Synthesis of types I, III and AB2 collagen by chick tendon fibroblasts in vitro

Impact of isolation method on cellular activation and presence of specific tendon cell subpopulations during in vitro culture

Tendon injuries are common and heal poorly, due in part to a lack of understanding of fundamental tendon cell biology. A major impediment to the study of tendon cells is the absence of robust, well-characterized in vitro models. Unlike other tissue systems, current tendon cell models do not account for how differences in isolation methodology may affect the activation state of tendon cells or the presence of various tendon cell subpopulations. The objective of this study was to characterize how common isolation methods affect the behavior, fate, and lineage composition of tendon cell cultures. Tendon cells isolated by explant exhibited reduced proliferative capacity, decreased expression of tendon marker genes, and increased expression of genes associated with fibroblast activation compared to digested cells. Consistently, explanted cells also displayed an increased propensity to differentiate to myofibroblasts compared to digested cells. Explanted cultures from multiple different tendons were substantially enriched for the presence of scleraxis-lineage (Scx-lin+) cells compared to digested cultures, while the overall percentage of S100a4-lineage (S100a4-lin+) cells was dependent on both isolation method and tendon of origin. Neither isolation methods preserved the ratios of Scx-lin+ or S100a4-lin+ to non-lineage cells seen in tendons in vivo. Combined, these data indicate that further refinement of in vitro cultures models is required in order to more accurately understand the effects of various stimuli on tendon cell behavior. Statement of clinical significance: The development of informed in vitro tendon cell models will facilitate enhanced screening of potential therapeutic candidates to improve tendon healing.

In vitro study of novel collagenase (XIAFLEX®) on Dupuytren's disease fibroblasts displays unique drug related properties

Dupuytren's disease (DD) is a benign, fibroproliferative disease of the palmar fascia, with excessive extracellular matrix (ECM) deposition and over-production of cytokines and growth factors, resulting in digital fixed flexion contractures limiting hand function and patient quality of life. Surgical fasciectomy is the gold standard treatment but is invasive and has associated morbidity without limiting disease recurrence. Injectable Collagenase Clostridium histolyticum (CCH)--Xiaflex®--is a novel, nonsurgical option with clinically proven in vivo reduction of DD contractures but with limited in vitro data demonstrating its cellular and molecular effects. The aim of this study was to delineate the effects of CCH on primary fibroblasts isolated from DD and non-DD anatomical sites (using RTCA, LDH, WST-1, FACS, qRT-PCR, ELISA and In-Cell Quantitative Western Blotting) to compare the efficacy of varying concentrations of Xiaflex® against a reagent grade Collagenase, Collagenase A. Results demonstrated that DD nodule and cord fibroblasts had greater proliferation than those from fat and skin. Xiaflex® exposure resulted in dose- and time-dependent inhibition of cellular spreading, attachment and proliferation, with cellular recovery after enzyme removal. Unlike Collagenase A, Xiaflex® did not cause apoptosis. Collagen expression patterns were significantly (p<0.05) different in DD fibroblasts across anatomical sites - the highest levels of collagen I and III were detected in DD nodule, with DD cord and fat fibroblasts demonstrating a smaller increase in both collagen expression relative to DD skin. Xiaflex® significantly (p<0.05) down-regulated ECM components, cytokines and growth factors in a dose-dependent manner. An in vitro scratch wound assay model demonstrated that, at low concentrations, Xiaflex® enabled a faster fibroblast reparatory migration into the wound, whereas, at high concentrations, this process was significantly (p<0.05) inhibited. This is the first report elucidating potential mechanisms of action of Xiaflex® on Dupuytren fibroblasts, offering a greater insight and a better understanding of its effect in DD.

Deposition of collagenous matrices by tendon fibroblasts in vitro: a comparison of fibroblast behavior in pellet cultures and a novel three-dimensional long-term scaffoldless culture system

Tendons transmit tensile loads from muscle to bone. They consist primarily of parallel collagen fibers between longitudinally oriented rows of tendon fibroblasts. In this study, we describe a novel scaffoldless dialysis-roller culture system that allows tendon cells to form large, organized, tendon-like structures. We compare cell and collagen orientation and synthesis in these cultures with that of monolayer and high-density pellet cultures. Monolayers are unable to deposit a substantial matrix, losing most of their secreted collagen to the medium. High-density pellet cultures deposit more matrix, lose less to the medium, and become organized at their periphery but show signs of nutritional compromise in the center core. In the novel system, cells formed highly organized structures resembling embryonic tendons, synthesized much more collagen, and incorporated around 70% of the secreted collagen into the tendon-like extracellular matrix. The three-dimensional cultures appear to allow substantial cell-cell interactions and may mimic important aspects of the early development of tendons, including the formation of membrane-bound extracellular spaces to contain and organize the secreted collagen.

