Chronic nSMase inhibition suppresses neuronal exosome spreading and sex-specifically attenuates amyloid pathology in APP knock-in Alzheimer's disease mice.

Female biased pathology and cognitive decline in Alzheimer's disease (AD) have been consistently observed with unclear underlying mechanisms. Although brain sphingolipid ceramide is elevated in AD patients, whether and how ceramide may contribute to sex-specific differences in amyloid pathology is unknown. Here we investigated the sex-specific impact of chronic pharmacological inhibition of neutral sphingomyelinase (nSMase), a key enzyme responsible for ceramide metabolism, on in vivo neuron-derived exosome dynamics, Aß plaque load, and cognitive function in the APPNL-F/NL-F knock-in (APP NL-F) AD mouse model. Our results found sex-specific increase of cortical C20:0 ceramide and brain exosome levels only in APP NL-F but not in age-matched WT mice. Although nSMase inhibition similarly blocks exosome spreading in male and female mice, significantly reduced amyloid pathology was mostly observed in cortex and hippocampus of female APP NL-F mice with only modest effect found on male APP NL-F mice. Consistently, T maze test to examine spatial working memory revealed a female-specific reduction in spontaneous alternation rate in APP NL-F mice, which was fully reversed with chronic nSMase inhibition. Together, our results suggest that disease induced changes in ceramide and exosome pathways contribute to the progression of female-specific amyloid pathology in APP NL-F AD models.

Improving the tumor selectivity of T cell engagers by logic-gated dual tumor-targeting.

Targeting single tumor antigens makes it difficult to provide sufficient tumor selectivity for T cell engagers (TCEs), leading to undesirable toxicity and even treatment failure, which is particularly serious in solid tumors. Here, we designed novel trispecific TCEs (TriTCEs) to improve the tumor selectivity of TCEs by logic-gated dual tumor-targeting. TriTCE can effectively redirect and activate T cells to kill tumor cells (∼18 pM EC50) by inducing the aggregation of dual tumor antigens, which was ∼70- or 750- fold more effective than the single tumor-targeted isotype controls, respectively. Further in vivo experiments indicated that TriTCE has the ability to accumulate in tumor tissue and can induce circulating T cells to infiltrate into tumor sites. Hence, TriTCE showed a stronger tumor growth inhibition ability and significantly prolonged the survival time of the mice. Finally, we revealed that this concept of logic-gated dual tumor-targeted TriTCE can be applied to target different tumor antigens. Cumulatively, we reported novel dual tumor-targeted TriTCEs that can mediate a robust T cell response by simultaneous recognition of dual tumor antigens at the same cell surface. TriTCEs allow better selective T cell activity on tumor cells, resulting in safer TCE treatment.

p14ARF ameliorates inflammation and airway remodeling in nitric acid aerosol inhalation-induced bronchiolitis obliterans.

BACKGROUND: To investigate the protective effect of p14ARF in a nitric acid (NA) aerosol inhalation-induced bronchiolitis obliterans (BO) mouse model and its potential regulatory mechanism. METHODS: A BO mouse model was established by NA aerosol inhalation. The expressions of p14ARF, phosphatidylinositol-3-kinase (PI3K), and protein kinase B (AKT) were detected by quantitative reverse transcription PCR (qRT-PCR) and western blot (WB). Hematoxylin (HE) staining, Masson staining, and periodic acid-Schiff (PAS) staining observed pulmonary histological changes. TdT-mediated dUTP nick end labeling (TUNEL) staining detected pulmonary cell apoptosis, and enzyme-linked immunosorbent assay (ELISA) measured matrix metalloproteinase-2 (MMP-2), MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), interleukon-6 (IL-6), and transforminh growth factor-ß (TGF-ß) levels in lung tissue and bronchoalveolar lavage fluid (BALF). RESULTS: The expressions of p14ARF, PI3K, and AKT showed a time gradient change, with a decrease trend (*P < 0.05 and **P < 0.01). Severe inflammatory infiltration and tracheal fibrosis were found in lung tissue in the modeling group (BO group) compared with the control group (Con group). The pH, PaO2, and PaO2/FiO2 values significantly reduced, while the PaCO2 value and the number of TUNEL-positive cells increased in BO group (P < 0.05). In addition, MMP-2, MMP-9, IL-6, and TGF-ß levels remarkably increased, with an increase in the number of white blood cells, neutrophils, and lymphocytes in BO group (P < 0.05). Furthermore, p14ARF up-regulation reversed the trend of the aforementioned indexes in BO mice. CONCLUSIONS: p14ARF ameliorated the inflammatory response and airway remodeling in a BO mouse model via the PI3K/AKT pathway.

