Myelin Debris Impairs Tight Junctions and Promotes the Migration of Microvascular Endothelial Cells in the Injured Spinal Cord.

Clearance of myelin debris caused by acute demyelination is an essential process for functional restoration following spinal cord injury (SCI). Microvascular endothelial cells, acting as "amateur" phagocytes, have been confirmed to engulf and degrade myelin debris, promoting the inflammatory response, robust angiogenesis, and persistent fibrosis. However, the effect of myelin debris engulfment on the function of endothelial tight junctions (TJs) remains unclear. Here, we demonstrate that myelin debris uptake impairs TJs and gap junctions of endothelial cells in the lesion core of the injured spinal cord and in vitro, resulting in increased permeability and leakage. We further show that myelin debris acts as an inducer to regulate the endothelial-to-mesenchymal transition in a dose-dependent manner and promotes endothelial cell migration through the PI3K/AKT and ERK signaling pathways. Together, our results indicate that myelin debris engulfment impairs TJs and promotes the migration of endothelial cells. Accelerating myelin debris clearance may help maintain blood-spinal cord barrier integrity, thus facilitating restoration of motor and sensory function following SCI.

SU16f inhibits fibrotic scar formation and facilitates axon regeneration and locomotor function recovery after spinal cord injury by blocking the PDGFRß pathway.

BACKGROUND: Excessively deposited fibrotic scar after spinal cord injury (SCI) inhibits axon regeneration. It has been reported that platelet-derived growth factor receptor beta (PDGFRß), as a marker of fibrotic scar-forming fibroblasts, can only be activated by platelet-derived growth factor (PDGF) B or PDGFD. However, whether the activation of the PDGFRß pathway can mediate fibrotic scar formation after SCI remains unclear. METHODS: A spinal cord compression injury mouse model was used. In situ injection of exogenous PDGFB or PDGFD in the spinal cord was used to specifically activate the PDGFRß pathway in the uninjured spinal cord, while intrathecal injection of SU16f was used to specifically block the PDGFRß pathway in the uninjured or injured spinal cord. Immunofluorescence staining was performed to explore the distributions and cell sources of PDGFB and PDGFD, and to evaluate astrocytic scar, fibrotic scar, inflammatory cells and axon regeneration after SCI. Basso Mouse Scale (BMS) and footprint analysis were performed to evaluate locomotor function recovery after SCI. RESULTS: We found that the expression of PDGFD and PDGFB increased successively after SCI, and PDGFB was mainly secreted by astrocytes, while PDGFD was mainly secreted by macrophages/microglia and fibroblasts. In addition, in situ injection of exogenous PDGFB or PDGFD can lead to fibrosis in the uninjured spinal cord, while this profibrotic effect could be specifically blocked by the PDGFRß inhibitor SU16f. We then treated the mice after SCI with SU16f and found the reduction of fibrotic scar, the interruption of scar boundary and the inhibition of lesion and inflammation, which promoted axon regeneration and locomotor function recovery after SCI. CONCLUSIONS: Our study demonstrates that activation of PDGFRß pathway can directly induce fibrotic scar formation, and specific blocking of this pathway would contribute to the treatment of SCI.

Tau knockout exacerbates degeneration of parvalbumin-positive neurons in substantia nigra pars reticulata in Parkinson's disease-related α-synuclein A53T mice.

α-Synuclein (α-syn)-induced neurotoxicity has been generally accepted as a key step in the pathogenesis of Parkinson's disease (PD). Microtubule-associated protein tau, which is considered second only to α-syn, has been repeatedly linked with PD in association studies. However, the underlying interaction between these two PD-related proteins in vivo remains unclear. To investigate how the expression of tau affects α-syn-induced neurodegeneration in vivo, we generated triple transgenic mice that overexpressed α-syn A53T mutation in the midbrain dopaminergic neurons (mDANs) with different expression levels of tau. Here, we found that tau had no significant effect on the A53T α-syn-mediated mDANs degeneration. However, tau knockout could modestly promote the formation of α-syn aggregates, accelerate the severe and progressive degeneration of parvalbumin-positive (PV+) neurons in substantia nigra pars reticulata (SNR), accompanied with anxiety-like behavior in aged PD-related α-syn A53T mice. The mechanisms may be associated with A53T α-syn-mediated specifically successive impairment of N-methyl-d-aspartate receptor subunit 2B (NR2B), postsynaptic density-95 (PSD-95) and microtubule-associated protein 1A (MAP1A) in PV+ neurons. Our study indicates that MAP1A may play a beneficial role in preserving the survival of PV+ neurons, and that inhibition of the impairment of NR2B/PSD-95/MAP1A pathway, may be a novel and preferential option to ameliorate α-syn-induced neurodegeneration.