Isolation and characterization of a collagen-binding glycoprotein from chondrocyte membranes

A collagen-binding glycoprotein was isolated from purified chick chondrocyte surface membranes by affinity chromatography on type II collagen-Sepharose. The purified glycoprotein has an apparent mol. wt. of 31,000 and binds to native chick collagen types I, II, III, V and M. Although it contains 30% carbohydrates, the majority of which is fucose, it is hydrophobic and soluble only in detergents. The integral membrane protein character of the 31-K protein became apparent from its ability to insert into lecithin vesicles. Liposome-inserted 31-K protein binds 125I-labelled type II collagen in the presence of 0.5 M NaCl, while detergent-solubilized 31-K protein is dissociated from type II collagen by 0.05-0.1 M NaCl. Electron microscopic studies employing the rotary shadowing technique indicate that 31-K protein particles bind to the ends of collagen molecules. We propose that this glycoprotein serves as anchorage site for extracellular collagen to the chondrocyte membrane and thus may be involved in cell-matrix interactions in cartilage.

Regulations of collagen synthesis by ascorbic acid, transforming growth factor-beta and interferon-gamma in human dermal fibroblasts cultured in three-dimensional collagen gel are photoaging- and aging-independent

Decreased collagen synthesis and loss of responsiveness to growth factors are well known phenomena in in vivo or in vitro aged cells. Ascorbic acid and some cytokines such as transforming growth factor-beta and interferon-gamma are important regulators of collagen synthesis. To investigate the responsiveness of fibroblasts with regard to the photoaging and aging process, we examined the effect of ascorbic acid, TGF-beta, and IFN-gamma on collagen synthesis in dermal fibroblasts from three newborn foreskins (1 day old) and in both exposed and unexposed skin fibroblasts from 4 old individuals (60-76 years old) cultured in monolayer and in collagen gel. We demonstrated that basal levels of collagen synthesis decreased with increasing age. Photoaged fibroblasts in collagen gel showed greater basal collagen synthesis than aged fibroblasts in the same individuals, but similar basal collagen synthesis in monolayer cultures. Even though basal levels of collagen synthesis in collagen gel are downregulated in a photoaging- and aging-dependent manner, collagen synthesis by ascorbic acid in collagen gel, and by TGF-beta and IFN-gamma in both monolayer culture and collagen gel were regulated in a photoaging- and aging-independent manner. In monolayer culture, however, the responsiveness to ascorbic acid in newborn fibroblasts was greater than in photoaged and aged fibroblasts. Our results suggest that there are differences in collagen synthesis between photoaged and aged cells, depending on culture conditions. Responsiveness to ascorbic acid, TGF-beta and IFN-gamma related to collagen synthesis in photoaged and aged fibroblasts in collagen gel appears to be the same as in newborn fibroblasts, even though basal levels of collagen synthesis are downregulated in a photoaging- or aging-dependent manner.

Cloning and characterization of human gingival and periodontal ligament fibroblasts

Fibroblast heterogeneity in human periodontal tissues was characterized by cloning and immuno-histochemical techniques. Cell suspensions from primary cultures gingival (GF) and PDL fibroblasts (PF) were cloned. The relative intensity of double-labeled immunofluorescence, using specific antibodies to the extracellular matrix (ECM) molecules collagen type I (CI), type III (CIII), and fibronectin (Fn), was measured by photometry. Most clones derived from either GF or PF showed positive intracellular staining for both CI and Fn, and CIII and Fn. However, there were variations in fluorescence intensity for CI and Fn, ranging from relatively weak to strongly positive. The fluorescence for CI and CIII was relatively weak in most isolated GF clones in contrast to their PF clones. These observations coupled with studies of growth and cellular morphology in individual clones suggest that: 1) GF and PF contain functionally heterogeneous subpopulations; and 2) the synthesis and expression of extracellular matrix molecules of GF may be essentially different from that of PF.

Tendon collagens: extracellular matrix composition in shear stress and tensile components of flexor tendons

Outer synovial tissues were separated from the remainder of avian flexor tendon and the collagens characterized biochemically and compared with those of the internal portion of tendon and sheath. The collagen content of tendon synovium was 23%, whereas that of tendon and sheath were 78% and 73%, respectively, based on dry weight. Four genetic types of collagen were found in the pepsin solubilized matrices: in the synovium, types I (78%) and III (19%) predominated; types V and possibly VI were present as minor collagens. Purified synovial type V collagen was a heterotrimer, with chain composition [alpha 1(V)]2 alpha 2(V). In contrast, the internal portion of tendon and sheath were comprised of only type I collagen. There was a large amount (41%) of ethanol extractable, noncollagenous material present in synovium, a part of which was proteoglycans. In addition, collagen cross-links of these tissues were quantified: the internal tendon had an abundant concentration of pyridinoline; synovium exhibited high amounts of labile, reducible cross-links, particularly dihydroxylysinonorleucine. In the case of sheath, lysine aldehyde-derived cross-links appeared to be predominant. These results indicate that each tissue has its own collagen type distribution as well as cross-linking pattern reflecting their maturational and functional differences.

