Epigenetic DNA Methylation Linked to Social Dominance.

Social status hierarchies are ubiquitous in vertebrate social systems, including humans. It is well known that social rank can influence quality of life dramatically among members of social groups. For example, high-ranking individuals have greater access to resources, including food and mating prerogatives that, in turn, have a positive impact on their reproductive success and health. In contrast low ranking individuals typically have limited reproductive success and may experience lasting social and physiological costs. Ultimately, social rank and behavior are regulated by changes in gene expression. However, little is known about mechanisms that transduce social cues into transcriptional changes. Since social behavior is a dynamic process, we hypothesized that a molecular mechanism such as DNA methylation might play a role these changes. To test this hypothesis, we used an African cichlid fish, Astatotilapia burtoni, in which social rank dictates reproductive access. We show that manipulating global DNA methylation state strongly biases the outcomes of social encounters. Injecting DNA methylating and de-methylating agents in low status animals competing for status, we found that animals with chemically increased methylation states were statistically highly likely to ascend in rank. In contrast, those with inhibited methylation processes and thus lower methylation levels were statistically highly unlikely to ascend in rank. This suggests that among its many roles, DNA methylation may be linked to social status and more generally to social behavior

Average number of territorial acts with non-territorial behavioral acts subtracted (per 5 min) of dominant (upper line in each graph) and non-dominant animals (lower line in each graph).

<p>(A) Paired L-methionine (blue line) and vehicle-injected (gray dashed line) animals (2N = 24). There is a significant difference between methionine-injected and control-injected animals F(1,110) = 59.28, p = 6.37 x 10⁻¹². There was no significant difference in behavior between individual observation days (F(4,110) = 2.32, p = 0.062) or significant interaction between injection treatment and individual days (F(4,110) = 1.52, p = 0.20). (B) Paired zebularine (red line) and vehicle injected (gray dashed line) animals (2N = 22). There was a significant difference between zebularine-injected and control-injected animals F(1,100) = 29.60, p = 3.79 x 10⁻⁷. There was no significant difference in behavior between individual days (F(4,100) = 1.76, p = 0.14), or significant interaction between injection treatment and individual days (F(4,100) = 0.70, p = 0.59).</p

Differential methylation at CpG sites within functional genomic regions of <i>GnRH1</i> in the pre-optic area (POA) in zebularine-injected, L-methionine-injected and control-injected dominant (D) and non-dominant (ND) males 5 days after initial injection.

<p><b>A</b>. Methylation was assayed in two locations on the <i>GnRH1</i> gene; in the promoter region within the binding site of <i>egr1</i> (3 CpG sites indicated by single vertical bars within the green rectangle) and in the coding region in the sequence of the signal peptide (2 CpG sites indicated by single bars within the yellow rectangle). <b>B</b>. Average methylation levels in <i>GnRH1</i> genomic regions of zebularine-injected ND males that show significantly higher average methylation levels than control-injected ND males in the <i>egr-1</i> binding site located in promoter region of <i>GnRH1</i>. (*q-value < 0.05; n = 3–4 per group). <b>C</b>. Average methylation levels in <i>GnRH1</i> genomic regions of methionine-injected ND males are not significantly different from those of control injected animals (q-value > 0.05 for all groups; n = 3–8 per group). Statistical significance for each of these regions was calculated by determining combined Fisher’s p values and then calculating q values estimating the multiple-testing-corrected false discovery rate (see Methods in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0144750#pone.0144750.s001" target="_blank">S1 File</a> for complete description). Error bars represent s.e.m.</p

Epigenetic DNA Methylation Linked to Social Dominance - Fig 1

<p>(A) Animals that had never been socially dominant were divided into three groups of size matched pairs. (B) In control animals, both members of the pair received vehicle injections (N = 10 pairs), in experimental animals, in one group (left) one member of the group received L-methionine (N = 12) and the other received vehicle control (N = 12), while in the other group (right), one member of the pair received zebularine, (N = 11) and the other received vehicle control (N = 11). (C) Animals injected with L-methionine were significantly more likely to become socially dominant, while those injected with zebularine were significantly more likely to remain non-dominant.</p

Magnetic Resonance Imaging of Stem Cell Apoptosis in Arthritic Joints with a Caspase Activatable Contrast Agent

About 43 million individuals in the U.S. encounter cartilage injuries due to trauma or osteoarthritis, leading to joint pain and functional disability. Matrix-associated stem cell implants (MASI) represent a promising approach for repair of cartilage defects. However, limited survival of MASI creates a significant bottleneck for successful cartilage regeneration outcomes and functional reconstitution. We report an approach for noninvasive detection of stem cell apoptosis with magnetic resonance imaging (MRI), based on a caspase-3-sensitive nanoaggregation MRI probe (C-SNAM). C-SNAM self-assembles into nanoparticles after hydrolysis by caspase-3, leading to 90% amplification of ¹H MR signal and prolonged <i>in vivo</i> retention. Following intra-articular injection, C-SNAM causes significant MR signal enhancement in apoptotic MASI compared to viable MASI. Our results indicate that C-SNAM functions as an imaging probe for stem cell apoptosis in MASI. This concept could be applied to a broad range of cell transplants and target sites

