Department of Agricultural Sciences, University of Naples "Federico II", Portici, NA, Italy.
Department of Biosciences, University of Milan, Milan, Italy.
Cell Tissue Res. 2019 Sep;377(3):505-525. doi: 10.1007/s00441-019-03076-w. Epub 2019 Jul 29.
The insect midgut epithelium represents an interface between the internal and the external environment and it is the almost unique epithelial tissue by which these arthropods acquire nutrients. This epithelium is indeed able to produce digestive enzymes and to support vectorial transport of small organic nutrients, ions, and water. Moreover, it plays a key role in the defense against pathogenic microorganisms and in shaping gut microbiota. Another important midgut function is the ability to produce signaling molecules that regulate its own physiology and the activity of other organs. The two main mature cell types present in the midgut of all insects, i.e., columnar and endocrine cells, are responsible for these functions. In addition, stem cells, located at the base of the midgut epithelium, ensure the growth and renewal of the midgut during development and after injury. In insects belonging to specific orders, midgut physiology is deeply conditioned by the presence of unique cell types, i.e., goblet and copper cells, which confer peculiar features to this organ. This review reports current knowledge on the cells that form the insect midgut epithelium, focusing attention on their morphological and functional features. Notwithstanding the apparent structural simplicity of this organ, the properties of the cells make the midgut a key player in insect development and homeostasis.
昆虫中肠上皮是内环境与外环境的界面，它是这些节肢动物获取营养物质的几乎唯一的上皮组织。事实上，这种上皮能够产生消化酶，并支持小分子有机营养物质、离子和水的向性运输。此外，它在抵御病原微生物和塑造肠道微生物群方面起着关键作用。中肠的另一个重要功能是产生信号分子，调节自身生理和其他器官的活动。所有昆虫中肠存在的两种主要成熟细胞类型，即柱状细胞和内分泌细胞，负责这些功能。此外，位于中肠上皮底部的干细胞确保了中肠在发育和损伤后的生长和更新。在属于特定目的昆虫中，中肠生理受到独特细胞类型（即杯状细胞和铜细胞）的存在的深刻影响，这赋予了该器官特殊的特征。本文综述了形成昆虫中肠上皮的细胞的最新知识，重点介绍了它们的形态和功能特征。尽管这个器官的结构表面上看起来很简单，但细胞的特性使中肠成为昆虫发育和体内平衡的关键参与者。
