Distraction osteogenesis in TNF receptor 1 deficient mice is protected from chronic ethanol exposure

Immunomodulatory effects and mechanisms of distraction osteogenesis

Distraction osteogenesis (DO) is widely used for bone tissue engineering technology. Immune regulations play important roles in the process of DO like other bone regeneration mechanisms. Compared with others, the immune regulation processes of DO have their distinct features. In this review, we summarized the immune-related events including changes in and effects of immune cells, immune-related cytokines, and signaling pathways at different periods in the process of DO. We aim to elucidated our understanding and unknowns about the immunomodulatory role of DO. The goal of this is to use the known knowledge to further modify existing methods of DO, and to develop novel DO strategies in our unknown areas through more detailed studies of the work we have done.

Impact of Alcohol on Bone Health, Homeostasis and Fracture repair

Purpose of review

Alcohol use continues to rise globally. We review the current literature on the effect of alcohol on bone health, homeostasis and fracture repair to highlight what has been learned in people and animal models of alcohol consumption.

Recent findings

Recently, forkhead box O (FoxO) has been found to be upregulated and activated in mesenchymal stem cells (MSC) exposed to alcohol. FoxO has also been found to modulate Wnt/β-catenin signaling, which is necessary for MSC differentiation. Recent evidence suggests alcohol activates FoxO signaling, which may be dysregulating Wnt/β-catenin signaling in MSCs cultured in alcohol.

Summary

This review highlights the negative health effects learned from people and chronic and episodic binge alcohol consumption animal models. Studies using chronic alcohol exposure or alcohol exposure then bone fracture repair model have explored several different cellular and molecular signaling pathways important for bone homeostasis and fracture repair, and offer potential for future experiments to explore additional signaling pathways that may be dysregulated by alcohol exposure.

Ethanol Inhibits Mesenchymal Stem Cell Osteochondral Lineage Differentiation Due in Part to an Activation of Forkhead Box Protein O-Specific Signaling

BACKGROUND

During bone fracture repair, resident mesenchymal stem cells (MSCs) differentiate into chondrocytes, to form a cartilaginous fracture callus, and osteoblasts, to ossify the collagen matrix. Our laboratory previously reported that alcohol administration led to decreased cartilage formation within the fracture callus of rodents and this effect was mitigated by postfracture antioxidant treatment. Forkhead box protein O (FoxO) transcription factors are activated in response to intracellular reactive oxygen species (ROS), and alcohol has been shown to increase ROS. Activation of FoxOs has also been shown to inhibit canonical Wnt signaling, a necessary pathway for MSC differentiation. These findings have led to our hypothesis that alcohol exposure decreases osteochondrogenic differentiation of MSCs through the activation of FoxOs.

METHODS

Primary rat MSCs were treated with ethanol (EtOH) and assayed for FoxO expression, FoxO activation, and downstream target expression. Next, MSCs were differentiated toward osteogenic or chondrogenic lineages in the presence of 50 mM EtOH and alterations in osteochondral lineage marker expression were determined. Lastly, osteochondral differentiation experiments were repeated with FoxO1/3 knockdown or with FoxO1/3 inhibitor AS1842856 and osteochondral lineage marker expression was determined.

RESULTS

EtOH increased the expression of FoxO3a at mRNA and protein levels in primary cultured MSCs. This was accompanied by an increase in FoxO1 nuclear localization, FoxO1 activation, and downstream catalase expression. Moreover, EtOH exposure decreased expression of osteogenic and chondrogenic lineage markers. FoxO1/3 knockdown restored proosteogenic and prochondrogenic lineage marker expression in the presence of 50 mM EtOH. However, FoxO1/3 inhibitor only restored proosteogenic lineage marker expression.

CONCLUSIONS

These data show that EtOH has the ability to inhibit MSC differentiation, and this ability may rely, at least partially, on the activation of FoxO transcription factors.

