Biology subjects

Arakawa, K.

Publications and source records attributed to Arakawa, K..

At least 19 recordsLinked to original sources

bioRxiv2026

A Col22a1-EGFP reporter reveals dynamic three-dimensional organization of the myotendinous junction

The myotendinous junction (MTJ) is a specialized extracellular matrix-rich interface that transmits contractile force generated by skeletal muscle to tendon, but its three-dimensional organization and dynamics remain poorly characterized. Here, we generate a Col22a1-EGFP knock-in mouse that enables direct visualization and quantitative analysis of MTJs from embryonic development to adulthood. Tissue-clearing and three-dimensional imaging reveal extensive variation in MTJ morphology and spatial distribution among skeletal muscles and between myofiber types. During embryonic MTJ formation, COL22A1-EGFP undergoes a striking transition from intracellular puncta within developing myofibers to extracellular accumulation at myofiber tips, associated with polarized Golgi organization. We further identify complex tendon protrusions that emerge during postnatal growth and connect tendon bodies with subsets of MTJs. These interfaces contain morphologically distinct Scx-lineage cells that express Col22a1, identifying a specialized tendon-associated population at the MTJ. Finally, muscle unloading and overload differentially alter COL22A1-EGFP signal intensity and area, respectively, demonstrating that the reporter provides a quantitative readout of MTJ responses to altered mechanical conditions. Thus, Col22a1-EGFP reveals previously unrecognized spatial, developmental, and adaptive features of the muscle-tendon interface and provides an experimental platform for investigating MTJ biology in vivo.

developmental biology↗

bioRxiv2026

A Novel Slow-Progressive Knee Osteoarthritis Murine Model Induced by Non-Invasive Posterior Cruciate Ligament Rupture in Mice

ObjectiveRecently, alternatives to animal testing, such as new approach methodologies, are being developed in the orthopedic research field; animal models still provide valuable insights into the pathogenesis of knee osteoarthritis (OA). However, commonly used models develop OA much more rapidly and severely than those observed in human patients. We aimed to develop a novel murine model that closely mimics the slow progression of human OA with posterior Cruciate ligament (PCL) rupture. Design12-week-old C57BL/6 mice were induced to PCL-rupture (PCL-R) by manually applying an external tibial posterior translation force. We analyzed joint kinematics, histological observations, and bone structure to confirm the absence of concurrent injury on day 0. Then, joint stability and the pathophysiological progression of knee OA were analyzed at 8, 16, and 34 weeks post-PCL-R. The destabilized medial meniscus (DMM) model was also analyzed to compare the OA progression. ResultsNon-invasive PCL-R intervention induced the complete rupture in the central region of PCL without concurrent injury. The PCL-R group showed larger posterior tibial deviation than the INTACT (P=0.008). Regarding the range of motion in the PCL-R group, there was no limitation in range of motion on day 0, but extension limitations occurred at weeks 16 and 34 weeks. Histologically, articular cartilage degeneration in PCL-R was milder than DMM. In the subchondral bone, micro-CT reconstruction images indicated that, compared with the INTACT group, the DMM group observed progressive subchondral bone formation from 16 weeks post-surgery. In contrast, the PCLR group maintained the subchondral bone structure even at 34 weeks. ConclusionsPCL-R model induced mild abnormal mechanical stress depending on posterior instability, and cartilage degeneration occurred more slowly in this model than in DMM models.

pathology↗

bioRxiv2026

Microbe-dependent inter-organ communication regulates germline stem cell proliferation in Drosophila

Animals integrate environmental cues with internal physiological states through inter-organ communication to regulate reproduction. However, how environmental microbes are incorporated into these systemic pathways to control reproductive stem cell proliferation remains poorly understood. Here, we demonstrate that environmental microbes colonizing the gut promote stem cell-mediated oogenesis in Drosophila melanogaster by increasing germline stem cell (GSC) number. This process requires microbial activation of gut metabolic pathways, including glycolysis and the pentose phosphate pathway (PPP), linking microbial cues to organismal physiology. We further show that microbial cues modulate circadian clock gene expression in both the gut and brain, and that circadian gene activity in these tissues is required for microbe-induced increases in GSCs. These metabolic changes promote ecdysone and juvenile hormone signaling in ovarian somatic cells, and single-cell transcriptomic analyses further reveal cell type-specific metabolic and hormonal responses across germline and follicle cell populations. Together, our findings establish that microbe-dependent gut-mediated inter-organ communication integrates metabolism, circadian gene expression, and endocrine signaling to regulate stem cell-mediated reproduction in Drosophila.

