Recent advances in the application of MXenes for neural tissue engineering and regeneration

Transition metal carbides and nitrides(MXenes)are crystal nanomaterials with a number of surface functional groups such as fluorine,hydroxyl,and oxygen,which can be used as carriers for proteins and drugs.MXenes have excellent biocompatibility,electrical conductivity,surface hydrophilicity,mechanical properties and easy surface modification.However,at present,the stability of most MXenes needs to be improved,and more synthesis methods need to be explored.MXenes are good substrates for nerve cell regeneration and nerve reconstruction,which have broad application prospects in the repair of nervous system injury.Regarding the application of MXenes in neuroscience,mainly at the cellular level,the long-term in vivo biosafety and effects also need to be further explored.This review focuses on the progress of using MXenes in nerve regeneration over the last few years;discussing preparation of MXenes and their biocompatibility with different cells as well as the regulation by MXenes of nerve cell regeneration in two-dimensional and three-dimensional environments in vitro.MXenes have great potential in regulating the proliferation,differentiation,and maturation of nerve cells and in promoting regeneration and recovery after nerve injury.In addition,this review also presents the main challenges during optimization processes,such as the preparation of stable MXenes and long-term in vivo biosafety,and further discusses future directions in neural tissue engineering.

Development of Chinese herbal medicine for sensorineural hearing loss

According to the World Health Organization’s world report on hearing,nearly 2.5 billion people worldwide will suffer from hearing loss by 2050,which may contribute to a severe impact on individual life quality and national economies.Sensorineural hearing loss(SNHL)occurs commonly as a result of noise exposure,aging,and ototoxic drugs,and is pathologically characterized by the impairment of mechanosensory hair cells of the inner ear,which is mainly triggered by reactive oxygen species accumulation,inflammation,and mitochondrial dysfunction.Though recent advances have been made in understanding the ability of cochlear repair and regeneration,there are still no effective therapeutic drugs for SNHL.Chinese herbal medicine which is widely distributed and easily accessible in China has demonstrated a unique curative effect against SNHL with higher safety and lower cost compared with Western medicine.Herein we present trends in research for Chinese herbal medicine for the treatment of SNHL,and elucidate their molecular mechanisms of action,to pave the way for further research and development of novel effective drugs in this field.

Conductive PS inverse opals for regulating proliferation and differentiation of neural stem cells

The development of neural tissue engineering has brought new hope to the treatment of spinal cord injury(SCI).Up to date,various scaffolds have been developed to induce the oriented growth and arrangement of nerves to facilitate the repair after injury.In this work,a conductive and anisotropic inverse opal substrate was presented by modifying polystyrene(PS)inverse opal films with carbon nanotubes and then stretching them to varying degrees.The film had good biocompatibility,and neural stem cells(NSCs)grown on the film displayed good orientation along the stretching direction.In addition,benefiting from the conductivity and anisotropy of the film,NSCs differentiated into neurons significantly.These results suggest that the conductive and anisotropic PS inverse opal substrates possess value in nerve tissue engineering regeneration.

MonkeyTrail:A scalable video-based method for tracking macaque movement trajectory in daily living cages

Behavioral analysis of macaques provides important experimental evidence in the field of neuroscience.In recent years,video-based automatic animal behavior analysis has received widespread attention.However,methods capable of extracting and analyzing daily movement trajectories of macaques in their daily living cages remain underdeveloped,with previous approaches usually requiring specific environments to reduce interference from occlusion or environmental change.Here,we introduce a novel method,called MonkeyTrail,which satisfies the above requirements by frequently generating virtual empty backgrounds and using background subtraction to accurately obtain the foreground of moving animals.The empty background is generated by combining the frame difference method(FDM)and deep learning-based model(YOLOv5).The entire setup can be operated with low-cost hardware and can be applied to the daily living environments of individually caged macaques.To test MonkeyTrail performance,we labeled a dataset containing>8000 video frames with the bounding boxes of macaques under various conditions as ground-truth.Results showed that the tracking accuracy and stability of MonkeyTrail exceeded that of two deep learningbased methods(YOLOv5 and Single-Shot MultiBox Detector),traditional frame difference method,and na?ve background subtraction method.Using MonkeyTrail to analyze long-term surveillance video recordings,we successfully assessed changes in animal behavior in terms of movement amount and spatial preference.Thus,these findings demonstrate that MonkeyTrail enables low-cost,large-scale daily behavioral analysis of macaques.