Surgically‑induced mouse models in the study of bone regeneration: Current models and future directions (Review)

Bone regeneration has been extensively studied over the past several decades. The surgically‑induced mouse model is the key animal model for studying bone regeneration, of the various research strategies used. These mouse models mimic the trauma and recovery processes in vivo and serve as carriers for tissue engineering and gene modification to test various therapies or associated genes in bone regeneration. The present review introduces a classification of surgically induced mouse models in bone regeneration, evaluates the application and value of these models and discusses the potential development of further innovations in this field in the future.

Chronic alcohol consumption potentiates the development of diabetes through pancreatic β-cell dysfunction

Chronic ethanol consumption is well established as a major risk factor for type-2 diabetes (T2D), which is evidenced by impaired glucose metabolism and insulin resistance. However, the relationships between alcohol consumption and the development of T2D remain controversial. In particular, the direct effects of ethanol consumption on proliferation of pancreatic β-cell and the exact mechanisms associated with ethanol-mediated β-cell dysfunction and apoptosis remain elusive. Although alcoholism and alcohol consumption are prevalent and represent crucial public health problems worldwide, many people believe that low-to-moderate ethanol consumption may protect against T2D and cardiovascular diseases. However, the J- or U-shaped curves obtained from cross-sectional and large prospective studies have not fully explained the relationship between alcohol consumption and T2D. This review provides evidence for the harmful effects of chronic ethanol consumption on the progressive development of T2D, particularly with respect to pancreatic β-cell mass and function in association with insulin synthesis and secretion. This review also discusses a conceptual framework for how ethanol-produced peroxynitrite contributes to pancreatic β-cell dysfunction and metabolic syndrome.

Alcoholism: A systemic proinflammatory condition

Excessive ethanol consumption affects virtually any organ, both by indirect and direct mechanisms. Considerable research in the last two decades has widened the knowledge about the paramount importance of proinflammatory cytokines and oxidative damage in the pathogenesis of many of the systemic manifestations of alcoholism. These cytokines derive primarily from activated Kupffer cells exposed to Gram-negative intestinal bacteria, which reach the liver in supra-physiological amounts due to ethanol-mediated increased gut permeability. Reactive oxygen species (ROS) that enhance the inflammatory response are generated both by activation of Kupffer cells and by the direct metabolic effects of ethanol. The effects of this increased cytokine secretion and ROS generation lie far beyond liver damage. In addition to the classic consequences of endotoxemia associated with liver cirrhosis that were described several decades ago, important research in the last ten years has shown that cytokines may also induce damage in remote organs such as brain, bone, muscle, heart, lung, gonads, peripheral nerve, and pancreas. These effects are even seen in alcoholics without significant liver disease. Therefore, alcoholism can be viewed as an inflammatory condition, a concept which opens the possibility of using new therapeutic weapons to treat some of the complications of this devastating and frequent disease. In this review we examine some of the most outstanding consequences of the altered cytokine regulation that occurs in alcoholics in organs other than the liver.

Impact of the environment on the skeleton: is it modulated by genetic factors?

The etiology of skeletal disease is driven by genetic and environmental factors. Genome-wide association studies (GWAS) of osteoporotic phenotypes have identified novel candidate genes, but have only uncovered a small proportion of the trait variance explained. This "missing heritability" is caused by several factors, including the failure to consider gene-by-environmental (G*E) interactions. Some G*E interactions have been investigated, but new approaches to integrate environmental data into genomic studies are needed. Advances in genotyping and meta-analysis techniques now allow combining genotype data from multiple studies, but the measurement of key environmental factors in large human cohorts still lags behind, as do the statistical tools needed to incorporate these measures in genome-wide association meta-studies. This review focuses on discussing ways to enhance G*E interaction studies in humans and how the use of rodent models can inform genetic studies. Understanding G*E interactions will provide opportunities to effectively target intervention strategies for individualized therapy.