Malocclusion impairs cognitive behavior via AgRP signaling in adolescent mice.

Introduction: Occlusal disharmony induced by deteriorating oral health conditions, such as tooth loss and decreased masticatory muscle due to sarcopenia, is one of the causes of cognitive impairment. Chewing is an essential oral function for maintaining cognitive function not only in the elderly but also in young people. Malocclusion is an occlusal disharmony that commonly occurs in children. The connection between a decline in cognitive function and malocclusion in children has been shown with chronic mouth breathing, obstructive sleep apnea syndrome, and thumb/digit sucking habits. However, the mechanism of malocclusion-induced cognitive decline is not fully understood. We recently reported an association between feeding-related neuropeptides and cognitive decline in adolescent mice with activity-based anorexia. The aim of the present study was to assess the effects of malocclusion on cognitive behavior and clarify the connection between cognitive decline and hypothalamic feeding-related neuropeptides in adolescent mice with malocclusion. Methods: Four-week-old mice were randomly assigned to the sham-operated solid diet-fed (Sham/solid), sham-operated powder diet-fed (Sham/powder), or malocclusion-operated powder diet-fed (Malocclusion/powder) group. We applied composite resin to the mandibular anterior teeth to simulate malocclusion. We evaluated cognitive behavior using a novel object recognition (NOR) test, measured hypothalamic feeding-related neuropeptide mRNA expression levels, and enumerated c-Fos-positive cells in the hypothalamus 1 month after surgery. We also evaluated the effects of central antibody administration on cognitive behavior impairment in the NOR test. Results: The NOR indices were lower and the agouti-related peptide (AgRP) mRNA levels and number of c-Fos-positive cells were higher in the malocclusion/powder group than in the other groups. The c-Fos-positive cells were also AgRP-positive. We observed that the central administration of anti-AgRP antibody significantly increased the NOR indices. Discussion: The present study suggests that elevated cerebral AgRP signaling contributes to malocclusion-induced cognitive decline in adolescents, and the suppression of AgRP signaling can be a new therapeutic target against cognitive decline in occlusal disharmony.

A novel auxiliary device enhances miniscrew stability under immediate heavy loading simulating orthopedic treatment.

OBJECTIVES: To evaluate miniscrew stability and perform a histomorphometric analysis of the bone around the miniscrew under a load corresponding to orthopedic force. MATERIALS AND METHODS: Thirty-two miniscrews were implanted into eight rabbit tibias. Auxiliary group rabbits received auxiliary devices with miniscrews (n = 8, 28 days; n = 8, 56 days), and those in the nonauxiliary control group received miniscrews without auxiliary devices (n = 8, 28 days; n = 8, 56 days). Elastics were placed between miniscrews to apply a load of 5 N. Miniscrew stability was evaluated using a Periotest. Bone-to-implant contact (BIC) and spike implantation depth were measured histomorphologically. RESULTS: Periotest values in the auxiliary group were significantly lower than those in the nonauxiliary group at all time periods. There was no significant difference in BIC between the auxiliary and nonauxiliary groups at 28 or 56 days postimplantation. The implantation spike depth in the auxiliary group was significantly greater at 56 days compared to that at 28 days. Newly formed bone was observed around the spike of the auxiliary device at 56 days. CONCLUSIONS: The results suggest that the use of miniscrews in conjunction with auxiliary devices provides stable skeletal anchorage, which may be useful in orthopedic treatments.

Invasion of fish parasite Prosorhynchoides ozakii (Trematoda: Bucephalidae) into Lake Kasumigaura and surrounding rivers of eastern Japan.

In 2019 to 2021, the golden mussel Limnoperna fortunei and several freshwater fishes were sampled from 22 sites of the Tone River system including Lake Kasumigaura, Honshu, Japan, to examine the invasion of bucephalid trematodes. The parasite species identification was performed by morphological observation and DNA barcoding based on the sequences of nuclear 28S rDNA and mitochondrial cytochrome c oxidase subunit 1 (cox1). A total of 1719 mussels were collected from 10 sites, and trematode-infected mussels were detected from 8 sites with prevalences between 0.3 and 42.9%. The sporocysts and cercariae were identified as Prosorhynchoides ozakii, a newly introduced species in the river system. A total of 700 fish individuals belonging to 24 species were collected from 15 sites. Two species of catfishes (Silurus asotus and Ictalurus punctatus) harbored mature or immature adults of Pr. ozakii in the intestine with prevalences between 8.3 and 20% including both host species. The metacercariae of Pr. ozakii were found from the fins and epidermis of 13 fish species from 10 sites (prevalence 4.8-100%). Fishes were heavily infected with metacercariae in fins, which were surrounded by the infiltration of hemocytes and rodlet cells. A population genetic analysis of Pr. ozakii did not show an obvious bottleneck, suggesting the possibility that the parasite was intentionally and repeatedly introduced into the river system.

Resolution of cryptic species complexes within the genus Metagonimus (Trematoda: Heterophyidae) in Japan, with descriptions of four new species.