Transcranial direct current stimulation treated by multilead brain reflex instrument accelerates neural functional recovery in a rat model of stroke.

PURPOSE: Clinical research suggests that transcranial direct current stimulation (tDCS) at bilateral supraorbital foramen and inferior orbital rim and nose intersections may facilitate rehabilitation after stroke. However, the underlying neurobiological mechanisms of tDCS remain poorly understood, impeding its clinical application. Here, we investigated the effect of tDCS applied after stroke on neural cells. MATERIALS AND METHODS: Middle cerebral arterial occlusion (MCAO) reperfusion was induced in rats. Animals with comparable infarcts were randomly divided into MCAO group and MCAO + tDCS group. Recovery of neurological function was assessed behaviorally by modified neurological severity score (mNSS). Ischemic tissue damage verified histologically by TTC and HE staining. Immunohistochemical staining, real-time qPCR, and western blot were applied to determine the changes of neural cells in ischemic brains. RESULTS: The results reveal that tDCS treated by multilead brain reflex instrument can promote the recovery of neurological function, remarkably reduce cerebral infarct volume, promote brain tissue rehabilitation, and can effectively inhibit astrocytosis and enhance neuronal survival and synaptic function in ischemic brains. CONCULSIONS: Our study suggests that tDCS treated by multilead brain reflex instrument could be prospectively developed into a clinical treatment modality.

Tau haploinsufficiency causes prenatal loss of dopaminergic neurons in the ventral tegmental area and reduction of transcription factor orthodenticle homeobox 2 expression.

Homozygous tau knockout (Mapt-/-) mice develop age-dependent dopaminergic (DA) neuronal loss in the substantia nigra (SN) and ventral tegmental area (VTA), supporting an important function of tau in maintaining the survival of midbrain dopaminergic neurons (mDANs) during aging. However, it remains to be determined whether the microtubule-associated protein tau regulates the differentiation and survival of mDANs during embryonic developmental stages. Here, we show that tau haploinsufficiency in postnatal day 0 (P0) heterozygous (Mapt+/-) pups, but not a complete loss of tau in the Mapt-/- littermates, led to a significant reduction of DA neurons in the VTA. This selective loss of DA neurons correlated with a similar reduction in orthodenticle homeobox 2 (Otx2), which is restricted to VTA neurons at the postmitotic stage and selectively controls the neurogenesis and survival of specific neuronal subtypes of VTA. Moreover, the prenatal developmental cell death in the Mapt+/- VTA specifically increased, and the expression of microtubule-associated protein (MAP)-1A was significantly up-regulated in the P0 Mapt-/- , but not the Mapt+/- , pups. These results suggest that tau haploinsufficiency, without the compensation effect of MAP1A, induces reduction of Otx2 expression, increases prenatal cell death, and accordingly leads to selective loss of VTA DA neurons in the early postnatal stage. Our findings highlight the impact of tau haploinsufficiency on the survival of mDANs and indicate that tau may participate in midbrain development in a dose-dependent way.-Zheng, M., Jiao, L., Tang, X., Xiang, X., Wan, X., Yan, Y., Li, X., Zhang, G., Li, Y., Jiang, B., Cai, H., Lin, X. Tau haploinsufficiency causes prenatal loss of dopaminergic neurons in the ventral tegmental area and reduction of transcription factor orthodenticle homeobox 2 expression.

Transplantation of bone marrow stromal stem cells overexpressing tropomyosin receptor kinase A for peripheral nerve repair.

