Periodontal ligament-derived cells for periodontal regeneration in animal models: a systematic review.

BACKGROUND AND OBJECTIVE: Implantation of periodontal ligament stem cells is emerging as a potential periodontal regenerative procedure. This systematic review considers the evidence from animal models investigating the use of periodontal ligament stem cells for successful periodontal regeneration. MATERIAL AND METHODS: PubMed, Embase, MEDLINE and Google Scholar were searched to December 2013 for quantitative studies examining the outcome of implanting periodontal ligament stem cells into experimental periodontal defects in animals. Inclusion criteria were: implantation of periodontal ligament stem cells into surgically created periodontal defects for periodontal regeneration; animal models only; source of cells either human or animal; and published in English. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. RESULTS: From the literature search, 43 studies met the inclusion criteria. A wide variety of surgical defects were created in four species of animal (dog, rat, pig and sheep). Owing to wide variability in defect type, cell source and cell scaffold, no meta-analysis was possible. Outcome measures included new bone, new cementum and new connective tissue formation. In 70.5% of the results, statistically significant improvements of these measures was recorded. CONCLUSION: These results are notable in that they indicate that irrespective of the defect type and animal model used, periodontal ligament stem cell implantation can be expected to result in a beneficial outcome for periodontal regeneration. It is recommended that there is sufficient evidence from preclinical animal studies to warrant moving to human studies to examine the efficacy, safety, feasibility (autologous vs. allogeneic transplantation) and delivery of periodontal ligament stem cells for periodontal regeneration.

Cementum and Periodontal Ligament Regeneration.

The unique anatomy and composition of the periodontium make periodontal tissue healing and regeneration a complex process. Periodontal regeneration aims to recapitulate the crucial stages of wound healing associated with periodontal development in order to restore lost tissues to their original form and function and for regeneration to occur, healing events must progress in an ordered and programmed sequence both temporally and spatially, replicating key developmental events. A number of procedures have been employed to promote true and predictable regeneration of the periodontium. Principally, the approaches are based on the use of graft materials to compensate for the bone loss incurred as a result of periodontal disease, use of barrier membranes for guided tissue regeneration and use of bioactive molecules. More recently, the concept of tissue engineering has been integrated into research and applications of regenerative dentistry, including periodontics, to aim to manage damaged and lost oral tissues, through reconstruction and regeneration of the periodontium and alleviate the shortcomings of more conventional therapeutic options. The essential components for generating effective cellular based therapeutic strategies include a population of multi-potential progenitor cells, presence of signalling molecules/inductive morphogenic signals and a conductive extracellular matrix scaffold or appropriate delivery system. Mesenchymal stem cells are considered suitable candidates for cell-based tissue engineering strategies owing to their extensive expansion rate and potential to differentiate into cells of multiple organs and systems. Mesenchymal stem cells derived from multiple tissue sources have been investigated in pre-clinical animal studies and clinical settings for the treatment and regeneration of the periodontium.

The association between breastfeeding, maternal smoking in utero, and birth weight with bone mass and fractures in adolescents: a 16-year longitudinal study.

UNLABELLED: The aim of this birth cohort study was to determine whether early life factors (birth weight, breastfeeding, and maternal smoking) were associated with bone mass and fractures in 16-year-old adolescents. The results suggest that breastfeeding is associated with higher bone mass and lower fracture risk at age 16 but not in utero smoking or birth weight. INTRODUCTION: There are limited data on early life influences on bone mass in adolescence but we have previously reported in utero smoking, breastfeeding, and birth weight were associated with bone mass at age 8. METHODS: Birth weight, breastfeeding intention and habit, and maternal smoking during pregnancy were assessed at phase one in 1988-1999 and by recall during phase two in 1996-1997. Bone mineral density (BMD) was measured by dual-energy X-ray densitometry. Fractures were assessed by questionnaire. Subjects included 415 male and female adolescents from Southern Tasmania representing 29 % of those who originally took part in a birth cohort study in 1988 and 1989. RESULTS: Breastfeeding (assessed in a number of ways) was associated with a 2-3 % increase in BMD at all sites apart from the radius and around a one third reduction in fracture risk which persisted after adjustment for confounders. In univariate analysis, birth weight was associated with BMD at the hip, radius, and total body but this did not persist in multivariate analysis and there was no association with fracture. Smoking in utero had no association with BMD at any site or fracture. CONCLUSIONS: Breastfeeding is associated with a beneficial increase in bone mass at age 16 and a reduction in fracture risk during adolescence. The association previously observed at 8 years of age is no longer present for birth weight or smoking in utero.