Restoration of the injured flexor tendon surface: a possible role for endotenon cells. A morphological study of the rabbit tendon in vivo

The ability of rabbit deep flexor tendons to restore the gliding surface and to heal, without the normal contribution of the superficial epitenon layer of the tendons, was studied by light and scanning electron microscopy. The epitenon layer was carefully removed from defined segments of the tendons. The remaining central tendon tissue was divided, sutured and placed in diffusion chambers subcutaneously in the back of the rabbits. After two weeks of culture, most of the sutured gaps were bridged and the tendons were encapsulated by flattened and spindle-shaped cells which covered a random network of thin collagen fibres. After five and 11 weeks, fibroblast-like cells in multiple layers formed a cobblestone-like surface. Thus, a tendon deprived of its epitenon layer still contains cells which can produce collagen, bridge the gap and restore the injured tendon surface.

Altered regulation of collagen metabolism in scleroderma fibroblasts grown within three-dimensional collagen gels

In systemic scleroderma (SSc) excessive deposition of collagen leads to fibrosis of various tissues including the skin. Previous studies have demonstrated that scleroderma fibroblasts in explant monolayer cultures are heterogeneous with respect to their levels of collagen synthesis. The critical role played by the extracellular matrix (ECM) in the modulation of fibroblast metabolism prompted us to study the regulation of collagen synthesis in scleroderma fibroblasts grown within three-dimensional collagen gels, a culture system representing more physiological conditions than monolayer cultures. Normal fibroblasts grown in this system dramatically reduce their collagen synthesis as compared to monolayer cultures. Quantification of total protein and collagen synthesis showed that scleroderma fibroblasts did not demonstrate the down regulation of collagen synthesis as observed in control fibroblasts, resulting in a much higher collagen synthesis in scleroderma fibroblasts compared to controls. However, also in this system scleroderma fibroblasts were heterogeneous in their response to the collagenous lattice. Ten strains were investigated, of which 3 were indistinguishable from controls, while 7 maintained higher levels of collagen production. In addition, our data showed that the changes in collagen synthesis on the protein level were accompanied by respective up- or downregulation on the mRNA level. These results indicate that an altered response to the surrounding ECM is an important factor in the disturbed regulation of connective tissue synthesis in scleroderma fibroblasts observed in vivo.

The collagen changes of Dupuytren's contracture

In Dupuytren's contracture there is an increase in the ratio of type III to type I collagen. The objective of this study was to determine if fibroblasts from patients with Dupuytren's contracture have an intrinsic aberration in collagen production or whether local factors govern the collagen changes in Dupuytren's contracture. Using a new collagen micro-method, we found that fibroblasts cultured from palmar fascia affected by Dupuytren's contracture produced similar collagen to fibroblasts derived from the palmar fascia of age- and sex-matched patients with carpal tunnel syndrome. Furthermore, the collagen changes of Dupuytren's contracture could be reproduced in all cell lines by increasing fibroblast density. At high fibroblast density, type I collagen production was inhibited: a finding that could account for the increased types III/I collagen ratio in Dupuytren's contracture. These results suggest that a genetic defect in collagen production is unlikely and that the important phenomenon is an increase in fibroblast density.

Muscarinic receptor expression in the primary culture of tracheal smooth muscle cells

Tracheal smooth muscle cells (TSMCs) were isolated from dog trachea in order to analyze the direct effects of growth factors and hormones on cell proliferation and muscarinic receptor (mAchR) expression. Dissection and dissociation of tracheal smooth muscle tissue with a collagenase I, deoxyribonuclease I and elastase IV mixture resulted in high yield and viability of TSMCs. A screen of growth factors, hormones, and serum concentration for the stimulation of cell growth, revealed that insulin-like growth factor, basic fibroblast growth factor, epidermal growth factor, insulin, transferrin, or hydrocortisone alone at the concentration used was not necessary or sufficient to stimulate growth of TSMCs in the primary culture with DMEM/F-12 containing 1% FBS. The regulation of cell surface mAchR expression in response to serum and cell growth in primary culture of TSMCs has been examined. In the presence of 1% serum, TSMCs withdraw from the cell cycle and express high levels of cell surface mAchRs. Exposure of quiescent TSMCs to 10% serum results in a loss of surface mAchRs. In addition, insulin-like growth factor, insulin or transferrin could stimulate the expression of mAchRs on TSMCs cultured in DMEM/F-12 containing 1% FBS. The results demonstrated that low serum concentration culture system may provide a useful model to elucidate the expression of mAchRs in the culture of TSMCs.