BACKGROUND AIMS: Previously we reported that overexpression of tropomyosin receptor kinase A (TrkA) could improve the survival and Schwann-like cell differentiation of bone marrow stromal stem cells (BMSCs) in nerve grafts for bridging rat sciatic nerve defects. The aim of this study was to investigate how TrkA affects the efficacy of BMSCs transplantation on peripheral nerve regeneration and functional recovery. METHODS: Rat BMSCs were infected with recombinant lentiviruses to construct TrkA-overexpressing BMSCs and TrkA-shRNA-expressing BMSCs, which were then seeded in acellular nerve allografts for bridging 10-mm rat sciatic nerve defects. RESULTS: At 8 weeks post-transplantation, compared with Vector and Control BMSCs-laden groups, TrkA-overexpressing BMSCs-laden group demonstrated obviously improved axon growth, such as significantly higher expression of myelin basic protein and superior results of myelinated fiber density, axon diameter and myelin sheaths thickness. In accordance with this increased nerve regeneration, the animals of TrkA-overexpressing BMSCs-laden group showed significantly better restoration of sciatic nerve function, manifested as greater sciatic function index value and superior electrophysiological parameters including shorter onset latency and higher peak amplitude of compound motor action potentials and faster nerve conduction velocity. However, these beneficial effects could be reversed in TrkA-shRNA-expressing BMSCs-laden group, which showed much fewer and smaller axons with thinner myelin sheaths and correspondingly poor functional recovery. CONCLUSIONS: These results demonstrated that TrkA may regulate the regenerative potential of BMSCs in nerve grafts, and TrkA overexpression can enhance the efficacy of BMSCs on peripheral nerve regeneration and functional recovery, which may help establish novel strategies for repairing peripheral nerve injuries.

Overexpression of tropomyosin receptor kinase A improves the survival and Schwann-like cell differentiation of bone marrow stromal cells in nerve grafts for bridging rat sciatic nerve defects.

BACKGROUND AIMS: Bone marrow stromal cells (BMSCs) can differentiate into Schwann-like cells in vivo and effectively promote nerve regeneration and functional recovery as the seed cells for peripheral nerve repair. However, the survival rate and neural differentiation rate of the transplanted BMSCs are very low, which would limit their efficacy. METHODS: In this work, rat BMSCs were infected by recombinant lentiviruses to construct tropomyosin receptor kinase A (TrkA)-overexpressing BMSCs and TrkA-shRNA-expressing BMSCs, which were then used in transplantation for rat sciatic nerve defects. RESULTS: We showed that lentivirus-mediated overexpression of TrkA in BMSCs can promote cell survival and protect against serum-starve-induced apoptosis in vitro. At 8 weeks after transplantation, the Schwann-like differentiated ratio of the existing implanted cells had reached 74.8 ± 1.6% in TrkA-overexpressing BMSCs-laden nerve grafts, while 40.7 ± 2.3% and 42.3 ± 1.5% in vector and control BMSCs-laden nerve grafts, but only 8.2 ± 1.8% in TrkA-shRNA-expressing BMSCs-laden nerve grafts. The cell apoptosis ratio of the existing implanted cells in TrkA-overexpressing BMSCs-laden nerve grafts was 16.5 ± 1.2%, while 33.9 ± 1.9% and 42.6 ± 2.9% in vector and control BMSCs-laden nerve grafts, but 87.2 ± 2.5% in TrkA-shRNA-expressing BMSCs-laden nerve grafts. CONCLUSIONS: These results demonstrate that TrkA overexpression can improve the survival and Schwann-like cell differentiation of BMSCs and prevent cell death in nerve grafts, which may have potential implication in advancing cell transplantation for peripheral nerve repair.

Effect of Myelin Debris on the Phenotypic Transformation of Astrocytes after Spinal Cord Injury in Rats.

After spinal cord injury (SCI), the accumulation of myelin debris can serve as proinflammatory agents, hindering axon regrowth and exacerbating damage. While astrocytes have been implicated in the phagocytosis of myelin debris, the impact of this process on the phenotypic transformation of astrocytes and their characteristics following SCI in rats is not well understood. Here, we demonstrated that the conditioned medium of myelin debris can trigger apoptosis in rat primary astrocytes in vitro. Using a compressional SCI model in rats, we observed that astrocytes can engulf myelin debris through ATP-binding cassette transporter sub-family A member 1 (ABCA1), and these engulfed cells tend to transform into A1 astrocytes, as indicated by C3 expression. At 4 days post-injury (dpi), astrocytes rapidly transitioned into A1 astrocytes and maintained this phenotype from 4 to 28 dpi, while A2 astrocytes, characterized by S100, were only detected at 14 and 28 dpi. Reactive astrocytes, identified by Nestin, emerged at 4 and 7 dpi, whereas scar-forming astrocytes, marked by N-cadherin, were evident at 14 and 28 dpi. This study illustrates the distribution patterns of astrocyte subtypes and the potential interplay between astrocytes and myelin debris after SCI in rats. We emphasize that myelin debris can induce astrocyte apoptosis in vitro and promote the transformation of astrocytes into A1 astrocytes in vivo. These two classification methods are not mutually exclusive, but rather complementary.

