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PubMedDate not supplied

Interaction of human liver connective tissue cells, skin fibroblasts and smooth muscle cells with collagen gels.

Interactions of liver connective tissue cells, skin fibroblasts and smooth muscle cells with collagen gels in vitro were studied and compared. Liver connective tissue cells showed the lowest rate of migration into the gel and the highest speed of gel contraction, reflecting their high adhesiveness to the substrate as compared to the other cell lines studied. The analysis of their ultrastructural morphology showed that liver connective tissue cells and smooth muscle cells developed cytoskeletal and cytoplasmic organelle polarities, in response to the contact with gel surface. This polarity was lost when cells were embedded in the gel. Skin fibroblasts did not show this characteristic, neither on top nor in the gel. Although liver connective tissue cells have been recognized as analogous to smooth muscle cells, they represent a defined cell population, present in fibrotic livers, with specific behavior and with particular relationship to the extracellular matrix.

Cell Line↗
PubMed1984

Histochemistry of connective tissue cells in subcutaneous adipose tissue of normal and decapitated pig fetuses.

Connective tissue cells that are histochemically and morphologically distinct from 'fibroblasts' are localized around developing hair follicles in the pig and rat. Immature adipose tissue is limited to small areas immediately around fully descended hair follicles in the rat hypodermis. In the present study, connective tissue around large nerves and blood vessels in fetal pig subcutaneous tissue was examined for the presence of enzymes typical of adipocytes. Samples from decapitated pig fetuses were studied so that the effects of an altered hormonal profile could be examined. Samples of dorsal subcutaneous adipose tissue were obtained from fetuses at 65, 70, 85, 90, 110, and 112 days of gestation. Fetuses were decapitated in utero at 45 days of gestation, and adipose tissue samples were obtained from these fetuses at 110 days of gestation. A close spatial relationship was observed between the growth of large blood vessels and nerves and fat cell cluster development in the older (greater than 70 days) fetuses. Connective tissue cells that were contiguous with fat cell clusters were histochemically identical to adipocytes. The lipid histochemistry of the reactive connective tissue cells (histochemically identical to adipocytes) was variable in young fetuses. In all 110-and 112-day-old fetuses, the reactive cells contained lipid, whereas the reactive cells in decapitated fetuses were devoid of lipid. The reactive connective tissue cells were not associated with capillaries and did not contain basement membranes. The histochemistry of these cells suggests that they respond to a particular hormonal or metabolic profile as do adipocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1978

Isolation and characterization of epithelial and connective tissue cells from rat palate.

Epithelial and connective tissue cells were isolated from rat palate by sequential enzymatic digestion. Differences between the two populations were noted with respect to proline uptake and incorporation, % collagen synthesized, effects of parathyroid hormone and metabolism of D-valine. From these studies it can be concluded that the cell populations are viable and distinct with respect to the biochemical parameters examined.

Animals↗
PubMed2004

TGF beta1 and PDGF AA override collagen type I inhibition of proliferation in human liver connective tissue cells.

BACKGROUND: A marked expansion of the connective tissue population and an abnormal deposition of extracellular matrix proteins are hallmarks of chronic and acute injuries to liver tissue. Liver connective tissue cells, also called stellate cells, derived from fibrotic liver have been thoroughly characterized and correspond phenotypically to myofibroblasts. They are thought to derive from fat-storing Ito cells in the perisinusoidal space and acquire a contractile phenotype when activated by tissue injury. In the last few years it has become evident that several peptide growth factors such as PDGF AA and TGF-beta are involved in the development of fibrosis by modulating myofibroblast proliferation and collagen secretion. The fact that during the development of chronic fibrosis there is concomitant deposition of collagen, a known inhibitory factor, and sustained cell proliferation, raises the possibility that stellate cells from chronic liver fibrosis patients fail to respond to normal physiologic controls. METHODS: In this study we address whether cells from fibrotic liver patients respond to normal controls of proliferation. We compared cell proliferation of primary human liver connective tissue cells (LCTC) from patients with liver fibrosis and skin fibroblasts (SF) in the presence of collagens type I and IV; TGF-beta, PDGF AA and combinations of collagen type I and TGF-beta or PDGF AA. RESULTS: Our results indicate that despite displaying normal contact and collagen-induced inhibition of proliferation LCTC respond more vigorously to lower concentrations of PDGF AA. In addition, we show that collagen type I synergizes with growth factors to promote mitogenesis of LCTC but not SF. CONCLUSIONS: The synergistic interaction of growth factors and extracellular matrix proteins may underlie the development of chronic liver fibrosis.

