Effect of coculturing on the myogenic and adipogenic marker gene expression

Research progress of intramuscular fat formation based on co-culture

Intramuscular fat (IMF) is closely related to the meat quality of livestock and poultry. As a new cell culture technique in vitro, cell co-culture has been gradually applied to the related research of IMF formation because it can simulate the changes of microenvironment in vivo during the process of IMF cell formation. In the co-culture model, in addition to studying the effects of skeletal muscle cells on the proliferation and differentiation of IMF, we can also consider the role of many secretion factors in the formation of IMF, thus making the cell research in vitro closer to the real level in vivo. This paper reviewed the generation and origin of IMF, summarized the existing co-culture methods and systems, and discussed the advantages and disadvantages of each method as well as the challenges faced in the establishment of the system, with emphasis on the current status of research on the formation of IMF for human and animal based on co-culture technology.

Identification of core genes affecting IMF deposition in bovine

Intramuscular fat (IMF) content is an important economic factor in beef production. However, knowledge on the key factors controlling bovine IMF is limited. In this study, using weighted gene co-expression network analysis (WGCNA), nine modules were identified and the number of transcripts in these modules ranged from 36 to 3191. Two modules were found to be significantly associated with fat deposition and three genes (TCAP, MYH7, and TNNC1) were further identified by Protein-protein interaction (PPI), which may be the hub genes regulating bovine IMF deposition. In addition, considering the genetic variation, the PCK1 gene was found by functional enrichment analysis of overlapping genes, which was previously reported to be involved in IMF deposition. We noted that the core promoter region of buffalo PCK1 binds to transcription factors involved in lipid metabolism while cattle PCK1 binds transcription factors involved in muscle development. The results suggest that PCK1 participated in IMF deposition of buffalo and cattle in different ways. In summary, gene expression networks and new candidate genes associated with IMF deposition identified in this study. This would lay the foundation for further research into the molecular regulatory mechanisms underlying bovine IMF deposition.

Influence of Nutritional Status and Physical Exercise on Immune Response in Metabolic Syndrome

Metabolic Syndrome (MetS) is a cluster of metabolic alterations mostly related to visceral adiposity, which in turn promotes glucose intolerance and a chronic systemic inflammatory state, characterized by immune cell infiltration. Such immune system activation increases the risk of severe disease subsequent to viral infections. Strong correlations between elevated body mass index (BMI), type-2-diabetes and increased risk of hospitalization after pandemic influenza H1N1 infection have been described. Similarly, a correlation between elevated blood glucose level and SARS-CoV-2 infection severity and mortality has been described, indicating MetS as an important predictor of clinical outcomes in patients with COVID-19. Adipose secretome, including two of the most abundant and well-studied adipokines, leptin and interleukin-6, is involved in the regulation of energy metabolism and obesity-related low-grade inflammation. Similarly, skeletal muscle hormones—called myokines—released in response to physical exercise affect both metabolic homeostasis and immune system function. Of note, several circulating hormones originate from both adipose tissue and skeletal muscle and display different functions, depending on the metabolic context. This review aims to summarize recent data in the field of exercise immunology, investigating the acute and chronic effects of exercise on myokines release and immune system function.

Hoxa11 and Hoxa13 facilitate slow-twitch muscle formation in C2C12 cells and indirectly affect the lipid deposition of 3T3-L1 cells

Muscle-fiber type in livestock skeletal muscles influences meat quality, but the underlying mechanisms remain unclear. We previously showed that Homeobox A11 (Hoxa11) and Homeobox A13 (Hoxa13) are differentially expressed in fast- and slow-twitch muscles, but their effects on the formation of muscle-fiber types and intramuscular fat deposition have not been investigated. Here, our results revealed that overexpression of Hoxa11 and Hoxa13 delayed cell-cycle progression in C2C12 myoblasts, reduced their proliferation, and promoted their differentiation into slow-twitch muscle fibers. Knockdown experiments produced the opposite results. The conditioned media of differentiated C2C12 cells with Hoxa11/Hoxa13 overexpression or knockdown were harvested. Staining results showed that adipogenesis of preadipocytes was significantly promoted by Hoxa13 knockdown C2C12 cell culture medium. Changes in lipid accumulation were due to a reduction in lipid decomposition and an increase in triglyceride synthesis; genes related to fatty-acid synthesis were decreased. In conclusion, our study showed that Hoxa11 and Hoxa13 promote slow-twitch muscle formation and indirectly regulate preadipocyte adipogenesis, which may facilitate meat-quality improvement in the future.

