Morphological features and functional properties of human fibroblasts exposed to Actinomyces viscosus substances

Connective tissue fibroblasts undergo cytopathic degenerative changes during certain long-term inflammatory diseases such as rheumatoid arthritis and periodontitis. The failure of inflamed tissues to repair properly may result from functional alterations of fibroblasts within the affected tissues. Numerous previous studies indicate that direct cytotoxicity by bacterial or other substances may be responsible for the cellular alterations observed in vivo. We have tested this hypothesis by exposing cultures of human diploid fibroblasts to homogenates of Actinomyces viscosus (a microorganism associated with periodontitis and capable of causing other chronic inflammatory diseases) and analyzing the effects on cell viability, morphology, and function. The cells bind and subsequently engulf relatively large quantities of the bacterial substances. These substances do not appear to be toxic to fibroblasts as determined by 51Cr release and microcytotoxicity assays, although there is a slight but significant decrease in protein synthesis (P less than 0.01) as measured by the incorporation of [14C]proline. However, collagen production was not altered, and the cytopathic alterations observed in diseased tissues in vivo did not occur in the exposed cells. These findings suggest that A. viscosus substances do not directly cause injury to connective tissue fibroblasts in periodontal disease but may, through cell-surface binding, mark these cells for subsequent immune-mediated damage.

Defective neutrophil chemotaxis in juvenile periodontitis

Neutrophil chemotaxis was evaluated in nine patients with juvenile periodontitis, with normal subjects and patients with the adult form of periodontitis as controls. Defective chemotactic responses were observed in neutrophils from seven of nine juvenile patients, and a reduced level of complement-derived chemotactic activity was demonstrated in serum from four patients. These determinations were normal in all the patients with adult periodontitis. Serum from five of the juvenile patients contained a heat-stable, non-dialyzable factor that markedly inhibited the chemotaxis of normal neutrophils. Thus the characteristic tissue destruction seen in juvenile periodontitis may be, at least in part, a consequence of a failure of host defense mechanisms.

Fibroblast heterogeneity and prostaglandin regulation of subpopulations

The effects of prostaglandin E(2) (PGE(2)) upon the synthesis of protein and DNA, and membrane transport of proline and thymidine, by human diploid fibroblasts were studied. At a concentration range of 1-10 muM, PGE(2) inhibited protein synthesis and membrane transport by 45-50%. Serum-activated DNA synthesis and thymidine transport were also inhibited by approximately 50% in cells made quiescent and synchronous by serum deprivation. To determine whether prostaglandin inhibits some of the cells completely or all of the cells partially, radioautographic and cell-counting experiments were done. In cultures pulse-labeled with [(3)H]thymidine 12-33 hr after serum activation, prostaglandin exposure reduced the number of labeled nuclei by 42%. Sixty-five hours after serum activation, the total cell numbers present in the PGE(2)-exposed cultures were reduced by 25%. Furthermore, in the fibroblast cultures derived from cells previously maintained in 10 muM PGE(2) for 14 days, PGE(2) had no effect on DNA synthesis, indicating that the PGE(2)-sensitive cells had disappeared from the cultures. Thus, PGE(2) appears to inhibit growth and synthesis of a subpopulation of cells while not affecting the remaining insensitive cells. Prostaglandins may play an important role in connective-tissue differentiation and in some pathologic alterations by regulating fibroblast subpopulations.

Effect of hormones on collagen metabolism and collagenase activity in the pubic symphysis ligament of the guinea pig

The ligament which forms between the pubic bones of the pregnant guinea pig offers a unique system for the study of hormonal regulation of connective tissue metabolism. During the 5 days prior to parturition the length and hydroxyproline content of the pubic symphysis increase threefold. In nonpregnant animals, ligament growth can be induced in an estrogen-primed animal only following the administration of the hormone relaxin. A further increase in length can be achieved when progesterone is also injected. Removal and culture of post-partum ligaments, which undergo a 75% reduction in length and hydroxyproline content by the fifth post-partum day, allowed the demonstration of high collagenase levels released into the media. In contrast, when ligaments from pre-partum period were cultured, low levels of collagenase were detected in the media. The rapid post-partum ligament resorption could be partially inhibited if estrogen was injected immediately following parturition, whereas progesterone or relaxin significantly impaired ligament resorption. In a corresponding fashion, when the collagenase levels of these ligaments were measured progesterone treatment was shown to inhibit collagenase activity markedly while estrogen was less effective. Relaxin however, appeared to have no direct inhibitory effect.

Biochemical characterization of collagens synthesized by fibroblasts derived from normal and diseased human gingiva

Fibroblasts obtained from healthy and diseased human gingiva were labeled with radioactive amino acids and the collagenous proteins synthesized were studied. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of untreated, reduced, and pepsin-treated proteins of the medium and cell extract showed that the collagenous proteins synthesized by these cells exist in the precursor form. Type I collagen was the chief constituent. In addition, cells from normal tissue synthesized type III collagen in amounts varying from 5 to 30%. Type III collagen was not detected in the cultures of fibroblasts from diseased tissue; however, an additional collagen fractionated between 2.5 to 5.0 M NaCl and accounted for 22 to 29% of the total. This collagen had an alpha1/alpha2 ratio of 8.6 and hydroxylysine/lysine ratio and cyanogen bromide peptide pattern were similar to that of alpha1[I]. It is concluded that the fibroblasts derived from disease gingiva synthesize a collagen of composition (alpha1)3, probably of type I.

