Role of cancer stem cell ecosystem on breast cancer metastasis and related mouse models

Breast cancer metastasis is responsible for most breast cancer-related deaths and is influenced by many factors within the tumor ecosystem,including tumor cells and microenvironment.Breast cancer stem cells(BCSCs)constitute a small population of cancer cells with unique characteristics,including their capacity for self-renewal and differentiation.Studies have shown that BCSCs not only drive tumorigenesis but also play a crucial role in promoting metastasis in breast cancer.The tumor microenvironment(TME),composed of stromal cells,immune cells,blood vessel cells,fibroblasts,and microbes in proximity to cancer cells,is increasingly recognized for its crosstalk with BCSCs and role in BCSC survival,growth,and dissemination,thereby influencing metastatic ability.Hence,a thorough understanding of BCSCs and the TME is critical for unraveling the mechanisms underlying breast cancer metastasis.In this review,we summarize current knowledge on the roles of BCSCs and the TME in breast cancer metastasis,as well as the underlying regulatory mechanisms.Furthermore,we provide an overview of relevant mouse models used to study breast cancer metastasis,as well as treatment strategies and clinical trials addressing BCSC-TME interactions during metastasis.Overall,this study provides valuable insights for the development of effective therapeutic strategies to reduce breast cancer metastasis.

Comparison of immune responses and intestinal flora in epicutaneously sensitized BALB/c or C57BL/6 mouse models of food allergy

Cutaneous exposure to food allergens through a disrupted skin barrier is recognized as an important cause of food allergy,and the cutaneous sensitized mouse model has been established to investigate relevant allergic disorders.However,the role of different genetic backgrounds of mice on immune responses to food allergens upon epicutaneous sensitization is largely unknown.In this study,two strains of mice,i.e.,the BALB/c and C57BL/6 mice,were epicutaneously sensitized with ovalbumin on atopic dermatitis(AD)-like skin lesions,followed by intragastric challenge to induce IgE-mediated food allergy.Allergic outcomes were measured as clinical signs,specific antibodies and cytokines,and immune cell subpopulations,as well as changes in intestinal barrier function and gut microbiota.Results showed that both strains of mice exhibited typical food-allergic symptoms with a Th2-skewed response.The C57BL/6 mice,rather than the BALB/c mice,were fitter for establishing an epicutaneously sensitized model of food allergy since a stronger Th2-biased response and severer disruptions in the intestinal barrier and gut homeostasis were observed.This study provides knowledge for selecting an appropriate mouse model to study food-allergic responses associated with AD-like skin lesions and highlights the role of genetic variations in the immune mechanism underlying pathogenesis of food allergy.

MicroRNAs in mouse and rat models of experimental epilepsy and potential therapeutic targets

Epilepsy is a common and serious neurological disease that causes recurrent seizures. The brain damage caused by seizures can lead to depression, anxiety, cognitive impairment, or disability. In almost all cases chronic seizures are difficult to cure. MicroRNAs are widely expressed in the central nervous system and play important roles in the pathogenesis of several neurological disorders, including epilepsy. A variety of animals(mostly mice and rats) have been used to induce experimental epilepsy using different protocols and miRNA profiling performed. Most of the recent studies reviewed had performed miRNA profiling in hippocampal tissues and a large number of microRNAs were dysregulated when compared to controls. Most notably, miR-132-3p,-146a-5p,-10a-5p,-21a-3p,-27a-3p,-142a-5p,-212-3p,-431-5p, and-155 were upregulated in both the mouse and rat studies. Overexpression of miR-137 and miR-219 decreased seizure severity in a mouse epileptic model, and suppression of miR-451,-10a-5p,-21a-5p,-27a-5p,-142a-5p,-431-5p,-155, and-134 had a positive influence on seizure behavior. In the rat studies, overexpression of miR-139-5p decreased neuronal damage in drug-resistant rats and inhibition of miR-129-2-3p,-27a-3p,-155,-134,-181a, and-146a had a positive effect on seizure behavior and/or reduced the loss of neuronal cells. Further studies are warranted using adult female and immature male and female animals. It would also be helpful to test the ability of specific agomirs and antagomirs to control seizure activity in a subhuman primate model of epilepsy such as adult marmosets injected intraperitoneally with pilocarpine or cynomolgus monkeys given intrahippocampal injections of kainic acid.

