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BACKGROUND: Circular RNAs (circRNAs) were initially regarded as by-products of aberrant splicing. Present research on their mechanism has gradually penetrated to the molecular level. Many studies have shown that circRNAs participate in osteogenic differentiation through various ways and play a key role. OBJECTIVE: To discuss the research progress of circRNAs during osteogenic differentiation in human mesenchymal stem cells. METHODS: Using “circRNAs, human mesenchymal stem cells, osteogenic differentiation” as keywords in English and Chinese. PubMed, Web of Science, CNKI, and Wanfang were searched for relevant articles on circRNAs in human mesenchymal stem cells published from 1993 to 2020. Types of retrieved articles included reviews, research papers, and books. RESULTS AND CONCLUSION: CircRNAs play an important role in the osteogenesis of mesenchymal stem cells. These circRNAs have proven to be key targets for the diagnosis and treatment of bone diseases. However, the molecular mechanism of circRNA in osteogenic differentiation needs further research, and in vivo experiments are also needed to support existing conclusions. [ABSTRACT FROM AUTHOR]

BACKGROUND: Muscle weakness is a common symptom after coronavirus disease 2019 (COVID-19) infection and affects the ability to perform daily activities in humans during recovery. Low-frequency pulsed magnetic field stimulation at a strength of 1.5 mT and a frequency of 3 300 Hz can enhance the maximal voluntary contraction and strength endurance of human skeletal muscle by inducing and activating classical transient receptor potential channel 1 (TRPC1), which produces a series of pathological support effects on muscle tissue. It has not been studied whether this means will improve muscle weakness in patients recovering from COVID-19. OBJECTIVE: To select the low-frequency pulsed magnetic field for magnetic stimulation of lower limb muscle groups in patients with COVID-19, in order to observe the effect of this stimulation on the improvement of muscle weakness of lower limb muscle groups in patients with COVID-19 during the recovery period. METHODS: Fourteen patients infected with COVID-19 (Omicron strain) positive for Innovita COVID-19 Ab Test (Colloidal Gold) and accompanied by muscle weakness were recruited and randomly divided into two groups: a test group receiving magnetic field stimulation and a control group receiving sham treatment, respectively. The total duration of the trial was 3 weeks. The test group was given low-frequency pulsed magnetic stimulation of the lower limbs every 48 hours and the control group was given the same intervention procedure as the test group but with sham stimulation. Patients in both groups were not informed whether the magnetic stimulation apparatus was running or not. Nine sessions were performed in both groups and the changes in the maximum voluntary contraction, explosive leg force and strength endurance of the local muscle groups of the lower limbs were subsequently observed in both groups. RESULTS AND CONCLUSION: Among the eight local muscle groups collected, seven local muscle groups in the test group showed an increase in the maximum voluntary contraction value after 3 weeks of low-frequency pulsed magnetic field stimulation. In the control group, there were only three muscle groups with improvement in the maximum voluntary contraction. The rate of improvement in the anterior and posterior muscle groups of the left leg in the test group was significantly higher than that in the control group. The longitudinal jump height and peak angular velocity of the knee joint in both groups were improved compared with the pre-test measurement, and the elevation rate of jumping height in the test group was higher than that in the control group. Under the fatigue condition, the decline rates of peak angular velocity of the knee joint and jumping height in the test group decreased significantly, while those in the control group did not change significantly. The above data confirmed that the low-frequency pulsed magnetic field stimulation with the intensity of 1.5 mT and frequency of 3 300 Hz could improve the muscle strength of more local muscle groups in the lower limbs of patients with COVID-19 during the recovery period compared with the human self-healing process, and the whole-body coordination ability and functional status based on explosive leg force of the legs could be significantly improved. Therefore, low-frequency pulsed magnetic field stimulation can be used as an effective, non-exercise rehabilitation tool to improve muscle weakness in the lower limbs of patients with COVID-19. [ABSTRACT FROM AUTHOR]

