Lipocalin 2 Influences Bone and Muscle Phenotype in the MDX Mouse Model of Duchenne Muscular Dystrophy

Transcriptional analysis of cancer cachexia: conserved and unique features across preclinical models and biological sex

Studies suggest heterogeneity in cancer cachexia (CC) among models and biological sexes, yet examinations comparing models and sexes are scarce. We compared the transcriptional landscape of skeletal muscle across murine CC models and biological sexes during early and late CC. Global gene expression analyses were performed on gastrocnemius [Lewis lung carcinoma (LLC)], quadriceps (KPC-pancreatic), and tibialis anterior [Colon-26 (C26)-colorectal and ApcMin/+] muscles across biological sexes. Differentially expressed genes (DEGs) were identified using an adj-P value of <0.05, followed by pathway and computational cistrome analyses. Integrating all controls, early and late stages of all models and sexes revealed up to 68% of DEGs and pathways were enriched at early and late CC, indicating a conserved transcriptional profile during CC development. Comparing DEGs and pathways within sexes and across models, in early CC, the transcriptional response was highly heterogeneous. At late stage, 11.5% of upregulated and 10% of downregulated genes were shared between models in males, whereas 18.9% of upregulated and 7% of downregulated DEGs were shared in females. Shared DEGs were enriched in proteasome and mitophagy/autophagy pathways (upregulated), and downregulation of energy metabolism pathways in males only. Between sexes, though the proportion of shared DEGs was low (<16%), similar pathway enrichment was observed, including proteasome and mitophagy at late-stage CC. In early CC, oncostatin M receptor (Osmr) upregulation was the only commonality across all models and sexes, whereas CLOCK and ARNTL/BMAL1 were predicted transcriptional factors associated with dysregulations in all three male models. This study highlights sex and model differences in CC progression and suggests conserved transcriptional changes as potential therapeutic targets.NEW & NOTEWORTHY This study is among the first to integrate and compare the skeletal muscle transcriptional landscape across multiple preclinical models and biological sexes. We highlight that 1) early CC transcriptional changes are two-thirds conserved at late stages, 2) DEGs are largely model and sex specific, and 3) transcriptional factors including CLOCK and ARNTL/BMAL1, which influence early CC gene expression, might represent a global therapeutic target with a chance of efficacy across various cancer types.

Poor bone health in Duchenne muscular dystrophy: a multifactorial problem beyond corticosteroids and loss of ambulation

Duchenne muscular dystrophy (DMD) is a progressive, fatal muscle wasting disease caused by X-linked mutations in the dystrophin gene. Alongside the characteristic muscle weakness, patients face a myriad of skeletal complications, including osteoporosis/osteopenia, high susceptibility to vertebral and long bone fractures, fat embolism post-fracture, scoliosis, and growth retardation. Those skeletal abnormalities significantly compromise quality of life and are sometimes life-threatening. These issues were traditionally attributed to loss of ambulation and chronic corticosteroid use, but recent investigations have unveiled a more intricate etiology. Factors such as vitamin D deficiency, hormonal imbalances, systemic inflammation, myokine release from dystrophic muscle, and vascular dysfunction are emerging as significant contributors as well. This expanded understanding illuminates the multifaceted pathogenesis underlying skeletal issues in DMD. Present therapeutic options are limited and lack specificity. Advancements in understanding the pathophysiology of bone complications in DMD will offer promising avenues for novel treatment modalities. In this review, we summarize the current understanding of factors contributing to bone problems in DMD and delineate contemporary and prospective multidisciplinary therapeutic approaches.

Adipose tissue in older individuals: a contributing factor to sarcopenia

Sarcopenia is a geriatric syndrome characterized by a functional decline in muscle. The prevalence of sarcopenia increases with natural aging, becoming a serious health problem among elderly individuals. Therefore, understanding the pathology of sarcopenia is critical for inhibiting age-related alterations and promoting health and longevity in elderly individuals. The development of sarcopenia may be influenced by interactions between visceral and subcutaneous adipose tissue and skeletal muscle, particularly under conditions of chronic low-grade inflammation and metabolic dysfunction. This hypothesis is supported by the following observations: (i) accumulation of senescent cells in both adipose tissue and skeletal muscle with age; (ii) gut dysbiosis, characterized by an imbalance in gut microbial communities as the main trigger for inflammation, sarcopenia, and aged adipose tissue; and (iii) microbial dysbiosis, which could impact the onset or progression of a senescent state. Moreover, adipose tissue acts as an endocrine organ, releasing molecules that participate in intricate communication networks between organs. Our discussion focuses on novel adipokines and their role in regulating adipose tissue and muscle, particularly those influenced by aging and obesity, emphasizing their contributions to disease development. On the basis of these findings, we propose that age-related adipose tissue and sarcopenia are disorders characterized by chronic inflammation and metabolic dysregulation. Finally, we explore new potential therapeutic strategies involving specialized proresolving mediator (SPM) G protein-coupled receptor (GPCR) agonists, non-SPM GPCR agonists, transient receptor potential (TRP) channels, antidiabetic drugs in conjunction with probiotics and prebiotics, and compounds designed to target senescent cells and mitigate their pro-inflammatory activity.

