Efficacy of stem cells on periodontal regeneration: Systematic review of pre-clinical studies.

This systematic review aims to evaluate mesenchymal stem cells (MSC) periodontal regenerative potential in animal models. MEDLINE, EMBASE and LILACS databases were searched for quantitative pre-clinical controlled animal model studies that evaluated the effect of local administration of MSC on periodontal regeneration. The systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement guidelines. Twenty-two studies met the inclusion criteria. Periodontal defects were surgically created in all studies. In seven studies, periodontal inflammation was experimentally induced following surgical defect creation. Differences in defect morphology were identified among the studies. Autogenous, alogenous and xenogenous MSC were used to promote periodontal regeneration. These included bone marrow-derived MSC, periodontal ligament (PDL)-derived MSC, dental pulp-derived MSC, gingival margin-derived MSC, foreskin-derived induced pluripotent stem cells, adipose tissue-derived MSC, cementum-derived MSC, periapical follicular MSC and alveolar periosteal cells. Meta-analysis was not possible due to heterogeneities in study designs. In most of the studies, local MSC implantation was not associated with adverse effects. The use of bone marrow-derived MSC for periodontal regeneration yielded conflicting results. In contrast, PDL-MSC consistently promoted increased PDL and cementum regeneration. Finally, the adjunct use of MSC improved the regenerative outcomes of periodontal defects treated with membranes or bone substitutes. Despite the quality level of the existing evidence, the current data indicate that the use of MSC may provide beneficial effects on periodontal regeneration. The various degrees of success of MSC in periodontal regeneration are likely to be related to the use of heterogeneous cells. Thus, future studies need to identify phenotypic profiles of highly regenerative MSC populations.

Anticandidal activity and biocompatibility of a rechargeable antifungal denture material.

OBJECTIVES: Candida-associated denture stomatitis is a recurrent and debilitating oral mucosal disease. Development of anticandidal denture materials represents a promising strategy to manage this condition. We have previously shown that miconazole incorporated in methacrylic acid (MAA) copolymerized diurethane dimethacrylate (UDMA) denture materials has long-term anticandidal activity. In this study, we examined the ability of culture medium conditioned with drug-free- or miconazole-MAA-UDMA discs to prevent Candida infection in an in vitro oral epithelial cell/Candida albicans coculture system. MATERIALS AND METHODS: Candida albicans (C. albicans)-induced OKF6/TERT-2 cell damage was quantified by the release of lactate dehydrogenase from epithelial cells, cytokine production was quantified using protein cytokine arrays, and the expression of C. albicans genes was measured by RT-qPCR. RESULTS: Candida albicans had limited growth with altered expression levels of secreted aspartyl proteinase-2 and -5 in culture medium conditioned by miconazole-MAA-UDMA discs. Significantly, the ability of C. albicans to induce oral epithelial cell damage and trigger epithelial proinflammatory cytokine production was also inhibited by miconazole disc conditioned media. CONCLUSION: Miconazole released from MAA-UDMA denture materials effectively prevents the development of candidal infection in an in vitro oral epithelial system. Further characterization of this drug-rechargeable denture material is warranted.

Candida albicans induces early apoptosis followed by secondary necrosis in oral epithelial cells.

The capacity of Candida albicans to invade and damage oral epithelial cells is critical for its ability to establish and maintain symptomatic oropharyngeal infection. Although oral epithelial cells are reported dead after 18 h of candidal infection, activation of specific epithelial cell-death pathways in response to C. albicans infection has not yet been demonstrated. Considering the key role of oral epithelial cell damage in the pathogenesis of oropharyngeal candidiasis, the aim of this study was to characterize this event during infection. Using an oral epithelial-C. albicans co-culture system, we examined the ability of C. albicans to induce classic necrotic, pyroptotic and apoptotic cellular alterations in oral epithelial cells such as osmotic lysis, exposure of phosphatidylserine on the epithelial cell plasma membrane and internucleosomal DNA fragmentation. It was found that the ability of C. albicans to kill oral epithelial cells depends on its capacity to physically interact with and invade these cells. Caspase-dependent apoptotic pathways were activated early during C. albicans infection and contributed to C. albicans-induced oral epithelial cell death. Earlier apoptotic events were followed by necrotic death of infected oral epithelial cells. Hence, C. albicans stimulates oral epithelial signaling pathways that promote early apoptotic cell death through the activation of cellular caspases, followed by late necrosis.

Mucosal tissue invasion by Candida albicans is associated with E-cadherin degradation, mediated by transcription factor Rim101p and protease Sap5p.

