論文の内容の要旨

BACKGROUND: Hair discs are Known to contain a large number of Merkel cells and are ideal for investigating Merkel cell biology. Hair follicles, which are important elements of heir discs, undergo unique cyclical morphological and biological changes.

OBJECTIVES: To define the relationships between the number and the morphology of Merkel cells within the hair disc in association with the hair cycle on rat back skin.

METHODS: Merkel cells in hair discs were observed three-dimensionally using immunohistochemistry. Epidermal sheets were incubated with monoclonal murine antibody to CK20.As a result, Merkel cells in hair discs were clearly demonstrated as whole shapes and were counted under a light microscope.

RESULTS: Merkel cells in hair discs increased during the early to middle phase of anagen and decreased during the middle phase of anagen to catagen and telogen in perinatal and postnatal rat back skin. We observed the morphological variation of Merkel cells in hair discs of rat back skin, and consequently divided them into two subtypes at the light microscopic level: the ovel type and the dendritic type. The number of oval-type Merkel cells was not markedly affected by the hair cycle. In contrast, the number of dendritic-type Merkel cells markedly changed with the hair cycle.

CONCLUSIONS: This difference of the heir cycle dependency between ovel and dendritic-type Merkel cells suggests some functional differences, such as a secretory function, related to the hair cycle.

論文審査の結果の要旨

主査　戸田　修二

副査　徳永　藏

副査　増子　貞彦

　本論文は，周産期及び出生後ラット背部皮膚の毛盤に局在するメルケル細胞と毛周期との関連について述べている。

　これによると，毛盤に局在するメルケル細胞の数が，毛周期の中でも成長期の早期から中期にかけて，増加した。一方，成長期の中期から退行期，休止期にかけて，メルケル細胞の数が，減少した。更に，形態学的にメルケル細胞を，細胞突起を有さないOvel typeと細胞突起を有するDendritic typeの2種類に分類して，メルケル細胞数の変化を解析すると，Ovel typeのメルケル細胞数は変化しないが，Dendritic typeのメルケル細胞数の変化が見られた。以上の解析結果は，周産期と出生後のラットでは，同様の結果であった。

　以上の成績は，細胞突起を有するDendritic typeのメルケル細胞の数が，毛周期と共に増減することを示し，毛周期とメルケル細胞の関係について，新しい知見を加えたものであり，意義あるものと考えられる。

　よって本論文は，博士（医学）の学位論文として価値あるものと認めた。