Adipoinductive effect of extracellular matrix involves cytoskeleton changes and SIRT1 activity in adipose tissue stem/stromal cells

SIRT1-mediated tunnelling nanotubes may be a potential intervention target for arsenic-induced hepatocyte senescence and liver damage

Arsenic, a widespread environmental poison, can cause significant liver damage upon exposure. Mitochondria are the most sensitive organelles to external factors. Dysfunctional mitochondria play a crucial role in cellular senescence and liver damage. Tunnelling nanotubes (TNTs), membrane structures formed between cells, with fibrous actin (F-actin) serving as the scaffold, facilitate mitochondrial transfer between cells. Notably, TNTs mediate the delivery of healthy mitochondria to damaged cells, thereby mitigating cellular damage. Although limited studies have suggested that F-actin may be modulated by the longevity gene SIRT1, the association between arsenic-induced liver damage and this mechanism remains unexplored. The findings of the current study indicate that arsenic suppresses SIRT1 and F-actin in the rat liver and MIHA cells, impeding the formation of TNTs and mitochondrial transfer between MIHA cells, thereby playing a pivotal role in mitochondrial dysfunction, cellular senescence and liver damage induced by arsenic. Notably, increasing SIRT1 levels effectively mitigated liver mitochondrial dysfunction and cellular senescence triggered by arsenic, highlighting SIRT1's crucial regulatory function. This research provides novel insights into the mechanisms underlying arsenic-induced liver damage, paving the way for the development of targeted preventive and therapeutic drugs to address arsenic-induced liver damage.

Sirtuins: Key players in obesity-associated adipose tissue remodeling

Obesity, a complex disease involving an excessive amount of body fat and a major threat to public health all over the world, is the determining factor of the onset and development of metabolic disorders, including type 2 diabetes, cardiovascular diseases, and non-alcoholic fatty liver disease. Long-term overnutrition results in excessive expansion and dysfunction of adipose tissue, inflammatory responses and over-accumulation of extracellular matrix in adipose tissue, and ectopic lipid deposit in other organs, termed adipose tissue remodeling. The mammalian Sirtuins (SIRT1-7) are a family of conserved NAD⁺-dependent protein deacetylases. Mounting evidence has disclosed that Sirtuins and their prominent substrates participate in a variety of physiological and pathological processes, including cell cycle regulation, mitochondrial biogenesis and function, glucose and lipid metabolism, insulin action, inflammatory responses, and energy homeostasis. In this review, we provided up-to-date and comprehensive knowledge about the roles of Sirtuins in adipose tissue remodeling, focusing on the fate of adipocytes, lipid mobilization, adipose tissue inflammation and fibrosis, and browning of adipose tissue, and we summarized the clinical trials of Sirtuin activators and inhibitors in treating metabolic diseases, which might shed light on new therapeutic strategies for obesity and its associated metabolic diseases.

Characterized the Adipogenic Capacity of Adipose-Derived Stem Cell, Extracellular Matrix, and Microenvironment With Fat Components Grafting

Background: Autologous fat grafting has been a widely used technique; however, the role of adipose-derived stem cells (ASCs), extracellular matrix (ECM), and microenvironment in fat regeneration are not fully understood. Methods: Lipoaspirates were obtained and processed by inter-syringe shifting to remove adipocytes, yielding an adipocyte-free fat (Aff). Aff was then exposed to lethal dose of radiation to obtain decellularized fat (Df). To further remove microenvironment, Df was rinsed with phosphate-buffered saline (PBS) yielding rinsed decellularized fat (Rdf). Green fluorescent protein (GFP) lentivirus (LV-GFP)-transfected ASCs were added to Df to generate cell-recombinant decellularized fat (Crdf). Grafts were transplanted subcutaneously into nude mice and harvested over 3 months. Results: Removal of adipocytes (Aff) didn't compromise the retention of fat grafts, while additional removal of stromal vascular fraction (SVF) cells (Df) and microenvironment (Rdf) resulted in poor retention by day 90 (Aff, 82 ± 7.1% vs. Df, 28 ± 6.3%; p < 0.05; vs. Rdf, 5 ± 1.2%; p < 0.05). Addition of ASCs to Df (Crdf) partially restored its regenerative potential. Aff and Crdf exhibited rapid angiogenesis and M2-polarized macrophages infiltration, in contrast to impaired angiogenesis and M1-polarized inflammatory pattern in Df. GFP + ASCs participated in angiogenesis and displayed a phenotype of endothelial cells in Crdf. Conclusion: Adipose ECM and microenvironment have the capacity to stimulate early adipogenesis while ECM alone cannot induce adipogenesis in vivo. By directly differentiating into endothelial cells and regulating macrophage polarization, ASCs coordinate early adipogenesis with angiogenesis and tissue remodeling, leading to better long-term retention and greater tissue integrity.

