Praveen K. Gajendrareddy

Differential Expression of HIF-1α in Skin and Mucosal Wounds

Despite accelerated epithelial closure, oral mucosal wounds exhibit lower levels of VEGF and a more refined angiogenic response than do skin wounds. The specific differences in angiogenesis suggest that skin and oral mucosal wounds may experience dissimilar levels of hypoxia and HIF-1α. Using a model of comparable wounds on murine dorsal skin and tongue, we determined levels of hypoxia and HIF-1α. Skin wounds were found to be significantly more hypoxic and had higher levels of HIF-1α than mucosal wounds. Furthermore, under stressed conditions, skin wounds, but not mucosal wounds, exhibited a further elevation of HIF-1α beyond that of non-stressed levels. To determine if manipulation of oxygen levels might equalize the repair response of each tissue, we exposed mice to hyperbaric oxygen treatment (HBOT) following wounding. HBOT did not significantly change HIF-1α or VEGF expression in either skin or mucosal wounds, nor did it alter wound bed vascularity. These studies suggest that skin wounds have higher levels of hypoxia than do mucosal wounds, along with a differential expression of HIF-1α. Interestingly, modulation of oxygen by HBOT does not ameliorate this difference. These results suggest that differential responses to hypoxia may underlie the distinctive wound-healing phenotypes seen in skin and oral mucosa.

MMP-8 overexpression and persistence of neutrophils relate to stress-impaired healing and poor collagen architecture in mice

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase (TIMPs) are critical for tissue remodeling during wound repair. Psychological stress has been found to impair wound healing in humans and animals. The objective of this study was to assess MMP and TIMP gene expression during stress-impaired healing. Female SKH-1 mice (n=299) were divided into control and stress groups (13h restraint/day for 3days prior to and 5days post-wounding). Two 3.5mm cutaneous full-thickness wounds were placed on the dorsum of each mouse and wound measurements were performed daily. RT-PCR for gene expression of MMP-2, MMP-8, MMP-9, TIMP-1 and TIMP-2 was performed at days 1, 3 and 5. Immunohistochemical analyses of the healed wounds were performed at days 15 and 28. As expected, wounds healed more slowly in restraint-stressed mice compared to controls. Stressed mice exhibited MMP-8 overexpression and lower TIMP-1 levels during healing, and poorer collagen organization once healed. MMP-8 overexpression may have stemmed from a higher level of neutrophils, observed in wound tissue on days 3 and 5. These findings implicate higher neutrophil numbers, MMP-8 overexpression, and TIMP-1 under-expression, as mechanisms that may compromise wound outcomes such as scarring under conditions of stress.

Biomimetically Enhanced Demineralized Bone Matrix for Bone Regenerative Applications

Demineralized bone matrix (DBM) is one of the most widely used bone graft materials in dentistry. However, the ability of DBM to reliably and predictably induce bone regeneration has always been a cause for concern. The quality of DBM varies greatly depending on several donor dependent factors and also manufacturing techniques. In order to standardize the quality and to enable reliable and predictable bone regeneration, we have generated a biomimetically-enhanced version of DBM (BE-DBM) using clinical grade commercial DBM as a control. We have generated the BE-DBM by incorporating a cell-derived pro-osteogenic extracellular matrix (ECM) within clinical grade DBM. In the present study, we have characterized the BE-DBM and evaluated its ability to induce osteogenic differentiation of human marrow derived stromal cells (HMSCs) with respect to clinical grade commercial DBM. Our results indicate that the BE-DBM contains significantly more pro-osteogenic factors than DBM and enhances HMSC differentiation and mineralized matrix formation in vitro and in vivo. Based on our results, we envision that the BE-DBM has the potential to replace DBM as the bone graft material of choice.

Wound Healing in the Elderly

Being elderly is a risk factor for delayed wound healing. In aged skin, epidermal turnover is decreased by about 50%. This is accompanied by reductions in vascularization, granulation tissue, collagen, elastin, mast cells and fibroblasts. Age-related changes occur which impact all phases of healing. In general, the elderly have increased rates of infection and wound dehiscence, decreases in wound strength, and slower healing times. This is primarily caused by reductions in re-epithelialization, angiogenesis, macrophage infiltration, and collagen deposition. Paradoxically, wounds heal with less scarring in the aged. It is important to note that healing is delayed but not impaired in the elderly, and the end result of healing, albeit slower, is similar to that of young adults. However, concomitant risk factors for delays or impairments in healing (e.g., disease, medications, malnutrition, immobility, obesity, stress) are more common in the elderly. Each of these risk factors should be tested for, treated, and monitored accordingly prior to surgery to ensure maximal healing. It is not being elderly per se, but being elderly and presenting additional risk factors, that predisposes an individual to impaired healing and poor surgical outcomes.

