Immunometabolism of macrophages regulates skeletal muscle regeneration

Effect of aging, endurance training, and denervation on innate immune signaling in skeletal muscle

Skeletal muscle function relies on mitochondria for energy and for mediating its unique adaptive plasticity. The NLRP3 inflammasome complex is an innate immune mechanism that responds to mitochondrial damage-associated molecular patterns (DAMPs); however, its activity relative to mitochondrial dysfunction in muscle requires exploration. The purpose of this study was to characterize immune signaling and mitochondrial function in muscle during aging, endurance training, and disuse induced by denervation. Denervation led to decreases in muscle mass, mitochondrial content, and impaired respiration. Protein analyses revealed increases in NF-κB p65 and downstream inflammatory markers, including NLRP3, caspase-1, GSDMD-N, STING, and IL-1β, along with pro-apoptotic BAX and AIF. When assessing potential DAMPS, denervation led to increased ROS production but no changes in cytosolic mtDNA levels, relative to total mtDNA. Since we hypothesized that inflammasome activation would be increased with age, we studied young (6-8 mo) and aged (21-22 mo) mice that remained sedentary or underwent a 6-wk voluntary running protocol. Aging resulted in marked increases in the expression of multiple pro-inflammatory and pro-apoptotic proteins. Remarkably, training uniformly attenuated age-related increases in BAX, NLRP3, caspase-1, STING, and gasdermin-D (GSDMD) protein expression and tended to reduce the elevated level of cytosolic mtDNA evident in aged muscle. Training adaptations were also evident in the aged animals by the preservation of muscle mass and improvements in oxygen consumption and endurance performance, and were achieved despite a lower training distance than in young animals. Our results strongly implicate endurance training as a promising therapeutic for combating disuse and age-related inflammation in skeletal muscle.NEW & NOTEWORTHY This study aims to further elucidate the role between skeletal muscle activity, mitochondria, and innate immune signaling, specifically looking at the NLRP3 inflammasome complex. Our results demonstrate that disuse conditions such as aging and denervation were associated with a pro-inflammatory phenotype and impairments in mitochondrial functioning, whereas chronic endurance training demonstrated anti-inflammatory effects. Notably, this work highlights the benefits of exercise in attenuating age-related inflammation in aged skeletal muscle.

Muscle-specific acellular ECM fibers made with anchored cell sheet engineering support regeneration in rat models of volumetric muscle loss

Volumetric muscle loss (VML), a condition affecting millions due to trauma, represents a critical unmet need in regenerative medicine, with no established standard of care. This study introduces a de novo therapeutic strategy using tissue-specific skeletal muscle acellular extracellular matrix (aECM) fibers fabricated using scaffold-free Anchored Cell Sheet Engineering technique. These engineered fibers replicate the native ECM composition and microarchitecture of skeletal muscle, incorporating essential structural and basement membrane proteins. In a rat VML model, aECM demonstrated promising regenerative capacity compared to commercial porcine-derived small intestine submucosa (SIS) ECM. Over an 8-week period, compared to contralateral muscle, aECM preserved muscle volume and weight, regulated inflammatory and fibrotic responses, and promoted vascularization. In contrast, SIS was rapidly degraded by week 4 and associated with fibrosis. Force recovery in aECM was lower at the 8-week time point (77 % compared to 91 % in control), but histological and immunohistochemical analyses revealed newly formed, dispersed muscle fibers exclusively in aECM treatment. Importantly, muscle weight was preserved only when aECM was used, resulting in similar normalized force-to-weight across all groups (87 % in aECM vs. 88 % in SIS). The histological analyses further demonstrated ongoing tissue remodeling, indicative of sustained regeneration, in contrast to the premature fibrotic healing observed in the other groups. An innovative quantitative image analysis workflow enabled assessment of spatial tissue heterogeneity through histology and immunohistochemistry images, setting a new standard for regeneration analysis. These findings establish engineered tissue-specific aECM as a transformative approach for VML treatment, laying the groundwork for translation to clinical applications. STATEMENT OF SIGNIFICANCE: The current study introduces a transformative approach to treating volumetric muscle loss (VML) through the development of tissue-specific acellular extracellular matrix (aECM) fibers engineered using a scaffold-free biofabrication platform uniquely suited for recreation of such aECM components. The engineered fibers represent a significant advancement over current commercial options by recreating native ECM composition and microarchitecture while eliminating complications associated with xenogenic materials. Through comprehensive in vivo evaluation in a rat model, it is demonstrated that these engineered fibers maintain muscle mass and promote controlled tissue regeneration, addressing key limitations of existing treatments. The scaffold-free biofabrication of tissue-specific aECM provides a new paradigm for biomaterial design in regenerative medicine.

