Regulation of collagen production in fibroblasts cultured from normal and phenytoin-induced hyperplastic human gingiva

Hormesis: Wound healing and keratinocytes

Hormetic dose responses (i.e., a biphasic dose/concentration response characterized by a low dose stimulation and a high dose inhibition) are shown herein to be commonly reported in the dermal wound healing process, with the particular focus on cell viability, proliferation, and migration of human keratinocytes in in vitro studies. Hormetic responses are induced by a wide range of substances, including endogenous agents, numerous drug and nanoparticle preparations and especially plant derived extracts, including many well-known dietary supplements as well as physical stressor agents, such as low-level laser treatments. Detailed mechanistic studies have identified common signaling pathways and their cross-pathway communications that mediate the hormetic dose responses. These findings suggest that the concept of hormesis plays a fundamental role in wound healing, with important potential implications for agent screening and evaluation, as well as clinical strategies.

Role of the small GTPase activating protein IQGAP1 in collagen phagocytosis

Many adult connective tissues undergo continuous remodeling to maintain matrix homeostasis. Physiological remodeling involves the degradation of collagen fibers by the intracellular cathepsin-dependent phagocytic pathway. We considered that a multidomain, small GTPase activating protein, IQGAP1, which is involved in the generation of cell extensions, is required for collagen phagocytosis, possibly arising from its interactions with cdc42 and the actin-binding protein Flightless I (FliI). We examined the role of IQGAP1 in collagen phagocytosis by human gingival fibroblasts (HGFs) and by IQGAP1+/+ and IQGAP1-/- mouse embryonic fibroblasts. IQGAP1 was strongly expressed by HGFs, localized to vinculin-stained cell adhesions and sites where cell extensions are initiated, and colocalized with FliI. Immunoprecipitation showed that IQGAP1 associated with FliI. HGFs showed 10-fold increases of collagen binding, 6-fold higher internalization, and 3-fold higher β1 integrin activation between 30 and 180 min after incubation with collagen. Compared with IQGAP1+/+ fibroblasts, deletion of IQGAP1 reduced collagen binding (1.4-fold), collagen internalization (3-fold), β1 integrin activation (2-fold), and collagen degradation (1.8-fold). We conclude that IQGAP1 affects collagen remodeling through its regulation of phagocytic degradation pathways, which may involve the interaction of IQGAP1 with FliI.

Protective effects of thymoquinone on the healing process of experimental left colonic anastomosis

PURPOSE

Colorectal cancer is globally the third most common cancer. Anastomotic complications remain to be an important issue for colorectal surgery. The aim of this study was to investigate the protective effects of thymoquinone (TQ) on the healing process of left colonic anastomosis in an experimental model.

METHODS

Thirty-two male rats were divided into two groups, as the TQ group and the control group. TQ was administered to the TQ group, whereas the control group was given a standard feed and water for 2 wk. Following the creation of a left colonic anastomosis, subjects in both groups were sacrificed on the postoperative (PO) third and seventh days. Anastomotic burst pressures were measured mechanically. Immunohistochemical stainings for proliferating cell nuclear antigen, cluster of differentiation (CD) 31, CD45 were performed, and the matrix metalloproteinase-2 levels were measured. Histologic total scores were calculated according to Ehrlich-Hunt model. A value of P < 0.05 was considered as statistically significant.

RESULTS

One rat in the control group that died on the PO fourth day was excluded. Anastomotic burst pressures on the PO seventh day were higher in the TQ group than the control group (P < 0.01). Histopathological total scores on the PO third and seventh days were higher in the TQ group (P < 0.01). In addition, the TQ group revealed lower matrix metalloproteinase-2 scores on the PO third day and higher hydroxyproline levels on the PO seventh day (P < 0.05 and P < 0.01, respectively).

CONCLUSIONS

The use of TQ in colorectal surgery cases with left-sided colonic anastomosis resulted with increased anastomotic burst pressures and increased tissue hydroxyproline levels.

Immunoexpression of interleukin-6 in drug-induced gingival overgrowth patients

BACKGROUND

To analyze the role of proinflammatory cytokines in drug-induced gingival enlargement in Indian population.

