Hearing loss has become increasingly prevalent and causes considerable disability, thus gravely burdening the global economy. Irreversible loss of hair cells is a main cause of sensorineural hearing loss, and currently, the only relatively effective clinical treatments are limited to digital hearing equipment like cochlear implants and hearing aids, but these are of limited benefit in patients. It is therefore urgent to understand the mechanisms of damage repair in order to develop new neuroprotective strategies. At present, how to promote the regeneration of functional hair cells is a key scientific question in the field of hearing research. Multiple signaling pathways and transcriptional factors trigger the activation of hair cell progenitors and ensure the maturation of newborn hair cells, and in this article, we first review the principal mechanisms underlying hair cell reproduction. We then further discuss therapeutic strategies involving the co-regulation of multiple signaling pathways in order to induce effective functional hair cell regeneration after degeneration, and we summarize current achievements in hair cell regeneration. Lastly, we discuss potential future approaches, such as small molecule drugs and gene therapy, which might be applied for regenerating functional hair cells in the clinic.
Infant, Newborn ; Humans ; Hair Cells, Auditory, Inner/physiology* ; Ear, Inner/physiology* ; Hair Cells, Auditory/physiology* ; Regeneration/genetics* ; Stem Cells

Periodontal bone regeneration is a major challenge in the treatment of periodontitis. Currently the main obstacle is the difficulty of restoring the regenerative vitality of periodontal osteoblast lineages suppressed by inflammation, via conventional treatment. CD301b⁺ macrophages were recently identified as a subpopulation that is characteristic of a regenerative environment, but their role in periodontal bone repair has not been reported. The current study indicates that CD301b⁺ macrophages may be a constituent component of periodontal bone repair, and that they are devoted to bone formation in the resolving phase of periodontitis. Transcriptome sequencing suggested that CD301b⁺ macrophages could positively regulate osteogenesis-related processes. In vitro, CD301b⁺ macrophages could be induced by interleukin 4 (IL-4) unless proinflammatory cytokines such as interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α) were present. Mechanistically, CD301b⁺ macrophages promoted osteoblast differentiation via insulin-like growth factor 1 (IGF-1)/thymoma viral proto-oncogene 1 (Akt)/mammalian target of rapamycin (mTOR) signaling. An osteogenic inducible nano-capsule (OINC) consisting of a gold nanocage loaded with IL-4 as the "core" and mouse neutrophil membrane as the "shell" was designed. When injected into periodontal tissue, OINCs first absorbed proinflammatory cytokines in inflamed periodontal tissue, then released IL-4 controlled by far-red irradiation. These events collectively promoted CD301b⁺ macrophage enrichment, which further boosted periodontal bone regeneration. The current study highlights the osteoinductive role of CD301b⁺ macrophages, and suggests a CD301b⁺ macrophage-targeted induction strategy based on biomimetic nano-capsules for improved therapeutic efficacy, which may also provide a potential therapeutic target and strategy for other inflammatory bone diseases.
Animals ; Mice ; Bone Regeneration ; Cytokines/metabolism* ; Interleukin-4/therapeutic use* ; Macrophages/physiology* ; Mammals ; Osteogenesis ; Periodontitis/drug therapy*

Hepatic parenchymal cells are a type of liver cells that performs important functions such as metabolism and detoxification. The contribution of hepatic parenchymal cells, bile duct cells, and hepatic stem/progenitor cells to new hepatic parenchymal cells in the process of liver injury repair has become a controversial issue due to their strong proliferation ability. Lineage tracing technology, which has emerged in the past decade as a new method for exploring the origin of cells, can trace specific type of cells and their daughter cells by labeling cells that express the specific gene and their progeny. The article reviews the current literature on the origin and contribution of hepatic parenchymal cells by this technique. About 98% of new hepatic parenchymal cells originate from the existing hepatic parenchymal cells during liver homeostasis and after acute injury. However, under conditions of severe liver injury, such as inhibition of hepatic parenchymal cell proliferation, bile duct cells (mainly liver stem/progenitor cells) become the predominant source of hepatic parenchymal cells, contributing a steady increased hepatocyte regeneration with the extension of time.
Hepatocytes/metabolism* ; Liver/metabolism* ; Bile Ducts ; Stem Cells ; Liver Regeneration/physiology* ; Cell Differentiation