5-HMF attenuates inflammation and demyelination in experimental autoimmune encephalomyelitis mice by inhibiting the MIF-CD74 interaction.

The neuroprotective role of 5-hydroxymethyl-2-furfural (5-HMF) has been demonstrated in a variety of neurological diseases. The aim of this study is to investigate the effect of 5-HMF on multiple sclerosis (MS). IFN-γ-stimulated murine microglia (BV2 cells) are considered a cell model of MS. With 5-HMF treatment, microglial M1/2 polarization and cytokine levels are detected. The interaction of 5-HMF with migration inhibitory factor (MIF) is predicted using online databases. The experimental autoimmune encephalomyelitis (EAE) mouse model is established, followed by a 5-HMF injection. The results show that 5-HMF facilitates IFN-γ-stimulated microglial M2 polarization and attenuates the inflammatory response. According to the network pharmacology and molecular docking results, 5-HMF has a binding site for MIF. Further results show that blocking MIF activity or silencing CD74 enhances microglial M2 polarization, reduces inflammatory activity, and prevents ERK1/2 phosphorylation. 5-HMF inhibits the MIF-CD74 interaction by binding to MIF, thereby inhibiting microglial M1 polarization and enhancing the anti-inflammatory response. 5-HMF ameliorates EAE, inflammation, and demyelination in vivo. In conclusion, our research indicates that 5-HMF promotes microglial M2 polarization by inhibiting the MIF-CD74 interaction, thereby attenuating inflammation and demyelination in EAE mice.

MiR-140 suppresses airway inflammation and inhibits bronchial epithelial cell apoptosis in asthma by targeting GSK3ß.

AIM OF THE STUDY: Asthma is a common and complex chronic inflammatory disease induced by genetic and environmental factors that affects the airways of the lungs. MicroRNAs (miRNAs) are key regulators of various cellular processes and have been shown to be critically involved in asthma progression. The objective of our study was to clarify the function and molecular mechanism of miR-140 in the progression of asthma. MATERIALS AND METHODS: MiR-140 expression was evaluated using RT-qPCR. Pathological changes in the lung tissue were confirmed using HE and PAS staining. The levels of IL-5, TGF-ß1, and IL-13 in the serum or bronchioalveolar lavage fluid were detected with an ELISA. Cellular apoptosis was measured using a TUNEL assay. The levels of Bax, Bcl-2, Cleaved caspase-3, and glycogen synthase kinase-3ß (GSK-3ß) were verified with a western blot. GSK3ß expression was also confirmed by immunohistochemistry. The binding ability between miR-140 and GSK3ß was confirmed using a luciferase reporter assay, RNA immunoprecipitation (RIP) assay and Pull-down assay. RESULTS: MiR-140 was markedly downregulated in asthmatic mice. Additionally, miR-140 weakened airway inflammation and bronchial epithelial cell apoptosis in asthmatic mice. Further experiments revealed that miR-140 negatively regulated GSK3ß expression and could bind to GSK3ß in asthma. Finally, rescue assays demonstrated that GSK3ß overexpression rescued the effects of miR-140 on asthma progression. CONCLUSION: MiR-140 targeted GSK3ß to suppress airway inflammation and inhibit bronchial epithelial cell apoptosis in asthma.