Anti-infection effects of heparin on SARS-CoV-2 in a diabetic mouse model

Severe acute respiratory syndrome coronavirus 2(SARSCo V-2)infection can result in more severe syndromes and poorer outcomes in patients with diabetes and obesity.However,the precise mechanisms responsible for the combined impact of coronavirus disease 2019(COVID-19)and diabetes have not yet been elucidated,and effective treatment options for SARS-Co V-2-infected diabetic patients remain limited.To investigate the disease pathogenesis,K18-h ACE2 transgenic(h ACE2^(Tg))mice with a leptin receptor deficiency(h ACE2-Lepr^(-/-))and high-fat diet(h ACE2-HFD)background were generated.The two mouse models were intranasally infected with a 5×10^(5) median tissue culture infectious dose(TCID_(50))of SARSCo V-2,with serum and lung tissue samples collected at 3days post-infection.The h ACE2-Lepr^(-/-)mice were then administered a combination of low-molecular-weight heparin(LMWH)(1 mg/kg or 5 mg/kg)and insulin via subcutaneous injection prior to intranasal infection with1×10^(4) TCID_(50)of SARS-Co V-2.Daily drug administration continued until the euthanasia of the mice.Analyses of viral RNA loads,histopathological changes in lung tissue,and inflammation factors were conducted.Results demonstrated similar SARS-Co V-2 susceptibility in h ACE2^(Tg)mice under both lean(chow diet)and obese(HFD)conditions.However,compared to the h ACE2-Lepr^(+/+)mice,h ACE2-Lepr^(-/-)mice exhibited more severe lung injury,enhanced expression of inflammatory cytokines and hypoxia-inducible factor-1α(HIF-1α),and increased apoptosis.Moreover,combined LMWH and insulin treatment effectively reduced disease progression and severity,attenuated lung pathological changes,and mitigated inflammatory responses.In conclusion,preexisting diabetes can lead to more severe lung damage upon SARS-Co V-2 infection,and LMWH may be a valuable therapeutic approach for managing COVID-19patients with diabetes.

Mouse models in male fertility research

Limited knowledge of the genetic causes of male infertility has resulted in few treatment and targeted therapeutic options. Although the ideal approach to identify infertility causing mutations is to conduct studies in the human population, this approach has progressed slowly due to the limitations described herein. Given the complexity of male fertility, the entire process cannot be modeled in vitro. As such, animal models, in particular mouse models, provide a valuable alternative for gene identification and experimentation. Since the introduction of molecular biology and recent advances in animal model production, there has been a substantial acceleration in the identification and characterization of genes associated with many diseases, including infertility. Three major types of mouse models are commonly used in biomedical research, including knockoutJknockin/gene-trapped, transgenic and chemical-induced point mutant mice. Using these mouse models, over 400 genes essential for male fertility have been revealed. It has, however, been estimated that thousands of genes are involved in the regulation of the complex process of male fertility, as many such genes remain to be characterized. The current review is by no means a comprehensive list of these mouse models, rather it contains examples of how mouse models have advanced our knowledge of post-natal germ cell development and male fertility regulation.