Cell Line↗
PubMed1990

Evaluation of connective tissue cell responses to orthopaedic implant materials.

We have developed an in vitro cell culture model to examine the interaction between connective tissue cells and orthopaedic implant biomaterials. Human connective tissue cells grown on different materials exhibit distinct responses in terms of attachment, morphology, proliferative capacity and matrix biosynthesis. Our results closely complement in vivo observations concerning biocompatibility and demonstrate the usefulness of this in vitro system for evaluating biomaterials. More importantly, this model can be used to define the specific cellular and biochemical processes that are responsible for the local tissue responses to orthopaedic implant materials.

Alloys↗
PubMed1984

Cultured endothelial cells produce multiple growth factors for connective tissue cells.

Cultured bovine aortic endothelial cells (BAEC) secrete into their medium a growth-promoting factor that stimulates many connective tissue cells in culture. We now report that this growth-promoting activity is due to at least two different proteins which are biochemically separable and immunologically distinct. Cation exchange chromatography (Carboxymethyl-Sephadex) of concentrated BAEC-conditioned medium yields two major peaks of growth-promoting activity which adsorb at pH 8 and elute with a salt gradient. One of these peaks contains as well a protein that inhibits the binding of radioiodinated platelet-derived growth factor (PDGF) to its receptor on target cells. The PDGF-like mitogen is purified approx. 25-fold by this chromatographic step. A second peak of mitogenic activity exhibits no binding to the PDGF receptor. Both the PDGF-like mitogenic activity and the PDGF-distinct mitogenic activity are highly cationic, stable to boiling, sensitive to beta-mercaptoethanol, and between 30 and 50 kD in molecular weight. Complementary studies with human umbilical vein endothelial cells in culture were performed. These human cells also produce both growth-promoting activity and a protein that binds to the PDGF receptor. The latter activity is greatly inhibited by a specific antiserum to human PDGF, whereas the growth-promoting activity of the conditioned medium is minimally affected. The degree of inhibition of the two activities is, however, quantitatively consistent: 3.5 ng of PDGF-like activity in the radioreceptor assay is inhibited, while 5 ng of PDGF-like activity in the DNA synthesis assay is inhibited. The data from the two species are consistent with the proposal that cultured endothelial cells produce at least two distinct mitogens, one of which is biochemically and immunologically related to PDGF.

Animals↗
PubMed1989

Retinoid-mediated induction of the fat-storing phenotype in a liver connective tissue cell line (GRX).

The GRX cell line is derived from murine liver connective tissue cells. It has myofibroblastic characteristics and can be induced to display a phenotype analogous to fat-storing (Ito) cells. Retinol-mediated induction of the fat-storing phenotype was studied in vitro. Based on the incorporation of radiolabelled acetate into cell lipids, cholesterol synthesis increased and phospholipid synthesis was modified shortly after the beginning of the induction, indicating an activation of pre-existing metabolic pathways. Triacylglycerol synthesis was increased only after a delay of 4 d, indicating the de novo induction of enzymes necessary for triacylglycerol metabolism. Retinol incorporation and conversion into retinyl esters were also considerably increased by previous incubation with retinoids. Retinoid-induced changes in GRX cells provide a model for studying in vitro the interconversion of liver connective tissue cells between the myofibroblastic and fat-storing phenotypes. This interconversion is considered to be one of the major control points of normal homeostasis and of pathological modifications of liver connective tissue.

