Connective tissues of the periodontium. Research and clinical implications

Matrix Metalloproteinases in the Periodontium-Vital in Tissue Turnover and Unfortunate in Periodontitis

The extracellular matrix (ECM) is a complex non-cellular three-dimensional macromolecular network present within all tissues and organs, forming the foundation on which cells sit, and composed of proteins (such as collagen), glycosaminoglycans, proteoglycans, minerals, and water. The ECM provides a fundamental framework for the cellular constituents of tissue and biochemical support to surrounding cells. The ECM is a highly dynamic structure that is constantly being remodeled. Matrix metalloproteinases (MMPs) are among the most important proteolytic enzymes of the ECM and are capable of degrading all ECM molecules. MMPs play a relevant role in physiological as well as pathological processes; MMPs participate in embryogenesis, morphogenesis, wound healing, and tissue remodeling, and therefore, their impaired activity may result in several problems. MMP activity is also associated with chronic inflammation, tissue breakdown, fibrosis, and cancer invasion and metastasis. The periodontium is a unique anatomical site, composed of a variety of connective tissues, created by the ECM. During periodontitis, a chronic inflammation affecting the periodontium, increased presence and activity of MMPs is observed, resulting in irreversible losses of periodontal tissues. MMP expression and activity may be controlled in various ways, one of which is the inhibition of their activity by an endogenous group of tissue inhibitors of metalloproteinases (TIMPs), as well as reversion-inducing cysteine-rich protein with Kazal motifs (RECK).

FNDC5/irisin is expressed and regulated differently in human periodontal ligament cells, dental pulp stem cells and osteoblasts

OBJECTIVE

To examine the expression and regulation of fibronectin type III domain-containing protein 5/irisin (FNDC5/irisin) in primary human periodontal ligament (hPDL) cells, dental pulp stem cells (hDPCs) and osteoblasts (hOBs).

METHODS

FNDC5/irisin was identified in sections of paraffin embedded rat maxillae, cryo-sections of 3D cultured spheroids hPDL cells, hDPCs and hOBs, 2D cultured hPDL cells, hDPCs and hOBs by immunohistochemistry. The expression of FNDC5/irisin was identified by qPCR, followed by sequencing of the qPCR product. Regulation of FNDC5/irisin expression in hPDL cells, hDPCs and hOBs were evaluated after administration of different concentrations of irisin and all-trans retinoic acid (ATRA). qPCR and ELISA were used to identify expression and secretion of FNDC5/irisin in odontoblast-like differentiation of hDPCs.

RESULTS

FNDC5/irisin was confirmed to be present in rat periodontium and dental pulp regions, as well as in 2D and 3D cultured hPDL cells, hDPCs and hOBs. BLAST analyses verified the generated nucleotide alignments matched human FNDC5/irisin. FNDC5/irisin gene expression was enhanced during odontoblast-like differentiation of hDPCs whereas the secretion of the protein was decreased compared to control. The protein signals in rat periodontal and pulpal tissues were higher than that of alveolar bone, and the expression of FNDC5/irisin was differently regulated by recombinant irisin and ATRA in hPDL cells and hDPCs compared to hOBs.

CONCLUSIONS

FNDC5/irisin expression was verified in rodent periodontium and dental pulp, and in hPDL cells, hDPCs and hOBs. The FNDC5/irisin expression was regulated by recombinant irisin and ATRA. Finally, expression and secretion of FNDC5/irisin were affected during odontoblast-like differentiation of hDPCs.

Rheumatoid Arthritis among Periodontitis Patients in Baddi Industrial Estate of Himachal Pradesh, India: A Cross Sectional Study

AIM

To determine whether there is a relationship between periodontal disease and rheumatoid arthritis.

METHODS

A total of 1520 (852 - periodontal group; 668 - general group) individuals of 30-70 years age group and residents of Baddi industrial estate in Himachal Pradesh, India, were assessed for the prevalence of rheumatoid arthritis and Periodontal Disease (PD). The prevalence and severity of periodontitis were determined by recording the Community Periodontal Index (CPI) with loss of attachment, based on WHO guidelines (1997). The criteria considered for diagnosis of rheumatoid arthritis were as those given by American Rheumatism Association -1988. Frequency distributions for bivariate analysis and logistic regression for multivariate analysis were used for assessment of statistical association between variables.