INT-767 improves histopathological features in a dietinduced ob/ob mouse model of biopsy-confirmed nonalcoholic steatohepatitis

AIM To characterize the efficacy of the dual FXR/TGR5 receptor agonist INT-767 upon histological endpoints in a rodent model of diet-induced and biopsy-confirmed non-alcoholic steatohepatitis(NASH).METHODS The effects of INT-767 on histological features of NASH were assessed in two studies using Lep^(ob/ob)(ob/ob) NASH mice fed the AMLN diet(high fat with transfat, cholesterol and fructose). In a proof-of-conceptstudy, Lep^(ob/ob)(ob/ob) NASH mice were first dosed with INT-767(3 or 10 mg/kg for 8 wk). A second ob/ob NASH study compared INT-767(3 and 10 mg/kg) to obeticholic acid(OCA)(10 or 30 mg/kg; 16 wk). Primary histological endpoints included qualitative and quantitative assessments of NASH. Other metabolic and plasma endpoints were also assessed. A comparative assessment of INT-767 and OCA effects on drug distribution and hepatic gene expression was performed in C57 Bl/6 mice on standard chow. C57 Bl/6 mice were orally dosed with INT-767 or OCA(1-30 mg/kg) for 2 wk, and expression levels of candidate genes were assessed by RNA sequencing and tissue drug levels were measured by liquid chromatography tandem-mass spectrometry.RESULTS INT-767 dose-dependently(3 and 10 mg/kg, PO, QD, 8 wk) improved qualitative morphometric scores on steatohepatitis severity, inflammatory infiltrates and fibrosis stage. Quantitative morphometric analyses revealed that INT-767 reduced parenchymal collagen area, collagen fiber density, inflammation(assessed by Galectin-3 immunohistochemistry) and hepatocyte lipid droplet area following INT-767 treatment. In a comparative study(16 wk), the FXR agonists OCA(10 and 30 mg/kg) and INT-767(3 and 10 mg/kg) both improved NASH histopathology, with INT-767 exerting greater therapeutic potency and efficacy than OCA. Mechanistic studies suggest that both drugs accumulate similarly within the liver and ileum, however, the effects of INT-767 may be driven by enhanced hepatic, but not ileal, FXR function. CONCLUSION These findings confirm the potential utility of FXR and dual FXR/TGR5 activation as disease intervention strategies in NASH.

Mouse models of colorectal cancer: Past, present and future perspectives

Colorectal cancer(CRC)is the third most common diagnosed malignancy among both sexes in the United States as well as in the European Union.While the incidence and mortality rates in western,high developed countries are declining,reflecting the success of screening programs and improved treatment regimen,a rise of the overall global CRC burden can be observed due to lifestyle changes paralleling an increasing human development index.Despite a growing insight into the biology of CRC and many therapeutic improvements in the recent decades,preclinical in vivo models are still indispensable for the development of new treatment approaches.Since the development of carcinogen-induced rodent models for CRC more than 80 years ago,a plethora of animal models has been established to study colon cancer biology.Despite tenuous invasiveness and metastatic behavior,these models are useful for chemoprevention studies and to evaluate colitis-related carcinogenesis.Genetically engineered mouse models(GEMM)mirror the pathogenesis of sporadic as well as inherited CRC depending on the specific molecular pathways activated or inhibited.Although the vast majority of CRC GEMM lack invasiveness,metastasis and tumor heterogeneity,they still have proven useful for examination of the tumor microenvironment as well as systemic immune responses;thus,supporting development of new therapeutic avenues.Induction of metastatic disease by orthotopic injection of CRC cell lines is possible,but the so generated models lack genetic diversity and the number of suited cell lines is very limited.Patient-derived xenografts,in contrast,maintain the pathological and molecular characteristics of the individual patient's CRC after subcutaneous implantation into immunodeficient mice and are therefore most reliable for preclinical drug development–even in comparison to GEMM or cell line-based analyses.However,subcutaneous patient-derived xenograft models are less suitable for studying most aspects of the tumor microenvironment and anti-tumoral immune responses.The authors review the distinct mouse models of CRC with an emphasis on their clinical relevance and shed light on the latest developments in the field of preclinical CRC models.

