The regenerative nidi of the locust midgut as a model to study epithelial cell differentiation from stem cells

Abstract

SUMMARY A better knowledge of the regulatory mechanisms involved in stem cell proliferation and/or differentiation could reveal new methods for the treatment of some diseases. Most previous studies in the field of stem cell biology have been carried out on cultured isolated cells. In the case of adult tissue stem cells, mesenchymal bone marrow derived cells have been most widely studied, while the undifferentiated stem cells present in the epithelial tissues are less known. In order to advance further our understanding of epithelial tissue stem cells, new in vivo models are required. The present study focuses on the dynamics of a new and simple model of intestinal epithelial regeneration found in the midgut of the migratory locust, Locusta migratoria (Linnaeus 1758). The locust midgut consists of three cell types: columnar cells, endocrine cells and undifferentiated regenerative clustered cells. The undifferentiated epithelial midgut cells give rise to two other cell types and are located in a nest of regenerative cells known as regenerative niche. We have performed single and continuous bromodeoxyuridine (BrdU) administration experiments to study regeneration niches and their cellular dynamics. Immunocytochemistry and immunofluorescence techniques were used to detect the incorporation of BrdU into regenerative niches and the presence of FMRFamide-like immunoreactivity, as a marker for endocrine cell differentiation. Some isolated label retaining cells (LRC) were observed at the niche base 10-15 days after the final BrdU administration. We propose that these cells are the stem cells of this epithelial tissue. We also calculated the length of the cell cycle phases for a subpopulation of transit amplifying cells within the regenerative niche: G1, 2.5±0.5 h; S,5.5±0.5 h; G2, 0.75±0.25 h; M, 2.5±0.5 h. These amplifying cells will give rise to the columnar epithelial non-endocrine lineage. The differentiation of an endocrine cell from a niche stem cell occurs less frequently and thus leads to a lower proportion of endocrine cells as compared with epithelial columnar digestive cells (up to three endocrine cells per niche). Endocrine cell commitment seems to occur very early in the differentiation process within the niche, as double-labelled BrdU and FMRF endocrine cells have never been found. The only exception is the endocrine cells located in the ampullar region of the midgut, some of which show double immunostaining after long-term chronic BrdU injection. In summary, we have characterized a new and simple animal model of epithelial stem cell regeneration that may be useful for understanding the complex biological process that drives tissue renewal from undifferentiated and uncommitted progenitor cells.

Mitochondria in the midgut epithelial cells of sugarcane borer parasitized by Cotesia flavipes (Cameron, 1891)

“…Previous morphometric works show that these cells did not suffer alteration in cytoplasmic or nuclear volume during the parasitism process, in both midgut regions (Pinheiro et al, 2006), which was attributed to the high variability in the morphology of these cells, existent even in non-parasitized larvae . This variability of regenerative cells must be related to their function along the midgut; it is known that these cells may be differentiated in other epithelial cell types, presenting a high index of morphological variability (Lehane and Billingsley, 1996;Illa-Bochaca and Montuenga, 2006). However, as parasitism in D. saccharalis larvae did not bring an increase in cellular death of epithelial cells in the host insect midgut (unpublished data), the cellular reposition resultant from apoptosis is not necessarily altered by parasitism.…”

Beneficial interactions between insects and gut bacteria

“…Other than the intestinal stem cells (ISC), there are two other cell types which make up the insect gut epithelium -enterocytes, which make up the majority of cells and are mainly responsible for enzyme secretion and food absorption, and enteroendocrine cells, which secrete hormones like allatostatin, tachykinin etc. Further, these cells are connected by a network of neural crest cells, which maintain the peristalsis -churning movement of the gut [3].…”

Programmed cell death and stem cell differentiation are responsible for midgut replacement in Heliothis virescens during prepupal instar

“…Midgut replacement, which is accomplished by regenerative cells, has been reported not only in lepidopteran species (Judy and Gilbert 1970;Waku and Sumimoto 1971;Baldwin and Hakim 1991;Uwo et al 2002), but also in other insects, highlighting differences among taxa (Humbert 1979;Jiang et al 1997;Martins et al 2006). This epithelial replacement by regenerative cells has proved to be a useful model for studying stem cell biology and regulation Hakim et al 2001;Loeb et al 2003;Illa-Bochaca and Montuenga 2006).…”