Differential expression patterns of myogenic regulatory factors in the postnatal longissimus dorsi muscle of Jeju Native Pig and Berkshire breeds along with their co-expression with Pax7

BACKGROUND: Myogenic regulatory factors (MRFs) such as MyoD, Myf6 and Myf5 play a vital role in the growth and development of muscles. Jeju Native Pig (JNP) is the top ranker in Korea amongst the indigenous livestock reared for meat purpose. Few studies covering transcript abundance of the MRFs and related to their co-expression with Pax7 in JNP have been conducted. Despite having better quality pork, JNP does not have a comparative growth rate with respect to western breeds. Therefore, the present study was designed with the objective to study the relative transcript levels of MRFs in the postnatal myogenesis of longissimus dorsi muscles in JNP and Berkshire breeds. RESULTS: Relative transcript levels were analyzed by qRT-PCR and blot expression analysis through Western blotting. Immunocytochemistry was performed to analyze their expressions at cellular levels. ToppCluster aided in the analysis of gene ontology of biological processes. The quantitative transcript levels of MyoD and Pax7 were significantly (P < 0.05) higher in Berkshire than in JNP. Myotube formation was observed under the co-expression of MyoD and Pax7. ToppCluster helped in the understanding of the linking of biological processes of the MRFs with the different signaling pathways. MyBPH had significantly (P < 0.05) high transcript levels during the chosen age groups in JNP than Berkshire. CONCLUSIONS: The current study can be helpful in understanding the genetic basis for myogenesis in postnatal stage. Moreover, it can act as stepping stone for the identification of marker genes related to body growth and meat quality in JNP.

Evaluation of skeletal muscle regeneration in experimental model after malnutrition / Avaliação da regeneração do músculo esquelético em modelo experimental após desnutrição

Abstract The aim of this study was to analyze muscle regeneration after cryoinjury in the tibialis anterior muscle of young rats that were malnourished and then recovered. Forty Wistar rats were divided into a nourished group that received a normal protein diet (14% casein) for 90 days and a malnourished and recovered rats group (MR) that was submitted to 45 days of malnutrition with a hypoproteic diet (6% casein) followed by 45 days of a normal protein diet (14% casein). After the recovery period, all of the animals underwent cryoinjury in the right tibialis anterior muscle and euthanasia after 7, 14 and 21 days. The amount of connective tissue and the inflammation area was higher in the malnutrition recovered injury MR group (MRI) at 14 days post-injury (p < 0.05). Additionally, the cross-sectional area (CSA) of the regenerated fibers was decreased in the MRI (p < 0.05). The MyoD and myogenin protein levels were higher in the nourished injury group. Similar levels of TGF-β1 were found between groups. The proposed malnutrition protocol was effective in showing delayed changes in the regeneration process of the tibialis anterior muscle of young rats. Furthermore, we observed a delay in muscle repair even after nutritional recovery.

Resumo O objetivo do presente estudo foi analisar a regeneração muscular após criolesão no músculo tibial anterior de ratos jovens desnutridos e recuperados. Foram utilizados 40 ratos da linhagem Wistar, divididos em 2 grupos: ratos nutridos receberam dieta normoproteica (14% de caseína) por 90 dias; e ratos desnutridos e recuperado submetidos a duas fases nutricionais pós-desmame, correspondendo a 45 dias de desnutrição com dieta hipoproteica (6% caseína), seguida por 45 dias de dieta normoproteica (14% caseína). Ao completar a fase de recuperação, todos os animais foram submetidos à criolesão no músculo tibial anterior direito e a eutanasia ocorreu 7, 14 e 21 dias após a lesão. A quantidade de tecido conjuntivo e a área de inflamação 14 dias pós-lesão foi maior no grupo desnutrido, recuperado e lesado (MRI – malnourished, recovered and injured group) (p < 0,05). A área de secção transversa (AST) das fibras regeneradas do grupo MRI foi menor (p < 0,05). O conteúdo das proteínas MyoD e Miogenina foi maior no grupo nutridos e lesados. A citocina TGF-β1 não apresentou diferença entre os grupos. O protocolo proposto foi eficaz para demonstrar alterações no processo de regeneração do músculo tibial anterior de ratos jovens, atrasando o reparo muscular mesmo após a recuperação nutricional.

Effects of isoflurane anenthesia on myocyte enhancer factor 2 signaling pathway in neonatal rat hippocampus / 中华麻醉学杂志

Objective To investigate the effects of isoflurane anenthesia on myocyte enhancer factor 2(MEF2) signaling pathway in neonatal rat hippocampus. Methods Twenty-four 5-day-old SD rats of both sexes,weighing 10-13 g, were randomly divided into 2 groups ( n = 12 each): control group (group C) and isoflurane group (group I). In group I, 1.5% isoflurane in 100% O2 was inhaled for 6 h. Group C received no treatment.Three rata in each group were sacrificed at 2, 4, 6 h of isoflurane anenthesia and 24 h after isoflurane anenthesia (T1-4), and the hippocampi removed for determination of MEF2 mRNA, synGAP Ⅰ mRNA, Arc mRNA and synapsinⅠ mRNA expression (by PT-PCR) and synapsin Ⅰ protein expression (by Western blot).Results Compared with group C, the expression of MEF2 mRNA, synGAP Ⅰ mRNA, Arc mRNA and synapsin Ⅰ mRNA at T1-3 and synapsin Ⅰ protein at T2-4 was up-regulated in group I ( P ＜ 0.05). Conclusion Inhalation of anaesthetic concentration of isoflurane may affect synapse formation during the development of central nervous system by actirating hippocampal MEF2 signaling pathways in neonatal rats.

EFFECTS OF MRF4 TRANSFECTION ON DIFFERENTIATION AND EXPRESSION OF MYOGENIC REGULATORY FACTORS IN CULTERED HUMAN RHABDOMYOSARCOMA RD CELLS / 解放军医学杂志

To study the effects of MRF4 transfection on differentiation and expression of myogenic regulatory factors of human rhabdomyosarcoma RD cells, the plasmid-MRF4 cDNA was transfected into cultured rhabdomyosarcoma RD cells with lipofectin method. The myogenic regulatory factors MRF4 and MyoD mRNA were measured with in situ hybridization and the expressions of myosin heavy chain(MHC) and a-actin in the cells were assayed with immunocytochemical method. The cell growth and morphology were observed at the same time. It was found that the morphology of differentiation increased and the growth was suppressed in RD cells after transfection. The expression of MHC and a-actin were significantly increased in RD cells after transfection, while the expressions of MRF4 and MyoD mRNA were up-regulated. It is suggested that transfection of MRF4 can induce differentiation of RD cells and up-regulate the expression of MyoD.