The ability of Candida albicans to invade mucosal tissues is a major virulence determinant of this organism; however, the mechanism of invasion is not understood in detail. Proteolytic breakdown of E-cadherin, the major protein in epithelial cell junctions, has been proposed as a mechanism of invasion of certain bacteria in the oral mucosa. The objectives of this study were (i) to assess whether C. albicans degrades E-cadherin expressed by oral epithelial cells in vitro; (ii) to compare the abilities of strains with different invasive potentials to degrade this protein; and (iii) to investigate fungal virulence factors responsible for E-cadherin degradation. We found that while E-cadherin gene expression was not altered, E-cadherin was proteolytically degraded during the interaction of oral epithelial cells with C. albicans. Moreover, C. albicans-mediated degradation of E-cadherin was completely inhibited in the presence of protease inhibitors. Using a three-dimensional model of the human oral mucosa, we found that E-cadherin was degraded in localized areas of tissue invasion by C. albicans. An invasion-deficient rim101-/rim101- strain was deficient in degradation of E-cadherin, and this finding suggested that proteases may depend on Rim101p for expression. Indeed, reverse transcription-PCR data indicated that expression of the SAP4, SAP5, and SAP6 genes is severely reduced in the rim101-/rim101- mutant. These SAP genes are functional Rim101p targets, because engineered expression of SAP5 in the rim101-/rim101- strain restored E-cadherin degradation and invasion in the mucosal model. Our data support the hypothesis that there is a mechanism by which C. albicans invades mucosal tissues by promoting the proteolytic degradation of E-cadherin in epithelial adherens junctions.

Therapeutic modulation of cytokines in chronic infectious diseases.

The recent increase in immunocompromised patient populations, including HIV-infected patients, cancer patients with chemotherapy-induced neutropenia, and transplant recipients receiving immunosuppressive therapy, has led to an increased incidence of clinically significant chronic opportunistic infections. Traditional treatment of chronic persistent infections has strongly relied on the use of antimicrobial drugs. However, unsatisfactory results with drug monotherapy and emergence of resistant strains have prompted the use of adjunctive cytokine therapies for the treatment of these infections. During the past decade, a wide spectrum of immunomodulators has been tested in human clinical trials and animal models of chronic infections caused by a variety of bacteria, fungi, viruses and parasites. This review compiles recent information on advances in the use of cytokines as a therapeutic strategy in chronic bacterial, parasitic, fungal and viral infections.

Invasive phenotype of Candida albicans affects the host proinflammatory response to infection.

Candida albicans is a major opportunistic pathogen in immunocompromised patients. Production of proinflammatory cytokines by host cells in response to C. albicans plays a critical role in the activation of immune cells and final clearance of the organism. Invasion of host cells and tissues is considered one of the virulence attributes of this organism. The purpose of this study was to investigate whether the ability of C. albicans to invade host cells and tissues affects the proinflammatory cytokine responses by epithelial and endothelial cells. In this study we used the invasion-deficient RIM101 gene knockout strain DAY25, the highly invasive strain SC5314, and highly invasive RIM101-complemented strain DAY44 to compare the proinflammatory cytokine responses by oral epithelial or endothelial cells. Using a high-throughput approach, we found both qualitative and quantitative differences in the overall inflammatory responses to C. albicans strains with different invasive potentials. Overall, the highly invasive strains triggered higher levels of proinflammatory cytokines in host cells than the invasion-deficient mutant triggered. Significant differences compared to the attenuated mutant were noted in interleukin-1alpha (IL-1alpha), IL-6, IL-8, and tumor necrosis factor alpha in epithelial cells and in IL-6, growth-related oncogene, IL-8, monocyte chemoattractant protein 1 (MCP-1), MCP-2, and granulocyte colony-stimulating factor in endothelial cells. Our results indicate that invasion of host cells and tissues by C. albicans enhances the host proinflammatory response to infection.

Role of Candida albicans polymorphism in interactions with oral epithelial cells.

BACKGROUND: Candida albicans is a polymorphic organism which undergoes morphologic transition between yeast, pseudohyphal and hyphal forms. The ability of C. albicans to change from yeast to filamentous types is a major virulence determinant of this organism. However, the exact role of hyphal transformation in establishing oral mucosal infection is still poorly understood. METHODS: In this study we used mutants with defects in filamentation, as well as oral strains, which differ in their capacity to form true hyphae, to examine the role of hyphal transformation in the interactions of C. albicans with oral epithelial cells in vitro. These interactions included the ability of these strains to adhere to and injure epithelial cells, as well as their ability to trigger a proinflammatory cytokine response. RESULTS: We found that strains SC5314 and ATCC28366 formed true hyphae on epithelial cells, whereas strain ATCC32077 and the tup1/tup1 mutant formed only pseudohyphae. Double mutant efg1/efg1cph1/cph1 grew exclusively as blastospores. We also found that yeast and pseudohyphal strains showed reduced adherence capacity to oral keratinocytes and caused minimal cell damage. Moreover, we showed that both yeast and pseudohyphal forms have a strongly attenuated proinflammatory phenotype, since they failed to induce significant interleukin (IL)-1alpha and IL-8 responses by oral epithelial cells. CONCLUSIONS: Germination of C. albicans into true hyphae is particularly important in the interactions with oral epithelial cells in vitro.