Exosome Transplantation From Patients With Schizophrenia Causes Schizophrenia-Relevant Behaviors in Mice: An Integrative Multi-omics Data Analysis

Abstract

Exosomes are involved in the pathophysiology of neuropsychiatric diseases, but the role of exosomes in schizophrenia (SCZ) is unclear. Here, we demonstrate that transplantation of serum exosomes from SCZ patients into mice caused behavioral abnormalities such as deficits in prepulse inhibition and sociability, hyperactivity, and anxiogenesis. A comparative bioinformatics analysis suggested shared and distinct differentially expressed genes (DEGs) and enriched molecular pathways in the brains of SCZ exosome-recipient mice, methylazoxymethanol acetate-treated rats, and SCZ patients, which correlates evidence of altered prefrontal-hippocampal functional coherence in SCZ. A large proportion of SCZ-relevant DEGs in the exosome-recipient mice were targets of DE exosomal miRNAs in SCZ patients. Furthermore, we identified 20 hub genes for SCZ risk genes, including BDNF and NRG1, which were DE miRNA targets in SCZ. Collectively, our study suggests that SCZ exosome transplantation caused SCZ-relevant behaviors in mice, and epigenetic regulation may contribute to the phenotypes in the SCZ exosome-recipient mice. Our results may provide a potential animal model and novel therapeutic targets for SCZ.

Keywords: behavior; bioinformatics; exosome; miRNA; schizophrenia.

Fig. 1.

Blood exosome transplantation from SCZ patients leads to SCZ-relevant behaviors in mice. (a) Compared with saline- and HC exosome-recipient mice, the percent of PPI was significantly decreased in SCZ exosome-recipient mice. (b) Compared with saline-treated rats, the percent of PPI was significantly decreased in MAM-treated rats. (c and d) Social behavior tests for mice. (c) Session I: Sociability. Unlike saline- and HC exosome-recipient mice, SCZ exosome-recipient mice failed to demonstrate a preference for sociability. (d) Session II: Social memory and novelty. Unlike saline- and HC exosome-recipient mice, SCZ exosome-recipient mice failed to demonstrate a preference for social novelty. (e and f) Social behavior tests for rats. MAM-treated rats failed to demonstrate preferences for sociability and social novelty. (g) Open-field test. The total distance traveled was significantly increased in SCZ exosome-recipient mice. (h) Tail suspension test. The duration of immobility was significantly decreased in the SCZ exosome-recipient mice. (i) Elevated plus maze test for mice. The ratio of time spent in the open arm of the maze was significantly decreased in SCZ exosome-recipient mice. (j) Elevated plus maze test for rats. The ratio of time spent in the open arm of the maze was significantly decreased in MAM-treated rats. (k) Y-maze test for mice. There was no difference in the alteration rate between the 3 groups. (l) Novel object recognition test for mice. There was no significant difference in the novel discrimination index between the 3 groups. (m) Y-maze test for rats. Compared to saline-treated rats, the alteration rate of MAM-treated rats was significantly decreased. (n) Novel object recognition test for rats. There was no difference in the novel discrimination index between the 2 groups. SCZ, schizophrenia; HC, healthy control; PPI, prepulse inhibition; EXO, exosome; MAM, methylazoxymethanol acetate. N =12. One-way analysis of variance followed by Tukey’s post hoc analysis of mean differences was used to compare multiple groups. Two-tailed Student’s t tests were used to compare the means of 2 groups.

Fig. 2.

Bioinformatics analysis of DE mRNAs. (a) Heatmaps show cluster analysis data for 1887 DE mRNAs in the hippocampus. (b) Metascape enrichment network analysis data depicting the intra- and intercluster similarities of enriched terms in the hippocampus. (c) Bubble map for viewing the top 20 Metascape enrichment clusters in the hippocampus, a unique square code represents a specific cluster. (d–g) Venn diagram showed the number of unique and overlapped genes from 3 closely bridged enrichment clusters, and protein–protein interaction networks were constructed with the overlapped genes. (h) Heatmaps show cluster analysis data for 2267 DE mRNAs in the prefrontal cortex. (i) Metascape enrichment network analysis data depicting the intra- and intercluster similarities of enriched terms in the prefrontal cortex. (j) Bubble map for viewing the top 20 Metascape enrichment clusters in the prefrontal cortex, a unique square code represents a specific cluster. (k and l) Venn diagram showed the number of unique and overlapped genes from 3 closely bridged enrichment clusters, and a protein–protein interaction network was constructed with the overlapped genes. (m and n) The Venn diagram showed the number of unique and overlapped genes from 3 closely bridged enrichment clusters, and a bar graph showed the 9 overlap genes. DE, differentially expressed; mRNA, messenger RNA.

Fig. 3.

Bioinformatics analysis of DE miRNA predicted target genes validated by mRNA-seq. Volcano plot (a) and bar graph (b) showed 19 up-regulated and 7 down-regulated DE blood exosomal miRNAs in patients with SCZ and HC subjects. (c–f) The top 20 Metascape enrichment clusters of DE miRNA predicted target genes validated by mRNA-seq in the hippocampus and prefrontal cortex. SCZ, schizophrenia; HC, healthy control; mRNA-seq, mRNA sequencing; DE, differentially expressed.

Fig. 4.

Association of SCZ exosome-related molecular phenotypes with SCZ risk genes. (a and b) Venn diagram and bar graph showed 9 overlapped genes from SCZ risk genes, DE mRNAs in the hippocampus and prefrontal cortex of SCZ exosome-recipient mice. (c) Network construction for hub gene analysis of SCZ risk genes from previous GWAS. (d) Bar graph showing 6 hub genes that were DE in the hippocampus or prefrontal cortex of SCZ exosome-recipient mice. Venn diagram indicated overlapped DE genes between SCZ exosome-recipient mice and postmortem SCZ patients in the hippocampus (e) and prefrontal cortex (f). Metascape bar graph for viewing top 20 nonredundant enrichment clusters of the DE mRNAs between SCZ exosome-recipient mice and postmortem SCZ patients in the hippocampus (g) and prefrontal cortex (h). GO chord plot showing Metascape enrichment clusters of overlapped DE genes between postmortem SCZ patients and exosome-recipient mice in the hippocampus (i) and prefrontal cortex (j). DEG, differentially expressed gene; SCZ, schizophrenia. GO, gene ontology; GWAS, genome-wide association study.

Fig. 5.

The workflow diagram for this study. SCZ blood exosome transplantation into mice leads to molecular and neurobehavioral phenotypes relevant to SCZ. SCZ, schizophrenia.