Prevalence of sarcopenia under different diagnostic criteria and the changes in muscle mass, muscle strength, and physical function with age in Chinese old adults.

BACKGROUND: At present, there are several diagnostic criteria of sarcopenia were used in China, and the diagnostic criteria were not unified. This study aims to investigate the consistency between the latest sarcopenia diagnostic criteria Asian Working Group for Sarcopenia(AWGS 2019) and other common diagnostic criteria. The changes of muscle mass, muscle strength and physical function with age and their effects on the diagnosis of sarcopenia were also analyzed. METHODS: A total of 1009 men aged ≥60 years were enrolled from multiple communities. Skeletal muscle mass index, grip strength and 6 m gait speed were measured. The consistency of AWGS 2019 with other diagnostic criteria was analyzed and the trends of these three indicators were observed. The differences of muscle mass, muscle strength and function among different diagnostic criteria and age groups were evaluated. In addition, the change trends of these three indicators with age were observed. RESULTS: According to AWGS 2019 diagnostic criteria, the incidence of sarcopenia in male aged 60-69 years, 70-79 years and over 80 years was 1.5%, 9.6% and 33.1%, respectively. AWGS 2019 was highly consistent with other diagnostic criteria (Kappa = 0.66-0.80, P < 0.01), except the Foundation for the National Institutes of Health(FNIH) (Kappa = 0.32, P < 0.01). When AWGSA2019 diagnostic criteria are applied, the prevalence of decreased muscle strength (39.1%) and physical function (46.4%) was significantly higher than that of low muscle mass (35.9%) in the men over 80 years old. Muscle strength (P < 0.01) and function (P < 0.01) decreased at the same rate with age, both of which were more significant than muscle mass (P < 0.01). CONCLUSION: AWGS 2019 was highly consistent with other criteria. Maintaining muscle mass should be the focus of attention before age 80, while improving muscle strength and function should be focused after age 80 to prevent disability.

Mapping enhancer and chromatin accessibility landscapes charts the regulatory network of Alzheimer's disease.

BACKGROUND: Enhancers are regulatory elements that target and modulate gene expression and play a role in human health and disease. However, the roles of enhancer regulatory circuit abnormalities driven by epigenetic alterations in Alzheimer's disease (AD) are unclear. METHODS: In this study, a multiomic integrative analysis was performed to map enhancer and chromatin accessibility landscapes and identify regulatory network abnormalities in AD. We identified differentially methylated enhancers and constructed regulatory networks across brain regions using AD brain tissue samples. Through the integration of snATAC-seq and snRNA-seq datasets, we mapped enhancers with DNA methylation alterations (DMA) and chromatin accessibility landscapes. Core regulatory triplets that contributed to AD neuropathology in specific cell types were further prioritized. RESULTS: We revealed widespread DNA methylation alterations (DMA) in the enhancers of AD patients across different brain regions. In addition, the genome-wide transcription factor (TF) binding profiles showed that enhancers with DMA are pervasively regulated by TFs. The TF-enhancer-gene regulatory network analysis identified core regulatory triplets that are associated with brain and immune cell proportions and play important roles in AD pathogenesis. Enhancer regulatory circuits with DMA exhibited distinct chromatin accessibility patterns, which were further characterized at single-cell resolutions. CONCLUSIONS: Our study comprehensively investigated DNA methylation-mediated regulatory circuit abnormalities and provided novel insights into the potential pathogenesis of AD.

Cell migration induces apoptosis in osteosarcoma cell via inhibition of Wnt-ß-catenin signaling pathway.

