Wnt signaling related transcripts and their relationship to energy metabolism in C2C12 myoblasts under temperature stress

Effects of culture temperature (37°C, 39°C) and oxygen concentration (20%, 2%) on proliferation and differentiation of C2C12 cells

Cells, culture media, and so on are important elements of cultured meat production technology. Also, the environment (humidity, temperature, air composition, dissolved oxygen tension, etc.) for in vivo muscle production are important. Among cell culture conditions, culture temperature and oxygen concentration are important physical factors that can affect cells. The objective of this study was to determine effects of culture temperature and oxygen concentration on proliferation and differentiation of muscle cells. This study was conducted using C2C12 cells of rat myoblasts widely used in muscle physiology. The temperature was chosen to induce some thermal stress at 39°C, and the oxygen concentration was selected at 2% to mimic the oxygen levels present in muscle cells in vivo. Culture conditions consisted of CON (37°C/20% O2), T1 (37°C/2% O2), T2 (39°C/20% O2) and T3 (39°C/2% O2). In terms of cell proliferation, temperature conditions had a significant impact (p < 0.05), and a temperature of 39°C was found to reduce the cell count. Oxygen conditions had a significant impact on 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) absorbance, and temperature conditions were found to have a greater influence on cell proliferation compared to oxygen condition and interaction condition. The temperature conditions were found to have a significant impact (p < 0.05) on the expression of proteins related to myogenesis compared to oxygen conditions. The significant increase (p < 0.05) in the protein expression levels of Myh, Myod1, Myog, and Mb in T2 compared to CON, and in T3 compared to T1, suggests that a temperature of 39°C enhances the expression of myogenic differentiation proteins. These results indicate that temperature conditions have a significant impact (p < 0.05) on cell proliferation and differentiation, more so than oxygen conditions and interaction conditions. And a temperature of 39°C was found to inhibit cell proliferation, but in the case of differentiation, it was observed to be promoted due to the upregulation of myogenic differentiation proteins.

Fast freezing inhibits melanin synthesis of melanocytes by modulating the Wnt/β-catenin signalling pathway

Skin hyperpigmentation is mainly caused by excessive synthesis of melanin; however, there is still no safe and effective therapy for its removal. Here, we found that the dermal freezer was able to improve UVB-induced hyperpigmentation of guinea pigs without causing obvious epidermal damage. We also mimic freezing stimulation at the cellular level by rapid freezing and observed that freezing treatments <2.5 min could not decrease cell viability or induce cell apoptosis in B16F10 and Melan-A cells. Critically, melanin content and tyrosinase activity in two cells were greatly reduced after freezing treatments. The dramatic decrease in tyrosinase activity was associated with the downregulation of MITF, TYR, TRP-1 and TRP-2 protein expression in response to freezing treatments for two cells. Furthermore, our results first demonstrated that freezing treatments significantly reduced the levels of p-GSK3β and β-catenin and the nuclear accumulation of β-catenin in B16F10 and Melan-A cells. Together, these data suggest that fast freezing treatments can inhibit melanogenesis-related gene expression in melanocytes by regulating the Wnt/β-catenin signalling pathway. The inhibition of melanin production eventually contributed to the improvement in skin hyperpigmentation induced by UVB. Therefore, fast freezing treatments may be a new alternative of skin whitening in the clinic in the future.

Using a metabolomics approach to investigate the sensitivity of a potential Arctic-invader and its Arctic sister-species to marine heatwaves and traditional harvesting disturbances

Coastal species are threatened by fishing practices and changing environmental conditions, such as marine heatwaves (MHW). The mechanisms that confer tolerance to such stressors in marine invertebrates are poorly understood. However, differences in tolerance among different species may be attributed to their geographical distribution. To test the tolerance of species occupying different thermal ranges, we used two closely related bivalves the softshell clam Mya arenaria (Linnaeus, 1758), a cold-temperate invader with demonstrated potential for establishment in the Arctic, and the blunt gaper Mya truncata (Linnaeus, 1758), a native polar species. Clams were subjected to a thermal stress, mimicking a MHW, and harvesting stress in a controlled environment. Seven acute temperature changes (2, 7, 12, 17, 22, 27, and 32 °C) were tested at two harvesting disturbance intensities (with, without). Survival was measured after 12 days and three tissues (gills, mantle, and posterior adductor muscle) collected from surviving individuals for targeted metabolomic profiling. MHW tolerance differed significantly between species: 26.9 °C for M. arenaria and 17.8 °C for M. truncata, with a negligeable effect of harvesting. At the upper thermal limit, M. arenaria displayed a more profound metabolomic remodelling when compared to M. truncata, and this varied greatly between tissue types. Network analysis revealed differences in pathway utilization at the upper MHW limit, with M. arenaria displaying a greater reliance on multiple DNA repair and expression and cell signalling pathways, while M. truncata was limited to fewer pathways. This suggests that M. truncata is ill equipped to cope with warming environments. MHW patterning in the Northwest Atlantic may be a strong predictor of population survival and future range shifts in these two clam species. As polar environments undergo faster rates of warming compared to the global average, M. truncata may be outcompeted by M. arenaria expanding into its native range.

