Odontoblasts produce most of the extracellular matrix (ECM) components found in dentin and implicated in dental mineralization. Major differences in the pulp ECM explain why pulp is normally a non-mineralized tissue. In vitro or in vivo, some dentin ECM molecules act as crystal nucleators and contribute to crystal growth, whereas others are mineralization inhibitors. After treatment of caries lesions of moderate progression, odontoblasts and cells from the sub-odontoblastic Höhl's layer are implicated in the formation of reactionary dentin. Healing of deeper lesions in contact with the pulp results in the formation of reparative dentin by pulp cells. The response to direct pulp-capping with materials such as calcium hydroxide is the formation of a dentinal bridge, resulting from the recruitment and proliferation of undifferentiated cells, which may be either stem cells or dedifferentiated and transdifferentiated mature cells. Once differentiated, the cells synthesize a matrix that undergoes mineralization. Animal models have been used to test the capacity of potentially bioactive molecules to promote pulp repair following their implantation into the pulp. ECM molecules induce either the formation of dentinal bridges or large areas of mineralization in the coronal pulp. They may also stimulate the total closure of the pulp in the root canal. In conclusion, some molecules found in dentin extracellular matrix may have potential in dental therapy as bioactive agents for pulp repair or tissue engineering.

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FIn cleft palate surgery, mucoperiosteal denudation of palatal bone is considered an important inhibiting factor of maxillary growth. This study investigated the effects of local injection of basic fibroblast growth factor (bFGF) into wounds on ultrastructural changes in the bone surface during the palatal wound healing process. Ninety male 20-day-old Wistar rats were divided into control, scar formation, and bFGF groups had lateral mucoperiosteum excised from the palate. In the bFGF group, bFGF solution was injected into the operated area one week after excision. In each of the three groups, the wound healing process was histologically investigated by light and scanning electron microscopy at 4, 6, and 10 weeks postoperatively. Compared with the controls, the scar formation and the bFGF groups showed few smaller diameter vascular pores on the bone surface at 4 weeks. Thereafter the bFGF group showed increases in the number and diameter of vascular pores along with periosteum-like cell aggregations on the bone surface. In conclusion, the bFGF injection into palatal wounds increases the number and size of vascular pores and regenerates the periosteum on the bone surface during wound healing. This pharmaceutical modulation may reduce bone growth inhibition induced by mucoperiosteal denudation of the palate.

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Angiogenesis is an essential process in the progression of malignant tumors. Vascular channel of the vasculogenic mimicry type reported. However, little is known of the angioarchitecture in primary oral malignant melanoma. We sought to determine this by the use of periodic acid-Schiff (PAS) stain, endothelial markers (CD34, CD105) and laminin, and by transmission electron microscopy in eight cases. The results demonstrated that endothelium-lined vessels dominated the tumor microvasculature and these stained positively for PAS, laminin, and endothelial markers. Mosaic and tumor-lined vessels were infrequently encountered. Most PAS-positive patterned networks and loops ultrastructurally represented intratumor microhemorrhages that probably arose secondary to tumor vessel leakiness. Vascular channels of the vasculogenic mimicry type were seen infrequently.

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The morphology and characteristics of melanosomes are important features for differentiating melanocyte-derived melanotic lesions such as benign and malignant melanoma. There are two types of melanosome; eumelanin and pheomelanin. In this study, we attempted to elucidate the characteristics of melanosomes in malignant melanomas (melanotic type and amelanotic type) by ultrastructural analysis. In the melanotic type malignant melanoma in situ, pleomorphic and ellipsoid abnormal melanosomes, so-called eumelanin melanosomes, were detected, together with an increase in alkali elution rate. In the melanotic type invasive malignant melanoma, irregular ellipsoid and spheroid melanosomes were found either as discrete bodies or compound melanosomes, with further increase in alkali elution. In the amelanotic type malignant melanoma in situ, there were no melanosomes in atypical melanocytes and keratinocytes. In the amelanotic type invasive malignant melanoma, a few round melanosomes with low density matrix, so-called pheomelanin melanosomes, distributed in the cytoplasm. Our findings suggest that abnormal melanosome morphology and characteristics are predictive differential markers for the melanotic type or amelanotic type of oral malignant melanomas.

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Recently, atelocollagen has been used in tissue engineering as one of the most useful scaffolds for bone formation. However, the optimal scaffold-structure for bone engineering has not been determined. Hence, we compared the honeycomb porous structure (HPS) and the interconnected porous structure (IPS) with or without KUSA/A1 cells in vivo. KUSA/A1 cells alone, HPS alone, IPS alone, KUSA/A1-HPS and KUSA/A1-IPS were implanted in the subcutaneous pockets of 4-weeks-old male SCID mice. The implants were examined radiologically and histologically 1, 2, 4 and 8 weeks after implantation. Radiologically, small radiopaque islands of new bone were observed in the implant of KUSA/A1 cells alone. No radiopacity was observed with both scaffols alone. In the KUSA/A1-HPS implant, the scaffold was partially filled with radiopaque areas. In contrast, in the KUSA/A1-IPS implant, the whole scaffold was filled with a well-defined radiopaque area. Histologically, KUSA/A1 cells alone induced only small nests of new bone. HPS alone produced inflammatory reaction. A large bone was observed in implants of KUSA/A1 cells combined with both scaffolds, but the scaffold was completely filled with new bone without inflammatory reaction within a shorter period in the KUSA/A1-IPS compared to KUSA/A1-HPS implant. Our results indicated that a cotton structured scaffold plays an important role in carrying the cells, providing the precise size, shape and comfortable environment. These results have potential impact to enhance existing therapeutic strategies.

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