Sonic Hedgehog Effectively Improves Oct4-Mediated Reprogramming of Astrocytes into Neural Stem Cells

Cell surface receptor-mediated signaling in CNS regeneration

Degenerative diseases and injuries of central nervous system (CNS) often cause nerve cell apoptosis and neural dysfunction. Protection of surviving cells or inducing the differentiation of stem cells into functional cells is considered to be an important way of neurorepair. In addition, transdifferentiation technology emerged recently is expected to provide new solutions for nerve regeneration. Cell surface receptors are transmembrane proteins embedded in cytoplasmic membrane, and play crucial roles in maintaining communication between extracellular signals and intracellular signaling processes. The extracellular microenvironment changed dramatically upon neural lesion, exploring the biological function of signals mediated by cell surface receptors will help to develop molecular strategies for nerve regeneration. An increasing number of studies have reported that cell surface receptor-mediated signaling affects the survival, differentiation, and functioning of neural cells, and even regulate their trans-lineage reprogramming. Here, we provide a review on the roles of cell surface receptors in CNS regeneration, thus providing new cues for better treatment of neurodegenerative diseases or nerve injury.

Transcription Factors in Brain Regeneration: A Potential Novel Therapeutic Target

Transcription factors play a crucial role in providing identity to each cell population. To maintain cell identity, it is essential to balance the expression of activator and inhibitor transcription factors. Cell plasticity and reprogramming offer great potential for future therapeutic applications, as they can regenerate damaged tissue. Specific niche factors can modify gene expression and differentiate or transdifferentiate the target cell to the required fate. Ongoing research is being carried out on the possibilities of transcription factors in regenerating neurons, with neural stem cells (NSCs) being considered the preferred cells for generating new neurons due to their epigenomic and transcriptome memory. NEUROD1/ASCL1, BRN2, MYTL1, and other transcription factors can induce direct reprogramming of somatic cells, such as fibroblasts, into neurons. However, the molecular biology of transcription factors in reprogramming and differentiation still needs to be fully understood.

Dauricine attenuates Oct4/sonic hedgehog co-activated stemness and induces reactive oxygen species-mediated mitochondrial apoptosis via AKT/β-catenin signaling in human neuroblastoma and glioblastoma stem-like cells

Neuroblastoma and glioblastoma are primary malignant tumors of the nervous system, with frequent relapse and limited clinical therapeutic drugs. The failure of their treatment is due to the tumor cells exhibiting cancer stem-like cells (CSLCs) properties. Octamer binding transcription factor 4 (Oct4) is involved in mediating CSLCs, our previous work found that Oct4-driven reprogramming of astrocytes into induced neural stem cells was potentiated with continuous sonic hedgehog (Shh) stimulation. In this study, we aimed to study the importance of Oct4 and Shh combination in the stemness properties induction of neuroblastoma and glioblastoma cells, and evaluate the anti-stemness effect of dauricine (DAU), a natural product of bis-benzylisoquinoline alkaloid. The effect of Oct4 and Shh co-activation on cancer stemness was evaluated by tumor spheres formation model and flow cytometry analysis. Then the effects of DAU on SH-SY5Y and T98-G cells were assessed by the MTT, colony formation, and tumor spheres formation model. DAU acts on Oct4 were verified using the Western blotting, MTT, and so on. Mechanistic studies were explored by siRNA transfection assay, Western blotting, and flow cytometry analysis. We identified that Shh effectively improved Oct4-mediated generation of stemness in SH-SY5Y and T98-G cells, and Oct4 and Shh co-activation promoted cell growth, the resistance of apoptosis. In addition, DAU, a natural product, was found to be able to attenuate Oct4/Shh co-activated stemness and induce cell cycle arrest and apoptosis via blocking AKT/β-catenin signaling in neuroblastoma and glioblastoma, which contributed to the neuroblastoma and glioblastoma cells growth inhibition by DAU. In summary, our results indicated that the treatment of DAU may be served as a potential therapeutic method in neuroblastoma and glioblastoma.

