Hif-1α/Hsf1/Hsp70 signaling pathway regulates redox homeostasis and apoptosis in large yellow croaker ( Larimichthys crocea) under environmental hypoxia

Oxygen is an essential molecule for animal respiration, growth, and survival. Unlike in terrestrial environments, contamination and climate change have led to the frequent occurrence of hypoxia in aquatic environments, thus impacting aquatic animal survival. However, the adaptative mechanisms underlying fish responses to environmental hypoxia remain largely unknown. Here, we used large yellow croaker (Larimichthys crocea) and large yellow croaker fry (LYCF) cells to investigate the roles of the Hif-1α/Hsf1/Hsp70 signaling pathway in the regulation of cellular redox homeostasis, and apoptosis. We confirmed that hypoxia induced the expression of Hif-1α, Hsf1, and Hsp70 in vivo and in vitro. Genetic Hsp70 knockdown/overexpression indicated that Hsp70 was required for maintaining redox homeostasis and resisting oxidative stress in LYCF cells under hypoxic stress. Hsp70 inhibited caspase-dependent intrinsic apoptosis by maintaining normal mitochondrial membrane potential, enhancing Bcl-2 mRNA and protein expression, inhibiting Bax and caspase3 mRNA expression, and suppressing caspase-3 and caspase-9 activation. Hsp70 suppressed caspase-independent intrinsic apoptosis by inhibiting nuclear translocation of apoptosis-inducing factor (AIF) and disturbed extrinsic apoptosis by inactivating caspase-8. Genetic knockdown/overexpression of Hif-1α and dual-luciferase reporter assay indicated that Hif-1α activated the Hsf1 DNA promoter and enhanced Hsf1 mRNA transcription. Hsf1 enhanced Hsp70 mRNA transcription in a similar manner. In summary, the Hif-1α/Hsf1/Hsp70 signaling pathway plays an important role in regulating redox homeostasis and anti-apoptosis in L. crocea under hypoxic stress.

Scavenging reactive oxygen species is a potential strategy to protect Larimichthys crocea against environmental hypoxia by mitigating oxidative stress

The large yellow croaker (Larimichthys crocea), which is an economically important mariculture fish in China, is often exposed to environmental hypoxia. Reactive oxygen species (ROS) homeostasis is essential for the maintenance of normal physiological conditions in an organism. Direct evidence that environmental hypoxia leads to ROS overproduction is scarce in marine fish. Furthermore, the sources of ROS overproduction in marine fish under hypoxic stress are poorly known. In this study, we investigated the effects of hypoxia on redox homeostasis in L. crocea and the impact of impaired redox homeostasis on fish. We first confirmed that hypoxia drove ROS production mainly via the mitochondrial electron transport chain and NADPH oxidase complex pathways in L. crocea and its cell line (large yellow croaker fry (LYCF) cells). We subsequently detected a marked increase in the antioxidant systems of the fish. However, imbalance between the pro-oxidation and antioxidation systems ultimately led to excessive ROS and oxidative stress. Cell viability showed a remarkable decrease while oxidative indicators, such as malondialdehyde, protein carbonylation, and 8-hydroxy-2 deoxyguanosine, showed a significant increase after hypoxia, accompanied by tissue damage. N-acetylcysteine (NAC) reduced ROS levels, alleviated oxidative damage, and improved cell viability in vitro. Appropriate uptake of ROS scavengers (e.g., NAC and elamipretide Szeto-Schiller-31) and inhibitors (e.g., apocynin, diphenylene iodonium, and 5-hydroxydecanoate) may be effective at overcoming hypoxic toxicity. Our findings highlight previously unstudied strategies of hypoxic toxicity resistance in marine fish.

ECM remodeling in stem cell culture: a potential target for regulating stem cell function

Stem cells (SCs) hold great potential for regenerative medicine, tissue engineering and cell therapy. The clinical applications of SCs require both high quality and quantity of transplantable cells. However, during conventional in vitro expansion, SCs tend to lose properties that make them amenable for cell therapies. Extracellular matrix (ECM) serves an essential regulatory part in the growth, differentiation and homeostasis of all cells in vivo. when signals transmitted to cells, they do not respond passively. Many cell types can remodel pericellular matrix to meet their specific needs. This reciprocal cell-ECM interaction is crucial for the conservation of cell and tissue functions and homeostasis. In vitro ECM remodeling also plays a key role in regulating the lineage fate of SCs. A deeper understanding of in vitro ECM remodeling may provide new perspectives for the maintenance of SC function. In this review, we critically examined three ways that cells can be used to influence the pericellular matrix: (i) exerting tensile force on the ECM, (ii) secreting a variety of ECM proteins, and (iii) degrading the surrounding matrix, and its impact on SC lineage fate. Finally, we describe the deficiencies of current studies and what needs to be done next to further understand the role of ECM remodeling in ex vivo SC cultures.

