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Research ArticleInflammationNeuroscience
Open Access | 
10.1172/jci.insight.181885
1Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
2Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China.
3Department of Gynecology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
4School of Pharmacy, Macau University of Science and Technology, Macau, China.
5Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital Clinical College of Nanjing University of Chinese Medicine, Nanjing, China.
6State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
7Department of Epidemiology, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China.
8Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.
Address correspondence to: Lingyun Sun, Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, 321 Zhongshan Road, Nanjing, Jiangsu 210008, China. Phone: 86.025.68182422; Email: lingyunsun@nju.edu.cn. Or to: Zhibin Hu, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China. Phone: 86.025.86868440; Email: zhibin_hu@njmu.edu.cn.
Authorship note: XH, DW, and LC are co–first authors. LS and ZH are co-senior and co-corresponding authors.
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1Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
2Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China.
3Department of Gynecology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
4School of Pharmacy, Macau University of Science and Technology, Macau, China.
5Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital Clinical College of Nanjing University of Chinese Medicine, Nanjing, China.
6State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
7Department of Epidemiology, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China.
8Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.
Address correspondence to: Lingyun Sun, Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, 321 Zhongshan Road, Nanjing, Jiangsu 210008, China. Phone: 86.025.68182422; Email: lingyunsun@nju.edu.cn. Or to: Zhibin Hu, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China. Phone: 86.025.86868440; Email: zhibin_hu@njmu.edu.cn.
Authorship note: XH, DW, and LC are co–first authors. LS and ZH are co-senior and co-corresponding authors.
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1Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
2Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China.
3Department of Gynecology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
4School of Pharmacy, Macau University of Science and Technology, Macau, China.
5Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital Clinical College of Nanjing University of Chinese Medicine, Nanjing, China.
6State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
7Department of Epidemiology, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China.
8Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.
Address correspondence to: Lingyun Sun, Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, 321 Zhongshan Road, Nanjing, Jiangsu 210008, China. Phone: 86.025.68182422; Email: lingyunsun@nju.edu.cn. Or to: Zhibin Hu, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China. Phone: 86.025.86868440; Email: zhibin_hu@njmu.edu.cn.
Authorship note: XH, DW, and LC are co–first authors. LS and ZH are co-senior and co-corresponding authors.
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1Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
2Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China.
3Department of Gynecology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
4School of Pharmacy, Macau University of Science and Technology, Macau, China.
5Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital Clinical College of Nanjing University of Chinese Medicine, Nanjing, China.
6State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
7Department of Epidemiology, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China.
8Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.
Address correspondence to: Lingyun Sun, Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, 321 Zhongshan Road, Nanjing, Jiangsu 210008, China. Phone: 86.025.68182422; Email: lingyunsun@nju.edu.cn. Or to: Zhibin Hu, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China. Phone: 86.025.86868440; Email: zhibin_hu@njmu.edu.cn.
Authorship note: XH, DW, and LC are co–first authors. LS and ZH are co-senior and co-corresponding authors.
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1Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
2Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China.
3Department of Gynecology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
4School of Pharmacy, Macau University of Science and Technology, Macau, China.
5Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital Clinical College of Nanjing University of Chinese Medicine, Nanjing, China.
6State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
7Department of Epidemiology, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China.
8Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.
Address correspondence to: Lingyun Sun, Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, 321 Zhongshan Road, Nanjing, Jiangsu 210008, China. Phone: 86.025.68182422; Email: lingyunsun@nju.edu.cn. Or to: Zhibin Hu, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China. Phone: 86.025.86868440; Email: zhibin_hu@njmu.edu.cn.
Authorship note: XH, DW, and LC are co–first authors. LS and ZH are co-senior and co-corresponding authors.
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1Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
2Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China.
3Department of Gynecology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
4School of Pharmacy, Macau University of Science and Technology, Macau, China.
5Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital Clinical College of Nanjing University of Chinese Medicine, Nanjing, China.
6State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
7Department of Epidemiology, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China.
8Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.
Address correspondence to: Lingyun Sun, Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, 321 Zhongshan Road, Nanjing, Jiangsu 210008, China. Phone: 86.025.68182422; Email: lingyunsun@nju.edu.cn. Or to: Zhibin Hu, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China. Phone: 86.025.86868440; Email: zhibin_hu@njmu.edu.cn.
Authorship note: XH, DW, and LC are co–first authors. LS and ZH are co-senior and co-corresponding authors.
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1Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
2Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China.
3Department of Gynecology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
4School of Pharmacy, Macau University of Science and Technology, Macau, China.
5Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital Clinical College of Nanjing University of Chinese Medicine, Nanjing, China.
6State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
7Department of Epidemiology, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China.
8Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.
Address correspondence to: Lingyun Sun, Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, 321 Zhongshan Road, Nanjing, Jiangsu 210008, China. Phone: 86.025.68182422; Email: lingyunsun@nju.edu.cn. Or to: Zhibin Hu, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China. Phone: 86.025.86868440; Email: zhibin_hu@njmu.edu.cn.
Authorship note: XH, DW, and LC are co–first authors. LS and ZH are co-senior and co-corresponding authors.
