Transporter mRNA Expression in a Conditionally Immortalized Rat Small Intestine Epithelial Cell Line (TR-SIE)

Primary cultures of mouse small intestinal epithelial cells using the dissociating enzyme type I collagenase and hyaluronidase

The epithelium is a highly dynamic system, which plays a crucial role in the homeostasis of the intestinal tract. However, studies on the physiological and pathophysiological functions of intestinal epithelial cells (IECs) have been hampered due to lack of normal epithelial cell models. In the present study, we established a reproducible method for primary culture of mouse IECs, which were isolated from the viable small intestinal crypts of murine fetuses (on embryonic day 19), using type I collagenase and hyaluronidase in a short span of time (≤20 min). With this method, continuously growing mouse IECs, which can be subcultured over a number of passages, were obtained. The obtained cell lines formed a tight cobblestone-like arrangement, displayed long and slender microvilli, expressed characteristic markers (cytokeratin 18 and Notch-1), and generated increasing transepithelial electrical resistance and low paracellular permeability during in vitro culture. The cells also had enzymatic activities of alkaline phosphatase and sucrase-isomaltase, and secreted various cytokines (IL-1β, IL-6, IL-8, and monocyte chemoattractant protein-1), responding to the stimulation of Escherichia coli. These results show that the primary-cultured mouse IECs obtained by the method established here had the morphological and immunological characteristics of IECs. This culture system can be a beneficial in vitro model for studies on mucosal immunology and toxicology.

Development of oral epithelial cell line ROE2 with differentiation potential from transgenic rats harboring temperature-sensitive simian virus40 large T-antigen gene

We have developed an immortalized oral epithelial cell line, ROE2, from fetal transgenic rats harboring temperature-sensitive simian virus 40 large T-antigen gene. The cells grew continuously at either a permissive temperature of 33°C or an intermediate temperature of 37°C. At the nonpermissive temperature of 39°C, on the other hand, growth decreased significantly, and the Sub-G1 phase of the cell cycle increased, indicating that the cells undergo apoptosis at a nonpermissive temperature. Histological and immunocytochemical analyses revealed that ROE2 cells at 37°C had a stratified epithelial-like morphology and expressed cytokeratins Krt4 and Krt13, marker proteins for oral nonkeratinized epithelial cells. Global-scale comprehensive microarray analysis, coupled with bioinformatics tools, demonstrated a significant gene network that was obtained from the upregulated genes. The gene network contained 16 genes, including Cdkn1a, Fos, Krt13, and Prdm1, and was associated mainly with the biological process of skin development in the category of biological functions, organ development. These four genes were validated by quantitative real-time polymerase chain reaction, and the results were nearly consistent with the microarray data. It is therefore anticipated that this cell line will be useful as an in vitro model for studies such as physiological functions, as well as for gene expression in oral epithelial cells.

Canine ABCB4: Tissue expression and cDNA structure

The ABCB gene subfamily of ABC (ATP-binding cassette) transporters is responsible for transporting a wide spectrum of molecules including peptides, iron, bile salts, drugs, and phospholipids. In humans, ABCB4 appears to be exclusively expressed on the apical membrane of hepatocytes where it translocates phosphatidylcholine from the inner to the outer leaflet of the canalicular membrane. Functional alterations in the ABCB4 transporter are associated with a number of cholestatic syndromes in humans. Because of its role in biliary lipid homeostasis in humans, investigation of the ABCB4 gene in dogs is warranted. Thus, the full cDNA sequence of canine ABCB4 was elucidated and its mRNA and protein expression levels in tissues were determined. Canine ABCB4 consists of 3804 nucleotides spanning 26 exons and is 89% identical to human ABCB4. Expression of ABCB4 in canine liver supports a potential role for the protein in normal biliary function similar to that in humans. The function of ABCB4 expressed in brain tissue has yet to be determined.

Peripheral nerve pericytes originating from the blood-nerve barrier expresses tight junctional molecules and transporters as barrier-forming cells

