Regulation of Neural Stem Cell Fate by Natural Products

Epigallocatechin-3-Gallate and Genistein for Decreasing Gut Dysbiosis, Inhibiting Inflammasomes, and Aiding Autophagy in Alzheimer's Disease

There are approximately 24 million cases of Alzheimer's disease (AD) worldwide, and the number of cases is expected to increase four-fold by 2050. AD is a neurodegenerative disease that leads to severe dementia in most patients. There are several neuropathological signs of AD, such as deposition of amyloid beta (Aβ) plaques, formation of neurofibrillary tangles (NFTs), neuronal loss, activation of inflammasomes, and declining autophagy. Several of these hallmarks are linked to the gut microbiome. The gastrointestinal (GI) tract contains microbial diversity, which is important in regulating several functions in the brain via the gut-brain axis (GBA). The disruption of the balance in the gut microbiota is known as gut dysbiosis. Recent studies strongly support that targeting gut dysbiosis with selective bioflavonoids is a highly plausible solution to attenuate activation of inflammasomes (contributing to neuroinflammation) and resume autophagy (a cellular mechanism for lysosomal degradation of the damaged components and recycling of building blocks) to stop AD pathogenesis. This review is focused on two bioflavonoids, specifically epigallocatechin-3-gallate (EGCG) and genistein (GS), as a possible new paradigm of treatment for maintaining healthy gut microbiota in AD due to their implications in modulating crucial AD signaling pathways. The combination of EGCG and GS has a higher potential than either agent alone to attenuate the signaling pathways implicated in AD pathogenesis. The effects of EGCG and GS on altering gut microbiota and GBA were also explored, along with conclusions from various delivery methods to increase the bioavailability of these bioflavonoids in the body.

A review on background, process and application of electrospun nanofibers for tissue regeneration

Electrospinning is a versatile method which is used to synthesize nano/micro sized fibers under the influence of electric field. Electrospun nanoscaffolds are one of the widely accepted platforms for cultivating soft and hard tissues as they create a prefect micro-environment for cell adhesion, proliferation and differentiation. Nanoscaffolds are widely used in the field of tissue engineering due to their versatility in aiding the growth of different types of cells and tissues for varied applications. The composition, molecular weight and structure of polymer used to fabricate nanoscaffold plays an important role in determining the size and strength of the nanofibers prepared. This review gives information about the background, process and different types of polymers used in electrospinning. Recent advances in culturing liver cells, osteoblasts, skin cells, neural cells and coronary artery smooth muscle cells on nanoscaffolds are also elucidated.

Kaempferia parviflora Extracts Protect Neural Stem Cells from Amyloid Peptide-Mediated Inflammation in Co-Culture Model with Microglia

The existence of neuroinflammation and oxidative stress surrounding amyloid beta (Aβ) plaques, a hallmark of Alzheimer's disease (AD), has been demonstrated and may result in the activation of neuronal death and inhibition of neurogenesis. Therefore, dysregulation of neuroinflammation and oxidative stress is one possible therapeutic target for AD. Kaempferia parviflora Wall. ex Baker (KP), a member of the Zingiberaceae family, possesses health-promoting benefits including anti-oxidative stress and anti-inflammation in vitro and in vivo with a high level of safety; however, the role of KP in suppressing Aβ-mediated neuroinflammation and neuronal differentiation has not yet been investigated. The neuroprotective effects of KP extract against Aβ₄₂ have been examined in both monoculture and co-culture systems of mouse neuroectodermal (NE-4C) stem cells and BV-2 microglia cells. Our results showed that fractions of KP extract containing 5,7-dimethoxyflavone, 5,7,4'-trimethoxyflavone, and 3,5,7,3',4'-pentamethoxyflavone protected neural stem cells (both undifferentiated and differentiated) and microglia activation from Aβ₄₂-induced neuroinflammation and oxidative stress in both monoculture and co-culture system of microglia and neuronal stem cells. Interestingly, KP extracts also prevented Aβ₄₂-suppressed neurogenesis, possibly due to the contained methoxyflavone derivatives. Our data indicated the promising role of KP in treating AD through the suppression of neuroinflammation and oxidative stress induced by Aβ peptides.

An update of nanotopographical surfaces in modulating stem cell fate: a narrative review

Stem cells have been one of the ideal sources for tissue regeneration owing to their capability of self-renewal and differentiation. In vivo, the extracellular microenvironment plays a vital role in modulating stem cell fate. When developing biomaterials for regenerative medicine, incorporating biochemical and biophysical cues to mimic extracellular matrix can enhance stem cell lineage differentiation. More specifically, modulating the stem cell fate can be achieved by controlling the nanotopographic features on synthetic surfaces. Optimization of nanotopographical features leads to desirable stem cell functions, which can maximize the effectiveness of regenerative treatment. In this review, nanotopographical surfaces, including static patterned surface, dynamic patterned surface, and roughness are summarized, and their fabrication, as well as the impact on stem cell behaviour, are discussed. Later, the recent progress of applying nanotopographical featured biomaterials for altering different types of stem cells is presented, which directs the design and fabrication of functional biomaterial. Last, the perspective in fundamental research and for clinical application in this field is discussed.