Acetates↗
PubMed1981

[Microtubule-independent cell surface stabilization in normal and transformed connective tissue cells].

Effects of colcemid on the distribution of pseudopodial activity in both normal and transformed connective tissue cells was studied by means of phase contrast microscopy and time-lapse cinematography. It was shown that normal as well as transformed fibroblasts are able to stabilize their surface independently on the presence of colcemid, however, in transformed cells this ability is more expressed. Possible mechanisms of this stabilization of cellular surface, independent on microtubules is discussed.

Animals↗
PubMedDate not supplied

Stimulation of connective tissue cell growth by substance P and substance K.

Connective tissue cells proliferate actively when cultured in the presence of serum. Platelet-derived growth factor (PDGF), a basic protein of relative molecular mass approximately 30,000, has been identified as the major serum mitogen for these cells; its main physiological/pathophysiological role may be to initiate wound healing in connection with tissue injury. However, growth of cultured cells is also influenced by several other factors, including epidermal growth factor, fibroblast growth factor, insulin and somatomedins. Furthermore, Rozengurt and Sinnett-Smith recently showed that bombesin, a neuroendocrine peptide isolated from frog skin, stimulates DNA synthesis and cell division in cultures of a specific subtype of 3T3 cells. Substance P and substance K (also known as neurokinin A or neuromedin L) are mammalian peptides belonging to the tachykinin family. Substance P has been studied extensively; it is distributed widely throughout the central and peripheral nervous system, including primary sensory neurones, and can be released in the periphery from axon collaterals of stimulated pain fibres and contribute to the inflammatory response. Substance K is a member of the tachykinin family isolated from mammalian spinal cord; Nawa et al. determined the primary structure of two types of substance P precursors, one of which contained a sequence homologous to substance K, as well as the sequence of substance P. We report here that substance P and substance K stimulate DNA synthesis in cultured arterial smooth muscle cells and human skin fibroblasts, and that this stimulation is inhibited by the substance P-antagonist spantide.

Animals↗
PubMed1998

Mechano-sensing and mechano-reaction of soft connective tissue cells.

One main function of the connective tissues is to provide cells with a mechanically resistant attachment support required for survival, division and differentiation. All cells contain membrane-anchored attachment proteins able to recognize specific chemical motifs in the extracellular macromolecules forming the supporting scaffold, made of various types of collagen, adhesive glycoproteins, elastin, proteoglycans, etc... These cell-matrix interactions are mainly mediated by receptors of the integrins family, heterodimeric molecules made of an extracellular domain connected through a transmembrane sequence to an intracytoplasmic tail. Upon recognition of the extracellular ligand, the clustering and activation of the integrins result in the recruitment of a complex of proteins and formation of the focal adhesion plaque, containing both cytoskeletal and catalytic signaling molecules. Activation results in polymerization of actin and formation of stress fibers. These structures establish a physical link between the extracellular matrix components and the cytoskeleton through the integrins providing a continuous path acting as a mechanotransducer. This connection is used by the cells to perform their mechanical functions as adhesion, migration and traction. In vitro experimental models using fibroblasts in a collagen gel demonstrate that cells are in mechanical equilibrium with their support which regulates their replicative and biosynthetic phenotype. The present review discusses the molecular structures operating in the transmission of the mechanical messages from the support to the connective tissue cells, and their effect on the cellular machinery. We present arguments for investigating these mechanisms in understanding the perception of reduced gravity and the resulting reaction leading to microgravity induced pathologies.

Animals↗
PubMed2002

Novel cell-scaffold interactions encountered in tissue engineering: contractile behavior of musculoskeletal connective tissue cells.

