Development of an in vitro wound healing model for periodontal cells

Supplement of secreted recombinant low molecular weight human fibroblast growth factor 2 in culture media enhances in vitro bovine maturation

With the annual increase in in vitro bovine embryo production, understanding oocyte maturation is becoming more important. Previous studies have shown that oocyte maturation can be improved by adding bovine additives to in vitro maturation media. Among the additives, human fibroblast growth factor 2 (hFGF2) is well known for its positive influence on the growth rate and quality of cells and oocytes. However, the effect of LMW-hFGF2, one of the isoforms of hFGF2, on bovine in vitro maturation has not yet been identified. Therefore, the goal of this study was to elucidate the effect of LMW-hFGF2 on bovine oocyte maturation. Vectors expressing LMW-hFGF2 were cloned and transfected into cells. Afterward, secretion of LMW-hFGF2 from cells was confirmed, and used to assess the effect LMW-hFGF2 on cells and bovine oocytes. LMW-hFGF2 improved bovine oocyte maturation and embryo developmental competence. Laboratories can use LMW-hFGF2 in bovine oocyte culture media to improve in vitro embryo production success rates.

Effects of DDR1 on migration and adhesion of periodontal ligament cells and the underlying mechanism

BACKGROUND AND OBJECTIVE

As one of the widely expressed cell surface receptors binding to collagen, the most abundant component of the extracellular matrix (ECM), knowledge of the expression, functions, and mechanisms underlying the role of discoidin domain receptor 1 (DDR1) in human periodontal ligament cells (hPDLCs) is incomplete. This study determined the expression of DDR1 in hPDLCs and the effect of DDR1 upon migration and adhesion to hPDLCs, as well as the related regulatory mechanisms.

MATERIALS AND METHODS

The expression of DDR1 and the DDR1 isoforms in hPDLCs from six donors were tested. The migratory ability (horizontal and vertical) and adhesive capacity of hPDLCs with or without specific knockdown of DDR1 were evaluated. After treatment with MEK-ERK1/2 inhibitors (PD98059 and U0126) with or without RNAi, the migratory and adhesive capacity of hPDLCs were re-tested. Western blotting was performed to verify p-MEK1/2 and p-ERK1/2, the key factors of the MEK-ERK1/2 signaling pathways.

RESULTS

DDR1 was detected in hPDLCs in the mRNA and protein level; DDR1b was the dominant isoform. Knockdown of DDR1 almost halved the migratory capacity and significantly downregulated the adhesive capacity of hPDLCs. The use of MEK-ERK1/2 inhibitors caused declined migratory and adhesive capacity of hPDLCs as well. After DDR1 was knocked down, the expression of p-MEK and p-ERK protein declined significantly while total MEK and ERK showed no obvious change, which means the ratio of p-MEK/MEK and p-ERK/ERK was markedly reduced.

CONCLUSIONS

DDR1 plays an important role in the migration and adhesion of hPDLCs and might be regulated via the MEK-ERK1/2 signaling pathway.

A Review of In Vivo and Clinical Studies Applying Scaffolds and Cell Sheet Technology for Periodontal Ligament Regeneration

Different approaches to develop engineered scaffolds for periodontal tissues regeneration have been proposed. In this review, innovations in stem cell technology and scaffolds engineering focused primarily on Periodontal Ligament (PDL) regeneration are discussed and analyzed based on results from pre-clinical in vivo studies and clinical trials. Most of those developments include the use of polymeric materials with different patterning and surface nanotopography and printing of complex and sophisticated multiphasic composite scaffolds with different compartments to accomodate for the different periodontal tissues' architecture. Despite the increased effort in producing these scaffolds and their undoubtable efficiency to guide and support tissue regeneration, appropriate source of cells is also needed to provide new tissue formation and various biological and mechanochemical cues from the Extraccellular Matrix (ECM) to provide biophysical stimuli for cell growth and differentiation. Cell sheet engineering is a novel promising technique that allows obtaining cells in a sheet format while preserving ECM components. The right combination of those factors has not been discovered yet and efforts are still needed to ameliorate regenerative outcomes towards the functional organisation of the developed tissues.

Adiponectin inhibits lipoplysaccharide-induced inflammation and promotes osteogenesis in hPDLCs

Periodontal diseases are infections of the structures that surround and support the teeth; they are characterized by local inflammation and alveolar bone loss. Most treatments focus on only one aspect, inhibiting inflammation, or promoting osteoblasts. We set out to develop a new method that would intervene in the two aspects simultaneously. Adiponectin (APN), secreted by adipocytes, inhibits the inflammatory response and promotes osteogenesis. However, its role in human periodontal ligament cells (hPDLCs) is unclear. Therefore, we aim to investigate whether APN could suppress lipopolysaccharide (LPS)-induced inflammation and promote osteogenesis in hPDLCs. In the present study, we stimulated hPDLCs with LPS in the presence or absence of APN. Real-time PCR and Western blotting results demonstrated that APN partially inhibited the activation of the classical nuclear factor κ-B (NF-κB) pathway. These results were confirmed by a change of expressions of NF-κB downstream inflammatory genes, such as decreased cyclooxygenase (COX)-2 and tumor necrosis factor α (TNF-α), along with increased interleukin (IL)-10. As for the role of APN in osteogenesis, Alizarin Red S staining showed that APN treatment induced more calcium deposition nodules than controls. We also found that APN enhanced the expression of osteoblast-related genes (osteopontin (OPN), collagen 1, osteocalcin, alkaline phosphatase, runt-related transcription factor 2 (RUNX2), and bone morphogenetic protein 2) in hPDLCs via the APPL1 (the adaptor protein containing PH domain, PTB domain, and leucine zipper motif 1)/p38 signal transduction pathway. Therefore, APN inhibits LPS-induced inflammation and promotes osteogenesis in hPDLCs and may have potential therapeutic value in treating periodontitis by inhibiting the inflammatory lesions and contributing to bone tissue regeneration.

Upregulation of centromere protein M promotes tumorigenesis: A potential predictive target for cancer in humans

Centromere protein M (CENPM), a protein required for chromosome separation, is involved in in mitosis. However, little has been reported about the roles of CENPM in various types of cancer. The present study identified that the mRNA expression levels of CENPM were significantly upregulated in 14 types of human cancer and identified a positive association between CENPM mRNA expression and patient mortality using the Oncomine, Gene Expression Profiling Interactive Analysis, Human Protein Atlas and Kaplan‑Meier Plotter databases. A protein interaction network constructed with CENPM‑interacting genes obtained from the cBioPortal demonstrated that nine genes participating in the cell cycle served key roles in the function of CENPM. Cell cycle analysis, reverse transcription‑quantitative polymerase chain reaction, a Cell Counting Kit‑8‑based proliferation assay and a terminal deoxynucleotidyl transferase dUTP nick end labelling assay further revealed the tumorigenic and carcinogenic roles of CENPM in vitro. In addition, it was identified that the mRNA expression levels of five of the nine identified genes were significantly associated with CENPM in MCF7 cells and that CENPM was rarely mutated among various types of human cancer. In conclusion, the data from the present study revealed that CENPM exerted its pro‑tumorigenic function by regulating cell cycle‑associated protein expression and suggested that CENPM could be used as a prognostic marker for breast cancer.