The current design scheme on anti-cancer materials is mainly through tuning the mechanical properties of the materials to induce apoptosis in cancer cells, with the involvement of Rho/ROCK signaling pathway. We hypothesize that tuning the motility is another potential important approach to modifying the tumor microenvironment and inducing tumor apoptosis. To this aim, we have prepared RGD-modified substrates to regulate cell motility through modification of RGD with different concentrations, and systematically examined the effect of motility on the apoptosis of tumor cells, and the potential involvement of Wnt signaling pathway. Our studies indicated that RGD modification could be readily used to tune the motility of cancer cells. High RGD concentration significantly suppressed the migration of cancer cells, leading to significantly increased apoptosis rate, about three times of that of the unmodified samples. Western-blot analysis also showed that cell with low motility expressed more caspase-3 and PARP proteins. Further RNA sequence study strongly suggested that low motility inhibited the canonical Wnt signaling pathway, which in turn led to the activation of the mitochondria-associated caspase signaling pathway, and ultimately to the apoptosis of osteosarcoma cells. Activation of the Wnt-ß-catenin pathway through HLY78 significantly suppressed the apoptosis of MG-63 cells, further suggesting the critical role of Wnt pathway in motility-regulated-apoptosis of tumor cells. Our findings shed insights to understand the underlying mechanisms that induced the tumor cell apoptosis, and might provide new strategy for designing the novel anti-tumor materials.

Direct Reprogramming of Mouse Fibroblasts to Osteoblast-like Cells Using Runx2/Dlx5 Factors on Engineered Stiff Hydrogels.

Direct reprogramming of somatic cells into functional cells still faces major limitations in terms of efficiency and achieving functional maturity of the reprogramed cells. While different approaches have been developed commonly based on exploiting biochemical signals, introducing appropriate mechanical cues that stimulate the reprogramming process is rarely reported. In this study, collagen-coated polyacrylamide (PAM) hydrogels with stiffness close to that of collagenous bone (40 kPa) were adopted to augment the direct reprogramming process of mouse fibroblasts to osteoblastic-like cells. The results suggested that culturing cells on a hydrogel substrate enhanced the overexpression of osteogenic transcription factors using nonviral vectors and improved the yield of osteoblast-like cells. Particularly, a synergistic effect on achieving osteogenic functionality has been observed for the mechanical cues and overexpression of transcriptional factors, leading to enhanced osteogenic transformation and production of bone mineral matrix. Animal experiments suggested that reprogramed cells generated on matrix hydrogels accelerated bone regeneration and stimulated ectopic osteogenesis. Mechanism analysis suggested the critical involvement of actomyosin contraction and mechanical signal-mediated pathways like the RhoA-ROCK pathway, leading to a synergistic effect on the key transcriptional processes, including chromatin remodeling, nuclear translocation, and epigenetic transition. This study provides insights into the mechanical cue-enhanced direct reprogramming and cell therapy.

Intervention of muscle-building and antifrailty exercise combined with Baduanjin for frailty of different functional levels: study protocol for a randomised controlled trial.

INTRODUCTION: Frailty has been currently considered as a multidimensional concept, including physical, cognitive and social frailty. Frailty has also been associated with a range of adverse events, which might increase the risks of disability, falls, fractures, delirium and death. Increasing evidence has shown that multicomponent exercise training can improve physical and cognitive function, delay or reverse frailty. However, there is still a lack of exercise intervention programmes for the frail older adults in China. This trial aims to investigate the effects of the muscle-building and antifrailty exercise combined with Baduanjin on the physical function of frail older adults, as well as the effectiveness and safety of the intervention. METHODS AND ANALYSIS: This study is a prospective randomised controlled trial. A total of 192 patients, aged 70 years or older, who are diagnosed as prefrailty or frailty based on the Fried criteria will be included. Prior written and informed consent will be obtained from every subject. These subjects will be randomly assigned to the exercise intervention group (n=96) and the control group (n=96). The exercise intervention group will undergo different exercise programmes for different levels of physical function. They will perform the muscle-building and antifrailty exercise three times per week for 30-60 min for 24 weeks. The control group will implement health education on frailty and maintain the old lifestyle without any intervention.The primary outcomes include the change in frailty and functional capacity, assessed according to the Fried Scale and the Short Physical Performance Battery. Secondary outcomes include the changes in body composition, Activities of daily living, Mini-Mental State Examination, The Geriatric Depression Scale-15 and the haematological indicators. ETHICS STATEMENT: The study has been approved by the Medical Ethics Committee of the PLA General Hospital (approval no.: S2022-600-02). TRIAL REGISTRATION NUMBER: ChiCTR2300070535.

