Meta-analysis Integrated With Multi-omics Data Analysis to Elucidate Pathogenic Mechanisms of Age-Related Knee Osteoarthritis in Mice

The intersection of aging and estrogen in osteoarthritis

Osteoarthritis (OA) is a chronic joint disease characterized by cartilage degradation, inflammation, and pain. While multiple factors contribute to OA development, age and sex are primary risk factors, particularly affecting postmenopausal women. The dramatic increase in OA risk after menopause suggests estrogen deficiency accelerates disease progression. This review explores the molecular mechanisms connecting aging and estrogen deficiency in OA development, focusing on key genes and pathways identified through RNA sequencing.

Progress in multi-omics studies of osteoarthritis

Osteoarthritis (OA), a ubiquitous degenerative joint disorder, is marked by pain and disability, profoundly impacting patients' quality of life. As the population ages, the global prevalence of OA is escalating. Omics technologies have become instrumental in investigating complex diseases like OA, offering comprehensive insights into its pathogenesis and progression by uncovering disease-specific alterations across genomics, transcriptomics, proteomics, and metabolomics levels. In this review, we systematically analyzed and summarized the application and recent achievements of omics technologies in OA research by scouring relevant literature in databases such as PubMed. These studies have shed light on new potential therapeutic targets and biomarkers, charting fresh avenues for OA diagnosis and treatment. Furthermore, in our discussion, we highlighted the immense potential of spatial omics technologies in unraveling the molecular mechanisms of OA and in the development of novel therapeutic strategies, proposing future research directions and challenges. Collectively, this study encapsulates the pivotal advances in current OA research and prospects for future investigation, providing invaluable references for a deeper understanding and treatment of OA. This review aims to synthesize the recent progress of omics technologies in the realm of OA, aspiring to furnish theoretical foundations and research orientations for more profound studies of OA in the future.

Sex Differences in Ambulatory Biomechanics: A Meta-Analysis Providing a Mechanistic Insight into Knee Osteoarthritis

PURPOSE

Females typically present with a higher prevalence of knee osteoarthritis (KOA), and such a higher prevalence may be due to unique knee biomechanics during walking. However, the sex-dependent ambulatory mechanics has been yet to be clarified. To address this critical knowledge gap, this study implemented a series of computational approaches 1) to identify sex-related knee joint biomechanics during ambulation in persons with KOA and 2) to compare these biomechanical measures between individuals with versus without KOA, stratified by sex.

METHODS

We searched five electronic databases for studies reporting sex-specific knee biomechanics in persons with and/or without KOA. Summary estimates were computed using random-effects meta-analysis and stratified by sex.

RESULTS

The systematic review identified 18 studies (308 males and 383 females with KOA; 740 males and 995 females without KOA). A series of meta-analyses identified female-specific knee biomechanics in a disease-dependent manner. Females with KOA had lower first peak knee adduction moment and peak knee adduction compared with male counterparts. On the other hand, healthy females had lower peak knee flexion moment than male counterparts. Effect estimate in each meta-analysis displayed poor quality of evidence according to the GRADE approach.

CONCLUSIONS

The current study is the first to consider sex as a biological variable into ambulatory mechanics in the development of KOA. We discovered that sex-dependent alterations in knee biomechanics is a function of the presence of KOA, indicating that KOA disease may be a driver of the sex-dependent biomechanical alterations or vice versa. Although no strong conclusion can be drawn because of the low quality of evidence, these findings provide new insight into the sex differences in ambulatory knee biomechanics and progression of KOA.

Menopause-induced 17β-estradiol and progesterone loss increases senescence markers, matrix disassembly and degeneration in mouse cartilage

Female individuals who are post-menopausal present with higher incidence of knee osteoarthritis (KOA) than male counterparts; however, the mechanisms underlying this disparity are unknown. The most commonly used preclinical models lack human-relevant menopausal phenotypes, which may contribute to our incomplete understanding of sex-specific differences in KOA pathogenesis. Here we chemically induced menopause in middle-aged (14-16 months) C57/BL6N female mice. When we mapped the trajectory of KOA over time, we found that menopause aggravated cartilage degeneration relative to non-menopause controls. Network medicine analyses revealed that loss of 17β-estradiol and progesterone with menopause enhanced susceptibility to senescence and extracellular matrix disassembly. In vivo, restoration of 17β-estradiol and progesterone in menopausal mice protected against cartilage degeneration compared to untreated menopausal controls. Accordingly, post-menopausal human chondrocytes displayed decreased markers of senescence and increased markers of chondrogenicity when cultured with 17β-estradiol and progesterone. These findings implicate menopause-associated senescence and extracellular matrix disassembly in the sex-specific pathogenesis of KOA.