Mesenchymal stem cell-derived exosomes promote neurogenesis and cognitive function recovery in a mouse model of Alzheimer’s disease

Studies have shown that mesenchymal stem cell-derived exosomes can enhance neural plasticity and improve cognitive impairment.The purpose of this study was to investigate the effects of mesenchymal stem cell-derived exosomes on neurogenesis and cognitive capacity in a mouse model of Alzheimer’s disease.Alzheimer’s disease mouse models were established by injection of beta amyloid 1?42 aggregates into dentate gyrus bilaterally.Morris water maze and novel object recognition tests were performed to evaluate mouse cognitive deficits at 14 and 28 days after administration.Afterwards,neurogenesis in the subventricular zone was determined by immunofluorescence using doublecortin and PSA-NCAM antibodies.Results showed that mesenchymal stem cells-derived exosomes stimulated neurogenesis in the subventricular zone and alleviated beta amyloid 1?42-induced cognitive impairment,and these effects are similar to those shown in the mesenchymal stem cells.These findings provide evidence to validate the possibility of developing cell-free therapeutic strategies for Alzheimer’s disease.All procedures and experiments were approved by Institutional Animal Care and Use Committee(CICUAL)(approval No.CICUAL 2016-011)on April 25,2016.

Recent advances in mouse models of obesity-and nonalcoholic steatohepatitis-associated hepatocarcinogenesis

Hepatocellular carcinoma(HCC) is the fifth most common cancer, and obesity has been established as a risk factor for HCC development. Nonalcoholic steatohepatitis(NASH) is apparently the key link between obesity and hepatocarcinogenesis, and obesity also accelerates HCC development synergistically with other risk factors, such as hepatitis virus infection and alcohol consumption. As an explanation for the pathogenesis of NASH, the so-called "two-hit" theory has been widely accepted, but recently, a better model, the so-called "multiple-hits hypothesis" was proposed, which states that many disease-promoting factors may occur in parallel, rather than consecutively. However, the overall mechanism remains largely unknown. Various cell-cell and organ-organ interactions are involved in the pathogenesis of NASH, and thus appropriate in vivo disease models are essential for a deeper understanding. However, replicating the full spectrum of human NASH has been difficult, as NASH involves obesity, insulin resistance, steatohepatitis, fibrosis, and ultimately HCC, and the lack of an appropriate mouse model has been a considerable barrier to determining the missing links among obesity, NASH, and HCC. In recent years, several innovative mouse models presenting obesity- and NASHassociated HCC have been established by modified diets, chemotoxic agents, genetic manipulation, or a combination of these factors, shedding some light on this complex network and providing new therapeutic strategies. Thus, in this paper, I review the mouse models of obesity- and NASH-associated HCC, especially focusing on recent advances and their clinical relevance.

Hepatocellular carcinoma mouse models:Hepatitis B virusassociatedhepatocarcinogenesis and haploinsufficienttumor suppressor genes

The multifactorial and multistage pathogenesis of hepatocellular carcinoma(HCC)has fascinated a wide spectrum of scientists for decades.While a number of major risk factors have been identified,their mechanistic roles in hepatocarcinogenesis still need to be elucidated.Many tumor suppressor genes(TSGs)have been identified as being involved in HCC.These TSGs can be classified into two groups depending on the situation with respect to allelic mutation/loss in the tumors:the recessive TSGs with two required mutated alleles and the haploinsufficient TSGs with one required mutated allele.Hepatitis B virus(HBV)is one of the most important risk factors associated with HCC.Although mice cannot be infected with HBV due to the narrow host range of HBV and the lack of a proper receptor,one advantage of mouse models for HBV/HCC research is the numerous and powerfulgenetic tools that help investigate the phenotypic effects of viral proteins and allow the dissection of the dose-dependent action of TSGs.Here,we mainly focus on the application of mouse models in relation to HBV-associated HCC and on TSGs that act either in a recessive or in a haploinsufficient manner.Discoveries obtained using mouse models will have a great impact on HCC translational medicine.