AIM

To evaluate for the presence of interleukin-6 (IL-6) in drug-induced gingival enlargement and to compare it with healthy control in the absence of enlargement.

MATERIALS AND METHODS

Thirty-five patients selected for the study and divided into control group (10) and study group (25) consisting of phenytoin (10); cyclosporin (10) and nifedipine (5) induced gingival enlargement. Gingival overgrowth index of Seymour was used to assess overgrowth and allot groups. Under LA, incisional biopsy done, tissue sample fixed in 10% formalin and immunohistochemically evaluated for the presence of IL-6 using LAB-SA method, Labeled- Streptavidin-Biotin Method (LAB-SA kit from Zymed- 2(nd) generation LAB-SA detection system, Zymed Laboratories, CA). The results of immunohistochemistry were statistically analyzed using Kruskaal-Wallis and Mann-Whitney test.

RESULTS

The data obtained from immunohistochemistry assessment shows that drug-induced gingival overgrowth (DIGO) samples express more IL-6 than control group and cyclosporin expresses more IL-6 followed by phenytoin and nifedipine.

CONCLUSION

Increased IL-6 expression was noticed in all three DIGO groups in comparison with control group. Among the study group, cyclosporin expressed maximum IL-6 expression followed by phenytoin and nifedipine.

Effect of Ginkgo biloba Extract (EGb 761) on the Healing of Left Colonic Anastomoses in Rat

BACKGROUND

The aim of this study was to assess the effect of Ginkgo biloba extract (EGb 761) on healing of experimental colonic anastomoses in a rat model.

METHODS

Rats were divided into four groups: postoperative day (POD) 3 untreated control group, POD 3 EGb 761 group, POD 7 untreated control group, and POD 7 EGb 761 group. In the oral EGb 761 groups, the agent was given at 9.6 mg daily per orogastric route using a 4-F fine feeding catheter. We measured bursting pressures and hydroxyproline content and histologically examined the resected anastomoses on POD 3 and POD 7.

RESULTS

The bursting pressures increased more in the EGb 761 group than in the untreated control group on POD 3, but this difference was not statistically significant. Hydroxyproline content was higher in the EGb 761 group than in the untreated control group on POD 3, and this difference was statistically significant. Anastomosis bursting pressure values and hydroxyproline contents were significantly higher in the EGb 761 group than in the untreated control group on POD 7. Histological examination showed greater fibroblastic activity in the EGb 761 group than in the untreated control group on POD 3. There was no significant difference in anastomotic polimorphonuclear leukocyte, mononuclear cells and blood vessel neodevelopment between the POD 3 groups, but there was significant difference in fibroblastic activity and blood vessel neodevelopment between the POD 7 groups.

CONCLUSIONS

These results showed us that EGb 761 administration resulted in enhanced stability of colonic anastomoses during the first postoperative week.

Impaired degradation of matrix collagen in human gingival fibroblasts by the antiepileptic drug phenytoin

BACKGROUND

Gingival overgrowth (GO) is a serious adverse effect associated with the administration of phenytoin (PHT), with PHT-induced GO characterized by a massive accumulation of extracellular matrix components, especially collagen, in gingival connective tissues. However, the etiology of such collagen accumulation is still largely unknown. We examined the effects of PHT on the collagen degradation process leading to collagen accumulation in human gingival fibroblasts (HGF).

METHODS

HGFs were cultured with various concentrations of PHT and viable cell numbers and collagen amounts were determined. Gene and protein expressions of matrix metalloproteinases (MMP) and tissue inhibitors of MMPs (TIMP) were quantified with reverse transcription-polymerase chain reaction (RT-PCR) analyses and Western blotting, respectively. Cellular endocytosis of collagen was assayed using flow-cytometric analysis. The effects of PHT on extracellular signal-regulated kinase 1/2 (ERK1/2) and inhibitor kappaB-alpha (IkappaB-alpha) were assayed.

RESULTS

The proliferation of HGFs was not affected by PHT, whereas it significantly increased collagen accumulation. Further, the expressions of MMP-1, -2, and -3 were markedly suppressed by PHT, whereas that of TIMP-1 was induced in a dose- and time-dependent manner. PHT also markedly prevented collagen endocytosis by HGFs, which was associated with the suppression of alpha2beta1-integrin expression. In addition, the phosphorylation of ERK1/2 and IkappaB-alpha degradation were suppressed by PHT.

