Induction of cell self-organization on weakly positively charged surfaces prepared by the deposition of polyion complex nanoparticles of thermoresponsive, zwitterionic copolymers.

We have developed inducible cell self-organization through weakly positively charged culture surfaces. In this study, a thermoresponsive and zwitterionic copolymer comprised of N,N-dimethylaminoethyl methacrylate (DMAEMA) and methacrylic acid (MA) (PDMAEMA-co-PMA; Mn: ∼9.7 × 104 g/mol; PDMAEMA/PMA ratio: 10) was designed for inducing cell self-organization. The copolymer formed single polymer-derived polyion complex (sPIC) nanoparticles following dissolution in an aqueous solution. The sPIC nanoparticles had a positive charge (ca. 25 mV). Self-organization occurred in adipose-derived vascular stromal cell monolayers cultivated on sPIC-deposited surfaces. There were dramatic morphological changes of these cells with the formation of capillary-like networks and single-cell aggregates with little cytotoxicity. This was a significant improvement compared with cells grown on previously developed surfaces deposited with PIC, a mixture of PDMAEMA and plasmid DNA. Thus, sPICs of PDMAEMA-co-PMA may allow for the accurate evaluation of a variety of cell behaviors with less cytotoxicity, and may facilitate additional potential medical applications such as cell-based therapy and drug discovery. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1009-1015, 2017.

Preparation and characterization of directed, one-day-self-assembled millimeter-size spheroids of adipose-derived mesenchymal stem cells.

Three-dimensional cell spheroids prepared without using any artificial scaffold materials are desirable for cell-based transplants. However, conventional cell culture systems are inefficient for rapid, large-scale and non-cytotoxic generation of size-controlled spheroids (>1 mm diameter) that are required for tissue regenerative therapy application. In this study, we prepared millimeter-order spheroids of adipose-derived mesenchymal stem cells (ADSCs) by controlling the spheroid size (diameter range: 0.4-2.5 mm). Notably, spheroid generation required only one day of culture on charged culture dishes. Almost all spheroid-derived ADSCs were viable and produced adhesion molecules and growth factors, which play an important role in tissue regeneration. Moreover, spheroid-derived ADSCs could infiltrate and recellularize collagenous tissue membranes in vitro. The ADSC spheroids developed in this study could be directly (without additional processing) used for cell-based tissue regeneration therapy. Furthermore, the rapid scale-up process and noncytotoxic generation of spheroids would also enable other applications such as use as screening models for drug discovery.

The effect of electrically charged polyion complex nanoparticle-coated surfaces on adipose-derived stromal progenitor cell behaviour.

Surface characteristics of biomaterials such as wettability, rigidity, roughness, and electrical charge affect the fate of transplanted cells such as progenitor cells or stem cells for use in regenerative medicine. Of these, the effects of surface electrical charges on cellular behaviour such as adhesion, proliferation, and differentiation are not well understood. We prepared precisely charged culture surfaces ranging from -28 mV to +21 mV, simply by surface deposition of polyion complex nanoparticles prepared by mixing a positively charged thermoresponsive homopolymer, poly(N,N-dimethylaminoethyl methacrylate), with negatively charged plasmid DNA at various charge ratios. Drastic morphological changes of adipose-derived vascular progenitor cells were generated on the positively charged surface of organized forms at +19 mV. Capillary-like networks or single aggregates of these cells were selectively created depending on cell seeding density. Our findings offer new insights that may aid develop stem cell-processing techniques for use in regenerative medicine.

Enhanced transfection efficiency of poly(N,N-dimethylaminoethyl methacrylate)-based deposition transfection by combination with tris(hydroxymethyl)aminomethane.