BACKGROUND: Exposure to transient low-frequency pulsed magnetic field can induce and activate classical transient receptor potential channel 1, and enhance the maximal voluntary contraction force and strength endurance of local muscles, such as biceps brachii. OBJECTIVE: To use a specific low-frequency pulsed magnetic field that can activate classical transient receptor potential channel 1 as a means of improving muscle strength and to observe the attenuation process of the maximal voluntary contraction force and strength endurance of human biceps brachii after short-term stimulation. METHODS: A total of 27 normal adult healthy subjects were selected and randomly divided into training group, exposure group, and training+exposure group. The training+exposure group received resistance training immediately after 10-minute exposure to low-frequency pulsed magnetic field; the exposure group was only exposed to low-frequency pulsed magnetic field for 10 minutes; and the training group only received resistance training. The trial duration was 8 weeks. At 1-12 days of the trial, short-term muscle strength enhancement scheme was performed and post-test muscle strength was measured. The attenuation process of maximum voluntary contraction force and strength endurance was then observed in the following 6 weeks. RESULTS AND CONCLUSION: (1) The maximum voluntary contraction force value of all subjects changed significantly over time (P < 0.01), with obvious timedependent interaction effect but no interaction effect between groups, and there was no significant difference between time- and grouping-dependent interaction effects. (2) In the 1st, 2nd, 3rd, and 4th weeks, the maximum voluntary contraction force values for strength attenuation in the exposure group were significantly higher than the initial value. In the 1st and 4th weeks, the maximum voluntary contraction force values for strength attenuation in the training group were significantly higher than the initial value. In the 5th and 6th weeks, the maximum voluntary contraction force values for strength attenuation in the exposure group and training group were significantly lower than the post-test value. In the 1st, 5th, and 6th weeks, the maximum voluntary contraction force values for strength attenuation in the training+exposure group were significantly lower than the post-test value. (3) The correlation analysis of the maximal voluntary contraction force curves in the three groups indicated that the overall changes in the maximal voluntary contraction force in the exposure group were highly positively correlated with the variation trend of maximum voluntary contraction force in the training group and training+exposure group. Their variation trend was highly consistent. Compared with the exposure group, the training group showed stronger positive correlation with the training+exposure group in terms of the maximum voluntary contraction force. (4) The median frequency value of the subjects in each group changed significantly with time (P < 0.01), and there was significant time-dependent interaction effect. Time- and grouping-dependent interactions led to significant changes in the median frequency values (P < 0.01). (5) In the 2nd week, the median frequency values of muscle strength attenuation in the exposure group and training+exposure group was significantly higher than the initial value. However, compared with the post-test value, the median frequency values of muscle strength attenuation showed no significant changes in the exposure group. In the 1st and 4nd weeks, the median frequency values of muscle strength attenuation in the training group were significantly lower than the post-test value. In the 1st and 2th weeks, the median frequency values of muscle strength attenuation in the training+exposure group were significantly lower than the post-test value. (6) The correlation analysis of the median frequency change curves in the three groups indicated that the training+exposure group showed a lower positive correlation with the training group and exposure group. However, compared with the training group, the exposure group had a higher correlation with the training+exposure group. (7) After exposure to the short-term pulsed magnetic field with the intensity of 1.5 mT and the frequency of 3 300 Hz, the maximum voluntary contraction force value of muscle strength attenuates to the initial value within 6 weeks, consistent with the attenuation period of resistance training and attenuation speed after enhancement of muscle strength. During the attenuation process, there is less fluctuation in the two resistance training groups, without fatigue accumulation, in which muscle strength can be better maintained. Improved strength endurance can be maintained for at least 6 weeks. Compared with the resistance training, low-frequency pulsed magnetic field stimulation can avoid fatigue accumulation, and the anti-fatigue ability continues to increase and maintain at a better level. Resistance training combined with pulsed magnetic field has a certain benefit for endurance level. To reduce the fluctuation during the attenuation process is beneficial to the maintenance of the endurance level. [ABSTRACT FROM AUTHOR]