Mini-review: "Enteric glia functions in nervous tissue repair: Therapeutic target or tool?"

In the body, nerve tissue is not only present in the central nervous system, but also in the periphery. The enteric nervous system (ENS) is a highly organized intrinsic network of neurons and glial cells grouped to form interconnected ganglia. Glial cells in the ENS are a fascinating cell population: their neurotrophic role is well established, as well as their plasticity in specific circumstances. Gene expression profiling studies indicate that ENS glia retain neurogenic potential. The identification of neurogenic glial subtype(s) and the molecular basis of glia-derived neurogenesis may have profound biological and clinical implications. In this review, we discuss the potential of using gene-editing for ENS glia and cell transplantation as therapies for enteric neuropathies. Glia in the ENS: target or tool for nerve tissue repair?

Regulation of Morphogenetic Processes during Postnatal Development and Physiological Regeneration of the Adrenal Medulla

Regulation of morphogenetic processes during postnatal development of the rat adrenal medulla was studied. Termination of the adrenal medulla growth was found to be associated with decreased chromaffin cell proliferation, activation of canonical Wnt-signaling pathway, and enhanced expression of Sonic Hedgehog ligand. Analysis of transcription factors associated with pluripotency revealed increased percentage of Oct4-expressing cells by the end of medulla growth and no signs of Sox2 expression. All the cells demonstrating activation of Wnt-signaling and expression of Oct4 and Sonic Hedgehog were found to be highly differentiated chromaffin cells actively producing tyrosine hydroxylase. These findings allow considering the formation of the cell pools for dedifferentiation as a putative mechanism for physiological regeneration of the adrenal medulla.

Astrocyte-to-neuron reprogramming and crosstalk in the treatment of Parkinson's disease

Parkinson's disease (PD) is currently the fastest growing disabling neurological disorder worldwide, with motor and non-motor symptoms being its main clinical manifestations. The primary pathological features include a reduction in the number of dopaminergic neurons in the substantia nigra and decrease in dopamine levels in the nigrostriatal pathway. Existing treatments only alleviate clinical symptoms and do not stop disease progression; slowing down the loss of dopaminergic neurons and stimulating their regeneration are emerging therapies. Preclinical studies have demonstrated that transplantation of dopamine cells generated from human embryonic or induced pluripotent stem cells can restore the loss of dopamine. However, the application of cell transplantation is limited owing to ethical controversies and the restricted source of cells. Until recently, the reprogramming of astrocytes to replenish lost dopaminergic neurons has provided a promising alternative therapy for PD. In addition, repair of mitochondrial perturbations, clearance of damaged mitochondria in astrocytes, and control of astrocyte inflammation may be extensively neuroprotective and beneficial against chronic neuroinflammation in PD. Therefore, this review primarily focuses on the progress and remaining issues in astrocyte reprogramming using transcription factors (TFs) and miRNAs, as well as exploring possible new targets for treating PD by repairing astrocytic mitochondria and reducing astrocytic inflammation.

OCT4 protein and gene expression analysis in the differentiation of spermatogonia stem cells into neurons by immunohistochemistry, immunocytochemistry, and bioinformatics analysis

BACKGROUND

Spermatogonia Stem Cells (SSCs) are potential candidates for reprogramming and regeneration. Recent studies have revealed that differentiated cells can be reverted to pluripotent by overexpressing a set of pluripotent transcription factors. OCT4 (encoded by pou5f1), a POU transcription factor family member, is essential to the potential that controls pluripotency, and it is widely expressed in pluripotent stem cells, although it decreased or suppressed after differentiation.

METHODS

In this investigated research, we examined the OCT4 expression during the differentiation of SSCs into neurons (involving four stages in the following order: SSCs in vivo and in-vitro, embryonic Stem Cell-like (ES-like), Embryonic Bodies (EBs), and finally Neurons) by Immunocytochemistry (ICC), Immunohistochemistry (IMH), and Fluidigm Real-Time polymerase chain reaction. In addition, we use some databases like STRING to predict protein-protein interaction and enrichment analysis.

