Christine M. Herring

VEGF is critical for stem cell-mediated cardioprotection and a crucial paracrine factor for defining the age threshold in adult and neonatal stem cell function

Bone marrow mesenchymal stem cells (MSCs) may be a novel treatment modality for organ ischemia, possibly through the release of beneficial paracrine factors. However, an age threshold likely exists as to when MSCs gain their beneficial protective properties. We hypothesized that 1) VEGF would be a crucial stem cell paracrine mediator in providing postischemic myocardial protection and 2) small-interfering (si)RNA ablation of VEGF in adult MSCs (aMSCs) would equalize the differences observed between aMSC- and neonatal stem cell (nMSC)-mediated cardioprotection. Female adult Sprague-Dawley rat hearts were subjected to ischemia-reperfusion injury via Langendorff-isolated heart preparation (15 min equilibration, 25 min ischemia, and 60 min reperfusion). MSCs were harvested from adult and 2.5-wk-old neonatal mice and cultured under normal conditions. VEGF was knocked down in both cell lines by VEGF siRNA. Immediately before ischemia, one million aMSCs or nMSCs with or without VEGF knockdown were infused into the coronary circulation. The cardiac functional parameters were recorded. VEGF in cell supernatants was measured via ELISA. aMSCs produced significantly more VEGF than nMSCs and were noted to increase postischemic myocardial recovery compared with nMSCs. The knockdown of VEGF significantly decreased VEGF production in both cell lines, and the pretreatment of these cells impaired stem cell-mediated myocardial function. The knockdown of VEGF in adult stem cells equalized the myocardial functional differences observed between adult and neonatal stem cells. Therefore, VEGF is a critical paracrine mediator in facilitating postischemic myocardial recovery and likely plays a role in mediating the observed age threshold during stem cell therapy.

Sex dimorphisms in activated mesenchymal stem cell function

ABSTRACT The plasticity of bone marrow-derived stem cells (BMSCs) has resulted in positive remodeling and the regeneration of viable tissues. However, BMSC release of growth factors, which limit apoptosis and inflammation, may play an important role in conferring organ protection. Recent studies also indicate that those patients with higher circulating BMSC counts may be more resistant to septic and traumatic insults. There are clear sex differences in response to such insults. Within the population of BMSC, mesenchymal stem cells (MSCs) may have clinical advantages. Therefore, we hypothesize that sex differences in the MSC paracrine response to acute injury exist. Mesenchymal stem cells were obtained from male and female mice. One million MSCs per well (triplicate wells per group) were stressed by hypoxia and increasing doses of endotoxin (lipopolysaccharide [LPS]) and hydrogen peroxide. Mesenchymal stem cell activation was determined by measuring vascular endothelial growth factor (VEGF) and tumor necrosis factor &agr; production by enzyme-linked immunosorbent assay. Differences were considered significant if P < 0.05. Results Lipopolysaccharide resulted in significant activation of both male and female MSCs. However, LPS provoked significantly more VEGF production in female MSCs versus male MSCs at all LPS doses. Hypoxia of 1 h and hydrogen pyroxide exposure also caused significantly more VEGF production in female MSCs versus male MSCs. Female MSCs expressed significantly less tumor necrosis factor &agr; than male MSCs after acute LPS and hypoxia. Conclusion This study constitutes the first demonstration that sex differences exist in activated MSC function. Sex differences in progenitor cell function may have important implications in understanding the observed sex differences in the hosts response to injury.

The struggle for iron: gastrointestinal microbes modulate the host immune response during infection

The gastrointestinal track is one source of potential bacterial entry into the host, and the local immune system at the mucosal border is paramount in establishing host immune tolerance and the immune response to invading organisms. Macrophages use iron for production of hydroxy‐radical and superoxide reactions, which are necessary for microbial killing. Presumably, as a survival strategy, bacteria, which also require iron for survival, have adapted the ability to sequester iron from the host, thereby limiting the availability to macrophages. As current modes of antimicrobial therapy are evolving, examination of nontraditional therapies is emerging. One such potential therapy involves altering the bacterial micronutrient iron concentration. Necrotizing enterocolitis is a clinical condition where such a strategy makes intuitive sense. This review will describe the immune response to gastrointestinal infection, the mechanisms that the gastrointestinal system uses to absorb intraluminal iron, and the critical role iron plays in the infectious process.