Controlled domain gels with a biomimetic gradient environment for osteochondral tissue regeneration.

In order to repair an osteochondral defect, it is critical to advance a bi-lineage constructive scaffold with gradient transition. In this study, we developed a simple and straightforward approach for fabricating a multi-domain gel scaffold through the assembly/disassembly of low-molecular-weight gels (LMWGs) inside a stable PEGDA network by photopolymerization. The versatility of this technology enabled to vary biological, topological, and mechanical properties through material selection and to generate a chondrogenic-osteogenic gradient transition. The multi-domain gel exhibited an increasing stiffness gradient along the longitudinal direction from the cartilage layer at approximately 20 kPa to the bone layer at approximately 300 kPa as well as spatial variation at the gradient interface. Moreover, the transitional layer with a condensed structure and intermediate stiffness prevented delamination of the contrasting layers and maintained microenvironmental differences in the upper and lower layers. The in vitro results indicated that each domain had an individual capacity to spatially control the differentiation of MSCs toward osteoblastic lineage and chondrocytic lineage. This was mainly because the mechanical and topographical cues from the respective domains played an important role in modulating the Rho-ROCK signaling pathway, whereas the blockage of ROCK signals significantly impaired domain-modulated osteogenesis and enhanced chondrogenesis. Additionally, the quantity and quality of osteochondral repair were evaluated at 4 and 8 weeks through histological analysis and micro-computed tomography (micro-CT). The results indicated that the multi-domain gels distinctly improved the regeneration of subchondral bone and cartilage tissues. Overall, the outcomes of this study can motivate future bioinspired gradient and heterogeneity strategies for osteochondral tissue regeneration. STATEMENT OF SIGNIFICANCE: The regeneration of osteochondral defects remains a major challenge due to the complexity of osteochondral structure and the limited self-repair capacity of cartilage. The gradient design to mimic the transition between the calcified cartilage and the subchondral bone plate as well as the zones of cartilage is an effective strategy. In this study, controlled multi-domain gels were fabricated through the assembly/disassembly of low-molecular-weight gels inside a stable PEGDA network by photopolymerization. The prepared multi-domain gels showed a chondrogenic-osteogenic gradient transition, which decreased the possibility of delamination and stimulated osteochondral tissue regeneration in vivo. Overall, our study promotes new strategies of bioinspired gradients and heterogeneities for more challenging applications.

MSC spheroids-loaded collagen hydrogels simultaneously promote neuronal differentiation and suppress inflammatory reaction through PI3K-Akt signaling pathway.

It is critical for the clinical success to take the anti-inflammatory function into consideration when integrating the neurogenesis into the nerve repair materials. To this aim, we prepared mesenchymal stem cell (MSC) spheroids-loaded collagen (Col) hydrogels with combined superior anti-inflammatory efficacy and neurogenic activity. The size of the MSC spheroids showed a strong modulation effect on both functions, and the MSC spheroids-100 sample exhibited the best neuronal and anti-inflammatory potentials. The observed dual functions were likely based on the elevated intrinsic cell-cell contacts and cell-extracellular matrix interactions from the MSC spheroids. MSC self-assembly as spheroids expedited the secretions of endogenous trophic factors and extracellular matrix (ECM), which was beneficial to drive neural stem cell differentiation into the neuronal lineage. In addition, the formation of the MSC spheroids secreted more amounts and types of cytokines as well as immunomodulatory paracrine factors to suppress LPS-induced inflammatory reaction. LC-MS/MS analysis further demonstrated that MSC spheroids contributed to the activation of neuroactive ligand-receptor interaction, thereby triggering downstream PI3K-Akt signal pathway, which was likely due to the acceleration of ECM-receptor interaction, gap junction and tight junction. Importantly, inhibiting Akt pathway significantly suppressed the neuronal differentiation, indicating that PI3K-Akt signal pathway was critically involved in the Col-MSC spheroid hydrogel mediated neuroprotection and neurogenesis. Such findings not only provided a simple approach for improving MSC-based therapies for neuron-related diseases, but also shed insight on understanding the underlying mechanisms of MSC-mediated neuronal differentiation.