Electrospun Silk Fibroin-Silk Sericin Scaffolds Induced Macrophage Polarization and Vascularization for Volumetric Muscle Loss Injury

Volumetric muscle loss (VML) results in the impediment of skeletal muscle function. Tissue engineering scaffolds have been widely developed and used in skeletal muscle regeneration. However, scaffold implantation causes an immune response that endogenously regulates implant integration and tissue regeneration. Moreover, vascularization is thought to be a principal obstacle in the reconstruction of skeletal muscle defects. Thus, creating a pro-regenerative microenvironment that facilitates muscle regeneration and supports angiogenesis represents a promising strategy for tissue repair following volumetric muscle loss (VML) injury. Previously, the electrospun silk fibroin-silk sericin (SF-SS) film could regulate macrophage polarization and promote neovessel formation. This study aimed to investigate if the electrospun SF-SS scaffold was capable of supporting functional muscle regeneration. The results indicate that the conditioned medium collected from macrophages co-cultured with the 7:3 SF-SS scaffold significantly enhanced the proliferation and migration of myoblast C2C12 cells and improved the tube formation of HUVECs. Data from animal studies showed that the 7:3 SF-SS scaffold significantly enhanced M2 macrophage polarization, vascularization, and muscle fiber regeneration, reduced fibrosis, and improved muscle function after VML injury, thereby promoting the repair of muscle tissue. Therefore, the 7:3 SF-SS scaffold might represent a potential candidate for skeletal muscle regeneration following VML injury.

Macrophage immunometabolism: emerging targets for regrowth in aging muscle

The recovery from muscle atrophy is impaired with aging as characterized by improper muscle remodeling and sustained functional deficits. Age-related deficits in muscle regrowth are tightly linked with the loss of early pro-inflammatory macrophage responses and subsequent cellular dysregulation within the skeletal muscle niche. Macrophage inflammatory phenotype is regulated at the metabolic level, highlighting immunometabolism as an emerging strategy to enhance macrophage responses and restore functional muscle regrowth. Accordingly, metabolic targets with an emphasis on glycolytic, hypoxia, and redox-related pathways stand out for their role in promoting macrophage inflammation and enhancing muscle regrowth in aging. Here we highlight promising immuno-metabolic targets that could be leveraged to restore optimal pro-inflammatory macrophage function in aging and enhance muscle regrowth following muscular atrophy.

Regenerative Functions of Regulatory T Cells and Current Strategies Utilizing Mesenchymal Stem Cells in Immunomodulatory Tissue Regeneration

BACKGROUND

Regulatory T cells (Tregs) are essential for maintaining immune homeostasis and facilitating tissue regeneration by fostering an environment conducive to tissue repair. However, in damaged tissues, excessive inflammatory responses can overwhelm the immunomodulatory capacity of Tregs, compromising their functionality and potentially hindering effective regeneration. Mesenchymal stem cells (MSCs) play a key role in enhancing Treg function. MSCs enhance Treg activity through indirect interactions, such as cytokine secretion, and direct interactions via membrane proteins.

METHODS

This review examines the regenerative functions of Tregs across various tissues, including bone, cartilage, muscle, and skin, and explores strategies to enhance Treg functionality using MSCs. Advanced techniques, such as the overexpression of relevant genes in MSCs, are highlighted for their potential to further enhance Treg function. Additionally, emerging technologies utilizing extracellular vesicles (EVs) and cell membrane-derived vesicles derived from MSCs offer promising alternatives to circumvent the potential side effects associated with live cell therapies. This review proposes approaches to enhance Treg function and promote tissue regeneration and also outlines future research directions.

RESULTS AND CONCLUSION

This review elucidates recent technological advancements aimed at enhancing Treg function using MSCs and examines their potential to improve tissue regeneration efficiency.