Physical Microenvironment-Based Inducible Scaffold for Stem Cell Differentiation and Tendon Regeneration

Tendon injuries are common musculoskeletal system disorders, but the tendons have poor regeneration ability. To address this issue, tendon tissue engineering provides potential strategies for future therapeutic treatment. Elements of the physical microenvironment, such as the mechanical force and surface topography, play a vital role in regulating stem cell fate, enhancing the differentiation efficiency of seed cells in tendon tissue engineering. Various inducible scaffolds have been widely explored for tendon regeneration, and scaffold-enhancing modifications have been extensively studied. In this review, we systematically summarize the effects of the physical microenvironment on stem cell differentiation and tendon regeneration; we also provide an overview of the inducible scaffolds for stem cell tenogenic differentiation. Finally, we suggest some potential scaffold-based therapies for tendon injuries, presenting an interesting perspective on tendon regenerative medicine.

Cepharanthine Prevents Estrogen Deficiency-Induced Bone Loss by Inhibiting Bone Resorption

Osteoporosis is a common health problem worldwide caused by an imbalance of bone formation vs. bone resorption. However, current therapeutic approaches aimed at enhancing bone formation or suppressing bone resorption still have some limitations. In this study, we demonstrated for the first time that cepharanthine (CEP, derived from Stephania cepharantha Hayata) exerted a protective effect on estrogen deficiency-induced bone loss. This protective effect was confirmed to be achieved through inhibition of bone resorption in vivo, rather than through enhancement of bone formation in vivo. Furthermore, the in vitro study revealed that CEP attenuated receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast formation, and suppressed bone resorption by impairing the c-Jun N-terminal kinase (JNK) and phosphatidylinositol 3-kinase (PI3K)-AKT signaling pathways. The inhibitory effect of CEP could be partly reversed by treatment with anisomycin (a JNK and p38 agonist) and/or SC79 (an AKT agonist) in vitro. Our results thus indicated that CEP could prevent estrogen deficiency-induced bone loss by inhibiting osteoclastogenesis. Hence, CEP might be a novel therapeutic agent for anti-osteoporosis therapy.

Sophocarpine attenuates wear particle-induced implant loosening by inhibiting osteoclastogenesis and bone resorption via suppression of the NF-κB signalling pathway in a rat model

BACKGROUND AND PURPOSE

Aseptic prosthesis loosening, caused by wear particles, is one of the most common causes of arthroplasty failure. Extensive and over-activated osteoclast formation and physiological functioning are regarded as the mechanism of prosthesis loosening. Therapeutic modalities based on inhibiting osteoclast formation and bone resorption have been confirmed to be an effective way of preventing aseptic prosthesis loosening. In this study, we have investigated the effects of sophocarpine (SPC, derived from Sophora flavescens) on preventing implant loosening and further explored the underlying mechanisms.

EXPERIMENTAL APPROACH

The effects of SPC in inhibiting osteoclastogenesis and bone resorption were evaluated in osteoclast formation, induced in vitro by the receptor activator of NF-κB ligand (RANKL). A rat femoral particle-induced peri-implant osteolysis model was established. Subsequently, micro-CT, histology, mechanical testing and bone turnover were used to assess the effects of SPC in preventing implant loosening.

KEY RESULTS

In vitro, we found that SPC suppressed osteoclast formation, bone resorption, F-actin ring formation and osteoclast-associated gene expression by inhibiting NF-κB signalling, specifically by targeting IκB kinases. Our in vivo study showed that SPC prevented particle-induced prosthesis loosening by inhibiting osteoclast formation, resulting in reduced periprosthetic bone loss, diminished pseudomembrane formation, improved bone-implant contact, reduced bone resorption-related turnover and enhanced stability of implants. Inhibition of NF-κB signalling by SPC was confirmed in vivo.