Advances in scarless foetal wound healing and prospects for scar reduction in adults

Healing after mammalian skin injury involves the interaction between numerous cellular constituents and regulatory factors, which together form three overlapping phases: an inflammatory response, a proliferation phase and a remodelling phase. Any slight variation in these three stages can substantially alter the healing process and resultant production of scars. Of particular significance are the mechanisms responsible for the scar‐free phenomenon observed in the foetus. Uncovering such mechanisms would offer great expectations in the treatment of scars and therefore represents an important area of investigation. In this review, we provide a comprehensive summary of studies on injury‐induced skin regeneration within the foetus. The information contained in these studies provides an opportunity for new insights into the treatment of clinical scars based on the cellular and molecular processes involved.

Cyclic tensile forces enhance the angiogenic properties of HUVECs by promoting the activities of human periodontal ligament cells

BACKGROUND

This study aimed to investigate whether human periodontal ligament (PDL) cells secrete pro-angiogenic factors that induce the vascularization of surrounding bone tissue under tensile stress.

METHODS

Quantitative real-time PCR and Western blotting were used to analyze the mRNA and protein expression levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), Angiopoietin-I (Ang-I), connective tissue growth factor （CTGF）, and macrophage colony-stimulating factor (M-CSF) in PDL cells after tensile force treatments of different durations. Enzyme-linked immunosorbent assay was used to measure the VEGF concentration in the supernatants of cell cultures. Cell viability assay, wound healing assay, and tube formation assay were performed to evaluate the angiogenic behaviors of human umbilical vein endothelial cells (HUVECs).

RESULTS

The mRNA expression and protein expression of VEGF, bFGF, Ang-I, and M-CSF was increased in the cells that received 6 to 48 hours of tensile force treatment. And, the VEGF level in the supernatant significantly increased in the human PDL cell cultures stressed for 6 to 48 hours. The abilities of HUVECs to proliferate, migrate, and form tubes were enhanced in media conditioned with tensile-stressed human PDL cells. Hence, tensile force induced human PDL cells to express and release pro-angiogenic factors enhancing the proliferation, migration, and angiogenic capacity of HUVECs.

CONCLUSION

Tensile stress induced human PDL cells to express and release pro-angiogenic factors, including VEGF, bFGF, Ang-I, and M-CSF, thereby enhancing the proliferation, migration, and angiogenic capacity of HUVECs.

The Effects of Continual Intermittent Parathyroid Hormone Treatment on Human Periodontal Ligament Fibroblasts in an In Vitro Wound Repopulation Model

INTRODUCTION

Periodontal ligament fibroblasts (PDLFs) play a vital role in periodontal regeneration. Parathyroid hormone (PTH) is important in catabolic regulation on osteoclasts; it also has anabolic effects on hard tissue formation. Using an in vitro wound repopulation model, this study investigated the effect of continual intermittent administration of PTH on PDLFs wound repopulation. Methods and Materials: PDLFs were grown in 12-well plates and divided into 0 (control), 5, 10, 20, 40, and 80 nM of PTH treatments. A 3-mm wound was created on confluent and synchronized cells. Six PTH treatments were initiated using serum-free medium with supplements. Cell repopulation was measured at four time points: 5, 10, 15, and 20 days.

RESULTS

A 5% increase wound repopulation showed an enhancement on day 10 for all treatment groups as compared to control groups. On days 15 and 20, treatment groups showed a decrease in proliferation and migration compared to controls with significant decreases at concentrations of 40 and 80 nM.

CONCLUSION

Continual intermittent treatment with PTH has the potential to enhance proliferation and migration of PDLFs for wound repopulation at early time points. A dose-dependent correlation was seen with a positive trend on day 10 while a significant decrease on day 20.

Effect of Sodium Lauryl Sulfate (SLS) on Primary Human Gingival Fibroblasts in an In Vitro Wound Healing Model

OBJECTIVES

Sodium lauryl sulfate (SLS) is a surfactant used to decrease the surface tension of water. Most commercially available dentifrices contain 0.5-2.0% SLS. This study investigated the potential effect of SLS on oral wound healing using primary human gingival fibroblasts (HGFs).

METHODS

HGFs cells were grown in12-well culture plates in DMEM medium. A 3 mm wound was created on confluent HGFs. The cells were challenged with 0 (the control group), 0.01, 0.02, 0.03, 0.04, or 0.05% SLS-containing media once daily for 2 minutes. The cells were stained on day 0, 2, 4, 6 and 8. The percent of wound fill area was measured.

RESULTS

On day 2, 4, 6, and 8, the wound fill of the control group (0% SLS) was 15, 35, 67 and 98%, respectively; at 0.01% SLS, it was 10, 20, 65 and 84%; at 0.02%, it was 7, 10, 15 and 25%; at 0.03% SLS, it was only 5% and 8% on day 2 and 4.

CONCLUSION

Our results showed a dose- and time-dependent inhibition on HGFs wound fill by SLS; however, future in vivo studies are needed to validate if our in vitro findings using SLS-free dentifrices to avoid the potential delay of wound healing.

Impact of high glucose on metastasis of colon cancer cells

AIM: To investigate the possible mechanism of how glucose promotes invasion and metastasis of colon cancer cells.

METHODS: CT-26 rat colorectal cancer cells were cultured in different concentrations of glucose environments (10, 20, and 30 mmol/L). Wound healing assay and transwell chamber invasion assay were utilized to test the migration and invasion, respectively. In order to understand the role of signal transducer and activator of transcription 3 (STAT3) in the process, STAT3 inhibitors, including Stattic (an STAT3 specific inhibitor) and small interfering RNA targeting STAT3, were used to block STAT3 function to evaluate their impact on CT-26 cell motion. To verify whether STAT3 and matrix metalloproteinase-9 (MMP-9) protein expression is associated with glucose-induced cell movement, Western blot was used to compare the differences in the expression of MMP-9 and STAT3 in cells incubated with and without STAT3 inhibitors in high glucose condition.

RESULTS: In both wound healing and invasion assays, the migration and invasion of CT-26 cells increased gradually with the increase in glucose concentration. However, the glucose-induced migration and invasion were obviously inhibited by STAT3 inhibitors (P < 0.05). Similarly, in Western blot assessment, both MMP-9 and STAT3 expression increased under a high glucose environment and the highest expression was achieved when 30 mmol/L glucose was used. However, in cells treated with 30 mmol/L mannitol, either MMP-9 or STAT3 expression did not increase (P > 0.05). When STAT3 inhibitors were added in the 30 mM glucose group, not only STAT3 but also MMP-9 expression decreased significantly (P < 0.05).

CONCLUSION: Our study provides evidence that glucose can promote both migration and invasion of CT-26 cells, and that the STAT3-induced MMP-9 signal pathway is involved in this process.