Development of Novel Tumor‐Targeted Theranostic Nanoparticles Activated by Membrane‐Type Matrix Metalloproteinases for Combined Cancer Magnetic Resonance Imaging and Therapy

A major drawback with current cancer therapy is the prevalence of unrequired dose-limiting toxicity to non-cancerous tissues and organs, which is further compounded by a limited ability to rapidly and easily monitor drug delivery, pharmacodynamics and therapeutic response. In this report, the design and characterization of novel multifunctional "theranostic" nanoparticles (TNPs) is described for enzyme-specific drug activation at tumor sites and simultaneous in vivo magnetic resonance imaging (MRI) of drug delivery. TNPs are synthesized by conjugation of FDA-approved iron oxide nanoparticles ferumoxytol to an MMP-activatable peptide conjugate of azademethylcolchicine (ICT), creating CLIO-ICTs (TNPs). Significant cell death is observed in TNP-treated MMP-14 positive MMTV-PyMT breast cancer cells in vitro, but not MMP-14 negative fibroblasts or cells treated with ferumoxytol alone. Intravenous administration of TNPs to MMTV-PyMT tumor-bearing mice and subsequent MRI demonstrates significant tumor selective accumulation of the TNP, an observation confirmed by histopathology. Treatment with CLIO-ICTs induces a significant antitumor effect and tumor necrosis, a response not observed with ferumoxytol. Furthermore, no toxicity or cell death is observed in normal tissues following treatment with CLIO-ICTs, ICT, or ferumoxytol. These findings demonstrate proof of concept for a new nanotemplate that integrates tumor specificity, drug delivery and in vivo imaging into a single TNP entity through attachment of enzyme-activated prodrugs onto magnetic nanoparticles. This novel approach holds the potential to significantly improve targeted cancer therapies, and ultimately enable personalized therapy regimens

Iron Administration before Stem Cell Harvest Enables MR Imaging Tracking after Transplantation

PurposeTo determine whether intravenous ferumoxytol can be used to effectively label mesenchymal stem cells (MSCs) in vivo and can be used for tracking of stem cell transplants.Materials and methodsThis study was approved by the institutional animal care and use committee. Sprague-Dawley rats (6-8 weeks old) were injected with ferumoxytol 48 hours prior to extraction of MSCs from bone marrow. Ferumoxytol uptake by these MSCs was evaluated with fluorescence, confocal, and electron microscopy and compared with results of traditional ex vivo-labeling procedures. The in vivo-labeled cells were subsequently transplanted in osteochondral defects of 14 knees of seven athymic rats and were evaluated with magnetic resonance (MR) imaging up to 4 weeks after transplantation. T2 relaxation times of in vivo-labeled MSC transplants and unlabeled control transplants were compared by using t tests. MR data were correlated with histopathologic results.ResultsIn vivo-labeled MSCs demonstrated significantly higher ferumoxytol uptake compared with ex vivo-labeled cells. With electron microscopy, iron oxide nanoparticles were localized in secondary lysosomes. In vivo-labeled cells demonstrated significant T2 shortening effects in vitro and in vivo when they were compared with unlabeled control cells (T2 in vivo, 15.4 vs 24.4 msec; P &lt; .05) and could be tracked in osteochondral defects for 4 weeks. Histologic examination confirmed the presence of iron in labeled transplants and defect remodeling.ConclusionIntravenous ferumoxytol can be used to effectively label MSCs in vivo and can be used for tracking of stem cell transplants with MR imaging. This method eliminates risks of contamination and biologic alteration of MSCs associated with ex vivo-labeling procedures

Iron Administration before Stem Cell Harvest Enables MR Imaging Tracking after Transplantation

PURPOSE: To determine whether intravenous ferumoxytol can be used to effectively label mesenchymal stem cells (MSCs) in vivo and can be used for tracking of stem cell transplants. MATERIALS AND METHODS: This study was approved by the institutional animal care and use committee. Sprague-Dawley rats (6–8 weeks old) were injected with ferumoxytol 48 hours prior to extraction of MSCs from bone marrow. Ferumoxytol uptake by these MSCs was evaluated with fluorescence, confocal, and electron microscopy and compared with results of traditional ex vivo–labeling procedures. The in vivo–labeled cells were subsequently transplanted in osteochondral defects of 14 knees of seven athymic rats and were evaluated with magnetic resonance (MR) imaging up to 4 weeks after transplantation. T2 relaxation times of in vivo–labeled MSC transplants and unlabeled control transplants were compared by using t tests. MR data were correlated with histopathologic results. RESULTS: In vivo–labeled MSCs demonstrated significantly higher ferumoxytol uptake compared with ex vivo–labeled cells. With electron microscopy, iron oxide nanoparticles were localized in secondary lysosomes. In vivo–labeled cells demonstrated significant T2 shortening effects in vitro and in vivo when they were compared with unlabeled control cells (T2 in vivo, 15.4 vs 24.4 msec; P < .05) and could be tracked in osteochondral defects for 4 weeks. Histologic examination confirmed the presence of iron in labeled transplants and defect remodeling. CONCLUSION: Intravenous ferumoxytol can be used to effectively label MSCs in vivo and can be used for tracking of stem cell transplants with MR imaging. This method eliminates risks of contamination and biologic alteration of MSCs associated with ex vivo–labeling procedures. © RSNA, 2013 Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13130858/-/DC