Yuzo Ishiwari

Quantitation of epidermal growth factor receptor gene amplification by competitive polymerase chain reaction in pre-malignant and malignant oral epithelial lesions.

Abnormal amplification of epidermal growth factor receptor (EGFR) gene has been reported widely in various human tumors. However, the status of amplification of this gene in the process of carcinogenesis is not clearly defined. We used competitive polymerase chain reaction (PCR) to study whether EGFR gene is amplified and the degree of amplification in pre-malignant and malignant oral epithelial lesions, and also examined the relationship between EGFR gene aberration and the development of squamous cell carcinoma (SCC). Genomic DNA was extracted from paraffin sections of 17 cases of oral epithelial dysplasia (ED), four cases of carcinoma in situ (CIS), and 20 cases of untreated primary SCC. The extracted DNA was subjected to competitive PCR to amplify EGFR gene. Amplification of the EGFR gene was observed in three cases (17%) of ED, one case of CIS and four cases (20%) of SCC. In cases showing EGFR gene amplification, the degree of amplification was low in ED and CIS cases, whereas it was extremely high in SCC cases. These results suggest that amplification of EGFR gene occurs in the relatively early stage of the development of oral SCC. However, a high level of EGFR gene accumulation probably plays an important role in the progression to invasive cancer.

Age effects on ectopic bone formation induced by purified bone morphogenetic protein

A mixture of heparin-Sepharose-purified bovine bone morphogenetic protein and type I atellocollagen was implanted in the subcutaneous tissues of 4-week, 10-month and 18-month-old rats. The implants were removed at 7, 14 and 21 days after implantation. The effects of rat age on ectopic bone formation were evaluated on the explants using haematoxylin-eosin staining, morphometric analysis, alkaline phosphatase activity and calcium content determination, as well as immunohistochemical staining of type IV collagen present in the basement membrane of blood vessels. On day 14 and 21, bone was observed in 4-week and 10-month-old rats, but the amount of bone formed in the latter was less than in the 4-week-old rats. In 18-month-old rats, bone was first found focally in very limited regions of the explants on day 21 and the amount of bone was much less than in 4-week-old rats. At all periods, alkaline phosphatase activity was higher in younger rats. On day 7, there were more blood vessels in the explants of 4-week-old rats than in those of 10-month or 18-month-old rats. On day 14 and 21, more blood vessels were found in the central regions of the explants in 4-week-old rats than in the same regions in 10-month or 18-month-old rats. The findings in the present study indicate that the rate and quantity of ectopic bone formation are reduced in aged rats, and suggest that the difference in blood vessel distribution is related to this reduction in ectopic bone formation.

Expression of type I, type II, and type X collagen genes during altered endochondral ossification in the femoral epiphysis of osteosclerotic (oc/oc) mice.

The osteosclerotic (oc/oc) mouse, a genetically distinct murine mutation that has a functional defect in its osteoclasts, also has rickets and shows an altered endochondral ossification in the epiphyseal growth plate. The disorder is morphologically characterized by an abnormal extension of hypertrophic cartilage at 10 days after birth, which is later (21 days after birth) incorporated into the metaphyseal woven bone without breakdown of the cartilage matrix following vascular invasion of chondrocyte lacunae.In situ hybridization revealed that the extending hypertrophic chondrocytes expressed type I and type II collagen mRNA, as well as that of type X collagen and that the osteoblasts in the metaphysis expressed type II and type X collagen mRNA, in addition to type I collagen mRNA. The topographic distribution of the signals suggests a possible coexpression of each collagen gene in the individual cells. Immunohistochemically, an overlapping deposition of type I, type II, and type X collagen was observed in both the extending cartilage and metaphyseal bony trabeculae. Such aberrant gene expression and synthesis of collagen indicate that pathologic ossification takes place in the epiphyseal/metaphyseal junction ofoc/oc mouse femur in different way than in normal endochondral ossification. This abnormality is probably not due to a developmental disorder in the epiphyseal plate but to the failure in conversion of cartilage into bone, since the epiphyseal plate otherwise appeared normal, showing orderly stratified zones with a proper expression of cartilage-specific genes.

Age and magnetic effects on ectopic bone formation induced by purified bone morphogenetic protein

A mixture of heparin-Sepharose-purified bovine bone morphogenetic protein (BMP) and type I atellocollagen was implanted in the subcutaneous tissues of 4-week, 10-month and 18-month-old rats. The implants were removed at 7, 14 and 21 days after implantation. The effects of rat age on ectopic bone formation were evaluated on the explants using H&E staining, morphometric analysis, alkaline phosphatase (ALP) activity and calcium (Ca) content determination, as well as immunohistochemical staining of type IV collagen present in the basement membrane of blood vessels. On day 14 and 21, bone was observed in 4-week and 10-month-old rats but the amount of bone formed in the later was less than in the former. In 18-month-old rats, bone was first found focally in very limited regions of the explants on day 21 and the amount of bone was much less than in 4-week-old rats. At all periods ALP activity was higher in younger rats. On day 7, there were more blood vessels in the explants of 4-week-old rats than in those of 10- or 18-month-old rats. On day 14 and 21, more blood vessels were found in the central regions of the explants in 4-week-old rats than in the same regions in 10- or 18-month-old rats. The findings in the present study indicated that the rate and quantity of ectopic bone formation were reduced, and that the difference in blood vessel distribution might be related to the reduction in ectopic bone formation in aged rats, and suggest that the difference in blood vessel distribution is related to ectopic bone formation. Magnetism can stimulate ectopic bone formation induced by BMP.