Towards in vivo photoacoustic human imaging: Shining a new light on clinical diagnostics

Multiscale visualization of human anatomical structures is revolutionizing clinical diagnosis and treatment. As one of the most promising clinical diagnostic techniques, photoacoustic imaging (PAI), or optoacoustic imaging, bridges the spatial-resolution gap between pure optical and ultrasonic imaging techniques, by the modes of optical illumination and acoustic detection. PAI can non-invasively capture multiple optical contrasts from the endogenous agents such as oxygenated/deoxygenated hemoglobin, lipid and melanin or a variety of exogenous specific biomarkers to reveal anatomy, function, and molecular for biological tissues in vivo, showing significant potential in clinical diagnostics. In 2001, the worldwide first clinical prototype of the photoacoustic system was used to screen breast cancer in vivo, which opened the prelude to photoacoustic clinical diagnostics. Over the past two decades, PAI has achieved monumental discoveries and applications in human imaging. Progress towards preclinical/clinical applications includes breast, skin, lymphatics, bowel, thyroid, ovarian, prostate, and brain imaging, etc., and there is no doubt that PAI is opening new avenues to realize early diagnosis and precise treatment of human diseases. In this review, the breakthrough researches and key applications of photoacoustic human imaging in vivo are emphatically summarized, which demonstrates the technical superiorities and emerging applications of photoacoustic human imaging in clinical diagnostics, providing clinical translational orientations for the photoacoustic community and clinicians. The perspectives on potential improvements of photoacoustic human imaging are finally highlighted.

Lipocalin-2 as a fundamental protein in type 2 diabetes and periodontitis in mice

BACKGROUND

Lipocalin-2 (LCN-2) is an osteokine that suppresses appetite, stimulates insulin secretion, regulates bone remodeling, and is induced by proinflammatory cytokines. The aim of this work was to investigate the participation of LCN-2 in periodontitis associated with type 2 diabetes (T2D) by evaluating alveolar bone loss, glycemic control, inflammation, and femur fragility.

METHODS

A murine model of periodontitis with T2D and elevated LCN-2 concentration was used. Functional LCN-2 inhibition was achieved using an anti-LCN-2 polyclonal antibody, and isotype immunoglobulin G was used as a control. The alveolar bone and femur were evaluated by micro-CT. Glucose metabolism was determined. Tumor necrosis factor (TNF-α) and receptor activator of nuclear factor kappa-B ligand (RANKL) levels in alveolar bone lysates were quantified using ELISA, and serum cytokines were quantified using flow cytometry. A three-point bending test was performed in the femur, and RANKL levels were measured in femur lysates using ELISA.

RESULTS

Functional inhibition of LCN-2 in T2D-periodontitis mice decreased alveolar bone loss in buccal and palatal surfaces and preserved the microarchitecture of the remaining bone, decreased TNF-α and RANKL in alveolar bone, reduced hyperglycemia, glucose intolerance, and insulin resistance, and increased insulin production through improving the functionality of pancreatic β cells. Furthermore, this inhibition increased serum free-glycerol levels, decreased serum interleukin (IL)-6, increased serum IL-4, and reduced femur fragility and RANKL expression in the femur.

CONCLUSIONS

LCN-2 participates in periodontitis associated with T2D. Inhibiting its function in mice with T2D and periodontitis improves pancreatic β-cell function, and glucose metabolism and decreases inflammatory cytokines and bone-RANKL levels, which results in the preservation of femoral and alveolar bone microarchitecture.