Striatal D2/D3 receptor availability is inversely correlated with cannabis consumption in chronic marijuana users

BACKGROUND Although the incidence of cannabis abuse/dependence in Americans is rising, the neurobiology of cannabis addiction is not well understood. Imaging studies have demonstrated deficits in striatal D(2)/D(3) receptor availability in several substance-dependent populations. However, this has not been studied in currently using chronic cannabis users. OBJECTIVE The purpose of this study was to compare striatal D(2)/D(3) receptor availability between currently using chronic cannabis users and healthy controls. METHODS Eighteen right-handed males age 18-34 were studied. Ten subjects were chronic cannabis users; eight were demographically matched controls. Subjects underwent a [(11)C]raclopride (RAC) PET scan. Striatal RAC binding potential (BP(ND)) was calculated on a voxel-wise basis. Prior to scanning, urine samples were obtained from cannabis users for quantification of urine Δ-9-tetrahydrocannabinol (THC) and THC metabolites (11-nor-Δ-9-THC-9-carboxylic acid; THC-COOH and 11-hydroxy-THC;OH-THC). RESULTS There were no differences in D(2)/D(3) receptor availability between cannabis users and controls. Voxel-wise analyses revealed that RAC BP(ND) values were negatively associated with both urine levels of cannabis metabolites and self-report of recent cannabis consumption. CONCLUSIONS In this sample, current cannabis use was not associated with deficits in striatal D(2)/D(3) receptor availability. There was an inverse relationship between chronic cannabis use and striatal RAC BP(ND). Additional studies are needed to identify the neurochemical consequences of chronic cannabis use on the dopamine system.

Test–retest variability of [11C]raclopride-binding potential in nontreatment-seeking alcoholics

Knowledge of the reproducibility of striatal [11C]raclopride (RAC) binding is important for studies that use RAC PET paradigms to estimate changes in striatal dopamine (DA) during pharmacological and cognitive challenges. To our knowledge, no baseline test–retest data exist for nontreatment‐seeking alcoholics (NTS). We determined the test–retest reproducibility of baseline RAC binding potential (BPND) in 12 male NTS subjects. Subjects were scanned twice with single‐bolus RAC PET on separate days. Striatal RAC BP (BPND) for left and right dorsal caudate, dorsal putamen, and ventral striatum was estimated using the Multilinear Reference Tissue Method (MRTM) and Logan Graphical Analysis (LGA) with a reference region. Test–retest variability (TRV), % change in BPND between scan days, and the intraclass correlation coefficient (ICC) were used as metrics of reproducibility. For MRTM, TRV for striatal RAC binding in NTS subjects was ±6.5% and ±7.1% for LGA. Average striatal ICCs were 0.94 for both methods (P < 0.0001). Striatal BPND values were similar to those reported previously for detoxified alcoholics. The results demonstrate that baseline striatal RAC binding is highly reproducible in NTS subjects, with a low variance similar to that reported for healthy control subjects. Synapse, 2011.

The Effects of Service-Delivery Model and Purchase Price on Hearing-Aid Outcomes in Older Adults: A Randomized Double-Blind Placebo-Controlled Clinical Trial

Objectives The objectives of this study were to determine efficacy of hearing aids in older adults using audiology best practices, to evaluate the efficacy of an alternative over-the-counter (OTC) intervention, and to examine the influence of purchase price on outcomes for both service-delivery models. Design The design of this study was a single-site, prospective, double-blind placebo-controlled randomized trial with three parallel branches: (a) audiology best practices (AB), (b) consumer decides OTC model (CD), and (c) placebo devices (P). Outcome measures were obtained after a typical 6-week trial period with follow-up 4-week AB-based trial for those initially assigned to CD and P groups. Setting Older adults from the general community were recruited via newspaper and community flyers to participate at a university research clinic. Participants Participants were adults, ages 55–79 years, with mild-to-moderate hearing loss. There were 188 eligible participants: 163 enrolled as a volunteer sample, and 154 completed the intervention. Intervention(s) All participants received the same high-end digital mini-behind-the-ear hearing aids fitted bilaterally. AB and P groups received best-practice services from audiologists; differing mainly in use of appropriate (AB) or placebo (P) hearing aid settings. CD participants self-selected their own pre-programmed hearing aids via an OTC model. Primary and Secondary Outcome Measures Primary outcome measure was a 66-item self-report, Profile of Hearing Aid Benefit (Cox & Gilmore, 1990). Secondary outcome measure was the Connected Speech Test (Cox, Alexander, & Gilmore, 1987) benefit. Additional measures of hearing-aid benefit, satisfaction, and usage were also obtained. Results Per-protocol analyses were performed. AB service-delivery model was found to be efficacious for most of the outcome measures, with moderate or large effect sizes (Cohens d). CD service-delivery model was efficacious, with similar effect sizes. However, CD group had a significantly (p < .05) lower satisfaction and percentage (CD: 55%; AB: 81%; P: 36%) likely to purchase hearing aids after the trial. Conclusions Hearing aids are efficacious in older adults for both AB and CD service-delivery models. CD model of OTC service delivery yielded only slightly poorer outcomes than the AB model. Efficacious OTC models may increase accessibility and affordability of hearing aids for millions of older adults. Purchase price had no effect on outcomes, but a high percentage of those who rejected hearing aids paid the typical price (85%). Trial Registration Clinicaltrials.gov: NCT01788432; https://clinicaltrials.gov/ct2/show/NCT01788423 Supplemental Materials https://doi.org/10.23641/asha.5382499

Deleterious effects of endogenous and exogenous testosterone on mesenchymal stem cell VEGF production.