We have developed a substrate-mediated transfection method called "deposition transfection technology" using a poly(N,N-dimethylaminoethylmethacrylate) (PDMAEMA) homopolymer with both thermoresponsive and cationic characteristics. In this study, we enhanced deposition transfection efficiency by using tris(hydroxymethyl)aminomethane (Tris buffer) as a pH adjuster for transfection solution composed of PDMAEMA and plasmid DNA (pDNA). PDMAEMA with a molecular weight of 9.7 × 10(4) g mol(-1) was synthesized by photoinduced radical polymerization. The pH of PDMAEMA solution was increased gradually in the range from 8 to 11 by the addition of Tris, and then the solubility of PDMAEMA was significantly decreased and the dissolution time was extended from 15 to 40 min at Tris/PDMAEMA ratio of 1 and higher. On the other hand, while the polyion complexes (polyplexes) were formed by mixing PDMAEMA with luciferase-encoding plasmid DNA even under an excess amount of Tris at Tris/PDMAEMA ratio of 8, the binding affinity between PDMAEMA and pDNA was decreased with increasing Tris at Tris/PDMAEMA ratio of 2 and higher. When HeLa cells, smooth muscle cells, and cardiac fibroblasts were transfected by the deposition method using polyplex solution containing various amounts of Tris, the transgene expression dramatically increased at a Tris/PDMAEMA ratio of 2 in all cell types, which were more than 150-fold in HeLa cells, 40-fold in smooth muscle cells, and 30-fold in cardiac fibroblasts compared to those in the Tris-free condition. In addition, the enhanced transgene expression by Tris was sustained for over 10 days post-transfection as well as that observed in Tris-free condition. Thus, deposition transfection efficiency can be dramatically enhanced by using Tris buffer as a pH adjuster for polyplex solution.

Deposition gene transfection using bioconjugates of DNA and thermoresponsive cationic homopolymer.

A poly(N,N-dimethylaminoethylmethacrylate) (PDMAEMA) homopolymer with both thermoresponsive and cationic characteristics was applied to a vector for use in deposition transfection. PDMAEMA with a molecular weight of 2.5 × 10(5) g mol(-1) was synthesized by photoinduced radical polymerization. Polyplexes approximately 750 nm in size were formed by mixing PDMAEMA with luciferase-encoding plasmid DNA. The polyplexes had a lower critical solution temperature (LCST) of approximately 30 °C. In addition, they exhibited excellent adsorption and durability on a polystyrene surface, as confirmed by a surface chemical compositional analysis. When HeLa cells and primary cells were cultured on a substrate coated with the polyplexes, high transgene expression and cell viability of more than 90% were obtained at low charge ratios (PDMAEMA/plasmid DNA ratio) ranging from 2 to 8. In addition, transgene expression was sustained for over 2 weeks post-transfection whereas decreased expression was observed 5 days post-transfection when the conventional solution-mediated transfection method was used. Thus, high and sustained transgene expression as well as high cell viability can be realized by using small amounts of PDMAEMA as a deposition transfection material.

[Survey on the actual condition of psychiatrists and psychiatric services in Japan. (Part 1): Basic data on number and distribution of psychiatrists].

BACKGROUND: To ensure that psychiatric services adequately meet the needs of the Japanese people, planning a prospective design based on a needs analysis is required. Presently, the distribution of medical resources in Japan is skewed and the priorities of psychiatric services are unclear. OBJECTIVE: To determine the current status of psychiatric services. METHOD: The definition of a psychiatrist was determined by qualified specialists of the Japanese Society for Psychiatry and Neurology (JSPN). Of the 11,169 candidates who applied for the specialist psychiatry examination, 246 were excluded due to a lack of personal information and 4 due to refusal. The remaining 10,919 agreed to allow the verification of their personal data. This study was conducted with the approval of the JSPN. The total number of psychiatrists, their demographic backgrounds, the number of psychiatrists by prefecture, and the number of psychiatrists in each secondary medical care block in Japan were calculated. RESULTS: Of the 10,919 psychiatrists included in this analysis, 2,124 were female and 8,790 were male. Approximately 90% were < 65 years old, and 42% were < 45 years old. Their primary work places were as follows: psychiatric hospitals (n = 5,233, 47.9%); university departments of psychiatry (n=1,353, 12.4%); general hospitals (n = 1,064, 9.7%); psychiatric clinics (n = 2,456, 22.5%); nonpsychiatric clinics (n = 687, 6.3%); and nonclinical work places such as basic science departments (n = 124, 1.1%). The number of psychiatrists per 100,000 inhabitants in each prefecture was determined. The highest numbers of psychiatrists were from Kochi (13.20), Tokyo (12.76), and Tokushima (12.24), and the lowest numbers were from Ibaraki (5.34), Aomori (5.36), and Saitama (5.67). The number of psychiatrists per 100,000 inhabitants in Kochi was 1.48 per area (100 km square), and Tokyo showed the highest at 75.99 psychiatrists per area, followed by Osaka and Kanagawa. The five Tohoku prefectures and Hokkaido had the fewest psychiatrists per area. CONCLUSION: For planning the future management of psychiatric services, continuous investigation of the actual number of psychiatrists and the status of psychiatric services in Japan is required with the constant cooperation of the JSPN.