Geroscience and pathology: a new frontier in understanding age-related diseases

Geroscience, a burgeoning discipline at the intersection of aging and disease, aims to unravel the intricate relationship between the aging process and pathogenesis of age-related diseases. This paper explores the pivotal role played by geroscience in reshaping our understanding of pathology, with a particular focus on age-related diseases. These diseases, spanning cardiovascular and cerebrovascular disorders, malignancies, and neurodegenerative conditions, significantly contribute to the morbidity and mortality of older individuals. We delve into the fundamental cellular and molecular mechanisms underpinning aging, including mitochondrial dysfunction and cellular senescence, and elucidate their profound implications for the pathogenesis of various age-related diseases. Emphasis is placed on the importance of assessing key biomarkers of aging and biological age within the realm of pathology. We also scrutinize the interplay between cellular senescence and cancer biology as a central area of focus, underscoring its paramount significance in contemporary pathological research. Moreover, we shed light on the integration of anti-aging interventions that target fundamental aging processes, such as senolytics, mitochondria-targeted treatments, and interventions that influence epigenetic regulation within the domain of pathology research. In conclusion, the integration of geroscience concepts into pathological research heralds a transformative paradigm shift in our understanding of disease pathogenesis and promises breakthroughs in disease prevention and treatment.

Network-based cytokine inference implicates Oncostatin M as a driver of an inflammation phenotype in knee osteoarthritis

Inflammatory cytokines released by synovium after trauma disturb the gene regulatory network and have been implicated in the pathophysiology of osteoarthritis. A mechanistic understanding of how aging perturbs this process can help identify novel interventions. Here, we introduced network paradigms to simulate cytokine-mediated pathological communication between the synovium and cartilage. Cartilage-specific network analysis of injured young and aged murine knees revealed aberrant matrix remodeling as a transcriptomic response unique to aged knees displaying accelerated cartilage degradation. Next, network-based cytokine inference with pharmacological manipulation uncovered IL6 family member, Oncostatin M (OSM), as a driver of the aberrant matrix remodeling. By implementing a phenotypic drug discovery approach, we identified that the activation of OSM recapitulated an "inflammatory" phenotype of knee osteoarthritis and highlighted high-value targets for drug development and repurposing. These findings offer translational opportunities targeting the inflammation-driven osteoarthritis phenotype.

How is Big Data reshaping preclinical aging research?

The exponential scientific and technological progress during the past 30 years has favored the comprehensive characterization of aging processes with their multivariate nature, leading to the advent of Big Data in preclinical aging research. Spanning from molecular omics to organism-level deep phenotyping, Big Data demands large computational resources for storage and analysis, as well as new analytical tools and conceptual frameworks to gain novel insights leading to discovery. Systems biology has emerged as a paradigm that utilizes Big Data to gain insightful information enabling a better understanding of living organisms, visualized as multilayered networks of interacting molecules, cells, tissues and organs at different spatiotemporal scales. In this framework, where aging, health and disease represent emergent states from an evolving dynamic complex system, context given by, for example, strain, sex and feeding times, becomes paramount for defining the biological trajectory of an organism. Using bioinformatics and artificial intelligence, the systems biology approach is leading to remarkable advances in our understanding of the underlying mechanism of aging biology and assisting in creative experimental study designs in animal models. Future in-depth knowledge acquisition will depend on the ability to fully integrate information from different spatiotemporal scales in organisms, which will probably require the adoption of theories and methods from the field of complex systems. Here we review state-of-the-art approaches in preclinical research, with a focus on rodent models, that are leading to conceptual and/or technical advances in leveraging Big Data to understand basic aging biology and its full translational potential.