Comparative transcriptome analysis reveals that PCK1 is a potential gene affecting IMF deposition in buffalo

BACKGROUND

In China, although buffaloes are abundant, beef is mainly obtained from cattle, and this preference is mainly attributed to the low intramuscular fat (IMF) content of buffalo. Genetic factors are an important driver that affects IMF deposition.

RESULTS

To reveal the intrinsic factors responsible for the low IMF content of buffalo, mRNA expression patterns in muscle and adipose tissue between buffalo and cattle were characterized by RNA sequencing analysis. The IMF content in Nanyang cattle was higher than that in Xinyang buffalo. A total of 1566 mRNAs expressed in adipose tissue showed differential expression between the longissimus dorsi muscles of buffalo and cattle. Functional annotation suggested a difference in the glycolysis/gluconeogenesis pathway between the two species. The results of RT-qPCR analysis and gain-of-function experiments confirmed the positive association between the IMF content and phosphoenolpyruvate carboxykinase 1 (PCK1) expression in buffalo. In both mouse C2C12 cells and cultured bovine myocytes, the activity of the PCK1 promoter in buffalo is lower than that in cattle. However, in mouse 3T3-L1 adipocytes and cultured bovine adipocytes, the activity of PCK1 in buffalo promoter is higher than that in cattle.

CONCLUSIONS

These results indicate the important role of PCK1 in buffalo IMF deposition and illustrate the differences between buffalo and cattle promoter activity that drive PCK1 expression. This research helps to establish a foundation for further studies investigating IMF deposition in buffalo.

The whole-transcriptome landscape of muscle and adipose tissues reveals the ceRNA regulation network related to intramuscular fat deposition in yak

Background

The Intramuscular fat (IMF) content in meat products, which is positively correlated with meat quality, is an important trait considered by consumers. The regulation of IMF deposition is species specific. However, the IMF-deposition-related mRNA and non-coding RNA and their regulatory network in yak (Bos grunniens) remain unknown. High-throughput sequencing technology provides a powerful approach for analyzing the association between transcriptome-related differences and specific traits in animals. Thus, the whole transcriptomes of yak muscle and adipose tissues were screened and analyzed to elucidate the IMF deposition-related genes. The muscle tissues were used for IMF content measurements.

Results

Significant differences were observed between the 0.5- and 2.5-year-old yaks. Several mRNAs, miRNAs, lncRNAs and circRNAs were generally expressed in both muscle and adipose tissues. Between the 0.5- and 2.5-year-old yaks, 149 mRNAs, 62 miRNAs, 4 lncRNAs, and 223 circRNAs were differentially expressed in muscle tissue, and 72 mRNAs, 15 miRNAs, 9 lncRNAs, and 211 circRNAs were differentially expressed in adipose tissue. KEGG annotation revelved that these differentially expressed genes were related to pathways that maintain normal biological functions of muscle and adipose tissues. Moreover, 16 mRNAs, 5 miRNAs, 3 lncRNAs, and 5 circRNAs were co-differentially expressed in both types of tissue. We suspected that these co-differentially expressed genes were involved in IMF-deposition in the yak. Additionally, LPL, ACADL, SCD, and FASN, which were previously shown to be associated with the IMF content, were identified in the competing endogenous RNA (ceRNA) regulatory network that was constructed on the basis of the IMF deposition-related genes. Three ceRNA subnetworks also revealed that TCONS-00016416 and its target SIRT1 “talk” to each other through the same miR-381-y and miR-208 response elements, whereas TCONS-00061798 and its target PRKCA, and TCONS-00084092 and its target LPL “talk” to each other through miR-122-x and miR-499-y response elements, respectively.

Conclusion

Taken together, our results reveal the potential mRNA and noncoding RNAs involved in IMF deposition in the yak, providing a useful resource for further research on IMF deposition in this animal species.

Molecular and Cellular Response of Co-cultured Cells toward Cobalt Chloride (CoCl2)-Induced Hypoxia

Cobalt chloride (CoCl₂) is a well-known hypoxia mimetic mediator that induces hypoxia-like responses. CoCl₂, a mediator confirmed to alleviate hypoxia-inducible factor-1 (HIF-1), has been associated with a variety of hypoxic responses. HIF-1 is the foremost transcriptionfactor that is particularly activated during hypoxia and regulates various genes. Therefore, this study aimed to investigate the cellular and molecular responses of the co-cultured cells under the influence of the CoCl₂-induced hypoxic condition. Mono- and co-cultured C2C12 and 3T3-L1 cells were exposed to CoCl₂, and a significant induction in HIF-1, reactive oxygen species and lipid peroxidase and a reduction in glutathione and catalase were observed. The expressions of proapoptotic genes like Bax, p53, caspase-9, and caspase-3 were notably increased, whereas the antiapoptotic gene, i.e., Bcl2, was downregulated during hypoxia in mono- as well as co-cultured C2C12 cells. However, the co-cultured C2C12 cells show significantly lower induction in oxidative stress and expression of apoptotic genes in comparison to monocultured C2C12 cells. Whereas, the co-cultured 3T3-L1 cells show comparatively higher oxidative stress and apoptotic event in comparison to monocultured 3T3-L1 cells. The reason may be the communication between the cells and some soluble factors that help in cell survival/death from hypoxia. Moreover, it may also be due to the fact that fat and muscle cells interact and communicate via proximity and mutual ability when growing together. Therefore, the co-culture system provides a unique approach to intercellular communication between the two different cell types.