Spinal cord injury (SCI) disrupts the structural and functional connectivity between the higher center and the spinal cord, resulting in severe motor, sensory, and autonomic dysfunction with a variety of complications. The pathophysiology of SCI is complicated and multifaceted, and thus individual treatments acting on a specific aspect or process are inadequate to elicit neuronal regeneration and functional recovery after SCI. Combinatory strategies targeting multiple aspects of SCI pathology have achieved greater beneficial effects than individual therapy alone. Although many problems and challenges remain, the encouraging outcomes that have been achieved in preclinical models offer a promising foothold for the development of novel clinical strategies to treat SCI. In this review, we characterize the mechanisms underlying axon regeneration of adult neurons and summarize recent advances in facilitating functional recovery following SCI at both the acute and chronic stages. In addition, we analyze the current status, remaining problems, and realistic challenges towards clinical translation. Finally, we consider the future of SCI treatment and provide insights into how to narrow the translational gap that currently exists between preclinical studies and clinical practice. Going forward, clinical trials should emphasize multidisciplinary conversation and cooperation to identify optimal combinatorial approaches to maximize therapeutic benefit in humans with SCI.
Humans ; Axons/pathology* ; Nerve Regeneration/physiology* ; Spinal Cord Injuries/therapy* ; Neurons/pathology* ; Recovery of Function

OBJECTIVE: To investigate the effect of folic acid coated-crosslinked urethane-doped polyester elastomer (fCUPE) nerve conduit in repairing long distance peripheral nerve injury. METHODS: Thirty-six 3-month-old male Sprague Dawley rats weighing 180-220 g were randomly assigned to 3 groups, each consisting of 12 rats: CUPE nerve conduit transplantation group (group A), fCUPE nerve conduit transplantation group (group B), and autologous nerve transplantation group (group C), the contralateral healthy limb of group C served as the control group (group D). A 20-mm-long sciatic nerve defect model was established in rats, and corresponding materials were used to repair the nerve defect according to the group. The sciatic function index (SFI) of groups A-C was calculated using the Bain formula at 1, 2, and 3 months after operation. The nerve conduction velocity (NCV) of the affected side in groups A-D was assessed using neuroelectrophysiological techniques. At 3 months after operation, the regenerated nerve tissue was collected from groups A-C for S-100 immunohistochemical staining and Schwann cell count in groups A and B to compare the level of nerve repair and regeneration in each group. RESULTS: At 3 months after operation, the nerve conduits in all groups partially degraded. There was no significant adhesion between the nerve and the conduit and the surrounding tissues, the conduit was well connected with the distal and proximal nerves, and the nerve-like tissues in the conduit could be observed when the nerve conduit stents were cut off. SFI in group A was significantly higher than that in group C at each time point after operation and was significantly higher than that in group B at 2 and 3 months after operation ( P<0.05). There was no significant difference in SFI between groups B and C at each time point after operation ( P>0.05). NCV in group A was significantly slower than that in the other 3 groups at each time point after operation ( P<0.05). The NCV of groups B and C were slower than that of group D, but the difference was significant only at 1 month after operation ( P<0.05). There was no significant difference between groups B and C at each time point after operation ( P>0.05). Immunohistochemical staining showed that the nerve tissue of group A had an abnormal cavo-like structure, light tissue staining, and many non-Schwann cells. In group B, a large quantity of normal neural structures was observed, the staining was deeper than that in group A, and the distribution of dedifferentiated Schwann cells was obvious. In group C, the nerve bundles were arranged neatly, and the tissue staining was the deepest. The number of Schwann cells in group B was (727.50±57.60) cells/mm ², which was significantly more than that in group A [(298.33±153.12) cells/mm ²] ( t=6.139, P<0.001). CONCLUSION The fCUPE nerve conduit is effective in repairing long-distance sciatic nerve defects and is comparable to autologous nerve grafts. It has the potential to be used as a substitute material for peripheral nerve defect transplantation.
Rats ; Animals ; Male ; Rats, Sprague-Dawley ; Polyesters ; Peripheral Nerve Injuries/surgery* ; Elastomers ; Urethane ; Sciatic Nerve/injuries* ; Carbamates ; Nerve Tissue ; Nerve Regeneration/physiology*