The blood-brain barrier as a target in traumatic brain injury treatment

Traumatic brain injury (TBI) is one of the most frequent causes of death in the young population. Several clinical trials have unsuccessfully focused on direct neuroprotective therapies. Recently immunotherapeutic strategies shifted into focus of translational research in acute CNS diseases. Cross-talk between activated microglia and blood-brain barrier (BBB) could initiate opening of the BBB and subsequent recruitment of systemic immune cells and mediators into the brain. Stabilization of the BBB after TBI could be a promising strategy to limit neuronal inflammation, secondary brain damage and acute neurodegeneration. This review provides an overview on the pathophysiology of TBI and brain edema formation including definitions and classification of TBI, current clinical treatment strategies, as well as current understanding on the underlying cellular processes. A summary of in vivo and in vitro models to study different aspects of TBI is presented. Three mechanisms proposed for stabilization of the BBB, myosin light chain kinases, glucocorticoid receptors and peroxisome proliferator-activated receptors are reviewed for their influence on barrier-integrity and outcome after TBI. In conclusion, the BBB is recommended as a promising target for the treatment of traumatic brain injury, and it is suggested that a combination of BBB stabilization and neuroprotectants may improve therapeutic success.

Possible implications of Ni(II) on oral IL-1β-induced inflammatory processes

OBJECTIVES

Nickel (Ni) is one of the main metal elements in orthodontic and prosthetic devices. Different effects of Ni are described ranging from an induction of local inflammation to allergy and cancerous/mutagenic properties. Inflammatory reactions are frequently observed in the oral cavity, but the interrelationship of Ni with those events is still unknown. Therefore, we focused on the impact of Ni on inflammation in vitro.

METHODS

In accordance to previous immersion tests of our lab, human gingival fibroblasts (HGFs) (n=6) were exposed to a pro-inflammatory environment using interleukin-1 beta (IL-1β) and additionally stimulated with different Ni(II) concentrations (400 and 4000ng/ml). At varying time points the expression of pro- and anti-inflammatory as well as matrix degeneration proteins, i.e. MMPs, were analyzed. Furthermore, proliferation assays, wound healing tests and the detection of NF-κB activation were conducted. Unstimulated HGFs served as control.

RESULTS

Our experiments showed that low clinical average Ni(II) levels did not alter pro-inflammatory cytokines significantly compared to control (p>0.05). Instead, a 10-fold higher dose up-regulated these mediators significantly in a time-dependent manner (p<0.01). This was even more pronounced combining both Ni(II) concentrations with an inflammatory condition (p<0.001), MMP expressions were in line with our findings (p<0.001). The mRNA data were supported by proliferation and wound closure assays (p<0.001). However, the combination of both stimuli induced contradictory results. Analyzing NF-κB activation revealed that our results may be in part attributed to NF-κB.

SIGNIFICANCE

Our in vitro study implicated that Ni(II) has various modifying effects on IL-1β-induced inflammatory processes depending on the concentration.

Psoriatic keratinocytes are resistant to tumor necrosis factor alpha's induction of mRNA for the NMDA-R2C subunit

Psoriatic individuals demonstrate accelerated healing and the Koebner phenomenon, suggesting that psoriatic proliferation of keratinocytes is not inhibited appropriately after skin injury. Serial analysis of gene expression in TNFα-exposed keratinocytes shows the greatest alteration in expression of NMDA-R2C. Expression of the NMDA receptor is altered in diseased skin containing TNFα, and TNFα plays a prominent role in psoriasis. An abnormality in induction of NMDA-R2C by TNFα in psoriatic keratinocytes may explain their lack of growth inhibition. We compared the capacity of TNFα to induce expression of NMDA-R2C in normal and psoriatic (involved and uninvolved) keratinocytes in vitro. After 72 h of incubation with TNFα, normal keratinocytes demonstrated a significant induction of NMDA-R2C mRNA compared with control cultures, whereas psoriatic keratinocytes showed no induction. In an in vitro model of wounding (scratches on monolayers), TNFα inhibited migration/proliferation of keratinocytes only at the edge of NMDA-R2C expressing wounded monolayers of normal keratinocytes.

Distinct phenotype and therapeutic potential of gingival fibroblasts

Gingiva of the oral mucosa provides a practical source to isolate fibroblasts for therapeutic purposes because the tissue is easily accessible, tissue discards are common during routine clinical procedures and wound healing after biopsy is fast and results in complete wound regeneration with very little morbidity or scarring. In addition, gingival fibroblasts have unique traits, including neural crest origin, distinct gene expression and synthetic properties and potent immunomodulatory functions. These characteristics may provide advantages for certain therapeutic approaches over other more commonly used cells, including skin fibroblasts, both in intraoral and extra-oral sites. However, identity and phenotype of gingival fibroblasts, like other fibroblasts, are still not completely understood. Gingival fibroblasts are phenotypically heterogeneous, and these…fibroblast subpopulations may play different roles in tissue maintenance, regeneration and pathologies. The purpose of this review is to summarize what is currently known about gingival fibroblasts, their distinct potential for tissue regeneration and their potential therapeutic uses in the future.

Insulin catalyzes the curcumin-induced wound healing: an in vitro model for gingival repair

OBJECTIVES

Human gingival fibroblasts (hGFs) play a major role in the maintenance and repair of gingival connective tissue. The mitogen insulin with IGFs etc. synergizes in facilitating wound repair. Although curcumin (CUR) and insulin regulate apoptosis, their impact as a combination on hGF in wound repair remains unknown. Our study consists of: 1) analysis of insulin-mediated mitogenesis on CUR-treated hGF cells, and 2) development of an in vitro model of wound healing.

MATERIALS AND METHODS

Apoptotic rate in CUR-treated hGF cells with and without insulin was observed by AnnexinV/PI staining, nuclear morphological analysis, FACS and DNA fragmentation studies. Using hGF confluent cultures, wounds were mechanically created in vitro and incubated with the ligands for 48 h in 0.2% fetal bovine serum DMEM.

RESULTS

CUR alone showed dose-dependent (1-50 μM) effects on hGF. Insulin (1 μg/ml) supplementation substantially enhanced cell survival through up-regulation of mitogenesis/anti-apoptotic elements.

CONCLUSIONS

The in vitro model for gingival wound healing establishes that insulin significantly enhanced wound filling faster than CUR-treated hGF cells over 48 h. This reinforces the pivotal role of insulin in supporting CUR-mediated wound repair. The findings have significant bearing in metabolic dysfunctions, e.g. diabetes, atherosclerosis, etc., especially under Indian situations.

Advanced glycation end products: possible link between metabolic syndrome and periodontal diseases

On a planetary scale, Metabolic Syndrome (MetS)is the third cause of inability after malnutrition and nicotinism, even higher than water shortage and sedentariness. In the USA, the prevalence is estimated at over 25 percent of the population; in Italy, it involves approximately 25 percent of men and even 27 percent of women. These are very high figures, corresponding to approximately 14 million affected individuals. The prevalence is alarming and must not be underestimated, particularly in the dental field, where more than one patient out of four sitting in a dentist chair is affected. The etiology of periodontal disease has not yet been clarified, and recently the idea to consider it as a multifactor pathology has been developed. Cofactors such as the formation of free radicals of oxygen (ROS), oxidative stress, lipid peroxidation, and formation of glycation end-products (AGEs) probably play an important role in the onset of periodontal disease. The AGEs are compounds physiologically produced by the cells. However, they accumulate and cause pro-inflammatory conditions, when the cellular clearance fails, or in hyperglycemic and oxidative states. All these conditions can be clinically summarized as Metabolic Syndrome. The purpose of this literature review is to establish a relationship between two pathologies with very high prevalence: Metabolic Syndrome and Periodontal Disorder. The literature seems to have clarified that MetS involves a pro-oxidation status, which induces AGE formation. AGEs play a very important role in the course and severity of periodontal diseases.

