Up-regulation of keratinocyte growth factor and receptor: a possible mechanism of action of phenytoin in wound healing

Multiple functions of gingival and mucoperiosteal fibroblasts in oral wound healing and repair

Fibroblasts are cells of mesenchymal origin. They are responsible for the production of most extracellular matrix in connective tissues and are essential for wound healing and repair. In recent years, it has become clear that fibroblasts from different tissues have various distinct traits. Moreover, wounds in the oral cavity heal under very special environmental conditions compared with skin wounds. Here, we reviewed the current literature on the various interconnected functions of gingival and mucoperiosteal fibroblasts during the repair of oral wounds. The MEDLINE database was searched with the following terms: (gingival OR mucoperiosteal) AND fibroblast AND (wound healing OR repair). The data gathered were used to compare oral fibroblasts with fibroblasts from other tissues in terms of their regulation and function during wound healing. Specifically, we sought answers to the following questions: (i) what is the role of oral fibroblasts in the inflammatory response in acute wounds; (ii) how do growth factors control the function of oral fibroblasts during wound healing; (iii) how do oral fibroblasts produce, remodel and interact with extracellular matrix in healing wounds; (iv) how do oral fibroblasts respond to mechanical stress; and (v) how does aging affect the fetal-like responses and functions of oral fibroblasts? The current state of research indicates that oral fibroblasts possess unique characteristics and tightly controlled specific functions in wound healing and repair. This information is essential for developing new strategies to control the intraoral wound-healing processes of the individual patient.

The impact of topical phenytoin on recalcitrant neuropathic diabetic foot ulceration

OBJECTIVE

To study the impact of topical phenytoin on the healing of recalcitrant neuropathic diabetic foot ulcers in patients with no clinical evidence of ischaemia or infection, and to evaluate its antibacterial effect.

METHOD

Thirty-two patients were enrolled into the study. Topical phenytoin in the form of 2% aerosol powder was applied once daily in addition to the patient's usual treatment (weekly sharp debridement, offloading and use of a gauze dressing) for eight weeks. The primary outcome was change in ulcer area over time, measured by grid tracing. Secondary outcomes were the ability of topical phenytoin to eradicate bacterial isolates, and the occurrence of adverse events.

RESULTS

Topical phenytoin significantly improved healing of recalcitrant neuropathic diabetic foot ulcers. Baseline wound area was 319.3 + 340.4 mm2, reducing to 286.1 + 341.1 mm2 and 269.1 + 341.2 mm2 after four and eight weeks respectively. However, the overall reduction in ulcer size was only 18.3% + 27.5% and 25.7% + 38.6 % respectively. Topical phenytoin therapy over eight weeks did not eradicate any of the bacterial wound isolates (Staphylococcus spp., Proteus spp. or Pseudomonas spp.). Of the 32 patients evaluated, only eight (25%) achieved more than 50% reduction in ulcer size after eight weeks of treatment.

CONCLUSION

Topical phenytoin can enhance wound healing in recalcitrant neuropathic diabetic foot ulcers, although only one-quarter of patients achieved more than 50% reduction in ulcer size after eight weeks of therapy. Further research is needed to characterise those patients who will satisfactorily respond to such therapy.

Topical diphenylhydantoin sodium can improve healing in a diabetic incisional animal wound model

OBJECTIVE

Anecdotally, topical application of diphenylhydantoin sodium (DpH) (phenytoin) has been shown to aid wound healing. We previously reported improved healing following topical infiltration of DpH in a healthy animal wound model. This study evaluates its effect on an incisional wound model in diabetic animals.

METHOD

Twenty-five male Sprague-Dawley rats were rendered diabetic by a single intraperitoneal injection of streptozotocin. Two caudal and two cephalad wounds were made on the dorsal surface. A polyvinyl alcohol sponge was placed in a subcutaneous pocket created proximal to both cephalad wounds. Each wound was either treated topically with 10mg DpH in a 200microl carrier or an equal volume of the saline vehicle (control) on the day of wounding and days 3 and 6 post-incision. The animals were sacrificed on day 10. The breaking strength of fresh and fixed wounds was determined by tensiometry, and the hydroxyproline content was determined spectrophotometrically.

RESULTS

There was a significant overall increase in both fresh (24%) and fixed (18%) wound-breaking strength of the DpH-treated wounds when compared with the controls (p<0.05). This was associated with an increase in collagen synthesis as indicated by the increased hydroxyproline content in the DpH-infiltrated sponges when compared with the controls.

