Medaka Model Research Articles

Resveratrol protects against Rankl-induced mineralized bone damage in a transgenic medaka fish model of osteoporosis

Natural substances with bone protective potential always greatly attract researchers for the development of safer and more effective drugs for osteopenia and osteoporosis. Resveratrol (RES), a plant polyphenol found in red grapes and berries has been commonly suggested as supplement for bone health. It has shown bone anabolic and anti-resorptive effects in different in vitro cell cultures and in vivo rodent models. Recently, the medaka fish (Oryzias latipes) has emerged as a valuable model organism for bone research. In this study, we present, for the first time, evidence that resveratrol, tested at five doses (25, 50, 100, 150, and 200 μM), mitigated bone loss induced by Rankl in a transgenic medaka model for osteoporosis. Notably, the dose of 150 μM exhibited the highest bone-protective and anti-resorptive effect, reducing bone loss by approximately 20%. However, at the same dose, RES did not significantly affect the signal densities of green fluorescent protein (GFP) and alizarin complexone (ALC), which represent osteoblasts and mineralized matrix, respectively, in col10a1:nlGFP transgenic medaka larvae. In these larvae, osteoblasts were marked by GFP, and bone was stained with ALC. Our findings provide significant evidence from a non-rodent model regarding the therapeutic potential of resveratrol.

Reproductive toxicity of DDT in the Japanese medaka fish model: Revisiting the impacts of DDT+ on female reproductive health

The organochlorine pesticide dichlorodiphenyltrichloroethane (DDT) is an endocrine-disrupting compound (EDC) that has been banned by most countries for decades. However, it continues to be detected in nearly all humans and wildlife due to its biological and environmental persistence. The ovarian dysgenesis syndrome hypothesis speculates that exposure to EDCs during sensitive developmental windows such as early gonadal differentiation lead to reproductive disorders later in life. Yet, mechanisms by which DDT affects developing gonads remain unclear due to the inherent challenge of getting developmental exposure data from adults presenting with reproductive disease. The Japanese medaka (Oryzias latipes) is a valuable fish model for sex-specific toxicological studies due to its chromosomal sex determination, external embryonic development, short generation time, and extensively mapped genome. It is well documented that medaka exposed to DDT and its metabolites and byproducts (herein referred to as DDT+) at different developmental time points experience permanent alterations in gonadal morphology, reproductive success, and molecular and hormonal signaling. However, the overwhelming majority of studies focus primarily on functional and morphological outcomes in males and females and have rarely investigated long-term transcriptional or molecular effects. This review summarizes previous experimental findings and the state of our knowledge concerning toxic effects DDT + on reproductive development, fertility, and health in the valuable medaka model. It also identifies gaps in knowledge, emphasizing a need for more focus on molecular mechanisms of ovarian endocrine disruption using enhanced molecular tools that have become increasingly available over the past few decades. Furthermore, DDT forms a myriad of over 45 metabolites and transformation products in biota and the environment, very few of which have been evaluated for environmental abundance or health effects. This reinforces the demand for high throughput and economical in vivo models for predictive toxicology screening, and the Japanese medaka is uniquely positioned to meet this need.

A Collagen10a1 mutation disrupts cell polarity in a medaka model for metaphyseal chondrodysplasia type Schmid

Heterozygous mutations in COL10A1 lead to metaphyseal chondrodysplasia type Schmid (MCDS), a skeletal disorder characterized by epiphyseal abnormalities. Prior analysis revealed impaired trimerization and intracellular retention of mutant collagen type X alpha 1 chains as cause for elevated endoplasmic reticulum (ER) stress. However, how ER stress translates into structural defects remained unclear. We generated a medaka (Oryzias latipes) MCDS model harboring a 5 base pair deletion in col10a1, which led to a frameshift and disruption of 11 amino acids in the conserved trimerization domain. col10a1Δ633a heterozygotes recapitulated key features of MCDS and revealed early cell polarity defects as cause for dysregulated matrix secretion and deformed skeletal structures. Carbamazepine, an ER stress-reducing drug, rescued this polarity impairment and alleviated skeletal defects in col10a1Δ633a heterozygotes. Our data imply cell polarity dysregulation as a potential contributor to MCDS and suggest the col10a1Δ633a medaka mutant as an attractive MCDS animal model for drug screening.