Interactions of adiponectin and lipopolysaccharide from Porphyromonas gingivalis on human oral epithelial cells

BACKGROUND

Periodontitis is an inflammatory disease caused by pathogenic microorganisms, such as Porphyromonas gingivalis, and characterized by the destruction of the periodontium. Obese individuals have an increased risk for periodontitis and show decreased serum levels of adiponectin. This in-vitro study was established to examine whether adiponectin modulates critical effects of lipopolysaccharide (LPS) from P. gingivalis on oral epithelial cells (OECs).

METHODOLOGY/PRINCIPAL FINDINGS

The presence of adiponectin and its receptors in human gingival tissue samples and OECs was analyzed by immunohistochemistry and PCR. Furthermore, OECs were treated with LPS and/or adiponectin for up to 72 h, and the gene expression and protein synthesis of pro- and anti-inflammatory mediators, matrix metalloproteinases (MMPs) and growth factors were analyzed by real-time PCR and ELISA. Additionally, cell proliferation, differentiation and in-vitro wound healing were studied. The nuclear translocation of NFκB was investigated by immunofluorescence. Gingival tissue sections showed a strong synthesis of adiponectin and its receptors in the epithelial layer. In cell cultures, LPS induced a significant up-regulation of interleukin (IL) 1β, IL6, IL8, MMP1 and MMP3. Adiponectin abrogated significantly the stimulatory effects of LPS on these molecules. Similarly, adiponectin inhibited significantly the LPS-induced decrease in cell viability and increase in cell proliferation and differentiation. Adiponectin led to a time-dependent induction of the anti-inflammatory mediators IL10 and heme oxygenase 1, and blocked the LPS-stimulated NFκB nuclear translocation.

CONCLUSIONS/SIGNIFICANCE

Adiponectin may counteract critical actions of P. gingivalis on oral epithelial cells. Low levels of adiponectin, as observed in obese individuals, may increase the risk for periodontal inflammation and destruction.

Effect of the cyclic stretch on the expression of osteogenesis genes in human periodontal ligament cells

Periodontal ligament cells can potentially differentiate into osteoblast-like cells and influence the remodeling of periodontal tissues under mechanical strain conditions. In the present study, Gene chip technology was adopted to investigate the effect of the cyclic stretch on the expression of osteogenic-related genes in human periodontal ligament cells (HPDLCs). Cultured HPDLCs were subjected to 12% elongation cyclic stretch for 24 h using a Flexercell Strain Unit, and then GEArray Q series human osteogenesis gene expression profile chip with 96 spot array numbers was used to conduct parallel analyses on the change of the related gene expression in the osteogenic differentiation of HPDLCs stimulated by cyclic stretch. The results show that after the HPDLCs were stimulated by the cyclic stretch, the expression of 21 osteogenic-related genes was significantly upregulated, including 10 growth factor genes and their associated molecules, 10 extracellular matrix genes and their associated proteins, and 1 cell adhesion molecule. Two genes were significantly downregulated, including one growth factor gene and one cell adhesion molecule. Then the expressions of 10 candidate genes were validated using Real-time RT-PCR. These results indicate that cyclic stretch with 12% deformation can stimulate or inhibit some gene expression which was associated with the process of HPDLCs differentiation.

Gene expression pattern during osteogenic differentiation of human periodontal ligament cells in vitro

Purpose

Periodontal ligament (PDL) cell differentiation into osteoblasts is important in bone formation. Bone formation is a complex biological process and involves several tightly regulated gene expression patterns of bone-related proteins. The expression patterns of bone related proteins are regulated in a temporal manner both in vivo and in vitro. The aim of this study was to observe the gene expression profile in PDL cell proliferation, differentiation, and mineralization in vitro.

Methods

PDL cells were grown until confluence, which were then designated as day 0, and nodule formation was induced by the addition of 50 µg/mL ascorbic acid, 10 mM β-glycerophosphate, and 100 nM dexamethasone to the medium. The dishes were stained with Alizarin Red S on days 1, 7, 14, and 21. Real-time polymerase chain reaction was performed for the detection of various genes on days 0, 1, 7, 14, and 21.

Results

On day 0 with a confluent monolayer, in the active proliferative stage, c-myc gene expression was observed at its maximal level. On day 7 with a multilayer, alkaline phosphatase, bone morphogenetic protein (BMP)-2, and BMP-4 gene expression had increased and this was followed by maximal expression of osteocalcin on day 14 with the initiation of nodule mineralization. In relationship to apoptosis, c-fos gene expression peaked on day 21 and was characterized by the post-mineralization stage. Here, various genes were regulated in a temporal manner during PDL fibroblast proliferation, extracellular matrix maturation, and mineralization. The gene expression pattern was similar.

Conclusions

We can speculate that the gene expression pattern occurs during PDL cell proliferation, differentiation, and mineralization. On the basis of these results, it might be possible to understand the various factors that influence PDL cell proliferation, extracellular matrix maturation, and mineralization with regard to gene expression patterns.

Possible involvement of advanced glycation end products in periodontal diseases

Periodontal diseases are considered as multifactorial conditions initiated by infection with pathogenic bacteria, promoted by inflammation and immune response against bacteria and modified by different environmental and genetic factors. Recently, interest in periodontal diseases has been increasing due to the awareness that the hyperinflammatory status associated with this disorder could impose a significant increase of reactive oxygen species (ROS) relevant to numerous systemic diseases driven by a pro-oxidant profile. A highly complex interplay occurs between oxidative stress and AGEs (Advanced Glycation End products), a group of heterogeneous compounds that form constantly under physiologic conditions, although their rate of formation is markedly increased in hyperglycemia and oxidizing conditions. Starting from the most relevant hypotheses on the pathogenesis of periodontal diseases, the present review outlines its relationship with oxidative stress and inflammation response in order to make a critical evaluation of the potential role of AGEs in periodontal deterioration. Although direct evidence for the presence of AGEs in the periodontal ligament is still lacking, valuable approaches based on the use of periodontal cells along with genetic and biochemical studies in animal models and chronic periodontal patients support a potential role for protein glycation in the aetiology and severity of this disease. Following a review of the current literature, the present study highlights the need for further investigation on the presence of AGEs in the periodontal ligament as a means for the comprehension of the pathogenic mechanisms underlying periodontal diseases in order to develop prevention and treatment modalities for this dysfunction.