hBcl2 overexpression in BMSCs enhances resistance to myelin debris-induced apoptosis and facilitates neuroprotection after spinal cord injury in rats.

After spinal cord injury (SCI), the accumulation of myelin debris at the lesion exacerbates cell death and hinders axonal regeneration. Transplanted bone marrow mesenchymal stem cells (BMSCs) have been proven to be beneficial for SCI repair, but they are susceptible to apoptosis. It remains unclear whether this apoptotic process is influenced by myelin debris. Here, we constructed rat BMSCs overexpressing human B-cell lymphoma 2 (hBcl2) alone (hBcl2 group), BMSCs overexpressing hBcl2 with an endoplasmic reticulum-anchored segment (hBcl2-cb) (cb group), and a negative control group (NC group) for transplantation in this study. Immunocytochemistry staining validated the successful expression of hBcl2 in BMSCs within the hBcl2 group and cb group. All BMSCs from each group exhibited the ability to phagocytize myelin debris. Nevertheless, only BMSCs derived from the hBcl2 group exhibited heightened resistance to apoptosis and maintained prolonged viability for up to 5 days when exposed to myelin debris. Notably, overexpression of hBcl2 protein, rather than its endoplasmic reticulum-anchored counterpart, significantly enhanced the resistance of BMSCs against myelin debris-induced apoptosis. This process appeared to be associated with the efficient degradation of myelin debris through the Lamp1+ lysosomal pathway in the hBcl2 group. In vivo, the hBcl2 group exhibited significantly higher numbers of surviving cells and fewer apoptotic BMSCs compared to the cb and NC groups following transplantation. Furthermore, the hBcl2 group displayed reduced GFAP+ glial scarring and greater preservation of NF200+ axons in the lesions of SCI rats. Our results suggest that myelin debris triggers apoptosis in transplanted BMSCs, potentially elucidating the low survival rate of these cells after SCI. Consequently, the survival rate of transplanted BMSCs is improved by hBcl2 overexpression, leading to enhanced preservation of axons within the injured spinal cord.

Tocilizumab promotes repair of spinal cord injury by facilitating the restoration of tight junctions between vascular endothelial cells.

BACKGROUND: Our previous study demonstrated that M1 macrophages could impair tight junctions (TJs) between vascular endothelial cells by secreting interleukin-6 (IL-6) after spinal cord injury (SCI). Tocilizumab, as a humanized IL-6 receptor (IL-6R) monoclonal antibody approved for the clinic, has been applied in the treatment of neurological diseases in recent years, but the treatment effect of Tocilizumab on the TJs restoration of the blood-spinal cord barrier (BSCB) after SCI remains unclear. This study aimed to explore the effect of Tocilizumab on the restoration of TJs between vascular endothelial cells and axon regeneration after SCI. METHODS: In this study, the mouse complete spinal cord crush injury model was used, and Tocilizumab was continuously injected intrathecally until the day of sample collection. A PBS injection in the same location was included as a control. At 14 days postinjury (dpi) and 28 dpi, spinal cord tissue sections were examined via tissue immunofluorescence. The Basso Mouse Scale (BMS) scores and footprint analysis were used to verify the effect of Tocilizumab on the recovery of motor function in mice after SCI. RESULTS: We demonstrated that depletion of macrophages has no effect on axon regeneration and motor functional recovery after SCI, but mice subjected to Tocilizumab showed a significant increase in axon regeneration and a better recovery in motor function during the chronic phase after SCI. Moreover, our study demonstrated that at 14 and 28 dpi, the expression of claudin-5 (CLDN5) and zonula occludens-1 (ZO-1) between vascular endothelial cells was significantly increased and the leakage of BSCB was significantly reduced in the injured core after daily intrathecal injection of Tocilizumab. Notably, the infiltration of CD68+ macrophages/microglia and the formation of fibrotic scar were decreased in the injured core after Tocilizumab treatment. Tocilizumab treatment could effectively reduce the IL-6 expression in macrophages in the injured core. CONCLUSION: The application of Tocilizumab to antagonize IL-6R can effectively reduce the expression of IL-6 in macrophages and facilitate TJs restoration of the BSCB, which is beneficial for axon regeneration and motor functional recovery after SCI. Hence, Tocilizumab treatment is a potential therapeutic strategy for SCI.

