Methylcobalamin promotes proliferation and migration and inhibits apoptosis of C2C12 cells via the Erk1/2 signaling pathway

Vibration acceleration enhances proliferation, migration, and maturation of C2C12 cells and promotes regeneration of muscle injury in male rats

Vibration acceleration (VA) using a whole-body vibration device is beneficial for skeletal muscles. However, its effect at the cellular level remains unclear. We aimed to investigate the effects of VA on muscles in vitro and in vivo using the C2C12 mouse myoblast cell line and cardiotoxin-induced injury in male rat soleus muscles. Cell proliferation was evaluated using the WST/CCK-8 assay and proportion of Ki-67 positive cells. Cell migration was assessed using wound-healing assay. Cell differentiation was examined by the maturation index in immunostained cultured myotubes and real-time polymerase chain reaction. Regeneration of soleus muscle in rats was assessed by recruitment of satellite cells, cross-sectional area of regenerated muscle fibers, number of centrally nucleated fibers, and conversion of regenerated muscle from fast- to slow-twitch. VA at 30 Hz with low amplitude for 10 min promoted C2C12 cell proliferation, migration, and myotube maturation, without promoting expression of genes related to differentiation. VA significantly increased Pax7-stained satellite cells and centrally nucleated fibers in injured soleus muscles on Day 7 and promoted conversion of fast- to slow-twitch muscle fibers with an increase in the mean cross-sectional area of regenerated muscle fibers on Day 14. VA enhanced the proliferation, migration, and maturation of C2C12 myoblasts and regeneration of injured rat muscles.

Cyanocobalamin promotes muscle development through the TGF-β signaling pathway

Cyanocobalamin (CNCbl, the compound name of Vitamin B12) is the only mineral vitamin that is essential for growth and development and cannot be produced by animals. Some studies have found that CNCbl can promote the proliferation and migration of C2C12 cells, but the mechanism by which it affects muscle development is still unknown. In this study, we elucidated the effect of CNCbl on muscle development and studied its underlying mechanism. CNCbl could promote the differentiation of C2C12 cells and upregulate Acvr1, p-Smad2 and p-Smad3 in the TGF-β signaling pathway in vitro. CD320 (the receptor in cell surface for binding with CNCbl transporter transcobalamin II) inhibition could reduce the uptake of CNCbl and significantly downregulate the expression of differentiation marker proteins MyoG and MYH2. Furthermore, the levels of p-Smad2 and p-Smad3 were also reduced with the inhibition of CD320, even though CNCbl was added to the C2C12 culture medium. In addition, the injection of CNCbl could accelerate the process of mouse muscle injury repair, enlarge the diameter of newly formed myofibers and upregulate the expression of MYH2, PAX7, CD320, Acvr1, p-Smad2 and p-Smad3 in vivo. These results suggest that CNCbl can promote muscle development and may play its role by regulating the expression of Acvr1, p-Smad2 and p-Smad3 related to the TGF-β signaling pathway.

Neuroprotective effects of methylcobalamin in cerebral ischemia/reperfusion injury through activation of the ERK1/2 signaling pathway

Despite advances in the understanding of the pathophysiology of ischemic stroke, therapeutic options remain limited. Methylcobalamin is an endogenous vitamin B12 that exhibits anti-inflammatory and antiapoptotic activities in a variety of diseases. In this study, we aimed to explore the neuroprotective effects and mechanism of action of methylcobalamin on cerebral ischemic injury in vitro and in vivo. The oxygen and glucose deprivation/reperfusion model and middle cerebral artery occlusion model were used to simulate cerebral ischemic injury in vitro and in vivo. Cell viability, inflammatory factors, cell apoptosis, and protein expression levels were determined. Further, autophagy flux and the cerebral infarction volume were measured. The modified neurological severity score, Longa score, Rotarod assay, and foot-fault test were used to evaluate behavioral changes and neurological deficits in rats. In vitro, methylcobalamin significantly increased cell viability, decreased lactate dehydrogenase release, attenuated inflammatory cytokine expression, reduced the apoptotic proportion, and enhanced autophagy flux after OGD treatment. In addition, Bcl-2 and Beclin1 expression levels and the LC3 II/I ratio were increased, whereas levels of Bax and cleaved caspase-3 were decreased. In vivo, methylcobalamin significantly reduced the cerebral infarction volume and neurological deficits in the rats. Furthermore, methylcobalamin activated the ERK1/2 pathway, whereas ERK1/2 inhibitors diminished its effects in the in vitro and in vivo models. In conclusion, methylcobalamin may exert a neuroprotective effect on cerebral ischemia and is a promising drug candidate for developing novel neuroprotective therapies.