Brain insulin resistance and Parkinson’s disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease. Its most prominent pathological features are the loss of dopaminergic neurons in the substantia nigra pars compacta and the deposition of intraneuronal inclusions named Lewy bodies. Currently, the pathophysiological mechanisms of PD are not fully understood. Growing evidence suggests that insulin resistance, diabetes and PD share similar pathological processes. This raises the possibility that defective insulin signaling pathways contribute to the occurrence and development of PD. In this article, we firstly reviewed the evidence of insulin resistance from epidemiology, PD patients and animal models. We also explained the insulin signal pathways in central nervous system. We then showed the evidence that insulin resistance participates in the pathogenesis of PD via protein aggregation, mitochondrial dysfunction, neural inflammation and cognitive impairment. Finally, we introduced four categories of drugs that facilitate insulin signaling and their effects on neurodegeneration in PD.

Recent advances in the molecular mechanism of Janus kinase activation

The JAK (Janus kinase) family members play a role in the transmission of signals from extracellular stimuli across the plasma membrane via the cytoplasm to the nucleus in eukaryotes. The JAK family is comprised of JAK1, JAK2, JAK3 and TYK2 (tyrosine kinase 2), and the complexities underlying their activation and regulation are still being investigated. Here, we review the recent advances of their functions and the underlying mechanism of activation. At the molecular level, recent studies have greatly advanced our knowledge of the structures and organization of the JAK proteins, as well as the mechanism of JAK activation, particularly the role of the pseudokinase domain as a suppressor of the adjacent tyrosine kinase domain’s catalytic activity. We also review recent advances in our understanding of the mechanisms of negative regulation exerted by phosphatase and SH2 (Src homology 2) domain-containing proteins. These recent studies highlight the diversity of regulatory mechanisms utilized by the JAK family to maintain signalling fidelity, and shed much light on the potential novel strategies for precise treatment of the associated diseases.

Noninvasive Tracking of Every Individual in Unmarked Mouse Groups Using Multi-Camera Fusion and Deep Learning

Accurate and efficient methods for identifying and tracking each animal in a group are needed to study complex behaviors and social interactions.Traditional tracking methods(e.g.,marking each animal with dye or surgically implanting microchips)can be invasive and may have an impact on the social behavior being measured.To overcome these shortcomings,video-based methods for tracking unmarked animals,such as fruit flies and zebrafish,have been developed.However,tracking individual mice in a group remains a challenging problem because of their flexible body and complicated interaction patterns.In this study,we report the development of a multi-object tracker for mice that uses the Faster region-based convolutional neural network(R-CNN)deep learning algorithm with geometric transformations in combination with multi-camera/multi-image fusion technology.The system successfully tracked every individual in groups of unmarked mice and was applied to investigate chasing behavior.The proposed system constitutes a step forward in the noninvasive tracking of individual mice engaged in social behavior.

Dock4 is required for the maintenance of cochlear hair cells and hearing function

Auditory hair cells(HCs)are the mechanosensory receptors of the cochlea,and HC loss or malfunction can result from genetic defects.Dock4,a member of the Dock180-related protein superfamily,is a guanine nucleotide exchange factor for Rac1,and previous reports have shown that Dock4 mutations are associated with autism spectrum disorder,myelodysplastic syndromes,and tumorigenesis.Here,we found that Dock4 is highly expressed in the cochlear HCs of mice.However,the role of Dock4 in the inner ear has not yet been investigated.Taking advantage of the piggyBac transposon system,Dock4 knockdown(KD)mice were established to explore the role of Dock4 in the cochlea.Compared to wild-type controls,Dock4 KD mice showed significant hearing impairment from postnatal day 60.Dock4 KD mice showed hair bundle deficits and increased oxidative stress,which eventually led to HC apoptosis,late-onset HC loss,and progressive hearing loss.Furthermore,molecular mechanism studies showed that Rac1/β-catenin signaling was significantly downregulated in Dock4 KD cochleae and that this was the cause for the disorganized stereocilia and increased oxidative stress in HCs.Overall,our work demonstrates that the Dock4/Rac1/β-catenin signaling pathway plays a critical role in the maintenance of auditory HCs and hearing function.