CONCLUSION AND IMPLICATIONS

SPC can prevent implant loosening through inhibiting osteoclast formation and bone resorption. Thus, SPC might be a novel therapeutic agent to prevent prosthesis loosening and for osteolytic diseases.

Physiological responses and changes in gene expression in the large yellow croaker Larimichthys crocea following exposure to hypoxia

Organisms at all levels of evolutionary complexity react to hypoxic stress. To clarify the effects of acute hypoxia on physiological and biochemical responses of Larimichthys crocea, we measured the activity levels of the antioxidant enzymes superoxide dismutase and catalase, hemoglobin concentration, functional indices of the liver (aspartate transaminase, alanine transaminase), heart (phosphocreatine kinase), and immune system (alkaline phosphatase), as well as mRNA expression levels of the immunity-related genes Hsp70 and HIF-1α at different time points of hypoxic. In addition, liver, gill, and kidney samples were histologically analyzed. We found that hemoglobin concentration and all enzyme activities increased during hypoxia, although these effects were transient and most indices returned to basal levels thereafter. The extent of the increase in the parameter values was inversely proportional to the dissolved oxygen content. Hsp70 and HIF-1α mRNA expression levels increased significantly in the blood, liver, gills, and kidneys following exposure to hypoxia, which may play an important role in protecting fish against oxidative damage. However, we found histological evidence of hypoxia-induced injuries to the gills, liver, and kidneys, which are involved in breathing, detoxification, and osmotic balance maintenance, respectively. Thus, despite the upregulation of defensive mechanisms, acute hypoxia still caused irreversible damage of organs. In conclusion, we observed that, in response to acute hypoxic stress, L. crocea enhances immune defensive function and antioxidant capacity. A better understanding of the regulation of the molecular anti-hypoxia mechanisms can help speeding up the selective breeding of hypoxia-tolerant L. crocea.

Pharmacological Regulation of In Situ Tissue Stem Cells Differentiation for Soft Tissue Calcification Treatment

Calcification of soft tissues, such as heart valves and tendons, is a common clinical problem with limited therapeutics. Tissue specific stem/progenitor cells proliferate to repopulate injured tissues. But some of them become divergent to the direction of ossification in the local pathological microenvironment, thereby representing a cellular target for pharmacological approach. We observed that HIF-2alpha (encoded by EPAS1 inclined form) signaling is markedly activated within stem/progenitor cells recruited at calcified sites of diseased human tendons and heart valves. Proinflammatory microenvironment, rather than hypoxia, is correlated with HIF-2alpha activation and promoted osteochondrogenic differentiation of tendon stem/progenitor cells (TSPCs). Abnormal upregulation of HIF-2alpha served as a key switch to direct TSPCs differentiation into osteochondral-lineage rather than teno-lineage. Notably, Scleraxis (Scx), an essential tendon specific transcription factor, was suppressed on constitutive activation of HIF-2alpha and mediated the effect of HIF-2alpha on TSPCs fate decision. Moreover, pharmacological inhibition of HIF-2alpha with digoxin, which is a widely utilized drug, can efficiently inhibit calcification and enhance tenogenesis in vitro and in the Achilles's tendinopathy model. Taken together, these findings reveal the significant role of the tissue stem/progenitor cells fate decision and suggest that pharmacological regulation of HIF-2alpha function is a promising approach for soft tissue calcification treatment.

Single-cell analysis reveals a nestin+ tendon stem/progenitor cell population with strong tenogenic potentiality

The repair of injured tendons remains a formidable clinical challenge because of our limited understanding of tendon stem cells and the regulation of tenogenesis. With single-cell analysis to characterize the gene expression profiles of individual cells isolated from tendon tissue, a subpopulation of nestin⁺ tendon stem/progenitor cells (TSPCs) was identified within the tendon cell population. Using Gene Expression Omnibus datasets and immunofluorescence assays, we found that nestin expression was activated at specific stages of tendon development. Moreover, isolated nestin⁺ TSPCs exhibited superior tenogenic capacity compared to nestin^- TSPCs. Knockdown of nestin expression in TSPCs suppressed their clonogenic capacity and reduced their tenogenic potential significantly both in vitro and in vivo. Hence, these findings provide new insights into the identification of subpopulations of TSPCs and illustrate the crucial roles of nestin in TSPC fate decisions and phenotype maintenance, which may assist in future therapeutic strategies to treat tendon disease.

