Translocation of telomerase reverse transcriptase coincided with ATP release in postnatal cochlear supporting cells

The spontaneous bursts of electrical activity in the developing auditory system are derived from the periodic release of adenosine triphosphate(ATP)by supporting cells in the Kölliker’s organ.However,the mechanisms responsible for initiating spontaneous ATP release have not been determined.Our previous study revealed that telomerase reverse transcriptase(TERT)is expressed in the basilar membrane during the first postnatal week.Its role in cochlear development remains unclear.In this study,we investigated the expression and role of TERT in postnatal cochlea supporting cells.Our results revealed that in postnatal cochlear Kölliker’s organ supporting cells,TERT shifts from the nucleus into the cytoplasm over time.We found that the TERT translocation tendency in postnatal cochlear supporting cells in vitro coincided with that observed in vivo.Further analysis showed that TERT in the cytoplasm was mainly located in mitochondria in the absence of oxidative stress or apoptosis,suggesting that TERT in mitochondria plays roles other than antioxidant or anti-apoptotic functions.We observed increased ATP synthesis,release and activation of purine signaling systems in supporting cells during the first 10 postnatal days.The phenomenon that TERT translocation coincided with changes in ATP synthesis,release and activation of the purine signaling system in postnatal cochlear supporting cells suggested that TERT may be involved in regulating ATP release and activation of the purine signaling system.Our study provides a new research direction for exploring the spontaneous electrical activity of the cochlea during the early postnatal period.

Supporting Cells-a New Area in Cochlear Physiology Study

For many years, studies about the cochlea have been mainly focused on sensory cells, i.e. the inner hair cell(IHC) and outer hair cell (OHC), and the neuron system. Supporting cells, such as Hensen’s cells and Deiters’ cells are less studied. Their physiological functions and other characteristics are not well documented. Nowadays,supporting cells are a new world attracting to scientists' interests. The scope of this review is to detail the biological properties of the supporting cells, mainly Hensen’s cells and Deiters’ cells in the cochlea. Studies on this subject will be helpful in understanding physiology of the cochlea, and hopefully provide new approaches in treating diseases of inner ear.

Growth Factors and Supporting Cells of Nerve Conduits for Peripheral Nerve Regeneration

Peripheral nerve injury is a common disease that endangers human health.There is a variety of methods to repair peripheral nerve injury,the current"gold standard"approach is autograft,however it still faces many disadvantages.A new choice is the use of artificial nerve conduits,which are tubular structures and are designed to bridge nerve gaps.In order to bridge longer nerve gaps and gain ideal nerve regeneration effects,multiple technologies have been developed to the design of nerve conduits,such as selecting sutible materials,supplementing growth factors,transplanting supporting cells and so on.This review mainly introduce current progess in growth factors supplementation and supporting cells transplantation technology of nerve conduits.

MECOM promotes supporting cell proliferation and differentiation in cochlea

Permanent damage to hair cells(HCs)is the leading cause of sensory deafness.Supporting cells(SCs)are essential in the restoration of hearing in mammals because they can proliferate and differentiate to HCs.MDS1 and EVI1 complex locus(MECOM)is vital in early development and cell differentiation and regulates the TGF-βsignaling pathway to adapt to pathophysiological events,such as hematopoietic proliferation,differentiation and cells death.In addition,MECOM plays an essential role in neurogenesis and craniofacial development.However,the role of MECOM in the development of cochlea and its way to regulate related signaling are not fully understood.To address this problem,this study examined the expression of MECOM during the development of cochlea and observed a significant increase of MECOM at the key point of auditory epithelial morphogenesis,indicating that MECOM may have a vital function in the formation of cochlea and regeneration of HCs.Meanwhile,we tried to explore the possible effect and potential mechanism of MECOM in SC proliferation and HC regeneration.Findings from this study indicate that overexpression of MECOM markedly increases the proliferation of SCs in the inner ear,and the expression of Smad3 and Cdkn2b related to TGF signaling is significantly down-regulated,corresponding to the overexpression of MECOM.Collectively,these data may provide an explanation of the vital function of MECOM in SC proliferation and trans-differentiation into HCs,as well as its regulation.The interaction between MECOM,Wnt,Notch and the TGF-βsignaling may provide a feasible approach to induce the regeneration of HCs.

Notch pathway inhibitor DAPT enhances Atoh1 activity to generate new hair cells in situ in rat cochleae

Atoh1 overexpression in cochlear epithelium induces new hair cell formation. Use of adenovirus-mediated Atoh1 overexpression has mainly focused on the rat lesser epithelial ridge and induces ectopic hair cell regeneration. The sensory region of rat cochlea is difficult to transfect, thus new hair cells are rarely produced in situ in rat cochlear explants. After culturing rat cochleae in medium containing 10% fetal bovine serum, adenovirus successfully infected the sensory region as the width of the supporting cell area was significantly increased. Adenovirus encoding Atoh1 infected the sensory region and induced hair cell formation in situ. Combined application of the Notch inhibitor DAPT and Atoh1 increased the Atoh1 expression level and decreased hes1 and hes5 levels, further promoting hair cell generation. Our results demonstrate that DAPT enhances Atoh1 activity to promote hair cell regeneration in rat cochlear sensory epithelium in vitro.