Intracortical astrocyte subpopulations defined by astrocyte reporter Mice in the adult brain.

Although historically regarded as a homogeneous cell population, astrocytes in different brain regions exhibit differences in their physiological properties, such as gap-junction coupling, glutamate uptake dynamics, and intracellular Ca2+ response. Recent in vivo RNA profiles have further demonstrated the molecular heterogeneity of astrocytes in the adult CNS. Astrocyte heterogeneity exists not only inter-regionally but also intra-regionally. Despite the characteristic laminal organization of cortical layers and multiple sources of radial glia progenitors for (astro)gliogenesis, the molecular profile and functional properties of astroglial subpopulations in the adult cerebral cortex remain essentially undefined. Using two astrocyte reporter mouse lines: eaat2-tdTomato and Bac aldh1l1-eGFP, we identified tdT- eGFP+ , tdTlow eGFP+ , and tdThigh eGFP+ astroglial subpopulations (in an approximate 1:7:2 ratio) within the cortex. The tdT- eGFP+ astrocyte population is selectively localized at layers I-II and exhibits increased resting membrane potential and membrane resistance but reduced functional expression of the potassium channel Kir4.1. We also isolated individual astrocyte subpopulations through fluorescence activated cell sorting (FACS) and examined their transcriptome differences by RNA-seq. We found that the whole-genome transcriptional profiles of tdT- eGFP+ astrocytes are drastically different from that of tdTlow eGFP+ and tdThigh eGFP+ astrocytes. Particularly, elevated levels of several nonastrocyte genes that are typically specific to other glial cells, such as mog, mobp, Iba1, and pdgfrα, are observed in tdT- eGFP+ astrocytes, suggesting a less-specific molecular identity of these astrocytes. Overall, our study has unveiled molecular differences between adult cortical astroglial subpopulations, shedding new light on understanding their unique functions in the adult cortex.

Conditioned Medium from the Stem Cells of Human Exfoliated Deciduous Teeth Ameliorates Experimental Autoimmune Encephalomyelitis.

Multiple sclerosis (MS) is a major neuroinflammatory demyelinating disease of the CNS. Current MS treatments, including immunomodulators and immunosuppressants, do not result in complete remission. Stem cells from human exfoliated deciduous teeth (SHEDs) are mesenchymal stem cells derived from dental pulp. Both SHED and SHED-conditioned medium (SHED-CM) exhibit immunomodulatory and regenerative activities and have the potential to treat various diseases. In this study, we investigated the efficacy of SHED-CM in treating experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. EAE mice treated with a single injection of SHED-CM exhibited significantly improved disease scores, reduced demyelination and axonal injury, and reduced inflammatory cell infiltration and proinflammatory cytokine expression in the spinal cord, which was associated with a shift in the microglia/macrophage phenotype from M1 to M2. SHED-CM also inhibited the proliferation of myelin oligodendrocyte glycoprotein-specific CD4(+) T cells, as well as their production of proinflammatory cytokines in vitro. Treatment of EAE mice with the secreted ectodomain of sialic acid-binding Ig-like lectin-9, a major component of SHED-CM, recapitulated the effects of SHED-CM treatment. Our data suggest that SHED-CM and secreted ectodomain of sialic acid-binding Ig-like lectin-9 may be novel therapeutic treatments for autoimmune diseases, such as MS.

Sortase A-Generated Highly Potent Anti-CD20-MMAE Conjugates for Efficient Elimination of B-Lineage Lymphomas.