developmental biology↗

bioRxiv2026

Image-scanning light-sheet microscopy for high-speed volumetric imaging of complex biological dynamics

Volumetric fluorescence microscopy is a powerful method for studying complex biological systems because it enables comprehensive observation of structural and physiological dynamics. In particular, light-sheet microscopy (LSM) is a leading option for real-time volumetric fluorescence imaging as it combines high imaging speed, low phototoxicity, minimal photobleaching, high spatiotemporal resolution, and low computational burden. To capture fast biological events, various efforts have been made to improve the imaging speed of volumetric fluorescence microscopy, including LSM. However, existing approaches entail significant trade-offs that make routine volumetric imaging at and beyond video rates challenging under practical conditions. Here, we introduce image-scanning LSM, a method that substantially increases the volumetric imaging speed achievable with LSM while preserving key performance metrics, such as spatial resolution and photon efficiency, as well as accessibility. Our implementation, termed image-scanning oblique plane (ISOP) microscopy, enables volumetric fluorescence imaging at up to 1,000 volumes per second with submicrometer lateral spatial resolution. We demonstrate the broad utility of ISOP microscopy by recording and analyzing the dynamics of behaving and rapidly moving organisms.

bioengineering↗

bioRxiv2026

Comparative genomics reveals signatures of distinct metabolic strategies and gene loss associated with Hydra immortality

Hydra is a freshwater cnidarian genus that provides a unique comparative model for aging research, contrasting the immortal H. vulgaris with the aging-inducible H. oligactis. Here, we report a high-quality, chromosome-level genome assembly of H. vulgaris strain AEP.JNIG. Our assembly is comparable in quality to existing resources, facilitating the analysis of genomic diversity across laboratory strains. Epigenomic profiling revealed that gene-body hypermethylation correlates with transcriptional stability and the suppression of spurious transcription in evolutionary conserved genes, suggesting an epigenetic mechanism for genomic integrity. Furthermore, comparative genomics demonstrated that while Hydra conserves fundamental Hallmarks of Aging pathways, the immortal H. vulgaris paradoxically lacks canonical anti-aging genes (e.g., Klotho, NAMPT) found in the aging-inducible H. oligactis. Instead, H. vulgaris exhibits a distinct metabolic signature related to mitochondrial energy production and NTP synthesis. Collectively, our comparative genomics results suggest multiple potential mechanisms associated with the H. vulgaris immortality and the aging traits of H. oligactis, providing novel targets for future functional studies. Significance statementWhy do some organisms age while others appear not to? The freshwater animal Hydra provides a unique opportunity to investigate this question, as closely related species display contrasting aging phenotypes. We generated a high-quality genome assembly for a new strain of a non-aging species and conducted comparative analyses with related strains and an aging species. Even closely related strains can accumulate substantial genetic divergence over time, and stable DNA modification patterns were associated with consistent gene activity, suggesting a mechanism that may help maintain cellular balance. Surprisingly, several well-known longevity genes are present in the aging species but absent in the non-aging one. This suggests that extended lifespan may not simply depend on possessing more "anti-aging" genes, but instead may reflect differences in how core biological processes are organized. Our study provides new insights into the genetic basis of aging and highlights Hydra as a powerful model for understanding longevity.

genomics↗

bioRxiv2025

Novel Biomaterial-Based Synovial Fluid Analysis Reveals Protective microRNA Signatures in a Mouse Model of Acute Synovitis-Driven Osteoarthritis