Cellular heterogeneity in cultured human chondrocytes identified by antibodies specific for alpha 2(XI) collagen chains

Collagen type XI is a component of hyaline cartilage consisting of alpha 1(XI), alpha 2(XI), and alpha 3(XI) chains; with 5-10% of the total collagen content, it is a minor but significant component next to type II collagen, but its function and precise localization in cartilaginous tissues is still unclear. Owing to the homology of the alpha 3(XI) and alpha 1(II) collagen chains, attempts to prepare specific antibodies to native type XI collagen have been unsuccessful in the past. In this study, we report on the preparation and use for immunohistochemistry of a polyclonal antibody specific for alpha 2(XI) denatured collagen chains. The antibody was prepared by immunization with the isolated alpha 2(XI) chain and reacts neither with native type XI collagen nor type I, II, V, or IX by ELISA or immunoblotting, nor with alpha 1(XI) or alpha 3(XI), but with alpha 2(XI) chains. Using this antibody, it was possible to specifically localize alpha 2(XI) in cartilage by pretreating tissue sections with 6 M urea. In double immunofluorescence staining experiments, the distribution of alpha 2(XI) as indicative for type XI collagen in fetal bovine and human cartilage was compared with that of type II collagen, using a monoclonal antibody to alpha 1(II). Type XI collagen was found throughout the matrix of hyaline cartilage. However, owing to cross-reactivity of the monoclonal anti-alpha 1(II) with alpha 3(XI), both antibodies produced the same staining pattern. Cellular heterogeneity was, however, detected in monolayer cultures of human chondrocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of collagen synthesis in fibroblasts within a three-dimensional collagen gel

Fibroblasts cultivated within a three-dimensional collagen gel display an elongated, spindle-like morphology, reduce their proliferation rate, contact the gel to a very dense tissue, and modify their metabolic activity as compared to monolayer cultures. Collagen synthesis measured as protein-bound hydroxyproline is reduced to 5% of the values found in monolayer culture. The reduction involving type I and type III collagen is due to decreased de novo synthesis and not to enhanced degradation. Dot blot hybridization, Northern blot analysis, and in situ hybridization using collagen I- and III-specific cDNA probes demonstrate that reduced biosynthesis rates are reflected by a marked reduction of pro alpha 1 (I), pro alpha 2 (I), and pro alpha 1 (III) collagen mRNA indicating pretranslational regulation. A similar reduction was observed for actin mRNA whereas levels of tubulin mRNA were similar for fibroblasts in monolayer culture or cultivated within the three-dimensional collagen gels. The data suggest a specific reprogramming of various cellular activities in response to contact with the reconstituted extracellular matrix.

Biosynthesis, secretion and extracellular localization of anchorin CII, a collagen-binding protein of the calpactin family

The amino acid sequence of anchorin CII, a collagen-binding protein isolated originally from chondrocyte membranes, was previously determined by sequencing of cDNA and proteolytic fragments of the protein. Computer analysis of the protein sequence revealed four internal repeats of approximately 70-80 residues, each containing a highly conserved consensus sequence of 17 residues. These repeats show considerable homology with sequences in human and bovine calpactin, lipocortin, endonexin and protein II, which are members of a family of Ca2+- and phospholipid-binding proteins, as well as major substrates of tyrosine kinases. While these proteins have been located at the inner side of the plasma membrane of fibroblasts and epithelial cells, here we present experimental evidence that anchorin CII is at least partially released from cells and binds to the outer cell surface. Biosynthesis studies in cell-free systems and in cell culture indicate that anchorin CII is not processed, which is consistent with the absence of signal sequences from the protein. Yet, pulse-chase experiments show that anchorin is released into the culture medium of fibroblasts after 30 min, and in chondrocyte cultures after 20 h. Anchorin CII was located to the outer cell surface of chondrocytes by lactoperoxidase-catalyzed cell surface iodination as well as by antibody labeling both at light- and electron-microscopical level. The pericellular localization of anchorin CII is consistent with the notion that this protein is involved in the interaction of chondrocytes and fibroblasts with extracellular collagen.

Collagen-type synthesis in human-hair papilla cells in culture

Hair-papilla derived cells were grown in monolayer culture and revealed the typical morphology and growth pattern which was similar but not identical to control fibroblasts. Hair-papilla cells were found to produce considerable amounts of collagen type I and type III and fibronectin. Type IV collagen production could not be detected. The ratio of collagen type III and type I clearly differed from the pattern observed in normal fibroblasts, being much higher in hair-papilla cells, where type III accounted for more than 20% of total collagen synthesis. These data show that hair-papilla derived cells have biosynthetic capacities similar to those of human skin fibroblasts as well as characteristic differences, indicating that they represent a specialized fibroblast subpopulation.