Antibody-drug conjugate (ADC) targeting antigens expressed on the surface of tumor cells are an effective approach for delivering drugs into the cells via antigen-mediated endocytosis. One of the well-known tumor antigens, the CD20 of B-lymphocyte, has long been suggested to be noninternalizing epitope, and is thus not considered a desirable target for ADCs. Here, sortase A (srtA)-mediated transpeptidation is used to specifically conjugate triple glycine-modified monomethyl auristatin E (MMAE), a highly toxic antimitotic agent, to anti-CD20 ofatumumab (OFA) equipped with a short C-terminal LPETG (5 amino acids) tag at heavy chain (HL), which generates ADCs that show extremely strong potency in killing CD20 positive cancer cells. One of the srtA-generated ADCs with a cleavable dipeptide linker (valine-citrulline, vc), OFA-HL-vcMMAE, shows IC50 values ranging from 5 pg mL-1 to 4.1 ng mL-1 against CD20+ lymphoma cells. Confocal laser scanning microscopy confirms that OFA-HL-vcMMAE internalization by Ramos cells is significantly improved compared to OFA alone, consistent with the high antitumor activity of the new ADC. OFA-HL-vcMMAE, at 5 mg kg-1 dose, is able to eliminate tumors with mean volume ≈400 mm3 while no obvious drug-related toxicity is observed. The results show that srtA-generated OFA-MMAE conjugate system provides a viable strategy for targeting CD20+ B lineage lymphomas.

A Versatile Chemo-Enzymatic Conjugation Approach Yields Homogeneous and Highly Potent Antibody-Drug Conjugates.

The therapeutic efficacy of antibodies can be successfully improved through targeted delivery of potent cytotoxic drugs in the form of antibody-drug conjugates. However, conventional conjugation strategies lead to heterogeneous conjugates with undefined stoichiometry and sites, even with considerable batch-to-batch variability. In this study, we have developed a chemo-enzymatic strategy by equipping the C-terminus of anti-CD20 ofatumumab with a click handle using Sortase A, followed by ligation of the payload based on a strain-promoted azide-alkyne cycloaddition to produce homogeneous conjugates. The resulting antibody-drug conjugates fully retained their antigen binding capability and proved to be internalized and trafficked to the lysosome, which released the payload with a favorable efficacy in vitro and in vivo. Thus, this reported method is a versatile tool with maximum flexibility for development of antibody-drug conjugates and protein modification.

[ORMDL3 polymorphisms and their relationship with OPN and TGF-ß1 levels in children with asthma in Hunan, China: an analysis of 98 cases].

OBJECTIVE: To investigate ORMDL3 polymorphisms in children with asthma in Hunan, China, and to determine the relationship between ORMDL3 polymorphisms and serum osteopontin (OPN) and transforming growth factor-ß1 (TGF-ß1) levels. METHODS: Peripheral blood samples were collected in children with asthma (n=98; astma group) or without asthma (n=30; control group) from Hunan, China. The asthma group was subdivided into atopic (n=62) and non-atopic (n=36) subgroups. Single nucleotide polymorphism (SNP) analysis was performed, and serum OPN and TGF-ß1 levels were measured. RESULTS: There were no significant differences in genotype and allele frequencies of rs7216389 of the ORMDL3 gene between the asthma and control groups. The serum level of OPN in the asthma group was significantly higher than in the control group (P<0.05). Both the atopic and non-atopic subgroups showed increased serum levels of OPN compared with the control group (P<0.05). The serum level of TGF-ß1 in the atopic subgroup was significantly higher than in the control group (P<0.05). The serum levels of OPN and TGF-ß1 showed no significant differences in asthmatic children with different genotypes. The serum levels of OPN and TGF-ß1 were in a positive linear correlation in the asthma group (r=0.620; P<0.01) and its two subgroups (r=0.734, 0.649 respectively; P<0.01). CONCLUSIONS: In children from Hunan, China, the SNP (rs7216389) of ORMDL3 is not related to asthma susceptibility. OPN and TGF-ß1 may be involved in the development of asthma, and they are in a positive linear correlation. The SNP (rs7216389) of ORMDL3 does not influence the expression of OPN and TGF-ß1, suggesting that it may not be associated with airway remodeling.

Midkine inhibits inducible regulatory T cell differentiation by suppressing the development of tolerogenic dendritic cells.