CONCLUSIONS

These results suggest that PHT causes an impaired degradation of collagen by suppression of enzymatic degradation with MMPs/TIMP-1 and alpha2beta1-integrin-mediated endocytosis. Those alterations are likely mediated through the cellular signaling pathways of ERK1/2 and nuclear factor kappaB. These synergistic effects may cause collagen accumulation, leading to GO.

Positive effects of phenytoin on experimental colonic anastomoses

BACKGROUND AND AIMS

Anastomotic dehiscence following colorectal surgery is a significant cause of morbidity and mortality. Phenytoin has wound-healing promoting and collagenase inhibitory effects. This study assessed these effects on healing of experimental colonic anastomoses in a rat model.

MATERIALS AND METHODS

Ninety Wistar rats weighing 240-290 g were divided into six groups: 3rd-day control group (n=15), 3rd-day oral administration of phenytoin (n=15), 3rd-day rectal administration of phenytoin (n=15), 7th-day control group (n=15), 7th-day oral administration of phenytoin (n=15), and 7th-day rectal administration of phenytoin (n=15). In oral phenytoin groups the agent was given at 10 mg/kg daily per orogastric route by 4-F fine feeding catheter; in rectal phenytoin RAP groups the agent was administered at 10 mg/0.5 cc daily to the anastomoses transrectally via a fine anal catheter.

RESULTS

There were significantly higher anastomosis bursting pressure values and hydroxyproline contents in phenytoin groups than in controls. In histopathological examination it was seen that phenytoin treatment caused greater collagen deposition, fibroblast, and blood vessel ingrowth than in controls. Immunohistochemical analysis showed the stimulatory effect of phenytoin in expression of vascular endothelial growth factor and basic fibroblast growth factor. Anastomosis bursting pressure, histopathological analysis, hydroxyproline content, and immunohistochemical results were better in the groups with rectal administration than in those with oral administration.

CONCLUSION

These results had showed us that phenytoin administration resulted in enhanced stability of colonic anastomoses during the first postoperative week and rectal administration showed better results than oral administration.

Effect of Sodium Diphenylhydantoin on Skin Wound Healing in Rats

This study evaluated the effect of phenytoin (sodium diphenylhydantoin) on skin wound healing in a rat model. The study was divided into two parts. In part I, 20 mul of phenytoin (10 mg/ml) was subcutaneously injected into the 3-cm dorsal full-thickness incisional wounds of 14 rats on postoperative days 0, 3, and 6. Twelve rats that received saline injections were used as the controls. The skin samples were harvested and tested for tensile strength and histology. An additional 12 rats with the same incisional wounds were tested for chemokine gene expressions. In part II, 20 mul of phenytoin (10 mg/ml) was applied topically once a day on a 4 x 4 cm area of the open dorsal wounds of 10 rats. Saline was applied to the wounds of the 10 control group rats. The wounds were measured weekly. The results showed that the average tensile strength of the phenytoin-treated wound was 0.49 +/- 0.08 MPa compared with the control group at 0.02 +/- 0.01 MPa (p < 0.05). The density ratio of chemokine monocyte chemotactic protein (MCP-1) to beta-actin in the phenytoin-treated group was also significantly higher than in the control group (p < 0.05). Histologic analysis of the phenytoin group showed a large amount of fibroblast proliferation, collagen synthesis, and neovascularization. Phenytoin-treated wounds were also smaller at 1 to 6 weeks postoperatively than the control group wounds. The authors conclude that the administration of phenytoin can promote wound healing and significantly increase MCP-1 expression. Phenytoin-treated wounds showed significant increase in collagen deposition and neovascularization, which resulted in an increased wound tensile strength and accelerated healing of both open and closed wounds.

Effect of nicotine-treated epithelial cells on the proliferation and collagen production of gingival fibroblasts

BACKGROUND, AIMS

Several in vitro and in vivo studies have indicated that tobacco smoking may be an important risk factor for the development and severity of inflammatory periodontal disease.

