Sciatic nerve regeneration in KLF7-transfected acellular nerve allografts

Understanding the role of potential biomarkers in attenuating multiple sclerosis progression via multiomics and network-based approach

BACKGROUND

Multiple sclerosis (MS) is a complex neurological disorder marked by neuroinflammation and demyelination. Understanding its molecular basis is vital for developing effective treatments. This study aims to elucidate the molecular progression of MS using multiomics and network-based approach.

METHODS

We procured differentially expressed genes in MS patients and healthy controls by accessing mRNA dataset from a publicly accessible database. The DEGs were subjected to a non-trait weighted gene co-expression network (WGCN) for hub DEGs identification. These hub DEGs were utilized for enrichment, protein-protein interaction network (PPIN), and feed-forward loop (FFL) analyses.

RESULTS

We identified 880 MS-associated DEGs. WGCN revealed a total of 122 hub DEGs of which most significant pathway, gene ontology (GO)-biological process (BP), GO-molecular function (MF) and GO-cellular compartment (CC) terms were assembly and cell surface presentation of N-methyl-D-aspartate (NMDA) receptors, regulation of catabolic process, NAD(P)H oxidase H2O2 forming activity, postsynaptic recycling endosome. The intersection of top 10 significant pathways, GO-BP, GO-MF, GO-CC terms, and PPIN top cluster genests identified STAT3 and CREB1 as key biomarkers. Based on essential centrality measures, CREB1 was retained as the final biomarker. Highest-order subnetwork FFL motif comprised one TF (KLF7), one miRNA (miR-328-3p), and one mRNA (CREB1) based on essential centrality measures.

CONCLUSIONS

This study provides insights into the roles of potential biomarkers in MS progression and offers a system-level view of its molecular landscape. Further experimental validation is needed to confirm these biomarkers' significance, which will lead to early diagnostic and therapeutic advancements.

Functional and structural neurodegenerative activities of Ankaferd BloodStopper in a mouse sciatic nerve model

Traumatic and postoperative hemorrhages are life-threatening complications. Ankaferd BloodStopper (ABS) is a potent topical hemostatic agent to stop bleeding. However, ABS is associated with nerve toxicity. The present study aimed to investigate the functional and structural neurodegenerative effects of ABS in a mouse model. A total of 30 male BALB/c mice, aged 6-8 weeks, were randomly divided into control group (no treatment), a sham group (treated with saline) and an experimental group (treated with ABS). In the saline and the ABS groups, the right sciatic nerve was surgically exposed and treated with saline or ABS, respectively. No surgical procedure was performed in the control group. On day 7 post-treatment, functional changes of the sciatic nerve were evaluated by a horizontal ladder rung walking task. Structural changes were assessed with immunohistochemistry. In the horizontal ladder rung walking test, the gait impairment was proportional to the severity of sciatic nerve damage, with the ABS group showing a significantly higher rate of errors than the control and saline groups. Immunohistochemistry demonstrated extensive degeneration and deformation in the axons and myelin sheath of the sciatic nerve in the ABS group. The results provide compelling evidence for the neurotoxicity of ABS.

Inhibition of microRNA-19a-3p alleviates the neuropathic pain (NP) in rats after chronic constriction injury (CCI) via targeting KLF7

BACKGROUND/PURPOSE

Neuropathic pain(NP) is derived from the dysfunctions of nerve system. The current research is to explore the impact and mechanism of miR-19a-3p in neuropathic pain in rats.

METHODS

The NP was induced through the chronic constriction injury (CCI) surgery in rats. The pro-inflammatory factors (IL-1β, IL-6, TNF-α) in spinal cord tissues from rats were measured using Elisa kits. Moreover, the different levels of thermal hyperalgesia and mechanical allodynia in rats were examined through paw withdrawal latency (PWL) and paw withdrawal threshold (PWT). To investigate into the role of miR-19a-3p and KLF7 in NP of rats, the knockdown of miR-19a-3p alone or along with KLF7 downregulation in rats were achieved through lentivirus injection. The miR-19a-3p and KLF7 expression in spinal cord of rats on Day 3,7,14 after CCI were detected using RT-qPCR. The protein expression of KLF7 were measured by Western blot. Bioinformatics and luciferase assays were used for the prediction and verification of bindings between KLF7 and miR-19a-3p.