Impacts of osteosarcopenia on musculoskeletal health, risks of falls and fractures, and activities of daily living among population aged 50 and above: an age- and sex-matched cross-sectional analysis

AIMS

We conducted this study to investigate the impact of muscle loss on musculoskeletal health, fall and fracture risks, and activities of daily living (ADL) in elderly patients with osteoporosis.

MATERIALS AND METHODS

This age- and sex-matched cross-sectional study analyzed data from a medical center involving patients aged ≥ 50 from 2020 to 2022. The included participants were formed into three groups: 100 with osteoporosis only, 100 with osteosarcopenia, and 50 control individuals without osteoporosis and sarcopenia. We compared groups based on their baseline characteristics, bone and muscle health measurements, and the risks of falls and fractures using the STRATIFY scale and FRAX, respectively. Additionally, ADL was assessed using the Barthel Index. A multivariate analysis was performed to identify factors associated with declined ADL in osteosarcopenic patients.

RESULTS

The mean age was 76.17 years, and 82% were female. The osteosarcopenic group demonstrated poorer bone and muscle quality and quantity, with greater risks of major osteoporotic-related fractures, hip fractures, and falls, as well as significantly decreased ADL than other groups. When comparing sexes, females exhibited worse performance than males across groups. Slow gait speed and high STRATIFY score are independent predictors of declined ADL in osteosarcopenic patients.

CONCLUSION

Sarcopenia exacerbates osteoporotic patients, particularly women, worsening bone deterioration, increasing fall and fracture risks, and significantly impairing daily activities. Enhancing walking speed and reducing fall risk can boost independence in individuals with osteosarcopenia. Early detection, proper management, and preventive measures are essential for mitigating these adverse outcomes in high-risk individuals.

Cross-Species Studies Reveal That Dysregulated Mitochondrial Gene Expression and Electron Transport Complex I Activity Are Crucial for Sarcopenia

The significance of complex I of the electron transport chain (ETC) in the aging process is widely acknowledged; however, its specific impact on the development of sarcopenia in muscle remains poorly understood. This study elucidated the correlation between complex I inhibition and sarcopenia by conducting a comparative analysis of skeletal muscle gene expression in sarcopenia phenotypes from rats, mice, and humans. Our findings reveal a common mechanistic link across species, particularly highlighting the correlation between the suppression of complex I of ETC activity and dysregulated mitochondrial transcription and translation in sarcopenia phenotypes. Additionally, we observed macrophage dysfunction alongside abnormal metabolic processes within skeletal muscle tissues across all species, implicating their pathogenic role in the onset of sarcopenia. These discoveries underscore the importance of understanding the shared mechanisms associated with complex I of ETC in sarcopenia development. The identified correlations provide valuable insights into potential targets for therapeutic interventions aimed at mitigating the impact of sarcopenia, a condition with substantial implications for aging populations.

A comprehensive single-cell RNA transcriptomic analysis identifies a unique SPP1+ macrophages subgroup in aging skeletal muscle

Senescence of skeletal muscle (SkM) has been a primary contributor to senior weakness and disability in recent years. The gradually declining SkM function associated with senescence has recently been connected to an imbalance between damage and repair. Macrophages (Mac) are involved in SkM aging, and different macrophage subgroups hold different biological functions. Through comprehensive single-cell transcriptomic analysis, we first compared the metabolic pathways and biological functions of different types of cells in young (Y) and old (O) mice SkM. Strikingly, the Mac population in mice SkM was also explored, and we identified a unique Mac subgroup in O SkM characterized by highly expressed SPP1 with strong senescence and adipogenesis features. Further work was carried out on the metabolic and biological processes for these Mac subgroups. Besides, we verified that the proportion of the SPP1+ Mac was increased significantly in the quadriceps tissues of O mice, and the senotherapeutic drug combination dasatinib + quercetin (D + Q) could dramatically reduce its proportion. Our study provides novel insight into the potential role of SPP1+ Mac in SkM, which may serve as a senotherapeutic target in SkM aging.