A Nanofiber Sheet Incorporating Vitamin B12 Promotes Nerve Regeneration in a Rat Neurorrhaphy Model

Outcomes of peripheral nerve repair after injury are often suboptimal. Therefore, developing biological approaches to augment nerve regeneration is important. In this in vivo study, we tested the hypothesis that augmentation with an electrospun nanofiber sheet incorporating methylcobalamin (MeCbl) would be effective for regeneration after peripheral nerve transection and repair.

Methods

Rats were divided into 3 groups that either underwent sciatic nerve repair with or without the MeCbl sheet, or a sham operation. At 4 and/or 8 weeks after the operation, sensory and motor functional recovery, along with histological findings, were compared among the groups using the toe-spreading test, mechanical and thermal algesimetry tests, tibialis anterior muscle weight measurements, electrophysiological analyses, which included nerve conduction velocity (NCV), compound muscle action potential (CMAP), and terminal latency (TL), and histological analyses involving the myelinated axon ratio, axon diameter, and total axon number.

Results

Compared with the repair group without the MeCbl sheet, the repair group with the MeCbl sheet showed significant recovery in terms of tibialis anterior muscle weight, NCV and CMAP, and also tended to improve in the toe-spreading test, mechanical and thermal algesimetry tests, and TL. Histological analyses also demonstrated that the myelinated axon ratios and axon diameters were significantly higher. Among these findings, the repair group with the MeCbl sheet demonstrated the same recovery in NCV as the sham group.

Conclusion

This study demonstrated that electrospun nanofiber MeCbl sheets promoted nerve regeneration and functional recovery, indicating that this treatment strategy may be viable for human peripheral nerve injuries.

Methylcobalamin-Loaded PLCL Conduits Facilitate the Peripheral Nerve Regeneration

The feasible fabrication of nerve guidance conduits (NGCs) with good biological performance is important for translation in clinics. In this study, poly(d,l-lactide-co-caprolactone) (PLCL) films loaded with various amounts (wt; 5%, 15%, 25%) of methylcobalamin (MeCbl) are prepared, and are further rolled and sutured to obtain MeCbl-loaded NGCs. The MeCbl can be released in a sustainable manner up to 21 days. The proliferation and elongation of Schwann cells, and the proliferation of Neuro2a cells are enhanced on these MeCbl-loaded films. The MeCbl-loaded NGCs are implanted into rats to induce the regeneration of 10 mm amputated sciatic nerve defects, showing the ability to facilitate the recovery of motor and sensory function, and to promote myelination in peripheral nerve regeneration. In particular, the 15% MeCbl-loaded PLCL conduit exhibits the most satisfactory recovery of sciatic nerves in rats with the largest diameter and thickest myelinated fibers.

Combination of Electrospun Nanofiber Sheet Incorporating Methylcobalamin and PGA-Collagen Tube for Treatment of a Sciatic Nerve Defect in a Rat Model

BACKGROUND

For peripheral nerve defects, autografting is considered the therapeutic gold-standard treatment. However, this procedure leads to donor-site morbidity. While various artificial conduits have been recently developed, treatment outcome has been demonstrated to be poorer than that with autograft. In our previous study using a rat sciatic nerve crush injury model, we demonstrated that the delivery of electrospun nanofiber sheets incorporating methylcobalamin (MeCbl sheet) to the local site of a peripheral nerve injury promoted peripheral nerve regeneration. In this study, we examined the effects of combination therapy using an MeCbl sheet and a polyglycolic acid tube filled with collagen sponge (PGA-c) in a rat model of a 10-mm sciatic nerve defect.

METHODS

The rats were divided into 4 groups: (1) sham group (n = 10); (2) PGA-c group (n = 9), in which the gap was bridged using a PGA-c; (3) PGA-c/Sheet group (n = 8), in which the gap was bridged using a PGA-c wrapped in an MeCbl sheet; and (4) autograft group (n = 10), in which the gap was bridged using a reversed autograft. Motor and sensory function were evaluated, electrophysiological analysis was performed, and histomorphological findings were analyzed at 12 weeks postoperatively.

RESULTS

Compared with the PGA-c group, the PGA-c/Sheet group demonstrated significant improvements in the paw-withdrawal threshold expressed as a ratio relative to the contralateral side (mean difference [MD], -1.51; 95% confidence interval [CI], -2.64 to -0.38), terminal latency (MD, -0.86 ms; 95% CI, -1.56 to -0.16 ms), myelinated axon area (MD, 4.97%; 95% CI, 0.14% to 9.80%), proportion of myelinated axons (MD, 8.453%; 95% CI, 0.001% to 16.905%), and g-ratio (MD, -0.018; 95% CI, -0.035 to -0.001). No significant improvements were observed regarding motor function, electrophysiological findings with the exception of terminal latency, and axon numbers.