RESULTS

CCI surgery caused neuropathic pain in rats with the levels of inflammatory cytokines increased and PWL and PWT decreased. Moreover, miR-19a-3p expression was increased while the protein and mRNA levels were decreased in spinal cord tissues in rats after CCI surgery. In rat microglial cells, miR-19a-3p downregulation could promote the KLF7 in both mRNA and protein expression. In spinal cord tissues of rats, the inhibition of miR-19a-3p enhanced the KLF7 expression. Furthermore, miR-19a-3p downregulation suppressed the IL-1β, IL-6 and TNF-α concentrations, and could decrease the NP but inhibition of KLF7 could partially reverse this in CCI rats.

CONCLUSION

miR-19a-3p inhibition may alleviate NP via KLF7 in CCI rats.

The use of viral vectors to promote repair after spinal cord injury

Spinal cord injury (SCI) is a devastating event that can permanently disrupt multiple modalities. Unfortunately, the combination of the inhibitory environment at a central nervous system (CNS) injury site and the diminished intrinsic capacity of adult axons for growth results in the failure for robust axonal regeneration, limiting the ability for repair. Delivering genetic material that can either positively or negatively modulate gene expression has the potential to counter the obstacles that hinder axon growth within the spinal cord after injury. A popular gene therapy method is to deliver the genetic material using viral vectors. There are considerations when deciding on a viral vector approach for a particular application, including the type of vector, as well as serotypes, and promoters. In this review, we will discuss some of the aspects to consider when utilizing a viral vector approach to as a therapy for SCI. Additionally, we will discuss some recent applications of gene therapy to target extrinsic and/or intrinsic barriers to promote axon regeneration after SCI in preclinical models. While still in early stages, this approach has potential to treat those living with SCI.

Nanochannel-Based Poration Drives Benign and Effective Nonviral Gene Delivery to Peripheral Nerve Tissue

While gene and cell therapies have emerged as promising treatment strategies for various neurological conditions, heavy reliance on viral vectors can hamper widespread clinical implementation. Here, the use of tissue nanotransfection as a platform nanotechnology to drive nonviral gene delivery to nerve tissue via nanochannels, in an effective, controlled, and benign manner is explored. TNT facilitates plasmid DNA delivery to the sciatic nerve of mice in a voltage-dependent manner. Compared to standard bulk electroporation (BEP), impairment in toe-spread and pinprick response is not caused by TNT, and has limited to no impact on electrophysiological parameters. BEP, however, induces significant nerve damage and increases macrophage immunoreactivity. TNT is subsequently used to deliver vasculogenic cell therapies to crushed nerves via delivery of reprogramming factor genes Etv2, Foxc2, and Fli1 (EFF). The results indicate the TNT-based delivery of EFF in a sciatic nerve crush model leads to increased vascularity, reduced macrophage infiltration, and improved recovery in electrophysiological parameters compared to crushed nerves that are TNT-treated with sham/empty plasmids. Altogether, the results indicate that TNT can be a powerful platform nanotechnology for localized nonviral gene delivery to nerve tissue, in vivo, and the deployment of reprogramming-based cell therapies for nerve repair/regeneration.

Using RNA-Seq to Explore the Repair Mechanism of the Three Methods and Three-Acupoint Technique on DRGs in Sciatic Nerve Injured Rats

Objective

To study the effects of the three methods and three-acupoint technique on DRG gene expression in SNI model rats and to elucidate the molecular mechanism of the three methods and three-acupoint technique on promoting recovery in peripheral nerve injury.

Methods

27 male SD rats were randomly divided into three groups: a Sham group, the SNI group, and the Tuina group. The Tuina group was treated with a tuina manipulation simulator to simulate massage on points, controlling for both quality and quantity. Point-pressing, plucking, and kneading methods were administered quantitatively at Yinmen (BL37), Chengshan (BL57), and Yanglingquan (GB34) points on the affected side once a day, beginning 7 days after modeling. Intervention was applied once a day for 10 days, then 1 day of rest, followed by 10 more days of intervention, totally equaling 20 times of intervention. The effect of the three methods and three-point technique on the recovery of injured rats was evaluated using behavior analysis. RNA sequencing (RNA-Seq) analysis of differentially expressed genes in DRGs of the three groups of rats was also performed. GO and KEGG enrichment was analyzed and verified using real-time PCR.

Results

RNA-Seq combined with database information showed that the number of differentially expressed genes in DRG was the largest in the Tuina group compared with the SNI group, totaling 226. GO function is enriched in the positive regulation of cell processes, ion binding, protein binding, neuron, response to pressure, response to metal ions, neuron projection, and other biological processes. GO function is also enriched in the Wnt, IL-17, and MAPK signaling pathways in the KEGG database. PCR results were consistent with those of RNA sequencing, suggesting that the results of transcriptome sequencing were reliable.