Fingolimod (FTY720) Hinders Interferon-γ-Mediated Fibrotic Scar Formation and Facilitates Neurological Recovery After Spinal Cord Injury.

Following spinal cord injury (SCI), fibrotic scar inhibits axon regeneration and impairs neurological function recovery. It has been reported that T cell-derived interferon (IFN)-γ plays a pivotal role in promoting fibrotic scarring in neurodegenerative disease. However, the role of IFN-γ in fibrotic scar formation after SCI has not been declared. In this study, a spinal cord crush injury mouse was established. Western blot and immunofluorescence showed that IFN-γ was surrounded by fibroblasts at 3, 7, 14, and 28 days post-injury. Moreover, IFN-γ is mainly secreted by T cells after SCI. Further, in situ injection of IFN-γ into the normal spinal cord resulted in fibrotic scar formation and inflammation response at 7 days post-injection. After SCI, the intraperitoneal injection of fingolimod (FTY720), a sphingosine-1-phosphate receptor 1 (S1PR1) modulator and W146, an S1PR1 antagonist, significantly reduced T cell infiltration, attenuating fibrotic scarring via inhibiting IFN-γ/IFN-γR pathway, while in situ injection of IFN-γ diminished the effect of FTY720 on reducing fibrotic scarring. FTY720 treatment inhibited inflammation, decreased lesion size, and promoted neuroprotection and neurological recovery after SCI. These findings demonstrate that the inhibition of T cell-derived IFN-γ by FTY720 suppressed fibrotic scarring and contributed to neurological recovery after SCI.

Effect of sub-acute exposure to acrylamide on GABAergic neurons and astrocytes in weaning rat cerebellum.

Occupational exposure and experimental intoxication of acrylamide (ACR) can produce skeletal muscle weakness and ataxia. In this study, we tested whether ACR would affect cerebellar function through the regulation of gamma-aminobutyric acid (GABA) and glial fibrillary acidic protein (GFAP) expression in cerebellum. Weaning male Sprague-Dawley rats were gavaged with ACR (5, 15, 30 mg/kg, 5 days per week) or saline for 4 weeks. Effects of ACR on the cerebellum were observed. For the 5 mg/kg group, no obvious change was observed, whereas moderate and severe ataxia were observed in the 15 mg/kg and 30 mg/kg groups, respectively. For the 15 mg/kg and 30 mg/kg groups, cerebellum concentrations of glutamate and GABA were dose-dependently decreased and increased, respectively. Moreover, the expression of GABA, the GABAergic presynaptic marker glutamate acid decarboxylase-65 (GAD65) and GFAP were significantly increased in those 2 groups. The results suggested that weaning rats were sensitive to ACR and that the toxic effects of ACR on the cerebellum may be associated with the increased expression of GABA and reactive astrocytes hypertrophy.

CD146 is closely associated with the prognosis and molecular features of osteosarcoma: Guidance for personalized clinical treatment.