Bridging long gap peripheral nerve injury using skeletal muscle-derived multipotent stem cells

Long gap peripheral nerve injuries usually reulting in life-changing problems for patients. Skeletal muscle derived-multipotent stem cells （Sk-MSCs） can differentiate into Schwann and perineurial/endoneurial cells, vascular relating pericytes, and endothelial and smooth muscle cells in the damaged peripheral nerve niche. Application of the Sk-MSCs in the bridging conduit for repairing long nerve gap injury resulted favorable axonal regeneration, which showing superior effects than gold standard therapy--healthy nerve autograft. This means that it does not need to sacrifice of healthy nerves or loss of related functions for repairing peripheral nerve injury.

BMP-IHH-mediated interplay between mesenchymal stem cells and osteoclasts supports calvarial bone homeostasis and repair

Calvarial bones are connected by fibrous sutures. These sutures provide a niche environment that includes mesenchymal stem cells(MSCs), osteoblasts, and osteoclasts, which help maintain calvarial bone homeostasis and repair. Abnormal function of osteogenic cells or diminished MSCs within the cranial suture can lead to skull defects, such as craniosynostosis. Despite the important function of each of these cell types within the cranial suture, we have limited knowledge about the role that crosstalk between them may play in regulating calvarial bone homeostasis and injury repair. Here we show that suture MSCs give rise to osteoprogenitors that show active bone morphogenetic protein(BMP) signalling and depend on BMP-mediated Indian hedgehog(IHH) signalling to balance osteogenesis and osteoclastogenesis activity. IHH signalling and receptor activator of nuclear factor kappa-Β ligand(RANKL) may function synergistically to promote the differentiation and resorption activity of osteoclasts. Loss of Bmpr1a in MSCs leads to downregulation of hedgehog(Hh) signalling and diminished cranial sutures. Significantly, activation of Hh signalling partially restores suture morphology in Bmpr1a mutant mice, suggesting the functional importance of BMP-mediated Hh signalling in regulating suture tissue homeostasis. Furthermore, there is an increased number of CD200+ cells in Bmpr1a mutant mice, which may also contribute to the inhibited osteoclast activity in the sutures of mutant mice. Finally, suture MSCs require BMPmediated Hh signalling during the repair of calvarial bone defects after injury. Collectively, our studies reveal the molecular and cellular mechanisms governing cell–cell interactions within the cranial suture that regulate calvarial bone homeostasis and repair.

Expression change of stem cell-derived neural stem/progenitor cell sup-porting factor gene in injured spinal cord of rats

Objective To explore the expression change of stem cell-derived neural stem/progenitor cell supporting factor （SDNSF） gene in the injuried spinal cord tissues of rats, and the relation between the expressions of SDNSF and nestin. Methods The spinal cord contusion model of rat was established according to Allen＇s falling strike method. The expression of SDNSF was studied by RT-PCR and in situ hybridization （ISH）, and the expression of nestin was detected by immunochemistry. Results RT-PCR revealed that SDNSF mRNA was upregulated on day 4 after injury, peaked on day 8-12, and decreased to the sham operation level on day 16. ISH revealed that SDNSF mRNA was mainly expressed in the gray matter cells, probably neurons, of spinal cord. The immunohistochemistry showed that accompanied with SDNSF mRNA upregulation, the nestin-positive cells showed erupted roots, migrated peripherad and proliferation on the 8-day slice. However, the distribution pattern of these new cells was different from that of SDNSF-positive cells. Conclusion （1） SDNSF is expressed in the gray matter of spinal cord. The expression of SDNSF mRNA in the spinal cord varies with injured time. （2） The nestin-positive cells proliferate accompanied with spinal cord injury repair, but do not secrete SDNSF.

Cell proliferation during hair cell regeneration induced by Math1 in vestibular epithelia in vitro

Hair cell regeneration is the fundamental method of correcting hearing loss and balance disorders caused by hair cell damage or loss. How to promote hair cell regeneration is a hot focus in current research. In mammals, cochlear hair cells cannot be regenerated and few vestibular hair cells can be renewed through spontaneous regeneration. However, Math1 gene transfer allows a few inner ear cells to be transformed into hair cells in vitro or in vivo. Hair cells can be renewed through two possible means in birds： supporting cell differentiation and transdifferentiation with or without cell division. Hair cell regeneration is strongly associated with cell proliferation. Therefore, this study explored the relationship between Math1-induced vestibular hair cell regeneration and cell division in mammals. The mouse vestibule was isolated to harvest vestibular epithelial cells. Ad-Math1-enhanced green fluorescent protein （EGFP） was used to track cell division during hair cell transformation.5-Bromo-2′-deoxyuridine （BrdU） was added to track cell proliferation at various time points. Immunocytochemistry was utilized to determine cell differentiation and proliferation. Results demonstrated that when epithelial cells were in a higher proliferative stage, more of these cells differentiated into hair cells by Math1 gene transfer. However, in the low proliferation stage, no BrdU-positive cells were seen after Math1 gene transfer. Cell division always occurred before Math1 transfection but not during or after Math1 transfection, when cells were labeled with BrdU before and after Ad-Math1-EGFP transfection. These results confirm that vestibular epithelial cells with high proliferative potential can differentiate into new hair cells by Math1 gene transfer, but this process is independent of cell proliferation.

Extensive supporting cell proliferation and mitotic hair cell generation by in vivo genetic reprogramming in the neonatal mouse cochlea

Subject Code:H13With the support by the National Natural Science Foundation of China,the research team led by Prof.Li Huawei(李华伟)at the Otorhinolaryngology Department,Affiliated Eye and ENT hospital,State Key Laboratory of Medical Neurobiology of Fudan University,achieved the mitotic hair cell generation through agenetic reprogramming procedure,which was published in the Journal of Neuroscience(2016,36(33):8734—8745).