Acute synovitis and continuous mechanical stress are critical factors of Post-traumatic Osteoarthritis (PTOA); however, the effect on cartilage degeneration and its underlying mechanisms remains unclear. Here, we established a novel biomaterial-based method for synovial fluid analysis in mice to uncover the mechanisms underlying the onset of PTOA, focusing on synovitis and mechanical stress. Twelve-week-old C57BL/6J males were divided to the ACL-Transection (ACL-T), ACL-rupture (ACL-R), and Intact groups. We performed joint instability test and histological analysis for cartilage degeneration and synovitis at 2, 6, and 10 weeks. Real time PCR was performed on articular cartilage at 2 weeks and synovium at 2, 6, and 10 weeks. Tetra-slime was injected into the knee joint, and solidified slime containing synovial fluid molecules was analyzed in digital PCR at 2 weeks. Acute synovitis and cartilage degeneration were induced in the ACL-T group at 2 weeks, although no difference was observed in joint instability between both two ACL injury models. Real time PCR showed significant increase of Mmp-3, Tnf-, Ifn-{gamma}, and inos in synovium of the ACL-T group. During this tissue interaction, although there were no significant differences, miR145-5p and miR149-5p in synovial fluid were also upregulated in the ACL-T group compared to the ACL-R group. Unlike the early stage, no histological or biological differences were observed between groups at 6 and 10 weeks. In conclusion, acute synovitis caused secondary cartilage degeneration via MMP-3 and TNF- in the synovium during the early stage and may involve M1 macrophage activation. Whereas it was suggested that synovial fluid miRNA might be produced to suppress the secondary cartilage degeneration. Furthermore, mechanical stress was the dominant factor in the late stage of OA, regardless of the initial synovitis condition.

pathology↗

bioRxiv2024

Effectiveness of Exercise Intervention in Preventing Active Arthritis Exacerbation in an SKG Mouse Model of Rheumatoid Arthritis

ObjectivesTo investigate the effects of low-intensity exercise on active arthritis in an SKG mouse model of human rheumatoid arthritis (RA) pathology. MethodsTwenty-four female SKG mice were divided into three groups: sedentary (control), AR (induced arthritis), and AREx (induced arthritis plus low-intensity exercise). Arthritis was induced via intraperitoneal administration of mannan. After a 2-week inflammation period, low-intensity treadmill exercise was performed only in the AREx group. Arthritis was assessed weekly during the rearing period. After 4 weeks of exercise, histological and bone morphometric analyses of the right ankle joint were performed. A histological analysis of the gastrocnemius muscle was also performed. Bulk mRNA sequencing was conducted on the left synovial membrane-fat pad (SM-FP) complex. ResultsThe synovitis score showed no change; however, the arthritis score was significantly lower in the AREx group than in the AR group (p<0.05), indicating that low-intensity exercise suppressed arthritis exacerbation. The calcaneal and talar bone volumes decreased in the AR group, whereas the AREx group showed no significant change. In the SM-FP complex tissue, the gene expression of inflammatory cytokines decreased in the AREx group compared with the AR group, particularly the suppression of IL6/Jak/Stat3. Immunohistochemical analysis revealed significantly decreased expression of pro-inflammatory cytokines and increased expression of anti-inflammatory cytokines in the synovium of the AREx group compared with the AR group (p<0.05). ConclusionLow-intensity exercise therapy for active RA showed anti-inflammatory and suppressive effects on arthritis exacerbation in SKG mice, a mouse model of human RA pathology. Key messagesO_LIExercise had an anti-inflammatory effect on SKG mice, a mouse model of rheumatoid arthritis. C_LIO_LIExercise suppresses pro-inflammatory cytokine pathways such as IL6/Jak/Stat3 signalling in the synovial-fat complex tissue. C_LIO_LIExercise therapy is effective in improving the pathophysiology of active rheumatoid arthritis. C_LI

molecular biology↗

bioRxiv2024

Pigment-dispersing factor neuropeptides act as multifunctional hormones and modulators in tardigrades

Pigment-dispersing factors (PDFs) are neuropeptides that play key roles in controlling the circadian rhythms in various insects, whereas their function remains elusive in other protostomes including tardigrades (water bears). Here we show that the three PDFs of the tardigrade Hypsibius exemplaris are co-localized in two pairs of inner lobe cells in the brain, whereas only one PDF occurs in four additional cerebral and two extracerebral cells. The axons of the inner lobe cells pass through the contralateral brain hemisphere, descend to the ventral nerve cord and terminate in two pairs of potential release sites in the posteriormost trunk ganglion. Using in vitro assays, we demonstrate that all three PDFs and their deorphanized receptor (PDFR) are functional. Widespread localization of PDFR suggests that tardigrade PDFs may act as multifunctional hormones and neuromodulators that control major functions including light detection, neural processing, locomotion, feeding, digestion, osmoregulation, growth, embryonic development, and oogenesis/reproduction.