METHOD

In the present study, we developed an in vitro model to study the interactions between nicotine-treated epithelial cells (EC) and gingival fibroblasts (GF) derived from the same patient. EC were treated with nicotine concentrations varying from 1 microg/ml to 500 microg/ml and their effect on different functions of GF was studied. The proliferation of GF was evaluated by the incorporation of 3H-thymidine. A dose-dependent inhibition was observed with nicotine concentrations > or =100 microg/ml. Similar results were observed when studying the total protein synthesis of GF by incorporation of 3H-proline into non-dialyzable material.

RESULTS

When collagen production was evaluated by 3H-proline incorporation into collagenase-sensitive protein, a dose-dependent reduction was observed: the degree of inhibition varied from 25% with 50 microg/ml nicotine, to almost 60% with 500 microg/ml. Interestingly, the production of non-collagenous proteins decreased by almost 50% only when EC were treated with the highest concentration of nicotine.

CONCLUSIONS

The results suggest that epithelial cells, acting as mechanical barrier, can reduce but not completely eliminate the deleterious effect of nicotine on gingival fibroblasts.

Differential proliferation of fibroblasts cultured from hereditary gingival fibromatosis and normal gingiva

Hereditary gingival fibromatosis (HGF) is an oral condition characterized by the enlargement of the gingiva of both the maxilla and mandible. To study the cell proliferation index of fibroblasts from HGF and normal gingiva (NG), cell cultures from 4 members of the same family with HGF and from 4 healthy patients were established. Our results obtained from 6 different cell proliferation assays clearly showed that the cell proliferation rate was significantly higher in fibroblasts from HGF than from normal gingiva. HGF and control fibroblasts in subconfluent culture densities were typically spindle, but in saturation density HGF cells were shorter than control cells. These data suggest that the higher proliferative index of HGF fibroblasts possibly has a role in the pathogenesis of gingival outgrowth in HGF patients.

Nifedipine-induced gingival overgrowth in rats: brief review and experimental study

The first case report of gingival overgrowth induced by nifedipine (NIF), a calcium-beta blocker, was in 1984. However, the association between gingival alterations and the drug therapy of sodium diphenyl hydantoinate was initially described in 1939. The purpose of the experimental study was to examine the effect of NIF on gingival morphology in an animal model. Forty-five male Sprague-Dawley rats were randomly divided into 3 groups. Animals in each group daily received NIF in dimethyl sulfoxide by gastric feeding at a dosage of 0 (control), 30, or 50 mg/kg body weight for 9 weeks. Gingival gross morphology was assessed tri-weekly from stone models obtained from the mandibular incisal region. Animals were sacrificed at the end of study and tissue blocks were processed for histopathologic and histometric evaluation. Histometric analysis was performed at 5 selected tissue levels. Macro- and microscopic significantly increased gingival dimensions were demonstrated in NIF-treated animals compared to control. Although a fibrovascular tissue was observed in the tooth-gingiva interface for both NIF-treated and control animals, it was thicker and appeared earlier in NIF-treated animals. The results of the present study suggest that gingival overgrowth can be induced by NIF in rats and that the gingival overgrowth appears dose dependent.

Medication induced gingival overgrowth

A number of idiopathic, pathological and pharmacological reactions may result in an overgrowth of the gingiva. This review concentrates on those overgrowths associated with various pharmacological agents. The pharmaco-kinetics and side effects of each drug associated with gingival overgrowth are discussed along with the clinical and histological features and treatment. By examining the possible pathogeneses for these overgrowths we propose a unifying hypothesis for the causation based around inhibition of apoptosis and decreased collagenase activity modulated by cytoplasmic calcium.

5 alpha reductase activity in human gingiva and gingival fibroblasts in response to bacterial culture supernatants, using [14C]4-androstenedione as substrate