Conclusion

The three methods and three-acupoint technique can promote the recovery of SNI model rats by altering the gene sequence in DRGs.

Inhibition of Gamma-Secretase Promotes Axon Regeneration After a Complete Spinal Cord Injury

In a recent study, we showed that GABA and baclofen (a GABAB receptor agonist) inhibit caspase activation and promote axon regeneration in descending neurons of the sea lamprey brainstem after a complete spinal cord injury (Romaus-Sanjurjo et al., 2018a). Now, we repeated these treatments and performed 2 independent Illumina RNA-Sequencing studies in the brainstems of control and GABA or baclofen treated animals. GABA treated larval sea lampreys with their controls were analyzed 29 days after a complete spinal cord injury and baclofen treated larvae with their controls 9 days after the injury. One of the most significantly downregulated genes after both treatments was a HES gene (HESB). HES proteins are transcription factors that are key mediators of the Notch signaling pathway and gamma-secretase activity is crucial for the activation of this pathway. So, based on the RNA-Seq results we subsequently treated spinal cord injured larval sea lampreys with a novel gamma-secretase inhibitor (PF-3804014). This treatment also reduced the expression of HESB in the brainstem and significantly enhanced the regeneration of individually identifiable descending neurons after a complete spinal cord injury. Our results show that gamma-secretase could be a novel target to promote axon regeneration after nervous system injuries.

High Expression of Krüppel-like Factor 7 Indicates Unfavorable Clinical Outcomes in Patients with Lung Adenocarcinoma

BACKGROUND

Krüppel-like factor 7 (KLF7), which belongs to the KLF family of zinc finger transcription factors, plays a critical role in regulating gene expression. It was reported that KLF7 overexpression was closely related to the progression of gastric cancer. However, the role of KLF7 in lung adenocarcinoma (LAC) has not been elucidated. The aim of our study is to investigate the expression pattern of KLF7 and explore whether the KLF7 expression is correlated with unfavorable clinical outcome of patients with LAC.

MATERIALS AND METHODS

The protein and mRNA levels of KLF7 were examined in LAC tissues by using immunohistochemistry staining and quantitative reverse transcription polymerase chain reaction, respectively. The prognostic role of KLF7 in patients with LAC was assessed using univariate and multivariate analyses. Clinical outcomes were evaluated by Kaplan-Meier analysis and logrank test. The effects of KLF7 on lung cancer cells were investigated through cellular experiments.

RESULTS

KLF7 expression was elevated in LAC tissues compared with adjacent normal tissues. High protein level of KLF7 was correlated with larger tumor size, positive lymph node metastasis, and advanced TNM stage. Moreover, patients with LAC with higher expression level of KLF7 had poorer overall survival, and KLF7 was identified as an unfavorable independent prognosis factor. Knockdown of KLF7 can suppress the proliferation and invasion abilities of cancer cells.

CONCLUSIONS

Our studies revealed that high KLF7 expression level was significantly associated with the poorer clinical outcomes of patients with LAC, indicating the potential role of KLF7 as a novel prognostic biomarker and therapeutic target.

The Combination of Adipose-derived Schwann-like Cells and Acellular Nerve Allografts Promotes Sciatic Nerve Regeneration and Repair through the JAK2/STAT3 Signaling Pathway in Rats

Schwann cells (SCs) combined with acellular nerve allografts (ANAs) effectively promote the regeneration and repair of peripheral nerves, but the exact mechanism has not been fully elucidated. However, the disadvantages of SCs include their limited source and slow rate of expansion in vitro. Previous studies have found that adipose-derived stem cells have the ability to differentiate into Schwann-like cells. Therefore, we speculated that Schwann-like cells combined with ANAs could profoundly facilitate nerve regeneration and repair. The aim of the present study was to investigate the cellular and molecular mechanisms of regeneration and repair. In this study, tissue-engineered nerves were first constructed by adipose-derived Schwann-like cells and ANAs to bridge missing sciatic nerves. Then, the rats were randomly divided into five groups (n = 12 per group): a Control group; a Model group; an ADSC group; an SC-L group; and a DMEM group. Twelve weeks postsurgery, behavioral function tests and molecular biological techniques were used to evaluate the function of regenerated nerves and the relevant molecular mechanisms after sciatic nerve injury (SNI). The results showed that adipose-derived Schwann-like cells combined with ANAs markedly promoted sciatic nerve regeneration and repair. These findings also demonstrated that the expression of neurotrophic factors (NFs) was increased, and the expression of Janus activated kinase2 (JAK2)/P-JAK2, signal transducer and activator of transcription-3 (STAT3)/P-STAT3 was decreased in the spinal cord after SNI. Therefore, these results suggested that highly expressed NFs in the spinal cord could promote nerve regeneration and repair by inhibiting activation of the JAK2/STAT3 signaling pathway.

