Niche-dependent inhibition of neural stem cell proliferation and oligodendrogenesis is mediated by the presence of myelin basic protein

Optimized approach for active peptides identification in Cerebrolysin by nanoLC-MS

Cerebrolysin (CBL) is a peptide-rich preparation made by hydrolysis and purified extraction of porcine brain. CBL contains various neuroprotective peptides, such as neurotrophic factor, nerve growth factor and ciliary neurotrophic factor, which can be used to treat neurodegenerative diseases. However, the active peptides in CBL had not been studied in depth. In this study, the following was carried out in order to investigate the active peptides in CBL. First, CBL samples were treated using organic reagents (acetonitrile and acetone) to precipitate the proteins and different solid phase extraction methods (MCX mixed-mode cartridges, C18 SPE cartridge columns and HILIC sorbent). Then the samples were analyzed using nanoLC-MS, followed by the identification of peptides using different sequence analysis software (PEAKS, pNovo and novor). Finally, bioinformatics analysis was performed to predict peptides with potential neuroprotective functions in CBL, such as anti-inflammatory and antioxidant peptides. Results showed that the number of peptides obtained by the MCX method coupled with PEAKS was the highest and the method was the most stable. Bioinformatic analysis of the detected peptides showed that two anti-inflammatory peptides (LLNLQPPPR and LSPSLRLP) and an antioxidant peptide (WPFPR) might be neuroprotective peptides in CBL. In addition, this study found that some peptides in CBL were present in myelin basic protein and tubulin beta chain. The results of this study for the detection of active peptides in CBL laid the foundation for the subsequent study of its active ingredients.

Regulating Endogenous Neural Stem Cell Activation to Promote Spinal Cord Injury Repair

Spinal cord injury (SCI) affects millions of individuals worldwide. Currently, there is no cure, and treatment options to promote neural recovery are limited. An innovative approach to improve outcomes following SCI involves the recruitment of endogenous populations of neural stem cells (NSCs). NSCs can be isolated from the neuroaxis of the central nervous system (CNS), with brain and spinal cord populations sharing common characteristics (as well as regionally distinct phenotypes). Within the spinal cord, a number of NSC sub-populations have been identified which display unique protein expression profiles and proliferation kinetics. Collectively, the potential for NSCs to impact regenerative medicine strategies hinges on their cardinal properties, including self-renewal and multipotency (the ability to generate de novo neurons, astrocytes, and oligodendrocytes). Accordingly, endogenous NSCs could be harnessed to replace lost cells and promote structural repair following SCI. While studies exploring the efficacy of this approach continue to suggest its potential, many questions remain including those related to heterogeneity within the NSC pool, the interaction of NSCs with their environment, and the identification of factors that can enhance their response. We discuss the current state of knowledge regarding populations of endogenous spinal cord NSCs, their niche, and the factors that regulate their behavior. In an attempt to move towards the goal of enhancing neural repair, we highlight approaches that promote NSC activation following injury including the modulation of the microenvironment and parenchymal cells, pharmaceuticals, and applied electrical stimulation.

Adhesive, Stretchable, and Spatiotemporal Delivery Fibrous Hydrogels Harness Endogenous Neural Stem/Progenitor Cells for Spinal Cord Injury Repair

Aligned fibrous hydrogels capable of recruiting endogenous neural stem/progenitor cells (NSPCs) show great promise in spinal cord injury (SCI) repair. However, the hydrogels suffer from severe issues in close contact with the transected nerve stumps and harnessing the NSPC fate in the lesion microenvironment. Herein, we report aligned collagen-fibrin (Col-FB) fibrous hydrogels with stretchable property, adhesive behavior, and stromal cell-derived factor-1α (SDF1α)/paclitaxel (PTX) spatiotemporal delivery capability. The resultant Col-FB fibrous hydrogels exhibited 1.98 times longer elongation at break (230%), 2.55 times lower Young's modulus (17.93 ± 1.16 KPa), and 2.21 times greater adhesive strength (3.45 ± 0.48 KPa) than collagen (Col) fibrous hydrogels. The soft aligned fibrous hydrogels simulate the oriented microstructure and soft tissue feature of a natural spinal cord and provide elasticity and adhesivity to ensure a persistent close contact with host stumps. The repair of complete transection SCI in rats demonstrates that "middle-to-bilateral" SDF1α gradient release induced endogenous NSPC migration to the lesion site in 10 days, and SDF1α/PTX sequential release promoted neuronal differentiation of the recruited NSPCs over 8 weeks, leading to hind limb locomotion recovery. The presented strategy was proved to be efficient for harnessing endogenous NSPCs, which facilitate SCI repair significantly.