[Survey on the actual condition of psychiatrists and psychiatric services in Japan. (Part 2): Change in geographical working area and setting of each psychiatrist].

BACKGROUND: The shortage of psychiatrists has recently become a public concern; however, the reason for this shortage has not been clearly discussed or explained on the basis of real data. We assumed that it is not only due to the lack of the absolute number of psychiatrists, but also due to an imbalance in their distribution in geographical working areas and settings. OBJECTIVE: To evaluate the change in distribution of Japanese psychiatrists. METHOD: We analyzed the change in the geographical working area and setting of each psychiatrist from September 2006 to March 2009 using data obtained from psychiatrists who applied for the Board Certification Examination of the Japanese Psychiatric Association. Our data included 6,881 psychiatrists. RESULTS: With regard to the geographical working area, the number of psychiatrists in ordinance-designated cities (urban areas) increased by 2.2%, whereas that in other areas decreased by 3.0%. On examination of work settings, we noted a 16.0% decrease in the number of psychiatric departments in general hospitals and a 20.0% increase in the number of psychiatric clinics. Surprisingly, more than 10% of middle-aged psychiatrists (10.3% of 36 45-year-olds and 12.2% of 46-55-year olds) who worked in general hospitals moved to clinics. CONCLUSION: The present study revealed that, although psychiatrists did not tend to move from rural to urban areas, they showed a tendency to move from general hospitals to psychiatric clinics.

Thermoresponsive heparin bioconjugate as novel aqueous antithrombogenic coating material.

A novel thermoresponsive aqueous antithrombogenic coating material comprising a heparin bioconjugate with a six-branched, star-shaped poly(2-(dimethylaminoethyl)methacrylate) (6B-PDMAEMA), which has both thermoresponsive and cationic characters, was developed to reduce the thrombogenic potential of blood-contacting materials such as synthetic polymers or tissue-engineered tissues in cardiovascular devices. 6B-PDMAEMA with M(n) of ca. 24 kDa was designed as a prototype compound by initiator-transfer agent-terminator (iniferter)-based living radical photopolymerization from hexakis(N,N-diethyldithiocarbamylmethyl)benzene. Bioconjugation of heparin with 6B-PDMAEMA occurred as soon as both aqueous solutions were simply mixed to form particles. The particle size at 25 °C was less than several hundred nanometers in diameter under a heparin/6B-PDMAEMA mixing weight ratio of over 2.5. The particles were very stable because of the prevention of hydrolysis of 6B-PDMAEMA in its bioconjugated form. Because the lower critical solution temperature of the bioconjugate ranges from approximately 20 to 36 °C for the formation of microparticles, the coating could be done in an aqueous solution at low temperatures. The excellent adsorptivity and high durability of the coating above 37 °C was demonstrated on silicone and polyethylene films by surface chemical compositional analysis. Blood coagulation was significantly reduced on the bioconjugate-coated surfaces. Therefore, the thermoresponsive bioconjugate developed here appears to satisfy the initial requirements for a biocompatible aqueous coating material.

Impact of molecular weight in four-branched star vectors with narrow molecular weight distribution on gene delivery efficiency.

