Bone marrow mesenchymal stem cells differentiate into intestinal epithelioid cells through the ERK1/2 pathway.

BACKGROUND/AIMS: Previous studies have found that the injection of rat bone marrow mesenchymal stem cells (rBMSCs) in a mouse model of acute hepatic failure significantly relieves intestinal damage and endotoxemia. However, the mechanism of this process remains unknown. This study demonstrated the differentiation of rBMSCs into enterocyte-like cells and possible molecular mechanisms for this with the aim of finding a new treatment for intestinal epithelial injury and endotoxemia during liver failure. MATERIALS AND METHODS: rBMSCs were isolated from rat femurs and tibias. Differentiation was induced by co-culturing rBMSCs with rat intestinal epithelial cells (mIEC-6) using Transwell plates; after three, seven, and ten days of induction, expression of specific differentiation molecules were quantified. To inhibit the activity of the Mitogen-activated protein kinase 1/2 (ERK1/2) signaling pathway, an inhibitor of Mitogen-activated protein kinase kinase 1/2 (MEK1/2) was added to the co-culture medium, and western blot analysis was performed after 36 or 72 h to evaluate the expression of ERK1/2 signaling pathway markers (p-MEK1/2 and p-ERK1/2). RESULTS: The rBMSCs differentiated into enterocyte-like cells when co-cultured with mIEC-6 cells. Inhibition of ERK1/2 signaling abrogated the activity of MEK1/2, but MEK increased after 72 h, and the epithelioid differentiation of rBMSCs was consistent with the change in MEK expression. CONCLUSION: rBMSCs differentiate into intestinal epithelium after co-culture with mIEC-6 by regulation of the ERK1/2 signaling pathway. Further research is needed to elucidate the network of mechanisms.

Experimental leprosy: a model of epithelioid cell granuloma.

An animal model of granulomatous hypersensitivity has been developed, which reproduces some features of the pathologies of important chronic granulomatous disorders, including tuberculosis, tuberculoid leprosy, sarcoidosis, berylliosis, Crohn's disease, and sensitivity to zirconium. The lesions consist of focal collections of epithelioid cells surrounded by lymphocytes to form tubercles. The epithelioid cell has a secretory function and is not phagocytic. Plasmacytoid dendritic cells are precursors of epithelioid cells, which are therefore part of the innate immune system. Subplasmalemmal linear densities are also present in these cells. This autoimmune model has been induced in rabbits using a non-myelin sensory peripheral antigen to reproduce the features of tuberculoid leprosy. The antigen is probably present only in human tissue. A granuloma antigen, which is tissue specific similar to that in peripheral nerves, could be present in sarcoidosis and Crohn's disease. In multiple sclerosis, mononuclear cells in the brain parenchyma are not phagocytic and are therefore similar to epithelioid cells. The induction of tolerance leading to the development of a vaccine to prevent the lesions in multiple sclerosis, sarcoidosis, and Crohn's disease is possible after purification of the granuloma antigen.

Nucleolar organizer regions: their significance in protein synthesis and consequent release of factors that attract immature lymphocytes in different types of thymic epitheliocytes and in different stages of thymic development.

The thymus is a lymphoepithelial organ that has the central role in T-lymphocyte development. Unlike other lymphoid structures, where the supportive framework is chiefly collagenous reticular tissue, the thymus is permeated by a network of interconnected epithelial cells (thymic epitheliocytes) between which lodge lymphoid and other cells of the organ. There is much evidence that many distinctive functional roles are subserved by the thymic epitheliocytes such as, the differentiation of T lymphocytes, the production of soluble thymic factors or hormones, supportive functions, or their role in MHC restriction of T-cell immune responses. Nucleolar organizer regions (NORs), which are important for regulating protein synthesis, were identified in 30 fetal thymuses in different stages of development ( 10th, 14th, 15th, 19th, 20th, 23rd, 31st, and 35th week), by means of a silver (Ag) staining technique (AgNOR). The aim of our study was to estimate the AgNOR counts in the six different types of fetal thymic epitheliocytes, following suggestions that there may be a possible association between AgNOR values and consequent protein synthesis in the different types of these cells and in different stages of thymic development. The results showed that: First Type I epitheliocytes (subcapsular-perivascular) of the cortex represent a higher number of AgNORs in comparison with the other cellular types, a difference that was observed every week of our study, and especially between the 10th and 15th week of development (p < 0.01). The increased number of AgNORs in Type I epitheliocytes reflect their intense protein synthesis, a fact that explains the increased secretion of factors, e.g. beta2-microglobulin, that release immature lymphocytes from the yolk sac and the liver. Second, gradual increase of the average AgNOR in all thymic epitheliocytes from the 10th till the 35th week, without any statistical variation. This increase might be due to the intense functional activity of the whole number of epitheliocytes that participate in the proliferation, differentiation and issue in the circulation of mature T lymphocytes, which takes place after the 17th week of development. The 17-week thymus appears fully differentiated, and after this time it produces the main type of thymocyte also present throughout life (designated TdT +).