CONCLUSION

Our data suggest that topical DpH improves healing in a diabetic wound model. Topical administration of DpH has the potential to accelerate diabetic wound healing and should be evaluated in human diabetic wounds.

Antiepileptic drugs prevent changes induced by pilocarpine model of epilepsy in brain ecto-nucleotidases

Ecto-nucleotidases, one of the main mechanisms involved in the control of adenosine levels in the synaptic cleft, have shown increased activities after the pilocarpine model of epilepsy. Here we have investigated the effect of the antiepileptic drugs (AEDs) on ecto-nucleotidase activities from hippocampal and cerebral cortical synaptosomes of rats at seven days after the induction of the pilocarpine model. Expression of these enzymes were investigated as well. Our results have demonstrated that phenytoin (50 mg/kg) and carbamazepine (30 mg/kg) were able to prevent the increase in ecto-nucleotidase activities elicited by pilocarpine in brain synaptosomes. However, sodium valproate (at 100 mg/kg) was only able to avoid the increase on ATP and ADP hydrolysis in hippocampal synaptosomes. Increase on ATP hydrolysis in hippocampal synaptosomes was also prevented by sodium valproate at 286 mg/kg, which corresponds to ED50 for pilocarpine model. NTPDase1, NTPDase2, NTPDase3, and ecto-5'-nucleotidase expressions were not affected by pilocarpine in cerebral cortex. However, expressions of NTPDase2, NTPDase3, and ecto-5'-nucleotidase were increased by pilocarpine in hippocampus. Our results have indicated that previous treatment with AEDs was able to prevent the increase in hippocampal ecto-nucleotidases of pilocarpine-treated rats. These findings have shown that anticonvulsant drugs can modulate plastic events related to the increase of nucleotidase expression and activities in pilocarpine-treated rats.

Initial responses of human osteoblasts to sol-gel modified titanium with hydroxyapatite and titania composition

Sol-gel thin films of hydroxyapatite (HA) and titania (TiO(2)) have received a great deal of attention in the area of bioactive surface modification of titanium (Ti) implants. Sol-gel coatings were developed on Ti substrates of pure HA and TiO(2) and two composite forms, HA+10% TiO(2) and HA+20% TiO(2), and the biological properties of the coatings were evaluated. All the coating layers exhibited thin and homogeneous structures and phase-pure compositions (either HA or TiO(2)). Primary human osteoblast cells showed good attachment, spreading and proliferation on all the sol-gel coated surfaces, with enhanced cell numbers on all the coated surfaces relative to uncoated Ti control at day 1, as observed by MTT assay and scanning electron microscopy. Cell attachment rates were also enhanced on the pure HA coating relative to control Ti. The pure HA and HA+10% TiO(2) composite coating furthermore enhanced proliferation of osteoblasts at 4 days. Moreover, the gene expression level of several osteogenic markers including bone sialoprotein and osteopontin, as measured by RT-PCR at 24h, was shown to vary according to coating composition. These findings suggest that human primary bone cells show marked and rapid early functional changes in response to HA and TiO(2) sol-gel coatings on Ti.

Effects of minocycline and doxycycline on cell survival and gene expression in human gingival and periodontal ligament cells

OBJECTIVES AND BACKGROUND

Periodontitis is an infectious disease in the gingival crevice caused by periodontopathic bacteria, including Porphyromonas gingivalis, Prevotella intermedia, Actinobacillus actinomycetemcomitans, and Tennerella forsythensis, and antibacterial agents are directly administered to the site of infection to treat it. To maximize the therapeutic effects while reducing the adverse effects, the antibacterial agents should be administered at concentrations greater than their MIC(90) doses required to inhibit the growth of 90% of periodontopathic bacteria and the administration should not damage the periodontal tissue. One approach for estimating cellular damage in the periodontal tissue caused by the administration is to assay cytological damages following exposures of cultured human cells derived from periodontal tissues to antibacterial agents. In the present study, we investigated the cytotoxic effect of minocycline (MINO) and doxycycline (DOX) by using a human gingival fibroblast cell line, a human gingival epithelial cell line, and a human periodontal ligament fibroblast cell line. We also used these cell lines to study the effect of MINO or DOX on the mRNA and protein expressions of genes associated with the differentiation of fibroblasts and the proliferation, differentiation, or cellular adhesion important to the epithelial regeneration of the periodontal attachment.