DNA Methylation as a Marker of Body Shape in Premenopausal Women

Preferential accumulation of fat in the gluteo-femoral (GF) depot (pear shape) rather than in the abdominal (A) depot (apple shape), protects against the development of metabolic diseases but the underlying molecular mechanism is still unknown. Recent data, including our work, suggest that differential epigenetic marking is associated with regulation of genes attributed to distinct fat distribution. Here, we aimed to compare the genomic DNA methylation signatures between apple and pear-shaped premenopausal women. To investigate the contribution of upper and lower body fat, we used paired samples of A-FAT and GF-FAT, analyzed on the BeadChip Methylation Array and quantified the differentially methylated sites between the 2 groups of women. We found unique DNA methylation patterns within both fat depots that are significantly different depending on the body fat distribution. Around 60% of the body shape specific DNA methylation sites identified in adipose tissue are maintained ex vivo in cultured preadipocytes. As it has been reported before in other cell types, we found only a hand full of genes showing coordinated differential methylation and expression levels. Finally, we determined that more than 50% of the body shape specific DNA methylation sites could also be detected in whole blood derived DNA. These data reveal a strong DNA methylation program associated with adipose tissue distribution with the possibility that a simple blood test could be used as a predictive diagnostic indicator of young women who are at increased risk for progressing to the apple body shape with a higher risk of developing obesity related complications. Clinical Trial Registration:https://clinicaltrials.gov/ct2/show/NCT02728635 and https://clinicaltrials.gov/ct2/show/NCT02226640, identifiers NCT02728635 and NCT02226640.

Differential expression and alternative splicing of transcripts in orbital adipose/connective tissue of thyroid-associated ophthalmopathy

Thyroid-associated ophthalmopathy is a typical autoimmune disease of orbital tissues. Alternative splicing significantly influences many diseases progression, including cancer, age-related macular degeneration, and multiple sclerosis, by modulating the expression of transcripts. However, its role in thyroid-associated ophthalmopathy is still unclear. In this study, differential expression transcripts and differential alternative splicing genes in orbital adipose/connective tissues of thyroid-associated ophthalmopathy patients were detected using RNA sequencing, Cuffdiff, and replicate multivariate analysis of transcript splicing. Three thousand ninety six differential expression transcripts and 2355 differential alternative splicing genes were screened out, while functional enrichment analysis indicated that differential expression transcript and differential alternative splicing genes were associated with immune modulation, extracellular matrix remodeling, and adipogenesis. The expression of the SORBS1, SEPT2, COL12A1, and VCAN gene transcripts was verified by qRT-PCR. In conclusion, prevalent alternative splicing is involved in the disease development in thyroid-associated ophthalmopathy. More attention should be paid to the mechanism of alternative splicing to explore more potential therapeutic targets in thyroid-associated ophthalmopathy.

Recent Advance in Source, Property, Differentiation, and Applications of Infrapatellar Fat Pad Adipose-Derived Stem Cells

Infrapatellar fat pad (IPFP) can be easily obtained during knee surgery, which avoids the damage to patients for obtaining IPFP. Infrapatellar fat pad adipose-derived stem cells (IPFP-ASCs) are also called infrapatellar fat pad mesenchymal stem cells (IPFP-MSCs) because the morphology of IPFP-ASCs is similar to that of bone marrow mesenchymal stem cells (BM-MSCs). IPFP-ASCs are attracting more and more attention due to their characteristics suitable to regenerative medicine such as strong proliferation and differentiation, anti-inflammation, antiaging, secreting cytokines, multipotential capacity, and 3D culture. IPFP-ASCs can repair articular cartilage and relieve the pain caused by osteoarthritis, so most of IPFP-related review articles focus on osteoarthritis. This article reviews the anatomy and function of IPFP, as well as the discovery, amplification, multipotential capacity, and application of IPFP-ASCs in order to explain why IPFP-ASC is a superior stem cell source in regenerative medicine.