zoology↗

bioRxiv2024

Concurrent Joint Contact in Anterior Cruciate Ligament Injury induces cartilage micro-injury and subchondral bone sclerosis, resulting in knee osteoarthritis

ObjectiveAnterior Cruciate Ligament (ACL) injury initiates post-traumatic osteoarthritis (PTOA) via two distinct processes: initial direct contact injury of the cartilage surface during ACL injury, and secondary joint instability due to the ACL deficiency. Using the well-established Compression-induced ACL rupture method (ACL-R) and a novel Non-Compression ACL-R model, we aimed to reveal the individual effects of cartilage compression and joint instability on PTOA progression after ACL injury in mice. DesignTwelve-week-old C57BL/6J male were randomly divided to three experimental groups: Compression ACL-R, Non-Compression ACL-R, and Intact. Following ACL injury, we performed joint laxity testing and microscopic analysis of the articular cartilage surface at 0 days, in vivo optical imaging of matrix-metalloproteinase (MMP) activity at 3 and 7 days, and histological and microCT analysis at 0, 7, 14, and 28 days. ResultsThe Compression ACL-R group exhibited a significant increase of cartilage roughness immediately after injury compared with the Non-Compression group. At 7 days, the Compression group exhibited increased MMP-induced fluorescence intensity and MMP-13 positive cell ratio of chondrocytes. Moreover, histological cartilage degeneration was observable in the Compression group at the same time point. Sclerosis of tibial subchondral bone in the Compression group was more significantly developed than in the Non-Compression group at 28 days. ConclusionsBoth Compression and Non-Compression ACL injury initiated PTOA progression due to joint instability. However, joint contact during ACL rupture also caused initial micro-damage on the cartilage surface and initiated early MMP activity, which could accelerate PTOA progression compared to ACL injury without concurrent joint contact.

molecular biology↗

bioRxiv2024

Sexual dimorphism in the tardigrade Paramacrobiotus metropolitanus transcriptome

BackgroundIn gonochoristic animals, the sex determination pathway induces different morphological and behavioral features that can be observed between sexes, a condition known as sexual dimorphism. While many components of this sex differentiation cascade shows high levels of diversity, factors such as the Doublesex-Mab-3-related transcription factor (DMRT) are highly conserved throughout animals. Species of the phylum Tardigrada exhibits remarkable diversity in morphology and behavior between sexes, suggesting a pathway regulating such dimorphism. Despite the wealth of genomic and zoological knowledge accumulated in recent studies, the sexual differences in tardigrades genomes have not been identified. In this study, we focused on the gonochoristic species Paramacrobiotus metropolitanus and employed omics analyses to unravel the molecular basis of sexual dimorphism. ResultsTranscriptome analysis between sex identified numerous differentially expressed genes, of which approximately 2,000 male-biased genes were focused on 29 non-male-specific genomic loci. From these regions, we identified two Macrobiotidae family specific DMRT paralogs, which were significantly upregulated in males and lacked sex specific splicing variants. Furthermore, phylogenetic analysis indicated all tardigrade genomes lacks the doublesex ortholog, suggesting doublesex emerged after the divergence of Tardigrada. In contrast to sex-specific expression, no evidence of genomic difference between the sexes were found. We also identified several anhydrobiosis genes exhibiting sex-biased expression, possibly suggesting a mechanism for protection of sex specific tissues against extreme stress. ConclusionsThis study provides a comprehensive analysis for analyzing the genetic differences between sexes in tardigrades. The existence of male-biased, but not male-specific, genomic loci and identification of the family specific male-biased DMRT subfamily would provide the foundation for understanding the sex determination cascade. In addition, sex-biased expression of several tardigrade-specific genes which are involved their stress tolerance suggests a potential role in protecting sex-specific tissue and gametes.