Scleraxis-overexpressed human embryonic stem cell-derived mesenchymal stem cells for tendon tissue engineering with knitted silk-collagen scaffold

AIM

Despite our previous study that demonstrates that human embryonic stem cells (hESCs) can be used as seed cells for tendon tissue engineering after stepwise induction, suboptimal tendon regeneration implies that a new strategy needs to be developed for tendon repair. We investigated whether overexpression of the tendon-specific transcription factor scleraxis (SCX) in hESC-derived mesenchymal stem cells (hESC-MSCs) together with knitted silk-collagen sponge scaffold could promote tendon regeneration.

METHODS AND RESULTS

hESCs were initially differentiated into MSCs and then engineered with scleraxis (SCX+hESC-MSCs). Engineered tendons were constructed with SCX+hESC-MSCs and a knitted silk-collagen sponge scaffold and then mechanical stress was applied. SCX elevated tendon gene expression in hESC-MSCs and concomitantly attenuated their adipogenic and chondrogenic potential. Mechanical stress further augmented the expression of tendon-specific genes in SCX+hESC-MSC-engineered tendon. Moreover, in vivo mechanical stimulation promoted the alignment of cells and increased the diameter of collagen fibers after ectopic transplantation. In the in vivo tendon repair model, the SCX+hESC-MSC-engineered tendon enhanced the regeneration process as shown by histological scores and superior mechanical performance compared with control cells, especially at early stages.

CONCLUSION

Our study offers new evidence concerning the roles of SCX in tendon differentiation and regeneration. We demonstrated a novel strategy of combining hESCs, genetic engineering, and tissue-engineering principles for tendon regeneration, which are important for the future application of hESCs and silk scaffolds for tendon repair.

Sequential deletion of Pichia pastoris genes by a self-excisable cassette

A rapid and convenient method is presented for unmarked gene deletions in Pichia pastoris. Cre/mutated lox system, Zeocin(®) (Invitrogen) resistance marker and homologous arms were spliced together by fusion PCR to generate the gene disruption cassettes (homologous region-lox71-Cre-ZeoR-lox66-homologous region), which could be integrated into the P. pastoris genome via homologous recombination. After transferring double-cross-over recombinants to methanol induction medium, transient expression of Cre recombinase caused the recombination of lox71-Cre-ZeoR-lox66 fragment into a double-mutant lox72 site, thus excising the Cre-ZeoR cassette from the P. pastoris genome. As the double-mutant lox72 site displays strongly reduced binding affinity for Cre recombinase, this method could be used sequentially to disrupt P. pastoris genes without introducing selectable markers. The effectiveness of this strategy was verified by introducing both single and double gene deletions into the P. pastoris genome.

[Knockdown of cyclin A2 expression by small interfering RNA in MG-63 cells]

OBJECTIVE

To study the inhibitory effect of small interference RNA (siRNA) targeting cyclin A2 gene on the growth of osteosarcoma MG-63 and human normal skin fibroblast HSF cells and to explore whether cyclin A2 siRNAs could become a useful tool in the treatment of osteosarcoma.

METHODS

Three pairs of siRNAs targeting cyclin A2 mRNA and a pair of nonsense siRNA were designed according to the current criteria. SiRNAs were chemically synthesized and purified. The siRNAs were transfected into MG-63 cells and HSF cells via oligofectamine. The cells transfected with nonsense siRNA served as negative control group and those only treated with PBS as blank control group. Quantitative fluorescence RT-PCR, Western-blot, MTT assay, reverse transcriptase (RT)-PCR, flow cytometry and clone forming test were employed to evaluate the efficacy of RNA interference. At the same time, the mRNA expression of PCNA and cyclin B1 in siRNA-treated MG-63 cells were examined.

