Potential Mechanism of Neurite Outgrowth Enhanced by Electrical Stimulation: Involvement of MicroRNA-363-5p Targeting DCLK1 Expression in Rat

Hmgcs2 is the hub gene in diabetic cardiomyopathy and is negatively regulated by Hmgcs2, promoting high glucose-induced cardiomyocyte injury

BACKGROUND

Diabetic cardiomyopathy (DCM) represents a major cause of heart failure and a large medical burden worldwide. This study screened the potentially regulatory targets of DCM and analyzed their roles in high glucose (HG)-induced cardiomyocyte injury.

METHODS

Through GEO database, we obtained rat DCM expression chips and screened differentially expressed genes. Rat cardiomyocytes (H9C2) were induced with HG. 3-hydroxy-3-methylglutarylcoenzyme A synthase 2 (Hmgcs2) and microRNA (miR)-363-5p expression patterns in cells were measured by real-time quantitative polymerase chain reaction or Western blot assay, with the dual-luciferase assay to analyze their binding relationship. Then, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay, lactate dehydrogenase assay, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, enzyme-linked immunosorbent assay, and various assay kits were applied to evaluate cell viability, cytotoxicity, apoptosis, inflammation responses, and oxidative burden.

RESULTS

Hmgcs2 was the vital hub gene in DCM. Hmgcs2 was upregulated in HG-induced cardiomyocytes. Hmgcs2 downregulation increased cell viability, decreased TUNEL-positive cell number, reduced HG-induced inflammation and oxidative stress. miR-363-5p is the upstream miRNA of Hmgcs2. miR-363-5p overexpression attenuated HG-induced cell injury.

CONCLUSIONS

Hmgcs2 had the most critical regulatory role in DCM. We for the first time reported that miR-363-5p inhibited Hmgcs2 expression, thereby alleviating HG-induced cardiomyocyte injury.

Neuromodulation for Peripheral Nerve Regeneration: Systematic Review of Mechanisms and In Vivo Highlights

While denervation can occur with aging, peripheral nerve injuries are debilitating and often leads to a loss of function and neuropathic pain. Although injured peripheral nerves can regenerate and reinnervate their targets, this process is slow and directionless. There is some evidence supporting the use of neuromodulation to enhance the regeneration of peripheral nerves. This systematic review reported on the underlying mechanisms that allow neuromodulation to aid peripheral nerve regeneration and highlighted important in vivo studies that demonstrate its efficacy. Studies were identified from PubMed (inception through September 2022) and the results were synthesized qualitatively. Included studies were required to contain content related to peripheral nerve regeneration and some form of neuromodulation. Studies reporting in vivo highlights were subject to a risk of bias assessment using the Cochrane Risk of Bias tool. The results of 52 studies indicate that neuromodulation enhances natural peripheral nerve regeneration processes, but still requires other interventions (e.g., conduits) to control the direction of reinnervation. Additional human studies are warranted to verify the applicability of animal studies and to determine how neuromodulation can be optimized for the greatest functional restoration.

Implantable Electrical Stimulation at Dorsal Root Ganglions Accelerates Osteoporotic Fracture Healing via Calcitonin Gene-Related Peptide

The neuronal engagement of the peripheral nerve system plays a crucial role in regulating fracture healing, but how to modulate the neuronal activity to enhance fracture healing remains unexploited. Here it is shown that electrical stimulation (ES) directly promotes the biosynthesis and release of calcitonin gene-related peptide (CGRP) by activating Ca2+ /CaMKII/CREB signaling pathway and action potential, respectively. To accelerate rat femoral osteoporotic fracture healing which presents with decline of CGRP, soft electrodes are engineered and they are implanted at L3 and L4 dorsal root ganglions (DRGs). ES delivered at DRGs for the first two weeks after fracture increases CGRP expression in both DRGs and fracture callus. It is also identified that CGRP is indispensable for type-H vessel formation, a biological event coupling angiogenesis and osteogenesis, contributing to ES-enhanced osteoporotic fracture healing. This proof-of-concept study shows for the first time that ES at lumbar DRGs can effectively promote femoral fracture healing, offering an innovative strategy using bioelectronic device to enhance bone regeneration.