zoology↗

bioRxiv2024

Post-embryonic tail development through molting of the freshwater shrimp Neocaridina denticulata

BackgroundUnderstanding postembryonic morphogenesis through molting in arthropods has recently become a focus of developmental biology. The hierarchical mechanisms of epithelial sheet folds play a significant role in this process. Drosophila is a well-studied model for holometabolous insects, with extensive research on imaginal disc growth. While developmental processes in other arthropods have been described, live imaging of morphological changes is challenging due to the macroscopic movements and hard cuticles. Neocaridina denticulata, a crustacean, presents unique tail morphogenesis through molting, which makes it the potential model. This study investigated the development of the tail in Neocaridina denticulata through histological analysis and in vivo live imaging using fluorescent probes. This study also performed long-read sequencing of the whole genome for future genetic tools. ResultsThe tail of Neocaridina was found to undergo two major changes with the first ecdysis. Firstly, the branches of the uropods are cleared, and secondly, the telson undergoes convergent elongation. Cross-sectional analysis revealed that uropod and telson branching occurs immediately after hatching in the form of cuticle branching. The surface structure of the developmental tail suggested that telson elongation is achieved by the extension of anisotropic furrows in the cuticle during ecdysis. Anisotropy of cuticle furrows was associated with the epithelial cell shape, and the anisotropy of cell shape was found to occur during development from post-hatching. We also established an in vivo live imaging system with UV-LED resin and detected the changes of tail development over time. in vivo live imaging analysis revealed that telson contraction occurs gradually prior to ecdysis. Furthermore, we have also provided a draft genome of Neocaridina. ConclusionNeocaridina denticulata is a valuable model for studying morphogenesis in arthropods through molting. The tail undergoes complex changes involving cuticle branching, anisotropic furrows, and cellular dynamics. in vivo live imaging system provides insights into the developmental process, and the draft genome enhances the potential for genetic tools in future studies. This research contributes to the understanding of arthropod morphogenesis and provides a foundation for further developmental and cytological investigations in Neocaridina.

developmental biology↗

bioRxiv2024

Transcriptome analysis of the tardigrade Hypsibius exemplaris exposed to the DNA-damaging agent bleomycin

Tardigrades are microscopic animals that are renowned for their capabilities of tolerating near-complete desiccation by entering an ametabolic state called anhydrobiosis. However, many species also show high tolerance against radiation in the active state as well, suggesting cross-tolerance via the anhydrobiosis mechanism. Previous studies utilized indirect DNA damaging agents to identify core components of the cross-tolerance machinery; however, it was difficult to distinguish whether transcriptomic changes were the result of DNA damage or residual oxidative stress. To this end, we performed transcriptome analysis on bleomycin-exposed Hypsibius exemplaris. We observed induction of several tardigrade-specific gene families that may be the core components of the cross-tolerance mechanism. We also identified an enrichment of the tryptophan metabolism pathway, which metabolomic analysis suggested the engagement of this pathway in stress tolerance. These results provide several candidates for the core component of the cross-tolerance, as well as possible anhydrobiosis machinery.

molecular biology↗

bioRxiv2023

Adolescent environmental enrichment induces social resilience and alters neural gene expression in a selectively bred rodent model with anxious phenotype

Stress is a major influence on mental health status; the ways that individuals respond to or copes with stressors determine whether they are negatively affected in the future. Stress responses are established by an interplay between genetics, environment, and life experiences. Psychosocial stress is particularly impactful during adolescence, a critical period for the development of mood disorders. In this study we compared two established, selectively-bred Sprague Dawley rat lines, the "internalizing" bred Low Responder (bLR) line versus the "externalizing" bred High Responder (bHR) line, to investigate how genetic temperament and adolescent environment impact future responses to social interactions and psychosocial stress, and how these determinants of stress response interact. Male bLR and bHR rats were exposed to social and environmental enrichment in adolescence prior to experiencing social defeat and were then assessed for social interaction and anxiety-like behavior. Adolescent enrichment caused rats to display more social interaction, as well as nominally less social avoidance, less submission during defeat, and resilience to the effects of social stress on corticosterone, in a manner that seemed more notable in bLRs. For bHRs, enrichment also caused greater aggression during a neutral social encounter and nominally during defeat, and decreased anxiety-like behavior. To explore the neurobiology underlying the development of social resilience in the anxious phenotype bLRs, RNA-seq was conducted on the hippocampus and nucleus accumbens, two brain regions that mediate stress regulation and social behavior. Gene sets previously associated with stress, social behavior, aggression and exploratory activity were enriched with differential expression in both regions, with a particularly large effect on gene sets that regulate social behaviors. Our findings provide further evidence that adolescent enrichment can serve as an inoculating experience against future stressors. The ability to induce social resilience in a usually anxious line of animals by manipulating their environment has translational implications, as it underscores the feasibility of intervention strategies targeted at genetically vulnerable adolescent populations.