Midkine (MK), a heparin-binding growth factor, reportedly contributes to inflammatory diseases, including Crohn's disease and rheumatoid arthritis. We previously showed that MK aggravates experimental autoimmune encephalomyelitis (EAE) by decreasing regulatory CD4(+)CD25(+)Foxp3(+) T cells (Tregs), a population that regulates the development of autoimmune responses, although the precise mechanism remains uncertain. In this article, we show that MK produced in inflammatory conditions suppresses the development of tolerogenic dendritic cells (DCregs), which drive the development of inducible Treg. MK suppressed DCreg-mediated expansion of the CD4(+)CD25(+)Foxp3(+) Treg population. DCregs expressed significantly higher levels of CD45RB and produced significantly less IL-12 compared with conventional dendritic cells. However, MK downregulated CD45RB expression and induced IL-12 production by reducing phosphorylated STAT3 levels via src homology region 2 domain-containing phosphatase-2 in DCreg. Inhibiting MK activity with anti-MK RNA aptamers, which bind to the targeted protein to suppress the function of the protein, increased the numbers of CD11c(low)CD45RB(+) dendritic cells and Tregs in the draining lymph nodes and suppressed the severity of EAE, an animal model of multiple sclerosis. Our results also demonstrated that MK was produced by inflammatory cells, in particular, CD4(+) T cells under inflammatory conditions. Taken together, these results suggest that MK aggravates EAE by suppressing DCreg development, thereby impairing the Treg population. Thus, MK is a promising therapeutic target for various autoimmune diseases.

Diagnostic values of soluble triggering receptor expressed on myeloid cells (sTREM-1) and interferon-inducible protein-10 (IP-10) for severe mycoplasma pneumoniae pneumonia in children.

OBJECTIVE: Early diagnosis of Severity Mycoplasma Pneumoniae Pneumonia (SMPP) has been a worldwide concern in clinical practice. Two cytokines, soluble Triggering Receptor Expressed on Myeloid cells (sTREM-1) and Interferon-Inducible Protein-10 (IP-10), were proved to be implicated in bacterial infection diseases. However, the diagnostic value of sTREM-1 and IP-10 in MPP was poorly known. This study aimed to investigate the diagnostic value of sTREM-1 and IP-10 for SMPP. METHODS: In this prospective study, the authors enrolled 44 children with MPP, along with their clinical information. Blood samples were collected, and cytokine levels of sTREM-1 and IP-10 were detected with ELISA assay. RESULTS: Serum levels of sTREM-1 and IP-10 were positively correlated with the severity of MPP. In addition, sTREM-1 and IP-10 have significant potential in the diagnosis of SMPP with an Area Under Curve (AUC) of 0.8564 (p-value = 0.0001, 95% CI 0.7461 to 0.9668) and 0.8086 (p-value = 0.0002, 95% CI 0.6918 to 0.9254) respectively. Notably, the combined diagnostic value of sTREM-1 and IP-10 is up to 0.911 in children with SMPP (p-value < 0.001, 95% CI 0.830 to 0.993). CONCLUSIONS: Serum cytokine levels of sTREM-1 and IP-10 have a great potential diagnostic value in children with SMPP.

Updated prevalence of latent prostate cancer in Chinese population and comparison of biopsy results: An autopsy-based study.