PLAIN LANGUAGE SUMMARY

In this study, we explored the role of a bone protein known as lipocalin-2 (LCN-2) in the connection between periodontitis and type 2 diabetes (T2D). Periodontitis is a destructive gum and alveolar bone disease. LCN-2 levels are increased in both T2D and periodontitis. Using a mouse model of T2D with periodontitis, we examined how blocking LCN-2 function affected various aspects of these two diseases. We found that this inhibition led to significant improvements. First, it reduced alveolar bone loss and preserved bone structure by decreasing local inflammation and bone resorption. Second, it improved glucose and lipid metabolism, leading to better blood-sugar control and decreased insulin resistance. Blocking the functions of LCN-2 also decreased systemic inflammation throughout the body and strengthened bone integrity. Overall, our results suggest that LCN-2 plays a crucial role in the periodontitis associated with T2D. By inhibiting LCN-2 function, we were able to improve pancreatic function, improve glucose metabolism, reduce inflammation, and enhance bone health. Targeting LCN-2 could be a promising strategy for the harmful effects of T2D and periodontitis.

A Machine Learning Framework for Screening Plasma Cell-Associated Feature Genes to Estimate Osteoporosis Risk and Treatment Vulnerability

Osteoporosis, in which bones become fragile owing to low bone density and impaired bone mass, is a global public health concern. Bone mineral density (BMD) has been extensively evaluated for the diagnosis of low bone mass and osteoporosis. Circulating monocytes play an indispensable role in bone destruction and remodeling. This work proposed a machine learning-based framework to investigate the impact of circulating monocyte-associated genes on bone loss in osteoporosis patients. Females with discordant BMD levels were included in the GSE56815, GSE7158, GSE7429, and GSE62402 datasets. Circulating monocyte types were quantified via CIBERSORT, with subsequent selection of plasma cell-associated DEGs. Generalized linear models, random forests, extreme gradient boosting (XGB), and support vector machines were adopted for feature selection. Artificial neural networks and nomograms were subsequently constructed for osteoporosis diagnosis, and the molecular machinery underlying the identified genes was explored. SVM outperformed the other tuned models; thus, the expression of several genes (DEFA4, HLA-DPB1, LCN2, HP, and GAS7) associated with osteoporosis were determined. ANNs and nomograms were proposed to robustly distinguish low and high BMDs and estimate the risk of osteoporosis. Clozapine, aspirin, pyridoxine, etc. were identified as possible treatment agents. The expression of these genes is extensively posttranscriptionally regulated by miRNAs and m6A modifications. Additionally, they participate in modulating key signaling pathways, e.g., autophagy. The machine learning framework based on plasma cell-associated feature genes has the potential for estimating personalized risk stratification and treatment vulnerability in osteoporosis patients.

Pre-proenkephalin 1 is Downregulated Under Unloading and is Involved in Osteoblast Biology

Pre-proenkephalin 1 (Penk1) is a pro-neuropeptide that belongs to the typical opioid peptide's family, having analgesic properties. We previously found Penk1 to be the most downregulated gene in a whole gene profiling analysis performed in osteoblasts subjected to microgravity as a model of mechanical unloading. In this work, Penk1 downregulation was confirmed in the bones of two in vivo models of mechanical unloading: tail-suspended and botulinum toxin A (botox)-injected mice. Consistently, in the sera from healthy volunteers subjected to bed rest, we observed an inverse correlation between PENK1 and bed rest duration. These results prompted us to investigate a role for this factor in bone. Penk1 was highly expressed in mouse bone, but its global deletion failed to impact bone metabolism in vivo. Indeed, Penk1 knock out (Penk1-/-) mice did not show an overt bone phenotype compared to the WT littermates. Conversely, in vitro Penk1 gene expression progressively increased during osteoblast differentiation and its transient silencing in mature osteoblasts by siRNAs upregulated the transcription of the Sost1 gene encoding sclerostin, and decreased Wnt3a and Col1a1 mRNAs, suggesting an altered osteoblast activity due to an impairment of the Wnt pathway. In line with this, osteoblasts treated with the Penk1 encoded peptide, Met-enkephalin, showed an increase of Osx and Col1a1 mRNAs and enhanced nodule mineralization. Interestingly, primary osteoblasts isolated from Penk1-/- mice showed lower metabolic activity, ALP activity, and nodule mineralization, as well as a lower number of CFU-F compared to osteoblasts isolated from WT mice, suggesting that, unlike the transient inhibition, the chronic Penk1 deletion affects both osteoblast differentiation and activity. Taken together, these results highlight a role for Penk1 in the regulation of the response of the bone to mechanical unloading, potentially acting on osteoblast differentiation and activity in a cell-autonomous manner.