5 alpha-Reduction of androgen substrates is increased in inflamed gingiva. It was therefore relevant to study the effect of bacterial culture supernatants derived from Prevotella intermedius (P.i), Porphyromonas gingivalis (P.g) and Actinobacillus actinomycetemcomitans (A.a) on the metabolism of [14C]4-androstenedione to 5 alpha-dihydrotestosterone (DHT) in gingival tissue and cultured fibroblasts. Chronically inflamed human gingival tissue and cultured gingival fibroblasts from the same source were incubated in duplicate with [14C]4-androstenedione and optimal concentrations of P.i, P.g. and A.a culture supernatants in Eagle's minimal essential medium in a CO2 incubator for 24 h at 37 degrees C. The metabolites were then extracted, separated and quantified using a radioisotope scanner. There were 87, 50 and 6% increases in DHT synthesis by human gingival tissue in response to the culture supernatants of P.i, P.g and A.a, respectively, over control incubations (n = 3; p < 0.01: Wilcoxon signed-ranked statistic for paired observations). With the cells in culture, all four fibroblast cell lines produced DHT and testosterone from [14C]4-androstenedione in varying amounts. The production of DHT was enhanced in the presence of each the bacterial culture supernatants to varying degrees (P.i 40%, P.g 35% and A.a 40%; p < 0.01). Combinations of the bacterial extracts: (P.i + P.g), (P.i + A.a), (P.g + A.a) and (P.i + P.g + A.a) showed intermediate or suppressor effects on DHT formed compared with individual incubations. Culture supernatants of these pathogens can influence DHT synthesis in fibroblasts, and effect that is modulated by baseline androgen metabolism and the proportion of virulent pathogens present. This may have some bearing on host susceptibility on host and the progression of the periodontal lesion.

Phenytoin in wound healing

OBJECTIVE

To describe a patient with a massive Grade IV pressure ulcer that responded rapidly to treatment with topical phenytoin and to review the literature supporting the use of this therapy.

CASE SUMMARY

A 55-year-old morbidly obese white man (266 kg), with respiratory failure secondary to obesity-hypoventilation syndrome and heart failure, developed pressure ulcers on his lower back and sacrum with the first 2 weeks of hospitalization. Traditional methods of treatment were unsuccessful, and by day 79, the wound involved the entire lumbosacral area and buttocks, and had extensive undermining and sinus tract formation. Within 2 days of applying topical phenytoin, fresh granulation was apparent. After 54 days of treatment, nearly all the sinus tracts were healed. Four months after treatment with topical phenytoin had facilitated the healing of the wounds, even though the patient's multiple underlying medical problems had not resolved.

DISCUSSION

Phenytoin has been used in the healing of pressure sores, venous stasis and diabetic ulcers, traumatic wounds, and burns. Many of the existing clinical studies have methodologic flaws, such as inappropriate statistical analysis, inadequate control groups, and the absence of randomization and double-blinding. Nevertheless, all the studies have reported enhancement of wound healing, with insignificant adverse effects. Phenytoin may promote wound healing by a number of mechanisms, including stimulation of fibroblast proliferation, facilitation of collagen deposition, glucocorticoid antagonism, and antibacterial activity.

CONCLUSIONS

Phenytoin promoted the healing of a massive necrotizing soft tissue wound that was unresponsive to conventional treatment. Clinical success in this difficult case and the other reports in the literature suggest that phenytoin is effective in would healing and deserves further investigation.

The pathogenesis of drug-induced gingival overgrowth

Gingival overgrowth is a well-documented unwanted effect, associated with phenytoin, cyclosporin, and the calcium channel blockers. The pathogenesis of drug-induced gingival overgrowth is uncertain, and there appears to be no unifying hypothesis that links together the 3 commonly implicated drugs. In this review, we consider a multifactorial model which expands on the interaction between drug and/or metabolite, with the gingival fibroblasts. Factors which impact upon this model include age, genetic predisposition, pharmacokinetic variables, plaque-induced inflammatory and immunological changes and activation of growth factors. Of these, genetic factors which give rise to fibroblast heterogeneity, gingival inflammation, and pharmacokinetic variables appear to be significant in the expression of gingival overgrowth. A more thorough understanding of the pathogenesis of this unwanted effect will hopefully elucidate appropriate mechanisms for its control.

