Environmental hypoxia induces apoptosis in large yellow croaker Larimichthys crocea via both intrinsic and extrinsic pathways

Hypoxia has become an unfavorable factor affecting the sustainable development of the large yellow croaker Larimichthys crocea,an economically important mariculture fish in China.Apoptosis is a consequence of hypoxia on fish.However,the effects of hypoxia stress on apoptosis in L.crocea remain largely unknown.We investigated the effect of environmental hypoxia on apoptosis in L.crocea.Results show that hypoxia induced apoptosis in L.crocea both in vivo and in vitro.The mitochondrial membrane potential was significantly reduced in large yellow croaker fry(LYCF)cells.The expression levels of Bcell lymphoma/leukemia-2(Bcl-2)m RNA and protein were also significantly decreased in the liver and LYCF cells during 96 h and 48 h of hypoxia stress,respectively,whereas the expression level of Bcl-2 associated X(Bax)mRNA,Casp3 mRNA,and activity of caspase-3/7/9 were significantly increased,indicating that hypoxia induced caspase-dependent intrinsic apoptosis in L.crocea.The expression level of the apoptosis-inducing factor(AIF)protein was significantly increased in the liver and LYCF cells.The level of AIF protein was significantly decreased in the cytoplasm but increased in the nuclei of L.crocea,demonstrating that hypoxia induced the AIF-mediated caspase-independent intrinsic apoptosis.In addition,the activity of caspase-8 was significantly increased,indicating that hypoxia stress induced extrinsic apoptosis in L.crocea.Therefore,hypoxia induced apoptosis in L.crocea through both the intrinsic and extrinsic pathways.The present study accumulated basic biological information to help elucidate the mechanism of hypoxia response in marine fish.

Effect of fasting on protein metabolism in muscle tissue of Larimichthys crocea revealed by transcriptome and proteome

The large yellow croaker(Larimichthys crocea)is an important mariculture fish in China.Farmed large yellow croaker undergo periods of fasting to adapt to the environment or to improve meat quality.To better understand the physiological responses of their muscle tissues to fasting stresses,we analyzed the transcriptomes and proteome s of both normally-fed and fasting fish groups and identified 7578 differentially expressed genes(DEGs)and 297 differentially expressed proteins(DEPs)among them.Gene ontology and KEGG analysis showed that the enriched biological pathways were mainly involved in various synthetic and catabolic pathways,especially the protein metabolism.Based on the omics data,nine DEGs related to muscle composition(CAN3,MYL3,and TNNC2),growth(MSTN and MYF5),autophagy(TSC2 and ULK1),and the ubiquitin proteasome pathway(PRS6 B and UCHL3)were examined using qPCR.In response to fasting stress,MYL3 and TNNC2 were significantly downregulated,while genes associated with autophagy and the ubiquitin proteasome pathway were significantly upregulated.In re sponse to fasting stres s,MYL3,TNNC2,and MYF5 positively correlated with muscle growth were significantly downregulated,while inhibiting growth MSTN and genes associated with autophagy and the ubiquitin proteasome pathways were significantly upregulated.These results clarify the effects of fasting on metabolic changes in their muscle components and growth at the molecular level.

Biomimetic strategies for tendon/ligament-to-bone interface regeneration

Tendon/ligament-to-bone healing poses a formidable clinical challenge due to the complex structure,composition,cell population and mechanics of the interface.With rapid advances in tissue engineering,a variety of strategies including advanced biomaterials,bioactive growth factors and multiple stem cell lineages have been developed to facilitate the healing of this tissue interface.Given the important role of structure-function relationship,the review begins with a brief description of enthesis structure and composition.Next,the biomimetic biomaterials including decellularized extracellular matrix scaffolds and synthetic-/natural-origin scaffolds are critically examined.Then,the key roles of the combination,concentration and location of various growth factors in biomimetic application are emphasized.After that,the various stem cell sources and culture systems are described.At last,we discuss unmet needs and existing challenges in the ideal strategies for tendon/ligament-to-bone regeneration and highlight emerging strategies in the field.

Promoting musculoskeletal system soft tissue regeneration by biomaterial-mediated modulation of macrophage polarization

Musculoskeletal disorders are common in clinical practice.Repairing critical-sized defects in musculoskeletal systems remains a challenge for researchers and surgeons,requiring the application of tissue engineering biomaterials.Successful application depends on the response of the host tissue to the biomaterial and specific healing process of each anatomical structure.The commonly-held view is that biomaterials should be biocompatible to minimize local host immune response.However,a growing number of studies have shown that active modulation of the immune cells,particularly macrophages,via biomaterials is an effective way to control immune response and promote tissue regeneration as well as biomaterial integration.Therefore,we critically review the role of macrophages in the repair of injured musculoskeletal system soft tissues,which have relatively poor regenerative capacities,as well as discuss further enhancement of target tissue regeneration via modulation of macrophage polarization by biomaterial-mediated immunomodulation(biomaterial properties and delivery systems).This active regulation approach rather than passive-evade strategy maximizes the potential of biomaterials to promote musculoskeletal system soft tissue regeneration and provides alternative therapeutic options for repairing critical-sized defects.