The BALB/c.mdx62 mouse exhibits a dystrophic muscle pathology and is a model of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a devastating monogenic skeletal muscle-wasting disorder. Although many pharmacological and genetic interventions have been reported in preclinical studies, few have progressed to clinical trials with meaningful benefit. Identifying therapeutic potential can be limited by availability of suitable preclinical mouse models. More rigorous testing across models with varied background strains and mutations can identify treatments for clinical success. Here, we report the generation of a DMD mouse model with a CRISPR-induced deletion within exon 62 of the dystrophin gene (Dmd) and the first generated in BALB/c mice. Analysis of mice at 3, 6 and 12 months of age confirmed loss of expression of the dystrophin protein isoform Dp427 and resultant dystrophic pathology in limb muscles and the diaphragm, with evidence of centrally nucleated fibers, increased inflammatory markers and fibrosis, progressive decline in muscle function, and compromised trabecular bone development. The BALB/c.mdx62 mouse is a novel model of DMD with associated variations in the immune response and muscle phenotype, compared with those of existing models. It represents an important addition to the preclinical model toolbox for developing therapeutic strategies.

The role of adipokines in osteoporosis management: a mini review

The prevalence of osteoporosis has been on the rise globally. With ageing populations, research has sought therapeutic solutions in novel areas. One such area is that of the adipokines. Current literature points to an important role for these chemical mediators in relation to bone metabolism. Well-established adipokines have been broadly reported upon. These include adiponectin and leptin. However, other novel adipokines such as visfatin, nesfatin-1, meteorin-like protein (Metrnl), apelin and lipocalin-2 are starting to be addressed pre-clinically and clinically. Adipokines hold pro-inflammatory and anti-inflammatory properties that influence the pathophysiology of various bone diseases. Omentin-1 and vaspin, two novel adipokines, share cardioprotective effects and play essential roles in bone metabolism. Studies have reported bone-protective effects of omentin-1, whilst others report negative associations between omentin-1 and bone mineral density. Lipocalin-2 is linked to poor bone microarchitecture in mice and is even suggested to mediate osteoporosis development from prolonged disuse. Nesfatin-1, an anorexigenic adipokine, has been known to preserve bone density. Animal studies have demonstrated that nesfatin-1 treatment limits bone loss and increases bone strength, suggesting exogenous use as a potential treatment for osteopenic disorders. Pre-clinical studies have shown adipokine apelin to have a role in bone metabolism, mediated by the enhancement of osteoblast genesis and the inhibition of programmed cell death. Although many investigations have reported conflicting findings, sufficient literature supports the notion that adipokines have a significant influence on the metabolism of bone. This review aims at highlighting the role of novel adipokines in osteoporosis while also discussing their potential for treating osteoporosis.

Transcriptional dysregulation of autophagy in the muscle of a mouse model of Duchenne muscular dystrophy

It has been reported that autophagic activity is disturbed in the skeletal muscles of dystrophin-deficient mdx mice and patients with Duchenne muscular dystrophy (DMD). Transcriptional regulations of autophagy by FoxO transcription factors (FoxOs) and transcription factor EB (TFEB) play critical roles in adaptation to cellular stress conditions. Here, we investigated whether autophagic activity is dysregulated at the transcription level in dystrophin-deficient muscles. Expression levels of autophagy-related genes were globally decreased in tibialis anterior and soleus muscles of mdx mice compared with those of wild-type mice. DNA microarray data from the NCBI database also showed that genes related to autophagy were globally downregulated in muscles from patients with DMD. These downregulated genes are known as targets of FoxOs and TFEB. Immunostaining showed that nuclear localization of FoxO1 and FoxO3a was decreased in mdx mice. Western blot analyses demonstrated increases in phosphorylation levels of FoxO1 and FoxO3a in mdx mice. Nuclear localization of TFEB was also reduced in mdx mice, which was associated with elevated phosphorylation levels of TFEB. Collectively, the results suggest that autophagy is disturbed in dystrophin-deficient muscles via transcriptional downregulation due to phosphorylation-mediated suppression of FoxOs and TFEB.