Establishment of an orthotopic pancreatic cancer mouse model: Cells suspended and injected in Matrigel

AIM:To establish an orthotopic mouse model of pancreatic cancer that mimics the pathological features of exocrine pancreatic adenocarcinoma.METHODS:Pan02 cells were suspended in low-temperature Matrigel and injected into the parenchyma of pancreatic tails of C57BL/6 mice,with cells suspended in phosphate buffered saline(PBS)serving as a control.Primary and implanted tumors were confirmed pathologically.The rate of tumor formation and intraperitoneal implantation in the two groups were compared at different time points after injection.Leakage and intraabdominal dispersion of Matrigel and PBS,both dyed with methylene blue,were compared after injection into the parenchyma of the pancreas.We observed adherence and proliferation in Pan02 cells suspended in Matrigel in vitro.We also compared the pathological manifestation of this orthotopic pancreatic cancer model in the head and tails of the pancreas.The characteristics of the origin of epithelial cells and exocrine markers of established orthotopic pancreatic tumors were confirmed using immunohistochemistry.RESULTS:Diluted Matrigel could form a gel drip in the pancreatic parenchyma,effectively preventing leakage from the injection site and avoiding dispersion in the abdominal cavity.Pan02 cells were able to adhere to a dish,proliferate,and migrate in the gel drip.The tumor formation rate in the Matrigel group was 100%at both2 and 3 wk after injection,whereas it was 25.0%and37.5%in the PBS group at 2 and 3 wk,respectively(P<0.05).The intraperitoneal tumor implantation rate was 75.0%in the PBS group after 3 wk of injection,while it was 12.5%in the Matrigel group(P<0.05).Hepatoduodenal ligament and duodenal invasions with obstructive jaundice and upper digestive obstruction with mesenteric lymph node metastasis were observed in the pancreatic head group.In the pancreatic tail group,spleen and gastric invasion were dominant,leading to retroperitoneal lymph nodes metastasis.Positive immunohistochemical staining of cytokeratin and negative staining of vimentin and chromogranin A confirmed that the orthotopic pancreatic tumor injected with Pan02 cells suspended in Matrigel was of epithelial origin and expressed exocrine markers of cancer.CONCLUSION:This method of low-temperature Matrigel suspension and injection is effective for establishing an orthotopic mouse model of pancreatic cancer.

Development of a mouse model of arecoline-induced oral mucosal fibrosis

Objective: To develop a BALB/c mouse model of oral submucous fibrosis(OSF)induced by arecoline and to exhibit an accumulation of collagen and angiogenesis changes.Methods: BALB/c mice were randomly assigned to either the control(distilled water) or experimental group(arecoline)(n = 40). Eight mice from each group were sacrificed every 4 weeks since 8 weeks post treatment. Changes in histopathologic features, levels of collagen type Ⅰ and collagen type Ⅲ, and angiogenesis were measured.Results: In the 8th week, epithelium atrophy, collagen cumulation and micrangium pathologic changes in the lamina propria were observed in the oral mucosa. In the 20th week, hyaline degeneration of the connective tissues was observed on the tongue and palate mucosa. The angiogenesis and collagen type Ⅰ changed significantly as the diseases advanced(P < 0.05); however, collagen type Ⅲ was not statistically different.Conclusions: An OSF model involving mice can be rapidly induced by drinking a highdose of arecoline. OSF angiogenic changes in mice primarily decrease and collagen accumulation is mainly collagen type Ⅰ.