miRNA transcriptome comparison between muscle and adipose tissues indicates potential miRNAs associated with intramuscular fat in Chinese swamp buffalo

The amount of intramuscular fat (IMF) affects the tenderness and juiciness of beef and is an important indicator of beef quality. A few miRNAs involved in IMF deposition have been identified in other livestock. However, in the buffalo, the association between miRNA and IMF has not been reported and the miRNA expression profile remains poorly understood. In this study, small RNA sequencing was performed to characterize the miRNA expression pattern in muscle and adipose tissues using the Illumina platform. A total of 108 differentially expressed (DE) miRNAs were identified, including 98 known miRNAs and 10 novel miRNAs. A qRT-PCR experiment confirmed the quality of the DE analysis. Eight DE miRNAs showed high expression in adipose tissue and a considerable expression level in muscle tissue. Functional enrichment indicated that bta-miR-148a, bta-miR-143, bta-miR-10b, bta-let-7i, bta-let-7f, bta-let-7b, bta-miR-30a-5p, and bta-miR-100 were significantly associated with adipogenesis, suggesting these as candidate regulators for IMF deposition in buffalo. However, further functional validation is required. This is the first characterization of the miRNA expression profile in the muscle and adipose tissues of buffalo. These results provide information for the identification of miRNAs with potential effects on IMF deposition in buffalo.

Cytotoxic effect of TDZ on human cervical cancer cells

The present study investigates the anticancer activity of Thidiazuron (TDZ). Anticancer activity of TDZ was evaluated in cervical carcinoma cells (HeLa cells). Sulforhodamine-B (SRB) assay indicates that TDZ was about 100 times more toxic to the cancer cell than normal cells. TUNEL assay showed TDZ induced DNA damage in tumor cells. The loss of mitochondrial membrane potential (MMP) in cancer cells was observed following TDZ treatment. The Bax and bcl-2 gene expression ratio are highly responsible for the regulation of MMP balance, and these ratio was significantly altered following TDZ treatment. The p53 and caspase-3 expressions were increased in cancer cells following treatment. Caspase-3 activation is the key factor for apoptosis. Cytotoxicity of TDZ on HeLa cells was 100 times higher than normal kidney cell (MDCK cells). Moreover, the anticancer activity of TDZ was tested by DNA damage, mitochondrial dysfunction, some gene expression and caspase-3 inhibition in silico. TDZ detected has higher ability on early apoptosis of cancer cell through DNA damage. Additionally, cancer cellular MMP was significantly reduced under inoculation of TDZ. In silico assay confirmed that TDZ was able to bind with the active site of the capase-3 protein. Therefore, taking all these data together it is suggested that the TDZ may be a potential agent to act against cervical cancer cells.

C2C12 myotubes inhibit the proliferation and differentiation of 3T3-L1 preadipocytes by reducing the expression of glucocorticoid receptor gene

Obesity is a well-established risk factor to health for its relationship with insulin resistance, diabetes and metabolic syndrome. Myocyte-adipocyte crosstalk model plays a significant role in studying the interaction of muscle and adipose development. Previous related studies mainly focus on the effects of adipocytes on the myocytes activity, however, the influence of myotubes on the preadipocytes development remains unclear. The present study was carried out to settle this issue. Firstly, the co-culture experiment showed that the proliferation, cell cycle, and differentiation of 3T3-L1 preadipocytes were arrested, and the apoptosis was induced, by differentiated C2C12 myotubes. Next, the sensitivity of 3T3-L1 preadipocytes to glucocorticoids (GCs), which was well known as cell proliferation, differentiation, apoptosis factor, was decreased after co-cultured with C2C12 myotubes. What's more, our results showed that C2C12 myotubes suppressed the mRNA and protein expression of glucocorticoid receptor (GR) in 3T3-L1 preadipocytes, indicating the potential mechanism of GCs sensitivity reduction. Taken together, we conclude that C2C12 myotubes inhibited 3T3-L1 preadipocytes proliferation and differentiation by reducing the expression of GR. These data suggest that decreasing GR by administration of myokines may be a promising therapy for treating patients with obesity or diabetes.

