Adachi Takahiro, Tomita Masahiro, Yoshizato Katsutoshi
Yoshizato Project, Cooperative Link of Unique Science and Technology for Economy Revitalization, Hiroshima Prefectural Institute of Industrial Science and Technology, 3-10-32, Kagamiyama, Higashihiroshima, Hiroshima, 739-0046, Japan.
Matrix Biol. 2005 Apr;24(2):136-54. doi: 10.1016/j.matbio.2005.01.007. Epub 2005 Apr 7.
The present study shows that hemocytic granular cells synthesize and secrete type IV collagen (ColIV) in the silkworm Bombyx mori (B. mori) and suggests that these cells play roles in the formation of basement membrane, the encapsulation of foreign bodies, and the metamorphic remodeling of the gut. The full- and partial-length cDNA of B. mori prolyl 4-hydroxylase alpha subunit (BmP4Halpha) and B. mori ColIV (BmColIV) were cloned, respectively. In situ hybridization and immunocytochemistry on larval tissues and cells identified hemocytic granular cells as the cells that express mRNAs and proteins of both BmP4Halpha and BmColIV. Immunohistochemistry and immunocytochemistry demonstrated that BmColIV was present in the basement membrane and in the secretory granules of granular cells, respectively. Granular cells in culture secreted BmColIV without accompanying the degranulation and discharged it from the granules when the cells were degranulated. Nylon threads were inserted into the hemocoel of larvae. Granular cells concentrated around the nylon threads and encapsulated them as a self-defense reaction. BmColIV was found to be a component of the capsules. Furthermore, the present study showed that actively BmColIV-expressing granular cells accumulated around the midgut epithelium and formed BmColIV-rich thick basal lamina-like structures there in larval to pupal metamorphosis.
本研究表明，家蚕血细胞中的颗粒细胞能合成并分泌IV型胶原蛋白（ColIV），提示这些细胞在基底膜形成、异物包囊以及肠道变态重塑过程中发挥作用。分别克隆了家蚕脯氨酰4-羟化酶α亚基（BmP4Hα）和家蚕ColIV（BmColIV）的全长及部分长度cDNA。对幼虫组织和细胞进行原位杂交和免疫细胞化学分析，确定血细胞中的颗粒细胞是同时表达BmP4Hα和BmColIV的mRNA及蛋白质的细胞。免疫组织化学和免疫细胞化学显示，BmColIV分别存在于基底膜和颗粒细胞的分泌颗粒中。培养的颗粒细胞分泌BmColIV时不会伴随脱颗粒现象，而当细胞脱颗粒时，BmColIV会从颗粒中释放出来。将尼龙线插入幼虫血腔。颗粒细胞聚集在尼龙线周围并将其包囊起来，作为一种自我防御反应。发现BmColIV是包囊的组成成分之一。此外，本研究还表明，在幼虫到蛹的变态过程中，积极表达BmColIV的颗粒细胞在中肠上皮周围聚集，并在那里形成富含BmColIV的厚基底膜样结构。