Increased lysyl oxidase activity in fibroblasts cultured from oral submucous fibrosis associated with betel nut chewing in Taiwan

Growth characteristics and lysyl oxidase activity of fibroblasts derived from human normal mucosa (NM) and oral submucous fibrosis (OSF) associated with betel nut chewing were compared in cell cultures. The growth rates of cultured cells were identified by plating 5 x 10(5) cells/35 mm culture dish (Day 0) and every 24 hours cell proliferation was determined by quantifying the cell number (using a hemocytometer). The third to seventh passages were used. A medium without serum but supplemented with 5 mg/ml bovine serum albumin was substituted for the original medium at the subconfluent period and cultured for an additional 24 h. The medium was collected and used for assays of protein content and lysyl oxidase activity. Lysyl oxidase activity was assayed with [4,5-3H]--lysine labelled purified chick--embryo aorta elastin substrate. After incubation for 10 h at 37 degrees C, the enzyme activity was measured from 3HHO (tritiated water) separated by ultrafiltration using Amicon C-10 micro-concentrators. The results showed the mean doubling time of OSF fibroblasts was 3.2 days and of NM fibroblasts was 3.6 days. NM fibroblasts became confluent at day 6 as determined by cell number, while OSF fibroblasts were confluent by Day 5. Furthermore, the immunoenzymatic assay for BrdUrd incorporation revealed that OSF fibroblasts proliferate significantly faster than NM fibroblasts under standard culture conditions. Both total protein content (10.84 +/- 1.15 mg/ml) and lysyl oxidase activity (3558.6 +/- 345.5 cpm/10(6) cell) in OSF fibroblasts were greater than in NM fibroblasts (6.35 +/- 0.96 mg/ml and 2436.0 +/- 352.6 cpm/10(6) cell). The results of this study provide evidence that fibroblasts derived from oral submucous fibrosis (OSF) tissue and normal mucosa (NM), although similar in many respects, exhibit specific differences in proliferation rates and lysyl oxidase activity. Moreover, collagen deposition in OSF tissue may, at least in part, be ascribed to increased lysyl oxidase activity.

Phenytoin at micromolar concentrations is an osteogenic agent for human-mandible-derived bone cells in vitro

The present study sought to test the hypothesis that phenytoin acts on normal human-mandible-derived bone cells to induce osteogenic effects. To test the effects of phenytoin on bone cell proliferation, we measured [3H]-thymidine incorporation into cell DNA during the final four hr of a 24-hour incubation with phenytoin. Phenytoin at micromolar concentrations significantly stimulated the [3H]-thymidine incorporation in a dose-dependent, biphasic, manner with a maximal effect at from 10 to 50 microM. We confirmed the proliferative effect of phenytoin by counting cell number. To evaluate the effects of phenytoin on osteoblastic differentiation, we determined alkaline-phosphatase specific activity and found that phenytoin at micromolar concentrations significantly increased that activity in a dose-dependent manner, with maximal stimulation at approximately 1 microM. To investigate the effects of phenytoin on mature osteoblastic activities, we measured de novo collagen synthesis and osteocalcin secretion. Mitogenic doses of phenytoin significantly increased collagen synthesis and osteocalcin secretion in a dose-dependent, biphasic, manner, with the maximal stimulatory dose at from 5 to 10 microM. In summary, phenytoin at micromolar ranges increased (a) [3H]-thymidine incorporation and cell number, (b) alkaline-phosphatase specific activity, (c) collagen synthesis, and (d) osteocalcin secretion in monolayer cultures of normal human-mandible-derived bone cells. These observations are consistent with the premise that low doses of phenytoin act on human craniofacial bone cells to stimulate cell proliferation, differentiation, and mature osteoblastic activities to stimulate bone formation.

Altered collagen metabolism in nifedipine-induced gingival overgrowth

Fibroblasts from nifedipine-induced fibrotic gingiva (NFG) have been characterized with respect to several cellular functions which could contribute to the characteristic clinical overgrowth of the gingiva: collagen synthesis and breakdown, glycosaminoglycan production, fibronectin synthesis, and proliferation. Histologic examination of NFG tissue revealed a hyperplastic epithelium with elongated, branched rete pegs. The connective tissue consisted of densely-packed collagen fibers and numerous enlarged fibroblasts, as well as regions of thinner, disorganized collagen fibers in the vicinity of scattered inflammatory and mast cells. Results of in vitro experiments showed that the fibroblast strains from the fibrotic gingiva (NFG) produced significantly greater amounts of collagen and lower levels of collagenase activity when compared to age- and sex-matched normal human gingival fibroblast strains. The NFG fibroblasts did not produce significantly greater amounts of fibronectin, and their level of glycosaminoglycan production was less than that of the normal fibroblasts. The NFG fibroblasts did not proliferate significantly more rapidly than the normal fibroblast strains. These findings therefore show that there are defects in the regulation of collagen production by NFG fibroblasts in vitro, and suggest that these alterations in collagen metabolism contribute to the over-deposition of collagen in this tissue, rather than hyperproliferation of the fibroblasts or through the production of increased amounts of fibronectin and glycosaminoglycans.