RESULTS

We evaluated the expression of OCT4 in this process, and we observed that it is expressed in SSCs, ES-like, and EBs during the differentiation of spermatogonia stem cells into adult neurons. We show that by adding RA to EBs, the expression of OCT4 is reduced and is not expressed in the neuron cells. We observed that the expression of OCT4 is linked and interacts with the differentiation of spermatogonia stem cells into neuron cells, and it has been shown to be biologically functional, like stem cell maintenance and somatic cell reprogramming.

CONCLUSION

Our findings can help us better understand the process of differentiation of spermatogonia stem cells into neurons, and it can be effective in finding new and more efficient treatments for neurogenesis and repair of neurons. We examined the OCT4 expression during the differentiation of SSCs into neurons (involving four stages in the following order: SSCs in vivo and in-vitro, embryonic Stem Cell-like (ES-like), Embryonic Bodies (EBs), and finally Neurons) by Immunocytochemistry (ICC), Immunohistochemistry (IMH), and Fluidigm Real-Time polymerase chain reaction. In addition, we use some databases like STRING to predict protein-protein interaction and enrichment analysis. We evaluated the expression of OCT4 in this process, and we observed that it is expressed in SSCs, ES-like, and EBs during the differentiation of spermatogonia stem cells into adult neurons. We show that by adding RA to EBs, the expression of OCT4 is reduced and is not expressed in the neuron cells. We observed that the expression of OCT4 is linked and interacts with the differentiation of spermatogonia stem cells into neuron cells, and it has been shown to be biologically functional, like stem cell maintenance and somatic cell reprogramming.

Astrocytes express aberrant immunoglobulins as putative gatekeeper of astrocytes to neuronal progenitor conversion

Using multi-omics analyses including RNAseq, RT-PCR, RACE-PCR, and shotgun proteomic with enrichment strategies, we demonstrated that newborn rat astrocytes produce neural immunoglobulin constant and variable heavy chains as well as light chains. However, their edification is different from the ones found in B cells and they resemble aberrant immunoglobulins observed in several cancers. Moreover, the complete enzymatic V(D)J recombination complex has also been identified in astrocytes. In addition, the constant heavy chain is also present in adult rat astrocytes, whereas in primary astrocytes from human fetus we identified constant and variable kappa chains as well as the substitution lambda chains known to be involved in pre-B cells. To gather insights into the function of these neural IgGs, CRISPR-Cas9 of IgG2B constant heavy chain encoding gene (Igh6), IgG2B overexpression, proximal labeling of rat astrocytes IgG2B and targets identification through 2D gels were performed. In Igh6 KO astrocytes, overrepresentation of factors involved in hematopoietic cells, neural stem cells, and the regulation of neuritogenesis have been identified. Moreover, overexpression of IgG2B in astrocytes induces the CRTC1-CREB-BDNF signaling pathway known to be involved in gliogenesis, whereas Igh6 KO triggers the BMP/YAP1/TEAD3 pathway activated in astrocytes dedifferentiation into neural progenitors. Proximal labeling experiments revealed that IgG2B is N-glycosylated by the OST complex, addressed to vesicle membranes containing the ATPase complex, and behaves partially like CD98hc through its association with LAT1. These experiments also suggest that proximal IgG2B-LAT1 interaction occurs concomitantly with MACO-1 and C2CD2L, at the heart of a potentially novel cell signaling platform. Finally, we demonstrated that these chains are synthesized individually and associated to recognize specific targets. Indeed, intermediate filaments Eif4a2 and Pdia6 involved in astrocyte fate constitute targets for these neural IgGs. Taken together, we hypothese that neural aberrant IgG chains may act as gatekeepers of astrocytes' fate.