Background: Osteosarcoma (OSA), a focus for orthopedic surgeons, always results in severe death due to metastasis. CD146 is severely expressed in several tumors, indicating its potential as a biomarker for OSA. Method: Two OSA cohorts were enrolled in this study. A Therapeutically Applicable Research to Generate Effective Treatments-Osteosarcoma (TARGET-OS) cohort was used as a training cohort, and GSE21257 was used as the external validation cohort. The R package "limma" was used to discriminate the differentially expressed genes among CD146-high and CD146-low patients and was further annotated by the enriched signaling pathways. The R package MOVICS was used to evaluate immune infiltration and the response to chemotherapy and immunotherapy. All statistical analyses were performed by R version 4.0.2, and p < 0.05 was considered statistically significant. Result: CD146 plays an important role in promoting the progression, invasion, and metastasis of several tumors. In the current study, we first revealed an integrative unfavorable prognosis in patients with tumors (p < 0.01, HR: 1.10, 95% CI: 1.07-1.14). CD146 is tightly correlated with m5C RNA methylation modification genes in OSA. Furthermore, we revealed that CD146 acts as an oncogene in OSA patients and is linked to poor prognosis in both the TARGET-OS cohort (p = 0.019, HR: 2.61, 95% CI: 1.171-5.834) and the GSE21257 cohort (p = 0.005, HR: 3.61, 95% CI: 1.474-8.855), with a total of 137 patients, regardless of whether they were adjusted for clinical pathological features. Highly-expressed CD146 impacts the signaling pathways of cytokine‒cytokine receptor interactions and is associated with the high infiltration of immunocytes. Moreover, patients with high CD146 expression were more likely to be sensitive to anti-PD-1 immunotherapy, while patients with low expression of CD146 were more likely to be sensitive to cisplatin and doxorubicin chemotherapy. Conclusion: Overall, CD146 is an independent prognostic factor for OSA patients and can help doctors select clinical treatment strategies.

D-4F, an apolipoprotein A-I mimetic, promotes the clearance of myelin debris and the reduction of foamy macrophages after spinal cord injury.

After spinal cord injury (SCI), a large number of blood-derived macrophages infiltrate the lesion site and phagocytose myelin debris to become foamy macrophages, which leads to chronic inflammation. The drug D-4F, an apolipoprotein A-I peptidomimetic made of D-amino acids, has been reported to promote the lipid metabolism of foamy macrophages in atherosclerosis. However, the role and mechanism of D-4F in SCI are still unclear. In this study, we found that D-4F can promote the removal of myelin debris, reduce the formation of foamy macrophages in the lesion core and promote neuroprotection and recovery of motor function after SCI. These beneficial functions of D-4F may be related to its ability to upregulate the expression of ATP-binding cassette transporter A1 (ABCA1), the main transporter that mediates lipid efflux in foamy macrophages because inhibiting the activity of ABCA1 can reverse the effect of D-4F in vitro. In conclusion, D-4F may be a promising candidate for treating SCI by promoting the clearance of myelin debris by foamy macrophages via the ABCA1 pathway.

M1 macrophages impair tight junctions between endothelial cells after spinal cord injury.

After spinal cord injury (SCI), endogenous angiogenesis occurs in the injury core, unexpectedly accompanied by continuous leakage of the blood-spinal cord barrier (BSCB), which may be caused by destruction of the tight junctions (TJs) between vascular endothelial cells-an important structure of the BSCB. Blood-derived macrophages infiltrate into the spinal cord, aggregate to the injury core and then polarize toward M1/M2 phenotypes after SCI. However, the effect of macrophages with different polarizations on the TJs between vascular endothelial cells remains unclear. Here, we demonstrated that from 7 days postinjury (dpi) to 28 dpi, accompanied by the aggregation of macrophages, the expression of claudin-5 (CLN-5) and zonula occludens-1 (ZO-1) in vascular endothelial cells in the injury core was significantly decreased in comparison to that in normal spinal cord tissue and in the penumbra. Moreover, the leakage of the BSCB was severe in the injury core, as demonstrated by FITC-dextran perfusion. Notably, our study demonstrated that depletion of macrophages facilitated the restoration of TJs between vascular endothelial cells and decreased the leakage of BSCB in the injury core after SCI. Furthermore, we confirmed that the endothelial TJs could be impaired by M1 macrophages through secreting IL-6 in vitro, leading to an increased permeability of endothelial cells, but it was not significantly affected by M0 and M2 macrophages. These results indicated that the TJs between vascular endothelial cells were impaired by M1 macrophages in the injury core, potentially resulting in continuous leakage of the BSCB after SCI. Preventing M1 polarization of macrophages or blocking IL-6 in the injury core may promote restoration of the BSCB, thus accelerating functional recovery after SCI.

M1-type microglia can induce astrocytes to deposit chondroitin sulfate proteoglycan after spinal cord injury.