RESULTS

In patients referred for periodontal treatment, the prevalence of rheumatoid arthritis was 4.4%. Females (3.2%) and subjects aged above 50 years (3.5%) showed a significantly higher prevalence in comparison to their counterparts (p<0.001). The odds of rheumatoid arthritis in females were nearly three times (OR=2.813) higher than those in males, which was also statistically significant (p<0.05).

CONCLUSION

The findings provide evidence of a relationship, suggesting that individuals with moderate to severe periodontal disease are at higher risk of suffering from rheumatoid arthritis and vice versa.

Control of periodontal infection reduces the severity of active rheumatoid arthritis

OBJECTIVE

To determine if eliminating periodontal infection and gingival inflammation affects the severity of active rheumatoid arthritis (RA) in patients with chronic inflammatory periodontal disease.

METHODS

Twenty-nine subjects with confirmed diagnosis of RA and mild-to-moderate chronic periodontitis of at least 3 years' duration were enrolled in the study. The activity of RA was assessed using the disease activity score test (DAS28). Seventeen subjects completing the study received periodontal treatment consisting of scaling/root planing and oral hygiene instruction; 12 subjects completing the study received no treatment. Participants continued their usual disease-modifying medications for RA without any changes in DMARD therapy during the study period. RA measurements, and periodontal indices were recorded at baseline and at 8 weeks for each participant. Mann-Whitney U and chi tests were used to test for significant differences in the severity of RA in the periodontally treated group compared with the untreated groups.

RESULTS

Ten of 17 subjects (58.8%) in the treated group and 2 of 12 subjects (16.7%) in the untreated group showed improvement in RA scores. There was a statistically significant difference in DAS28 (4.3 +/- 1.6 vs. 5.1 +/- 1.2) and erythrocyte sedimentation rate (31.4 +/- 24.3 vs. 42.7 +/- 22) between the treatment and the control groups.

CONCLUSION

Control of periodontal infection and gingival inflammation by scaling/root planing and plaque control in subjects with periodontal disease may reduce the severity of RA. This notion is supported by reported subjective improvement in treated patients.

Immunolocalization of glycosaminoglycans in ageing, healthy and periodontally diseased human cementum

The distribution of glycosaminoglycans in the extracellular matrix of human cementum was investigated in periodontally involved and periodontal disease-free teeth separated into eight different age groups (from 12 to 90 years), to investigate possible changes in the distribution of glycosaminoglycan species associated with ageing and periodontal disease. A standard indirect immunoperoxidase technique was used, with a panel of monoclonal antibodies, 2B6, 3B3, 5D4, and 7D4, that recognize epitopes in chondroitin-4-sulphate/dermatan sulphate (C-4S/DS), chondroitin-6-sulphate (C-6S), keratan sulphate (KS) and a novel sulphated chondroitin sulphate (CS) epitope, respectively. Intense positive staining for C4-S/DS was observed at the margins and lumina of almost all the lacunae and canaliculi in cellular cementum in all sections. Immunoreactivity to C6-S, KS and novel CS epitopes was limited to a proportion of lacunae and canaliculi in all sections, although C6-S and the novel CS epitopes were more widely distributed than KS. In acellular cementum, there was no demonstrable staining for any of the glycosaminoglycans except where periodontal ligament (Sharpey's) fibres insert; periodontal ligament fibres inserting in cellular cementum also demonstrated positive immunoreactivity. In addition, the cementoblasts on the outer root surface, as well as the pericellular areas around a proportion of these cells, demonstrated positive immunoreactivity. These results indicate that glycosaminoglycan species present in human cementum include C4-S, DS, C6-S, and novel sulphated CS epitopes. KS is also present in cementum but is limited to a more restricted proportion of lacunae and canaliculi. Regional differences in the distribution of glycosaminoglycans exist between the two cementum types, but no qualitative differences in that distribution were observed between the various age groups or between periodontally involved and periodontal disease-free teeth. The immunoreactivity observed in a proportion of lacunae after staining for C6-S, KS, and novel sulphated CS epitopes could suggest the existence of different cementocyte subpopulations.