Diphenylhydantoin (dilantin) gingival hyperplasia: drug-induced abnormality of connective tissue

Various degrees of gingival overgrowth may occur in individuals taking diphenylhydantoin, a drug used widely in the treatment of epilepsy. The tissue overgrowth is made up predominantly of collagen, and may therefore be a useful model for analysis of fibrosis and some other connective tissue abnormalities. Fibroblasts derived from the overgrown tissue exhibit a level of protein synthetic activity approximately twice that of comparable cells obtained from nonepileptic control individuals and from the gingiva of age-matched epileptics taking the drug but not exhibiting gingival enlargement. In addition, 20% of the protein synthesized by cells from the affected tissue is collagen, whereas collagen accounts for only about 11% of the total protein produced by control cells of both types. The drug appears to induce or select for fibroblasts characterized by enhanced levels of protein synthesis and collagen production. This alteration persists through several cell replications in vitro in the absence of drug.

Pathogenesis of inflammatory periodontal disease. A summary of current work

Chronic periodontitis, a common disease of microbial origin, is the major cause of tooth loss in adult humans. The disease serves as a convenient experimental model for analysis of many aspects of chronic inflammation. A consideration of currently available data has permitted the formulation of a new concept of the pathogenesis of this disease. The gingival tissues respond within 2 to 4 days to a beginning accumlation of microbial plaque with a classic acute exudative vasculitis which we have termed the initial lesion. This response, which includes loss of perivascular collagen, is comparable to that elicited in most other tissues subjected to acute injury and may be a consequence of the elaboration and release of chemotactic and antigenic substances by microbial plaque. Within 4 to 10 days, the early lesion develops. It is characterized by a dense infiltrate of lymphocytes and other mononuclear cells, pathologic alteration of fibroblasts, and continuing loss of the connective tissue substance. The structural features of the early lesion are consistent with those expected in some form of cellular hypersensitivity, and a mechanism of this kind may be important in the pathogenesis. The early lesion is followed by the established lesion which develops within 2 to 3 weeks and is distinguished by a predominance of plasma cells in the absence of significant bone loss. The established lesion, which is extremely widespread in humans and in animals, may remain stable for years or decades, or it may become converted into a progressive destructive lesion. Factors causing this conversion are not understood. In the advanced lesion, plasma cells continue to predominate although loss of the alveolar bone and periodontal ligament, and disruption of the tissue architecture with fibrosis are also important characteristics. The initial, early, and established lesions are sequential stages in gingivitis and they, rather than the advanced lesion which is manifest clinically as periodontitis, make up the major portion of inflammatory gingival and periodontal disease in humans.

Demonstration of a precursor-product relationship between soluble and cross-linked elastin, and the biosynthesis of the desmosines in vitro

Direct evidence showing that a soluble form of elastin is the precursor of cross-linked elastin was obtained from pulse-chase experiments using chick embryo aortas and by demonstrating the conversion of soluble elastin into cross-linked elastin in a cell-free system. Acetic acid extracts of embryonic chick aorta pulse-labeled with [14C]lysine contain two radioactive proteins of molecular weights 74,000 and 138,000 which have been identified previously as soluble elastin and the pro-alpha chain of collagen, respectively. In pulse-chase experiments, the radioactivity incorporated in the soluble elastin during the pulse with [14C]lysine disappeared during a 24-hour chase with [12C]lysine and 89% of that which disappeared was accounted for in the desmosines of alkali-insoluble elastin. The disappearance of the radioactivity from the soluble fraction and its appearance in the desmosines of elastin were inhibited by beta-aminopropionitrile, a specific inhibitor of the cross-linking enzyme lysyl oxidase. In addition in vitro experiments, it was shown that the radioactivity in the desmosines of elastin can arise from that present in an acid-soluble precursor protein. This precursor protein is soluble elastin, as demonstrated by the formation of desmosines when a homogeneous preparation of soluble elastin was incubated with purified lysyl oxidase.

Lymphokine-induced production and release of lysosomal enzymes by macrophages

MACROPHAGES ARE ASSOCIATED WITH MOST CHRONIC INFLAMMATORY LESIONS, AND THESE CELLS CONTAIN ENZYMES THAT ARE ABLE TO DESTROY CONNECTIVE TISSUE CONSTITUENTS. Normal lymphoid cells responding to a mitogen, phytohemagglutinin-P, release factor(s) that cause a marked increase in the size and enzyme content for mononuclear phagocytes maintained in culture. The stimulated macrophages, which by several criteria remain otherwise viable and healthy, selectively release large quantities of hydrolytic enzymes to the culture medium.

Histopathologic features of the initial and early stages of experimental gingivitis in man

The pathologic alterations occurring in the gingival tissues of humans immediately following the beginning of plaque accumulation have not heen elucidated previously. Seven males, 22--31 years of age, free of clinical manifestations of dental and periodontal disease, and exhibiting a Plaque Index score of zero for the previous 28 days served as subjects. Plaque control measures were discontinued for 8 days and biopsies were taken from the buccal marginal gingiva of the first premolars on days 0, 2, 4, and 8. Paraffin- and Epon-embedded section, treated with a variety of histochemical stains were analyzed microscopically and cell counts were done on 1-micron Epon section. At 2 and 4 days following the beginning of plaque accumulation, the vessels subjacent to the juctional epithelium exhibited vasculitis and alterations in the perivascular collagen. There was a statistically significant increase in the number of neutrophils residing in the junctional epithelium. By the end of the 8-day period, the number of small mononuclear cells, mostly lymphocytes, in the connective tissues had increased by 3-fold and the area of collagen fiber alteration by 4-fold. In addition, the number of fibroblasts per unit area of connective tissue decreased significantly. Thus, within the period of 8 days following the beginning of plaque accumulation, an early lesion exhibiting many features characteristic of delayed hypersensitivity develops.