Effect of calcium-channel blockers on cell proliferation, DNA synthesis and collagen synthesis of cultured gingival fibroblasts derived from human nifedipine responders and non-responders

Human gingival fibroblasts from six patients who developed gingival hyperplasia as a result of nifedipine medication and five who did not were studied for the effects of calcium-channel blockers (nifedipine, diltiazem, verapamil and nicardipine) on cell proliferation, DNA synthesis and collagen synthesis. Phenytoin was used as a positive control. The fibroblasts from reactive patients gave trends toward better cell proliferation rates, DNA synthesis ([3H]-thymidine incorporation), and collagen synthesis ([3H]-proline incorporation) than those from non-reactive patients in the presence of 1 microM of calcium-channel blockers or phenytoin.

Increased expression of type VI collagen genes in drug-induced gingival enlargement

Fibrotic gingival enlargements induced by phenytoin or nifedipine were examined with special reference to type VI collagen expression. Immunolocalization studies showed abnormal accumulation of type VI collagen around the collagen fiber bundles in the fibrotic gingival enlargements. Examination of total RNA extracted from fibroblasts and tissues of enlarged gingivae demonstrated increased type VI collagen steady-state mRNA levels. These results suggest that excessive deposition of type VI collagen in drug-induced gingival enlargement is attributed to increased expression of the collagen genes.

Phenytoin has little effect on in-vitro models of wound healing

It has been reported that phenytoin induces gingival and connective tissue hyperplasia and may be of use in wound healing. In this study the effect of phenytoin on human epidermal keratinocytes and skin fibroblasts has been investigated in vitro. Cell cultures were exposed to increasing concentrations of phenytoin from 10(-9) to 10(-4) M in the presence of 1 and 10% serum supplemented medium. In addition the effect of phenytoin on epidermal cell migration (epiboly) has been investigated using organ culture of human skin. No stimulation of cell growth was observed, and only a mild toxicity affecting keratinocytes was seen at the highest concentrations. Similarly, no effect on epidermal cell migration in vitro was observed. The lack of a direct effect in vitro suggests that any in-vivo effect was not the result of interaction between phenytoin and keratinocytes or fibroblasts but possibly due to indirect modulation via other cell types, such as inflammatory or lymphoreticular cells.

Fibroblast heterogeneity in collagenolytic response to cyclosporine

To investigate the mechanism of cyclosporine (CS)-induced fibrotic gingival enlargement, the effect of CS on the collagenolytic activities of 14 different human gingival fibroblast strains derived from healthy individuals with non-inflammed gingiva was examined in vitro. There was marked heterogeneity among individuals in basal levels of collagenase activity, and there was also variation among the subpopulations derived from one strain. Fibroblasts from different individuals also varied markedly in their collagenolytic response to CS (0.1 to 0.75 micrograms/ml). In most strains, CS decreased collagenase activity, but in some, the drug caused no change or significantly increased activities. In most of the subpopulations CS significantly decreased collagenolytic activity. Two of the fibroblasts strains and the subpopulations described above were examined for the production of immunoreactive collagenase and tissue inhibitor of metalloproteinase (TIMP). The two strains made similar amounts of collagenase, but differed markedly in TIMP levels; CS affected their collagenase production differently but had similar effects on TIMP. Among the subpopulations there was variation in the production of collagenase, although none made detectable levels of TIMP; they also varied in the production of both proteins in response to CS. In two of the subpopulations and in both strains at some concentrations, the effect of CS on the relative levels of collagenase and TIMP could account for the decreased collagenase activity; i.e., the level of collagenase was unchanged or decreased, and TIMP production was unchanged or increased. This study demonstrates the variation among individuals as well as intrastrain heterogeneity of human gingival fibroblasts with regard to collagenase activity and the production of collagenase and TIMP. The heterogeneity of the collagenolytic response of different gingival fibroblast strains and their subpopulations to CS treatment may partly explain the susceptibility of only some individuals to CS-induced gingival enlargement.

