Characterization of a spontaneously transformed pulmonary embryonic rat (PER) epithelial cell line

ADAM metallopeptidase with thrombospondin type 1 motif 2 inactivation reduces the extent and stability of carbon tetrachloride-induced hepatic fibrosis in mice

ADAMTS2 belongs to the "ADAM metallopeptidase with thrombospondin type 1 motif" (ADAMTS) family. Its primary function is to process collagen type I, II, III, and V precursors into mature molecules by excising the aminopropeptide. This process allows the correct assembly of collagen molecules into fibrils and fibers, which confers to connective tissues their architectural structure and mechanical resistance. To evaluate the impact of ADAMTS2 on the pathological accumulation of extracellular matrix proteins, mainly type I and III collagens, we evaluated carbon tetrachloride-induced liver fibrosis in ADAMTS2-deficient (TS2(-/-)) and wild-type (WT) mice. A single carbon tetrachloride injection caused a similar acute liver injury in deficient and WT mice. A chronic treatment induced collagen deposition in fibrous septa that were made of thinner and irregular fibers in TS2(-/-) mice. The rate of collagen deposition was slower in TS2(-/-) mice, and at an equivalent degree of fibrosis, the resorption of fibrous septa was slightly faster. Most of the genes involved in the development and reversion of the fibrosis were similarly regulated in TS2(-/-) and WT mice.

CONCLUSION

These data indicate that the extent of fibrosis is reduced in TS2(-/-) mice in comparison with their WT littermates. Inhibiting the maturation of fibrillar collagens may be a beneficial therapeutic approach to interfering with the development of fibrotic lesions.

Measurement of mechanical forces generated by skin fibroblasts embedded in a three-dimensional collagen gel

Mechanical activities developed by cells play a significant role in the embryogenesis, development, and physiopathology of pluricellular organisms. A technique is described to measure in vitro the traction force developed by cells seeded into a three-dimensional polymeric collagen lattice. It is based on the use of strain gauges generating an electrical signal upon tension that is amplified and recorded. The intensity of the signal depends on the number and type of cells, cytoskeleton integrity, concentration of collagen in the lattice support, and fetal calf serum in the culture medium. Skin fibroblasts from humans and animals produce traction forces ranging from 100 to 1000 mg per million cells. In the gel under tension, the cells are in mechanical dynamic equilibrium with their support. It is suggested that the mechanical activity of fibroblasts and the control of the tension that they operate on the lattice support participate in the structural organization of the dermis and in its physiologic tension.

Isolation and Maintenance of Continuous Cultures of Epithelial Cells from Chemically-injured Adult Rabbit Lung

Acute alveolar injury commonly occurs as a result of exposure to a variety of toxic stimuli and is characterised by widespread necrosis of the epithelium, followed by regeneration and hyperplasia of type II alveolar epithelial cells. We studied epithelial proliferation in rabbit lung resulting from a chemical stimulus by isolating the mitotically active cells and establishing them in continuous culture.

Acute alveolar injury was induced in rabbits with two daily injections of N-nitroso- N-methylurethane (NNNMU). Four to six days after treatment, the lungs were enzymatically digested and a homogeneous monolayer of epithelial cells was established in culture. The cells displayed a typical cobblestone-like arrangement and cuboidal shape, and represented 95% of the cells isolated. The cultures exhibited contact inhibition and achieved a population doubling level of 11 ± 2. Their epithelial origin was confirmed by positive reactions for immunofluorescent cytokeratin, alkaline phosphatase, and the Papanicolaou stain. Ultrastructurally, the cells showed abundant rough endoplasmic reticulum with dilated cisternae, desmosomes, cytokeratin filaments, and lamellar-like structures early in culture. In addition, the cells accumulated paraquat in a manner similar to that shown by established epithelial cell lines. The results demonstrate that regenerating epithelial cells can be isolated and propagated in culture as a relatively homogeneous population. This system, which is designed to further understanding of the metabolic role of epithelial cells following acute injury, may serve as an in vitro model for pulmonary toxicity studies using a minimal number of animals.

Antagonistic effects of laminin and fibronectin in cell-to-cell and cell-to-matrix interactions in MCF-7 cultures

During morphogenesis, tumor progression and metastasis, cell adhesion, dissociation, and migration result from a complex balance between cell-to-cell and cell-to-matrix interactions. Two different organization patterns of MCF-7 cells were induced by different extracellular matrix proteins. When plated on plastic or polymeric type I collagen gel used as a model of interstitial matrix, MCF-7 cells spread and grew in monolayer. When cultured on a solid gel of basement membrane (BM) proteins (85% laminin) used as a model of BM, cells formed clusters attached to the matrix. Matrix proteins regulated these two types of cell organization by preferentially promoting cell-to-cell or cell-support interactions. On plastic in the presence of soluble laminin or on laminin-coated dishes, cells also formed clusters. Addition of soluble fibronectin induced spreading of the cells, suggesting that laminin and fibronectin have competitive antagonistic effects on MCF-7 cell morphology. Antilaminin antibodies inhibited cluster formation and attachment, emphasizing the important role of this glycoprotein not only in promoting cluster attachment but also in cell-to-cell contact formation. Such effects of extracellular matrix proteins could play significant roles in tumor progression and metastasis.

Fibroblasts induce the assembly of the macromolecules of the basement membrane

The mechanism regulating the deposition of basement membrane components (BMCs) in a polymeric structure at the junction with the connective tissues is not yet understood. Cultures and cocultures of epithelial BMC-producing cells (L2 or PER cells) and fibroblasts were prepared in several experimental conditions and the organization of BMCs was studied by immunofluorescence. The pattern of BMCs in pure cultures of L2 or pulmonary epithelial rat (PER) cells consisted of intra- and extracellular granular deposits. At very high density, the cell contours were also underlined by a disrupted network of BMC deposits. A different fibrillar plexus--containing laminin, collagen type IV, and heparan-sulfate proteoglycan resistant to deoxycholate treatment and distant from the cell membrane--was observed in cocultures of L2 or PER cells with fibroblasts. Fibrils of fibronectin and/or collagen type I were most often dissociated from this plexus of BMCs. Similar results were obtained by adding a conditioned medium of L2 or PER cells to confluent fibroblasts, even when the cells were killed. Pure laminin also bound to the fibroblast layer. A coated film of fibronectin or polymeric collagen type I was unable to bind BMC provided by a conditioned medium. It is suggested that molecule(s) synthesized by fibroblasts and deposited in the pericellular matrix are involved in the assembly of BMCs.