Generation of neural organoids for spinal-cord regeneration via the direct reprogramming of human astrocytes

Organoids with region-specific architecture could facilitate the repair of injuries of the central nervous system. Here we show that human astrocytes can be directly reprogrammed into early neuroectodermal cells via the overexpression of OCT4, the suppression of p53 and the provision of the small molecules CHIR99021, SB431542, RepSox and Y27632. We also report that the activation of signalling mediated by fibroblast growth factor, sonic hedgehog and bone morphogenetic protein 4 in the reprogrammed cells induces them to form spinal-cord organoids with functional neurons specific to the dorsal and ventral domains. In mice with complete spinal-cord injury, organoids transplanted into the lesion differentiated into spinal-cord neurons, which migrated and formed synapses with host neurons. The direct reprogramming of human astrocytes into neurons may pave the way for in vivo neural organogenesis from endogenous astrocytes for the repair of injuries to the central nervous system.

The aOECs Facilitate the Neuronal Differentiation of Neural Stem Cells in the Inflammatory Microenvironment Through Up-Regulation of Bioactive Factors and Activation of Wnt3/β-Catenin Pathway

The therapeutic application of neural stem cells (NSCs) in the central nerve system (CNS) injury is a promising strategy for combating irreversible neuronal loss. However, a variety of obvious inflammatory responses following nerve injury rapidly create an unfavorable microenvironment for survival and neuronal differentiation of NSCs in lesion area, limiting the efficacy of NSC-based therapy for CNS injury. It remained unknown how to effectively increase the neuronal differentiation efficiency of NSCs through transplantation. Here, we demonstrated that curcumin (CCM)-activated olfactory ensheathing cells (aOECs) effectively promoted neuronal differentiation of NSCs in the activated microglial inflammatory condition, and co-transplantation of aOECs and NSCs improved neurological recovery of rats after spinal cord injury (SCI), as evidenced by higher expression levels of neuronal markers and lower expression levels of glial markers in the differentiated cells, greater number of Tuj-1-positive cells as well as higher Basso, Beattie, and Bresnahan (BBB) locomotor scale, compared to the corresponding controls. Pathologically, hematoxylin and eosin (HE) staining and immunostaining also showed that aOECs remarkably enhanced the in vivo neuronal differentiation of NSCs and migration, and nerve repair. Further analysis revealed that the underlying mechanisms of aOECs potentiating the neuronal conversion of NSCs under inflammatory environment were tightly associated with up-regulation of anti-inflammatory cytokines and neurotrophic factors in OECs, and importantly, the activation of Wnt3/β-catenin pathway was likely involved in the mechanisms underlying the observed cellular events. Therefore, this study provides a promising strategy for SCI repair by co-transplantation of aOECs and NSCs.

Modification of Müller Glial Cell Fate and Proliferation with the Use of Small Molecules

In recent years, reprogramming Müller glia by overexpressing Ascl1 and other transcription factors has shown promise for the regeneration of postmitotic retinal neurons, primarily bipolar cells, following injury. Müller glial proliferation and efficiency of neuronal differentiation can be modified by the use of small molecules in various systems. The molecules and pathways studied thus far share remarkable consistency with astrocytes. In this mini review, we provide an overview on the modulation of Müller glial proliferation and cell fate using small molecules in injury and reprogramming. We also compare these observations to what has been observed in astrocytes.

