Biomedical subjects

Izumi Asahina

Publications and source records attributed to Izumi Asahina.

6 recordsLinked to original sources

PubMed2006

Expression of heat shock protein 47 in the fibrous tissue adjacent to mouse tumour subjected to photodynamic therapy.

The reaction of normal fibrous tissue adjacent to tumours subjected to photodynamic therapy (PDT) was investigated by assessment of the immunohistochemical expression of heat shock protein 47 (HSP47) and proliferating cell nuclear antigen (PCNA), as well as by immunoblot analysis of procollagen type I. PDT was administered to NR-S1 mouse squamous cell carcinoma or normal mouse skin. Each of four mice was investigated at several time points after receiving PDT. The levels of HSP47 expression were determined by computer-assisted image analysis. The expression of procollagen type I in the fibrous tissue adjacent to the tumours was examined by immunoblot analysis at intervals of 24 and 48h after PDT. The expression of HSP47 was first detected 6h post-PDT in the tumour-bearing mice, but no such expression was observed in the normal mice. It was also revealed that, after PDT, the fibroblast PCNA labeling indices at 24, 48, and 72h were significantly higher in both the tumour-bearing and the normal mice than in the control animals that did not receive PDT. Furthermore, procollagen type I was detected in the fibrous tissue adjacent to the tumours at 24 and 48h after PDT, but was not detected in the fibrous tissue adjacent to tumours of mice that did not receive PDT. Therefore, the present results suggest that PDT enhances the synthesis of collagen type I in the fibrous tissue adjacent to NR-S1 squamous cell carcinoma in mice, which contributes to the resultant encapsulation of such tumours.

Animals↗

PubMed2006

Mandibular reconstruction using a combination graft of rhBMP-2 with bone marrow cells expanded in vitro.

BACKGROUND: The aim of this study was to evaluate the efficacy of a combination graft, using recombinant human bone morphogenetic protein-2 (rhBMP-2) and culture-expanded cells derived from bone marrow, for bone regeneration in a nonhuman primate mandible. METHODS: Five Japanese monkeys were used. Three milliliters of bone marrow was obtained from the tibia and plated into culture flasks. Adherent cells were cultured until near confluence; then, the proliferated cells were transferred to a three-dimensional culture system using collagen beads as the cell carrier. The medium was supplemented with ascorbic acid, beta-glycerophosphate, and dexamethasone to promote osteoblastic differentiation. After further proliferation on beads, the cells were mixed with a collagen sponge that was impregnated with rhBMP-2 and grafted into surgically created segmental bone defects of the mandibles. Three animals received this treatment, and either culture-expanded cells alone or collagen beads without cells were implanted into the remaining two monkeys as controls. The animals were killed 24 weeks after surgery, and the results were assessed by radiographic and histologic evaluation. RESULTS: The combination graft of culture-expanded bone marrow cells with rhBMP-2 in a collagen sponge regenerated the mandibular bone completely. By contrast, the graft of culture-expanded cells alone resulted in only a small amount of bone formation, and the implantation of collagen beads alone led to no bone formation. CONCLUSION: The combination graft of rhBMP-2 and culture-expanded cells, which requires only a small amount of bone marrow, is a reliable method for the reconstruction of segmental bone defects of the mandible.

Animals↗

PubMed2003

Administration of parathyroid hormone, prostaglandin E2, or 1-alpha,25-dihydroxyvitamin D3 restores the bone inductive activity of rhBMP-2 in aged rats.

Bone morphogenetic protein (BMP) induces bone formation in young rodents, but aging causes a reduction in the bone-forming ability of BMP. Most patients who require bone reconstruction are relatively old. Accordingly, we examined whether anabolic hormones could restore the bone inductive activity of rhBMP-2 in aged rats. rhBMP-2 in a carrier pellet was implanted subcutaneously in both 4- and 50-week-old female Wistar rats. PTH, PGE2, or 1,25(OH)2D3 was injected every day during the period of BMP implantation. The pellets were harvested, and were examined both histologically and biochemically 2 weeks after implantation. Bone-forming ability was measured by alkaline phosphatase (ALP) activity and calcium (Ca) content. Pellets in 50-week-old rats showed a significant reduction in bone formation compared to pellets in 4-week-old rats. However, daily injections of PTH into 50-week-old rats restored both ALP activity (103 +/- 4.6%) and Ca content (105 +/- 2.6%). 1,25(OH)2D3 and PGE2 also restored Ca content (103 +/- 4.5% and 98 +/- 3.8%, respectively) and stimulated ALP activity (142 +/- 2.3% and 133 +/- 3.6%). These results show that the administration of these hormones restores bone-forming ability in aged rats. A combination treatment of these hormones with rhBMP-2 might be applicable to the reconstruction of bone defects in elderly patients.