Real-time PCR focused-gene array profiling of gingival and periodontal ligament fibroblasts

The techniques for the establishment of primary gingival and periodontal ligament fibroblast cultures have been well established for over 30 years. It is only more recently, with the commercial availability of real-time PCR (RT-PCR) gene arrays that the expression profiles of up to 84 genes can be carried out simultaneously. Each focused panel of genes can identify the up- or down-regulation of genes associated with any one of over 100 biological pathways or specific disease states. Fibroblasts for RNA extraction and subsequent gene expression analysis can be collected under various experimental conditions and stored in RNA-preserving solution (e.g., RNAlater) for processing at a later date or extracted immediately. The "gold standard" method for the extraction of RNA from fibroblasts for RT-PCR purposes is the TRIzol reagent method. With the addition of a spin-column clean-up step, any phenol carried over from the TRIzol step is removed, thus ensuring a high yield of quality RNA. The RNA is then reverse transcribed to cDNA and analyzed using the RT-PCR focused-gene arrays. Data analysis is made easy using on-line array analysis software packages.

Advanced glycation of type I collagen and fibronectin modifies periodontal cell behavior

BACKGROUND

Advanced glycation end products (AGEs) have been linked to pathogenic mechanisms of diabetes mellitus. However, little is known about the contribution of protein glycation to periodontal disease in patients with diabetes. Therefore, this study investigated whether glycation of type I collagen (COLI) and fibronectin (FN) modified the behavior of human gingival fibroblasts (hGFs) and periodontal ligament fibroblasts (hPDLs).

METHODS

Procedures for rapid in vitro glycation of COLI and FN used methylglyoxal (MG). Formation of AGEs was analyzed by changes in protein migration using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting with antibodies specific for MG-glycated proteins. Experiments then characterized the effects of glycated FN and COLI on the behavior of hGFs and hPDLs.

RESULTS

MG glycated COLI and FN in <6 hours. Confirming the specificity of the reactions, antibodies specific for MG-induced AGEs reacted with glycated FN and COLI but not with control proteins. In cell culture experiments, glycated FN was significantly less efficient in supporting the attachment of hGFs and hPDLs (P <0.05). Moreover, the morphologic parameters, including length, area, perimeter, and shape factor, were altered (P <0.001) for cells on both glycated proteins. Finally, cell migration was reduced on glycated FN and COLI (P <0.001).

CONCLUSIONS

MG treatment efficiently glycated COLI and FN, providing a new tool to study the effects of diabetes on periodontal disease. The substantial effects of glycated COLI and FN on hGF and hPDL behavior indicated that protein glycation contributed to the pathogenesis and altered periodontal wound healing observed in patients with diabetes.

Human Periodontal Fibroblast Response to Enamel Matrix Derivative, Amelogenin, and Platelet-Derived Growth Factor-BB

BACKGROUND

The ideal goal of clinical therapy in periodontal defects is regeneration of all lost structures. For regeneration to occur, cell proliferation, migration, and extracellular matrix synthesis are prerequisites. Attempts at regeneration of periodontal defects by guided tissue regeneration using bone grafts and membranes have not always yielded predictable results. Recently, attempts at engineering the defects using various materials have shown promising results. Two such approaches have been used to regenerate periodontal defects, one using extracellular matrix such as enamel matrix proteins and the other using growth factors. However, to our knowledge, no study has looked at combining these two approaches to achieve potentially even greater regeneration.

METHODS

Primary human periodontal ligament (PDL) fibroblasts were explanted, and alkaline phosphatase (ALK PHOS) activity was determined. Phenotypically different cell lines were incubated for 1, 3, 6, and 10 days in 0.2% fetal bovine serum (FBS) media containing different concentrations of either enamel matrix derivative (EMD), amelogenin, platelet-derived growth factor-BB (PDGF-BB), EMD+PDGF-BB, or amelogenin+PDGF-BB. A culture of 0.2% FBS alone served as a negative control, and a culture of 10% FBS served as a positive control. Cell proliferation was measured using a Coulter counter to determine the cell number. The effects on a wound-fill model were evaluated by scraping a 3-mm wide cell-free zone in PDL monolayers across the diameter of the tissue-culture plate and determining PDL cell migration into the cell-free zone using computer assisted histomorphometry.

RESULTS

Compared to the control, only EMD+PDGF-BB significantly increased PDL cell proliferation in an ALK PHOS (-) cell line (P<0.001), and EMD alone, EMD+PDGF-BB, and amelogenin+PDGF-BB significantly increased PDL cell proliferation in an ALK PHOS (+) cell line (P<0.001) with EMD+PDGF-BB showing a trend for greater proliferation than either PDGF or EMD alone. Individually, EMD and amelogenin had no significant effect on PDL cell proliferation. In the wound-fill experiment, all factors and their combinations except amelogenin significantly enhanced cell migration compared to the control (P<0.05) at the wound edge. In addition, EMD+PDGF-BB had additive effects on the ALK PHOS (-) cell line at the wound edge. At the center of the wound, neither EMD nor amelogenin had a significant wound-fill effect. However, the combination of EMD+PDGF-BB additively increased wound fill for both ALK PHOS (+) and ALK PHOS (-) cells.

CONCLUSIONS

The combination of EMD and PDGF-BB produces greater proliferative and wound-fill effects on PDL cells than each by themselves. If these combined effects can be translated clinically, one may see greater regeneration in periodontal defects with this combination. However, amelogenin does not have significant effects on PDL cell proliferation or migration by itself. This may suggest that either another enamel matrix component in EMD may be responsible for some of its clinical effects, or that amelogenin alone may not trigger the regenerative potential of periodontal tissues and that it requires a combined interaction with other enamel matrix components of EMD to direct the regenerative process.

Influence of Baicalin on the Expression of Receptor Activator of Nuclear Factor-κB Ligand in Cultured Human Periodontal Ligament Cells

BACKGROUND

Baicalin is a flavonoid purified from the medicinal plant Scutellaria baicalensis Georgi. It has been reported that baicalin exhibits antibacterial, anti-inflammatory and analgesic effects and can inhibit nuclear factor-kappaB activation. Periodontal disease is a chronic infective disease of the periodontium caused by bacteria present in dental plaque inducing alveolar bone resorption until teeth are lost. Human periodontal ligament (HPDL) is the connective tissue between alveolar bone and tooth. Receptor activator of nuclear factor-kappaB ligand (RANKL), a member of the tumor necrosis factor (TNF) ligand family, plays an important role in osteoclastogenesis from osteoclast precursors to mature osteoclasts. In this study we investigate the effects of baicalin on RANKL protein production and messenger RNA (mRNA) expression induced by IL-1beta in cultured HPDL cells.

METHODS

To induce RANKL expression, IL-1beta was added to serum-free medium HPDL cells and incubated. Various concentrations of baicalin (0, 0.001, 0.01 and 0.1 microg/ml) were added to the medium and the cells were treated for 0, 12, 24, 48 and 72 h, respectively. RANKL in the cells was detected using immunocytochemistry. The mRNA of RANKL, osteoprotegerin (OPG) and cyclooxygenase-2 (COX-2) were measured by semiquantitative reverse transcription-polymerase chain reaction.

RESULTS

The expression of RANKL at mRNA and protein levels in HPDL cells was stimulated by IL-1beta. Baicalin suppressed IL-1beta-induced RANKL and COX-2 production at a concentration of 0.01 microg/ml. The most prominent effect was observed with 48 h of baicalin treatment. The inhibition of baicalin on the rhIL-1beta-stimulated OPG expression was first apparent at 24 h after the start of treatment, however it did not reach significant differences.

