Reproducibility2020: Progress and priorities.

The preclinical research process is a cycle of idea generation, experimentation, and reporting of results. The biomedical research community relies on the reproducibility of published discoveries to create new lines of research and to translate research findings into therapeutic applications. Since 2012, when scientists from Amgen reported that they were able to reproduce only 6 of 53 "landmark" preclinical studies, the biomedical research community began discussing the scale of the reproducibility problem and developing initiatives to address critical challenges.

Matched preclinical designs for improved translatability.

A more stratified preclinical design strategy will increase the statistical power and reproducibility of animal studies and their translatability.

[Letter to the Editor] The need for improved education and training in research antibody usage and validation practices.

Address correspondence to Leonard P. Freedman, Global Biological Standards Institute, 1020 19th Street, NW, Suite 550, Washington, DC, 20036. E-mail: lfreedman@gbsi.

The Economics of Reproducibility in Preclinical Research.

Low reproducibility rates within life science research undermine cumulative knowledge production and contribute to both delays and costs of therapeutic drug development. An analysis of past studies indicates that the cumulative (total) prevalence of irreproducible preclinical research exceeds 50%, resulting in approximately US$28,000,000,000 (US$28B)/year spent on preclinical research that is not reproducible-in the United States alone. We outline a framework for solutions and a plan for long-term improvements in reproducibility rates that will help to accelerate the discovery of life-saving therapies and cures.

The increasing urgency for standards in basic biologic research.

Research advances build upon the validity and reproducibility of previously published data and findings. Yet irreproducibility in basic biologic and preclinical research is pervasive in both academic and commercial settings. Lack of reproducibility has led to invalidated research breakthroughs, retracted articles, and aborted clinical trials.

Liver X receptor-retinoid X receptor (LXR-RXR) heterodimer cistrome reveals coordination of LXR and AP1 signaling in keratinocytes.

Liver X receptors (LXRs) play a critical role in regulating lipid synthesis and transport in numerous tissues. In the skin, activation of LXR induces keratinocyte differentiation and improves epidermal permeability barrier homeostasis. To elucidate the mechanism of LXR action in skin, we mapped its cistrome by identifying LXRβ-RXRα binding sites using ChIP-on-chip in normal human epidermal keratinocytes (NHEKs).

Identification of 5α, 6α-epoxycholesterol as a novel modulator of liver X receptor activity.

The liver X receptors (LXRα and LXRβ) are members of the nuclear receptor superfamily that function as key transcriptional regulators of a number of biological processes, including cholesterol homeostasis, lipid metabolism, and keratinocyte differentiation. Natural ligands that activate LXRs include oxysterol derivatives such as 25-hydroxycholesterol, 27-hydroxycholesterol, 22(R)-hydroxycholesterol, 20(S)-hydroxycholesterol, and 24(S),25-epoxycholesterol. Related oxysterols, such as 5α,6α-epoxycholesterol (5,6-EC) are present in a number of foods and have been shown to induce atherosclerosis in animal models.

Discovery of the selective androgen receptor modulator MK-0773 using a rational development strategy based on differential transcriptional requirements for androgenic anabolism versus reproductive physiology.

Selective androgen receptor modulators (SARMs) are androgen receptor (AR) ligands that induce anabolism while having reduced effects in reproductive tissues. In various experimental contexts SARMs fully activate, partially activate, or even antagonize the AR, but how these complex activities translate into tissue selectivity is not known. Here, we probed receptor function using >1000 synthetic AR ligands.

Estrogen receptor beta is a novel therapeutic target for photoaging.

One of the many harmful factors faced by the skin is solar UV radiation, which damages skin by inducing chronic low-grade inflammation through increased expression of proinflammatory cytokines, metalloproteinases (MMPs) and cyclooxygenase-2 (COX-2). Estrogen receptors (ERs) alpha and beta are ligand-dependent transcription factors that are expressed in skin, and an ERbeta agonist has previously shown efficacy in vivo in models of pain and inflammation. Because ERbeta does not carry the breast and uterine proliferation liabilities of ERalpha, we decided to explore the possibility of using ERbeta as a target for photoaging.

Androgen-mediated improvement of body composition and muscle function involves a novel early transcriptional program including IGF1, mechano growth factor, and induction of {beta}-catenin.

Androgens promote anabolism in the musculoskeletal system while generally repressing adiposity, leading to lean body composition. Circulating androgens decline with age, contributing to frailty, osteoporosis, and obesity; however, the mechanisms by which androgens modulate body composition are largely unknown. Here, we demonstrate that aged castrated rats develop increased fat mass, reduced muscle mass and strength, and lower bone mass.

Differential biochemical and cellular actions of Premarin estrogens: distinct pharmacology of bazedoxifene-conjugated estrogens combination.

The use of estrogen-based therapies and the selective estrogen receptor (ER) modulator (SERM), raloxifene, which are approved for postmenopausal osteoporosis, is associated with side effects such as uterine/breast hyperproliferation, thromboembolism, and hot flashes. A combination of a new SERM, bazedoxifene (BZA), and Premarin (conjugated estrogens; CE) is under investigation to mitigate the estrogen/SERM side effects with promising results in Phase III clinical trials. To explore the mechanism of BZA/CE action, we investigated the recruitment of cofactor peptides to ERalpha by components of CE and a mixture containing the 10 major components of CE with or without three different SERMs.

Liver X receptor is a therapeutic target for photoaging and chronological skin aging.

Liver X receptors (LXRalpha and -beta) are liposensors that exert their metabolic effects by orchestrating the expression of macrophage genes involved in lipid metabolism and inflammation. LXRs are also expressed in other tissues, including skin, where their natural oxysterol ligands induce keratinocyte differentiation and improve epidermal barrier function. To extend the potential use of LXR ligands to dermatological indications, we explored the possibility of using LXR as a target for skin aging.

MNAR plays an important role in ERa activation of Src/MAPK and PI3K/Akt signaling pathways.

Estrogens play a critical role in the regulation of cellular proliferation, differentiation, and apoptosis. Evidence indicates that this regulation is mediated by a complex interface of direct control of gene expression (so-called "genomic action") and by regulation of cell-signaling/phosphorylation cascades (referred to as the "non-genomic", or "extranuclear" action). However, the mechanisms of the non-genomic action of estrogens are not well defined.

Estrogen protects bone by inducing Fas ligand in osteoblasts to regulate osteoclast survival.

Estrogen deficiency in menopause is a major cause of osteoporosis in women. Estrogen acts to maintain the appropriate ratio between bone-forming osteoblasts and bone-resorbing osteoclasts in part through the induction of osteoclast apoptosis. Recent studies have suggested a role for Fas ligand (FasL) in estrogen-induced osteoclast apoptosis by an autocrine mechanism involving osteoclasts alone.

Selective androgen receptor modulators for frailty and osteoporosis.

Androgens play an important role not only in male sexual differentiation, puberty, sexual behavior and spermatogenesis, but also in the maintenance of bone architecture and muscle mass and strength. For decades, steroidal androgens have been used by hypogonadal and aging men as hormone replacement therapy, and abused by prominent athletes as anabolic agents for enhancing physical performance. The use of steroidal androgens is associated with hepatotoxicity, potential for prostate stimulation, virilizing actions and other side effects resulting from their cross-reactivity to related steroid receptors.