Temperature-Induced Sex Differentiation in River Prawn (Macrobrachium nipponense): Mechanisms and Effects

Macrobrachium nipponense is gonochoristic and sexually dimorphic. The male prawn grows faster and usually has a larger size than the female. Therefore, a higher male proportion in stock usually results in higher yield. To investigate the impact of temperature on sexual differentiation in M. nipponense, two temperature treatments (26 °C and 31 °C) were conducted. The results showed that compared to the 31 °C treatment (3.20 ± 0.12), the 26 °C treatment displayed a lower female/male ratio (2.20 ± 0.11), which implied that a lower temperature could induce masculinization in M. nipponense. The temperature-sensitive sex differentiation phase was 25-35 days post hatching (DPH) at 26 °C while 15-20 DPH at 31 °C. Transcriptome and qPCR analysis revealed that a lower temperature up-regulated the expression of genes related to androgen secretion, and down-regulated the expressions of genes related to oogonia differentiation. Thirty-one temperature-regulated sex-differentiation genes were identified and the molecular mechanism of temperature-regulated sex differentiation was suggested. The finding of this study indicates that temperature regulation can be proposed as an innovative strategy for improving the culture yield of M. nipponense.

The Anti-Müllerian Hormone as Endocrine and Molecular Marker Associated with Reproductive Performance in Holstein Dairy Cows Exposed to Heat Stress

Anti-Müllerian hormone (AMH) is proposed as a biomarker for fertility in cattle, yet this associative relationship appears to be influenced by heat stress (HS). The objective was to test serum AMH and AMH-related single nucleotide polymorphisms (SNPs) as markers potentially predictive of reproductive traits in dairy cows experiencing HS. The study included 300 Holstein cows that were genotyped using BovineSNP50 (54,000 SNP). A genome-wide association study was then executed. Nine intragenic SNPs within the pathways that influence the AMH gene were found important with multiple comparisons adjustment tests (p < 1.09 × 10-6). A further validation study was performed in an independent Holstein cattle population, which was divided into moderate (MH; n = 152) and severe heat-stressed (SH; n = 128) groups and then subjected to a summer reproductive management program. Serum AMH was confirmed as a predictor of fertility measures (p < 0.05) in MH but not in the SH group. Cows were genotyped, which revealed four SNPs as predictive markers for serum AMH (p < 0.01), reproductive traits (p < 0.01), and additional physiological variables (p < 0.05). These SNPs were in the genes AMH, IGFBP1, LGR5, and TLR4. In conclusion, serum AMH concentrations and AMH polymorphisms are proposed as predictive markers that can be used in conjunction with genomic breeding value approaches to improve reproductive performance in Holstein cows exposed to summer HS conditions.

Transcriptomic Response of Differentiating Porcine Myotubes to Thermal Stress and Donor Piglet Age

Climate change is a current concern that directly and indirectly affects agriculture, especially the livestock sector. Neonatal piglets have a limited thermoregulatory capacity and are particularly stressed by ambient temperatures outside their optimal physiological range, which has a major impact on their survival rate. In this study, we focused on the effects of thermal stress (35 °C, 39 °C, and 41 °C compared to 37 °C) on differentiating myotubes derived from the satellite cells of Musculus rhomboideus, isolated from two different developmental stages of thermolabile 5-day-old (p5) and thermostable 20-day-old piglets (p20). Analysis revealed statistically significant differential expression genes (DEGs) between the different cultivation temperatures, with a higher number of genes responding to cold treatment. These DEGs were involved in the macromolecule degradation and actin kinase cytoskeleton categories and were observed at lower temperatures (35 °C), whereas at higher temperatures (39 °C and 41 °C), the protein transport system, endoplasmic reticulum system, and ATP activity were more pronounced. Gene expression profiling of HSP and RBM gene families, which are commonly associated with cold and heat responses, exhibited a pattern dependent on temperature variability. Moreover, thermal stress exhibited an inhibitory effect on cell cycle, with a more pronounced downregulation during cold stress driven by ADGR genes. Additionally, our analysis revealed DEGs from donors with an undeveloped thermoregulation capacity (p5) and those with a fully developed thermoregulation capacity (p20) under various cultivation temperature. The highest number of DEGs and significant GO terms was observed under temperatures of 35 °C and 37 °C. In particular, under 35 °C, the DEGs were enriched in insulin, thyroid hormone, and calcium signaling pathways. This result suggests that the different thermoregulatory capacities of the donor piglets determined the ability of the primary muscle cell culture to differentiate into myotubes at different temperatures. This work sheds new light on the underlying molecular mechanisms that govern piglet differentiating myotube response to thermal stress and can be leveraged to develop effective thermal management strategies to enhance skeletal muscle growth.

