Myocardial infarction is one of the most common heart diseases which are irreversible leading to progressive heart failure, mainly because cardiomyocytes possess limited intrinsic regenerative capability to replace the lost cells. Stem cells can be driven to differentiate into cardiomyogenic lineages and an understanding on the various strategies and mechanisms for cardiomyogenic differentiation is essential for evaluations of myocardial regeneration and recovery of heart function. Various strategies, both in vitro and in vivo, have been applied to stem cells for cardiomyogenic differentiation including molecular treatments, culture medium mediation, and chemical or physical stimulations. In this review, we discuss various strategies and mechanisms of five types of stem cells (mesenchymal stem cells, haematopoietic stem cells, adipose-derived stem cells, embryonic stem cells, induced pluripotent stem cells) differentiating to cardiomyocytes, and the fabrication of bio-nanomaterials such as conductive polymers and injectables as cardiac tissue engineering substrates, as well as the potential techniques like electrical stimulation and bioreactors used to direct and control the cardiomyogenic differentiation of stem cells.

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The purpose of this study was to clarify whether the short glass fibers of CaO-P₂O₅-SiO₂-Al₂O₃ (CPSA) glass possessed the ability to reinforce conventional glass-ionomer cement (GIC). Biocompatibility of the set GIC mixed with short CPSA glass fibers was evaluated in a cell culture cytotoxicity test. Moreover, the rate of release fluoride ions from GIC mixed with short glass fibers was measured. The powder of a conventional GIC was mixed with short CPSA glass fibers (diameter, 9.7±2.1 μm; aspect ratio, 5.0±0.9) before mixing with the liquid of the GIC. Set cements of 40 mass% short CPSA glass fibers mixed with GIC powders showed maximum values of 18 MPa in diametral tensile strength (DTS) after aging for 24 hours due to the effects of specific shape of short glass fibers and reactivity between the mixing liquid and short glass fibers. The cytotoxicity of these cements to rat pulpal cells tested by cellular activity showed that the set GIC disks (13 mm in dia. × 1 mm in thickness) with 40 mass% short CPSA glass fibers had cell activity as that of the set GIC or a cell culture coverslip used as control. Moreover, the addition of short glass fibers to GIC did not disturb the release of fluoride from the specimens.

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The application of zirconia ceramics for the dental restorations and dental implants has increased. However the weak performance of the veneering porcelains and low adhesion to the zirconia framework were reported. In this study, the micro-structure, elemental distribution and crystal phase around the interface between zirconia and veneering porcelain were estimated using SEM-EDS (energy dispersed spectrometry) and micro-XRD (X-ray diffraction). The specimen fired at 940^oC for 1 minute showed clear interface in the SEM and the elemental distribution images of Zr and Si. With extending firing period up to 384 hours, slight diffusions of Zr and Si, which are the major components of zirconia and porcelain ware suggested. In micro-XRD, no phase transformation was observed in the zirconia and porcelain, thus extension of firing period would not affect the crystal phase around the zirconia/porcelain interface. Therefore, the extension of firing period was expected to slightly improve the zirconia/porcelain bonding.

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Biomaterials made using hydroxyapatite (HAp) and calcium phosphates, which are inorganic components of hard tissues, have been developed to fill bone defects caused by various diseases. A biomaterial of HAp containing collagen, an organic component of bone, has also been developed. However, the physical and biological functions of these bone biomaterials remain inadequate.
Focusing on Zinc(Zn) and Manganese(Mn) ions out of the divalent cations involved in the activity of integrins, which are molecules existing in cell membranes, we synthesized three kinds of inorganic biomaterials—pure HAp, Zn-containing HAp (Zn-HAp), and Mn-containing HAp (Mn-HAp)—by a wet process. These three kinds of HAp powders were formed into pellets of 6mm diameter and 1mm thickness and their bio-adaptability was investigated.
In vitro experiments using osteoblast-like cells (MC3T3E1) demonstrated that Mn-HAp showed higher cell adhesion potential than pure HAp, indicating that Mn addition improves bioresponses. This may be because Mn ions eluted from Mn-HAp pellets activated integrins, which are closely related to the cell adhesion potential of MC3T3E1 cells to the surface of the pellets.

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We examined the influence of culture methods with mono- and multilayer nanocarbon tubes (SWCNT and MWCNT, respectively) on the differentiation of mouse embryonic stem (ES) cells using a cellular differentiation technique for the embryonic stem cell test (EST). On differentiation assay, beating was noted in 72, 35, and 60% of the cells in the control, SWCNT, and MWCNT groups, respectively. In addition, there was no influence on cytotoxicity based on the LDH level. In this study, the MWCNT did not influence the differentiation of ES cells, but the SWCNT markedly inhibited it, confirming that the differentiation of ES cells depends on the material surface structure.

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We evaluated the in vitro influences of two types of ultrafine titanium dioxide differing in surface treatment and ultrafine zinc oxide on the area rate and length of tubule-like structures using a human angiogenesis kit. In addition, the influences of titanium and zinc oxide ions were evaluated. A comparison of influences on tubule-like structures between the two surface treatment methods of ultrafine titanium dioxide showed only slight influences of surface treatment providing water-repellency. Using ultrafine zinc oxide, no tubule-like structure formation was observed. The area rate of tubule-like structures was 84.0% for titanium ions and 78.3% for zinc ions at a concentration of 2.5 ppm, but this rapidly decreased with an increase in the ion concentration. These results may differ from those obtained in the nanoparticle dispersion state. It is possible that in vivo biological influences also differ between aggregation and dispersion states. Further studies based on the in vivo dispersion state are necessary.

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