A series of star-shaped cationic polymers, termed star vectors (SVs), has been developed as effective nonviral gene delivery carriers. In this study, we separated SVs into several fractions having different molecular weights with very narrow molecular weight distributions in order to examine in detail the influence of the molecular weight of the SVs on the gene transfection efficiency. As a model compound for several types of SVs, 4-branched poly(N,N-dimethylaminopropyl acrylamide) having a molecular weight (M(n)) of approximately 35 kDa and polydispersity of 1.6 was prepared by iniferter-based radical polymerization. The SVs were separated using size-exclusion chromatography to obtain seven fractions having M(n) ranging from 27 kDa to 73 kDa with polydispersity ranging from 1.1 to 1.2. All the fractionated SVs have similar pH of 10.2-10.4 and were able to interact with and condense luciferase-encoding plasmid deoxyribonucleic acid (DNA) to yield SV/DNA polyplexes. A water-soluble tetrazolium-1 (WST) assay showed that all SVs had minimal cellular cytotoxicity under an N/P charge ratio of 10. The critical micellar concentration decreased with an increase in the M(n) of the fractionated SVs; however, the particle size of the polyplexes, exclusion activity of ethidium bromide, and zeta-potential of the polyplexes increased. An in vitro evaluation using COS-1 cells at an N/P ratio of 10 showed that transfection activity increased almost linearly with M(n). The highest transfection activity was obtained for SVs with the highest M(n) (73 kDa), which was over 7 times that for the SVs with the lowest M(n) (27 kDa), the nonfractionated original SV, or PEI standard. The transfection efficiency was more correlated with the amphiphilicity or hydrophobicity of the SVs and the surface potential and condensate density of the polyplexes than with the particle size.

An animal study of a newly developed skin-penetrating pad and covering material for catheters to prevent exit-site infection in continuous ambulatory peritoneal dialysis.

Because currently available peritoneal dialysis catheters are not sufficiently biocompatible with the skin and subcutaneous tissue at the site of penetration, exit-site infection due to pericatheter pocket formation caused by epidermal downgrowth over a long period of time has increasingly become a problem. We developed a new, biocompatible, segmented polyurethane porous material and devised a novel skin-penetrating pad, the form and material of which we optimized for application in peritoneal dialysis catheters. For the extent of tissue ingrowth into this porous material to be examined, test materials with different pore diameters were inserted into hollow silicone tubes and implanted in the subcutaneous tissue of a goat. Four weeks later, the tubes were extracted, and, after the extent of granulation tissue ingrowth was measured, histopathological evaluation was made. Our novel skin-penetrating pad has three disklike layers of the segmented polyurethane material with different pore sizes, into the center of which a polyurethane catheter is inserted. These pads were implanted in the skin of a goat and clinically observed over a 2-year period, after which they were extracted and histopathologically analyzed. In accordance with actual clinical procedures, a commercial CAPD catheter equipped with our skin-penetrating pad was left indwelling in a goat for 4 months, and the performance of the pad was evaluated after repeated periodic infusion and drainage of the dialysate in and out of the abdominal cavity. There was no inflammation of the ingrown tissue in the pores of the segmented polyurethane material as well as the surrounding tissue, which indicated favorable tissue biocompatibility. The extent of tissue ingrowth was greater as the pore size of the material was larger, and the tissue tended to be mature, mainly consisting of collagenous fibers. The skin-penetrating pad using the porous material, of which tissue ingrowth was thus optimized, tightly adhered to the goat skin throughout the 2-year experimental period without any special wound care such as cleansing or disinfection. The performance of the skin-penetrating pad was similarly favorable when attached to a commercial continuous ambulatory peritoneal dialysis catheter. The newly developed segmented polyurethane porous material had excellent tissue biocompatibility and tissue ingrowth. The skin-penetrating pad devised by using this porous material did not cause epidermal downgrowth, suggesting that it may be effective for the prevention of exit-site infection.

Development of a novel nonviral gene silencing system that is effective both in vitro and in vivo by using a star-shaped block copolymer (star vector).

The objective of our study was to develop a novel nonviral gene silencing system using small interfering RNA (siRNA) or short hairpin RNA (shRNA) complexes using star vector (SV), which is a star-shaped, four-branched, cationic-nonionic-blocked copolymer, as the water-soluble delivery system. This vector was previously designed as a carrier for high-efficiency gene delivery of plasmid DNA. The lamin gene was used as the target for developing siRNAs. SV was shown to condense and interact with siRNAs to yield SV/siRNA polyion complexes with a diameter of ca. 90 nm and having considerable stability. By using these complexes, siRNA was successfully delivered to almost all human hepatocellular carcinoma cells used in this study, and both siRNAs and shRNAs could produce significant gene silencing in these cells without affecting cell viability. The silencing efficacy of these complexes was similar to that of commercially available high-efficiency siRNA transfection reagent (Darmafect-4). After injecting SV/siRNA complexes into mice, effective gene silencing was also observed in vivo in the liver and lung, suggesting that the SV/siRNA complexes were stable under in vivo conditions, and their transfection efficiency was retained after intravenous administration. Thus, SV was a potential carrier for siRNA and shRNA delivery in both in vitro and in vivo conditions; this finding suggests that it may offer a new clinical therapeutic approach in gene therapy.

