Yasuhiro Okazaki

Bone regeneration following injection of mesenchymal stem cells and fibrin glue with a biodegradable scaffold

AIM The purpose of this study was to determine whether a combination of fibrin glue, beta-tricalcium phosphate as a biodegradable (beta-TCP) and mesenchymal stem cells would provide three-dimensional templates for bone growth resulting in new bone formation at heterotopic sites in the rat with plasticity. MATERIAL AND METHODS Growing stem cells and developing matrices, explanted from the rat femur, were fragmented and mixed with fibrin glue in a syringe. The cells/beta-TCP fibrin glue admixtures were injected into the subcutaneous space on the dorsum of the rat. RESULTS Eight weeks after implantation, gross morphology revealed a pearly opalescence and firm consistency. Histological inspections showed newly formed bone structures in all admixtures, but none in the control groups when only fibrin glue and beta-TCP were injected. Osteopontin, a protein important in bone development, was identified by using antibodies in all cells/beta-TCP fibrin glue admixtures. CONCLUSION Mesenchymal stem cells/beta-TCP fibrin glue admixtures can result in successful bone formation. This technique holds the promise of a minimally invasive means of generating autogenous bone to correct or reconstruct bony defects.

Tissue-engineered bone using mesenchymal stem cells and a biodegradable scaffold.

Bone marrow has been shown to contain a population of rare cells capable of differentiating to the cells that form various tissues. These cells, referred to as mesenchymal stem cells (MSCs), are capable of forming bone when implanted ectopically in an appropriate scaffold. The aim of this study was to investigate the potential of a new &bgr;-tricalcium phosphate (&bgr;-TCP) as a scaffold and to compare the osteogenic potential between &bgr;-TCP and hydroxyapatite (HA). The &bgr;-TCP and HA loaded with MSCs were implanted in subcutaneous sites and harvested at 1, 2, 4, and 8 weeks after implantation for biochemical and histological analysis. Biochemically, in both &bgr;-TCP and HA composites, the alkaline phosphatase activity in the composites could be detected and was maintained at a high level for 8 weeks. In the histological analysis, active bone formation could be found in both the &bgr;-TCP and HA composites. These findings suggest that &bgr;-TCP could play a role as a scaffold as well as HA. The fabricated synthetic bone using biodegradable &bgr;-TCP as a scaffold in vivo is useful for reconstructing bone, because the scaffold material is absorbed several months after implantation.

Salivary growth factors in health and disease.

The salivary gland is considered to be a reservoir of many growth factors in rodents. In humans, the epidermal growth factor, basic fibroblast growth factor, and insulin and insulin-like growth factor family have also been detected in this gland, but their physiological role remains unclear. In this study, we focused on bFGF, which is a well-known mitogen for various types of cells, and is present in the salivary gland as well as in saliva. The roles of bFGF in the salivary gland were investigated by three different procedures. First, the effects of bFGF on the salivary gland cells were investigated with a monolayer culture of normal submandibular gland cells. The effects of different concentrations of bFGF on the second passage of these cultured cells were examined. In both human and rat cultured submandibular gland cells, bFGF accelerated the cell proliferation at a concentraion of 100 ng/mL or higher. Next, an atrophic model of the rat submandibular gland was used to examine the ability of bFGF to accelerate tissue repair. Two weeks after ductal ligation, the ligature was removed, and various amounts of bFGF, isoproterenol, or saline were administered via a retrograde duct instillation. Both isoproterenol and bFGF increased acinar and ductal cell proliferation significantly. To determine the role of bFGF in saliva, we investigated its effect on the healing process of oral mucosal defects. Four-millimeter mucosal defects were made to the depth of the periosteum in the rat palate under anesthesia. bFGF or vehicle alone was applied once only at the time of surgery as a suspension. At days 3, 5, and 7 in the bFGF group, significant increases in the degree of re-epithelialization were found in treated groups. These results indicate that its action as a mitogen stimulus is the major effect of bFGF on salivary gland cells and mucosal epithelium.