Uncovering the "riddle of femininity" in osteoarthritis: a systematic review and meta-analysis of menopausal animal models and mathematical modeling of estrogen treatment

OBJECTIVE

Post-menopausal women are disproportionately affected by osteoarthritis (OA). As such, the purpose of this study was to (1) summarize the state-of-the-science aimed at understanding the effects of menopause on OA in animal models and (2) investigate how dosage and timing of initiation of estrogen treatment affect cartilage degeneration.

DESIGN

A systematic review identified articles studying menopausal effects on cartilage in preclinical models. A meta-analysis was performed using overlapping cartilage outcomes in conjunction with a rigor and reproducibility analysis. Ordinary differential equation models were used to determine if a relationship exists between cartilage degeneration and the timing of initiation or dosage of estrogen treatment.

RESULTS

Thirty-eight manuscripts were eligible for inclusion. The most common menopause model used was ovariectomy (92%), and most animals were young at the time of menopause induction (86%). Most studies did not report inclusion criteria, animal monitoring, protocol registration, or data accessibility. Cartilage outcomes were worse in post-menopausal animals compared to age-matched, non-menopausal animals, as evidenced by cartilage histological scoring [0.75, 1.72], cartilage thickness [-4.96, -0.96], type II collagen [-4.87, -0.56], and c-terminal cross-linked telopeptide of type II collagen (CTX-II) [2.43, 5.79] (95% CI of Effect Size (+greater in menopause, -greater in non-menopause)). Moreover, modeling suggests that cartilage health may be improved with early initiation and higher doses of estrogen treatment.

CONCLUSIONS

To improve translatability, animal models that consider aging and natural menopause should be utilized, and more attention to rigor and reproducibility is needed. Timing of initiation and dosage may be important factors modulating therapeutic effects of estrogen on cartilage.

Age-related matrix stiffening epigenetically regulates α-Klotho expression and compromises chondrocyte integrity

Extracellular matrix stiffening is a quintessential feature of cartilage aging, a leading cause of knee osteoarthritis. Yet, the downstream molecular and cellular consequences of age-related biophysical alterations are poorly understood. Here, we show that epigenetic regulation of α-Klotho represents a novel mechanosensitive mechanism by which the aged extracellular matrix influences chondrocyte physiology. Using mass spectrometry proteomics followed by a series of genetic and pharmacological manipulations, we discovered that increased matrix stiffness drove Klotho promoter methylation, downregulated Klotho gene expression, and accelerated chondrocyte senescence in vitro. In contrast, exposing aged chondrocytes to a soft matrix restored a more youthful phenotype in vitro and enhanced cartilage integrity in vivo. Our findings demonstrate that age-related alterations in extracellular matrix biophysical properties initiate pathogenic mechanotransductive signaling that promotes Klotho promoter methylation and compromises cellular health. These findings are likely to have broad implications even beyond cartilage for the field of aging research.

Osteoarthritis gene therapy in 2022

PURPOSE OF REVIEW

To assess the present status of gene therapy for osteoarthritis (OA).

RECENT FINDINGS

An expanding list of cDNAs show therapeutic activity when introduced into the joints of animals with experimental models of OA. In vivo delivery with adenovirus or adeno-associated virus is most commonly used for this purpose. The list of encoded products includes cytokines, cytokine antagonists, enzymes, enzyme inhibitors, growth factors and noncoding RNA. Elements of CRISPR-Cas have also been delivered to mouse knees to ablate key genes. Several human trials have been initiated, using transgenes encoding transforming growth factor-β1, interleukin-1 receptor antagonist, interferon-β, the NKX3.2 transcription factor or variant interleukin-10. The first of these, using ex vivo delivery with allogeneic chondrocytes, gained approval in Korea which was subsequently retracted. However, it is undergoing Phase III clinical trials in the United States. The other trials are in Phase I or II. No gene therapy for OA has current marketing approval in any jurisdiction.

SUMMARY

Extensive preclinical data support the use of intra-articular gene therapy for treating OA. Translation is beginning to accelerate and six gene therapeutics are in clinical trials. Importantly, venture capital has begun to flow and at least seven companies are developing products. Significant progress in the future can be expected.