Aging↗

PubMed2002

Restoration of occlusal function using osseointegrated implants in the canine mandible reconstructed by rhBMP-2.

Bone morphogenetic proteins have been found to be one of the most promising osteoinductive substances and they are expected to be utilized clinically for the reconstruction of defective mandibles. However, newly formed bone induced by recombinant human bone morphogenetic protein-2 (rhBMP-2) has not yet been proven able to withstand the masticatory force applied by oral implants. In this study, we examined the qualitative changes in an rhBMP-2-induced mandible from the functional force of osseointegrated oral implants. Segmental (30 mm) bone defects were created in the mandibles of beagles. A poly D,L-lactic coglycolic acid-coated gelatin sponge impregnated with rhBMP-2 was grafted to the resected canine mandible. The new bone was formed 8 weeks after surgery and the Brånemark system fixtures were implanted into the reconstructed mandible. After another 8 weeks, the prosthesis was placed over the oral implants. The prosthesis was maintained in occlusion with the opposing natural dentition for 0, 4, 12, 24, or 48 weeks before the animal was euthanized. The quality of regenerated bone was then evaluated histologically and the osseointegration ratio between oral implants and the bonemeasured. During the first 4 weeks, the ratio remarkably increased from 48.9% to 64.5%. After 48 weeks, the ratio approached about 74.5%. The bone loaded for 48 weeks had undergone extensive remodeling and consolidation; its quality was better and maturer than that of bone that was not loaded. These results indicated that the newly formed bone induced by rhBMP-2 was able to withstand the masticatory force applied by oral implants and had become as functionally mature as a natural bone.

Analysis of Variance↗

PubMed2002

[Bone regeneration using bone morphogenetic protein (BMP)].

Bone morphogenetic protein (BMP) is one of the most promising osteoinductive substances and is expected to be applied clinically for bone reconstruction. BMP has restored critical-size bone defects in numerous animal experiments, but the evaluation of bone formation by BMP in primates is a prerequisite for its clinical application. We attempted to restore the mandible bone defects in primates using BMP. The implantation of BMP with the carrier completely regenerated the mandible bone defects in the young primates, and the occlusal function was restored by the dental implants inserted into the regenerated bone. Although the use of BMP alone to regenerate mandible bone defects in old monkeys produced inconclusive results, the combination grafts of BMP and bone marrow, which contained osteoprogenitor cells, were successful. Furthermore, the combination of BMP and the culture-expanded cells derived form bone marrow grafts regenerate the segmental bone defects in the mandibles of old monkeys. Thus, the implantation of BMP with the BMP-responding cells could restore large bone defects even in elderly patients.

English Abstract↗

PubMedDate not supplied

Cultured mucosal cell sheet with a double layer of keratinocytes and fibroblasts on a collagen membrane.

The aim of this study was to develop a novel cultured mucosal membrane that was facile to prepare and easy to handle, and that could be applied to mucosal defects in the oral cavity. Human oral keratinocytes and fibroblasts were prepared from the oral mucosa. We made the following two types of cultured mucosal cell sheets: a monolayer sheet of keratinocytes cultured on a collagen membrane (K-S) and a double-layered sheet of keratinocytes and fibroblasts on a collagen membrane (KF-S). A collagen membrane was used as a control. Each type of sheet was transplanted onto dorsal skin defects of nude mice. The wound area was measured for the assessment of wound contraction and a specimen was harvested for histologic evaluation 1 week and 4 weeks after grafting. Wound contraction was minimal with KF-S grafts. Although histologic examination showed normal differentiation of the epithelium in all graft types, the involucrin expression pattern of KFS was most similar to that of normal epithelium. These results indicate that a double-layered sheet of keratinocytes and fibroblasts cultured on a collagen membrane may facilitate epithelial healing and prevent wound contraction.

Adult↗