Biological sex divergence in transcriptomic profiles during the onset of hindlimb unloading-induced atrophy

Disuse-induced muscle atrophy is a common clinical problem observed mainly in older adults, intensive care units patients, or astronauts. Previous studies presented biological sex divergence in progression of disuse-induced atrophy along with differential changes in molecular mechanisms possibly underlying muscle atrophy. The aim of this study was to perform transcriptomic profiling of male and female mice during the onset and progression of unloading disuse-induced atrophy. Male and female mice underwent hindlimb unloading (HU) for 24, 48, 72, and 168 h (n = 8/group). Muscles were weighed for each cohort and gastrocnemius was used for RNA-sequencing analysis. Females exhibited muscle loss as early as 24 h of HU, whereas males after 168 h of HU. In males, pathways related to proteasome degradation were upregulated throughout 168 h of HU, whereas in females these pathways were upregulated up to 72 h of HU. Lcn2, a gene contributing to regulation of myogenesis, was upregulated by 6.46- to 19.86-fold across all time points in females only. A reverse expression of Fosb, a gene related to muscle degeneration, was observed between males (4.27-fold up) and females (4.57-fold down) at 24-h HU. Mitochondrial pathways related to tricarboxylic acid (TCA) cycle were highly downregulated at 168 h of HU in males, whereas in females this downregulation was less pronounced. Collagen-related pathways were consistently downregulated throughout 168 h of HU only in females, suggesting a potential biological sex-specific protective mechanism against disuse-induced fibrosis. In conclusion, females may have protection against HU-induced skeletal muscle mitochondrial degeneration and fibrosis through transcriptional mechanisms, although they may be more vulnerable to HU-induced muscle wasting compared with males.NEW & NOTEWORTHY Herein, we have assessed the transcriptomic response across biological sexes during the onset and progression of unloading disuse-induced atrophy in mice. We have demonstrated an inverse expression of Fosb between males and females, as well as differentially timed patterns of expressing atrophy-related pathways between sexes that are concomitant to the accelerated atrophy in females. We also identified in females signs of mechanisms to combat disuse-induced mitochondrial degeneration and fibrosis.

Bone and Cartilage Biology

Recent technical and conceptual advances in molecular and cellular biology have dramatically advanced bone and cartilage biology [...]

Adipokines as targets in musculoskeletal immune and inflammatory diseases

Adipokines are the principal mediators in adipose signaling. Nevertheless, besides their role in energy storage, these molecules can be produced by other cells, such as immune cells or chondrocytes. Given their pleiotropic effects, research over the past few years has also focused on musculoskeletal diseases, showing that these adipokines might have relevant roles in worsening the disease or improving the treatment response. In this review, we summarize recent advances in our understanding of adipokines and their role in the most prevalent musculoskeletal immune and inflammatory disorders.

HistoEnder: A 3D printer-based histological slide autostainer that retains 3D printer functions

Automated microscope slide stainers are usually very expensive and unless the laboratory performs heavy histological work it is difficult to justify buying a 2000-10000€ machine. As a result, histology and pathology labs around the world lose thousands of working hours for following procedures that could be easily automated. Herein, we propose a simple modification of an open-source 3D printer, the Creality Ender-3, into an automated microscope slide autostainer, the HistoEnder. The HistoEnder is cheap (less than 200€), modular, and easy to set up, with only two 3D-printed parts needed. Additionally, the 3D printer retains its full functionality, and it can be reverted back into 3D printing in less than 1 min. The g-code associated with the procedure is extremely simple, and can be written by anyone. The HistoEnder can also be used in chemistry and material science laboratories for automating surface modifications and dip coating.

Lipocalin-2: a novel link between the injured kidney and the bone

PURPOSE OF REVIEW

Fibroblast growth factor 23 (FGF23) excess is associated with left ventricular hypertrophy (LVH) and early mortality in patients with chronic kidney disease (CKD) and in animal models. Elevated Lipocalin-2 (LCN2), produced by the injured kidneys, contributes to CKD progression and might aggravate cardiovascular outcomes. The current review aims to highlight the role of LCN2 in CKD, particularly its interactions with FGF23.

RECENT FINDINGS

Inflammation, disordered iron homeostasis and altered metabolic activity are common complications of CKD, and are associated with elevated levels of kidney-produced LCN2 and bone-secreted FGF23. A recent study shows that elevated LCN2 increases FGF23 production, and contributes to cardiac injury in patients and animals with CKD, whereas LCN2 reduction in mice with CKD reduces FGF23, improves cardiovascular outcomes and prolongs lifespan.

SUMMARY

In this manuscript, we discuss the potential pathophysiological functions of LCN2 as a major kidney-bone crosstalk molecule, linking the progressive decline in kidney function to excessive bone FGF23 production. We also review associations of LCN2 with kidney, cardiovascular and bone and mineral alterations. We conclude that the presented data support the design of novel therapeutic approaches to improve outcomes in CKD.