Three-dimensional morphological study on formation and development of morphological hepatic zonation during pre- and postnatal periods in house musk shrews (Suncus murinus )

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要旨 肝実質細胞は、形態的機能的不均質性を示し、肝小葉内に肝領域を形成する。本研究は、スンクス肝実質細胞の不均質性発現と肝細胞索の形成過程を明らかにすることを目的とする。胎仔期から成獣期の樹脂包埋連続標本を作製し、二次元形態解析を行った。さらに同領域について、肝細胞索の立体再構築を行い、三次元的に検証した。肝実質細胞の体積の部位差は、生後4 日から16 日にかけて、門脈域細胞の大型化によって顕著になった。その後、細胞の体積はさらに増大し、小葉の成長に寄与していた。形状の不均質性は造血巣の小葉内局在と関連しており、造血巣の消失後、全ての肝細胞は、成獣と同様の多面体を呈した。また肝細胞索の立体的な連続性は、胎生29 日には形成されることが示された。スンクス肝組織は哺乳類のなかでも比較的単純な組織構造しており、形成過程の立体的な可視化は、生物模倣の候補のひとつとして、再生医療分野等における活用が期待される。
Hepatocytes exhibit morphological and functional heterogeneity, and form regional divisions within the hepatic lobules. The aim of the present study is to clarify the development of the spatial morphological heterogeneity of hepatocytes and the process of the hepatic-cell-cord formation in Suncus Murinus. Two-dimensional analysis was carried out using epoxy-embedded semithin sections of livers from embryonic to adulthood. Furthermore, we performed three-dimensional reconstruction of hepatic-cell-cords and stereoscopically verification of the obtained findings. The regional heterogeneity in the volume of hepatocytes became remarkable from the 4th to 16th day after birth in portal regions. After that, the volume of hepatocytes further increased, and that was contributed to the growing of hepatic lobules. The heterogeneity in shape of hepatocytes was associated with the hematopoietic compartments, and almost all hepatocytes became polyhedral shape after disappearance of the hematopoietic cells. The spatial structure of hepatic-cell-cord was almost complete at embryonic 29th day. The hepatic spatial structure of Suncus was relatively simple in mammals, so the elucidation of the developmental process of the spatial structure will be useful as one of candidate of biomimicry.