Spatial transcriptomics reveals metabolic changes underly age-dependent declines in digit regeneration

De novo limb regeneration after amputation is restricted in mammals to the distal digit tip. Central to this regenerative process is the blastema, a heterogeneous population of lineage-restricted, dedifferentiated cells that ultimately orchestrates regeneration of the amputated bone and surrounding soft tissue. To investigate skeletal regeneration, we made use of spatial transcriptomics to characterize the transcriptional profile specifically within the blastema. Using this technique, we generated a gene signature with high specificity for the blastema in both our spatial data, as well as other previously published single-cell RNA-sequencing transcriptomic studies. To elucidate potential mechanisms distinguishing regenerative from non-regenerative healing, we applied spatial transcriptomics to an aging model. Consistent with other forms of repair, our digit amputation mouse model showed a significant impairment in regeneration in aged mice. Contrasting young and aged mice, spatial analysis revealed a metabolic shift in aged blastema associated with an increased bioenergetic requirement. This enhanced metabolic turnover was associated with increased hypoxia and angiogenic signaling, leading to excessive vascularization and altered regenerated bone architecture in aged mice. Administration of the metabolite oxaloacetate decreased the oxygen consumption rate of the aged blastema and increased WNT signaling, leading to enhanced in vivo bone regeneration. Thus, targeting cell metabolism may be a promising strategy to mitigate aging-induced declines in tissue regeneration.

Temperature and Growth Selection Effects on Proliferation, Differentiation, and Adipogenic Potential of Turkey Myogenic Satellite Cells Through Frizzled-7-Mediated Wnt Planar Cell Polarity Pathway

Satellite cells (SCs) are a heterogeneous population of multipotential stem cells. During the first week after hatch, satellite cell function and fate are sensitive to temperature. Wingless-type mouse mammary tumor virus integration site family/planar cell polarity (Wnt/PCP) signaling pathway is significantly affected by thermal stress in turkey pectoralis major (p. major) muscle SCs. This pathway regulates the activity of SCs through a frizzled-7 (Fzd7) cell surface receptor and two intracellular effectors, rho-associated protein kinase (ROCK) and c-Jun. The objective of the present study was to determine the effects of thermal stress, growth selection, and the Fzd7-mediated Wnt/PCP pathway on proliferation, myogenic differentiation, lipid accumulation, and expression of myogenic and adipogenic regulatory genes. These effects were evaluated in SCs isolated from the p. major muscle of 1-week faster-growing modern commercial (NC) line of turkeys as compared to SCs of a slower-growing historic Randombred Control Line 2 (RBC2) turkey line. Heat stress (43°C) increased phosphorylation of both ROCK and c-Jun with greater increases observed in the RBC2 line. Cold stress (33°C) had an inhibitory effect on both ROCK and c-Jun phosphorylation with the NC line showing greater reductions. Knockdown of the expression of Fzd7 decreased proliferation, differentiation, and expression of myogenic regulatory genes: myoblast determination factor-1 and myogenin in both lines. Both lipid accumulation and expression of adipogenic regulatory genes: peroxisome proliferator-activated receptor-γ, CCAAT/enhancer-binding protein-β, and neuropeptide-Y were suppressed with the Fzd7 knockdown. The RBC2 line was more dependent on the Fzd7-mediated Wnt/PCP pathway for proliferation, differentiation, and lipid accumulation compared to the NC line. Thus, thermal stress may affect poultry breast muscle growth potential and protein to fat ratio by altering function and fate of SCs through the Fzd7-mediated Wnt/PCP pathway in a growth-dependent manner.

Insights into molecular pathways and fatty acid membrane composition during the temperature stress response in the murine C2C12 cell model

Daily and seasonal temperature fluctuations are inevitable due to climate change, which highlights the importance of studying the detrimental effects of temperature fluctuations on the health, productivity, and product quality of farm animals. Muscle membrane composition and the molecular signals are vital for muscle cell differentiation and muscle growth, but their response to temperature stress is not well characterized. Temperature changes can lead to modification of membrane components of the cell, which may affect its surroundings and intracellular signaling pathways. Using C2C12 myoblast cells as a model of skeletal muscle development, this study was designed to investigate the effects of high temperature (39 °C and 41 °C) and low temperature (35 °C) on molecular pathways in the cells as well as the cell membrane fatty acid composition. Our results show that several genes were differentially expressed in C2C12 cells cultured under heat or cold stress, and these genes were enriched important KEGG pathways including PI3K-Akt signaling pathway, lysosome and HIF- signaling pathway, Wnt signaling pathway and AMPK signaling pathway. Our analysis further reveals that several membrane transporters and genes involved in lipid metabolism and fatty acid elongation were also differentially expressed in C2C12 cells cultured under high or low temperature. Additionally, temperature stress shifts the fatty acid composition in the cell membranes, including the proportion of saturated, monounsaturated and polyunsaturated fatty acids. This study revealed an interference between fatty acid composition in the membranes and changing molecular pathways including lipid metabolism and fatty acids elongation mediated under thermal stress. These findings will reinforce a better understanding of the adaptive mechanisms in skeletal muscle under temperature stress.