Harnessing immunomodulation to combat sarcopenia: current insights and possible approaches

Sarcopenia is a complex age-associated syndrome of progressive loss of muscle mass and strength. Although this condition is influenced by many factors, age-related changes in immune function including immune cell dynamics, and chronic inflammation contribute to its progression. The complex interplay between the immune system, gut-muscle axis, and autophagy further underscores their important roles in sarcopenia pathogenesis. Immunomodulation has emerged as a promising strategy to counteract sarcopenia. Traditional management approaches to treat sarcopenia including physical exercise and nutritional supplementation, and the emerging technologies of biophysical stimulation demonstrated the importance of immunomodulation and regulation of macrophages and T cells and reduction of chronic inflammation. Treatments to alleviate low-grade inflammation in older adults by modulating gut microbial composition and diversity further combat sarcopenia. Furthermore, some pharmacological interventions, nano-medicine, and cell therapies targeting muscle, gut microbiota, or autophagy present additional avenues for immunomodulation in sarcopenia. This narrative review explores the immunological underpinnings of sarcopenia, elucidating the relationship between the immune system and muscle during ageing. Additionally, the review discusses new areas such as the gut-muscle axis and autophagy, which bridge immune system function and muscle health. Insights into current and potential approaches for sarcopenia management through modulation of the immune system are provided, along with suggestions for future research directions and therapeutic strategies. We aim to guide further investigation into clinical immunological biomarkers and identify indicators for sarcopenia diagnosis and potential treatment targets to combat this condition. We also aim to draw attention to the importance of considering immunomodulation in the clinical management of sarcopenia.

The Categorization of Perinatal Derivatives for Orthopedic Applications

Musculoskeletal (MSK) pathology encompasses an array of conditions that can cause anything from mild discomfort to permanent injury. Their prevalence and impact on disability have sparked interest in more effective treatments, particularly within orthopedics. As a result, the human placenta has come into focus within regenerative medicine as a perinatal derivative (PnD). These biologics are sourced from components of the placenta, each possessing a unique composition of collagens, proteins, and factors believed to aid in healing and regeneration. This review aims to explore the current literature on PnD biologics and their potential benefits for treating various MSK pathologies. We delve into different types of PnDs and their healing effects on muscles, tendons, bones, cartilage, ligaments, and nerves. Our discussions highlight the crucial role of immune modulation in the healing process for each condition. PnDs have been observed to influence the balance between anti- and pro-inflammatory factors and, in some cases, act as biologic scaffolds for tissue growth. Additionally, we assess the range of PnDs available, while also addressing gaps in our understanding, particularly regarding biologic processing methods. Although certain PnD biologics have varying levels of support in orthopedic literature, further clinical investigations are necessary to fully evaluate their impact on human patients.

Bioactive Nanofiber-Hydrogel Composite Regulates Regenerative Microenvironment for Skeletal Muscle Regeneration after Volumetric Muscle Loss

Volumetric muscle loss (VML) is a severe form of muscle trauma that exceeds the regenerative capacity of skeletal muscle tissue, leading to substantial functional impairment. The abnormal immune response and excessive reactive oxygen species (ROS) accumulation hinder muscle regeneration following VML. Here, an interfacial cross-linked hydrogel-poly(ε-caprolactone) nanofiber composite, that incorporates both biophysical and biochemical cues to modulate the immune and ROS microenvironment for enhanced VML repair, is engineered. The interfacial cross-linking is achieved through a Michael addition between catechol and thiol groups. The resultant composite exhibits enhanced mechanical strength without sacrificing porosity. Moreover, it mitigates oxidative stress and promotes macrophage polarization toward a pro-regenerative phenotype, both in vitro and in a mouse VML model. 4 weeks post-implantation, mice implanted with the composite show improved grip strength and walking performance, along with increased muscle fiber diameter, enhanced angiogenesis, and more nerve innervation compared to control mice. Collectively, these results suggest that the interfacial cross-linked nanofiber-hydrogel composite could serve as a cell-free and drug-free strategy for augmenting muscle regeneration by modulating the oxidative stress and immune microenvironment at the VML site.

Ambient air pollution exposure and the risk of probable sarcopenia: A prospective cohort study

BACKGROUND

Sarcopenia is characterized by decreased muscle mass and strength, posing threat to quality of life. Air pollutants are increasingly recognized as risk factors for diseases, while the relationship between the two remains to be elucidated. This study investigated whether exposure to ambient air pollution contributes to the development of sarcopenia.

METHODS

We employed the data from the UK Biobank with 303,031 eligible participants. Concentrations of PM2·5, NO2, and NOx were estimated. Cox proportional hazard regression models were applied to investigate the associations between pollutants and sarcopenia.