Development and validation of a Medaka fish voxel-based model for internal ionizing radiation dosimetry

In this paper, we present a voxel-based phantom of Medaka fish that can be used to assess the internal radiation doses that would be absorbed by different organs of this fish species if exposed to radioactive wastewater released into the ocean. The geometric model for fish was generated based on available Wavefront Object files for smooth-bodied Medaka fish organs, whereas due to the lack of Medaka fish material specification, the material model was constructed using material data appropriate to ICRP 110 adult male voxel-based phantom. Absorbed Fractions (AFs) and Specific Absorbed Fractions (SAFs) were calculated for eight organs of major interest as sources and for each organ as target at a set of discrete photon, electron, alpha and neutron energies. To validate the present model the calculated AFs in the studied organs were compared to ones obtained in similar organs in a voxel-based phantom of another teleost fish species called Limanda limanda. The results presented are consistent with the reference dosimetric data. We concluded that the Medaka model can be used in radioecology research to improve marine radiation protection.

Characterization of Fibrodysplasia Ossificans Progessiva relevant Acvr1/Acvr2 Activin receptors in medaka (Oryzias latipes).

Activin and Bone Morphogenetic Protein (BMP) signaling plays crucial roles in vertebrate organ formation, including osteo- and angiogenesis, and tissue homeostasis, such as neuronal maintenance. Activin and BMP signaling needs to be precisely controlled by restricted expression of shared receptors, stoichiometric composition of receptor-complexes and presence of regulatory proteins. A R206H mutation in the human (hs) BMP type I receptor hsACVR1, on the other hand, leads to excessive phosphorylation of Sons of mothers against decapentaplegic (SMAD) 1/5/8. This in turn causes increased inflammation and heterotopic ossification in soft tissues of patients suffering from Fibrodysplasia Ossificans Progressiva (FOP). Several animal models have been established to understand the spontaneous and progressive nature of FOP, but often have inherent limitations. The Japanese medaka (Oryzias latipes, ola) has recently emerged as popular model for bone research. To assess whether medaka is suitable as a potential FOP animal model, we determined the expression of Activin receptor type I (ACVR1) orthologs olaAcvr1 and olaAcvr1l with that of Activin type II receptors olaAcvr2ab, olaAcvr2ba and olaAcvr2bb in embryonic and adult medaka tissues by in situ hybridization. Further, we showed that Activin A binding properties are conserved in olaAcvr2, as are the mechanistic features in the GS-Box of both olaAcvr1 and olaAcvr1l. This consequently leads to FOP-typical elevated SMAD signaling when the medaka type I receptors carry the R206H equivalent FOP mutation. Together, this study therefore provides experimental groundwork needed to establish a unique medaka model to investigate mechanisms underlying FOP.

Knockout of sws2a and sws2b in Medaka (Oryzias latipes) Reveals Their Roles in Regulating Vision-Guided Behavior and Eye Development.

The medaka (Oryzias latipes) is an excellent vertebrate model for studying the development of the retina. Its genome database is complete, and the number of opsin genes is relatively small compared to zebrafish. Short wavelength sensitive 2 (sws2), a G-protein-coupled receptor expressed in the retina, has been lost in mammals, but its role in eye development in fish is still poorly understood. In this study, we established a sws2a and sws2b knockout medaka model by CRISPR/Cas9 technology. We discovered that medaka sws2a and sws2b are mainly expressed in the eyes and may be regulated by growth differentiation factor 6a (gdf6a). Compared with the WT, sws2a-/- and sws2b-/- mutant larvae displayed an increase in swimming speed during the changes from light to dark. We also observed that sws2a-/- and sws2b-/- larvae both swam faster than WT in the first 10 s of the 2 min light period. The enhanced vision-guided behavior in sws2a-/- and sws2b-/- medaka larvae may be related to the upregulation of phototransduction-related genes. Additionally, we also found that sws2b affects the expression of eye development genes, while sws2a is unaffected. Together, these findings indicate that sws2a and sws2b knockouts increase vision-guided behavior and phototransduction, but on the other hand, sws2b plays an important role in regulating eye development genes. This study provides data for further understanding of the role of sws2a and sws2b in medaka retina development.