Atoh1 gene encodes a helix-loop-helix transcription factor which is involved in the generation and differentiation of mammalian auditory hair cells and supporting cells, and regulation of the proliferation of cochlear cells, therefore plays an important role in the pathogenesis and recovery of sensorineural deafness. This study reviews the progress of the Atoh1 gene in hair cell regeneration, with the aim of providing a reference for the study of hair cell regeneration gene therapy for sensorineural deafness.
Animals ; Humans ; Basic Helix-Loop-Helix Transcription Factors/genetics* ; Hair Cells, Auditory/physiology* ; Transcription Factors ; Hearing Loss, Sensorineural ; Cell Differentiation ; Deafness ; Regeneration/genetics* ; Mammals

Artificial nerve guidance conduits (NGCs) are synthetic nerve grafts that are capable of providing the structural and nutritional support for nerve regeneration. The ideal NGCs have plenty of requirements on biocompatibility, mechanical strength, topological structure, and conductivity. Therefore, it is necessary to continuously improve the design of NGCs and establish a better therapeutic strategy for peripheral nerve injury in order to meet clinical needs. Although current NGCs have made certain process in the treatment of peripheral nerve injury, their nerve regeneration and functional outcomes on repairing long-distance nerve injury remain unsatisfactory. Herein, we review the nerve conduit design from four aspects, namely raw material selection, structural design, therapeutic factor loading and self-powered component integration. Moreover, we summarize the research progress of NGCs in the treatment of peripheral nerve injury, in order to facilitate the iterative updating and clinical transformation of NGCs.
Humans ; Peripheral Nerve Injuries/therapy* ; Guided Tissue Regeneration ; Nerve Regeneration/physiology* ; Sciatic Nerve

Sweat gland is one of the important appendage organs of the skin, which plays an important role in thermoregulation and homeostasis maintenance. Sweat glands are damaged and unable to self-repair after burns, resulting in perspiration disorders eventually. However, current clinical strategies cannot restore the function of the damaged sweat glands effectively. Therefore, it is urgent to seek treatments that can promote the regeneration of sweat glands and restore their normal functions. Stem cells have extensive sources, low immunogenicity, high proliferation capacity, and multi-directional differentiation potential, which have become a focus in the field of regenerative medicine. In recent years, a variety of stem cells have been induced to differentiate into sweat gland-like tissue with certain secretory function, which provides treatment direction for sweat gland regeneration after burns in clinic. This article reviews the recent research advances on the application of stem cells in sweat gland regeneration from the perspectives of the manner by which stem cells transform into sweat gland cells in different environments and their influencing factors.
Cell Differentiation/physiology* ; Regeneration/physiology* ; Skin ; Stem Cells ; Sweat Glands/physiology*

Distraction osteogenesis (DO) is widely used for bone tissue engineering technology. Immune regulations play important roles in the process of DO like other bone regeneration mechanisms. Compared with others, the immune regulation processes of DO have their distinct features. In this review, we summarized the immune-related events including changes in and effects of immune cells, immune-related cytokines, and signaling pathways at different periods in the process of DO. We aim to elucidated our understanding and unknowns about the immunomodulatory role of DO. The goal of this is to use the known knowledge to further modify existing methods of DO, and to develop novel DO strategies in our unknown areas through more detailed studies of the work we have done.
Bone Regeneration/physiology* ; Bone and Bones ; Osteogenesis/physiology* ; Osteogenesis, Distraction/methods* ; Tissue Engineering

Rats ; Animals ; Sciatic Neuropathy ; Muscle, Skeletal ; Sciatic Nerve/physiology* ; Sequence Analysis, RNA ; Nerve Regeneration/physiology*