Absence of Serpinb6a causes progressive hair cell apoptosis and hearing loss in mice

Hearing impairment constitutes a global public health problem with severe social,political,and economic consequences,and the World Health Organization estimates that about 466 million individuals globally have some degree of hearing loss.Genetic factors account for about half of all deafness cases.Currently,more than 100 genes are known to be involved in hearing loss,but the underlying molecular mechanisms behind these deafness genes have not been fully characterized.The main clinical treatment for deafness is hearing aids and cochlear implants,but their efficacy depends heavily on the quantity and quality of residual hair cells(HCs)and spiral ganglion neurons and has only limited auditory effects.

The overexpression of Rps14 in Lgr5+progenitor cells promotes hair cell regeneration in the postnatal mouse cochlea

Sensory hair cells(HCs)in the cochlea cannot regenerate spontaneously in adult mammals after being damaged by external or genetic factors.However,several genes and signaling pathways are reported to induce cochlear HC regeneration at the early neonatal stage.Rps14 encodes a ribosomal protein that is involved in the regulation of cell differentiation and proliferation in mammals.However,its roles in the cochlea have not been reported in vivo.Here,we specifically overexpressed Rps14 in Lgr5+progenitor cells in the newborn mouse cochlea and found that Rps14 conditional overexpression(cOE)mice had significantly increased the ectopic HCs,including inner and outer HCs.We further explored the source of these ectopic HCs and found no EdU+supporting cells observed in the Rps14 cOE mice.The lineage tracing results,on the other hand,revealed that Rps14 cOE mice had significantly more tdTomato+HCs in their cochleae than control mice.These results indicated that regenerated HCs by cOE of Rps14 are most likely derived from inducing the direct trans-differentiation of Lgr5+progenitor cells into HCs.Moreover,real-time qPCR results suggested that the transcription factor genes Atoh1 and Gfi1,which are important in regulating HC differentiation,were upregulated in the cochlear basilar membrane of Rps14 cOE mice.In summary,this study provides in vivo evidence that,in the postnatal mouse cochlea,Rps14 is a potential gene that can promote the spontaneous trans-differentiation of Lgr5+progenitor cells into HCs.This gene may one day be exploited as a therapeutic target for treating hearing loss.

AAV-ie-K558R mediated cochlear gene therapy and hair cell regeneration

The cochlea consists of multiple types of cells,including hair cells,supporting cells and spiral ganglion neurons,and is responsible for converting mechanical forces into electric signals that enable hearing.Genetic and environmental factors can result in dysfunctions of cochlear and auditory systems.In recent years,gene therapy has emerged as a promising treatment in animal deafness models.One major challenge of the gene therapy for deafness is to effectively deliver genes to specific cells of cochleae.

Disruption of the autism-related gene Pak1 causes stereocilia disorganization,hair cell loss,and deafness in mice

Several clinical studies have reported that hearing loss is correlated with autism in children.However,little is known about the underlying mechanism between hearing loss and autism.p21-activated kinases(PAKs)are a family of serine/threonine kinases that can be activated by multiple signaling molecules,particularly the Rho family of small GTPases.Previous studies have shown that Pak1 mutations are associated with autism.In the present study,we take advantage of Pak1 knockout(Pak1a/a)mice to investigate the role of PAK1 in hearing function.We find that PAK1 is highly expressed in the postnatal mouse cochlea and that PAK1 deficiency leads to hair cell(HC)apoptosis and severe hearing loss.Further investigation indicates that PAK1 deficiency downregulates the phosphorylation of cofilin and ezrin-radixin-moesin and the expression of b II-spectrin,which further decreases the HC synapse density in the basal turn of cochlea and disorganized the HC stereocilia in all three turns of cochlea in Pak1à/àmice.Overall,our work demonstrates that the autism-related gene Pak1 plays a crucial role in hearing function.As the first candidate gene linking autism and hearing loss,Pak1 may serve as a potential target for the clinical diagnosis of autism-related hearing loss.