Effects of a selective PPARα modulator, sodium-glucose cotransporter 2 inhibitor, and statin on the myocardial morphology of medaka nonalcoholic fatty liver disease model

ObjectiveNonalcoholic fatty liver disease (NAFLD) is associated with metabolic dysregulation and is linked with various cardiovascular complications, which often lead to poor prognostic outcomes. To develop a standard therapy for NAFLD and to urgently address its complications, the current study aimed to investigate the mechanisms of NAFLD-related heart disease and the therapeutic effects of drugs targeting various metabolic pathways. MethodsTo explore the mechanism of NAFLD-related heart disease, a medaka model of high-fat diet-induced NAFLD was utilized. The gross structural, histological, and inflammatory changes in the myocardium were evaluated in a time-dependent manner. In addition, the therapeutic effects of medicines used for NAFLD treatment including, selective peroxisome proliferator-activated receptor α modulator (SPPARMα, pemafibrate), sodium-glucose cotransporter 2 (SGLT2) inhibitor (tofogliflozin), and statin (pitavastatin), and their combinations on heart pathology were evaluated. To determine the mechanisms underlying the therapeutic effects, the expression of genes related to liver inflammation was assessed via whole transcriptome sequencing analysis. ResultsThe fish with NAFLD-related heart injury presented with cardiomyocyte hypertrophy, which led to cardiac hypertrophy. This morphological change was caused by the infiltration of inflammatory cells, including macrophages and CD4− and CD8-positive lymphocytes, in the cardiac wall and the expression of transforming growth factor beta 1 in the cardiomyocytes.Further, the livers of the fish had upregulated expressions of senescence-associated secretory phenotype-related genes. Treatment with pemafibrate, tofogliflozin, and pitavastatin reduced these changes and, consequently, cardiomyopathy. ConclusionOur results demonstrated that NAFLD-related heart disease was attributed to the senescence-associated secretory phenotype-induced inflammatory activity in the cardiac wall, which resulted in myocardial hypertrophy. Moreover, the effects of SPPARMα, SGLT2 inhibitor, and statin on NAFLD-related heart disease were evident in the medaka NAFLD model.

Transcriptome Profiling of Osteoblasts in a Medaka (Oryzias latipes) Osteoporosis Model Identifies Mmp13b as Crucial for Osteoclast Activation.

Matrix metalloproteases (MMPs) play crucial roles in extracellular matrix (ECM) modulation during osteoclast-driven bone remodeling. In the present study, we used transcriptome profiling of bone cells in a medaka model for osteoporosis and bone regeneration to identify factors critical for bone remodeling and homeostasis. This identified mmp13b, which was strongly expressed in osteoblast progenitors and upregulated under osteoporotic conditions and during regeneration of bony fin rays. To characterize the role of mmp13b in bone remodeling, we generated medaka mmp13b mutants by CRISPR/Cas9. We found that mmp13b mutants form normal numbers of osteoblasts and osteoclasts. However, osteoclast activity was severely impaired under osteoporotic conditions. In mmp13b mutants and embryos treated with the MMP13 inhibitor CL-82198, unmineralized collagens and mineralized bone matrix failed to be degraded. In addition, the dynamic migratory behavior of activated osteoclasts was severely affected in mmp13b mutants. Expression analysis showed that maturation genes were downregulated in mmp13b deficient osteoclasts suggesting that they remain in an immature and non-activated state. We also found that fin regeneration was delayed in mmp13b mutants with a concomitant alteration of the ECM and reduced numbers of osteoblast progenitors in regenerating joint regions. Together, our findings suggest that osteoblast-derived Mmp13b alters the bone ECM to allow the maturation and activation of osteoclasts during bone remodeling in a paracrine manner. Mmp13b-induced ECM alterations are also required to facilitate osteoblast progenitor recruitment and full regeneration of bony fin rays.