Effects of Varied Stimulation Parameters on Adipose-Derived Stem Cell Response to Low-Level Electrical Fields

Exogenous electrical fields have been explored in regenerative medicine to increase cellular expression of pro-regenerative growth factors. Adipose-derived stem cells (ASCs) are attractive for regenerative applications, specifically for neural repair. Little is known about the relationship between low-level electrical stimulation (ES) and ASC regenerative potentiation. In this work, patterns of ASC expression and secretion of growth factors (i.e., secretome) were explored across a range of ES parameters. ASCs were stimulated with low-level stimulation (20 mV/mm) at varied pulse frequencies, durations, and with alternating versus direct current. Frequency and duration had the most significant effects on growth factor expression. While a range of stimulation frequencies (1, 20, 1000 Hz) applied intermittently (1 h × 3 days) induced upregulation of general wound healing factors, neural-specific factors were only increased at 1 Hz. Moreover, the most optimal expression of neural growth factors was achieved when ASCs were exposed to 1 Hz pulses continuously for 24 h. In evaluation of secretome, apparent inconsistencies were observed across biological replications. Nonetheless, ASC secretome (from 1 Hz, 24 h ES) caused significant increase in neurite extension compared to non-stimulated control. Overall, ASCs are sensitive to ES parameters at low field strengths, notably pulse frequency and stimulation duration.

Electrical stimulation of neural-differentiating iPSCs on novel coaxial electroconductive nanofibers

Neural tissue engineering strategies are paramount to create fully mature neurons, necessary for new therapeutic strategies for neurological diseases or the creation of reliable in vitro models. Scaffolds can provide physical support for these neurons and enable cues for enhancing neural cell differentiation, such as electrical current. Coaxial electrospinning fibers, designed to fulfill neural cell needs, bring together an electroconductive shell layer (PCL-PANI), able to mediate electrical stimulation of cells cultivated on fibers mesh surface, and a soft core layer (PGS), used to finetune fiber diameter (951 ± 465 nm) and mechanical properties (1.3 ± 0.2 MPa). Those dual functional coaxial fibers are electroconductive (0.063 ± 0.029 S cm-1, stable over 21 days) and biodegradable (72% weigh loss in 12 hours upon human lipase accelerated assay). For the first time, the long-term effects of electrical stimulation on induced neural progenitor cells were studied using such fibers. The results show increase in neural maturation (upregulation of MAP2, NEF-H and SYP), up-regulation of glutamatergic marker genes (VGLUT1 - 15-fold) and voltage-sensitive channels (SCN1α - 12-fold, CACNA1C - 32-fold), and a down-regulation of GABAergic marker (GAD67 - 0.09-fold), as detected by qRT-PCR. Therefore, this study suggest a shift from an inhibitory to an excitatory neural cell profile. This work shows that the PGS/PCL-PANI coaxial fibers here developed have potential applications in neural tissue engineering.

Neural circuit repair after central nervous system injury

Central nervous system injury often causes lifelong impairment of neural function, because the regenerative ability of axons is limited, making a sharp contrast to the successful regeneration that is seen in the peripheral nervous system. Nevertheless, partial functional recovery is observed, because axonal branches of damaged or undamaged neurons sprout and form novel relaying circuits. Using a lot of animal models such as the spinal cord injury model or the optic nerve injury model, previous studies have identified many factors that promote or inhibit axonal regeneration or sprouting. Molecules in the myelin such as myelin-associated glycoprotein, Nogo-A or oligodendrocyte-myelin glycoprotein, or molecules found in the glial scar such as chondroitin sulfate proteoglycans, activate Ras homolog A (RhoA) signaling, which leads to the collapse of the growth cone and inhibit axonal regeneration. By contrast, axonal regeneration programs can be activated by many molecules such as regeneration-associated transcription factors, cyclic AMP, neurotrophic factors, growth factors, mechanistic target of rapamycin or immune-related molecules. Axonal sprouting and axonal regeneration largely share these mechanisms. For functional recovery, appropriate pruning or suppressing of aberrant sprouting are also important. In contrast to adults, neonates show much higher sprouting ability. Specific cell types, various mouse strains and different species show higher regenerative ability. Studies focusing on these models also identified a lot of molecules that affect the regenerative ability. A deeper understanding of the mechanisms of neural circuit repair will lead to the development of better therapeutic approaches for central nervous system injury.

Combining feature selection and shape analysis uncovers precise rules for miRNA regulation in Huntington's disease mice

Background

MicroRNA (miRNA) regulation is associated with several diseases, including neurodegenerative diseases. Several approaches can be used for modeling miRNA regulation. However, their precision may be limited for analyzing multidimensional data. Here, we addressed this question by integrating shape analysis and feature selection into miRAMINT, a methodology that we used for analyzing multidimensional RNA-seq and proteomic data from a knock-in mouse model (Hdh mice) of Huntington’s disease (HD), a disease caused by CAG repeat expansion in huntingtin (htt). This dataset covers 6 CAG repeat alleles and 3 age points in the striatum and cortex of Hdh mice.