METHODS

The cytotoxic effect of MINO or DOX was measured as a decrease in cell survivals. The effects of these antibiotics on the mRNA and protein expressions in the cell lines were studied by reverse transcription-polymerase chain reaction (RT-PCR) and western blot analyses, respectively.

RESULTS

The maximum concentration of MINO or DOX that has little effect on the cell survivals and the mRNA and protein expressions of genes for alkaline phosphatase, type I procollagen, keratinocyte growth factor receptor, keratin 18 or 8/18, integrin beta1, integrin beta4, and laminin 5gamma2 was 10 or 30 microm, respectively, which are greater than their MIC(90) doses against periodontopathic bacteria described above.

CONCLUSIONS

These findings suggest that little, if any, cellular damage would be expected with topical administration of MINO or DOX to the periodontal pocket at a dose equivalent to the MIC(90). It is important to note, however, that the extrapolation of these findings to in vivo conditions has yet to be undertaken.

Roughness response genes in osteoblasts

Titanium (Ti) and Ti alloys are widely used as dental and orthopedic implants, but the effects of the surface characteristics of these materials, including roughness, on the response of target tissues in vivo are not well understood. The present study has therefore examined the effects of a moderately rough (sand-blasted, acid-etched; SLA) Ti surface, a highly rough (plasma-sprayed; TPS) surface, and a smooth surface (SMO) on bone cells in vitro. X-ray photoelectron spectroscopy showed that these surfaces had similar surface chemistry, while scanning electron microscopy suggested that the SLA provided a transiently less biocompatible surface, with initially less well-attached cells. SLA also delayed bone cell growth compared with SMO, whereas the TPS surface elicited the greatest increase in cell numbers. In addition, expression profiling using the ATLAS gene array showed marked differences in gene responses after 3 h of incubation; this increased further after 24 h, with TPS generating the largest number of up- and down-regulated genes compared with SLA and SMO. A number of osteoblast genes were also identified as 'roughness' genes on the basis of their similar response on SLA and TPS, compared with SMO. These findings show, for the first time, that the surface roughness of Ti has a profound effect on the profile of genes expressed by bone cells and suggest that improvements in the biological activity and possibly the clinical efficacy of these materials could be achieved by selective regulation of gene expression mediated via modification of surface roughness.

Cl- channels in basolateral TAL membranes. XIX. Cytosolic Cl- regulates mmCIC-Ka and mcCIC-Ka channels

We evaluated the effects of culturing mouse MTAL cells under conditions that suppressed steady-state cytosolic Cl- on chloride channels fused into bilayers from basolateral vesicles of cultured MTAL cells. We used two agents to suppress Cl- entry: 10(-6) M PGE2 and 10(-4) M bumetanide. Basolateral Cl- channels from control cultured MTAL cells exhibited the signature characteristics of mmCIC-Ka channels: increased open-time probability (Po) either by raising cytosolic-face [Cl-] or, at 2 mM cytosolic Cl-, by adding (ATP + PKA), and first-order conductance kinetics. Either 10(-6) M PGE2 or 10(-4) M bumetanide in culture media reduced steady-state MTAL cytosolic Cl-. Chloride channels from these cells exhibited characteristics unique to CTAL mcCIC-Ka channels, namely: no augmentation of Po either by raising cytosolic Cl- or with cytosolic (ATP + PKA), and multi-ion occupancy. Semi-quantitative RT-PCR and real-time quantitative PCR showed that culturing MTAL cells with 10(-6) M PGE2 or 10(-4) M bumetanide reduced mRNA levels encoding mmCIC-Ka but not mRNA levels encoding mcCIC-Ka. However, when MTAL cells were cultured under control conditions, and then pre-incubated for 60 minutes with 10(-4) M bumetanide, cytosolic Cl- fell acutely but Cl- channels exhibited characteristics of mmCIC-Ka channels. Thus PGE2 and bumetanide, both of which lower steady-state MTAL cytosolic Cl- concentrations, inhibit either the transcriptional and/or the translational processes for mmCIC-Ka synthesis.

