached 18.5 ± 1.3% (w/w), compared to traditional mPEG-PLA micelles at 3.6 ± 0.4% (w/w). IC(50) of mPEG-PLA-Tris-Cur micelles (~22 µg/mL at curcumin-equivalent dose) was similar to unmodified curcumin. Placebo and drug-encapsulated conjugate micelles could be efficiently internalized to cytoplasmic compartment of HepG2 cells. CONCLUSIONS: Micelle-forming polymer-drug conjugates containing multiple drug molecules were an efficient means to increase loading and intracellular delivery of low-potency curcumin.

Expression and characterization of hydrophobin HGFI fused with the cell-specific peptide TPS in Pichia pastoris.

The cell-specific peptide TPS (TPSLEQRTVYAK) has been proposed as a potential candidate for fabricating tissue engineering scaffolds based on its ability of binding to human endothelial progenitor cells (EPC) with high affinity and specificity. In this study, the class I hydrophobin hgfI gene from Grifola frondosa and the tps were fused and cloned into pPIC9. The fusion gene was expressed in Pichia pastoris under the control of alcohol oxidase 1 promoter. Tricine-SDS-PAGE and Western blotting confirmed that the fusion protein TPS-linker-HGFI (TLH) was successfully secreted into the culture medium. The fusion protein TLH was purified by ultrafiltration and reverse-phase high performance liquid chromatography (RP-HPLC). Water contact angle (WCA) demonstrated that similar to recombinant HGFI (rHGFI), the purified TLH could convert the surface wettability of polystyrene and mica. X-ray photoelectron spectroscopy (XPS) measurements indicated that the purified TLH could form stable films on the hydrophobic siliconized glass surface. The cell adhesion examination showed that the TLH modified poly(ε-caprolactone) (PCL) could specially facilitate the EPC (particularly EPC derived from human) binding, while rHGFI modified PCL could nonselectively enhance cells adhesion. To the best of our knowledge, this is the first report that demonstrates that the TPS peptide was immobilized on biomaterial-PCL surface by fusion with hydrophobin. The potential application of this finding in combination with biomedical devices for EPC culture, will facilitate the current techniques used for cell-based therapies.

Development of a recombinant ureolytic Lactococcus lactis for urea removal.

Kidney failure is a common disease with high frequency. Food-grade recombinant bacteria that can effectively remove urea has great potential for treatment of renal failure. A nonpathogenic strain, L. lactis MG1363, was transformed with plasmid pMG36eure, which carries urease gene. The expression of transgene urease in genetically modified L. lactis MG1363 and the urease activity in removal of urea were investigated. It was found that the removal of urea by recombinant L. lactis MG1363 was pH- and nickel-dependent. At pH 6.5 and in the presence of 250 microM of NiSO4, 50 approximately 60% of urea could be removed in 24 hours. The urea removal activity was also evaluated in imitative gastroenteric environment. After being exposed to acidic solution (pH2.5-4.0) for 2 hours, the cells were then grown in a medium containing 0.1 cfu/ml bile acid salt, 30 mg/dl urea, and 250 microM NiSO4 at pH 6.8. The concentration of urea decreased over time, and the removal was about 30% at 10 hours and 65% at 24 hours, respectively. The safety tests were performed by feeding normal rats with either L. lactis MG1363 or recombinant L. lactis MG1363. The two materials did not cause any changes in blood cells and blood biochemical indexes. There were no differences in terms of body weight and water/food consumption between the two materials. These results indicate the safety, feasibility, and capacity of urease gene modified Lactococcus Lactis in removal of urea under the gastroenteric circumstances. Further investigation may generate a food-grade strain for treatment of chronic renal failure.