A nationwide fish survey was conducted in Japan to detect metacercariae of the genus Metagonimus (Trematoda: Heterophyidae). The metacercariae were subjected to DNA barcoding for molecular species identification. A phylogeny inferred from the sequences of mitochondrial cytochrome c oxidase subunit 1 (cox1) prompted us to recognize three cryptic species complexes (i.e., the M. miyatai complex, the M. takahashii complex, and the M. katsuradai complex). Each complex included one or two undescribed species. For morphological description, adult flukes of each species were raised through the experimental infections of immunosuppressed mice. We propose M. saitoi n. sp., M. kogai n. sp., M. shimazui n. sp., and M. kinoi n. sp., based on their phylogeny, morphology, biogeography, and ecology (host-parasite relationships). The originally described species, M. miyatai, was split into M. miyatai sensu stricto and M. saitoi n. sp. The former is distributed mainly in eastern Japan and uses the sweetfish (Plecoglossus altivelis) and daces (Pseudaspius hakonensis and Ps. sachalinensis) as principal second intermediate hosts, while the latter is in western Japan and its principal fish hosts are the dark chub (Nipponocypris temminckii) and the pale chub (Opsariichthys platypus). The present survey resolves a long-standing controversy on the microtaxonomy of Metagonimus in Japan since the first discovery of Metagonimus yokogawai in 1912, and shows that 10 species of Metagonimus are still distributed in Japan, although human metagonimiasis is almost eradicated.

Retrotransposons Manipulating Mammalian Skeletal Development in Chondrocytes.

Retrotransposons are genetic elements that copy and paste themselves in the host genome through transcription, reverse-transcription, and integration processes. Along with their proliferation in the genome, retrotransposons inevitably modify host genes around the integration sites, and occasionally create novel genes. Even now, a number of retrotransposons are still actively editing our genomes. As such, their profound role in the evolution of mammalian genomes is obvious; thus, their contribution to mammalian skeletal evolution and development is also unquestionable. In mammals, most of the skeletal parts are formed and grown through a process entitled endochondral ossification, in which chondrocytes play central roles. In this review, current knowledge on the evolutional, physiological, and pathological roles of retrotransposons in mammalian chondrocyte differentiation and cartilage development is summarized. The possible biological impact of these mobile genetic elements in the future is also discussed.

Screening of key candidate genes and pathways for osteocytes involved in the differential response to different types of mechanical stimulation using a bioinformatics analysis.

This study aimed to predict the key genes and pathways that are activated when different types of mechanical loading are applied to osteocytes. mRNA expression datasets (series number of GSE62128 and GSE42874) were obtained from Gene Expression Omnibus database (GEO). High gravity-treated osteocytic MLO-Y4 cell-line samples from GSE62128 (Set1), and fluid flow-treated MLO-Y4 samples from GSE42874 (Set2) were employed. After identifying the differentially expressed genes (DEGs), functional enrichment was performed. The common DEGs between Set1 and Set2 were considered as key DEGs, then a protein-protein interaction (PPI) network was constructed using the minimal nodes from all of the DEGs in Set1 and Set2, which linked most of the key DEGs. Several open source software programs were employed to process and analyze the original data. The bioinformatic results and the biological meaning were validated by in vitro experiments. High gravity and fluid flow induced opposite expression trends in the key DEGs. The hypoxia-related biological process and signaling pathway were the common functional enrichment terms among the DEGs from Set1, Set2 and the PPI network. The expression of almost all the key DEGs (Pdk1, Ccng2, Eno2, Egln1, Higd1a, Slc5a3 and Mxi1) were mechano-sensitive. Eno2 was identified as the hub gene in the PPI network. Eno2 knockdown results in expression changes of some other key DEGs (Pdk1, Mxi1 and Higd1a). Our findings indicated that the hypoxia response might have an important role in the differential responses of osteocytes to the different types of mechanical force.

Physiological role of urothelial cancer-associated one long noncoding RNA in human skeletogenic cell differentiation.

A vast number of long-noncoding RNAs (lncRNA) are found expressed in human cells, which RNAs have been developed along with human evolution. However, the physiological functions of these lncRNAs remain mostly unknown. In the present study, we for the first time uncovered the fact that one of such lncRNAs plays a significant role in the differentiation of chondrocytes and, possibly, of osteoblasts differentiated from mesenchymal stem cells, which cells eventually construct the human skeleton. The urothelial cancer-associated 1 (UCA1) lncRNA is known to be associated with several human malignancies. Firstly, we confirmed that UCA1 was expressed in normal human chondrocytes, as well as in a human chondrocytic cell line; whereas it was not detected in human bone marrow mesenchymal stem cells (hBMSCs). Of note, although UCA1 expression was undetectable in hBMSCs, it was markedly induced along with the differentiation toward chondrocytes, suggesting its critical role in chondrogenesis. Consistent with this finding, silencing of the UCA1 gene significantly repressed the expression of chondrogenic genes in human chondrocytic cells. UCA1 gene silencing and hyper-expression also had a significant impact on the osteoblastic phenotype in a human cell line. Finally, forced expression of UCA1 in a murine chondrocyte precursor, which did not possess a UCA1 gene, overdrove its differentiation into chondrocytes. These results indicate a physiological and important role of this lncRNA in the skeletal development of humans, who require more sustained endochondral ossification and osteogenesis than do smaller vertebrates.