Effects of a novel selective PPARα modulator, statin, sodium-glucose cotransporter 2 inhibitor, and combinatorial therapy on the liver and vasculature of medaka nonalcoholic steatohepatitis model

ObjectiveNonalcoholic steatohepatitis (NASH) is a disease entity with an increasing incidence, with involvement of several metabolic pathways. Various organs, including the liver, kidneys, and the vasculature, are damaged in NASH, indicating the urgent need to develop a standard therapy. Therefore, this study was conducted to investigate the effects of drugs targeting various metabolic pathways and their combinations on a high-fat diet (HFD)-induced NASH medaka model. MethodsTo investigate the effects of drugs on vascular structures, the NASH animal model was developed using the fli::GFP transgenic medaka fed with HFD at 20 mg/fish daily. The physiological changes, histological changes in the liver, vascular structures in the fin, and serum biochemical markers were evaluated in a time-dependent manner after treatment with selective peroxisome proliferator-activated receptor α modulator (pemafibrate), statin (pitavastatin), sodium-glucose cotransporter 2 inhibitor (tofogliflozin), and their combinations. Furthermore, to determine the mechanisms underlying the effects, whole transcriptome sequencing was conducted using medaka liver samples. ResultsHistological analyses revealed significant suppression of fat accumulation and fibrotic changes in the liver after treatment with drugs and their combinations. The expression levels of steatosis- and fibrosis-related genes were modified by the treatments. Moreover, the HFD-induced vascular damages in the fin exhibited milder changes after treatment with the drugs. ConclusionThe effects of treating various metabolic pathways on the medaka body, liver, and vascular structures of the NASH medaka model were evidenced. Moreover, to our knowledge, this study is the first to report whole genome sequence and gene expression evaluation of medaka livers, which could be helpful in clarifying the molecular mechanisms of drugs.

Peonidin-3-O-glucoside and cyanidin increase osteoblast differentiation and reduce RANKL-induced bone resorption in transgenic medaka.

Experimental and clinical studies suggest a positive impact of anthocyanins on bone health; however, the mechanisms of anthocyanins altering the differentiation and function of osteoblasts and osteoclasts are not fully understood. This work demonstrates that dietary anthocyanins and resveratrol increased proliferation of cultured human hFOB 1.19 osteoblasts. In addition, treatment of serum starvation of hFOB osteoblasts with anthocyanins and resveratrol at 1.0 μg/ml reduced apoptosis, the Bax/Bcl-2 ratio, p53, and HDAC1 expression, but increased SIRT1/3 and PGC1α mRNA expression, suggesting mitochondrial and epigenetic regulation. In Sp7/osterix:mCherry transgenic medaka, peonidin-3-O-glucoside and resveratrol increased osteoblast differentiation and increased the expression of Sp7/osterix. Cyanidin, peonidin-3-O-glucoside, and resveratrol also reduced RANKL-induced ectopic osteoclast formation and bone resorption in col10α1:nlGFP/rankl:HSE:CFP medaka in doses of 1-4μg/ml. The results indicate that both cyanidin and peonidin-3-O-glucoside have anabolic effects on bone, increasing osteoblast proliferation and differentiation, mitochondrial biogenesis, and by altering the osteoblast epigenome. Cyanidin and peonidin-3-O-glucoside also reduced RANKL-induced bone resorption in a transgenic medaka model of bone resorption. Thus, peonidin-3-O-glucoside and cyanidin appear to both increase bone formation and reduce bone loss, suggesting that they be further investigated as potential treatments for osteoporosis and osteomalacia.