Potential of iPSC-Derived Mesenchymal Stromal Cells for Treating Periodontal Disease.

Mesenchymal stromal cell-like populations have been derived from mouse-induced pluripotent stem cells (miPSC-MSC) with the capability for tissue regeneration. In this study, murine iPSC underwent differentiation towards an MSC-like immunophenotype. Stable miPSC-MSC cultures expressed the MSC-associated markers, CD73, CD105, and Sca-1, but lacked expression of the pluripotency marker, SSEA1, and hematopoietic markers, CD34 and CD45. Functionally, miPSC-MSC exhibited the potential for trilineage differentiation into osteoblasts, adipocytes, and chondrocytes and the capacity to suppress the proliferation of mitogen-activated splenocytes. The efficacy of miPSC-MSC was assessed in an acute inflammation model following systemic or local delivery into mice with subcutaneous implants containing heat-inactivated P. gingivalis. Histological analysis revealed less inflammatory cellular infiltrate within the sponges in mice treated with miPSC-MSC cells delivered locally rather than systemically. Assessment of proinflammatory cytokines in mouse spleens found that CXCL1 transcripts and protein were reduced in mice treated with miPSC-MSC. In a periodontitis model, mice subjected to oral inoculation with P. gingivalis revealed less bone tissue destruction and inflammation within the jaws when treated with miPSC-MSC compared to PBS alone. Our results demonstrated that miPSC-MSC derived from iPSC have the capacity to control acute and chronic inflammatory responses associated with the destruction of periodontal tissue. Therefore, miPSC-MSC present a promising novel source of stromal cells which could be used in the treatment of periodontal disease and other inflammatory systemic diseases such as rheumatoid arthritis.

NICE guideline for the management of head injury: an audit demonstrating its impact on a district general hospital, with a cost analysis for England and Wales.

OBJECTIVES: To answer concerns related to implementation of the National Institute for Clinical Excellence (NICE) guideline on the management of head injury by determining the impact on the workload of a district general hospital. Increased computed tomography (CT) was of particular concern (cost, radiation risk, and delivery constraints). METHOD: Retrospective audit of all patients attending the hospital's emergency department with a head injury over a three month period. Any reattendees for the same head injury episode were excluded but the need for CT was recorded. Case notes and electronic records were reviewed to determine whether the CT head or skull radiograph (SXR) was indicated in line with the NICE guideline. The workload was compared with an identical audit performed before the implementation of the NICE guideline. RESULTS: Of 17 472 patients attending the ED in 2004, 472 had a head injury. CT scan was indicated in 36, a significant increase from 2003 (p < 0.001). No SXR was indicated but two were performed, a significant decrease (p < 0.001). The admission rate was unaltered. The positive predictive value of NICE was 17.1% compared with 25% (p = not significant) for the authors' pre-NICE departmental guideline. CONCLUSIONS: This department has seen an increase in CT head requests since the implementation of the NICE guideline. This costs an extra 15,000 pounds sterling per 100 head injuries annually for this department, with an estimated 51.7 million pounds sterling burden for England and Wales. Further evaluation is required as there were only nine brain injuries in this audit population.

Induced Pluripotent Stem Cells: A New Frontier for Stem Cells in Dentistry.