Systemic scleroderma. Clinical and pathophysiologic aspects

Systemic scleroderma is a generalized disease of connective tissue involving mainly the skin, the gastrointestinal tract, the lungs, the heart, and the kidneys. It can be present in different forms, of which acroscleroderma, with limited cutaneous and extracutaneous involvement, and diffuse scleroderma within a more rapid progression are most characteristic. Circulating antibodies against antinucleolar antigens are present in most patients with systemic scleroderma. They are helpful for establishing a classification and for determining the prognosis of the disease; their involvement in the pathogenesis, however, is still unclear. Alterations of the blood vessels and induction of fibroblasts by potent mediators are thought to play an important role in the early phase of scleroderma. Therefore early diagnosis is required, which then can initiate vasoactive therapy. In patients with systemic scleroderma, who also suffer from additional myositis, interstitial lung diseases, or arthritis, anti-inflammatory treatment with prednisolone and azathioprine is suggested. Development and progression of fibrosis cannot yet be influenced sufficiently. Only D-penicillamine affecting cross-linking of collagen has been widely used in scleroderma and has some beneficial effect.

Type III collagen can be present on banded collagen fibrils regardless of fibril diameter

Monoclonal antibodies that recognize an epitope within the triple helix of type III collagen have been used to examine the distribution of that collagen type in human skin, cornea, amnion, aorta, and tendon. Ultrastructural examination of those tissues indicates antibody binding to collagen fibrils in skin, amnion, aorta, and tendon regardless of the diameter of the fibril. The antibody distribution is unchanged with donor age, site of biopsy, or region of tissue examined. In contrast, antibody applied to adult human cornea localizes to isolated fibrils, which appear randomly throughout the matrix. These studies indicate that type III collagen remains associated with collagen fibrils after removal of the amino and carboxyl propeptides, and suggests that fibrils of skin, tendon, and amnion (and presumably many other tissues that contain both types I and III collagens) are copolymers of at least types I and III collagens.

Donor-age-related changes in the morphology, growth potential, and collagen biosynthesis in rat fibroblast subpopulations in vitro

Primary explant, mass and clonal fibroblast cultures established from BN rat skin and lungs were used to examine changes in cell behaviour associated with aging. Three distinct fibroblast cell types, i.e. FI, FII and FIII, could be identified on the basis of their morphological and proliferative properties. They could also be distinguished from each other by the amount and type of collagen they synthesized in clonal cultures. FI cells are diploid, spindle shaped and highly proliferative, and they synthesize low levels of type-I and -III collagen. Epithelioid FII cells are also diploid, proliferate slowly, and exhibited elevated collagen synthesis as compared to FI cells. FIII fibroblasts are large, stellate, tetraploid cells that proliferate more slowly than the other types but synthesize large amounts of collagen. In comparison to FI cells, the level of type-III-collagen synthesis is slightly elevated in FIII fibroblasts. In primary explant, mass and clonal cultures, the relative proportions of FI, FII and FIII cells were found to change as a function of the age of the donor animal. The increasing predominance of FIII cells in mass cultures of fibroblasts obtained from donors of increasing ages was consistent with the increased level of collagen synthesis in these cultures. Our observations indicate that the differentiation of normal BN rat fibroblasts occurs via a three-phase process. We discuss the age-related changes in the relative abundance of FI, FII and FIII cells in vivo in the context of alterations in fibroblast replacement and changes in connective tissue that occur during aging.

Modulation of collagen type synthesis in organ and cell cultures of fibroblasts

Fibroblast cultures are widely used to study abnormalities of collagen metabolism in both inborn and acquired diseases. However, there is reason to question the extent to which the experimental information obtained from in vitro culture systems in fact reflects the in vivo situation. In the present study we analyzed the proportions of collagens I and III synthesized by human and mouse skin fibroblasts maintained under various culture conditions. The amount of type III collagen extracted from skin specimens was lower than that which was newly synthesized in organ culture. Cells obtained by enzymatic disintegration of skin specimens synthesized more type III collagen than fibroblasts grown from explants. However, subcultivation of the enzymatically liberated cells resulted in a continuous decline of type III collagen production which eventually reached levels similar to those observed in explant cultures.

The extracellular matrix proteins laminin and fibronectin modify the AMPase activity of 5'-nucleotidase from chicken gizzard smooth muscle

Laminin and fibronectin, but not collagen, affect the AMPase activity of the purified transmembrane protein 5'-nucleotidase. Laminin stimulates whereas fibronectin inhibits the AMPase activity of this ectoenzyme. The AMPase-modulating effects by these components of the extracellular matrix require a preincubation period of several hours when detergent-solubilized 5'-nucleotidase is employed, they can, however, instantaneously be elicited with liposome-incorporated 5'-nucleotidase.