Establishment of an Adult Medaka Fatty Liver Model by Administration of a Gubra-Amylin-Nonalcoholic Steatohepatitis Diet Containing High Levels of Palmitic Acid and Fructose.

Among lifestyle-related diseases, fatty liver is the most common liver disease. To date, mammalian models have been used to develop methods for inhibiting fatty liver progression; however, new, more efficient models are expected. This study investigated the creation of a new model to produce fatty liver more efficiently than the high-fat diet medaka model that has been used to date. We compared the GAN (Gubra-Amylin nonalcoholic steatohepatitis) diet, which has been used in recent years to induce fatty liver in mice, and the high-fat diet (HFD). Following administration of the diets for three months, enlarged livers and pronounced fat accumulation was noted. The GAN group had large fat vacuoles and lesions, including ballooning, compared to the HFD group. The GAN group had a higher incidence of lesions. When fenofibrate was administered to the fatty liver model created via GAN administration and liver steatosis was assessed, a reduction in liver fat deposition was observed, and this model was shown to be useful in drug evaluations involving fatty liver. The medaka fatty liver model administered with GAN will be useful in future fatty liver research.

A collagen10a1 mutation disrupts cell polarity and causes skeletal defects in a medaka model for Schmid Metaphyseal Chondrodysplasia

A collagen10a1 mutation disrupts cell polarity and causes skeletal defects in a medaka model for Schmid Metaphyseal Chondrodysplasia

Multigenerational Impacts of Benzo[a]pyrene on Bone Modeling and Remodeling in Medaka (Oryzias latipes).

Ancestral benzo[a]pyrene (BaP) (1 μg/L, 21 days) exposure has previously been shown to cause skeletal deformities in medaka (Oryzias latipes) larvae in the F1-F3 generation. However, when and how this deformity is induced during bone development remain to be elucidated. The col10a1:nlGFP/osx:mCherry double transgenic medaka model was employed to determine the temporal and spatial changes of col10a1:nlGFP- positive osteochondral progenitor cells (OPCs) and osx:mCherry-positive premature osteoblasts (POBs) [8 days postfertilization (dpf)-31 dpf] in combination with changes in bone mineralization at the tissue level. Ancestral BaP exposure delayed the development of col10a1:nlGFP- and osx:mCherry-positive osteoblasts and reduced the abundance of col10a1:nlGFP-positive osteoblast progenitors and col10a1:nlGFP/osx:mCherry double-positive premature osteoblasts during critical windows of early vertebral bone formation, associated with reduced bone mineralization in embryos (14 dpf) and larvae (31 dpf), compressed vertebral segments in larvae (31 dpf), and reduced bone thickness in adult male medaka (6 months old) of the F1-F3 generations. Both Col10a1:nlGFP and osx:mCherry were identified as potential targets of epigenetic modifications underlying the transgenerational inheritance of BaP bone toxicity. The present study provides novel knowledge of the underlying mechanisms of transgenerational toxicity of BaP at the cellular level.

The dietary anthocyanin delphinidin prevents bone resorption by inhibiting Rankl-induced differentiation of osteoclasts in a medaka (Oryzias latipes) model of osteoporosis.