Induced pluripotent stem cells (iPSCs) are the newest member of a growing list of stem cell populations that hold great potential for use in cell-based treatment approaches in the dental field. This review summarizes the dental tissues that have successfully been utilized to generate iPSC lines, as well as the potential uses of iPSCs for tissue regeneration in different dental applications. While iPSCs display great promise in a number of dental applications, there are safety concerns with these cells that need to be addressed before they can be used in clinical settings. This review outlines some of the apprehensions to the use of iPSCs clinically, and it details approaches that are being employed to ensure the safety and efficacy of these cells. One of the major approaches being investigated is the differentiation of iPSCs prior to use in patients. iPSCs have successfully been differentiated into a wide range of cells and tissue types. This review focuses on 2 differentiation approaches-the differentiation of iPSCs into mesenchymal stem cells and the differentiation of iPSCs into osteoprogenitor cells. Both these resulting populations of cells are particularly relevant to the dental field.

Loss of endothelial barrier function requires neutrophil adhesion.

BACKGROUND: The inflammatory response is characterized by cytokine-induced up-regulation of endothelial adhesion molecules followed by polymorphonuclear neutrophil (PMN) adhesion and breakdown of tight junctions between cells. The purpose of this investigation was to determine whether PMN adhesion is an essential element in the alteration of endothelial permeability or whether cytokines alone can produce this change. METHODS: Human umbilical vein endothelial cells (HUVECs) were exposed to formylated met-leu-phe-activated PMNs. In a second series of experiments, PMNs were contained in a microporous membrane that allowed passage of secreted cytokines but not cells. Permeability was quantified by using transendothelial electrical resistance (TEER, ohm.cm2,) whereas expressions of two cell adhesion molecules (endothelial leukocyte adhesion molecule-1 [ELAM-1] and intercellular adhesion molecule-1 [ICAM-1]) were measured by flow cytometry (% shift). Cytokine production was monitored with enzyme-linked immunosorbant assays (picograms per milliliter). RESULTS: Stimulated PMNs secreted comparable amounts of cytokines whether allowed access to HUVECs or trapped in a microporous membrane (interleukin-1 alpha, 5.88 +/- 2.38 versus 3.65 +/- 1.84 pg/ml; tumor necrosis factor-alpha, 10.27 +/- 3.21 versus 6.61 +/- 1.82 pg/ml). Up-regulation of ELAM-1 and ICAM-1 was observed whether PMNs were free or restricted (52.97% +/- 2.14% versus 75.32% +/- 4.19% and 71.66% +/- 7.37% versus 73.66% +/- 4.32%, respectively). TEER was unchanged in controls and when PMNs were membrane restricted. In contrast, TEER decreased precipitously (51% +/- 5.9% of control, p < 0.05) if PMNs were allowed access to HUVECs. CONCLUSIONS: Cytokine secretion by PMNs is independent of endothelial contact and is sufficient to upregulate adhesion molecules. However, PMN adhesion is essential for the loss of endothelial barrier function, which leads to diapedesis of activated PMNs and eventual tissue injury.

Prolonged hypoxia alters endothelial barrier function.

BACKGROUND: It is well recognized that hypoxia/reoxygenation and exposure to inflammatory mediators such as cytokines and neutrophils alter the barrier function of the vascular endothelium. The experiments we conducted tested whether hypoxia alone could produce changes in permeability and whether a prolonged period of hypoxia alters the surface expression of cell adhesion molecules. METHODS: Endothelial cells were cultured from human umbilical vein endothelial cells (HUVECs). Hypoxia was created by isolating the cells in a chamber through which 1% 02, 5% CO2, and 94% N2 were insufflated (30 min at 1/min). Oxygen tension was measured through oxygen-quenching phosphorescence. Hypoxia was maintained for 24 hours. Changes in endothelial permeability were measured by transendothelial electrical resistance (TEER). Endothelial leukocyte adhesion molecule 1 (ELAM-1) and intercellular adhesion molecule 1 (ICAM-1) expression were assessed by flow cytometry (mean +/ standard error of the mean [SEM]. RESULTS: Exposure of endothelial cells to hypoxia resulted in increased permeability between 6 and 24 hours, with the greatest decrease in TEER at 18 hours (63% +/ 3%; P < .05). Prolonged hypoxia produced no change in the surface expression of ELAM-1 or ICAM-1. CONCLUSIONS: Hypoxia alone produced a significant reversible alteration in endothelial permeability. However, this change was observed only under severe hypoxic conditions (eg, below 20 mm Hg); higher oxygen tensions (25 and 35 mm Hg) had no significant effect. Unlike observations made after cytokine exposure, hypoxic breakdown of endothelial barrier function was unassociated with up-regulation of either ELAM-1 or ICAM-1.