A Risk of Bias Assessment of Randomized Controlled Trials (RCTs) on Periodontal Regeneration Published in 2013

OBJECTIVE The objective of this assessment is to evaluate the degree of risk of bias in randomized controlled trials published in 2013 and focusing on periodontal regeneration. METHODS Three reviewers searched and selected the trials based on pre-defined inclusion criteria. Predictor variables [number of authors, primary objective of the study, biomaterial employed, follow-up time periods, split mouth study (yes/no), journal, year of publication, country, scale (single/multi-center) and nature of funding] were extracted and risk of bias assessment using Cochrane risk of bias tool were performed independently by the three reviewers. RESULTS Seventeen RCTs were included in this assessment. The risk of bias in RCTs published in 2013 with a focus in periodontal regeneration varied significantly with only in less than 30% of the included trials, the overall risk of bias was found to be low, while 41% of trials were designated to have a higher degree of bias. Specifically, when looking at the domains assessed, 70% of the included trials reported an accepted method of sequence generation, blinding (whenever possible), completeness of outcome data or avoided selective outcome reporting. Meanwhile, only 47% of the included trials reported some form of allocation concealment. CONCLUSION In this assessment, of the included 17 trials, slightly more than 40% of them had a high risk of bias, underscoring the importance of careful appraisal of trials before implementing the study interventions in clinical practice and the need for more detailed analyses.

Vitamin D deficiency and periodontal clinical attachment loss in HIV-seropositive women: A secondary analysis conducted in the Women's Interagency HIV Study (WIHS)

OBJECTIVE The aim of this study was to test a hypothesized positive association between low vitamin D (VitD) serum levels and the severity of periodontal disease in women with HIV infection. STUDY DESIGN This was a cross-sectional secondary analysis of data from an oral substudy conducted within the Chicago site of the Womens Interagency HIV Study. Serum VitD levels and clinical attachment loss (CAL) measurements were available for 74 women with HIV infection. VitD levels were treated as both continuous and categorical variables in bivariate and multivariate analyses. Mean clinical attachment loss (mCAL) was determined for each subject by obtaining the averages of measurements taken at 4 sites in each measured tooth. RESULTS Average age of study participants (n = 74) was 39.6 years (standard deviation 7.2), and the majority were African Americans (70.3%) with VitD deficiency (58.1%). VitD deficiency was positively associated with higher mCAL (P = .012). After adjustment for race, age, smoking, and HIV viral load, an association was found between VitD deficiency and mCAL (Beta 0.438; P = .036). CONCLUSIONS We identified a previously unreported association between VitD deficiency and mCAL in women with HIV infection. Larger and more inclusive, multisite, longitudinal studies are warranted to investigate whether these findings can be generalized to all individuals with HIV infection in the current treatment era and to determine causality.

Increased oxygen exposure alters collagen expression and tissue architecture during ligature‐induced periodontitis

BACKGROUND AND OBJECTIVE The aim of this study was to evaluate the effects of increased oxygen availability on gene expression and on collagen deposition/maturation in the periodontium following disease. MATERIAL AND METHODS Male Wistar rats had ligatures placed around their molars to induce periodontal disease, and a subset of animals underwent hyperbaric oxygen (HBO) treatment for 2 h twice per day. At 15 and 28 d, tissue gene expression of COL1A1, transforming growth factor-β1 and alkaline phosphatase was determined; other histological samples were stained with Picrosirius red to evaluate levels of collagen deposition, maturation and thickness. RESULTS In animals that underwent HBO treatment, type I collagen expression was higher and collagen deposition, maturation and thickness were more robust. Reduced mRNA levels of transforming growth factor-beta1 and alkaline phosphatase in HBO-treated rats on day 28 suggested that a quicker resolution in both soft tissue and bone remodeling occurred following oxygen treatment. No differences in inflammation were observed between groups. CONCLUSIONS The extracellular matrix regenerated more quickly in the HBO-treated group as evidenced by higher collagen expression, deposition and maturation.

68. Naked mole-rat: A model for investigating neuropeptides and healing

was mirrored by prominent c-Fos expression in arousal-supporting orexin and histamine neurons of saline-treated rats, whereas c-Fos expression in these populations was greatly diminished in the LPStreated rats. Arcuate neurons expressing cocaine-amphetaminereated transcript (CART) also expressed prominent c-Fos in salinetreated rats, probably related to ingestion of food. Paradoxally, LPS treatment completely suppressed activity of these CART neurons in the arcuate nucleus, which are implicated in satiety-induced suppression of feeding (serving an anorexigenic role). These findings support our notion that arousal-supporting systems, including the orexin and histaminergic components, which project to large parts of the brain, are functionally disengaged during sickness. This lack of functional activation, critical for goal-directed behavior, may underlie the characteristic lack of behavioral arousal during illness. This study was supported by NIH Grant MH068834.