Kajiwara, Y. | Search bioRxiv

bioRxiv2020

Effect of belt electrode-skeletal muscle electrical stimulation on immobilization-induced muscle fibrosis

PurposeMacrophage accumulation in response to decreasing myonuclei may be the major mechanism underlying immobilization-induced muscle fibrosis in muscle contracture, an intervention strategy suppressing these lesions is necessary. Therefore, this research investigated the effect of belt electrode-skeletal muscle electrical stimulation (B-SES), a new electrical stimulation device, to the macrophage accumulation via myonuclei decrease in immobilization-induced muscle fibrosis. Materials and Methods18 Wistar male rats were divided into the control group, immobilization group (with plaster cast fixation to immobilize the soleus muscles in a shortened position for 2 weeks), and B-SES group (with muscle contractile exercise through B-SES during the immobilization period). B-SES stimulation was performed at a frequency of 50 Hz and an intensity of 4.7 mA, muscle contractile exercise by B-SES was applied to the lower limb muscles for 20 minutes/session (twice a day) for 2 weeks (6 times/week). The bilateral soleus muscles were used for histological, immunohistochemical, biochemical, and molecular biological analyses. ResultsThe number of myonuclei was significantly higher in the B-SES group than in the immobilization group, and there was no significant difference between the B-SES and control groups. The cross-sectional area of type I and II myofibers in the immobilization and B-SES groups was significantly lower than that in the control group, and the cross-sectional area of type I myofibers in the B-SES group was higher than that in the immobilization group. However, Atrogin-1 and MuRF-1 mRNA expression in the immobilization and B-SES groups was significantly higher than those in the control group. Additionally, the number of macrophages, IL-1{beta}, TGF-{beta}1, and -SMA mRNA expression, and hydroxyproline expression was significantly lower in the control and B-SES groups than those in the immobilization group. ConclusionThis research surmised that muscle contractile exercise through B-SES prevented immobilization-induced muscle fibrosis, and this alteration suppressed the development of muscle contracture.

pathology↗

bioRxiv2018

Behavioral phenotyping of an improved mouse model of Phelan-McDermid Syndrome with a complete deletion of the Shank3 gene

AbstractPhelan-McDermid Syndrome (PMS) is a rare genetic disorder in which one copy of the SHANK3 gene is missing or mutated, leading to a global developmental delay, intellectual disability, and autism. Multiple intragenic promoters and alternatively spliced exons are responsible for the formation of numerous isoforms. Many genetically-modified mouse models of PMS have been generated but most disrupt only some of the isoforms. In contrast, the vast majority of known SHANK3 mutations found in patients involve deletions that disrupt all isoforms. Here, we report the production and thorough behavioral characterization of a new mouse model in which all Shank3 isoforms are disrupted. Our mice are more severely affected than previously published models. While the deficits were typically more pronounced in homozygotes, an intermediate phenotype was observed for heterozygotes in many paradigms. As in other Shank3 mouse models, stereotypies, including increased grooming, were observed. Additionally, both sensory and motor deficits were detected in neonatal and adult mice. While social behaviors were not strongly impacted, Shank3-deficient mice displayed a strong escape behavior and avoidance of inanimate objects indicating increased novelty-induced anxiety. Similarly, increased freezing was observed during fear conditioning training and amygdala-dependent cued retrieval. Finally, deficits were observed in both initial training and reversal in the Barnes maze and in contextual fear memory that are memory tasks involving hippocampal-prefrontal circuits. This new mouse model of PMS, engineered to most closely represent human mutations, recapitulates core symptoms of PMS providing improvements for both construct and face validity, compared to previous models.\n\nSignificant statementPhelan-McDermid syndrome, caused by happloinsufficiency of Shank3, is a severe and complex neurodevelopmental disorder. This study investigates the behavioral consequences of a disruption of all Shank3 isoforms in neonatal and adult mice using a detailed battery of tests tailored to investigate core symptoms and usual comorbidities of PMS. We found that our new model is more severely affected than previously published mouse models with only partial deletions of Shank3 and more closely recapitulates symptoms of PMS thus providing improvements for both construct and face validity. Our results highlight the significance of using a mouse model with a complete deletion of Shank3 for studying mechanisms underlying autism spectrum disorder and PMS, carrying preclinical studies and testing test novel therapeutic approaches.

animal behavior and cognition↗