Rho Kinase Inhibitor Y27632 Improves Recovery After Spinal Cord Injury by Shifting Astrocyte Phenotype and Morphology via the ROCK/NF-κB/C3 Pathway

Spinal cord injury (SCI) usually results in loss or reduction in motor and sensory functions. Despite extensive research, no available therapy can restore the lost functions after SCI. Reactive astrocytes play a pivotal role in SCI. Rho kinase inhibitors have also been shown to promote functional recovery of SCI. However, the role of Rho kinase inhibitors in reactive astrocytic phenotype switch within SCI remains largely unexplored. In this study, astrocytes were treated with proinflammatory cytokines and/or the Rho kinase inhibitor Y27632. Concomitantly the phenotype and morphology of astrocytes were examined. Meanwhile, the SCI model of SD rats was established, and nerve functions were evaluated following treatment with Y27632. Subsequently, the number of A1 astrocytes in the injured area was observed and analyzed. Eventually, the expression levels of nuclear factor kappa B (NF-κB), C3, and S100A10 were measured. The present study showed that the Rho kinase inhibitor Y27632 improved functional recovery of SCI and elevated the proliferation and migration abilities of the astrocytes. In addition, Y27632 treatment initiated the switch of astrocytes morphology from a flattened shape to a process-bearing shape and transformed the reactive astrocytes A1 phenotype to an A2 phenotype. More importantly, further investigation suggested that Y27632 was actively involved in promoting the functional recovery of SCI in rats by inhabiting the ROCK/NF-κB/C3 signaling pathway. Together, Rho kinase inhibitor Y27632 effectively promotes the functional recovery of SCI by shifting astrocyte phenotype and morphology. Furthermore, the pro-regeneration event is strongly associated with the ROCK/NF-κB/C3 signal pathway.

Generation of a Pure Culture of Neuron-like Cells with a Glutamatergic Phenotype from Mouse Astrocytes

Astrocyte-to-neuron reprogramming is a promising therapeutic approach for treatment of neurodegenerative diseases. The use of small molecules as an alternative to the virus-mediated ectopic expression of lineage-specific transcription factors negates the tumorigenic risk associated with viral genetic manipulation and uncontrolled differentiation of stem cells. However, because previously developed methods for small-molecule reprogramming of astrocytes to neurons are multistep, complex, and lengthy, their applications in biomedicine, including clinical treatment, are limited. Therefore, our objective in this study was to develop a novel chemical-based approach to the cellular reprogramming of astrocytes into neurons with high efficiency and low complexity. To accomplish that, we used C8-D1a, a mouse astrocyte cell line, to assess the role of small molecules in reprogramming protocols that otherwise suffer from inconsistencies caused by variations in donor of the primary cell. We developed a new protocol by which a chemical mixture formulated with Y26732, DAPT, RepSox, CHIR99021, ruxolitinib, and SAG rapidly and efficiently induced the neural reprogramming of astrocytes in four days, with a conversion efficiency of 82 ± 6%. Upon exposure to the maturation medium, those reprogrammed cells acquired a glutaminergic phenotype over the next eleven days. We also demonstrated the neuronal functionality of the induced cells by confirming KCL-induced calcium flux.

Reactive Astrocytes in Central Nervous System Injury: Subgroup and Potential Therapy

Traumatic central nervous system (CNS) injury, which includes both traumatic brain injury (TBI) and spinal cord injury (SCI), is associated with irreversible loss of neurological function and high medical care costs. Currently, no effective treatment exists to improve the prognosis of patients. Astrocytes comprise the largest population of glial cells in the CNS and, with the advancements in the field of neurology, are increasingly recognized as having key functions in both the brain and the spinal cord. When stimulated by disease or injury, astrocytes become activated and undergo a series of changes, including alterations in gene expression, hypertrophy, the loss of inherent functions, and the acquisition of new ones. Studies have shown that astrocytes are highly heterogeneous with respect to their gene expression profiles, and this heterogeneity accounts for their observed context-dependent phenotypic diversity. In the inured CNS, activated astrocytes play a dual role both as regulators of neuroinflammation and in scar formation. Identifying the subpopulations of reactive astrocytes that exert beneficial or harmful effects will aid in deciphering the pathological mechanisms underlying CNS injuries and ultimately provide a theoretical basis for the development of effective strategies for the treatment of associated conditions. Following CNS injury, as the disease progresses, astrocyte phenotypes undergo continuous changes. Although current research methods do not allow a comprehensive and accurate classification of astrocyte subpopulations in complex pathological contexts, they can nonetheless aid in understanding the roles of astrocytes in disease. In this review, after a brief introduction to the pathology of CNS injury, we summarize current knowledge regarding astrocyte activation following CNS injury, including: (a) the regulatory factors involved in this process; (b) the functions of different astrocyte subgroups based on the existing classification of astrocytes; and (c) attempts at astrocyte-targeted therapy.