RESULTS

Although all three siRNAs could reduce the cyclin A2 expression, siRNA, appeared to be the most effective. After 48 h treatment with siRNA1, cyclin A2 mRNA and protein expression in MG-63 cells was significantly reduced by nearly 80% as compared with that of the blank control group, whereas the negative and blank control groups had similar expression levels. MG-63 cells treated with siRNA1 were arrested at G0/G1 phase by 80.1% and the proliferation of these tumor cells was suppressed 48 h after transfection. Furthermore, MG-63 cells showed a decreased colony forming ability after siRNA1 treatment. In addition, the cyclin A2-depleted MG-63 cells showed decreased levels of PCNA and cyclin B1. In contrast, although cyclin A2 expression in HSF reduced by nearly 60% after treatment by siRNA1 for 48h, these cells exhibited only a slight change in cell cycling, and neither clear inhibition of proliferation nor impaired colony forming ability was observed.

CONCLUSION

Cyclin A2 is critical for proliferation of MG-63 cells. Cyclin A2-siRNAs can induce obvious inhibition of cyclin A2 mRNA and protein expression in MG-63 and HSF cells, which consequently down-regulate the proliferation of MG-63 cells. There is little effect on the proliferation of siRNA-treated HSF cells. Those results indicate that siRNAs against cyclin A2 may become a potential antiproliferative tool in future antitumor therapy.

[Growth inhibition of MG-63 cells by cyclin A2 gene-specific small interfering RNA]

OBJECTIVE

To study the impact of small interference RNA (siRNA) targeting cyclin A2 gene on the growth of MG-63 and HSF cells and to explore whether cyclin A2 siRNAs could become a useful tool in the treatment of osteosarcoma.

METHODS

One pair of siRNA targeting the cyclin A2 mRNA and a pair of nonsense siRNA were designed according the current criteria. SiRNA was chemically synthesized and purified. The siRNA was transfected into osteosarcoma cell line MG-63 and normal human skin fibroblast (HSF) cells via oligofectamine. Cells transfected with nonsense siRNA served as the negative control and those only treated with PBS as the blank control group. Quantitative fluorescence RT-PCR, Western-blot, MTT assay, reverse transcriptase (RT)-PCR, flow cytometry and colony-forming test were employed to evaluate the efficacy of RNA interference. At the same time, the mRNA expression of PCNA and cyclin B1 in siRNA treated MG-63 cells were examined.

RESULTS

1 nmol/L, 10 nmol/L, 50 nmol/L and 100 nmol/L cyclin A2-siRNA can reduced cyclin A2 mRNA and protein expression respectively by 9.43%, 56.35%, 79.17% and 84.30% as compared with that of the blank control group, whereas the negative and blank control groups had similar expression levels. After 48 h treatment with 10 nmol/L siRNA, MG-63 cells were arrested in G0/G1 phase and the proliferation of this tumor cell was suppressed by 39.06% 48 h after transfection. Furthermore, the treated MG-63 cells showed less colony-forming ability. Increasing the siRNA concentration to 50 nmol/L can further inhibit the proliferation of MG-63 cells by 54.94%. In addition, the cyclin A2-depleted MG-63 cells showed decreased levels of PCNA and cyclin B1. In contrast, although cyclin A2 mRNA and protein expression in HSF reduced 58.13% 48 h after treatment by 50 nmol/L siRNA, these cells exhibited only a slight change in cell cycle, and no clear inhibition of proliferation and impaired plate colony-forming ability was observed.

CONCLUSION

Cyclin A2 gene maybe served as a potential target for tumor therapy. RNA interference induces obvious inhibition of cyclin A2 mRNA and protein expression in MG-63 and HSF cells, which consequently downregulate the proliferation of MG-63 cells. There is few inhibitory effect on the proliferation by siRNAs for HSF cells. These results indicate that siRNAs against cyclin A2 could become a potential antiproliferative tool in future antitumor therapy.

Bcl-2 antisense oligodeoxynucleotide increases the sensitivity of leukemic cells to arsenic trioxide

Cell culture, tissue chemistry and flow cytometry were used to determine whether antisense bcl-2 oligodeoxynucleotides enhanced the sensitivity of leukemia cells to arsenic trioxide. A combination of arsenic trioxide with antisense bcl-2 oligodeoxynucleotides inhibited cell growth, induced apoptosis and induced bcl-2 protein expression in K562 and NB4 leukemic cells more significantly than either arsenic trioxide or the oligodeoxynucleotides on their own (P<0.01). Thus, bcl-2 antisense oligodeoxynucleotides increase the sensitivity of leukemic cells to arsenic trioxide. Combined use of the two agents could be a novel and attractive strategy in leukemia treatment.