BACKGROUND: Strength quality is an essential element for human physical activity. Short-term low-frequency pulsed electrical magnetic field (PEMF) stimulation can activate classical transient receptor potential channel 1 (TRPC1) and trigger skeletal muscle growth and remodeling in mice, thereby producing a series of physiological support effects on muscle tissue. However, there is no report on whether this mechanism will alter the physiological structure and working ability of human skeletal muscle and act as a new way to improve muscle strength. OBJECTIVE: To select a specific low-frequency PEMF that can activate TRPC1 as an exogenous stimulus to observe and verify the effect of short-term stimulation on the maximum voluntary contraction force and strength endurance of human biceps brachii. METHODS: A total of 27 normal adult healthy subjects were selected and randomly divided into exercise group, PEMF group, and exercise+PEMF group, with 9 cases in each group. The training group was subjected to resistance training. The exercise+PEMF group received 10-min low-frequency PEMF stimulation (intensity 1.5 mT, frequency 3300 Hz) immediately after resistance training. The irradiation group only received 10-minute low-frequency PEMF stimulation. Training or irradiation was performed every 48 hours for 9 days. Electromyography information on the maximum voluntary contraction force was collected before and after five training sessions in the exercise group and the exercise+PEMF group, to observe whether the combination of low-frequency PEMF and resistance training will produce a gain effect. In the PEMF group, the maximum voluntary contraction force was tested only at the 1st, 3rd, and 5th sessions to track the changes in muscle strength. The maximum voluntary contraction force, one-repetition maximum force, endurance duration and median frequency were observed in each group. RESULTS AND CONCLUSION: (1) During the trial, there were significant interaction effects between the changes in maximum voluntary contraction force and time in all the subjects (P < 0.01) as well as in each group as time goes by (P < 0.05). However, there was no interaction effect between groups. (2) There was a significant improvement in the maximum voluntary contraction force, one-repetition maximum force, endurance duration, and median frequency in each group after completion of the trial. These indicators were successively improved by 19%, 23%, 28%, and 18% in the exercise group, 11%, 10%, 53%, and 18% in the exercise+PEMF group, and 28%, 18%, 27%, and 6% in the PEMF group. (3) The median frequency of the exercise+PEMF group was significantly higher than that of the PEMF group (P < 0.05), but there was no significant difference between the exercise+PEMF group and exercise group. (4) Compared with the exercise+PEMF group, the exercise group showed a significant decrease in the root mean square of maximum voluntary contraction after the first two exercise sessions (P < 0.05). (5) All these findings indicate that the short-term PEMF stimulation with intensity of 1.5 mT and frequency of 3 300 Hz can significantly improve the maximum voluntary contraction force and strength endurance of human biceps brachii. That is, low-frequency PEMF can induces TRPC1 to promote the working ability of muscle tissue, which has been effectively verified in human body. Low-frequency PEMF stimulation shares similar effects with conventional resistance training in terms of enhancing the maximum strength. Resistance training combined with PEMF stimulation shows better anti-fatigue ability and stabilizes the increase of muscle strength. This combination can stimulate more motor units of local muscle groups under the same load in the early stage of training and improve the overall training efficiency. In terms of strength endurance improvement, low-frequency PEMF stimulation can prolong isometric muscle contraction time and improve anti-fatigue ability. Compared with simple low-frequency PEMF stimulation, low-frequency PEMF stimulation combined with resistance training is more effective to develop strength endurance. [ABSTRACT FROM AUTHOR]

BACKGROUND: Previous studies have found that panax notoginseng saponins have a certain protective effect on immunological liver injury in mice. OBJECTIVE: To explore the therapeutic effect of notoginsenoside R1 on carbon tetrachloride-induced liver fibrosis in rats. METHODS: Experimental liver fibrosis model was made by carbon tetrachloride in male Sprague-Dawley rats. Then 30 g/L notoginsenoside R1 (60 mg/kg) was given once daily for 4 and 6 weeks in the treatment group. Rats in the control and model group were given distilled water of the same volume. Histopathological observation with hematoxylin-eosin staining and Masson’s trichrome staining was used to evaluate the changes of liver structure and fibrosis degree. The expression of collage type I, α-smooth muscle actin and transforming growth factor-β1 mRNA of hepatic tissue was measured by qRT-PCR method. The experimental protocol was approved by the Animal Experiment Ethics Committee of Kunming Medical University (approval No. KMMU2018018). RESULTS AND CONCLUSION: Liver histopathology showed that notoginsenoside R1 improved the degree of liver fibrosis. The expression levels of collagen type I, α-smooth muscle actin and transforming growth factor-β1 mRNA were reduced significantly in the treatment group compared with the model group (P < 0.05). But there was no significant difference after 4 and 6 weeks of treatment with notoginsenoside R1. Overall findings indicate that notoginsenoside R1 can slow down the progression of carbon tetrachloride-induced liver fibrosis in rats to a certain extent. [ABSTRACT FROM AUTHOR]