Methods employed in the course of tissue engineering often offer unique opportunities to observe cell-matrix interactions that cannot otherwise be viewed. These observations may provide insights into cell behavior than can contribute important new knowledge about cell biology. One such set of observations led to the discoveries that musculoskeletal connective tissue cells express a contractile muscle actin isoform, alpha-smooth muscle actin, and can contract. This knowledge may help to explain how these cells generate forces required for certain physiological and pathological functions, and this information may inform future approaches to regulate this function to advance tissue engineering. Tissue engineering science is thus emerging as an importance force that can both contribute to cell and molecular biology and add to the fund of knowledge supporting the production of tissue in vitro or in vivo to improve the management of a wide variety of disorders.

Actins↗
PubMed1977

The villous stroma of the human placenta. I. The ultrastructure of fixed connective tissue cells.

In human placental villi the connective tissue is constructed by mesenchymal cells, small and large reticulum cells and fibroblasts. During early pregnancy mesenchymal cells dominate; starting with the third month of gestation the reticulum cells are in the majority within the terminal villi, the fibroblasts within the stem villi. Ultrastructurally intermediary types of cells can be differentiated. Together with reticular and collagenous fibres the reticulum cells form the basic architecture of the villous stroma during the first 2/3 of gestation: the "reticular type of stroma". This consists of a network of cells and fibres with fetal vessels fitted in between. The remaining interspaces form a fluid system of compartments in which Hofbauer cells are suspended. They are called stromal channels. During the last trimester these channels and the Hofbauer cells as well are progressively replaced either by voluminous masses of fibres ("fibrous type of stroma", mainly in the stem villi) or by sinusoidal enlargements of fetal capillaries ("sinusoidal type of stroma", mainly in the terminal villi).

Cell Differentiation↗
PubMed1975

[Ultrastructure of nuclear bodies in connective tissue cells of psoriatic lesions (author's transl)].

Electron microscopic observations were made in 6 psoriatic lesions of the skin. All specimens showed an increased number of nuclear bodies containing glycogen and lipids in the nuclear plasma of connective tissue cells. The results indicate an activation of connective tissue cell metabolism. They are discussed in connection with previously described signs of the participation of mesenchymal tissue in the psoriatic skin reaction. The increased metabolism could be part of a "nonspecific mesenchymal tissue reaction".

Adult↗
PubMed2003

Network organization of interstitial connective tissue cells in the human endolymphatic duct.

The human endolymphatic duct (ED) and sac of the inner ear have been suggested to control endolymph volume and pressure. However, the physiological mechanisms for these processes remain obscure. We investigated the organization of the periductal interstitial connective tissue cells and extracellular matrix (ECM) in four freshly fixed human EDs by transmission electron microscopy and by immunohistochemistry. The unique surgical material allowed a greatly improved structural and epitopic preservation of tissue. Periductal connective tissue cells formed frequent intercellular contacts and focally occurring electron-dense contacts to ECM structures, creating a complex tissue network. The connective tissue cells also formed contacts with the basal lamina of the ED epithelium and the bone matrix, connecting the ED with the surrounding bone of the vestibular aqueduct. The interstitial connective tissue cells were non-endothelial and non-smooth muscle fibroblastoid cells. We suggest that the ED tissue network forms a functional mechanical entity that takes part in the control of inner ear fluid pressure and endolymph resorption.

Connective Tissue Cells↗
PubMedDate not supplied

Musculoskeletal connective tissue cells with muscle: expression of muscle actin in and contraction of fibroblasts, chondrocytes, and osteoblasts.

The expression of the gene for a muscle actin in certain nonmuscle cells and the contraction of these connective tissue cells has been associated with several important physiological and pathological processes; the contraction of healing skin wounds and the contracture in Dupuytren's disease being two notable examples. Studies in recent years have shown that a much wider variety of connective tissue cells than previously considered, including cells in many of the musculoskeletal tissues, e.g., chondrocytes and osteoblasts, can express the gene for alpha-smooth muscle actin and can display contractile behavior. These findings suggest that muscle actin-enabled cell contraction may also be playing important roles in the other connective tissues comprising the musculoskeletal system, namely, tendon, ligament, meniscus, intervertebral disc, articular cartilage, and bone.

Actins↗