Development of a novel mouse constipation model

AIM: To establish a novel mouse constipation model. METHODS: Animals were randomly divided into three groups, and intragastrically administered 0-4?℃ saline(ice-cold group) or 15-20?℃ saline(saline control group) daily for 14 d, or were left untreated(blank control group). Stools were collected 3-24 h after treatment to record the wet and dry weights and the stool form. Intestinal propulsion experiments were carried out and defecation time was measured for six days continuously after suspending treatments. The expressions of PGP9.5 were detected by immunohistochemistry.RESULTS: Based on the percentage of stool weight changes compared with baseline(before irritation) in 9-14 d, stool weight changes were classified into three levels. Each level shows a different body state, which is state Ⅰ(no change: plus or minus 5%), state Ⅱ(slightly decreased: 5%-15%) and state Ⅲ(decreased: 15%-25%). In state Ⅲ, between day 9-14, the stool weights decreased by 15%-25% compared with the baseline, and changed at a rate > 10% compared with blank control values, and the stools became small and dry. Additionally, intestinal functions degenerated in these animals, and PGP9.5-positive expression markedly decreased in jejunum, ileum and proximal colon myenteric plexus.CONCLUSION: Irritation with ice-cold saline is a stable, repeatable method in building constipation model in mice for exploring the pathogenesis and treatment options of constipation, and the change of stool weight and size may serve as a useful tool to judge a constipation model success or not.

Role of FGF/FGFR signaling in skeletal development and homeostasis: learning from mouse models

Fibroblast growth factor （FGF）/fibroblast growth factor receptor （FGFR） signaling plays essential roles in bone development and diseases. Missense mutations in FGFs and FGFRs in humans can cause various congenital bone diseases, including chondrodysplasia syndromes, craniosynostosis syndromes and syndromes with dysregulated phosphate metabolism. FGF/FGFR signaling is also an important pathway involved in the maintenance of adult bone homeostasis. Multiple kinds of mouse models, mimicking human skeleton diseases caused by missense mutations in FGFs and FGFRs, have been established by knock-m/out and transgenic technologies. These genetically modified mice provide good models for studying the role of FGF/FGFR signaling in skeleton development and homeostasis. In this review, we summarize the mouse models of FGF signaling-related skeleton diseases and recent progresses regarding the molecular mechanisms, underlying the role of FGFs/FGFRs in the regulation of bone development and homeostasis. This review also provides a perspective view on future works to explore the roles of FGF signaling in skeletal development and homeostasis.

Towards a standard diet-induced and biopsy-confirmed mouse model of non-alcoholic steatohepatitis: Impact of dietary fat source

BACKGROUND The trans-fat containing AMLN(amylin liver non-alcoholic steatohepatitis,NASH)diet has been extensively validated in C57BL/6J mice with or without the Lep^ob/Lep^ob(ob/ob)mutation in the leptin gene for reliably inducing metabolic and liver histopathological changes recapitulating hallmarks of NASH.Due to a recent ban on trans-fats as food additive,there is a marked need for developing a new diet capable of promoting a compatible level of disease in ob/ob and C57BL/6J mice.AIM To develop a biopsy-confirmed mouse model of NASH based on an obesogenic diet with trans-fat substituted by saturated fat.METHODS Male ob/ob mice were fed AMLN diet or a modified AMLN diet with trans-fat(Primex shortening)substituted by equivalent amounts of palm oil[Gubra amylin NASH,(GAN)diet]for 8,12 and 16 wk.C57BL/6J mice were fed the same diets for 28 wk.AMLN and GAN diets had similar caloric content(40%fat kcal),fructose(22%)and cholesterol(2%)level.RESULTS The GAN diet was more obesogenic compared to the AMLN diet and impaired glucose tolerance.Biopsy-confirmed steatosis,lobular inflammation,hepatocyte ballooning,fibrotic liver lesions and hepatic transcriptome changes were similar in ob/ob mice fed the GAN or AMLN diet.C57BL/6J mice developed a mild to moderate fibrotic NASH phenotype when fed the same diets.CONCLUSION Substitution of Primex with palm oil promotes a similar phenotype of biopsyconfirmed NASH in ob/ob and C57BL/6J mice,making GAN diet-induced obese mouse models suitable for characterizing novel NASH treatments.