The objective of this study was to establish pure blood-nerve barrier (BNB)-derived peripheral nerve pericyte cell lines and to investigate their unique properties as barrier-forming cells. We isolated peripheral nerve, brain, and lung pericytes from transgenic rats harboring the temperature-sensitive simian virus 40 large T-antigen gene. These cell lines expressed several pericyte markers such as alpha-smooth muscle actin, NG2, osteopontin, and desmin, whereas they did not express endothelial cell markers such as vWF and PECAM. In addition, these cell lines expressed several tight junction molecules such as occludin, claudin-12, ZO-1, and ZO-2. In particular, the expression of occludin was detected in peripheral nerve and brain pericytes, although it was not detected in lung pericytes by a Western blot analysis. An immunocytochemical analysis confirmed that occludin and ZO-1 were localized at the cell-cell boundaries among the pericytes. Brain and peripheral nerve pericytes also showed significantly higher trans-pericyte electrical resistance values and lower inulin clearances than lung pericytes. We considered that occludin localized at the cell-cell boundaries among the pericytes might mechanically stabilize the microvessels of the BNB and the blood-brain barrier. Furthermore, we also showed that these cell lines expressed many barrier-related transporters. ABCG2, p-gp, MRP-1, and Glut-1 were detected by a Western blot analysis and were observed in the cytoplasm and outer membrane by an immunocytochemical analysis. These transporters on pericytes might facilitate the peripheral nerve-to-blood efflux and blood-to-peripheral nerve influx transport of substrates in cooperation with those on endothelial cells in order to maintain peripheral nerve homeostasis.

Endothelial cells constituting blood-nerve barrier have highly specialized characteristics as barrier-forming cells

In autoimmune disorders of the peripheral nervous system (PNS) such as Guillain-Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy, breakdown of the blood-nerve barrier (BNB) has been considered as a key step in the disease process. Hence, it is important to know the cellular property of peripheral nerve microvascular endothelial cells (PnMECs) constituting the bulk of BNB. Although many in vitro models of the blood-brain barrier (BBB) have been established, very few in vitro BNB models have been reported so far. We isolated PnMECs from transgenic rats harboring the temperature-sensitive SV40 large T-antigen gene (tsA58 rat) and investigated the properties of these "barrier-forming cells". Isolated PnMECs (TR-BNBs) showed high transendothelial electrical resistance and expressed tight junction components and various types of influx as well as efflux transporters that have been reported to function at BBB. Furthermore, we confirmed the in vivo expression of various BBB-forming endothelial cell markers in the endoneurium of a rat sciatic nerve. These results suggest that PnMECs constituting the bulk of BNB have a highly specialized characteristic resembling the endothelial cells forming BBB.

The immortalized cell lines with differentiation potentials: their establishment and possible application

Approximately 200 types of the cells are qualified as differentiated cells in the human body. If these different types of cells can be separated from each other (or cloned) and obtained in sufficient quantity, it will be beneficial for studying development, morphogenesis, tissue maintenance, cancer and aging, and for reconstructing functional tissues in vitro for regenerative medicine. We produced the transgenic mouse and rat harboring SV40 T-antigen gene to make the immortalized cell lines in the primary tissue culture and succeeded in establishing many functionally active cell lines from various tissues. Many immortalized cell lines from various tissues are shown to exhibit the unique characteristics of tissue functions and they should be useful as an in vitro model of various tissues for physiological and pharmacological investigations. Future application of these cells to drug screening is discussed.

Establishment and characterization of conditionally immortalized endothelial cell lines from the thoracic duct and inferior vena cava of tsA58/EGFP double-transgenic rats

The basic biology of blood vascular endothelial cells has been well documented. However, little is known about that of lymphatic endothelial cells, despite their importance under normal and pathological conditions. The lack of a lymphatic endothelial cell line has hampered progress in this field. The objective of this study has been to establish and characterize lymphatic and venous endothelial cell lines derived from newly developed tsA58/EGFP transgenic rats harboring the temperature-sensitive simian virus 40 (SV40) large T-antigen and enhanced green fluorescent protein (EGFP). Endothelial cells were isolated from the transgenic rats by intraluminal enzymatic digestion. The cloned cell lines were named TR-LE (temperature-sensitive rat lymphatic endothelial cells from thoracic duct) and TR-BE (temperature-sensitive rat blood-vessel endothelial cells from inferior vena cava), respectively, and cultured on fibronectin-coated dishes in HuMedia-EG2 supplemented with 20% fetal bovine serum and Endothelial Mitogen at a permissive temperature, 33 degrees C. A temperature shift to 37 degrees C resulted in a decrease in proliferation with degradation of the large T-antigen and cleavage of poly (ADP-ribose) polymerase. TR-LE cells expressed lymphatic endothelial markers VEGFR-3 (vascular endothelial growth factor receptor), LYVE-1 (a lymphatic endothelial receptor), Prox-1 (a homeobox gene product), and podoplanin (a glomerular podocyte membrane mucoprotein), together with endothelial markers CD31, Tie-2, and VEGFR-2, whereas TR-BE cells expressed CD31, Tie-2, and VEGFR-2, but no lymphatic endothelial markers. Thus, these conditionally immortalized and EGFP-expressing lymphatic and vascular endothelial cell lines might represent an important tool for the study of endothelial cell functions in vitro.