Hepatic lipocytes: the principal collagen-producing cells of normal rat liver

Hepatic lipocytes were isolated from normal rat liver and established in culture. A virtually pure isolate was obtained by fractionating enzymatically digested liver on a discontinuous gradient of arabinogalactan. Isolated cells displayed prominent rough endoplasmic reticulum and typical cytoplasmic droplets containing vitamin A. Lipocytes in primary culture were shown by immunofluorescence to secrete collagen types I, III, and IV and also laminin. Immunoassay of culture media showed that lipocytes during the first week in culture secrete type I (72.1-86.2% of total measured soluble collagen), type III (2.6-7.2%), and type IV (11.2-29.7%) collagens. Five percent of total secreted protein was collagen compared with 0.2% in similarly cultured hepatocytes and 1.7% in sinusoidal endothelial cells, as measured by the production of peptide-bound [3H]hydroxyproline in cells incubated with [3H]proline. The calculated amount of collagen synthesized by lipocytes per microgram of cellular DNA was 10-fold greater than that produced by hepatocytes and over 20-fold greater than that produced by endothelial cells. The findings indicate that collagen synthesis and secretion are specialized functions of hepatic lipocytes, and that, in cells from normal liver, this represents production primarily of type I collagen. The phenotypic resemblance of these cells to fibroblasts supports the hypothesis that lipocytes are a major source of collagen in pathologic fibrosis and may be precursors of the fibroblast-like cells observed in liver injury.

Dermatofibrosarcoma protuberans: altered collagen metabolism in cell culture

Dermatofibrosarcoma protuberans is a low-grade malignant tumor that grows invasively but rarely forms metastases. Its origin is still controversial. We characterized the synthesis of collagen in detail in cells which were obtained from dermatofibrosarcoma protuberans tumors by enzymatic tissue disintegration. Similar to fibroblasts, all tumor cell strains produced considerable amounts of collagen. However, the rate was reduced compared to normal skin fibroblasts. Cells grown from the tumors synthesized type I collagen, but no type II could be detected. After serial passaging the cultures started to produce type III collagen, which is probably due to a slow overgrowth by normal fibroblasts.

Coated vesicles purified from chick tendon fibroblasts contain newly synthesized type I procollagen

Coated vesicles were purified from embryonic chick tendon fibroblasts pulsed with [3H]proline. They were morphologically and biochemically similar to coated vesicles purified from other sources. Furthermore, they contained newly synthesized Type I procollagen which was protected from bacterial collagenase digestion unless detergent was present. The procollagen remained associated with coated vesicles during immune precipitation and agarose gel electrophoresis. Data from pulse-chase experiments demonstrated that the specific activity of the coated vesicle preparations was approx. 5-fold higher at the 10 min chase point than at either the 0 or 40 min chase points. These data are consistent with the hypothesis that coated vesicles are intermediates in the intracellular transport of newly synthesized Type I procollagen in chick tendon fibroblasts.

Collagen in the egg shell membranes of the hen

Collagen-like proteins have been found in the egg shell membranes of the hen. Materials similar to types I and V collagens were detected in each of the two layers of this membrane, the thick outer membrane and the thin inner membrane. Collagen was extracted by acid-pepsin digestion and isolated by differential salt precipitation. Identification of type-specific collagen-like material was established by coelectrophoresis on SDS-polyacrylamide gels using known collagen standards. These bands were susceptible to digestion by bacterial collagenase. From differential staining of the gels it was estimated that the ratio of collagen types I:V was approximately 100:1. Further confirmation of these biochemical results was obtained with immunofluorescence microscopy using type-specific antisera against chicken types I and V collagen with the indirect sandwich technique. Both the inner and outer shell membranes contained the two types of collagen. Within each membrane, the large, coarse 2.5-micron fibers contained predominantly type I collagen-like material, while type V collagen was mainly associated with the delicate narrower fibers of approximately 0.6-micron diameter. These tended to be concentrated in the inner membrane. At the electron microscopic level, both types of fibers were coated with glycoproteins that stained positively with ruthenium red. The deposition of these collagen-like substances by the hen oviduct on to the surface of the developing egg is an additional example of interstitial-type collagen synthesis and secretion by epithelial rather than by mesenchymal cells.

Effect of vitamin A and its derivatives on collagen production and chemotactic response of fibroblasts

Vitamin A and several other retinoids were added to fibroblast cultures in order to study possible alterations in biochemical properties and cellular responsiveness. The proliferation of cells was inhibited as the concentration of retinoids increased from 10(-9) to 10(-5) mol/l. Synthesis of non-collagenous proteins and production of both type I and type III collagen were decreased. The onset of type III collagen synthesis by tendon fibroblasts in culture was delayed. Furthermore, the chemotactic response of fibroblasts to fibroblast-conditioned medium was markedly reduced in the presence of retinoids (10(-6) to 10(-12) mol/l).