CONCLUSIONS

The data suggest that baicalin may inhibit RANKL mRNA expression via the suppression of COX-2 expression induced by IL-1beta. In addition to its antibacterial and anti-inflammatory properties, baicalin was shown to be effective in periodontitis and alveolar bone resorption.

Tetracycline at Subcytotoxic Levels Inhibits Matrix Metalloproteinase-2 and -9 But Does Not Remove the Smear Layer

BACKGROUND

The antibacterial and anticollagenolytic properties of tetracycline (TCN) are valuable in periodontal therapy, and TCN treatment can remove the smear layer following root instrumentation. However, recent reports pointing to cytotoxic effects of several acids prompted this study to define TCN concentrations that are anticollagenolytic and remove the smear layer, but have low cytotoxicity.

METHODS

Human gingival (hGF) and periodontal ligament (hPDL) cells were treated short- (3 minutes) or long-term (24 hours) with TCN to determine concentrations yielding 50% (TD(50)) and 90% (TD(10)) cell survival. Activity assays measured TCN concentrations with half-maximal inhibition (IC(50)) of matrix metalloproteinase- 2 and -9 (MMP-2 and -9). Finally, we analyzed the effects of TCN with high (75 mg/ml) or low (1 mg/ml) cytotoxicity on the smear layer by scanning electron microscopy (SEM).

RESULTS

The TD(50) for TCN after short-term treatment was 4 mg/ml for both hGF and hPDL. Ninety percent of the cells survived 0.2 mg/ml. With long-term treatment, the TD(50) for hGF and hPDL was 70 and 30 microg/ml, respectively, and the TD(10) was 20 and 5 microg/ml. HGF and hPDL recovered from the 3-minute treatment with 1 mg/ml, but not from concentrations exceeding 3 and 9 mg/ml, respectively. The IC(50) was 25 microg/ml for both MMP-2 and MMP-9. Whereas 75 mg/ml TCN removed the smear layer, 1 mg/ml TCN had no effects.

CONCLUSIONS

Tetracycline has significant cytotoxicity on periodontal cells. Since non-cytotoxic concentrations of TCN inhibited MMP-2 and -9 but had no effects on the smear layer, TCN is not recommended for root surface treatment.

Lysophosphatidic acid modulates the regenerative responses of human gingival fibroblasts and enhances the actions of platelet-derived growth factor

BACKGROUND

Platelet-derived growth factor (PDGF) has been used to promote healing in many in vitro and in vivo models of periodontal regeneration. PDGF is known to interact extensively with another platelet mediator, lysophosphatidic acid (LPA), to enhance regenerative responses in non-oral systems. PDGF and LPA are both liberated by platelets in the blood clot, which is known to be critical in stabilizing early periodontal wound healing. The purpose of this study was to evaluate the basic interactions of LPA with primary human gingival fibroblasts (GF) alone and with PDGF-BB for promoting GF growth and migration, as well as their effects in an in vitro oral wound-healing model.

METHODS

GF regenerative responses were measured using 1 and 10 microM LPA in the absence or presence of 1 or 10 ng/ml PDGF-BB. Cell growth was determined using [3H]thymidine incorporation and cell counting. Migration responses were measured using a microchemotaxis chamber. For the in vitro wound-healing experiments, GF were grown to confluence on glass slides, and a 3 mm wide wound was mechanically inflicted. Percent wound fill on days 4, 6, and 9 was analyzed using computer-assisted histomorphometry.

RESULTS

GF exhibited proliferative and chemotactic responses to LPA. These responses were synergistic when LPA and PDGF-BB were present together. LPA on its own did not stimulate statistically significant wound fill, but when combined with PDGF-BB, wound fill was equivalent to the 10% serum positive control group by day 6 (5.5-fold of negative control, [P<0.001]) and again on day 9 (6-fold of negative control, [P<0.001]).

CONCLUSIONS

These studies provide the first evidence that LPA stimulates human GF regenerative responses and that it interacts positively with PDGF-BB to regulate these actions. The results suggest that LPA needs to be further investigated in the oral system as a factor that should be considered for incorporation when designing new periodontal wound-healing therapies using PDGF.

Platelet-Derived Growth Factor-BB Stimulated Cell Migration Mediated Through p38 Signal Transduction Pathway in Periodontal Cells

BACKGROUND

Intracellular signaling pathways mediate specific responses to growth factors. The manipulation of these pathways ultimately may be used to control the clinical outcomes of periodontal regenerative therapy. The purpose of this study was to examine the role of the p38 signal transduction pathway in the responses of periodontal cells to platelet-derived growth factor-BB (PDGF).

METHODS

Primary cultures of human periodontal ligament cells (PDLs) and gingival fibroblasts (GFs) were used for all experiments. Cell numbers, 3H-thymidine incorporation, and Boyden chamber assays were used to characterize the effects of SB 203580 (SB), a specific inhibitor of the p38 signaling pathway, on cell proliferation and migration. An in vitro wound model also was used to assess the effects of SB. For the in vitro wound assay, triplicate wells were incubated for 1, 3, 5, and 7 days using 0.1% fetal bovine serum (FBS), 10% FBS +/- 10 microM SB, or 20 ng/ml PDGF +/- 10 microM SB. Digital histomorphometric analysis assessed cellular fill within the wound area.

RESULTS

SB specifically inhibited PDGF-induced migration in the Boyden chamber assays without affecting cell proliferation. The wound model data showed similar levels of wound fill for PDLs and GFs in 10% FBS. Relative to 10% FBS, PDLs stimulated with PDGF showed significantly (P < 0.01, analysis of variance) greater wound fill (74%) than GFs (12%). SB inhibited the PDGF-induced wound fill of PDLs and GFs by 64% and 57%, respectively. This inhibition was significant (P < 0.01, ANOVA) only for PDLs. The addition of SB to 10% FBS did not significantly affect the wound fill response of either cell type compared to 10% FBS alone.

CONCLUSIONS

These results demonstrate that periodontal cells possess distinct responses to PDGF that may be altered at the signal transduction level. The manipulation of these responses through the use of inhibitors to specific signaling pathways may enhance our control of periodontal regeneration in the future.

Role of Insulin-Like Growth Factor-1 Signaling in Dental Fibroblast Apoptosis

BACKGROUND

Studies have shown that periodontal ligament fibroblasts (PDLF) and gingival fibroblasts (GF) respond differently to growth factors in the repair and regeneration of periodontal tissues. The goal of this study was to determine the effects of insulin-like growth factor-1 (IGF-1) signaling on cell apoptosis in PDLF compared to GF.

METHODS

The levels of apoptosis were compared between cultured PDLF and GF by DNA fragmentation assay and trypan blue exclusion assay, either in the presence or absence of IGF-1. The transcript level of upstream signaling molecules, such as IGF binding protein-5 (IGFBP-5), IGF-1 receptor (IGF-1R), and phosphoinositide 3-kinase (PI3K), was studied using reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, the role of IGFBP-5 in IGF-1 signaling was verified by annexin-V staining using flow cytometric analysis.