Ferulic Acid Induces NURR1 Expression and Promotes Dopaminergic Differentiation in Neural Precursor Cells

Degeneration of dopaminergic (DA) neurons in the substantia nigra is known as the main cause of Parkinson's disease (PD). Preventing the loss of DA neurons alongside the cell-replacement therapy have brought tremendous hope for the treatment of PD. For this purpose, various studies have been done to find the specific DA neuro-protective compounds or progressing DA-differentiation methods. Ferulic acid (FA) has strong neuro-protective effects, but at this point its role on protection and differentiation of DA neurons is not well-defined. Mouse neural stem cells (mNSCs) were treated with FA and expressions of TH (tyrosine hydroxylase) and NURR1 as the DA neuron specific markers were determined using real time qRT-PCR and immunostaining assays . Finally, efficacy of FA on DA differentiation was evaluated in comparison with other methods using fibroblast growth factor 8b (FGF8b) and sonic hedgehog (SHH). Treatment with FA could increase the Th and Nurr1 gene expressions in mNSCs. Also, it enhanced β - tubullin - III expression and increased the neurite length in treated groups. Real time qRT-PCR and immunostaining assays showed that FA could increase DA differentiation in mNSCs effectively. Also, gene expression profile in some groups showed that FA can raise the differentiation rate of other neuronal subtypes such as cholinergic neurons. FA effectively induces the DA differentiation in neural precursor cells by its ability to increase the expression of the NURR1 transcription factor, which is a known transcription factor for differentiation of midbrain DA neurons.

Functional Group-Dependent Induction of Astrocytogenesis and Neurogenesis by Flavone Derivatives

Neural stem cells (NSCs) differentiate into multiple cell types, including neurons, astrocytes, and oligodendrocytes, and provide an excellent platform to screen drugs against neurodegenerative diseases. Flavonoids exert a wide range of biological functions on several cell types and affect the fate of NSCs. In the present study, we investigated whether the structure-activity relationships of flavone derivatives influence NSC differentiation. As previously reported, we observed that PD98059 (2′-amino-3′-methoxy-flavone), compound 2 (3′-methoxy-flavone) induced astrocytogenesis. In the present study, we showed that compound 3 (2′-hydroxy-3′-methoxy-flavone), containing a 3′-methoxy group, and a non-bulky group at C2′ and C4′, induced astrocytogenesis through JAK-STAT3 signaling pathway. However, compound 1 and 7–12 without the methoxy group did not show such effects. Interestingly, the compounds 4 (2′,3′-dimethoxyflavone), 5 (2′-N-phenylacetamido-3′-methoxy-flavone), and 6 (3′,4′-dimethoxyflavone) containing 3′-methoxy could not promote astrocytic differentiation, suggesting that both the methoxy groups at C3′ and non-bulky group at C2′ and C4′ are required for the induction of astrocytogenesis. Notably, compound 6 promoted neuronal differentiation, whereas its 4′-demethoxylated analog, compound 2, repressed neurogenesis, suggesting an essential role of the methoxy group at C4′ in neurogenesis. These findings revealed that subtle structural changes of flavone derivatives have pronounced effects on NSC differentiation and can guide to design and develop novel flavone chemicals targeting NSCs fate regulation.

Berberine Protects C17.2 Neural Stem Cells From Oxidative Damage Followed by Inducing Neuronal Differentiation

Neurodegeneration is the loss of structure and/or function of neurons. Oxidative stress has been suggested as one of the common etiology in most of the neurodegenerative diseases. Previous studies have demonstrated the beneficial effects of berberine in various neurodegenerative and neuropsychiatric disorders. In this study, we hypothesized that berberine could protect C17.2 neural stem cells (NSCs) from 2,2′-Azobis(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative damage then promote neuronal differentiation. AAPH was used to induce oxidative damage. After the damage, berberine protected C17.2 cells were kept cultured for another week in differentiation medium with/without berberine. Changes in cell morphology were detected by microscopy and cell viability was determined by MTT assay. Real-time PCR and western blot analysis were performed to confirm the associated pathways. Berberine was able to protect C17.2 NSCs from the oxidative damage. It lowered the cellular reactive oxygen species (ROS) level in C17.2 cells via Nuclear Factor Erythroid 2-Related Factor 1/2 (NRF1/2) – NAD(P)H Quinone Dehydrogenase 1 (NQO-1) – Heme Oxygenase 1 (HO-1) pathway. It also down-regulated the apoptotic factors-Caspase 3 and Bcl2 Associated X (Bax) and upregulated the anti-apoptotic factor-Bcl2 to reduce cell apoptosis. Besides, berberine increased C17.2 cell viability via up-regulating Extracellular-signal-Related Kinase (ERK) and phosphor-Extracellular-signal-Related Kinase (pERK) expression. Then, berberine promoted C17.2 cell to differentiate into neurons and the differentiation mechanism involved the activation of WNT/β-catenin pathway as well as the upregulation of expression levels of pro-neural factors Achaete-Scute Complex-Like 1 (ASCL1), Neurogenin 1 (NeuroG1), Neuronal Differentiation 2 (NeuroD2) and Doublecortin (DCX). In conclusion, berberine protected C17.2 NSCs from oxidative damage then induced them to differentiate into neurons.