The anthocyanin delphinidin is a natural compound found as water-soluble pigment in coloured fruits and berries. Anthocyanin-rich diets have been proposed to have bone protective effects in humans and mice, but the underlying mechanisms remain unclear. In this study, we used a medaka (Oryzias latipes) osteoporosis model to test the effects of delphinidin on bone cells in vivo. In this model, inducible transgenic expression of receptor-activator of NF-kβ ligand (Rankl) leads to ectopic formation of osteoclasts and excessive bone resorption, similar to the situation in human osteoporosis patients. Using live imaging in medaka bone reporter lines, we show that delphinidin significantly reduces the number of osteoclasts after Rankl induction and protects bone integrity in a dose-dependent manner. Our in vivo findings suggest that delphinidin primarily affects the de novo differentiation of macrophages into osteoclasts rather than the recruitment of macrophages to sites of bone resorption. For already existing osteoclasts, delphinidin treatment affected their morphology, leading to fewer protrusions and a more spherical shape. Apoptosis rates were not increased by delphinidin, suggesting that osteoclast numbers were reduced primarily by impaired differentiation from macrophage progenitors and reduced maintenance of pre-existing osteoclasts. Importantly, and in contrast to previously reported cell culture experiments, no effect of delphinidin on osteoblast differentiation and distribution was observed in medaka in vivo. Our study is the first report on the effects of delphinidin on bone cells in fish embryos, which are a unique model system for compound testing that is suitable for live imaging of bone cell behaviour in vivo.

Inhibition of sodium-glucose cotransporter 2 ameliorates renal injury in a novel medaka model of nonalcoholic steatohepatitis-related kidney disease.

The effect of sodium‐glucose cotransporter 2 inhibitor (SGLT2I) on nonalcoholic steatohepatitis (NASH) has been reported, but there are few studies on its effect on NASH‐related renal injury. In this study, we examined the effect of SGLT2I using a novel medaka fish model of NASH‐related kidney disease, which was developed by feeding the d‐rR/Tokyo strain a high‐fat diet. SGLT2I was administered by dissolving it in water of the feeding tank. SGLT2I ameliorates macrophage accumulation and oxidative stress and maintained mitochondrial function in the kidney. The results demonstrate the effect of SGLT2I on NASH‐related renal injury and the usefulness of this novel animal model for research into NASH‐related complications.

Extracellular vesicles from human bone marrow mesenchymal stem cells repair organ damage caused by cadmium poisoning in a medaka model.

Treatment modalities for kidney disease caused by long‐term exposure to heavy metals, such as cadmium (Cd), are limited. Often, chronic, long‐term environmental exposure to heavy metal is not recognized in the early stages; therefore, chelation therapy is not an effective option. Extracellular vesicles (EVs) derived from stem cells have been demonstrated to reduce disease pathology in both acute and chronic kidney disease models. To test the ability of EVs derived from human bone marrow mesenchymal stem cells (hBM‐MSCs) to treat Cd damage, we generated a Cd‐exposed medaka model. This model develops heavy metal‐induced cell damage in various organs and tissues, and shows decreased overall survival. Intravenous injection of highly purified EVs from hBM‐MSCs repaired the damage to apical and basolateral membranes and mitochondria of kidney proximal tubules, glomerular podocytes, bone deformation, and improved survival. Our system also serves as a model with which to study age‐ and sex‐dependent cell injuries of organs caused by various agents and diseases. The beneficial effects of EVs on the tissue repair process, as shown in our novel Cd‐exposed medaka model, may open new broad avenues for interventional strategies.

Study on Streptococcus agalactiae infection in Javanese medaka (Oryzias javanicus Bleeker, 1854) model

This study determines the median lethal dose, and describes the clinico-pathological changes and disease development following Streptococcus agalactiae infection in Javanese medaka model. Javanese medakas were infected with S. agalactiae via intraperitoneal (IP) from 104 to 108 CFU/mL, and immersion (IM) route from 103 to 107 CFU/mL. The LD50–240h and clinico-pathological changes of the fish was determined until 240 h post infection (hpi). Next, the disease development was determined for 96 hpi in the fish following IP and IM infection at 103 CFU/mL and 104 CFU/mL, respectively. The LD50–240h of S. agalactiae in Javanese medaka was lower following IP injection (4.5 × 102 CFU/mL), compared to IM route (3.5 × 103 CFU/mL). The clinical signs included separating from the schooling group, swimming at the surface of water column, lethargy, erratic swimming pattern, corneal opacity and exophthalmia. Histopathological examinations revealed generalized congestion in almost all internal organs, particularly in liver and brain, while the kidney displayed tubular necrosis. Both IP and IM routes showed significant positive correlation (p < 0.05) between the CFU/g of S. agalactiae in the fish tissue and fish deaths. Moreover, the lesions for histopathological scoring in selected organs following IP and IM challenges were also reflecting the CFU/g and fish deaths. This study indicates the capability of Javanese medaka as a model organism in study of streptococcosis development.