RESULTS

30,766 probable sarcopenia cases was identified during the follow-up. We observed that exposure to PM2.5 (HR, 1.232; 95% CI, 1.053-1.440), NO2 (HR, 1.055; 95% CI, 1.032-1.078) and NOx (HR, 1.016; 95% CI, 1.007-1.026) were all significantly associated with increased risk for probable sarcopenia for each 10 μg/m3 increase in pollutant concentration. In comparison with individuals in the lowest quartiles of exposure, those in the upper quartiles had significantly increased risk of probable sarcopenia. Sarcopenia-related factors, e.g., reduced lean muscle mass, diminished walking pace, and elevated muscle fat infiltration ratio, also exhibited positive associations with exposure to ambient air pollution. On the contrary, high level physical activity significantly mitigated the influence of air pollutants on the development of probable sarcopenia.

CONCLUSIONS

Air pollution exposure elevated the risk of developing sarcopenia and related manifestations in a dose-dependent manner, while physical activity maintained protective under this circumstance. Efforts should be made to control air pollution and emphasize the importance of physical activity for skeletal muscle health under this circumstance.

Modulation of experimental acute lung injury by exosomal miR-7704 from mesenchymal stromal cells acts through M2 macrophage polarization

Acute lung injury (ALI) is a life-threatening condition with limited treatment options. The pathogenesis of ALI involves macrophage-mediated disruption and subsequent repair of the alveolar barriers, which ultimately results in lung damage and regeneration, highlighting the pivotal role of macrophage polarization in ALI. Although exosomes derived from mesenchymal stromal cells have been established as influential modulators of macrophage polarization, the specific role of exosomal microRNAs (miRNAs) remains underexplored. This study aimed to elucidate the role of specific exosomal miRNAs in driving macrophage polarization, thereby providing a reference for developing novel therapeutic interventions for ALI. We found that miR-7704 is the most abundant and efficacious miRNA for promoting the switch to the M2 phenotype in macrophages. Mechanistically, we determined that miR-7704 stimulates M2 polarization by inhibiting the MyD88/STAT1 signaling pathway. Notably, intra-tracheal delivery of miR-7704 alone in a lipopolysaccharide-induced murine ALI model significantly drove M2 polarization in lung macrophages and remarkably restored pulmonary function, thus increasing survival. Our findings highlight miR-7704 as a valuable tool for treating ALI by driving the beneficial M2 polarization of macrophages. Our findings pave the way for deeper exploration into the therapeutic potential of exosomal miRNAs in inflammatory lung diseases.

Exercise, mitochondrial dysfunction and inflammasomes in skeletal muscle

In the broad field of inflammation, skeletal muscle is a tissue that is understudied. Yet it represents about 40% of body mass in non-obese individuals and is therefore of fundamental importance for whole body metabolism and health. This article provides an overview of the unique features of skeletal muscle tissue, as well as its adaptability to exercise. This ability to adapt, particularly with respect to mitochondrial content and function, confers a level of metabolic "protection" against energy consuming events, and adds a measure of quality control that determines the phenotypic response to stress. Thus, we describe the particular role of mitochondria in promoting inflammasome activation in skeletal muscle, contributing to muscle wasting and dysfunction in aging, disuse and metabolic disease. We will then discuss how exercise training can be anti-inflammatory, mitigating the chronic inflammation that is observed in these conditions, potentially through improvements in mitochondrial quality and function.

Macrophage SREBP1 regulates skeletal muscle regeneration

Macrophages are essential for the proper inflammatory and reparative processes that lead to regeneration of skeletal muscle after injury. Recent studies have demonstrated close links between the function of activated macrophages and their cellular metabolism. Sterol regulatory element-binding protein 1 (SREBP1) is a key regulator of lipid metabolism and has been shown to affect the activated states of macrophages. However, its role in tissue repair and regeneration is poorly understood. Here we show that systemic deletion of Srebf1, encoding SREBP1, or macrophage-specific deletion of Srebf1a, encoding SREBP1a, delays resolution of inflammation and impairs skeletal muscle regeneration after injury. Srebf1 deficiency impairs mitochondrial function in macrophages and suppresses the accumulation of macrophages at sites of muscle injury. Lipidomic analyses showed the reduction of major phospholipid species in Srebf1 -/- muscle myeloid cells. Moreover, diet supplementation with eicosapentaenoic acid restored the accumulation of macrophages and their mitochondrial gene expression and improved muscle regeneration. Collectively, our results demonstrate that SREBP1 in macrophages is essential for repair and regeneration of skeletal muscle after injury and suggest that SREBP1-mediated fatty acid metabolism and phospholipid remodeling are critical for proper macrophage function in tissue repair.