KLF7 overexpression in bone marrow stromal stem cells graft transplantation promotes sciatic nerve regeneration

OBJECTIVE

Our previous study demonstrated that the transcription factor, Krüppel-like Factor 7 (KLF7), stimulates axon regeneration following peripheral nerve injury. In the present study, we used a gene therapy approach to overexpress KLF7 in bone marrow-derived stem/stromal cells (BMSCs) as support cells, combined with acellular nerve allografts (ANAs) and determined the potential therapeutic efficacy of a KLF7-transfected BMSC nerve graft transplantation in a rodent model for sciatic nerve injury and repair.

APPROACH

We efficiently transfected BMSCs with adeno-associated virus (AAV)-KLF7, which were then seeded in ANAs for bridging sciatic nerve defects.

MAIN RESULTS

KLF7 overexpression promotes proliferation, survival, and Schwann-like cell differentiation of BMSCs in vitro. In vivo, KLF7 overexpression promotes transplanted BMSCs survival and myelinated fiber regeneration in regenerating ANAs; however, KLF7 did not improve Schwann-like cell differentiation of BMSCs within in the nerve grafts. KLF7-BMSCs significantly upregulated expression and secretion of neurotrophic factors by BMSCs, including nerve growth factor, ciliary neurotrophic factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor in regenerating ANA. KLF7-BMSCs also improved motor axon regeneration, and subsequent neuromuscular innervation and prevention of muscle atrophy. These benefits were associated with increased motor functional recovery of regenerating ANAs.

SIGNIFICANCE

Our findings suggest that KLF7-BMSCs promoted peripheral nerve axon regeneration and myelination, and ultimately, motor functional recovery. The mechanism of KLF7 action may be related to its ability to enhance transplanted BMSCs survival and secrete neurotrophic factors rather than Schwann-like cell differentiation. This study provides novel foundational data connecting the benefits of KLF7 in neural injury and repair to BMSC biology and function, and demonstrates a potential combination approach for the treatment of injured peripheral nerve via nerve graft transplant.

Noncellular Modification of Acellular Nerve Allografts for Peripheral Nerve Reconstruction: A Systematic Critical Review of the Animal Literature

BACKGROUND

Acellular nerve allografts (ANAs) have been established as promising alternatives to autologous nerve grafts, which represent the reference standard. Our research group recently performed a systematic review of reported cell-based-enriching methods for recellularization of ANAs. Recellularization results in consistent improvement of peripheral neuroregeneration compared with plain ANAs. We systematically reviewed the effects on nerve regeneration when ANA enrichment was obtained through biological, chemical, and physical modification instead of cells.

METHODS

The PubMed, ScienceDirect, Medline, and Scopus databases were searched for reports of noncellular modification of ANAs, reported from January 2007 to December 2017. The inclusion criteria were English language, noncellular enrichment of ANAs in peripheral nerve regeneration, an in vivo study design, and postgrafting neuroregenerative outcomes assessment. The exclusion criteria were the central nervous system as the site of ANA application, nerve conduits, xenografts, case series, case reports, and reviews.

RESULTS

Only animal studies were found to be eligible. We included 16 studies, which were analyzed regarding the animal model, decellularization method, graft-enriching mode, and neuroregenerative tests performed.

CONCLUSIONS

Noncellular-based stimulation of ANAs demonstrated positive effects on recovery of nerve function compared with nerve grafting compared with plain ANAs. The neuroregenerative effect of autografting still appeared superior to ANAs, even with noncellular enrichment of ANAs. However, we found that in a few studies, modified ANAs closely approached or even outperformed autografts. Future research should include more preclinical investigations of this promising tool and clinical translation to increase the level of evidence available in the challenging field of peripheral nerve reconstruction.