Cytokine-induced increases in endothelial permeability occur after adhesion molecule expression.

BACKGROUND: Transmigration of neutrophils (PMNs) through endothelial cell tight junctions is a critical stage in the tissue injury of ischemia-reperfusion (I/R). Although cytokines are released in I/R, it is unclear whether cytokines directly increase permeability or this phenomenon requires both expression of cell adhesion molecules and PMN adhesion-activation. METHODS: We exposed confluent monolayers of human umbilical vein endothelial cells to physiologic concentrations of interleukin-1 (10 pg/ml) and tumor necrosis factor-alpha (10 pg/ml) in the absence of PMNs. Tight junction permeability was quantified with both transendothelial electrical resistance and albumin flux, whereas expression of endothelial-leukocyte adhesion molecule-1 was measured by flow cytometry (t test p < 0.05). RESULTS: Stimulation with tumor necrosis factor-alpha or interleukin-1 produced maximal transendothelial electrical resistance decreases at 12 hours with return to baseline at 24 hours. Increases in albumin flux began at 6 hours, with maximum effects at 24 hours. These changes occurred soon after maximal expression of endothelial-leukocyte adhesion molecule-1 at 4 hours. CONCLUSIONS: Cytokines induced increases in both cell adhesion molecule expression and endothelial permeability. This sequence of events is consistent with direct cytokine effects on cytoarchitecture, because it occurred without the adhesion-activation of PMNs.

Serum proteins facilitate neutrophil induction of endothelial leukocyte adhesion molecule 1.

BACKGROUND: Although the individual actions of neutrophils and serum proteins such as complement in acute inflammation are well characterized, less is known about their effects in combination. We investigated the combined effects of neutrophil contact and active serum proteins on the expression of endothelial leukocyte adhesion molecule 1 (ELAM-1). METHODS: Confluent monolayers of human umbilical vein endothelial cells were incubated with neutrophils in the presence and absence of fresh human serum. Flow cytometry was used to assess expression of endothelial intercellular adhesion molecule 1 (ICAM-1) and ELAM-1. In addition, neutrophils were retained in a semipermeable insert, which allowed their secretions to contact the endothelium but restricted neutrophil-endothelial contact. RESULTS: ELAM-1 expression was significantly increased on the cells coincubated with neutrophils and fresh human serum (25.8%; p < 0.001). There was no significant change in ELAM-1 expression on endothelial cells incubated with fresh human serum alone (3.9%; p > 0.01) or in those incubated with neutrophils and heat-inactivated serum (9.3%; p > 0.01). In the absence of neutrophil contact, ELAM-1 expression was increased only in the presence of fresh human serum (9.6%; p < 0.05). CONCLUSIONS: These findings suggest that serum proteins may potentiate the volume or potency of neutrophil-derived diffusable mediators of ELAM-1 expression. These effects are eliminated with the heat inactivation of serum proteins, implicating a heat sensitive mediator such as the complement cascade.

A randomized controlled trial of phytoestrogen supplementation, growth and bone turnover in adolescent males.

