Faculty Bibliography

The differentiated state of somatic cells provides barriers for the derivation of induced pluripotent stem cells (iPSCs). To address why some cell types reprogram more readily than others, we studied the effect of combined modulation of cellular signaling pathways. Surprisingly, inhibition of transforming growth factor beta (TGF-beta) together with activation of Wnt signaling in the presence of ascorbic acid allows >80% of murine fibroblasts to acquire pluripotency after 1 week of reprogramming factor expression. In contrast, hepatic and blood progenitors predominantly required only TGF-beta inhibition or canonical Wnt activation, respectively, to reprogram at efficiencies approaching 100%. Strikingly, blood progenitors reactivated endogenous pluripotency loci in a highly synchronous manner, and we demonstrate that expression of specific chromatin-modifying enzymes and reduced TGF-beta/mitogen-activated protein (MAP) kinase activity are intrinsic properties associated with the unique reprogramming response of these cells. Our observations define cell-type-specific requirements for the rapid and synchronous reprogramming of somatic cells.

Liver X receptors (LXRs) attenuate inflammation by modulating the expression of key inflammatory genes, making LXRs and their ligands particularly attractive candidates for therapeutic intervention in cardiovascular, metabolic, and/or inflammatory diseases. Herein, enhanced proresolving activity of polymeric nanoparticles (NPs) containing the synthetic LXR agonist GW3965 (LXR-NPs) is demonstrated, developed from a combinatorial library of more than 70 formulations with variations in critical physicochemical parameters. In vitro studies on peritoneal macrophages confirm that LXR-NPs are significantly more effective than the free agonist at downregulating pro-inflammatory mediators (MCP-1 and TNFalpha), as well as inducing the expression of LXR target genes (ABCA1 and SREBP1c). Through a zymosan-induced acute peritonitis in vivo model, LXR-NPs are found to be more efficient than free GW3965 at limiting the recruitment of polymononuclear neutrophils (50% vs 17%), suppressing the gene expression and secretion of pro-inflammatory factors MCP-1 and TNFalpha in peritoneal macrophages, and decreasing the resolution interval up to 4 h. Furthermore, LXR-NPs suppress the secretion of MCP-1 and TNFalpha by monocytes and macrophages more efficiently than the commercial drug dexamethasone. Overall, these findings demonstrate that LXR-NPs are capable of promoting resolution of inflammation and highlight the prospect of LXR-based nanotherapeutics for inflammatory diseases.

Polarization of early embryos along cell contact patterns-referred to in this paper as radial polarization-provides a foundation for the initial cell fate decisions and morphogenetic movements of embryogenesis. Although polarity can be established through distinct upstream mechanisms in Caenorhabditis elegans, Xenopus laevis, and mouse embryos, in each species, it results in the restriction of PAR polarity proteins to contact-free surfaces of blastomeres. In turn, PAR proteins influence cell fates by affecting signaling pathways, such as Hippo and Wnt, and regulate morphogenetic movements by directing cytoskeletal asymmetries.

With increasing numbers of people with Alzheimer's and other dementias across the globe, many countries have developed national plans to deal with the resulting challenges. In the United States, the National Alzheimer's Project Act, signed into law in 2011, required the creation of such a plan with annual updates thereafter. Pursuant to this, the US Department of Health and Human Services (HHS) released the National Plan to Address Alzheimer's Disease in 2012, including an ambitious research goal of preventing and effectively treating Alzheimer's disease by 2025. To guide investments, activities, and the measurement of progress toward achieving this 2025 goal, in its first annual plan update (2013) HHS also incorporated into the plan a set of short, medium and long-term milestones. HHS further committed to updating these milestones on an ongoing basis to account for progress and setbacks, and emerging opportunities and obstacles. To assist HHS as it updates these milestones, the Alzheimer's Association convened a National Plan Milestone Workgroup consisting of scientific experts representing all areas of Alzheimer's and dementia research. The workgroup evaluated each milestone and made recommendations to ensure that they collectively constitute an adequate work plan for reaching the goal of preventing and effectively treating Alzheimer's by 2025. This report presents these Workgroup recommendations.

RATIONALE: Diabetes mellitus increases cardiovascular disease risk in humans and remains elevated despite cholesterol-lowering therapy with statins. Consistent with this, in mouse models, diabetes mellitus impairs atherosclerosis plaque regression after aggressive cholesterol lowering. MicroRNA 33 (miR33) is a key negative regulator of the reverse cholesterol transport factors, ATP-binding cassette transporter A1 and high-density lipoprotein, which suggested that its inhibition may overcome this impairment. OBJECTIVE: To assess the effects of miR33 inhibition on atherosclerosis regression in diabetic mice. METHODS AND RESULTS: Reversa mice, which are deficient in the low-density lipoprotein receptor and in which hypercholesterolemia is reversed by conditional inactivation of the microsomal triglyceride transfer protein gene, were placed on an atherogenic diet for 16 weeks, then either made diabetic by streptozotocin injection or kept normoglycemic. Lipid-lowering was induced by microsomal triglyceride transfer protein gene inactivation, and mice were treated with anti-miR33 or control oligonucleotides. Although regression was impaired in diabetic mice treated with control oligonucleotides, anti-miR33 treatment decreased plaque macrophage content and inflammatory gene expression in these mice. The decreased macrophage content in anti-miR33 treated diabetic mice was associated with a blunting of hyperglycemia-induced monocytosis and reduced monocyte recruitment to the plaque, which was traced to an inhibition of the proliferation of bone marrow monocyte precursors associated with the upregulation of their Abca1. CONCLUSIONS: miR33 inhibition overcomes deleterious effects of diabetes mellitus in atherosclerosis regression in mice, which suggests a therapeutic strategy in diabetic patients, who remain at elevated cardiovascular disease risk, despite plasma cholesterol lowering.

Stem cells give rise to tissues and organs during development and maintain their integrity during adulthood. They have the potential to self-renew or differentiate at each division. To ensure proper organ growth and homeostasis, self-renewal versus differentiation decisions need to be tightly controlled. Systematic genetic studies in Drosophila melanogaster are revealing extensive regulatory networks that control the switch between stem cell self-renewal and differentiation in the germline. These networks, which are based primarily on mutual translational repression, act via interlocked feedback loops to provide robustness to this important fate decision.

Vitamin D plays crucial roles in neuroprotection and neurodevelopment, and low levels are commonly associated with schizophrenia. We considered if the association was spurious or causal by examining the association of Vitamin D with Leukocyte Telomere Length (LTL), a marker of cellular aging. Vitamin D levels in 22 well-characterized schizophrenia cases were examined with respect to symptoms, cognition, and functioning. LTL was assessed using quantitative polymerase chain reaction (qPCR). The results showed that 91% (20) had deficient or insufficient Vitamin D levels, which were associated with excitement and grandiosity, social anhedonia, and poverty of speech. Sex-specific analyses showed strong associations of hypovitamintosis D to negative symptoms and decreased premorbid adjustment in males, and to lesser hallucinations and emotional withdrawal, but increased anti-social aggression in females. In females LTL was furthermore associated with Vitamin D levels. This study demonstrates a relationship of low vitamin D levels with increased cellular aging in females. It is also the first study to demonstrate potential sex-specific profiles among schizophrenia cases with hypovitaminosis.