[Graft-versus-host disease and xenotransplantation]

OBJECTIVE

The pathogenesis, mechanism, manifestation and diagnosis of graft-versus-host disease(GVHD) are reviewed in this article.

METHODS

The relevant articles in recent public magazines were reviewed and summarized.

RESULTS

It was indicated that GVHD occurred in the conditioned recipients in animal experiments and clinical transplantations. Humoral and cellular factors were involved in GVHD, which could be diagnosed and classified according to their characteristics.

CONCLUSION

As a kind of interactions between the host and donor, GVHD are severely harmful to the host. It may also occur in xenotransplantation, where GVHD can be utilized in the studies on transplant immunology, oncology etc. Xenogeneic GVHD is receiving more and more attentions.

Direct and indirect costs of chickenpox in young children

OBJECTIVE

To estimate the medical and economic or societal costs of chickenpox in young children using a descriptive study

METHODS

Children under 5 years of age attending 124 Sydney childcare centres who were reported as having chickenpox were studied to assess the costs of medication use and medical consultations, days of care missed, and parental costs resulting from lost time from work and alternate childcare costs.

RESULTS

There were 174 children (92 girls and 79 boys; in three the sex was not stated) who missed a mean of 5.5 days of care because of chickenpox, currently valued at $154. Medical costs were valued at $33 per child, based on 0.97 medical visits, and topical and oral medication. Labour costs resulting from parental work absenteeism were valued at $160 or $345 depending on the method of calculation, whilst direct economic costs of $24 were incurred through use of alternate childcare arrangements. Total costs including those incurred by secondary cases and by rare hospitalisations were in the range of $393-$578 per affected child.

CONCLUSIONS

Medical costs of chickenpox in children are small relative to costs incurred as a result of parental work absenteeism and to costs of foregone childcare. Ascribing precise work-related costs should take into account some capacity to make up lost work time. Such data will be required when determining the cost-benefit of childhood varicella immunisation.

[Topography of intraabdominal supra and infra-hepatic IVC and its application in hepatectomy]

Topographic study of infra-diaphragmatic and supra-hepatic IVC (ISIVC) was made in 16 fresh adult cadavers. The diameter and length of ISIVC averaged 35.94 +/- 5.68 mm and 16.87 +/- 5.14 mm respectively, hence making band-blockade of the ISIVC is practical. In clinical application, 21 cases of liver cancer involving the second or third hepatic hilus underwent lobectomy or segmentectomy with temporary band-blocking of the ISIVC, the infrahepatic IVC and the first hepatic hilus to prevent or to treat massive bleeding. In 3 of the 21 cases, the middle hepatic vein was inadvertently torn and was successfully suture repaired with this way.

Evaluation of inductively coupled plasma mass spectrometry as an elemental detector for supercritical fluid chromatography

Supercritical fluid chromatography coupled with inductively coupled plasma mass spectrometry shows high potential for the determination at ultratrace levels of organometallic compounds of environmental interest. In this study the determination of organotin compounds at ultratrace levels is demonstrated. In this work a supercritical fluid chromatography/inductively coupled plasma mass spectrometry (SFC/ICPMS) interface was developed. Separation of tetraalkyltin compounds shows detection levels in the subpicogram range (0.034 pg for tetrabutyltin; 0.047 pg for tetraphenyltin). The linear ranges are over 3 orders magnitude (1-1000 pg). The reproducibility of sample injections are better than 5% RSD.

Omental autotransplantation in treatment of thromboangiitis obliterans

From 1981 to 1985, omental autotransplantation was performed for 28 patients with thromboangiitis obliterans on the left lower extremities in 16 patients, the right ones 11, and the right upper limb 1. The early results in all patients were satisfactory. In 19 patients followed up from 1 to 4 years, the results were encouraging, with the improvement of symptoms after operation. In 18 patients, digital ulcers healed within 2-4 weeks. Doppler and electrical impedance plethysmography examinations showed the blood circulation of affected extremities was markedly improved in the 18 patients except one who had the recurrence of digital ulcer 2 years later. In one of the 19 patients the disease recurred one month after the operation, and a lumbar sympathectomy was performed. The indications, the operative technique, and the mechanism of this operation are discussed.