Adipose tissue-derived stem cells ameliorates dermal fibrosis in mouse models of scleroderma

Objective: To investigate the therapeutic potential of adipose-derived stem cells(ADSCs) for limited cutaneous scleroderma(LS) in mouse models,Methods: ADSCs were isolated from pathogen-free female C57BL/6 mice and LS was induced in wild type(WT) C57BL/6 mice via daily injection of bleomycin(0.1 m L x 300 μg/m L) for 4 weeks; then the ADSCs were subcutaneously injected into the dorsal area in the model treatment group,and 100 μL of phosphate buffered saline(PBS) solution was injected into the same site in the model control group,Green fluorescent protein(GFP) was used to track the cells using an in vivo imaging system on days 7,14,21 and 28 after transplantation,All mice were sacrificed and histologic analyses were performed after 4 weeks,and the skin thickness,collagen deposition and the total content of hydroxyproline were evaluated,Additionally,immunohistochemistry were performed to compare the tissue expression and distribution of TGF-β1 and VEGF between the ADSCs treatment group and the treatment control group,Results: WT C57BL/6 LS mouse model were successfully established and GFP in vivo fluorescence imaging showed that the translated ADSCs survived at the local for at least 4 weeks,Compared with the control group,the ADSCs treatment group significantly attenuated bleomycin-induced dermal fibrosis,reduced the skin thickness and the total content of hydroxyproline(P<0.05),The ADSCs treatment group displayed significantly lower levels of TGF-β1 and higher levels of VEGF than the control group(P<0.05),Conclusions: ADSCs may provide a feasible and practical treatment for autoimmune diseases such as LS and ameliorate dermal fibrosis.

Can mouse models mimic sporadic Alzheimer’s disease?

Alzheimer’s disease(AD)is a progressive neurodegenerative disorder and the most common form of dementia worldwide.As age is the main risk factor,>97%of all AD cases are of sporadic origin,potentiated by various risk factors associated with life style and starting at an age>60 years.Only<3%of AD cases are of genetic origin caused by mutations in the amyloid precursor protein or Presenilins 1 or 2,and symptoms already start at an age<30 years.In order to study progression of AD,as well as therapeutic strategies,mouse models are state-of-the-art.So far many transgenic mouse models have been developed and used,with mutations in the APP or presenilin or combinations(3×Tg,5×Tg).However,such transgenic mouse models more likely mimic the genetic form of AD and no information can be given how sporadic forms develop.Several risk genes,such as Apolipoprotein E4 and TREM-2 enhance the risk of sporadic AD,but also many risk factors associated with life style(e.g.,diabetes,hypercholesterolemia,stress)may play a role.In this review we discuss the current situation regarding AD mouse models,and the problems to develop a sporadic mouse model of AD.