RESULTS

IGF-1 significantly inhibited the level of DNA fragmentation and decreased trypan blue-positive cells in PDLF compared to GF during serum deprivation. The mRNA expression of IGFBP-5, IGF-1R, and PI3K was constitutively upregulated in PDLF compared to GF. In the presence of exogenous IGFBP-5, the annexin-V-positive cells were significantly decreased in GF after IGF-1 stimulation.

CONCLUSIONS

The present study provides evidence that IGF-1 reduces apoptosis in cultured PDLF compared to GF. Upregulation of IGF-1R and PI3K in PDLF further suggests the activation of IGF signaling in PDLF. In addition, the anti-apoptotic effect of IGF-1 may be facilitated by the upregulation of IGFBP-5 in PDLF.

IGF-1 signaling enhances cell survival in periodontal ligament fibroblasts vs. gingival fibroblasts

The role of insulin-like growth factors (IGFs) in the regulation of apoptosis has been suggested, yet their impact on specific cells such as periodontal ligament fibroblasts (PDLF) and gingival fibroblasts (GF) remains unknown. The purpose of this study was to test the role of IGF-1 signaling in cell survival in PDLF compared with GF. In periodontal tissue sections, a significantly reduced apoptotic rate was first demonstrated in PDLF compared with GF. In vitro, IGF-1 substantially enhanced cell survival in PDLF compared with GF by the up-regulation of anti-apoptotic molecules and the down-regulation of pro-apoptotic molecules. Furthermore, the differential expression of insulin-like growth factor binding protein 5 (IGFBP-5) was observed in vitro, and its differential distribution was confirmed in vivo. Analysis of the present data suggests an enhanced cell survival in PDLF compared with GF by the up-regulation of IGF-1 signaling pathway.

In vitro evaluation of the mitogenic effect of platelet-derived growth factor-BB on human periodontal ligament cells cultured with various bone allografts

BACKGROUND

Several studies have documented the role of growth factors in periodontal regeneration. It has been shown that platelet-derived growth factor (PDGF) is a potent stimulator of human periodontal ligament (PDL) cells. A variety of bone graft materials are used to treat osseous defects caused by periodontal disease. We evaluated the mitogenic effect of PDGF on human PDL cells cultured with different allografts to determine which of the allografts with or without PDGF promoted periodontal regeneration.

METHODS

Two human demineralized freeze-dried allografts of cortical (DFDBA) and cancellous (DFBA) bone and a non-demineralized freeze-dried allograft (FBA) from cancellous bone were used alone or supplemented with PDGF-BB. Human PDL cultures were derived from the mid-root of 2 maxillary premolars extracted for orthodontic reasons. Cells were grown separately in 24-well dishes with or without 20 mg of each bone allograft. On day 2 of quiescence, new medium was added with 10 ng/ml of PDGF-BB. DNA synthesis was estimated by measuring [3H] thymidine incorporation to determine the effects of the test agents on cell proliferation. Cells were processed and subjected to scintillation counting after 48 hours of incubation. Counts per minute (cpm/well) were determined for each sample.

RESULTS

There was no statistically significant difference (P<0.05) on PDL cell proliferation when the allografts were used alone. PDL cells exhibited significantly greater proliferative responses to the 2 demineralized bone allografts, DFDBA and DFBA, when combined with PDGF-BB. A statistically significant difference on DNA synthesis was noticed when PDGF-BB was added to PDL cells cultured with FBA. PDL cells displayed no significant increase in mitogenic activity when cultured with PDGF-BB alone.

CONCLUSIONS

The findings of this study demonstrate the beneficial role of DFDBA, DFBA, and FBA as synergic agents with PDGF-BB to periodontal regeneration. The significant ability of the 2 decalcified bone allografts, DFDBA and DFBA, combined with PDGF to stimulate PDL cell proliferation might be a useful adjunct in the treatment of periodontal defects.

The induction of c-fos mRNA expression by mechanical stress in human periodontal ligament cells

The periodontal ligament is subjected to mechanical loading during occlusion and mastication. Although internuclear transcription factors are associated with the regulatory pathway that converts these extracellular mechanical stimuli into a cellular response, there are no reports on these in human periodontal ligament fibroblasts. In this study, the amounts of c-fos mRNA in human periodontal ligament fibroblasts were investigated shortly after subjecting them to a cyclic tension force in vitro. The mRNA of alkaline phosphatase and the matrix proteins type I collagen, type III collagen, matrix Gla-protein, osteonectin, osteopontin, and osteocalcin were also examined. A significant, rapid, transient increase in c-fos mRNA was detected, which peaked 30 min after the application of mechanical force. However, there was no significant change in the mRNA for alkaline phosphatase or the matrix proteins. These results provide evidence that periodontal ligament fibroblasts and c-fos may play a critical part in the response of periodontal tissue to mechanical stimulation.

Differences in motility pattern between human buccal fibroblasts and periodontal and skin fibroblasts

Migration of fibroblasts from surrounding normal tissue into the wound bed is an important requirement for successful wound healing. This study investigated the motility pattern of buccal, periodontal and skin fibroblasts to determine whether differences in the wound healing efficiency at these sites can be explained by differences in the motile behavior of their respective fibroblast populations. The migratory characteristics were studied in a two-dimensional culture system. The migration of single cells was time-lapse video recorded at intervals of 15 min for a period of 6 h using a computer-assisted microscope work-station. For evaluation of cell morphology, cell contours were recognized semiautomatically and used for determination of cell area, cell spreading and number and length of processes. We found that the cellular displacement of the buccal fibroblasts was only approximately 50% of the cellular displacement of periodontal and skin fibroblasts. The decreased cellular displacement of the buccal fibroblasts was found to be due to both lower cellular speed and less persistence in direction. The buccal fibroblasts also displayed smaller areas and longer processes. The differences in cellular morphology and motility pattern amongst the three fibroblast types could not be explained by differences in secretion of extracellular matrix components and are therefore believed to reflect phenotypic differences amongst fibroblast subpopulations.

Isolation and characterization of cultured human periodental ligament fibroblast-specific cDNAs

The molecular mechanisms that control the function of periodontal ligament (PDL) fibroblasts remain unclear. We speculated that the character of differentiating PDL fibroblasts is defined by the altered expansion of specific genes not found in neighboring gingival fibroblasts in the periodontium. To expand this set, subtractive hybridization was applied between cultured human PDL and gingival fibroblasts to identify genes differentially expressed in PDL. Consequently five candidate clones, PDLs (periodontal ligament specific) 5, -17, -22, -25, and -31 were identified and characterized by homology search, Northern analysis, and in situ hybridization. Although the mRNAs of these clones were expressed by bone marrow cells and rarely by gingival fibroblasts, the highest expression was detected in the PDL cells, which were uniformly distributed throughout the whole PDL. Amongst the five candidate clones, we focused on PDLs17, because it is a hypothetical protein whose biological function has not been reported yet in the database. Polyclonal antiserum raised against PDLs17 peptide was made, and stained the PDL fibroblasts, osteoblast-like cells and stromal cells in the bone marrow, but not gingival fibroblasts. The results suggest that clones, PDLs5, -17, -22, -25, and -31 may be used as PDL fibroblast-specific markers, and that PDLs17 could act as an important factor in the differentiation process of PDL fibroblasts.