In vivo Direct Conversion of Astrocytes to Neurons Maybe a Potential Alternative Strategy for Neurodegenerative Diseases

Partly because of extensions in lifespan, the incidence of neurodegenerative diseases is increasing, while there is no effective approach to slow or prevent neuronal degeneration. As we all know, neurons cannot self-regenerate and may not be replaced once being damaged or degenerated in human brain. Astrocytes are widely distributed in the central nervous system (CNS) and proliferate once CNS injury or neurodegeneration occur. Actually, direct reprogramming astrocytes into functional neurons has been attracting more and more attention in recent years. Human astrocytes can be successfully converted into neurons in vitro. Notably, in vivo direct reprogramming of astrocytes into functional neurons were achieved in the adult mouse and non-human primate brains. In this review, we briefly summarized in vivo direct reprogramming of astrocytes into functional neurons as regenerative strategies for CNS diseases, mainly focusing on neurodegenerative diseases such as Parkinson’s disease (PD), Alzheimer’s disease (AD), and Huntington’s disease (HD). We highlight and outline the advantages and challenges of direct neuronal reprogramming from astrocytes in vivo for future neuroregenerative medicine.

RhoA/ROCK signaling pathway and astrocytes in ischemic stroke

Ischemic stroke is one of the most common and undertreated cerebral diseases with high mortality and disability rate. Various intrinsic and extrinsic factors regulate the onset, severity, and progression of ischemic stroke. As an integral part of the neuronal glia system, astrocytes provide many housekeeping functions in nervous system, and perform multiple functions both beneficial and detrimental for neuronal survival after ischemic stroke. In addition, the small GTPase Rho and its downstream Rho kinase (ROCK) are associated with various neuronal functions such as dendrite development, migration and axonal extension, and numerous central nervous system (CNS) diseases. The aim of this review is to summarize the role of RhoA/ROCK signaling pathway and astrocytes on neurological function after ischemic stroke. We also discuss the interaction of RhoA/ROCK signaling pathway and astrocytes on the tissue repair after brain injury.

Relationship between lipid metabolism and Hedgehog signaling pathway

The Hedgehog (Hh) signaling pathway is highly conserved signaling pathway in cells. Steroids was found to play a vital role in Hh signaling pathway and aberrant Hh signaling was found to lead a series of disease correlate with abnormal lipid metabolism. This paper aimed to elucidate the relationship between lipid metabolism and Hedgehog signaling pathway.

1-[(4-Nitrophenyl)sulfonyl]-4-phenylpiperazine treatment after brain irradiation preserves cognitive function in mice

BACKGROUND

Normal tissue toxicity is an inevitable consequence of primary or secondary brain tumor radiotherapy. Cranial irradiation commonly leads to neurocognitive deficits that manifest months or years after treatment. Mechanistically, radiation-induced loss of neural stem/progenitor cells, neuroinflammation, and demyelination are contributing factors that lead to progressive cognitive decline.

METHODS

The effects of 1-[(4-nitrophenyl)sulfonyl]-4-phenylpiperazine (NSPP) on irradiated murine neurospheres, microglia cells, and patient-derived gliomaspheres were assessed by sphere-formation assays, flow cytometry, and interleukin (IL)-6 enzyme-linked immunosorbent assay. Activation of the hedgehog pathway was studied by quantitative reverse transcription PCR. The in vivo effects of NSPP were analyzed using flow cytometry, sphere-formation assays, immunohistochemistry, behavioral testing, and an intracranial mouse model of glioblastoma.