CONCLUSIONS

An MeCbl sheet in combination with a PGA-c significantly accelerated recovery with respect to sensory function, electrophysiology, and histomorphometry.

CLINICAL RELEVANCE

An MeCbl sheet may represent an effective therapeutic strategy for promoting regeneration across a nerve gap bridged with an artificial conduit.

Electrospun nanofiber sheets incorporating methylcobalamin promote nerve regeneration and functional recovery in a rat sciatic nerve crush injury model

Peripheral nerve injury is one of common traumas. Although injured peripheral nerves have the capacity to regenerate, axon regeneration proceeds slowly and functional outcomes are often poor. Pharmacological enhancement of regeneration can play an important role in increasing functional recovery. In this study, we developed a novel electrospun nanofiber sheet incorporating methylcobalamin (MeCbl), one of the active forms of vitamin B12 homologues, to deliver it enough locally to the peripheral nerve injury site. We evaluated whether local administration of MeCbl at the nerve injury site was effective in promoting nerve regeneration. Electrospun nanofiber sheets gradually released MeCbl for at least 8weeks when tested in vitro. There was no adverse effect of nanofiber sheets on function in vivo of the peripheral nervous system. Local implantation of nanofiber sheets incorporating MeCbl contributed to the recovery of the motor and sensory function, the recovery of nerve conduction velocity, and the promotion of myelination after sciatic nerve injury, without affecting plasma concentration of MeCbl.

STATEMENT OF SIGNIFICANCE

Methylcobalamin (MeCbl) is a vitamin B12 analog and we previously reported its effectiveness in axonal outgrowth of neurons and differentiation of Schwann cells both in vitro and in vivo. Here we estimated the effect of local administered MeCbl with an electrospun nanofiber sheet on peripheral nerve injury. Local administration of MeCbl promoted functional recovery in a rat sciatic nerve crush injury model. These sheets are useful for nerve injury in continuity differently from artificial nerve conduits, which are useful only for nerve defects. We believe that the findings of this study are relevant to the scope of your journal and will be of interest to its readership.

Low frequency pulsed electromagnetic field promotes C2C12 myoblasts proliferation via activation of MAPK/ERK pathway

Low frequency pulsed electromagnetic field (PEMF) has been shown to affect the activity of various cell types and promote them proliferation. However, its effect on skeletal muscle cells remains to be determined. In our study, we confirmed that PEMF (100 Hz, 1 mT) could promote C2C12 myoblasts proliferation by using Cell Counting Kit-8 (CCK-8) and 5-Ethynyl-2'-deoxyuridine (EdU) assays, yet hardly any distinction was found in the rate of cell apoptosis between PEMF and control groups by flow cytometry (Annexin V-FITC/PI double staining method). To further study the mechanism of action of PEMF, Western blot was utilized to detect the mitogen-activated protein kinase (MAPK) signaling pathways. After exposing C2C12 myoblasts to PEMF, we found the phosphorylation level of extracellular signal-regulated kinase (ERK) was significantly increased, while p38 MAPK and c-Jun N-terminal kinase (JNK) pathways were not affected. Pretreating the cells with the ERK kinase1/2 (MEK1/2) inhibitor U0126 obviously inhibited the proliferation of C2C12 cells. Taken together, our research for the first time demonstrated that PEMF promoted C2C12 myoblasts proliferation via activating MAPK/ERK pathway.

Methylcobalamin promotes the differentiation of Schwann cells and remyelination in lysophosphatidylcholine-induced demyelination of the rat sciatic nerve

Schwann cells (SCs) are constituents of the peripheral nervous system. The differentiation of SCs in injured peripheral nerves is critical for regeneration after injury. Methylcobalamin (MeCbl) is a vitamin B12 analog that is necessary for the maintenance of the peripheral nervous system. In this study, we estimated the effect of MeCbl on SCs. We showed that MeCbl downregulated the activity of Erk1/2 and promoted the expression of the myelin basic protein in SCs. In a dorsal root ganglion neuron–SC coculture system, myelination was promoted by MeCbl. In a focal demyelination rat model, MeCbl promoted remyelination and motor and sensory functional regeneration. MeCbl promoted the in vitro differentiation of SCs and in vivo myelination in a rat demyelination model and may be a novel therapy for several types of nervous disorders.