The effects of platelet-derived growth factor-BB on periodontal cells in an in vitro wound model

BACKGROUND

Platelet-derived growth factor (PDGF-BB) has been shown to enhance periodontal regeneration. Principles of guided tissue regeneration dictate that one of the goals of therapy is to modulate the wound healing processes to favor repopulation of the wound with cells derived from the periodontal ligament rather than from the gingival tissues. Using an in vitro wound model, gingival fibroblasts (GF) have been shown to fill a wound space significantly faster than periodontal ligament cells (PDL). There are no data reported directly comparing the response of these 2 cell types to PDGF-BB within such a wound model. Therefore, the aims of this research were: 1) to characterize both the proliferative and wound fill (WF) effects of PDGF-BB within an in vitro model and 2) to compare specific growth factor effects between GF and PDL.

METHODS

Primary cultures of both human PDL and GF were derived from explanted tissues and passaged to 12-well tissue culture plates. Triplicate cultures of both cell types were grown to confluence and in vitro wounds were mechanically created, removing a 3 mm wide band of the cell layer across the diameter of the wells. The wells were then incubated for 2, 6, and 9 days in media containing 0.1% fetal bovine serum (FBS) and 1 of 5 concentrations of PDGF-BB. At each time point, cells were pulsed with 5-bromo, 2-deoxyuridine (BrdU) fixed, and nuclei were stained to measure BrdU incorporation (as a measure for proliferation). Cells were counter-stained with cytoplasmic stain to measure cell number. Quantitative analyses within the wound boundaries, marginally (area of interest [AOI] 1) and centrally (AOI 2), were accomplished using computer-assisted histomorphometry.

RESULTS

PDL exhibited a significantly greater proliferative response to PDGF-BB in both AOI when compared to GF (P <0.0001). The PDL exhibited increased levels of proliferation at concentrations of PDGF-BB greater than or equal to 10 ng/ml. By contrast, GF displayed no increase in proliferation in response to stimulation with PDGF-BB at any of the concentrations tested when compared to negative controls. The wound fill (WF) responses to PDGF-BB were similar between PDL and GF, with both cell types responding in an all or none fashion when measured at day 2, and in a concentration-dependent manner at later time points. The only significant difference in WF between PDL and GF occurred in AOI 2 in negative control medium (0 ng/ml of PDGF-BB), with GFs having greater (P <0.01) levels of WF over the 9 days.

CONCLUSION

The findings from this study demonstrate differing effects of PDGF-BB on the proliferation of PDL and GF in this in vitro model. These results suggest that there may be cell-specific differences critical to periodontal wound healing that may be exploited in the development of new therapies.

Characterization of proliferation and cellular wound fill in periodontal cells using an in vitro wound model

BACKGROUND

The therapeutic success of periodontal regenerative therapy may be compromised by our limited understanding of the wound healing process. Wound healing requires the coordination of complex cellular and molecular interactions. Recently, using an in vitro wound model, our laboratory has shown that gingival fibroblasts (GF) fill an in vitro wound more rapidly than periodontal ligament cells (PDL). This suggests that there may be differences in the levels of proliferation for these 2 cell types during the wound healing process. Such specific cell type differences may be significant in clinical outcomes of regenerative therapy. Therefore, the aim of this research was to characterize and compare the levels of both proliferation and cellular wound fill between GF and PDL using our in vitro wound model.

METHODS

Primary cultures of human PDL and GF cells were established from explanted tissue, and passaged to 12-well tissue culture plates. Triplicate cultures of both cell types were grown to confluence and in vitro wounds were mechanically created, removing a 3 mm wide band of the cell layer across the diameter of the wells. The wells were then incubated for 2, 6, or 9 days in media containing either 0.1% or 10% fetal bovine serum (FBS). At each time point, cells were pulsed with 5-bromo, 2-deoxyuridine (BrdU), fixed, and nuclei stained to measure DNA synthesis (as a measure for proliferation). Cells were counter stained with cytoplasmic stain to measure cell number. Quantitative analysis distant from (area of interest [AOI 1]), next to (AOI 2), and within the wound boundaries (AOI 3 and 4) was accomplished using computer-assisted histomorphometry.

RESULTS

The levels of proliferation and cellular fill for each cell type were assessed relative to time and AOI. Overall, the PDL displayed greater (P <0.01) levels of proliferation than the GF. For both cell types, proliferation was found to be significantly (P<0.001) greater at day 2 compared to other time points. PDL displayed greater levels of proliferation than GF in all AOI, with this difference reaching significance (P<0.02) within the cell layer (AOI 1 and 2). When comparing levels of cellular fill in 10% FBS, GF displayed greater wound fill than the PDL. This difference was significant at day 6 (P <0.05) for both the marginal (AOI 3) and central (AOI 4) portions of the wound.

CONCLUSIONS

These findings, demonstrating unique differences between PDL and GF with respect to proliferation and wound fill in an in vitro model, suggest that there may be cell-specific differences in cellular activity critical to periodontal wound healing. In addition, the results of this study show that the cellular proliferation response may not accurately reflect the overall wound healing response.

In vitro wound healing responses to enamel matrix derivative

BACKGROUND

Enamel matrix derivative (EMD) contains a variety of hydrophobic enamel matrix proteins and is extracted from developing embryonal enamel of porcine origin. EMD has been associated with the formation of acellular cementum and it has been found to stimulate periodontal regeneration. The present study was established to investigate the influence of EMD on human periodontal ligament (PDL) cells, gingival fibroblasts (GF), and osteosarcoma (MG-63) cells on wound-fill rates using an in vitro wound model.

METHODS

Wounds were created by making 3 mm incisions in cell monolayers across the length of tissue culture plates. The wounded PDL, GF, and MG-63 cell monolayers were treated with media containing EMD over a concentration range of 5 to 100 microg/ml, platelet-derived growth factor (PDGF-BB) at 20 ng/ml as a positive control and insulin-like growth factor (IGF-I) at 100 ng/ml as a negative control. PDL cell wounded monolayers also were treated in EMD coated tissue culture plates. After an incubation period (up to 9 days), the cells were fixed and stained and cellular fill was measured across the width of the wound by computer-assisted histomorphometry.

RESULTS

When PDL, GF, and MG-63 cells were exposed to EMD in culture medium, an enhanced wound-fill was observed for all cells compared to untreated conditions. At early time points, PDL wound-fill rates in the presence of EMD were statistically greater than the rates of GF and MG-63 treated with EMD (P<0.001). There were no significant differences in wound-fill rates of PDL cells treated with EMD in medium versus EMD coated on culture plates. At days 3 and 6 post-wounding, PDL cells showed a significantly greater response to EMD than to PDGF-BB (P <0.001). EMD also had a greater effect on GF wound-fill rates than PDGF-BB at days 6 and 9. MG-63 cells were less responsive to PDGF-BB and EMD than PDL cells and GF. All 3 cell types treated with IGF-I showed no significant increase of wound-fill rates.

CONCLUSION

The present data support the concept that clinical application of enamel matrix derivative may enhance periodontal wound regeneration by specifically modifying periodontal ligament cell proliferation and migration.