Sarcopenia, sarcopenic obesity and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD), sarcopenia and sarcopenic obesity (SO) are highly prevalent conditions that may coexist, especially in the aging population, without any approved pharmacologic treatment for all of them. There are multiple pathophysiologic mechanisms suggested to explain an association between NAFLD and sarcopenia or SO, including alterations in the adipokines, cytokines, hepatokines and myokines, which may interplay with other factors, such as aging, diet and physical inactivity. In clinical terms, most observational studies support an association between NAFLD and sarcopenia or SO; importantly, there are few cohort studies indicating higher mortality in patients with NAFLD and sarcopenia. Their association also bears some treatment considerations: for example, pioglitazone or vitamin E, suggested as off label treatment for selected patients with nonalcoholic steatohepatitis, may be recommended in the coexistence of sarcopenia or SO, since limited evidence did not show adverse effects of them on sarcopenia and abdominal obesity. In this review, evidence linking sarcopenia and SO with NAFLD is summarized, with a special focus on clinical data. A synopsis of the major pathophysiological links between NAFLD and sarcopenia/SO is initially presented, followed by selected clinical studies and, finally, treatment considerations in patients with NAFLD and sarcopenia or SO are discussed.

Unsaturated Long-Chain Fatty Acids Activate Resident Macrophages and Stem Cells in a Human Skeletal Muscle Tissue Model

Phenotypically heterogeneous populations of tissue-resident macrophages and stem cells play important roles in the regeneration of the skeletal muscle tissue. Previous studies using animal and cell culture models implied a beneficial effect of fatty acid (FA) species on tissue regeneration. Here, we applied a human experimental model using excised muscle tissues from reconstructive surgeries to study the effects of FAs on resident macrophages and stem cells in the natural environment of human skeletal muscle tissue. Muscle tissue samples from 20 donors were included in this study. The expression of 34 cytokines/chemokines was determined, using multiplex protein analysis. The phenotypes of macrophages and stem cells were determined immunohistochemically. The numbers of CD80+ macrophages correlated with the expression levels of IL-1α, IL-1RA, IL-8, IL-17A, and MCP-1, while the PAX7+ and MyoD+ stem cell counts were positively correlated with the expression level of CXCL12α, a recognized chemoattractant for muscle stem cells. Treatment of additional tissue sections with FAs revealed that CD80+ or MARCO+ macrophages- and PAX7+ or MyoD+ stem cells were simultaneously increased by unsaturated long-chain FAs. Taken together, this is the first experimental demonstration of a coordinated activation of macrophages and stem cells in human skeletal muscle tissue.

Ageing of skeletal muscle extracellular matrix and mitochondria: finding a potential link

Aim: To discuss the progress of extracellular matrix (ECM) characteristics, mitochondrial homeostasis, and their potential crosstalk in the pathogenesis of sarcopenia, a geriatric syndrome characterized by a generalized and progressive reduction in muscle mass, strength, and physical performance.Methods: This review focuses on the anatomy and physiology of skeletal muscle, alterations of ECM and mitochondria during ageing, and the role of the interplay between ECM and mitochondria in the pathogenesis of sarcopenia.Results: Emerging evidence points to a clear interplay between mitochondria and ECM in various tissues and organs. Under the ageing process, the ECM undergoes changes in composition and physical properties that may mediate mitochondrial changes via the systematic metabolism, ROS, SPARC pathway, and AMPK/PGC-1α signalling, which in turn exacerbate muscle degeneration. However, the precise effects of such crosstalk on the pathobiology of ageing, particularly in skeletal muscle, have not yet been fully understood.Conclusion: The changes in skeletal muscle ECM and mitochondria are partially responsible for the worsened muscle function during the ageing process. A deeper understanding of their alterations and interactions in sarcopenic patients can help prevent sarcopenia and improve its prognoses.