Inhibition of KLF7-Targeting MicroRNA 146b Promotes Sciatic Nerve Regeneration

A previous study has indicated that Krüppel-like factor 7 (KLF7), a transcription factor that stimulates Schwann cell (SC) proliferation and axonal regeneration after peripheral nerve injury, is a promising therapeutic transcription factor in nerve injury. We aimed to identify whether inhibition of microRNA-146b (miR-146b) affected SC proliferation, migration, and myelinated axon regeneration following sciatic nerve injury by regulating its direct target KLF7. SCs were transfected with miRNA lentivirus, miRNA inhibitor lentivirus, or KLF7 siRNA lentivirus in vitro. The expression of miR146b and KLF7, as well as SC proliferation and migration, were subsequently evaluated. In vivo, an acellular nerve allograft (ANA) followed by injection of GFP control vector or a lentiviral vector encoding an miR-146b inhibitor was used to assess the repair potential in a model of sciatic nerve gap. miR-146b directly targeted KLF7 by binding to the 3'-UTR, suppressing KLF7. Up-regulation of miR-146b and KLF7 knockdown significantly reduced the proliferation and migration of SCs, whereas silencing miR-146b resulted in increased proliferation and migration. KLF7 protein was localized in SCs in which miR-146b was expressed in vivo. Similarly, 4 weeks after the ANA, anti-miR-146b increased KLF7 and its target gene nerve growth factor cascade, promoting axonal outgrowth. Closer analysis revealed improved nerve conduction and sciatic function index score, and enhanced expression of neurofilaments, P0 (anti-peripheral myelin), and myelinated axon regeneration. Our findings provide new insight into the regulation of KLF7 by miR-146b during peripheral nerve regeneration and suggest a potential therapeutic strategy for peripheral nerve injury.

Baseline effects of lysophosphatidylcholine and nerve growth factor in a rat model of sciatic nerve regeneration after crush injury

Schwann cells play a major role in helping heal injured nerves. They help clear debris, produce neurotrophins, upregulate neurotrophin receptors, and form bands of Büngner to guide the healing nerve. But nerves do not always produce enough neurotrophins and neurotrophin receptors to repair themselves. Nerve growth factor (NGF) is an important neurotrophin for promoting nerve healing and lysophosphatidylcholine (LPC) has been shown to stimulate NGF receptors (NGFR). This study tested the administration of a single intraneural injection of LPC (1 mg/mL for single LPC injection and 10 mg/mL for multiple LPC injections) at day 0 and one (day 7), two (days 5 and 7), or three (days 5, 7, and 9) injections of NGF (160 ng/mL for single injections and 80 ng/mL for multiple injections) to determine baseline effects on crushed sciatic nerves in rats. The rats were randomly divided into four groups: control, crush, crush-NGF, and crush-LPC-NGF. The healing of the nerves was measured weekly by monitoring gait; electrophysiological parameters: compound muscle action potential (CMAP) amplitudes; and morphological parameters: total fascicle areas, myelinated fiber counts, fiber densities, fiber packing, and mean g-ratio values at weeks 3 and 6. The crush, crush-NGF, and crush-LPC-NGF groups statistically differed from the control group for all six weeks for the electrophysiological parameters but only differed from the control group at week 3 for the morphological parameters. The crush, crush-NGF, and crush-LPC-NGF groups did not differ from each other over the course of the study. Single injections of LPC and NGF one week apart or multiple treatments of NGF at 5, 7 and 9 days post-injury did not alter the healing rate of the sciatic nerves during weeks 1-6 of the study. These findings are important to define the baseline effects of NGF and LPC injections, as part of a larger effort to determine the minimal dose regimen of NGF to regenerate peripheral nerves.

AAV-KLF7 Promotes Descending Propriospinal Neuron Axonal Plasticity after Spinal Cord Injury

DPSN axons mediate and maintain a variety of normal spinal functions. Unsurprisingly, DPSN tracts have been shown to mediate functional recovery following SCI. KLF7 could contribute to CST axon plasticity after spinal cord injury. In the present study, we assessed whether KLF7 could effectively promote DPSN axon regeneration and synapse formation following SCI. An AAV-KLF7 construct was used to overexpress KLF7. In vitro, KLF7 and target proteins were successfully elevated and axonal outgrowth was enhanced. In vivo, young adult C57BL/6 mice received a T10 contusion followed by an AAV-KLF7 injection at the T7–9 levels above the lesion. Five weeks later, overexpression of KLF7 was expressed in DPSN. KLF7 and KLF7 target genes (NGF, TrkA, GAP43, and P0) were detectably increased in the injured spinal cord. Myelin sparring at the lesion site, DPSN axonal regeneration and synapse formation, muscle weight, motor endplate morphology, and functional parameters were all additionally improved by KLF7 treatment. Our findings suggest that KLF7 promotes DPSN axonal plasticity and the formation of synapses with motor neurons at the caudal spinal cord, leading to improved functional recovery and further supporting the potential of AAV-KLF7 as a therapeutic agent for spinal cord injury.