Find articles by Zhao, S. in: JCI | PubMed | Google Scholar
1Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
2Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China.
3Department of Gynecology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
4School of Pharmacy, Macau University of Science and Technology, Macau, China.
5Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital Clinical College of Nanjing University of Chinese Medicine, Nanjing, China.
6State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
7Department of Epidemiology, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China.
8Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.
Address correspondence to: Lingyun Sun, Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, 321 Zhongshan Road, Nanjing, Jiangsu 210008, China. Phone: 86.025.68182422; Email: lingyunsun@nju.edu.cn. Or to: Zhibin Hu, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China. Phone: 86.025.86868440; Email: zhibin_hu@njmu.edu.cn.
Authorship note: XH, DW, and LC are co–first authors. LS and ZH are co-senior and co-corresponding authors.
Find articles by Liang, J. in: JCI | PubMed | Google Scholar
1Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
2Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China.
3Department of Gynecology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
4School of Pharmacy, Macau University of Science and Technology, Macau, China.
5Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital Clinical College of Nanjing University of Chinese Medicine, Nanjing, China.
6State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
7Department of Epidemiology, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China.
8Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.
Address correspondence to: Lingyun Sun, Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, 321 Zhongshan Road, Nanjing, Jiangsu 210008, China. Phone: 86.025.68182422; Email: lingyunsun@nju.edu.cn. Or to: Zhibin Hu, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China. Phone: 86.025.86868440; Email: zhibin_hu@njmu.edu.cn.
Authorship note: XH, DW, and LC are co–first authors. LS and ZH are co-senior and co-corresponding authors.
Find articles by Xu, T. in: JCI | PubMed | Google Scholar
1Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
2Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China.
3Department of Gynecology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
4School of Pharmacy, Macau University of Science and Technology, Macau, China.
5Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital Clinical College of Nanjing University of Chinese Medicine, Nanjing, China.
6State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
7Department of Epidemiology, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China.
8Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.
Address correspondence to: Lingyun Sun, Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, 321 Zhongshan Road, Nanjing, Jiangsu 210008, China. Phone: 86.025.68182422; Email: lingyunsun@nju.edu.cn. Or to: Zhibin Hu, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China. Phone: 86.025.86868440; Email: zhibin_hu@njmu.edu.cn.
Authorship note: XH, DW, and LC are co–first authors. LS and ZH are co-senior and co-corresponding authors.
Find articles by Hu, Z. in: JCI | PubMed | Google Scholar
1Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
2Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China.
3Department of Gynecology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
4School of Pharmacy, Macau University of Science and Technology, Macau, China.
5Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital Clinical College of Nanjing University of Chinese Medicine, Nanjing, China.
6State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, Nanjing, China.
7Department of Epidemiology, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China.
8Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.
Address correspondence to: Lingyun Sun, Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, 321 Zhongshan Road, Nanjing, Jiangsu 210008, China. Phone: 86.025.68182422; Email: lingyunsun@nju.edu.cn. Or to: Zhibin Hu, State Key Laboratory of Reproductive Medicine and Offspring Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China. Phone: 86.025.86868440; Email: zhibin_hu@njmu.edu.cn.
Authorship note: XH, DW, and LC are co–first authors. LS and ZH are co-senior and co-corresponding authors.
Find articles by Sun, L. in: JCI | PubMed | Google Scholar
Authorship note: XH, DW, and LC are co–first authors. LS and ZH are co-senior and co-corresponding authors.
Published March 6, 2025 - More info
Published in Volume 10, Issue 8 on April 22, 2025
AbstractSystemic lupus erythematosus (SLE), an autoimmune disease, can cause psychiatric disorders, particularly depression, via immune activation. Human umbilical cord mesenchymal stromal cell (hUCMSC) transplantation (MSCT) has been shown to ameliorate immune dysfunction in SLE by inducing immune tolerance. However, whether MSCT can relieve the depressive symptoms in SLE remains incompletely understood. Here, we demonstrate that MSCT relieved early-onset depression-like behavior in both genetically lupus-prone (MRL/lpr) and pristane-induced lupus mice by rescuing impaired hippocampal synaptic connectivity. Transplanted hUCMSCs targeted Th1 cell–derived IFN-γ to inhibit neuronal JAK/STAT1 signaling and downstream CCL8 expression, reducing phagocytic microglia apposition to alleviate synaptic engulfment and neurological dysfunction in young (8-week-old) lupus mice. Systemic delivery of exogenous IFN-γ blunted MSCT-mediated alleviation of synaptic loss and depressive behavior in lupus mice, suggesting that the IFN-γ/CCL8 axis may be an effective therapeutic target and that MSCT is a potential therapy for lupus-related depression. In summary, transplanted hUCMSCs can target systemic immunity to ameliorate psychiatric disorders by rescuing synaptic loss, highlighting the active role of neurons as intermediaries between systemic immunity and microglia in this process.