Ribosomal S6 kinase as a mediator of keratinocyte growth factor-induced activation of Akt in epithelial cells

The keratinocyte growth factor receptor (KGFR) is a member of the fibroblast growth factor receptor (FGFR) superfamily. The proximal signaling molecules of FGFRs are much less characterized compared with other growth factor receptors. Using the yeast two-hybrid assay, we have identified ribosomal S6 kinase (RSK) to be a protein that associates with the cytoplasmic domain of the KGFR. The RSK family of kinases controls multiple cellular processes, and our studies for the first time show association between the KGFR and RSK. Using a lung-specific inducible transgenic system we have recently demonstrated protective effects of KGF on the lung epithelium and have demonstrated KGF-induced activation of the prosurvival Akt pathway both in vivo and in vitro. Here we show that a kinase inactive RSK mutant blocks KGF-induced Akt activation and KGF-mediated inhibition of caspase 3 activation in epithelial cells subjected to oxidative stress. It was recently shown that RSK2 recruits PDK1, the kinase responsible for both Akt and RSK activation. When viewed collectively, it appears that the association between the KGFR and RSK plays an important role in KGF-induced Akt activation and consequently in the protective effects of KGF on epithelial cells.

Role of phenytoin in wound healing: microarray analysis of early transcriptional responses in human dermal fibroblasts

Wound healing is a complex process involving a number of related genes and receptors. Using cDNA microarrays, we explored the global gene expression profile of phenytoin (20microg/ml) induced changes to human dermal fibroblasts. Microarray data analysis revealed approximately 1500 genes were differentially expressed by 2.5-fold. At 3, 6, 12, and 24h, the transcripts of the major growth factors involved in wound healing and their receptors were increased. This was further confirmed by RT-PCR. Genes encoding other proteins with roles in signal transduction (NFkappaB), extracellular matrix (MMP1) including type I collagen, fibronectin, and laminin were strongly induced at 6h and onwards. Genes involved in cell cycle regulation (CCND1 and CDKN1A) were down-regulated consistent with our finding that phenytoin per se did not have cell proliferation activity. Notably, phenytoin accelerates the autocrine and paracrine activity of growth factors by up-regulating the related receptors.

Keratinocyte growth factor receptor is up-regulated in cyclosporin A-induced gingival hyperplasia

Keratinocyte growth factor stimulates the growth and activity of epithelial cells via the keratinocyte growth factor receptor. We have recently shown that the growth factor is markedly elevated in cyclosporin A-induced gingival hyperplasia tissue in vivo, but the effects of cyclosporin A on the receptor are not yet known. The present study was therefore carried out to determine whether expression of the keratinocyte growth factor receptor is up-regulated in gingival hyperplasia compared with normal gingiva. Using immunohistochemistry and the reverse-transcribed polymerase chain-reaction, we obtained results which showed that receptor antigen and gene transcript levels were both elevated in gingival hyperplasia tissue. In addition, flow cytometry and the reverse-transcribed polymerase chain-reaction showed that the receptor and mRNA were also higher in gingival epithelial cells following incubation with cyclosporin A in vitro. These findings suggest that the keratinocyte growth factor-receptor pathway of mesenchymal-epithelial interaction could play an important part in the molecular pathogenesis of gingival hyperplasia.

Cl- channels in basolateral TAL membranes. XVI. MTAL and CTAL cells each contain the mRNAs encoding mmClC-Ka and mcClC-Ka

BACKGROUND

Our prior data indicate that two separate but homologous basolateral chloride (Cl-) channels, mmClC-Ka and mcClC-Ka, are the principal mediators of net Cl- absorption in mouse medullary thick ascending limb (MTAL) and cortical thick ascending limb (CTAL) cells, respectively. In the present studies, we evaluated the possibility that there might be translational or post-translational suppression of mmClC-Ka and mcClC-Ka activity in CTAL and MTAL cells, respectively.

METHODS

Polymerase chain reaction (PCR) fragments were prepared that were highly specific for either mmClC-Ka or mcClC-Ka, the cDNAs encoding mmClC-Ka and mcClC-Ka, respectively.

RESULTS

Using reverse transcription (RT)-PCR with these highly specific products, mRNAs specific for non-homologous channel sequences in either mmClC-Ka or mcClC-Ka were present in both MTAL and CTAL cells.

CONCLUSIONS

Both mouse MTAL and CTAL cells contain the mRNAs encoding mmClC-Ka and mcClC-Ka. There may be translational or post-translational suppression of mmClC-Ka activity in CTAL cells, and of mcClC-Ka activity in MTAL cells.