Virus-Mediated Overexpression of ETS-1 in the Ventral Hippocampus Counteracts Depression-Like Behaviors in Rats

ETS-1 is a transcription factor that is a member of the E26 transformation-specific(ETS) family. Galanin receptor 2(Gal R2), a subtype of receptors of the neuropeptide galanin, has been shown to have an antidepressant-like effect after activation in rodents. Our previous study has shown that overexpression of ETS-1 increases the expression of Gal R2 in PC12 phaeochromocytoma cells. However, whether ETS-1 has an antidepressant-like effect is still unclear. In this study, we found that chronic mild stress(CMS) decreased the expression of both ETS-1 and Gal R2 in the ventral hippocampus of rats. Meanwhile,we demonstrated that overexpression of ETS-1 increased the expression of Gal R2 in primary hippocampal neurons.Importantly, we showed that overexpression of ETS-1 in the ventral hippocampus counteracted the depression-like behaviors of CMS rats. Furthermore, we found that overexpression of ETS-1 increased the level of downstream phosphorylated extracellular signal-regulated protein kinases 1 and 2(p-ERK1/2) of Gal R2 in the ventral hippocampus of CMS rats. Taken together, our findings suggest that ETS-1 has an antidepressant-like effect in rats,which might be mediated by increasing the level of Gal R2 and its downstream p-ERK1/2 in the ventral hippocampus.

Bio-inspired intestinal scavenger from microfluidic electrospray for detoxifying lipopolysaccharide

Lipopolysaccharide(LPS)plays an important role in metabolic syndrome(MetS)and other gut-derived diseases,and detoxifying LPS is considered to be a fundamental approach to prevent and treat these diseases.Here,inspired by the feeding behaviour of scavenger,novel microfluidic microcapsules with alkaline phosphatase(ALP)encapsulation and the scavenger-like molecular sieve shell are presented for cleaning intestinal LPS.Benefiting from the precisely controlled of the pore size and microfluidic electrospray,the generated microcapsules were imparted with porous molecular-sieve shells and ALP encapsulated active cores.These microcapsules could continuously work as an intestinal scavenger after colonized in intestine.It has been demonstrated that the microcapsules could englobe LPS while inhibit the permeation of digestive enzyme,and this ability contributes to promising ALP’s activity,protecting cells at the presence of LPS and reducing inflammation.In addition,this scavenger inspired microcapsule could effectively decrease the LPS in organs,reduce inflammation and regulating fat metabolism in vivo.These features make the ALP encapsulated microcapsules an ideal candidate for treating MetS and other LPS related diseases.

Advance and Application of Single‑cell Transcriptomics in Auditory Research

Hearing loss and deafness,as a worldwide disability disease,have been troubling human beings.However,the auditory organ of the inner ear is highly heterogeneous and has a very limited number of cells,which are largely uncharacterized in depth.Recently,with the development and utilization of single-cell RNA sequencing(scRNA-seq),researchers have been able to unveil the complex and sophisticated biological mechanisms of various types of cells in the auditory organ at the single-cell level and address the challenges of cellular heterogeneity that are not resolved through by conventional bulk RNA sequencing(bulk RNAseq).Herein,we reviewed the application of scRNA-seq technology in auditory research,with the aim of providing a reference for the development of auditory organs,the pathogenesis of hearing loss,and regenerative therapy.Prospects about spatial transcriptomic scRNA-seq,single-cell based genome,and Live-seq technology will also be discussed.

Scaffolds with anisotropic structure for neural tissue engineering

Nervous system injuries remain a great challenge due to limited natural tissue regeneration capabilities.Neural tissue engineering has been regarded as a promising approach for repairing nerve defects,which utilizes external biomaterial scaffolds to allow cells to migrate to the injury site and repair the tissue.Particularly,scaffolds with anisotropic structures biomimicking the native extracellular matrix(ECM)can effectively guide neural orientation and reconnection.Here,the advancements of scaffolds with anisotropic structures in the field of neural tissue engineering are presented.The fabrication strategies of scaffolds with anisotropic structures and their effects in vitro and in vivo are highlighted.We also discuss the challenges and provide a perspective of this field.