Covalent immobilization of DJK-5 peptide on porous titanium for enhanced antibacterial effects and restrained inflammatory osteoclastogenesis.

Currently, implant-related bone infection characterized by aggravated infection-induced inflammatory responses and osteolysis, remains a severe challenge in orthopedic surgery, especially in patients with osteoporosis. Attempts to control such responses using biomaterials with combined immunomodulatory and anti-bacterial properties may provide novel strategies. Herein, DJK-5, a class of host defense peptides (HDPs) with established antimicrobial and immunomodulatory functions, was introduced into porous Ti alloy. Our results indicated that the DJK-5 immobilized surfaces showed intrinsically multifunctional properties, including antibacterial ability, anti-inflammation, biocompatibility and osteolysis-inhibiting properties. The results demonstrated that the antibacterial efficiency of DJK-5 functionalized surfaces was over 90 % for both Gram-positive and Gram-negative bacteria. Specifically, DJK-5 functionalized samples also possessed the excellent anti-bacterial activity against a mixture of bacterial strains, including S. aureus, S. epidermidis and P. aeruginosa, with an antibacterial rate against mixed bacteria reaching 91.36 %, as well as reduced biofilm formation. The remarkable anti-bacterial efficacy was likely based on the direct anti-bacterial effect of DJK-5, which destroyed the integrity of bacteria membranes, leading to the leakage of intracellular materials. Additionally, the immobilized DJK-5 surfaces could indirectly kill bacteria through promoted macrophage capacity to bacteria uptake. Furthermore, DJK-5 functionalized surfaces suppressed inflammatory reaction by decreasing the release of pro-inflammatory factors and increasing the secretions of anti-inflammatory factors, and thereby impeded the activation of NF-κB signal pathway, which resulted in the disruption of the actin rings and decreased Tracp5b expressions. Based on these promising findings, the multi-functional DJK-5 immobilized titanium represents an efficient alternative to realize better osseointegration in sever implant-associated bacterial infections.

The effect of form of carboxymethyl-chitosan dressings on biological properties in wound healing.

Chitosan and its derivative have been widely used for wound healing applications, but the effect of the chitosan form on wound healing related properties has been less exploited. To this aim, water-soluble carboxymethyl-chitosan (CMCS) crosslinked by 10 wt.% genipin was fabricated in three different forms of dressings, i.e. hydrogel, membrane and sponge. The properties of dressing were evaluated and compared in terms of surface morphology, mechanical properties, water absorption rate, gas permeability, coagulation performance and biological responses in vitro and in vivo. The results showed that the prepared CMCS sponge dressing with porous structure exhibited the best water absorption, gas permeability, hemostatic performance and promoting effect on human skin fibroblast proliferation. The sponge sample overall had the highest expressions of α-smooth muscle actin (α-SMA) and transforming growth factor-ß1 (TGF-ß1), while the CMCS hydrogel was favorable for stimulating the expression of matrix metalloproteinase-1 (MMP-1). Furthermore, the CMCS sponge dressing demonstrated the best performance in wound closure and accelerating wound repair in-vivo, showing the fastest epithelization, and best healing performance with the well-structure of epidermis and well-arranged collagen in the dermis. On the other hand, the CMCS hydrogel and membrane also demonstrated good biocompatibility, hemostatic properties and the capability to promote wound healing. Overall, CMCS sponge dressing demonstrated the optimal biological performances and excellent potential for the clinical wound healing applications.

