Miya Ishihara

The properties of bioengineered chondrocyte sheets for cartilage regeneration.

BackgroundAlthough the clinical results of autologous chondrocyte implantation for articular cartilage defects have recently improved as a result of advanced techniques based on tissue engineering procedures, problems with cell handling and scaffold imperfections remain to be solved. A new cell-sheet technique has been developed, and is potentially able to overcome these obstacles. Chondrocyte sheets applicable to cartilage regeneration can be prepared with this cell-sheet technique using temperature-responsive culture dishes. However, for clinical application, it is necessary to evaluate the characteristics of the cells in these sheets and to identify their similarities to naive cartilage.ResultsThe expression of SOX 9, collagen type 2, 27, integrin α10, and fibronectin genes in triple-layered chondrocyte sheets was significantly increased in comparison to those in conventional monolayer culture and in a single chondrocyte sheet, implying a nature similar to ordinary cartilage. In addition, immunohistochemistry demonstrated that collagen type II, fibronectin, and integrin α10 were present in the triple-layered chondrocyte sheets.ConclusionThe results of this study indicate that these chondrocyte sheets with a consistent cartilaginous phenotype and adhesive properties may lead to a new strategy for cartilage regeneration.

Recent technological advancements related to articular cartilage regeneration

Some treatments for full thickness defects of the articular cartilage, such as the transplantation of cultured chondrocytes have already been performed. However, in order to overcome osteoarthritis, we must further study the partial thickness defects of articular cartilage. It is much more difficult to repair a partial thickness defect because few repair cells can address such injured sites. We herein show that bioengineered and layered chondrocyte sheets using temperature-responsive culture dishes may be a potentially useful treatment for the repair of partial thickness defects. We also show that a chondrocyte-plate using a rotational culture system without the use of a scaffold may also be useful as a core cartilage of an articular cartilageous defect. We evaluated the properties of these sheets and plates using histological findings, scanning electrical microscopy, and photoacoustic measurement methods, which we developed to evaluate the biomechanical properties of tissue-engineered cartilage. In conclusion, the layered chondrocyte sheets and chondrocyte-plates were able to maintain the cartilageous phenotype, thus suggesting that they could be a new and potentially effective therapeutic product when attached to the sites of cartilage defects.

Multispectral photoacoustic tomography for detection of small tumors inside biological tissues

Visualization of small tumors inside biological tissue is important in cancer treatment because that promotes accurate surgical resection and enables therapeutic effect monitoring. For sensitive detection of tumor, we have been developing photoacoustic (PA) imaging technique to visualize tumor-specific contrast agents, and have already succeeded to image a subcutaneous tumor of a mouse using the contrast agents. To image tumors inside biological tissues, extension of imaging depth and improvement of sensitivity were required. In this study, to extend imaging depth, we developed a PA tomography (PAT) system that can image entire cross section of mice. To improve sensitivity, we discussed the use of the P(VDF-TrFE) linear array acoustic sensor that can detect PA signals with wide ranges of frequencies. Because PA signals produced from low absorbance optical absorbers shifts to low frequency, we hypothesized that the detection of low frequency PA signals improves sensitivity to low absorbance optical absorbers. We developed a PAT system with both a PZT linear array acoustic sensor and the P(VDF-TrFE) sensor, and performed experiment using tissue-mimicking phantoms to evaluate lower detection limits of absorbance. As a result, PAT images calculated from low frequency components of PA signals detected by the P(VDF-TrFE) sensor could visualize optical absorbers with lower absorbance.

3D quantitative photoacoustic image reconstruction using Monte Carlo method and linearization

To quantify the functional and structural information of peripheral blood vessels for diagnoses of diseases which affects peripheral blood vessels such as diabetes and peripheral vascular disease, a 3D quantitative photoacoustic tomography (QPAT) reconstructing the optical properties such as the absorption coefficient reflecting microvascular structures and hemoglobin concentration and oxygenation saturation is studied. QPAT image reconstruction algorithms based on radiative transfer equation (RTE) and photon diffusion equation (PDE) have been proposed. However, it is not easy to use RTE in the clinical practice because of the huge computational load and long calculation time. On the other hand, it is always considered problematic to use PDE, because it does not approximate RTE well near the illuminating position. In this study, we developed the 3D QPAT image reconstruction using Monte Carlo (MC) method which approximates RTE better than PDE to reconstruct the optical properties in the region near the illuminating surface. To reduce the calculation time, we applied linearization. The QPAT image reconstruction algorithm with MC method and linearization was examined in numerical simulations and phantom experiment by use of a scanning system with a single probe consisting of P(VDF-TrFE) piezo electric film and optical fiber.

Transdermal delivery of photosensitizer by laser-induced stress wave

The skin permeability of most of drugs is low, because the stratum corneum works as a solid barrier. It is required, therefore, to enhance the skin permeability for transdermal delivery of drug. To investigate the effects of heating skin and exposing skin to a laser-induced stress wave (LISW) on the drug permeability, we tried to deliver porfimer sodium into rat’s skin. The experiment was performed under the four different skin conditions; exposing to a LISW (case 1); heating (case 2); exposing to a LISW and heating (case 3); control (case 4). It was observed in all cases except the case 4 (control), the drug permeated into the dermis through the epidermis. The deepest penetration was obtained in the case 3 (a LISW plus heating). It was suggested that heating increased the fluidity of the lipid bilayers in the stratum corneum, and therefore the drug permeability might be enhanced.

Signal analysis of fiber optic probe method from Ho:YAG laser ablation bubble

We experimentally and theoretically studied interpretation of the waveform signal which was obtained by the fiber-optic probe method during Ho:YAG laser ablation. We monitored behavior of the ablation bubble which occurs at the fiber tip during the ablation by means of developed fiber-optic probe method as well as time-resolved photography to investigate the information which involves the waveform signal. We used water and agar as model materials for different purposes. We determined that the waveform signal from the fiber-optic probe method is mainly attributed to the reflection of the boundary between the water-vapor bubble and surrounding material/tissue. We also found that the intensive shockwave which is induced may be monitored by our method.