Human liver chimeric mouse model based on diphtheria toxin-induced liver injury

AIM To establish an inducible liver injury mouse model and transplant human hepatocytes to obtain liverhumanized mice.METHODS We crossed three mouse strains,including albumin(Alb)-cre transgenic mice,inducible diphtheria toxin receptor(DTR) transgenic mice and severe combined immune deficient(SCID)-beige mice,to create Alb-cre/DTR/SCID-beige(ADSB) mice,which coincidentally harbor Alb-cre and DTR transgenes and are immunodeficient. As the Cre expression is driven by the liver-specific promoter Alb(encoding ALB),the DTR stop signal flanked by two lox P sites can be deleted in the ADSB mice,resulting in DTR expression in the liver. ADSB mice aged 8-10 wk were injected intraperitoneally(i.p.) with diphtheria toxin(DT) and liver damage was assessed by serum alanine aminotransferase(ALT) level. Two days later,mouse livers were sampled for histological analysis,and human hepatocytes were transplanted into the livers on the same day. A human ALB enzyme-linked immunosorbent assay was performed 7,14,21 and 28 d after transplantation. Human CD68 immunohistochemistry was performed 30 and 90 d after transplantation.RESULTS We crossed Alb-cre with DTR and SCID-beige mice to obtain ADSB mice. These mice were found to have liver damage 4 d after i.p. injection of 2.5 ng/g bodyweight DT. Bodyweight began to decrease on day 2,increased on day 7,and was lowest on day 4(range,10.5%-13.4%). Serum ALT activity began to increase on day 2 and reached a peak value of 289.7 ± 16.2 IU/m L on day 4,then returned to background values on day 7. After transplantation of human liver cells,peripheral blood human ALB level was 1580 ± 454.8 ng/m L(range,750.2-3064.9 ng/m L) after 28 d and Kupffer cells were present in the liver at 30 d in ADSB mice.CONCLUSION Human hepatocytes were successfully repopulated in the livers of ADSB mice. The inducible mouse model of humanized liver in ADSB mice may have functional applications,such as hepatocyte transplantation,hepatic regeneration and drug metabolism.

Anti-apoptotic treatment in mouse models of age-related hearing loss

Age-related hearing loss (AHL), or presbycusis, is the most common neurodegenerative disorder and top communication deficit of the aged population. Genetic predisposition is one of the major factors in the development of AHL. Generally, AHL is associated with an age-dependent loss of sensory hair cells, spiral ganglion neurons and stria vascularis cells in the inner ear. Although the mechanisms leading to genetic hearing loss are not completely understood, caspase-family proteases function as important signals in the inner ear pathology. It is now accepted that mouse models are the best tools to study the mechanism of genetic hearing loss or AHL. Here, we provide a brief review of recent studies on hearing improvement in mouse models of AHL by anti-apoptotic treatment.

Platelet-rich plasma enhances adipose-derived stem cell-mediated angiogenesis in a mouse ischemic hindlimb model

AIM To evaluate the angiogenic effect of platelet-rich plasma(PRP)-preconditioned adipose-derived stem cells(ADSCs) both in vitro and in a mouse ischemic hindlimb model.METHODS ADSCs were divided based on culture medium: 2.5% PRP, 5% PRP, 7.5% PRP, and 10% PRP. Cell proliferation rate was analyzed using the MTS assay. The gene expression of CD31, vascular endothelial growth factor, hypoxia-inducible factors, and endothelial cell nitric oxide synthase was analyzed using reverse transcription polymerase chain reaction. Cell markers and structural changes were assessed through immunofluorescence staining and the tube formation assay. Subsequently, we studied the in vivo angiogenic capabilities of ADSCs by a mouse ischemic hindlimb model.RESULTS The proliferation rate of ADSCs was higher in the 2.5%, 5%, and 7.5% PRP groups. The expression of hypoxia-inducible factor, CD31, vascular endothelial growth factor, and endothelial cell nitric oxide synthase in the 5% and 7.5% PRP groups increased. The 5%, 7.5%, and 10% PRP groups showed higher abilities to promote both CD31 and vascular endothelial growth factor production and tubular structure formation in ADSCs. According to laser Doppler perfusion scan, the perfusion ratios of ischemic limb to normal limb were significantly higher in 5% PRP, 7.5% PRP, and human umbilical vein endothelial cells groups compared with the negative control and fetal bovine serum(FBS) groups(0.88 ± 0.08, 0.85 ± 0.07 and 0.81 ± 0.06 for 5%, 7.5% PRP and human umbilical vein endothelial cells compared with 0.42 ± 0.17 and 0.54 ± 0.14 for the negative control and FBS, P < 0.01).CONCLUSION PRP-preconditioned ADSCs presented endothelial cell characteristics in vitro and significantly improved neovascularization in ischemic hindlimbs. The optimal angiogenic effect occurred in 5% PRP-and 7.5% PRPpreconditioned ADSCs.