Serial observations and definition of mononuclear cell infiltrates in avian scleroderma, an inherited fibrotic disease of chickens

University of California, Davis (UCD) line 200 chickens develop an inherited connective tissue disease which includes fibrosis, vascular occlusion, and lymphocytic infiltration of skin, comb, and viscera. To further identify the nature of these features, tissue from both affected and control chickens, aged 7 days to 12 months, was serially examined using hematoxylin-eosin and Masson's trichrome stain. Mononuclear cell accumulations in skin were simultaneously characterized using mouse anti-chicken T and B cell specific monoclonal antibodies in a solid-phase immunoperoxidase assay; the same cells were also examined by direct immunofluorescence with fluoresceinated anti-chicken IgM and IgG, and stained for esterase and acid phosphatase. At 6 weeks of age, the majority of line 200 chicks manifested dermal fibrosis, cellular infiltrates, and vessel anomalies. In contrast, visceral involvement did not reach maximum incidence until 5 months of age with involvement of small intestine (60%), lungs (60%), and kidneys (65%), and not until 1 year for esophagus (64%), heart (30%), and testes (66%). Moreover, and of particular interest, was the threefold increment of full-thickness skin biopsies in line 200 birds. The cellular infiltrates in skin, found in 100% of affected line 200 chickens, were positive for B1, a mature B cell marker found on peripheral blood and bursal B cells; the majority of these same cells were found to bear surface IgM but not IgG. These data suggest that this syndrome may result from an alteration in collagen metabolism associated with a mature subpopulation of B lymphocytes.

Analysis of collagen types synthesized by rabbit ear cartilage chondrocytes in vivo and in vitro

This study compares the collagen types present in rabbit ear cartilage with those synthesized by dissociated chondrocytes in cell culture. The cartilage was first extracted with 4M-guanidinium chloride to remove proteoglycans. This step also extracted type I collagen. After pepsin solubilization of the residue, three additional, genetically distinct collagen types could be separated by fractional salt precipitation. On SDS (sodium dodecyl sulphate)/polyacrylamide-gel electrophoresis they were identified as type II collagen, (1 alpha, 2 alpha, 3 alpha) collagen and M-collagen fragments, a collagen pattern identical with that found in hyaline cartilage. Types I, II, (1 alpha, 2 alpha, 3 alpha) and M-collagen fragments represent 20, 75, 3.5, and 1% respectively of the total collagen. In frozen sections of ear cartilage, type II collagen was located by immunofluorescence staining in the extracellular matrix, whereas type I collagen was closely associated with the chondrocytes. Within 24h after release from elastic cartilage by enzymic digestion, auricular chondrocytes began to synthesize type III collagen, in addition to the above-mentioned collagens. This was shown after labelling of freshly dissociated chondrocytes with [3H]proline 1 day after plating, fractionation of the pepsin-treated collagens from medium and cell layer by NaCl precipitation, and analysis of the fractions by CM(carboxymethyl)-cellulose chromatography and SDS/polyacrylamide-gel electrophoresis. The 0.8 M-NaCl precipitate of cell-layer extracts consisted predominantly of type II collagen. The 0.8 M-NaCl precipitate obtained from the medium contained type I, II, and III collagen. In the supernatant of the 0.8 M-NaCl precipitation remained, both in the cell extract and medium, predominantly 1 alpha-, 2 alpha-, and 3 alpha-chains and M-collagen fragments. These results indicate that auricular chondrocytes are similar to chondrocytes from hyaline cartilage in that they produce, with the exception of type I collagen, the same collagen types in vivo, but change their cellular phenotype more rapidly after transfer to monolayer culture, as indicated by the prompt onset of type III collagen synthesis.

The effect of chronic inflammation on the composition of collagen types in human connective tissue

Biochemical alterations in the connective tissue matrix are a common feature of many diseases, and they account in major part for their functional impairment. Such alterations are especially important in acute and chronic inflammatory diseases where they may take the form of degradation of matrix components or their excessive accumulation leading to fibrosis. Although a wealth of morphologic information is available, very little is known about these changes at the biochemical level. Using human gingival tissue as a model, we have carried out studies aimed at assessing the effects of chronic inflammation on the collagen isotypes comprising the connective tissue matrix. Tissue obtained from patients undergoing surgical treatment for periodontitis was separated on the basis of clinical features into healthy and inflamed portions. After confirming the inflammatory status of each specimen histologically, each set of tissue pairs was extracted at 4 degrees C in 0.5 M acetic acid containing 1 mg/ml of pepsin, and the extracted collagens were fractionated with NaCl. Alpha chains were separated by polyacrylamide slab gel electrophoresis, and methods devised for their quantitation. The results showed that the proportions of type I and III collagens present in normal and inflamed tissues did not differ significantly. In contrast, the type V collagen, which accounted for 0.1 to 1.3% of the total collagens present in normal tissue, was increased by 2- to 9-fold in the chronically inflamed tissue. Because of the unique binding and connecting role type V collagen is thought to play, this alteration may have major pathologic and functional significance.