Modulating cationicity of chitosan hydrogel to prevent hypertrophic scar formation during wound healing.

It is of great clinical significance to design wound dressing materials with combined excellent wound healing properties and superior capability to suppress hypertrophic scar formation. This study aimed to examine if and how the cationicity of chitosan would affect the hypertrophic scar-related outcomes, through preparing carboxymethyl chitosan hydrogels with different genipin concentrations (2.5%, 5%, 10% and 15%, respectively). An optimum window of chitosan cationicity (5% in our case) demonstrated potential to mitigate hypertrophic scar in wound healing by suppressing the expression of a-smooth muscle actin (a-SMA) and promoting secretion of type I matrix metalloproteinases (MMP-1). In vivo, the CMCS-5% hydrogel again showed smaller, thinner and smoother wound appearance. Moreover, the CMCS-5% sample with additional incorporation of 2% (V/V) Aloe vera gel exhibited further improved performance in scar inhibition. Overall, such findings might have important implications in chitosan-based wound dressing design for high-quality wound repair and effective scar inhibition.

Migration critically meditates osteoblastic differentiation of bone mesenchymal stem cells through activating canonical Wnt signal pathway.

Basic cellular events, such as focal adhesion and cytoskeleton organization, have been reported to be actively involved in fate decision process of stem cells, besides chemical and physical cues. Stem cell migration is critical in regulating various stem cell functions, but its influence on MSC differentiation into specific lineages has been rarely exploited. In this study, we used RGD-modified substrates to regulate cell motility though different RGD concentrations and systematically analyzed the correlation between osteoblastic differentiation and cell migration, as well as the role of Wnt signaling pathway. High motility correlated well with the significantly enhanced potential of the MSCs to differentiate into the osteoblastic lineage, as suggested by the significant up-regulations of Runx2, ALP, OCN expressions. The results also suggested that enhanced MSC migration efficiently activated the canonical Wnt-ß-catenin pathway and stimulated transcription activities leading to osteoblastic differentiation, likely through internal forces generated dynamically during migration. Blockage of the Wnt-ß-catenin pathway through artificial down-regulation of LRP5/6 expression significantly suppressed the osteoblastic differentiation for samples with high MSC motilities, further corroborating the critical involvement of Wnt/ß-catenin pathway in the cell migration induced mechanotransduction and MSC differentiation into osteoblastic lineage. Our findings provide important insight for understanding the complicate mechanisms involved in MSC fate selection process and bone regeneration, and would have significant implications in the optimal design of bone tissue engineering materials through regulating cell motility.

Modulation of osteogenic and haemostatic activities by tuning cationicity of genipin-crosslinked chitosan hydrogels.

Chitosan as a natural cationic polysaccharide has drawn wide interests as surface modification materials in orthopedic applications, with the potential to achieve combined osteogenic, antimicrobial and haemostatic functions. The cationicity of chitosan has been reported to play an important role in modifying the osteoblastic cell responses and the antibacterial activities, while its effect on the haemostatic properties has been rarely studied. To this aim, we prepared carboxymethyl chitosan hydrogels with different cationicity through crosslinking with different concentrations of genipin (1%, 2.5%, 5% and 10%). The genipin concentration strongly influenced both mesenchymal stem cell (MSC) responses and blood coagulation activity for chitosan-hydroxyapatite samples. Increasing genipin concentration overall enhanced the osteogenic and haemostatic potentials, and an optimum window of chitosan cationicity (5% genipin in our case) led to both the best MSC response and coagulant activities. In particular, the cationicity had demonstrated a profound modulation effect on the haemostatic activities of chitosan samples, through influencing three different aspects of the coagulation processes, including intrinsic coagulation pathway, aggregation and activation of platelet, and activation of erythrocyte. Tuning the crosslinking degree thus provides a simple and effective approach to achieving combined osteogenic and haemostatic functions, which has great potential in surface modification of surgical implants.