Restoration of FMRP expression in adult V1 neurons rescues visual deficits in a mouse model of fragile X syndrome

Many people affected by fragile X syndrome(FXS)and autism spectrum disorders have sensory processing deficits,such as hypersensitivity to auditory,tactile,and visual stimuli.Like FXS in humans,loss of Fmr1 in rodents also cause sensory,behavioral,and cognitive deficits.However,the neural mechanisms underlying sensory impairment,especially vision impairment,remain unclear.It remains elusive whether the visual processing deficits originate from corrupted inputs,impaired perception in the primary sensory cortex,or altered integration in the higher cortex,and there is no effective treatment.In this study,we used a genetic knockout mouse model(Fmr1^(KO)),in vivo imaging,and behavioral measurements to show that the loss of Fmr1 impaired signal processing in the primary visual cortex(V1).Specifically,Fmr1^(KO) mice showed enhanced responses to low-intensity stimuli but normal responses to high-intensity stimuli.This abnormality was accompanied by enhancements in local network connectivity in V1 microcircuits and increased dendritic complexity of V1 neurons.These effects were ameliorated by the acute application of GABAA receptor activators,which enhanced the activity of inhibitory neurons,or by reintroducing Fmr1 gene expression in knockout V1 neurons in both juvenile and young-adult mice.Overall,V1 plays an important role in the visual abnormalities of Fmr1^(KO) mice and it could be possible to rescue the sensory disturbances in developed FXS and autism patients.

Corrigendum to“Bio-inspired intestinal scavenger from microfluidic electrospray for detoxifying lipopolysaccharide”[Bioact.Mater.6(2020)1653-1662]

The fluorescent image of living cell staining in Fig.4A was wrongly used during the assembly of Fig.4.We tracked down the original data obtained in June 2020,and have replaced Fig.4A with the correct image as follow.

Regulation of autophagy:a promising therapeutic target for the treatment of hearing loss

Autophagy,a ubiquitous cellular biological behavior that features a lysosome-dependent degradation pathway,is an important mechanism for cellular self-protection in eukaryotes.Autophagy plays essential roles in cell survival,renewal,material reuse and the maintenance of homeostasis.This paper reviews recent advances in understanding the physiological function of autophagy and its possible roles in auditory diseases.We focused our review on original publications on animal models,drug models,and molecular mechanisms of hearing impairment involved in the dysregulation of autophagy.As research on the mechanisms of autophagy has deepened,it has become obvious that autophagy plays essential roles not only in cell survival,but the occurrence and development of a variety of auditory-related disorder,including aminoglycoside-induced hearing loss,age-related hearing loss,and noise-induced hearing loss.While clinical treatment of such conditions via regulation of the development of autophagy is a novel idea,more time is needed to fully elucidate the specific regulatory pathways and modes of autophagy in auditory diseases.The continued study of the mechanisms and regulation of autophagy in auditory diseases will be of great significance for the future treatment and prevention of these conditions.

Rassf2 overexpression mediated by AAV promotes the supporting cell-to-hair cell transformation in the cochlea

Sensory hair cells are responsible for detecting and transmitting sound in the inner ear,and damage to HCs leads to hearing loss.HCs do not regenerate spontaneously in adult mammals,which makes the hearing loss permanent.However,hair cells and supporting cells have the same precursors in the inner ear,and in newborn mice,the adjacent SCs can be activated by gene manipulation to differentiate into newly regenerated hair cells.Here,we demonstrate the role of the Ras association domain family member 2(Rassf2)in supporting cell to hair cell trans-differentiation in the inner ear.Using the AAV vector(AAV-ie)to upregulate Rassf2 expression promoted supporting cell division and hair cell production in cultured cochlear organoids.Also,AAV-Rassf2 enhanced the regenerative ability of Lgr5+SCs in the postnatal cochlea without impairing hearing,and this might due to the modulation of the Wnt,Hedgehog and Notch signaling pathways.Furthermore,AAV-Rassf2 enhances cochlear supporting cell division and hair cell production in the neomycin injury model.In summary,our results suggest that Rassf2 is a key component in HC regenerative repair,and gene modulation mediated by adeno-associated virus may be a promising gene therapy for hearing repair.