OBJECTIVE: To assess the effect of phytoestrogens on bone turnover and growth in adolescent boys. DESIGN: Randomized double-blind placebo-controlled trial. SETTING: Single school in northwest Tasmania. PARTICIPANTS: Adolescent boys (treatment n=69, placebo n=59, mean age 16.8 y). INTERVENTIONS: Six weeks of isoflavone supplementation (Novasoy, 50 mg daily of isoflavone equivalents). Bone turnover markers (bone specific alkaline phosphatase (BAP) and pyridinoline creatinine ratio (PYR)) were measured at baseline and follow-up. RESULTS: Despite marked increases in urinary genistein and daidzein in the treatment arm (both P<0.001), there were no significant differences in BAP, PYR or short-term height or weight change. This applied to both intention-to-treat and per protocol analysis. Neither was there a significant correlation between urinary genistein and daidzein levels and BAP or PYR. CONCLUSIONS: Phytoestrogen supplementation to the level of usual Japanese dietary intake has no measurable effect on bone turnover in adolescent boys. Longer-term studies of bone density may be desirable but it is unlikely that there will be a large effect in either girls or boys given the lower endogenous oestrogen levels in boys.

The effects of area health education centers on primary care physician-to-population ratios from 1975 to 1985.

The purpose of this study was to explore how the primary care (PC) physician-to-population ratio changed from 1975 to 1985 in counties that were served by an Area Health Education Center (AHEC) in contrast to those counties that were not. The investigation attempted to determine whether any observed changes in this ratio were dependent upon either degree of urbanization or contiguity to a Standard Metropolitan Statistical Area (SMSA). The data source for this study was the Area Resource File. Results indicated that: (a) irrespective of AHEC status, increased degree of urbanization across counties was associated with relatively more PC physicians in both 1975 and 1985; (b) PC physician-to-population ratios increased from 1975 to 1985 for all American Medical Association (AMA) county code categories, regardless of AHEC versus non-AHEC designation; (c) AHEC counties demonstrated greater (or equivalent) absolute improvement for all AMA county code categories except for several categories which represented more urbanized counties; (d) for the least urbanized counties in the AMA code, the percentage improvement in PC physician-to-population ratios for AHEC counties ranged from 3 to 5 percent higher than corresponding percentage improvement in ratios for non-AHEC counties; and (e) AHEC counties showed greater absolute and percentage improvement in PC physician-to-population ratios than did non-AHEC counties for counties not contiguous to SMSAs.

Physician distribution in a predominantly rural state: predictors and trends.

The present study examined changes in physician distribution across time in a predominantly rural state to determine the generalizability of national studies of physician distribution. Contrary to recent national findings, decreases in the population/physician ratio occurred only for counties having populations greater than 25,000. When county population was controlled for by entering it hierarchically as the first predictor in the regression analysis, number of applicants to medical school from a county was the only consistently significant predictor of physician distribution.

Mesenchymal stem cells from iPS cells facilitate periodontal regeneration.

Mesenchymal stem cells (MSC) have been considered as a potential therapy for the treatment of periodontal defects arising from periodontitis. However, issues surrounding their accessibility and proliferation in culture significantly limit their ability to be used as a mainstream treatment approach. It is therefore important that alternative, easily accessible, and safe populations of stem cells be identified. Controlled induction of induced pluripotent stem cells (iPSC) into MSC-like cells is emerging as an attractive source for obtaining large populations of stem cells for regenerative medicine. We have successfully induced iPSC to differentiate into MSC-like cells. The MSC-like cells generated satisfied the International Society of Cellular Therapy's minimal criteria for defining multipotent MSC, since they had plastic adherent properties, expressed key MSC-associated markers, and had the capacity to undergo tri-lineage differentiation. Importantly, the resulting iPSC-MSC-like cells also had the capacity, when implanted into periodontal defects, to significantly increase the amount of regeneration and newly formed mineralized tissue present. Our results demonstrate, for the first time, that MSC derived from iPSC have the capacity to aid periodontal regeneration and are a promising source of readily accessible stem cells for use in the clinical treatment of periodontitis.