After spinal cord injury (SCI), astrocytes gradually migrate to and surround the lesion, depositing chondroitin sulfate proteoglycan-rich extracellular matrix and forming astrocytic scar, which limits the spread of inflammation but hinders axon regeneration. Meanwhile, microglia gradually accumulate at the lesion border to form microglial scar and can polarize to generate a pro-inflammatory M1 phenotype or an anti-inflammatory M2 phenotype. However, the effect of microglia polarization on astrocytes is unclear. Here, we found that both microglia (CX3CR1+) and astrocytes (GFAP+) gathered at the lesion border at 14 days post-injury (dpi). The microglia accumulated along the inner border of and in direct contact with the astrocytes. M1-type microglia (iNOS+CX3CR1+) were primarily observed at 3 and 7 dpi, while M2-type microglia (Arg1+CX3CR1+) were present at larger numbers at 7 and 14 dpi. Transforming growth factor-ß1 (TGFß1) was highly expressed in M1 microglia in vitro, consistent with strong expression of TGFß1 by microglia in vivo at 3 and 7 dpi, when they primarily exhibited an M1 phenotype. Furthermore, conditioned media from M1-type microglia induced astrocytes to secrete chondroitin sulfate proteoglycan in vitro. This effect was eliminated by knocking down sex-determining region Y-box 9 (SOX9) in astrocytes and could not be reversed by treatment with TGFß1. Taken together, our results suggest that microglia undergo M1 polarization and express high levels of TGFß1 at 3 and 7 dpi, and that M1-type microglia induce astrocytes to deposit chondroitin sulfate proteoglycan via the TGFß1/SOX9 pathway. The study was approved by the Institutional Animal Care and Use Committee of Anhui Medical University, China (approval No. LLSC20160052) on March 1, 2016.

Imatinib inhibits pericyte-fibroblast transition and inflammation and promotes axon regeneration by blocking the PDGF-BB/PDGFRß pathway in spinal cord injury.

BACKGROUND: Fibrotic scar formation and inflammation are characteristic pathologies of spinal cord injury (SCI) in the injured core, which has been widely regarded as the main barrier to axonal regeneration resulting in permanent functional recovery failure. Pericytes were shown to be the main source of fibroblasts that form fibrotic scar. However, the mechanism of pericyte-fibroblast transition after SCI remains elusive. METHODS: Fibrotic scarring and microvessels were assessed using immunofluorescence staining after establishing a crush SCI model. To study the process of pericyte-fibroblast transition, we analyzed pericyte marker and fibroblast marker expression using immunofluorescence. The distribution and cellular origin of platelet-derived growth factor (PDGF)-BB were examined with immunofluorescence. Pericyte-fibroblast transition was detected with immunohistochemistry and Western blot assays after PDGF-BB knockdown and blocking PDGF-BB/PDGFRß signaling in vitro. Intrathecal injection of imatinib was used to selectively inhibit PDGF-BB/PDGFRß signaling. The Basso mouse scale score and footprint analysis were performed to assess functional recovery. Subsequently, axonal regeneration, fibrotic scarring, fibroblast population, proliferation and apoptosis of PDGFRß+ cells, microvessel leakage, and the inflammatory response were assessed with immunofluorescence. RESULTS: PDGFRß+ pericytes detached from the blood vessel wall and transitioned into fibroblasts to form fibrotic scar after SCI. PDGF-BB was mainly distributed in the periphery of the injured core, and microvascular endothelial cells were one of the sources of PDGF-BB in the acute phase. Microvascular endothelial cells induced pericyte-fibroblast transition through the PDGF-BB/PDGFRß signaling pathway in vitro. Pharmacologically blocking the PDGF-BB/PDGFRß pathway promoted motor function recovery and axonal regeneration and inhibited fibrotic scar formation. After fibrotic scar formation, blocking the PDGFRß receptor inhibited proliferation and promoted apoptosis of PDGFRß+ cells. Imatinib did not alter pericyte coverage on microvessels, while microvessel leakage and inflammation were significantly decreased after imatinib treatment. CONCLUSIONS: We reveal that the crosstalk between microvascular endothelial cells and pericytes promotes pericyte-fibroblast transition through the PDGF-BB/PDGFRß signaling pathway. Our finding suggests that blocking the PDGF-BB/PDGFRß signaling pathway with imatinib contributes to functional recovery, fibrotic scarring, and inflammatory attenuation after SCI and provides a potential target for the treatment of SCI.

Toxicological effects of acrylamide on the reproductive system of weaning male rats.

