Denny P C, Liu P, Denny P A
Department of Basic Sciences, School of Dentistry, University of Southern California, Los Angeles, California 90089-0641, USA.
Anat Rec. 1999 Sep 1;256(1):84-90. doi: 10.1002/(SICI)1097-0185(19990901)256:1<84::AID-AR11>3.0.CO;2-S.
The submandibular salivary gland of mice contains a parenchymal element, the granular duct, which matures peripubertally from the striated ducts. Granular duct cells also differentiate from intercalated ducts in the adult mouse submandibular gland. Using preproNGF-A as a signature protein of mature granular duct cells, this study inquired if phenotypic determination might have occurred earlier than the first signs of cellular differentiation. Results from RT-PCR indicate the presence of preproNGF-A transcripts at all postnatal stages of development of the submandibular glands, as well as in adult sublingual glands. The preproNGF-A transcript was also detected prenatally as early as embryonic day 17 in the submandibular/sublingual complex. Using an antibody directed specifically against the "pre" peptide, immunocytochemistry showed preproNGF-A localized in the granular ducts and striated ducts of the adult submandibular gland. In addition preproNGF-A was detected throughout the first order branches of the intercalated duct system. In the neonatal gland, preproNGF-A was found in the large tubules that differentiate to the striated ducts. The early appearance of preproNGF-A in the histological lineage that sequentially gives rise to striated ducts and then to granular ducts suggests that this lineage is phenotypically determined as early as birth. An undifferentiated stage of the phenotypically determined lineage also appears to be retained in the intercalated duct system to provide progenitors for subsequent differentiation in the adult gland. Throughout development of the sublingual gland, preproNGF-A was detectable in the striated ducts or in their predecessors, suggesting that they may also represent a phenotypically determined cell lineage similar to that of the submandibular gland.
小鼠的下颌下唾液腺含有一种实质成分，即颗粒导管，它在青春期前后从纹状导管发育成熟。颗粒导管细胞也可从成年小鼠下颌下腺的闰管分化而来。本研究以前体神经生长因子A（preproNGF-A）作为成熟颗粒导管细胞的标志性蛋白，探究表型决定是否可能早于细胞分化的最初迹象出现。逆转录聚合酶链反应（RT-PCR）结果表明，在下颌下腺发育的所有出生后阶段以及成年舌下腺中均存在前体神经生长因子A转录本。早在胚胎第17天，在下颌下/舌下复合体中也检测到了前体神经生长因子A转录本。使用特异性针对“前体”肽的抗体，免疫细胞化学显示前体神经生长因子A定位于成年下颌下腺的颗粒导管和纹状导管中。此外，在闰管系统的一级分支中均检测到了前体神经生长因子A。在新生腺体中，前体神经生长因子A存在于分化为纹状导管的大管中。前体神经生长因子A在依次产生纹状导管然后颗粒导管的组织学谱系中的早期出现表明，该谱系在出生时就已确定表型。表型确定的谱系的未分化阶段似乎也保留在闰管系统中，为成年腺体中的后续分化提供祖细胞。在舌下腺的整个发育过程中，均可在纹状导管或其前身中检测到前体神经生长因子A，这表明它们可能也代表一种与下颌下腺类似的表型确定的细胞谱系。