Molecular size distribution analysis of human gingival proteoglycans and glycosaminoglycans in specific periodontal diseases

In order to determine the molecular-size distribution of gingival proteoglycans (PGs) and glycosaminoglycans (GAGs) both in periodontal health and disease states, gingival tissues were obtained from patients with early onset periodontitis (EOP) and adult periodontitis (AP) and also from periodontally healthy subjects. Gel filtration chromatography of gingival PGs revealed different profiles for periodontally diseased and healthy gingiva. Healthy gingiva was mainly composed of high-molecular size proteins and PGs, while diseased gingival tissue presented a decrease in high-molecular size PG forms and a shift towards low-molecular size proteins and PGs. This indicates the degradation of PG macromolecules during periodontal disease activity. Furthermore, this shift towards low-molecular size forms was more intense in EOP patients when compared to AP patients. Gel filtration of gingival GAGs also demonstrated depolymerization of GAGs, with low-molecular size GAGs being more intense in periodontally diseased gingiva, while healthy gingival GAGs profile was mainly composed of high-molecular size GAGs. Similar to the profile of gingival PGs, low-molecular size gingival GAGs were more prominent in gingival tissue from patients with EOP. These findings suggest that both PGs and GAGs, essential components of the extracellular matrix (ECM), are depolymerized during periodontal disease activity, which is more prominent in EOP. Since the basic feature of periodontal disease is matrix degradation, ECM components, more specifically PGs and GAGs, are likely to provide valuable information for a better understanding of periodontal disease activity.

Turnover in periodontal connective tissues: dynamic homeostasis of cells, collagen and ground substances

The connective tissues of the periodontium are composed of two soft tissues and two hard tissues--each of which has unique features. This review considers the constituents of normal, healthy periodontal connective tissues together with an appraisal of the changes in the connective tissue matrices of the periodontium which occur during the development of periodontitis. Recent developments in this field have paved the way for new and exciting vistas in periodontal diagnosis and regeneration which, ultimately, are two important goals in periodontal therapy.

The effect of glycosylaminoglycans on the mineralization of sheep periodontal ligament in vitro

The effect of removal of glycosylaminoglycans on the mineralization of sheep periodontal ligament was determined using enzyme digests followed by incubation in solutions supersaturated with respect to hydroxyapatite at pH 7.4. TEM revealed that control periodontal ligament remained unmineralized. However, tissue from which glycosylaminoglycans had been removed contained plate-like crystals arranged parallel to and within the collagen fibrils. Electron probe and electron diffraction studies suggested that the crystals were apatitic with a similar order of crystallinity to dentine, and a Ca:P ratio of 1.61. In addition, the glycosylaminoglycan content of periodontal ligament, cementum and alveolar bone was compared using cellulose acetate electrophoresis. Periodontal ligament contained predominantly dermatan sulfate while cementum and alveolar bone contained mostly chondroitin sulfate. A role for glycosylaminoglycans in maintaining the unmineralized state of the periodontal ligament is suggested. Control of expression of specific proteoglycan species on a spatially restricted basis is presumably central to this role.

Effects of cytokines on gingival fibroblasts in vitro are modulated by the extracellular matrix

Fibroblast function in gingival tissue is thought to be regulated by the local cellular environment--both the extracellular matrix and soluble factors. In an attempt to artificially re-create this situation fibroblasts have been cultured within 3-dimensional collagen gels in an environment more physiologically comparable to connective tissue. Using such a model we investigated the effects of the extracellular matrix on gingival fibroblast growth and synthetic activity and on the cellular responsiveness to 4 soluble factors--epidermal growth factor (EGF), platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-beta 1) and interleukin-1 beta (IL-1 beta). Fibroblasts cultured within collagen gels showed similar growth rates, an increased production of collagen but reduced levels of hyaluronan synthesis in comparison to cells in monolayer culture. Cellular responsiveness to soluble mediators was also modulated by the collagen matrix, with a generalised reduction in response by cells embedded within the matrix. The stimulatory effects of EGF and PDGF on cell growth in monolayer over a 14-day period were only found during the initial stages of culture within gels. Similarly the stimulation of matrix production by cells induced by TGF-beta 1 on plastic was reduced or even negated when cells were cultured in collagen gels. On plastic IL-1 beta significantly stimulated cell growth but had no effect on either collagen or hyaluronan production by fibroblasts. In gel cultures, this cytokine had no effect on cell proliferation, but significantly inhibited both collagen and hyaluronan synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)