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Hydroxyapatite (HA) has been widely used to produce biomaterials. We reported that electrically polarized HA (pHA) induces cells as a scaffold. Recently, in the biomedical field, many studies are underway, seeking new applications of silk fibroin (SF), because SF can be gelatinized and still retain its biocompatibility and permeability. To develop an innovative composite material for effective wound dressings, we added pHA powder to SF and gelatinized the compound. We then applied the gel composite on full-thickness porcine skin wounds for investigation of its healing effect. The pHA transforms the SF structure into a porous three-dimensional scaffold. It was found that the SF gel containing pHA (pHA/SF) had higher promotive effects on wound healing, re-epithelization, and matrix formation than did the other prepared gel composites in the study. The pHA/SF effectively advanced the maturation of fibroblast cells benefiting from its structural advantages and stored charges. To our knowledge, this is the first report of the preparation of pHA/SF gel and identification of its wound-healing effects in vivo.

Osteoclasts are multinuclear cells of the monocyte macrophage lineage. They are responsible for bone remodeling by first resorbing packets of bone, which are subsequently replaced by new bone produced by osteoblasts. Osteoblasts are derived from mesenchymal stem cells, and thus osteogenesis can also be induced in various tissues at extra skeletal sites. Fifty years ago it was discovered that demineralized bone matrix is able to induce ectopic bone formation. Since that time the differentiation of bone cells has been studied intensively. The aim was to produce bone for the repair of bone defects. The molecular basis of bone remodeling has been established in great detail and the mechanism of how bone resorption and bone formation are coupled in bone remodeling sites has been delineated. Osteoclasts resorb bone, but they also secrete anabolic signals that induce mesenchymal stem cells and osteoblasts to initiate osteogenesis in resorption lacuna (remodeling) or another nonresorbed site (modeling). It is this osteoclast derived influence on mesenchymal stem cells and osteoblasts that could be utilized in tissue engineering. So far investigators have tried to find ways to induce bone formation by activating mesenchymal stem cells, but a better understanding of the remodeling paradigm of bone, the intrinsic regulation of bone formation through osteoclastic resorption, could be utilized for tissue engineering. Scaffold materials like decellularized natural tissue extracellular matrices or bone type resorbable mineral matrices induce resorption and simultaneously induce bone formation.

The binding of orally administered imidafenacin, used to treat overactive bladders, to muscarinic receptors in rat tissue was characterized based on pharmacokinetics. The binding in six tissues including bladder tissue was measured using [N-methyl-3 H] scopolamine methyl chloride ([ 3 H]NMS). Pharmacokinetic parameters were estimated from measurements of the concentration of imidafenacin in serum, the bladder, and the submaxillary gland by liquid chromatography-mass spectrometry/mass spectrometry. The receptor binding affinity of imidafenacin in vitro was significantly lower in the bladder than submaxillary gland or colon. The oral administration of imidafenacin (0.79, 1.57, and 6.26 mol/kg) was characterized by a more selective and longer-lasting binding to muscarinic receptors in the bladder than other tissues. Imidafenacin showed little binding to brain muscarinic receptors, consistent with its minor effect on the central nervous system. Pharmacokinetic data showed that orally administered imidafenacin was distributed at a higher concentration in the bladder than the serum or submaxillary gland of rats. After the intravesical instillation of imidafenacin, there was significant binding of muscarinic receptors in the bladder. Furthermore, a significant level of imidafenacin was detected in the urine of rats given a 1.57 mol/kg concentration of this agent. The present study demonstrated that imidafenacin administered orally distributes predominantly to the bladder and exerts more selective and longer-lasting effect on the bladder than other tissues, such as the submaxillary gland, colon, and brain. Furthermore, the imidafenacin excreted in urine may play an important role in pharmacokinetic and pharmacological selectivity.

Hydroxyapatite (HAp), well known as a biomaterial, is also known as a proton conductor. Its electrical properties are related strongly to its stability and surface properties. In particular, persistent electrical polarization related to proton conductivity of hydroxyapatite has a substantial influence on hydroxyapatite surface properties. The origins of polarizations were investigated in proton-defect-induced HAp ceramics using thermally stimulated depolarization current (TSDC) measurements. Two peaks were observed, indicating that the persistent polarization comprises polarization elements of two kinds. The TSDC response as a function of the applied electric field in polarization treatments indicated that the persistent polarization is dipole polarization and space charge polarization. The former, dipole polarization, increased continuously with increased defect concentration. The activation energies were 0.67–0.86 eV, which are comparable to proton conduction activation energy. Results show that dipole polarization consists of electrical dipoles of the defect pairs, which are formed through proton conduction. The activation energies of 1.01 ± 0.01 eV for space charge polarization are independent of the defect concentration, suggesting that these originated from protons trapped at the grain boundaries as a result of long-range proton conduction. The polarization of two different types is expected to exert different effects on the HAp surface properties.

Besides lowering cholesterol, statins exert multiple effects, such as anti-inflammatory activity and improvement of endothelial cell function. We examined whether simvastatin (SS) protects against the development of elastase-induced pulmonary emphysema in mice by using mean linear intercepts of alveoli (Lm) as a morphometric parameter of emphysema. After injection of intratracheal elastase on day 0, C57BL/6 mice were treated daily with SS (SS+ group) or PBS (SS− group) for 2 wk. A 21% decrease in Lm on day 7 was observed in the SS+ group vs. the SS− group. Anti-inflammatory effects of SS were observed as a decrease in percentage of neutrophils up to day 3, and in hydroxyproline concentration on day 3, in bronchoalveolar lavage fluid (BALF). SS also increased the number of proliferating cell nuclear antigen (PCNA)-positive alveolar epithelial cells between days 3 and 14. To confirm the role of statins in promoting proliferation of alveolar cells, mice were treated with SS (SS+) vs. PBS (SS−) for 12 days, starting 3 wk after elastase administration. After SS treatment, Lm decreased by 52% and PCNA-positive alveolar epithelial cells increased compared with the SS− group. Concentrations of vascular endothelial growth factor in BALF and endothelial nitric oxide synthase protein expression in pulmonary vessels tended to be higher in the SS+ group vs. the SS− group in this protocol. In conclusion, SS inhibited the development of elastase-induced pulmonary emphysema in mice. This therapeutic effect was due not only to anti-inflammation but also to the promotion of alveolar epithelial cell regeneration, partly mediated by restoring endothelial cell functions.

Osteoblasts are susceptible to the surface characteristics of bioceramics and stimulation from outside the cells. The purpose of this study was to evaluate the effects of electrical polarization on surface characteristics and osteoblastic adhesion. The surface characteristics revealed that electrical polarization had no effect on the surface roughness, crystallinity, and constituent elements. According to contact-angle measurements, electrically polarized hydroxyapatite (HA), which provides two kinds of surfaces, negatively charged HA (N-HA) and positively charged HA (P-HA), was even more hydrophilic than that of normal HA (O-HA). Morphological observations and quantitative analyses revealed that the typical adhered cells had a round shape on O-HA but had a spindle or fanlike spreading configuration on N-HA and P-HA 1 h after seeding. After 3 h of cultivation, the rate of the number of spread cells and the size of the focal adhesions on O-HA increased and approached that of N-HA and P-HA. However, the cell areas positively stained for actin, which indicates the degree of cell spreading, were distinctly larger on N-HA and P-HA than that on O-HA. The number of focal adhesions per cell was also less than that on N-HA and P-HA.

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