| Follistatin(FST)is expressed in bone and muscle tissues and can regulate their growth and development in autocrine and paracrine manners.FST,as a secreted factor expressed by both tissues,may play an important role in their cooperative development,but there is a lack of relevant research reports.Therefore,this study reconstitute duck FST protein in vitro and then injected different concentrations of recombinant duck FST recombinant protein into duck breast muscle to establish an experimental model to explore the effects of FST on sternum and breast muscle development at different stages as well as the possible regulatory mechanisms.The main results were listed as follows:(1)In this study,the recombinant duck FST protein was successfully obtained by constructing a prokaryotic expression vector.The purification and identification results showed that there was a single band between 50 and 75 k Da,and the recombinant protein activity was 43.359U/L.(2)After FST injection,the dressed percentage and percentage of eviscerated yield of the FST10 group and the dressed percentage of the FST100 group were significantly increased at 6-week-old(P<0.05).The dressed percentage of the 7-weekold FST50 group and the percentage of eviscerated yield of the FST100 group significantly decreased(P<0.05).At 9 weeks of age,the live weight and daily weight gain of the FST10 group,as well as the daily weight gain and body oblique length of the FST50 group were significantly increased,but the dressed percentage and percentage of eviscerated yield of the FST10 group and FST100 group were significantly decreased(P<0.05).(3)After FST injection,the breast muscle weight(rate)of the FST100 group increased at 6-week-old(0.05<P<0.1).The 7-week-old and 9-week-old FST groups of different doses had a slight decrease in breast muscle weight(rate).There was no significant change in sternum development in the FST treatment group at 6-week-old.The sternum weight and sternum area of the 7-week-old FST10 group decreased(0.05<P<0.1),and the sternum area and posterior protrusion distance of the 9-week-old FST50 group significantly increased(P<0.05).(4)Results from HE staining of breast muscle and sternum tissue sections showed that compared with the control group,the muscle fiber diameter and cross-section of the 7-week-old FST treatment group extremely significant dereased(P<0.01),and the muscle fiber diameter and cross-section of the 9-week-old FST treatment group extremely significant increased(P<0.01).The sternum thickness and sternum crosssection of the 7-week-old FST treatment group extremely significant decreased(P<0.01),and the sternum thickness of the 9-week-old FST treatment group extremely significant increased(P<0.01),but the trabecular bone area and unit area and the number of osteoblasts per unit area showed a downward trend(P>0.05).(5)The quantitative real-time PCR results showed that at 7 weeks of age,the expression levels of COL10A1 and VEGF in the sternum of the FST treatment group extremely significant increased(P<0.01),and the expression levels of COL2A1 and Runx2 extremely significant decreased(P<0.01).The expression of Pax7 and MAFbx in the breast muscles extremely significant increased(P<0.01).At 9 weeks of age,the expression levels of ALP,COL1A2,CTSK,and MMP9 in the sternum of the FST treatment group extremely significant decreased(P<0.01),while the expression levels of Pax7,MyoD,mTOR,and Mur F in the breast muscles increased(P>0.05).(6)After FST injection,there were significant changes in the TGF-β/ActA and PI3K/AKT pathway-related genes in sternum and breast muscles at 7 and 9 weeks of age,indicating that FST may act through the TGF-β/ActA and PI3K/AKT pathways to affect the development of the sternum and breast muscles.In summary,the effects of FST on the development of sternum and breast muscles of ducks at different ages are both developmental stage-and dose-depenent,which may regulate the development of duck sternal and breast muscles through the TGF-β/ActA and PI3K/AKT pathways. |
PDF Full Text Request