Hepatoma Derived Growth Factor Enhances Oligodendrocyte Genesis from Subventricular Zone Precursor Cells

Oligodendrocytes, the myelinating cells of the central nervous system (CNS), perform vital functions in neural protection and communication, as well as cognition. Enhanced production of oligodendrocytes has been identified as a therapeutic approach for neurodegenerative and neurodevelopmental disorders. In the postnatal brain, oligodendrocytes are generated from the neural stem and precursor cells (NPCs) in the subventricular zone (SVZ) and parenchymal oligodendrocyte precursor cells (OPCs). Here, we demonstrate exogenous Hepatoma Derived Growth Factor (HDGF) enhances oligodendrocyte genesis from murine postnatal SVZ NPCs in vitro without affecting neurogenesis or astrogliogenesis. We further show that this is achieved by increasing proliferation of both NPCs and OPCs, as well as OPC differentiation into oligodendrocytes. In vivo results demonstrate that intracerebroventricular infusion of HDGF leads to increased oligodendrocyte genesis from SVZ NPCs, as well as OPC proliferation. Our results demonstrate a novel role for HDGF in regulating SVZ precursor cell proliferation and oligodendrocyte differentiation.

RNA Profiling of Mouse Ependymal Cells after Spinal Cord Injury Identifies the Oncostatin Pathway as a Potential Key Regulator of Spinal Cord Stem Cell Fate

Ependymal cells reside in the adult spinal cord and display stem cell properties in vitro. They proliferate after spinal cord injury and produce neurons in lower vertebrates but predominantly astrocytes in mammals. The mechanisms underlying this glial-biased differentiation remain ill-defined. We addressed this issue by generating a molecular resource through RNA profiling of ependymal cells before and after injury. We found that these cells activate STAT3 and ERK/MAPK signaling post injury and downregulate cilia-associated genes and FOXJ1, a central transcription factor in ciliogenesis. Conversely, they upregulate 510 genes, seven of them more than 20-fold, namely Crym, Ecm1, Ifi202b, Nupr1, Rbp1, Thbs2 and Osmr—the receptor for oncostatin, a microglia-specific cytokine which too is strongly upregulated after injury. We studied the regulation and role of Osmr using neurospheres derived from the adult spinal cord. We found that oncostatin induced strong Osmr and p-STAT3 expression in these cells which is associated with reduction of proliferation and promotion of astrocytic versus oligodendrocytic differentiation. Microglial cells are apposed to ependymal cells in vivo and co-culture experiments showed that these cells upregulate Osmr in neurosphere cultures. Collectively, these results support the notion that microglial cells and Osmr/Oncostatin pathway may regulate the astrocytic fate of ependymal cells in spinal cord injury.

Niche-dependent inhibition of neural stem cell proliferation and oligodendrogenesis is mediated by the presence of myelin basic protein

Neural stem and progenitor cells (collectively termed neural precursor cells [NPCs]) are found along the ventricular neuraxis extending from the spinal cord to the forebrain in regionally distinct niches comprised of different cell types, architecture, and cell-cell interactions. An understanding of the factors that regulate NPC behavior is critical for developing therapeutics to repair the injured central nervous system. Herein, we demonstrate that myelin basic protein (MBP), the major cytoplasmic protein constituent of the myelin sheath in oligodendrocytes, can regulate NPC behavior. Under physiological conditions, NPCs are not in contact with intracellular MBP; however, upon injury, MBP is released into the neural parenchyma. We reveal that MBP presented in a spinal cord niche is inhibitory to NPC proliferation. This inhibitory effect is regionally distinct as spinal cord NPCs, but not forebrain-derived NPCs, are inhibited by MBP. We performed coculture and conditioned media experiments that reveal the stem cell niche is a key regulator of MBP's inhibitory actions on NPCs. The inhibition is mediated by a heat-labile protein released by spinal cord niche cells, but not forebrain niche cells. However, forebrain NPCs are also inhibited by the spinal cord derived factor as revealed following in vivo infusion of the spinal cord niche-derived conditioned media. Moreover, we show that MBP inhibits oligodendrogenesis from NPCs. Together, these findings highlight the role of MBP and the regionally distinct microenvironment in regulating NPC behavior which has important implications for stem cell-based regenerative strategies.