Prostate cancer detected by autopsy is named latent prostate cancer. As the repertoire of clinical prostate cancer, latent cancer may better reflect the disease burden. Unlike clinical prostate specimens, which are obtained exclusively from biopsy-positive cases, prostate specimens obtained through autopsy provide information on biopsy-negative cases, helping calculate the true sensitivity of prostate biopsy. From 2014 to 2021, we collected autopsy specimens of the prostate from body donors in China and performed transperineal and transrectal biopsies on specimens before step-sectioning and pathological measurements. We found that the crude prevalence of latent prostate cancer in middle-aged and elderly men was 35.1% (81/231), which was higher than previous estimates for Chinese populations. The overall per-patient sensitivities of transperineal and transrectal biopsies were not significantly different (33.3% vs. 32.1%, p = 0.82), but the two approaches differed in preferential sampling area along the proximal-distal axis of the prostate. Transperineal biopsy had a higher sensitivity for detecting clinically significant lesions in the distal third (34.7% vs. 16.3%, p = 0.02) and distal half (30.6% vs. 18.1%, p = 0.04), while transrectal biopsy had a higher sensitivity for lesions in the proximal half (25.0% vs. 13.9%, p = 0.046). Both transperineal and transrectal methods of biopsy missed most small lesions (<0.1 mL) and 35.3% (6/17) of large lesions (>0.5 mL). In conclusion, the prevalence of latent prostate cancer in China has increased over the past 2 decades. Systematic transperineal and transrectal methods of biopsy had comparable sensitivities but had different preferential sampling areas. Both approaches miss one-third of large lesions.

IL-9 promotes Th17 cell migration into the central nervous system via CC chemokine ligand-20 produced by astrocytes.

Newly discovered IL-9-producing helper T cells (Th9) reportedly exert both aggravating and suppressive roles on experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. However, it is still unclear whether Th9 is a distinct Th cell subset and how IL-9 functions in the CNS. In this study, we show that IL-9 is produced by naive CD4(+) T cells that were stimulated with anti-CD3 and anti-CD28 Abs under the conditions of Th2-, inducible regulatory T cell-, Th17-, and Th9-polarizing conditions and that IL-9 production is significantly suppressed in the absence of IL-4, suggesting that IL-4 is critical for the induction of IL-9 by each producing cell. The IL-9 receptor complex, IL-9R and IL-2Rγ, is constitutively expressed on astrocytes. IL-9 induces astrocytes to produce CCL-20 but not other chemokines, including CCL-2, CCL-3, and CXCL-2 by astrocytes. The conditioned medium of IL-9-stimulated astrocytes induces Th17 cell migration in vitro, which is cancelled by adding anti-CCL-20 neutralizing Abs. Treating with anti-IL-9 neutralizing Abs attenuates experimental autoimmune encephalomyelitis, decreases the number of infiltrating Th17 cells, and reduces CCL-20 expression in astrocytes. These results suggest that IL-9 is produced by several Th cell subsets in the presence of IL-4 and induces CCL-20 production by astrocytes to induce the migration of Th17 cells into the CNS.

[Mycoplasma pneumoniae infection and drug resistance in children: an analysis of 1026 cases].

OBJECTIVE: To investigate the Mycoplasma pneumoniae (MP) infection and drug resistance in children with respiratory tract infection and to provide a rational basis for the clinical diagnosis and treatment of MP infection. METHODS: Throat swabs were collected from 3529 children with respiratory tract infection, who visited the pediatric outpatient department or received treatment in the pediatric ward of our hospital from September 2010 to September 2011. The swabs were cultured to detect MP. The drug sensitivity of MP to azithromycin, roxithromycin, erythromycin, acetylspiramycin and clarithromycin was evaluated. RESULTS: Of the 3529 children with respiratory tract infection, 1026 (29.07%) were MP-positive. There were cases of MP infection in all four seasons of the year but infection rates in summer and autumn were significantly higher than in spring and winter (P < 0.05). The infection rate in females was higher than in males (30.43% vs 28.32%; P > 0.05). The infection rate was negatively correlated with age in these children, and there were significant differences in the infection rate among all age groups (P < 0.05). For macrolide antibiotics suitable for children, the cultured MP developed the highest resistance to roxithromycin, followed by erythromycin, acetylspiramycin, clarithromycin, and azithromycin, with significant differences among them (P < 0.01). CONCLUSIONS: MP infection rate is very high among children with respiratory tract infection. The incidence of MP infection is relatively low among school-age children and children are more susceptible to MP infection in summer and autumn than in spring and winter. Throat swabs should be cultured and drug sensitivity tests should be performed as early as possible in children with respiratory tract infection, so that proper intervention can be undertaken in time to reduce drug-resistant strains of MP.