Attachment and extracellular matrix differences between tendon and synovial fibroblastic cells

Fibroblasts of the synovium of sheathed tendons were isolated, and their biochemical properties were compared with those of the fibroblasts of the remaining tendon. The synovial cells had a lower attachment efficiency than did the tendon cells. On the day of cell isolation the synovial cells synthesized collagen as 10% of their total protein, whereas the tendon cells synthesized 30% collagen. After growth in fetal bovine serum (FBS), the percentage of collagen synthesized by both populations decreased; however, the synovial cells still made less collagen than did the tendon cells (5 versus 11%). On the basis of cyanogen bromide peptide analysis, the synovial cells were found to synthesize Types I and III collagen in primary culture, whereas the tendon cells synthesized only Type I. The synovial cells also synthesized two to three times less sulfated glycosaminoglycans in culture than did the tendon cells. Thus, the two cell populations differed in attachment efficiency and in their biosynthesis of collagen and sulfated glycosaminoglycans. These differences reflect extracellular matrix differences that have been observed in the tendon in vivo. In addition, the results augment existing data showing that not all fibroblasts have identical phenotypes.

Relationship of cell growth to collagen synthesis in glucocorticoid treated A/J and C57BL6/J neonatal mouse dermal fibroblasts

Primary cultures of neonatal dermal fibroblasts from two strains of mice (A/J and C57BL6/J) were utilized as an in vitro system to investigate the effects of glucocorticoids on cell growth and collagen synthesis. Protein and DNA synthesis were lower in untreated (control) A/J fibroblasts than in C57BL6/J fibroblasts. Treatment with glucocorticoids for 4 days resulted in dose-dependent inhibition of [3H]thymidine incorporation into DNA and a reduction in collagen synthesis. Collagen synthesis was differentially more susceptible to glucocorticoids than was total protein synthesis. Neonatal dermal fibroblasts obtained from A/J mice were more sensitive to glucocorticoids than were cells from C57BL6/J mice. Reduction in collagen production by anti-inflammatory steroids in this system may be related to adverse effects observed in vivo following treatment with these steroids.

Multiple collagen gene expression with type III predominance in rat mucosal keratinocytes

Collagen synthesis in serially propagated cultures of rat mucosal keratinocytes (line RTK-I) was investigated. Analysis of biosynthetically labeled cell and media proteins retrieved after limited pepsin digestion revealed seven or eight collagen chains originating from four distinct collagens (types I, III, IV, V). Type III collagen was identified as the predominant species based on its electrophoretic and chromatographic behavior in the reduced and unreduced states, on the peptide pattern generated by limited cleavage with CNBr and with trypsin, and on the immunofluorescent detection of intracellular, collagen type III-reactive material. Evidence for the synthesis of two type IV collagen chains (155 k and 160 k after limited pepsin digestion) was provided by immunofluorescent and electrophoretic studies. Type V collagen was revealed by immunofluorescence, and two, possibly three, component chains were resolved in native type V collagen isolated from the harvest medium. Type I collagen, identified by comigration with authentic carriers, was a constant but quantitatively variable synthetic product. This study provides evidence that keratinocytes produce collagens normally found in mesenchymal matrices (type I and III) in addition to collagens characteristic of basement membranes (type IV) and of pericellular structures (type V). These findings reveal a hitherto unrecognized complexity and heterogeneity of the collagens synthesized by a highly differentiated epithelial cell type.

Difference in thermal stability of type-I and type-II collagen from rat skin

Type-I and type-III collagens were obtained by differential salt fractionation of neutral-salt-soluble collagen from rat skin. Their thermal stabilities were determined by u.v. difference spectroscopy. The ;melting' temperature (T(m)) in 5mm-acetic acid of type-III collagen was almost 2 degrees C above that of type-I collagen. Intramolecular covalent cross-linking had no effect on the thermal stability.

Synthesis of collagen type I, type I trimer and type III by embryonic mouse dental epithelial and mesenchymal cells in vitro

Epithelial and mesenchymal dental cells were grown in primary monolayer culture and the ability of both cell types to synthesize interstitial collagens was investigated. Pepsin-solubilized collagens were analyzed by CM-cellulose chromatography and both cell types were found to synthesize collagen type I, type III and type I trimer. The collagen phenotype of mesenchymal cells (type I: 82.4%, type III: 8.5%, type I trimer: 9.1%) was different from that of epithelial cells (type I: 71.8%, type III: 9.5%, type I trimer: 18.7%). The radioactivity incorporated into collagen molecules by mesenchymal cells was 34-times greater than the radioactivity incorporated by epithelial cells. This result agreed with previous observations obtained from tissue culture experiments (Lesot, H. and Ruch, J.V. (1979) Biol. Cell. 34, 23--37) which indicated a low synthesis of interstitial collagens by isolated dental epithelia when compared to isolated dental mesenchymes.