Acceleration of rat salivary gland tissue repair by basic fibroblast growth factor.

A model of atrophic rat submandibular gland was used to examine the ability of basic fibroblast growth factor (bFGF) to accelerate tissue repair. The gland duct was separated carefully from associated blood vessels and nerve, and ligated with a 8-0 suture under a surgical microscope. Two weeks after ligation, the glandular tissue showed severe atrophy and weight loss (to 26% of that in a sham-operated group). Thereafter, the ligature was removed and various amounts of bFGF, isoproterenol or saline were instilled retrogradely through the duct. Both isoproterenol and bFGF increased cell proliferation significantly. bFGF accelerated the proliferation of various cell types, including both acinar and ductal. The proliferative effects of bFGF peaked at a dose of 1 ng/gland. When bFGF (1 ng/gland) was administered to the atrophic gland, its weight increased to 125% of the glands in saline-treated control animals after 2 weeks. The effects of bFGF were also examined in normal submandibular glands: bFGF stimulated cell proliferation, but the effective concentration was at least 50 times higher than that required in the atrophic gland. The results from immunohistochemical tests against anti-FGF receptor-type 1 antibody demonstrated increased immunoreactivity in the damaged gland, which might be involved in the difference in the response to bFGF between damaged and normal glands. Overall, the results indicate that bFGF can accelerate tissue repair in salivary gland.

Effects of basic fibroblast growth factor on cultured rat and human submandibular salivary gland cells.

Basic fibroblast growth factor (bFGF) is a strong mitogen for most mesoderm- and ectoderm-derived cells. Although bFGF exists in rat and human salivary glands, its physiological role in those glands is unknown. In this study, the effects of bFGF were investigated in monolayer culture of normal rat and human submandibular gland cells. Epithelial cells from rat and human submandibular glands were cultivated with the aid of 3T3 cells as a feeder layer. The effects of different concentrations of bFGF on the second passage of these cultured cells were examined. In both the rat and human cells, the percentage of bromodeoxyuridine (BrdU)-positive cells gradually increased up to 50 ng/ml, and then increased sharply at 100 ng/ml. However, at concentrations higher than 100 ng/ml, the percentages of BrdU-positive cells reached a plateau. In both rat and human cells, total cell numbers at 100 ng/ml bFGF were significantly higher than those of the control group from culture day 4. On the other hand, the morphology of the cultured cells showed no difference either with or without bFGF. These results indicate that a major effect of bFGF on salivary gland epithelial cells is to act as a mitogenic stimulus.

Clinical Evaluation of Vascularized Bone Grafts and Osseointegrated Implants

We evaluated mandibular rehabilitation using vascularized bone graft and osseointegrated implants. Questionnaires were used to evaluate the masticatory function, and we measured the occlusal force in each patient. In addition, we measured the height of grafted bone to assess the possible relationship between masticatory rehabilitation and the change in bony height. Five of 13 patients showed over 12.0% increase in bony height after superstructure fabrication. Most of the patients who underwent tongue resection scored low points on the questionnaire. Also, most patients with resection, including resection of the angles of the mandible, showed a lower occlusal force than those without.

Malignant tumors metastasized to oral and maxillofacial regions from other organs; Report of two cases.

頭頸部以外に原発した悪性腫瘍が口腔領域に転移したものは比較的まれである。今回, 口腔領域に転移した悪性腫瘍の症例を2例経験したので報告した。症例1は左頬部の腫脹を主訴に当科来院した84歳の女性である。口腟内病変部の生検の結果は腺癌であった。患者は約10年以上前に左乳房腺癌の既往を有し, 病理組織学的検討などより, 乳癌の口腟内への転移と診断した。症例2は左頬部から顎下部にかけての腫脹と疼痛が主訴の71歳の男性である。臨床診断は下顎歯肉癌で, 生検の結果は大細胞癌であった。レントゲン, CT, 喀痰細胞診より肺の大細胞癌が疑われ, 肺癌の口腔内への転移と診断した。