Inhibition of sodium glucose cotransporter 2 (SGLT2) delays liver fibrosis in a medaka model of nonalcoholic steatohepatitis (NASH).

The rise in the incidence of nonalcoholic steatohepatitis (NASH) has necessitated the development of an effective prevention methodology. An antidiabetic drug, belonging to the group of sodium glucose cotransporter 2 (SGLT2) inhibitors, has been tested for its therapeutic effect on NASH; however, no studies to date have demonstrated the preventive effect of an SGLT2 inhibitor on the histological progression of steatosis and fibrosis in a sequential manner in animal models. In the present study, we examined the effect of the SGLT2 inhibitor, tofogliflozin (Tofo), on NASH liver tissue using medaka as an animal model, maintaining a feeding amount and drug concentration in all animal bodies. We generated a medaka NASH model by feeding d‐rR/Tokyo medaka a high‐fat diet and administered Tofo by dissolving the drug directly in the water of the feeding tank. Thereafter, the effects of Tofo on body weight (BW), liver weight, hepatotoxicity, fatty infiltration, and fibrotic changes in the liver were examined. We report here that SGLT2 is expressed in medaka fish and that Tofo inhibits the accumulation of fatty tissue and delays the progression of liver fibrosis in the medaka NASH model by inhibiting increases in blood sugar, serum lipids, and transaminase, irrespective of changes in BW. These results suggest that Tofo is effective for treating NASH and that the medaka model may be useful for developing new therapeutic drugs for this disease.

4-O-Methylhonokiol Influences Normal Cardiovascular Development in Medaka Embryo.

Although 4-O-Methylhonokiol (MH) effects on neuronal and immune cells have been established, it is still unclear whether MH can cause a change in the structure and function of the cardiovascular system. The overarching goal of this study was to evaluate the effects of MH, isolated from Magnolia grandiflora, on the development of the heart and vasculature in a Japanese medaka model in vivo to predict human health risks. We analyzed the toxicity of MH in different life-stages of medaka embryos. MH uptake into medaka embryos was quantified. The LC50 of two different exposure windows (stages 9–36 (0–6 days post fertilization (dpf)) and 25–36 (2–6 dpf)) were 5.3 ± 0.1 μM and 9.9 ± 0.2 μM. Survival, deformities, days to hatch, and larval locomotor response were quantified. Wnt 1 was overexpressed in MH-treated embryos indicating deregulation of the Wnt signaling pathway, which was associated with spinal and cardiac ventricle deformities. Overexpression of major proinflammatory mediators and biomarkers of the heart were detected. Our results indicated that the differential sensitivity of MH in the embryos was developmental stage-specific. Furthermore, this study demonstrated that certain molecules can serve as promising markers at the transcriptional and phenotypical levels, responding to absorption of MH in the developing embryo.

Developmental and bone development indexes of medaka fish at 11 and 16 days of age

The teleost fish medaka (Oryzias latipes) is currently used by laboratories worldwide as a model for many human diseases, including bone diseases. Our research group focuses on a medaka model for osteoporosis. To characterize the bone indexes of diseased animals, the bone development indexes of healthy wild-type fish are required for comparative analysis. Thus, this study examined the developmental and bone development indexes of wild-type medaka larvae at 11 and 16 days of age, the two developmental stages selected for the analysis of diseased patterns in osteoporosis-induced animals. The assessed parameters included the total body length of live larvae, number of caudal fin rays, vertebrae, and neural and hemal arches, as well as the total areas of mineralized vertebrae and lengths of mineralized arches. The obtained data are important for subsequent studies on bones using this fish model.