Role of fibroblast subpopulations in periodontal physiology and pathology

Fibroblasts are the principal cell type in the soft connective tissues of the periodontium; they perform important functions in development, physiology, and disease. A growing number of reports have indicated site-specific phenotypic variation of fibroblasts. Heterogeneity of metabolic traits has been demonstrated in cells from healthy and diseased tissues. The tissue distribution and relative proportions of fibroblast subpopulations have a significant impact on the regulation of connective tissue function in health and disease.

Characterization of fibroblasts derived from human periodontal ligament and gingiva

Growth characteristics and macromolecular synthesis of fibroblasts derived from human periodontal ligament (PDLF) and gingiva (GF) have been compared in cell culture. Cells were isolated from explants and plated at 500,000 cells/100 mm culture dish (day 0) with daily changes of culture medium. DNA histograms were obtained by flow microfluorimetric analysis to confirm the growth state of the cell cultures. Human PDLF cultures became confluent at day 6 as determined by cell number and cell cycle analysis while GF were confluent by day 4. Initially, DNA content of logarithmically growing cells was significantly greater in GF cultures; however, when confluent, DNA content and cell number was greater in PDLF cultures. Total protein content in GF was slightly greater than PDLF until day 7 but this difference was not significant. Analysis of collagen and noncollagen protein synthesis revealed a greater trend in noncollagen protein synthesis in the GF cultures compared to PDLF cultures. Analysis of glycosaminoglycans in the culture medium of GF and PDLF revealed similar distributions of components. In the cellular fraction, GF had greater amounts of hyaluronic acid and heparin and lesser amounts of chondroitin sulfates A and C than PDLF cultures. The results indicate that the growth characteristics of PDLF and GF, although similar in many respects, do exhibit specific differences in proliferative rates and macromolecular synthesis. The differences observed in these parameters may be important during in vivo events, such as guided tissue regeneration, where significant functional differences are observed between gingival connective tissue and periodontal ligament connective tissue.

Collagen synthesis by human fibroblasts. Regulation by transforming growth factor-beta in the presence of other inflammatory mediators

We have examined the combined effects of transforming growth factor-beta (TGF-beta), serum and gamma-interferon (gamma-IFN) on collagen synthesis by fibroblasts and compared the response of fibroblast subpopulations to TGF-beta. Human diploid fibroblasts were treated with TGF-beta alone and with serum of gamma-IFN. Cells were labelled with radioactive amino acids, and collagen production was measured as collagenase-digestible radioactivity. Collagen mRNA was determined by a solution-hybridization assay using procollagen-alpha 1[I] cDNA clone HF 677. The results showed that either serum or TGF-beta increased incorporation, collagen production and mRNA by fibroblasts approx. 2-fold; however, collagen synthesis relative to total protein synthesis and collagen mRNA relative to total polyadenylated [poly(A)+] RNA were not affected. Only serum activated cell growth. Collagen production increased approx. 4-fold in cells exposed to both TGF-beta and serum, and this increase was equal to that expected for an additive effect by both components. Treatment with gamma-IFN decreased collagen production and collagen mRNA to 44 and 40% respectively, whereas total incorporation and poly(A)+ RNA were affected only marginally. Cells exposed simultaneously to both gamma-IFN and TGF-beta produced less collagen and contained less mRNA than did those treated with TGF-beta alone. The gamma-IFN decreased collagen synthesis in control and TGF-beta-treated cultures to a similar extent, and TGF-beta increased collagen synthesis 2-fold in cells pre-treated with gamma-IFN. Fibroblast strains obtained in medium containing plasma-derived serum synthesized approximately half as much collagen as did cells derived from the same explant in the presence of fresh human serum, and TGF-beta stimulated collagen production and mRNA in both cell strains. We conclude that TGF-beta, serum and gamma-IFN regulate collagen synthesis by independent mechanisms, and that the combined action of these components plays a significant role in regulating collagen synthesis during wound healing and tissue repair.