생쥐 턱밑샘의 발생, 분화 및 노화에 따른 C-type natriuretic peptide와 natriuretic peptide 수용기의 발현양상 = Expression of C-type Natriuretic Peptide and Natriuretic Peptide Receptors in the Mouse Submandibular Glands Following Embryonic Development, Postnatal Differentiation and Aging

국문 초록 (Abstract)

C-type natriuretic peptide (CNP)는 natriuretic peptide family의 하나로서 주로 중추신경계통과 혈관내피세포에서 국소적으로 합성되는 것으로 알려져 있으나 최근 다른 말초기관에서도 합성되어 세포의 성장과 분화 조절에 관여하는 것으로 알려지고 있다. 본 연구자들은 CNP가 정상 성체 턱밑샘의 사이관과 곱슬과립세관세포에서 국소적으로 합성되어 분포하며 생물학적 활성을 보임을 보고한 바 있으나, 발생 및 분화, 그리고 노화에 따르는 발현 및 활성에 대해서는 알려진 바 없다. 따라서 본 연구는 턱밑샘의 발생 및 분화과정에서 CNP와 그 수용기의 발현양상과 노화과정에서 그 수용기의 생물학적 활성변화를 알아보고자, 임신14, 16, 18일된 C57BL/6N 생쥐 배자와 출생 후 1일, 2주, 그리고 1, 2, 12, 24개월된 성체의 턱밑샘을 대상으로 RT-PCR, in situ hybridization, 면역조직화학법 그리고 cGMP assay를 시행하였다. CNP는 임신14일에 턱밑샘의 원기인 외배엽성상피싹 종말부위에서 강하게 발현되었으며 출생 전까지 높게 유지되었으나 출생 후 현저히 감소되었다. CNP는 성체 턱밑샘의 사이관과 곱슬과립세관에 분포하고 있었으며 이들 관계통에서 NPRC는 특이적으로 발현되었으나 NPRB는 발현되지 않았다. RT-PCR결과 턱밑샘에서 CNP전사체는 임신16일부터 출생 후 2개월까지 점차 감소하였으나 ANP전사체는 증가하였다. CNP에 특이적인 수용기인 NPRB와 NPRC는 CNP와 동일한 발현양상이었으나 NPRA는 약하게 발현되었다. 또한 CNP는 치아싹, 혀, 앞위턱뼈, 뼈형성 부위와 같은 두개안면 조직에서도 발현되었으며, 이들 부위에서도 NPRC는 발현되었으나 NPRB는 발현되지 않았다. 출생 후 2개월된 턱밑샘의 관세포는 CNP에 의해 현저히 많은 cGMP를 생성하였으나, 샘꽈리는 CNP보다는 ANP와 BNP에 의해 많은 cGMP를 생성하였다. 노화에 따라 턱밑샘의 cGMP 활성능력은 전반적으로 감소되었으며 출생 후 1개월된 턱밑샘에서는 CNP, 출생 후 2개월 이후로는 ANP에 의한 cGMP 활성이 우세하였다. 이상의 결과로 보아 CNP는 턱밑샘에서 NPRC를 매개로 하는 발생 및 분화유도 기능을 주로 수행하며, 성체이후에는 NPRB를 매개로 하는 관계통 유지에 관여하고 노화에 따라서 활성이 점차 감소하는 것으로 추정된다.

다국어 초록 (Multilingual Abstract)

C-type natriuretic peptide (CNP), a member of natriuretic peptide family, is mainly synthesized in the endothelium and central nervous system. But CNP is also involved in the growth and differentiation of other
peripheral organs. Although we have reported the local synthesis and localization of CNP in the adult submandibular glands (SMG), it is not known that the expression and biological activity of CNP following the morphogenesis, differentiation and aging. This study aimed to examine the expression of CNP and its receptors in the developing and differentiating stages of mouse SMG, and the changes of biological activity of its receptors with aging. The SMG, obtained from 14, 16, 18 days-old embryos (E) and 1 day, 2 weeks, 1, 2, 12, and 24 month-old C57BL/6N mouse, were processed for RT-PCR, in situ hybridization, immunohistochemistry and cGMP assay. CNP was strongly expressed in the epithelial clusters of primitive SMG, which was maintained before birth but was markedly decreased after birth. CNP was localized in the intercalated duct and granular convoluted tubules of adult SMG, where NPRC was specifically expressed but NPRB was not. CNP mRNA was gradually decreased from E16 to 2 M but ANP mRNA was opposed. NPRB and NPRC were the same pattern of the expression of CNP but NPRA was weakly expressed. In addition, CNP mRNA was also expressed in the craniofacial tissues such as tooth germs, tongue, premaxilla and bone forming area in which NPRC was specifically expressed but NPRB was not. In the SMG of 2 M, the membrane of duct cells markedly produced cGMP by CNP whereas acini produced cGMP by ANP and BNP rather than CNP. The biological activity of cGMP production of SMG gradually decreased with age. cGMP production was dominant by CNP in SMG of 1M but was by ANP after 2M. These results shows that CNP may play roles both in the morphogenesis and differentiation via NPRC and in the maintenance of duct system via NPRB in the mouse SMG and that the biological activity of its receptors may decreased with aging.

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