Results

Remarkably, compared to previous analyzes of this multidimensional dataset, the miRAMINT approach retained only 31 explanatory striatal miRNA-mRNA pairs that are precisely associated with the shape of CAG repeat dependence over time, among which 5 pairs with a strong change of target expression levels. Several of these pairs were previously associated with neuronal homeostasis or HD pathogenesis, or both. Such miRNA-mRNA pairs were not detected in cortex.

Conclusions

These data suggest that miRNA regulation has a limited global role in HD while providing accurately-selected miRNA-target pairs to study how the brain may compute molecular responses to HD over time. These data also provide a methodological framework for researchers to explore how shape analysis can enhance multidimensional data analytics in biology and disease.

Neural responses to electrical stimulation in 2D and 3D in vitro environments

Electrical stimulation (ES) to manipulate the central (CNS) and peripheral nervous system (PNS) has been explored for decades, recently gaining momentum as bioelectronic medicine advances. The application of ES in vitro to modulate a variety of cellular functions, including regenerative potential, migration, and stem cell fate, are being explored to aid neural degeneration, dysfunction, and injury. This review describes the materials and approaches for the application of ES to the PNS and CNS microenvironments, towards an improved understanding of how ES can be harnessed for beneficial clinical applications. Emphasized are some recent advances in ES, including conductive polymers, methods of charge transfer, impact on neural cells, and a brief overview of alternative methodologies for cellular targeting including magneto, ultrasonic, and optogenetic stimulation. This review will examine how heterogenous cell populations, including neurons, glia, and neural stem cells respond to a wide range of conductive 2D and 3D substrates, stimulation regimes, known mechanisms of response, and how cellular sources impact the response to ES.

Emerging role of MicroRNAs in peripheral nerve system

Peripheral nerve injury is one of the most common clinical diseases. Although the regeneration of the peripheral nerve is better than that of the nerves of the central nervous system, because of its growth rate restrictions after damage. Hence, the outcome of repair after injury is not favorable. Small RNA, a type of non-coding RNA, has recently been gaining attention in neural injury. It is widely distributed in the nervous system in vivo and a significant change in the expression of small RNAs has been observed in a neural injury model. This suggests that MicroRNAs (miRNAs) may serve as a potential target for resolving the challenges of peripheral nerve repair. This review summarizes the current challenges in peripheral nerve injury repair, systematically expounds the mechanism of miRNAs in the process of nerve injury and repair and attempts to determine the possible treatment of peripheral nerve injury.

miR-424-5p regulates cell proliferation, migration and invasion by targeting doublecortin-like kinase 1 in basal-like breast cancer

Our previous study has showed doublecortin like kinase 1 (DCLK1) serves as an oncogene to regulate basal-like breast cancer cell proliferation, migration and invasion, and is associated with malignant status and poor prognosis. The aim of this study is to identify microRNAs (miRNAs), which target DCLK1 to regulate basal-like breast cancer cell proliferation, migration and invasion. In our results, we observed that miR-424-5p expression was decreased in basal-like breast cancer tissues and cell lines. Furthermore, we found 3'-UTR of DCLK1 had binding site of miR-424-5p based on microRNA target databases, and there was an inverse correlation between miR-424-5p and DCLK1 in basal-like breast cancer tissues. Moreover, we confirmed miR-424-5p directly targeted to 3'-UTR of DCLK1 through luciferase reporter assay, and miR-424-5p negatively regulated DCLK1 mRNA and protein expressions through qRT-PCR and western blot. The gain-of-function studies showed that miR-424-5p suppressed basal-like breast cancer cell proliferation, migration and invasion. The rescued-function studies suggested up-regulation of DCLK1 could rescue inhibition of miR-424-5p mimics in the regulation of basal-like breast cancer cell proliferation, migration and invasion. Finally, low-expression of miR-424-5p was associated with advanced clinical stage, large tumor size, more metastatic lymph nodes, present distant metastasis and poor histological grade in basal-like breast cancer patients. In conclusion, miR-424-5p is a tumor suppressive microRNA to regulate tumor cell proliferation, migration and invasion via binding to the functional target DCLK1, and associated with malignant status in basal-like breast cancer.