Photoinduced cross-linking of star vector for improvement of gene transfer efficiency.

This study aimed to investigate the effect of cross-linking of a cationic nonviral gene carrier on gene expression. As a precursor for photo-cross-linking, a star-shaped, six-branched cationic polymer of poly(N,N-dimethylaminopropylacrylamide) (six-branched star vector, SV), which was previously designed as a gene carrier, was synthesized by iniferter-based living radical polymerization. Upon UV irradiation, the number-average molecular weight (Mn) of the SV increased from ca. 28 kDa to ca. 32 kDa (irradiation time, 180 min) and ca. 46 kDa (240 min) with broadness of the polydispersity due to the coupling reaction between the polymer radicals generated at the terminal ends of each branch of the SVs, resulting in the preparation of cross-linked SVs (CSVs) without the use of any chemical cross-linking agents. Irrespective of cross-linking, all the SVs were able to interact with and condense luciferase-encoding plasmid DNA to yield relatively stable polymer/DNA complexes (polyplexes) of approximate diameter 150 nm with zeta-potential of ca. 20 mV. However, a transfection study using several types of cell lines, HeLa, Hep G2, 293, and COS-1, showed that by cross-linking of SVs the luciferase activity increased drastically. The activity with CSV (Mn=ca. 46 kDa) was increased by at least 1 order of magnitude in the original SV (Mn=ca. 28 kDa), which was several-fold that in the SV with the same molecular weight in all cells. In all SVs, no significant cellular cytotoxicity was observed even at a high charge ratio of 45. The SV-based gene transfection was significantly enhanced by the cross-linking of the SVs.

Synthesis and in vitro evaluation of novel star-shaped block copolymers (blocked star vectors) for efficient gene delivery.

Novel 4-branched diblock copolymers consisting of cationic chains as an inner domain and nonionic chains as an outer domain were prepared by iniferter-based living radial polymerization and evaluated as a polymeric transfectant. The cationic polymerization of 3-(N,N-dimethylamino)propyl acrylamide (DMAPAAm) using 1,2,4,5-tetrakis( N,N-diethyldithiocarbamylmethyl)benzene as a 4-functional iniferter followed by the nonionic block polymerization of N,N-dimethylacrylamide (DMAAm) afforded 4-branched diblock copolymers with controlled compositions. By changing the solution or irradiation conditions, 4-branched PDMAPAAms with molecular weights of 10,000, 20,000, and 50,000 were synthesized. In addition, by graft polymerization, PDMAPAAm-PDMAAm blocked copolymers with copolymer composition (unit ratio of DMAAm/DMAPAAm) ranging from 0.18 to 1.0 for each cationic polymer were synthesized. All polymers were shown to interact with and condense plasmid DNA to yield polymer/DNA complexes (polyplexes). A transfection study on COS-1 cells showed that the polyplexes from block copolymers with cationic chain length of approximately 50,000 and a nonionic chain length of 30,000, which were approximately 200 nm in diameter and very stable in aqueous media, had the most efficient luciferase activity with minimal cellular cytotoxicity under a charge ratio of 20 (vector/pDNA). The PDMAPAAm-PDMAAm-blocked, star-shaped polymers are an attractive novel class of nonviral gene delivery systems.

Deposition transfection technology using a DNA complex with a thermoresponsive cationic star polymer.