Diferenciación celular del epitelio mamario en cultivo / Cellular differentiation of the mammary epitelium in culture

The functional differentiation of mammary epithelial cells requires specific hormones, growth factors and chemical signals of the cellular environment. These signals consist in cell communication with the extracellular matirx and cell-cell interactions whic though an intrincated mechanism lead to the events that trigger milk secretion. The mammary epithelial cells HC!! from the cellular line COMMA-1D were cultured in the presence of lactogenic hormones such as insuline, dexametazone and prolactin and further stimulated with the epidermal growth factor. In these conditions the cell differentiated, presenting quantitative changes in shape and volume on their organelle cell structure. These cells synthesize betha casein and the intermediary filaments of keratin demonstrated by immunoblotting as well as electronic micrographies

The experimental granuloma. A hypothesis to explain the persistence of the lesion.

Granulomatous inflammation is the morphological substrate of a variety of important infectious diseases such as tuberculosis, leprosy, schistosomiasis and others. Nevertheless, although many aspects of this special type of inflammation are known, fundamental questions concerning granuloma formation, persistence, fate and significance for host-parasite relationships still remain to be elucidated. In this brief review, the basic and more relevant literature related to experimental investigations on granuloma physiopathology is presented. Based on recent investigations performed in our laboratory showing that MDF (Macrophage Deactivating Factor) secreted by epithelioid cells and characterized as the calcium-binding protein protein MRP-14 deactivates activated macrophages, a hypothesis to explain the persistence of granulomatous inflammation is put forward.

Hypotonic stress-induced release of KHCO3 in fused renal epitheloid (MDCK) cells.

Mechanisms of cell volume regulation induced by the reduction of the osmolality of the Ringer solution by one-third were studied in fused Madin-Darby canine kidney (MDCK) cells. Intracellular HCO3-, K+ and Cl- concentrations [ion]i in parallel with cell membrane potential (PD), cell membrane conductance (Gm) and conductances of individual ions (Gmion) were evaluated with microelectrode techniques. Fused cells regulate their cell volume by about 50%. Gm increased from 0.43 +/- 0.03 mS/cm2 in isotonic Ringer solution to 4.3 +/-0.3 mS/cm2 in the steady state phase of cell swelling. GmCl was 0.31 +/- 0.03 mS/cm2 in isotonic Ringer solution and thus was the dominant individual ion conductance. In the initial phase of cell swelling GmK increased transiently 64-fold to 0.32 +/- 0.03 mS/cm2, and consequently PD hyperpolarized. At peak hyperpolarization GmCl transiently decreased by 15%. Cell swelling increased GmCl 11-fold and GmHCO3 28-fold to 0.95 +/- 0.1 mS/cm2 in the steady state phase of cell swelling. In this phase GmCl and GmHCO3 were dominating, whereas GmK was only slightly increased compared to isotonic conditions. The hyperpolarization of PD was paralleled by cytoplasmic acidification. At peak acidification [HCO3-]i decreased by 6.4 mmol/kg H2O. Cl- extrusion was not detectable in the initial phase of cell swelling. In isotonic Ringer solution [K+]i was 125 +/- 5 mmol/kg H2O. During the initial phase of cell swelling 23 +/- 5 mmol/kg H2O K+ was extruded, indicating that yet unknown anions participated in cell volume regulation in this phase of cell swelling. In the steady state phase of cell swelling [pH]i was normalized by replenishing [HCO3-]i, whereas Cl- was extruded. We conclude that fused renal epitheloid cells acutely release KHCO3 in response to hypotonicity, but then regain pH homeostasis in the steady state phase of cell swelling.