Modulating the paracrine effects of bone marrow mesenchymal stem cells (BMSCs) may be important for the treatment of ischemic myocardial tissue. In this regard, endogenous estrogen may enhance BMSC vascular endothelial growth factor (VEGF) production. However, little information exists regarding the effect of testosterone on stem cell function. We hypothesized that 1) endogenous or exogenous estrogen will enhance stem cell production of VEGF and 2) endogenous or exogenous testosterone will inhibit BMSC VEGF production. BMSCs were collected from adult male, female, castrated male, and ovariectomized female rats. One hundred thousand cells were incubated with testosterone (1, 10, or 100 nM) or estrogen (0.15, 1.5, or 15 nM) for 48 h. Cell supernatants were collected, and VEGF was measured by ELISA. BMSCs harvested from castrated males, normal females, and ovariectomized females produced more VEGF compared with normal males. Castration was associated with the highest level (1,018 +/- 98.26 pg/ml) of VEGF production by BMSCs, which was significantly more than that produced by BMSCs harvested from normal male and normal female animals. Exogenous testosterone significantly reduced VEGF production in BMSCs harvested from ovariectomized females in a dose-dependent manner. Exogenous estrogen did not alter BMSC VEGF production. These findings suggest that testosterone may work on BMSCs to decrease protective growth factor production and that effective removal of testosterones deleterious effects via castration may prove to be beneficial in terms of protective factor production. By manipulating the mechanisms that BMSCs use to produce growth factors, we may be able to engineer stem cells to produce maximum growth factors during therapeutic use.

Monetary discounting and ventral striatal dopamine receptor availability in nontreatment-seeking alcoholics and social drinkers

RationaleDopamine (DA) in the ventral striatum (VST) has long been implicated in addiction pathologies, yet its role in temporal decision-making is not well-understood.ObjectivesTo determine if VST DA D2 receptor availability corresponds with greater impulsive choice in both nontreatment-seeking alcoholics (NTS) and social drinkers (SD).MethodsNTS subjects (n = 10) and SD (n = 13) received PET scans at baseline with the D2/D3 radioligand [11C]raclopride (RAC). Outside the scanner, subjects performed a delay discounting procedure with monetary rewards. RAC binding potential (BPND) was estimated voxelwise, and correlations were performed to test for relationships between VST BPND and delay discounting performance. Self-reported impulsivity was also tested for correlations with BPND.ResultsAcross all subjects, greater impulsive choice for

Reliability of striatal [11C]raclopride binding in smokers wearing transdermal nicotine patches

20 correlated with lower BPND in the right VST. NTS showed greater impulsive choice than SD and were more impulsive by self-report. Across all subjects, the capacity of larger rewards to reduce impulsive choice (the magnitude effect) correlated negatively (p = 0.028) with problematic alcohol use (AUDIT) scores. Self-reported impulsivity did not correlate with BPND in VST.ConclusionsPreference for immediate reinforcement may reflect greater endogenous striatal DA or lower D2 number, or both. Alcoholic status did not mediate significant effects on VST BPND, suggesting minimal effects from alcohol exposure. The apparent lack of BPND correlation with self-reported impulsivity highlights the need for objective behavioral assays in the study of the neurochemical substrates of behavior. Finally, our results suggest that the magnitude effect may be more sensitive to alcohol-induced problems than single discounting measures.

The Effects of Endogenous Sex Hormones and Acute Hypoxia on Vasoconstriction in Isolated Rat Pulmonary Artery Rings

PurposeIn studies where [11C]raclopride (RAC) positron emission tomography (PET) is used to assess changes in striatal dopamine, it is important to control for cognitive states, such as drug craving, that could alter dopamine levels. In cigarette smokers, transdermal nicotine patches (TNP) can control nicotine craving, but the effects of nicotine patches on RAC binding are unknown. Thus, we sought to determine the test-retest reliability of RAC binding in the presence of nicotine patches.MethodsEleven male smokers were scanned twice with RAC on separate days while wearing TNP.ResultsAcross the striatum, test-retest variability was 7.63 ± 5.88; percent change in binding potential was 1.11 ± 9.83; and the intraclass correlation coefficient was 0.91 (p < 0.0001).ConclusionBaseline RAC binding is highly reproducible in smokers wearing nicotine patches. This suggests that TNP are an acceptable method for controlling cigarette craving during studies that utilize RAC to examine changes in dopamine.