neuroscience↗

bioRxiv2023

Characteristic differences in tibial subchondral bone changes in the post-traumatic knee osteoarthritis model

ObjectiveMeniscus degeneration and subchondral bone changes contribute to the development and progression of knee OA. The purpose of this study was to reveal the relationship between medial meniscus degeneration and characteristics of subchondral bone changes in different models DesignWe used the anterior cruciate ligament transection (ACL-T) model, destabilization of the medial meniscus (DMM) model, controlled abnormal tibial translation (CATT) model and a controlled abnormal tibial rotation (CATR) model with different mechanical stresses. We performed histological analysis and micro computed tomography analysis, at 4 and 6 weeks. In addition, we divided the tibial subchondral bone into four compartments and set the regions of interest ResultsMeniscus degeneration was observed in all groups, but there was no significant difference. The ACL-T group showed posterior displacement of the contact area, and the DMM and CATR groups showed lateral deviation of the medial meniscus. The region-specific subchondral bone changes in each model showed that changes in mechanical stress due to ACL and meniscus dysfunction, as well as changes in the contact area, affect the bony structure of the subchondral bone differently in each region. ConclusionsSubchondral bone changes in different models of mechanical stress were different in each region. In particular, changes in the contact area and increased compressive stress due to meniscus dysfunction were suggested to promote bone formation. The results of this study indicate that changes in alignment and contact area in the PTOA model may cause region-specific characteristics of the subchondral bone changes.

pathology↗

bioRxiv2022

Composition of minor ampullate silk makes its properties different from those of major ampullate silk

Spiders minor ampullate silk, or MI-silk, exhibits distinct mechanical properties and water resistance compared to its major ampullate counterpart (MA-silk). The principal protein constituent of MI-silk is known as minor ampullate spidroin, or MiSp, and while its sequence has been deciphered and is thought to underlie the differences in properties with MA-silk, the composition of MI-silk and the relationship between its composition and properties remain elusive. In this study, we set out to investigate the mechanical properties, water resistance, and proteome of MA-silk and MI-silk from Araneus ventricosus and Trichonephila clavata. We also synthesized artificial fibers from major ampullate spidroin, MaSp1 and 2, and MiSp to compare their properties. Our proteomic analysis reveals that the MI-silk of both araneids is composed of MiSp, MaSp1, and spidroin constituting elements (SpiCEs). The absence of MaSp2 in the MI-silk proteome and the comparison of the water resistance of artificial fibers suggest that the presence of MaSp2 is the reason for the disparity in water resistance between MI-silk and MA-silk.

molecular biology↗

bioRxiv2022

in vivo expression vector derived from anhydrobiotic tardigrade genome enables live imaging in Eutardigrada

Water is essential for life, but anhydrobiotic tardigrades can survive almost complete dehydration. Anhydrobiosis has been a biological enigma for more than a century with respect to how organisms sustain life without water, but the few choices of genetic toolkits available in tardigrade research have been a challenging circumstance. Here, we report the development of an in vivo expression system for tardigrades (the TardiVec system). TardiVec is based on a plasmid vector with promoters that originated from an anhydrobiotic tardigrade Ramazzottius varieornatus. It enables the introduction of GFP-fused proteins and genetically encoded indicators such as the Ca2+ indicator GCaMP into tardigrade cells; consequently, the dynamics of proteins and cells in tardigrades may be observed by fluorescence live imaging. This system is applicable for several tardigrades in the class Eutardigrada: the promoters of anhydrobiosis-related genes showed tissue-specific expression in this work. Surprisingly, promoters functioned similarly between multiple species, even for species with different modes of expression of anhydrobiosis-related genes, such as Hypsibius exemplaris, in which these genes are highly induced upon facing desiccation, and Thulinius ruffoi, which lacks anhydrobiotic capability. These results suggest that the highly dynamic expression changes in desiccation-induced species are regulated in trans. Tissue-specific expression of tardigrade-unique unstructured proteins also suggests differing anhydrobiosis machinery depending on the cell types. We believe that TardiVec opens up various experimental possibilities in tardigrade research, especially to explore anhydrobiosis mechanisms.