A novel approach for in vitro meat production

The present review describes the possibility of in vitro meat production with the help of advanced co-culturing methods. In vitro meat production method could be a possible alternative for the conventional meat production. Originally, the research on in vitro meat production was initiated by the National Aeronautics and Space Administration (NASA) for space voyages. The required key qualities for accepting in vitro meat for consumption would be good efficiency ratio, increased protein synthesis rate in skeletal muscles, and mimicking the conventional meat qualities. In vitro culturing of meat is possible with the use of skeletal muscle tissue engineering, stem cell, cell co-culture, and tissue culture methods. Co-culture of myoblast and fibroblast is believed as one of the major techniques for in vitro meat production. In our lab, we have co-cultured myoblast and fibroblast. We believe that a billion pounds of in vitro meat could be produced from one animal for consumption. However, we require a great deal of research on in vitro meat production.

Retinoic acids change gene expression profiles of bovine intramuscular adipocyte differentiation, based on microarray analysis

Beef marbling is caused by intramuscular deposition and it is an economically important trait in the beef industry. Vitamin A (VA) is an important feed supplement for cattle, but it can hinder marbling if provided in excess. In cattle, VA forms various derivatives such as all-trans retinoic acid (ATRA) and 9-cis retinoic acid (9cRA). Therefore, we investigated the genes involved in bovine intramuscular adipogenesis after VA treatment with ATRA and 9cRA. Differential gene expression levels were validated by microarray analysis in a clonal bovine intramuscular preadipocyte (BIP) cell line derived from the intramuscular adipose tissue of Japanese Black cattle. BIP cells were harvested 6 days after adipogenic stimulation with either 1 μmol/L ATRA, 1 μmol/L 9cRA or non-retinoic acid control. The ATRA- and 9cRA-treated cells exhibited reduced transcription of genes involved in the circulatory system and muscle development compared with the no retinoic acid (RA) treatment. In addition, the ATRA- and 9cRA-treated cells exhibited increased transcription of genes involved in the immune system, protein kinase B signaling and responses to various stimuli. These results demonstrate the lower expression of muscle development in ATRA- and 9cRA-treated BIP cells during adipogenesis.

Application of cell co-culture system to study fat and muscle cells

Animal cell culture is a highly complex process, in which cells are grown under specific conditions. The growth and development of these cells is a highly unnatural process in vitro condition. Cells are removed from animal tissues and artificially cultured in various culture vessels. Vitamins, minerals, and serum growth factors are supplied to maintain cell viability. Obtaining result homogeneity of in vitro and in vivo experiments is rare, because their structure and function are different. Living tissues have highly ordered complex architecture and are three-dimensional (3D) in structure. The interaction between adjacent cell types is quite distinct from the in vitro cell culture, which is usually two-dimensional (2D). Co-culture systems are studied to analyze the interactions between the two different cell types. The muscle and fat co-culture system is useful in addressing several questions related to muscle modeling, muscle degeneration, apoptosis, and muscle regeneration. Co-culture of C2C12 and 3T3-L1 cells could be a useful diagnostic tool to understand the muscle and fat formation in animals. Even though, co-culture systems have certain limitations, they provide a more realistic 3D view and information than the individual cell culture system. It is suggested that co-culture systems are useful in evaluating the intercellular communication and composition of two different cell types.

Cortisol effect on heat shock proteins in the C2C12 and 3T3-L1 cells

The present study was carried out to understand the effect of cortisol on heat shock protein system (Hsps) in the C2C12 and 3T3-L1 cells under co-culture system. Cells were co-cultured by using Transwell inserts with a 0.4-μm porous membrane to separate C2C12 and 3T3-L1 cells. Each cell type was grown independently on the Transwell plates. After cell differentiation, inserts containing 3T3-L1 cells were transferred to C2C12 plates and inserts containing C2C12 cells transferred to 3T3-L1 plates. Ten micrograms per microliter of cortisol was added to the medium. Following 72 h of treatment, the cells in the lower wells were harvested for analysis. Heat shock proteins (Hsps) such as Hsp27, Hsp70, and Hsp90 were selected for the analysis. The qRT-PCR results showed the significant increase in the mRNA expression of as Hsp27, Hsp70, and Hsp90. In addition, confocal microscopical investigation showed the cortisol treatment increases Hsps expressions in the mono and co-cultured C2C12 and 3T3-L1 cells. From the results, we concluded that the cortisol increases Hsps expression in the co-cultured C2C12 and 3T3-L1 cells, which is differed from one-dimensional mono-cultured C2C12 and 3T3-L1 cells.