It has been reported that acrylamide can be detected in starchy food treated by high temperature (120 °C). People could be exposed to acrylamide in factory, laboratory, or even in daily life via diet and drinking water. Recently, the toxicity of acrylamide receives more attention. In addition to the neurotoxicity in humans, other toxic effects of acrylamide are worth further investigation. In this study, we investigated whether acrylamide affected the male reproductive system using high-performance liquid chromatography. In this study, the reproductive toxicity of acrylamide was observed in 3-week-old weaning male Sprague-Dawley rats treated with acrylamide at various doses (0, 5, 15 or 30 mg/kg/day). The results showed that food availability and reproductive organ indexes of the weaning male rats decreased. Levels of follicle-stimulating hormone and testosterone in serum increased while luteinizing hormone in serum decreased. The histopathological lesions and abnormal sperms presented in weaning rats after acrylamide treatment. The results suggested that there is a toxicological effect of acrylamide on the reproductive system of weaning male rats. Based on the findings above, we suggested that more attention should be paid to the toxicological study of acrylamide on weaning male rats or human beings, rather than just on adult male animals.

Tau Knockout and α-Synuclein A53T Synergy Modulated Parvalbumin-Positive Neurons Degeneration Staging in Substantia Nigra Pars Reticulata of Parkinson's Disease-Liked Model.

The loss of parvalbumin-positive (PV+) neurons in the substantia nigra pars reticulata (SNR) was observed in patients with end-stage Parkinson's disease (PD) and our previously constructed old-aged Pitx3-A53Tα-Syn × Tau-/- triple transgenic mice model of PD. The aim of this study was to examine the progress of PV+ neurons loss. We demonstrated that, as compared with non-transgenic (nTg) mice, the accumulation of α-synuclein in the SNR of aged Pitx3-A53Tα-Syn × Tau-/- mice was increased obviously, which was accompanied by the considerable degeneration of PV+ neurons and the massive generation of apoptotic NeuN+TUNEL+ co-staining neurons. Interestingly, PV was not costained with TUNEL, a marker of apoptosis. PV+ neurons in the SNR may undergo a transitional stage from decreased expression of PV to increased expression of NeuN and then to TUNEL expression. In addition, the degeneration of PV+ neurons and the expression of NeuN were rarely observed in the SNR of nTg and the other triple transgenic mice. Hence, we propose that Tau knockout and α-syn A53T synergy modulate PV+ neurons degeneration staging in the SNR of aged PD-liked mice model, and NeuN may be suited for an indicator that suggests degeneration of SNR PV+ neurons. However, the molecular mechanism needs to be further investigated.

Fascin-1 is Highly Expressed Specifically in Microglia After Spinal Cord Injury and Regulates Microglial Migration.

Recent research indicates that after spinal cord injury (SCI), microglia accumulate at the borders of lesions between astrocytic and fibrotic scars and perform inflammation-limiting and neuroprotective functions, however, the mechanism of microglial migration remains unclear. Fascin-1 is a key actin-bundling protein that regulates cell migration, invasion and adhesion, but its role during SCI has not been reported. Here, we found that at 7-14 days after SCI in mice, Fascin-1 is significantly upregulated, mainly distributed around the lesion, and specifically expressed in CX3CR1-positive microglia. However, Fascin-1 is not expressed in GFAP-positive astrocytes, NeuN-positive neurons, NG2-positive cells, PDGFRß-positive cells, or blood-derived Mac2-positive macrophages infiltrating into the lesion core. The expression of Fascin-1 is correspondingly decreased after microglia are specifically depleted in the injured spinal cord by the colony-stimulating factor 1 receptor (CSF1R) inhibitor PLX5622. The upregulation of Fascin-1 expression is observed when microglia are activated by myelin debris in vitro, and microglial migration is prominently increased. The inhibition of Fascin-1 expression using small interfering RNA (siRNA) markedly suppresses the migration of microglia, but this effect can be reversed by treatment with myelin. The M1/M2-like polarization of microglia does not affect the expression of Fascin-1. Together, our results suggest that Fascin-1 is highly expressed specifically in microglia after SCI and can play an important role in the migration of microglia and the formation of microglial scars. Hence, the elucidation of this mechanism will provide novel therapeutic targets for the treatment of SCI.