The prognostic value of zonal origin in clinically localized prostate cancer: a systematic review and meta-analysis.

Introduction: Correlation between zonal origin of clinically localized prostate cancer (PC) and biochemical recurrence (BCR) after treatment is still controversial. Methods: We performed a meta-analysis of published articles to investigate the prognostic value of zonal origin in clinically localized PC. Literature was searched from Medline, Embase, Scopus, and Web of Science, from inception to Nov 1st, 2022. The risk of BCR was compared between PC originating from transition zone with peripheral zone. Relative risk (RR) was pooled in a random-effects model. Subgroup analysis and meta-regression were conducted to assess the source of heterogeneity. Results: 16 cohorts and 19,365 patients were included. PC originating from transition zone was associated with a lower risk of BCR (RR, 0.79, 95%CI; 0.69-0.92, I2, 76.8%). The association was consistent in studies with median follow-up time ≥60 months (RR, 0.65; 95%CI, 0.48 to 0.88, I2 56.8%), studies with NOS score ≥8 (RR, 0.70; 95%CI, 0.62 to 0.80, I2 32.4%), and studies using multivariate regression model (RR, 0.57; 95%CI, 0.48 to 0.69, I2 23%). Discussion: This meta-analysis supported that transition zone origin was an independent prognostic factor of a better biochemical result in clinically localized prostate cancer after treatment. Systematic review registration: 10.37766/inplasy2023.11.0100, identifier INPLASY2023110100.

Astroglial exosome HepaCAM signaling and ApoE antagonization coordinates early postnatal cortical pyramidal neuronal axon growth and dendritic spine formation.

Developing astroglia play important roles in regulating synaptogenesis through secreted and contact signals. Whether they regulate postnatal axon growth is unknown. By selectively isolating exosomes using size-exclusion chromatography (SEC) and employing cell-type specific exosome reporter mice, our current results define a secreted astroglial exosome pathway that can spread long-range in vivo and stimulate axon growth of cortical pyramidal neurons. Subsequent biochemical and genetic studies found that surface expression of glial HepaCAM protein essentially and sufficiently mediates the axon-stimulating effect of astroglial exosomes. Interestingly, apolipoprotein E (ApoE), a major astroglia-secreted cholesterol carrier to promote synaptogenesis, strongly inhibits the stimulatory effect of astroglial exosomes on axon growth. Developmental ApoE deficiency also significantly reduces spine density of cortical pyramidal neurons. Together, our study suggests a surface contact mechanism of astroglial exosomes in regulating axon growth and its antagonization by ApoE, which collectively coordinates early postnatal pyramidal neuronal axon growth and dendritic spine formation.

Astroglial exosome HepaCAM signaling and ApoE antagonization coordinates early postnatal cortical pyramidal neuronal axon growth and dendritic spine formation.

Developing astroglia play important roles in regulating synaptogenesis through secreted and contact signals. Whether they regulate postnatal axon growth is unknown. By selectively isolating exosomes using size-exclusion chromatography (SEC) and employing cell-type specific exosome reporter mice, our current results define a secreted astroglial exosome pathway that can spread long-range in vivo and stimulate axon growth of cortical pyramidal neurons. Subsequent biochemical and genetic studies found that surface expression of glial HepaCAM protein essentially and sufficiently mediates the axon-stimulating effect of astroglial exosomes. Interestingly, apolipoprotein E (ApoE), a major astroglia-secreted cholesterol carrier to promote synaptogenesis, strongly inhibits the stimulatory effect of astroglial exosomes on axon growth. Developmental ApoE deficiency also significantly reduces spine density of cortical pyramidal neurons. Together, our study suggests a surface contact mechanism of astroglial exosomes in regulating axon growth and its antagonization by ApoE, which collectively coordinates early postnatal pyramidal neuronal axon growth and dendritic spine formation.