RESULTS

We report that NSPP mitigates radiation-induced normal tissue toxicity in the brains of mice. NSPP treatment significantly increased the number of neural stem/progenitor cells after brain irradiation in female animals, and inhibited radiation-induced microglia activation and expression of the pro-inflammatory cytokine IL-6. Behavioral testing revealed that treatment with NSPP after radiotherapy was able to successfully mitigate radiation-induced decline in memory function of the brain. In mouse models of glioblastoma, NSPP showed no toxicity and did not interfere with the growth-delaying effects of radiation.

CONCLUSIONS

We conclude that NSPP has the potential to mitigate cognitive decline in patients undergoing partial or whole brain irradiation without promoting tumor growth and that the use of this compound as a radiation mitigator of radiation late effects on the central nervous system warrants further investigation.

Understanding stem cells and its pivotal role in regenerative medicine

Stem cells (SCs) are clonogenic cells that develop into the specialized cells which later responsible for making up various types of tissue in the human body. SCs are not only the appropriate source of information for cell division, molecular and cellular processes, and tissue homeostasis but also one of the major putative biological aids to diagnose and cure various degenerative diseases. This study emphasises on various research outputs that occurred in the past two decades. This will give brief information on classification, differentiation, detection, and various isolation techniques of SCs. Here, the various signalling pathways which includes WNT, Sonic hedgehog, Notch, BMI1 and C-met pathways and how does it effect on the regeneration of various classes of SCs and factors that regulates the potency of the SCs are also been discussed. We also focused on the application of SCs in the area of regenerative medicine along with the cellular markers that are useful as salient diagnostic or curative tools or in both, by the process of reprogramming, which includes diabetes, cancer, cardiovascular disorders and neurological disorders. The biomarkers that are mentioned in various literatures and experiments include PDX1, FOXA2, HNF6, and NKX6-1 (for diabetes); CD33, CD24, CD133 (for cancer); c-Kit, SCA-1, Wilm's tumor 1 (for cardiovascular disorders); and OCT4, SOX2, c-MYC, EN1, DAT and VMAT2 (for neurological disorders). In this review, we come to know the advancements and scopes of potential SC-based therapies, its diverse applications in clinical fields that can be helpful in the near future.

Dedifferentiation: inspiration for devising engineering strategies for regenerative medicine

Cell dedifferentiation is the process by which cells grow reversely from a partially or terminally differentiated stage to a less differentiated stage within their own lineage. This extraordinary phenomenon, observed in many physiological processes, inspires the possibility of developing new therapeutic approaches to regenerate damaged tissue and organs. Meanwhile, studies also indicate that dedifferentiation can cause pathological changes. In this review, we compile the literature describing recent advances in research on dedifferentiation, with an emphasis on tissue-specific findings, cellular mechanisms, and potential therapeutic applications from an engineering perspective. A critical understanding of such knowledge may provide fresh insights for designing new therapeutic strategies for regenerative medicine based on the principle of cell dedifferentiation.

Adult neurogenesis from reprogrammed astrocytes

The details of adult neurogenesis, including environmental triggers, region specificity, and species homology remain an area of intense investigation. Slowing or halting age-related cognitive dysfunction, or restoring neurons lost to disease or injury represent just a fraction of potential therapeutic applications. New neurons can derive from stem cells, pluripotent neural progenitor cells, or non-neuronal glial cells, such as astrocytes. Astrocytes must be epigenetically “reprogrammed” to become neurons, which can occur both naturally in vivo, and via artificial exogenous treatments. While neural progenitor cells are localized to a few neurogenic zones in the adult brain, astrocytes populate almost every brain structure. In this review, we will summarize recent research into neurogenesis that arises from conversion of post-mitotic astrocytes, detail the genetic and epigenetic pathways that regulate this process, and discuss the possible clinical relevance in supplementing stem-cell neurogenic therapies.