A novel non-viral gene transfection method in which DNA complexes were kept in contact with a deposition surface (deposition transfection) was developed. We designed a novel aqueous thermoresponsive adsorbent material for DNA deposition, which was a star-shaped copolymer with 4-branched chains. Each chain is comprised of a cationic poly(N,N-dimethylaminopropyl acrylamide) (PDMAPAAm) block (Mn: ca. 3000 g x mol(-1)), which formed an inner domain for DNA binding and a thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) block (Mn: ca. 6000 g x mol(-1)), which formed an outer domain for surface adsorption. Complex formation between the copolymer and the luciferase-encoding plasmid DNA occurred immediately upon simple mixing in an aqueous medium; polyplexes approximately 100 nm in size were formed. Because the lower critical solution temperature of the polyplexes was approximately 35 degrees C, they could deposit on the substrate by precipitation from an aqueous solution upon warming, which was confirmed by quartz crystal microbalance (QCM) method and water contact angle measurement. When COS-1 cells were cultured on the polyplex-deposited substrate in a culture medium, the luciferase activity observed was higher than that observed on a DNA-coated substrate with or without the cationic polymer before and after complete adhesion and by conventional solution transfection using the polyplexes. The activity was enhanced with an increase in the charge ratio (surfactant/pDNA) with permissible cellular cytotoxicity.

Differentiation from embryonic stem cells to vascular wall cells under in vitro pulsatile flow loading.

This study evaluated the possibility of differentiation from embryonic stem (ES) cells to vascular wall cells by physical (mechanical) stress loading in vitro. A cell mixture containing Flk1-positive cells (ca. 30%) derived from murine ES cells was added to a compliant microporous tube made of segmented polyurethane. The compliance of the tube was close to that of the human artery [the stiffness parameter (beta) = 57.2 (n = 5, SD < 5%)]. The luminal surface of the tube was fully covered with the cells by preincubation for two days in the presence of vascular endothelial growth factor (VEGF). After 2 days of additional incubation without VEGF under static conditions, layering of the grown cells, mostly smooth muscle actin (SMA)-positive cells, was observed only on the luminal surface of the tube. The cells were flat, polygonal, and randomly oriented. On the other hand, after a 2-day incubation under a weak pulsatile flow simulating the human venous systems [wall shear stress (WSS) from -0.98 to 2.2 dyn/cm(2); circumferential strain (CS) 4.6-9.6 x 10(4) dyn/cm(2)] without VEGF, cells in the superficial layer were regularly oriented in the direction of the pulsatile flow. The oriented cells exhibited endothelial-like appearance, indicating that they were platelet endothelial cell adhesion molecule 1 (PECAM1)-positive. In addition, the cells growing into the interstices in the deeper layer showed smooth muscle-like appearance, indicating that they were SMA-positive. Differentiation to two different cell types and segregation of incorporated ES cells may be simultaneously encouraged by the combination of WSS and CS. It is expected that the monobloc building of hierarchically structured hybrid vascular prostheses composed of several vascular wall cell types is possible by physically synchronized differentiation of ES cells.

Development of sutureless vascular connecting system for easy implantation of small-caliber artificial grafts.

A novel sutureless vascular connecting system, an assembly with a delivery rod, an introducing sheath, and a connecting device, was developed for easy implantation of small-caliber vascular grafts less than 2 mm in internal diameter. A microporous stainless tube (length 2 mm, external diameter 1.6 mm, wall thickness 65 microm, pore diameter 400 microm, pore-to-pore distance 500 microm) was designed to serve as a connecting device. The feasibility of the system was tested using two types of preliminary animal experiments. One animal model consisted of graft implantation into the rat abdominal aorta (1.5 mm in diameter). The connecting device was inserted into the proximal and distal ends of the aorta through the introducing sheath by pushing the delivery rod with the connecting device placed over it. Subsequently, the aortic segments were inserted into both ends of model grafts made of segmented polyurethane (1.8 mm in internal diameter) and were fixed with banding silk threads from the exterior. The procedure was completed within 20 min without requiring specialized microsurgery techniques. Blood leakage and obstruction did not occur. The second model consisted of an end-to-end anastomosis between rabbit common carotid arteries (2 mm in diameter), which was performed within several minutes of blood flow interruption. Scanning electron microscopy demonstrated that the luminal surface of the device was fully covered with endothelial cells (ECs) after 1 week as a result of transluminal ingrowth of native ECs through the micropores in the device. This endothelialization may prevent early thrombus-induced occlusion. This simple and "easy-to-learn" technique will promote the development of small-caliber arterial grafts, and furthermore, it may have potential for clinical application.