molecular biology↗

bioRxiv2022

Transcriptional Profiling of the Hippocampus in an F2 Cross of a Genetic Rat Model of Internalizing vs. Externalizing Behavior and Addiction Liability

Selectively-bred High Responder (bHR) and Low Responder (bLR) rats model the extreme externalizing and internalizing behavior accompanying many psychiatric disorders. To elucidate gene expression underlying these heritable behavioral differences, bHRs and bLRs (generation 37) were used to produce a F0-F1-F2 cross. We measured exploratory locomotion, anxiety-like behavior, and reward cue sensitivity (Pavlovian Conditioned Approach), and performed hippocampal RNA-Seq in male and female F0s (n=24) and F2s (n=250). Behaviors that diverged during selective breeding remained correlated in F2s, implying a shared genetic basis. F0 bHR/bLR differential expression was robust, surpassing differences associated with sex, and predicted expression patterns associated with F2 behavior. With bHR-like behavior, gene sets related to growth/proliferation were upregulated, whereas with bLR-like behavior, gene sets related to mitochondrial function, oxidative stress, and microglial activation were upregulated. This differential expression could be successfully predicted based on F0 genotype using cis-expression quantitative trait loci (cis-eQTLs) identified in the F2s. Colocalization of these cis-eQTLs with behavioral Quantitative Trait Loci pinpointed 16 differentially expressed genes that were strong candidates for mediating the influence of genetic variation on behavioral temperament. Our findings implicate hippocampal bioenergetic regulation of oxidative stress, microglial activation, and growth-related processes in shaping behavioral temperament, modulating vulnerability to psychiatric disorders.

neuroscience↗

bioRxiv2022

Abnormal Tibia Translation leads Directly the Surface Cartilage Degeneration with Molecular Biological Response using a Novel Non-Invasive ACL ruptured Mice Model

ObjectiveThe ACL-deficient model helps to clarify the mechanism of knee OA; however, the conventional ACL injury model could have included concurrent onset factors such as direct compression stress to cartilage and subchondral bone. In this study, we established a novel Non-invasive ACL-Ruptured mouse model without concurrent injuries and elucidated the relationship between OA progression and joint instability. DesignWe induced the ACL-Rupture non-invasively in twelve-week-old C57BL/6 male mice and evaluated histological, macroscopical, and morphological analysis at 0 days. Next, we created the ACL-R, controlled abnormal tibial translation (CATT), and Sham groups. Then, the joint stability and OA pathophysiology were analyzed at 2, 4, and 8 weeks. ResultsNo intra-articular injuries, except for ACL rupture, were observed in the ACL-R model. ACL-R mice increased anterior tibial displacement compared to the Sham group (p<0.001, 95% CI [-1.509 to -0.966]) and CATT group (p<0.001, 95% CI [-0.841 to -0.298]) at 8 weeks. All mice in the ACL-R group caused cartilage degeneration. The degree of cartilage degeneration in the ACL-R group was higher than in the CATT group (p=0.006) at 8 weeks. The MMP-3-positive cell rate of chondrocytes increased in the ACL-R group than CATT group from 4 weeks (p=0.043; 95% CI [-28.32 to -0.364]) while that of synovial cells increased at 8 weeks (p=0.031; 95% CI [-23.398 to -1.021]). ConclusionWe successfully established a Non-invasive ACL-R model without intra-articular damage. Our model revealed that chondrocytes might react to abnormal mechanical stress prior to synovial cells while the knee OA onset.

molecular biology↗