Growth and propagation of normal rat intestinal epithelial cells

Intestinal epithelial cells in vitro

Recent advances in the biology of stem cells has resulted in significant interest in the development of normal epithelial cell lines from the intestinal mucosa, both to exploit the therapeutic potential of stem cells in tissue regeneration and to develop treatment models of degenerative disorders of the digestive tract. However, the difficulty of propagating cell lines of normal intestinal epithelium has impeded research into the molecular mechanisms underlying differentiation of stem/progenitor cells into the various intestinal lineages. Several short-term organ/organoid and epithelial cell culture models have been described. There is a dearth of long-term epithelial and/or stem cell cultures of intestine. With an expanding role of stem cells in the treatment of degenerative disorders, there is a critical need for additional efforts to develop in vitro models of stem/progenitor epithelial cells of intestine. The objective of this review is to recapitulate the current status of technologies and knowledge for in vitro propagation of intestinal epithelial cells, markers of the intestinal stem cells, and gene and protein expression profiles of the intestinal cellular differentiation.

Mammalian intestinal epithelial cells in primary culture: a mini-review

Epithelial cells lining the digestive tract represent a highly organized system built up by multipotent stem cells. A process of asymmetric mitosis produces a population of proliferative cells that are rapidly renewed and migrate along the crypt-villus axis, differentiating into functional mature cells before dying and exfoliating into the intestinal lumen. Isolated crypts or epithelial cells retaining high viability can be prepared within a few h after tissue sampling. After cells are cultured in serum-free media, short-term studies (16-48 h) can be conducted for endocrinology, energy metabolism, or programmed cell death. However, long-term primary culture of intestinal cells (up to 10 d) is still difficult despite progress in isolation methodologies and manipulation of the cell microenvironment. The main problem in developing primary culture is the lack of structural markers specific to the stem cell compartment. The design of a microscopic multidimensional analytic system to record the expression profiles of biomarkers all along the living intestinal crypt should improve basic knowledge of the survival and growth of adult crypt stem cells, and the selection of totipotent embryonic stem cells capable of differentiating into intestinal tissues should facilitate studies of the genomic basis of endodermal tissue differentiation.

Mammalian intestinal epithelial cells in primary culture: a mini-review

Epithelial cells lining the digestive tract represent a highly organized system built up by multipotent stem cells. A process of asymmetric mitosis produces a population of proliferative cells that are rapidly renewed and migrate along the crypt-villus axis, differentiating into functional mature cells before dying and exfoliating into the intestinal lumen. Isolated crypts or epithelial cells retaining high viability can be prepared within a few h after tissue sampling. After cells are cultured in serum-free media, short-term studies (16-48 h) can be conducted for endocrinology, energy metabolism, or programmed cell death. However, long-term primary culture of intestinal cells (up to 10 d) is still difficult despite progress in isolation methodologies and manipulation of the cell microenvironment. The main problem in developing primary culture is the lack of structural markers specific to the stem cell compartment. The design of a microscopic multidimensional analytic system to record the expression profiles of biomarkers all along the living intestinal crypt should improve basic knowledge of the survival and growth of adult crypt stem cells, and the selection of totipotent embryonic stem cells capable of differentiating into intestinal tissues should facilitate studies of the genomic basis of endodermal tissue differentiation.

Regeneration of cultured midgut cells after exposure to sublethal doses of toxin from two strains of Bacillus thuringiensis

Toxin from two strains of Bacillus thuringiensis (Bt), AA 1-9 and HD-73, caused dose-dependent destruction of cultured midgut cells from Heliothis virescens larvae. HD-73 toxin was more effective although, at the doses used, not all cells were killed. After 2 days of exposure to 0.8 pg/µl AA 1-9 or 0.06 pg/µl HD-73, columnar and goblet cell numbers declined to ca 20% of controls. In contrast, stem and differentiating cells increased to 140-200% of controls. The dynamic of depletion and replacement depended on toxin type and concentration. Two days after toxin was washed out, ratios of cell types returned to approximate control levels, suggesting rapid population corrections in vitro. Regulation of the ratio of cell types in each population, and the rate of proliferation and differentiation of stem cells was induced by the cultured midgut cells themselves. Controls and cells treated with toxin from Bt strain AA 1-9 were stained using a polyclonal antibody to Lepidopteran midgut differentiation factor 1 (MDF1). With Bt toxin, 1.5 times more cells stained for MDF1, suggesting increased synthesis of this differentiation factor during increased stem cell differentiation. The response of cultured midgut cells to Bt toxin injury is similar to injured vertebrate tissues dependent on stem cells for replacement and healing.

Apoptosis in cultured midgut cells from heliothis virescens larvae exposed to various conditions

We exposed midgut cells from primary cultures of Heliothis virescens larvae to cell-free previously used medium, the Vaughn X and HyQ SFtrade mark media used for serum-free culture of insect cell lines which do not support H. virescens midgut cells, and to toxin from Bacillus thuringiensis. A statistically significant increase in the percent of dying cells was counted in cell populations in Vaughn X medium. Use of the TUNEL method to detect apoptosis indicated a low rate (7.2%) of apoptosis in control cultures grown in Heliothis medium, an increase to approximately 20% in previously used and HyQ SFtrade mark media, and to approximately 45% of cells remaining after exposure to and initial destruction by B. thuringiensis toxin. Apoptotic nuclei were predominant (approximately 6%) in mature columnar cells in control cultures. Approximately 1% of goblet, stem, and differentiating cells were apoptotic. However, apoptosis rose to 12% in stem and differentiating cells exposed to used and unsuitable medium. B. thuringiensis exposure to toxin for 2-3 days resulted in visible membrane damage and necrosis, causing the death of 84% of the cells as measured by both the TUNEL and Annexin methods. Some of the columnar cells and stem and differentiating cells that remained also contained apoptotic nuclei. Stem and differentiating cells normally replace dying mature cells in the midgut. Thus, exposure of cultures of H. virescens midgut cells to adverse environments such as unsuitable or poisonous media appeared to induce down-regulation of the cell populations by apoptosis.