Graphical Abstract
Introduction
Systemic lupus erythematosus (SLE) is frequently associated with a range of diffuse central nervous system (CNS) disorders, termed CNS lupus or neuropsychiatric SLE (NPSLE), which can manifest as depression, anxiety, cognitive impairment, etc. (1). Depression is one of the most common mood disorders in patients with SLE and occurs early during the disease process (2, 3). Increased depression-like behavior has also been reported and even detected in an “early” disease state in genetically lupus-prone rodents, e.g., the MRL/lpr (4), NZB × NZW F1, and 564Igi strains (5). Recent advances point to an immune-mediated neuroinflammatory pathogenesis (6, 7), but the detailed mechanism underlying SLE-related depression has not been clarified. Furthermore, owing to the heterogeneity of depression in individuals with SLE, symptom-based diagnostic approaches are inadequate, and effective antidepressant treatments are lacking.
Correct synaptic wiring is a basic prerequisite for accurate synaptic connectivity and neuronal function. Increased elimination of synapses, resulting in an overall loss of synapses, is observed in several pathological conditions, including brain inflammation (8) and SLE (9). Microglia-mediated engulfment of synaptic processes, which is a potential mechanism underlying synapse loss, is increased in these diseases. Moreover, the number and activation of microglia are altered in the brains of individuals with SLE (10). Our previous work demonstrated that increased synaptic stripping by microglia accounts for early neuropsychiatric (NP) symptoms in lupus mice (9). However, the mechanism by which microglia recognize specific synapses for precise pruning remains unclear. Moreover, in SLE, which and how activated systemic immune factors affect synaptic pruning in the brain and whether this systemic signal can be targeted to prevent brain injury and alleviate depression in patients with SLE are unclear. Elucidating these problems would be helpful for early and precise intervention in patients with SLE-related depression.
In addition to microglia, cytotoxic T cells and systemic immune signals can also target neurons in inflammation-related conditions, including viral infections (11), autoimmune diseases (12), and neurodegenerative disorders (13). The cellular and molecular bases of T cell– and T cell–derived cytokine–driven synaptic pathology are currently largely unclear. A recent study proposed that neurons themselves function as intermediaries between CD8+ T cells and phagocytes, driving synaptic loss and motor coordination impairment in encephalitis (11). Additionally, phagocytes can be activated by immune factors (14) and act as effectors of T cell–driven brain damage (15). Thus, it can be hypothesized that microglia are responsible for systemic immune factor–driven synaptic degeneration, but this needs to be verified experimentally.
Recently, accumulating evidence has indicated that systemic mesenchymal stromal cell (MSC) transplantation (MSCT) ameliorates tissue damage in a variety of human diseases, such as graft-versus-host disease (GvHD), autoimmune encephalomyelitis, diabetes, liver fibrosis, Alzheimer disease, and other age-related degenerative diseases (16–21). Multiple mechanisms, including paracrine cytokine secretion (21), direct interplay with immune cells (22), extracellular vesicles (19, 20), and epigenetic regulation (23), have been identified as contributors to the therapeutic effect of MSCT. Our previous studies confirmed that MSCT has therapeutic effects on patients with SLE and SLE model mice (23–26). However, the extent to which MSCT ameliorates NP symptoms, particularly depression, and rescues synaptic structure impairment in patients with SLE remains largely unclear.
In this study, we applied MSCT to both Fas-deficient MRL/lpr mice and pristane-induced lupus mice to explore the early neuroprotective potential of MSCT. We show that MSCT rescues impaired synaptic density and alleviates depression-like behaviors in young (5- to 8-week-old) lupus mice by reducing systemic T helper 1 (Th1) cell–derived IFN-γ levels to inhibit neuronal JAK/STAT1 signaling and downstream CCL8 expression and then inhibit neuron-coordinated synapse elimination by microglia in the brain. Our data provide insights into the molecular mechanisms underlying immune-mediated psychopathy and suggest that biotherapies, such as MSCT, represent potential treatments and require clinical attention.
ResultsLupus mice develop increased depression-like behavior in the early stage of SLE. To investigate the relationship between SLE and depression, we monitored NP changes in MRL/lpr mice, a well-established lupus-prone murine model (27). MRL/lpr mice developed typical SLE-related pathological changes, as evidenced by the presence of anti–double-stranded DNA (anti-dsDNA) antibodies in the serum beginning at 8 weeks, the occurrence of albuminuria, and increased spleen size and weight at 18 weeks (Supplemental Figure 1, A–D; supplemental material available online with this article; https://doi.org/10.1172/jci.insight.181885DS1). To measure depression-like behavior, we first performed the sucrose preference test (SPT) to evaluate the tendency of the mice to consume sucrose at 8 weeks (early stage) and 18 weeks (active stage) (Figure 1A). Compared with control mice, MRL/lpr mice presented a decreased sucrose preference at 8 weeks of age, which was aggravated at 18 weeks of age (Figure 1B). Two other tests (the tail suspension test [TST] and forced swim test [FST]) were employed. The immobility time of MRL/lpr mice was markedly higher than that of control mice in both the TST (Figure 1C) and the FST (Figure 1D) at 8 weeks, and this depressive-like behavior was aggravated at 18 weeks of age. As reduced activity may contribute to immobility in the TST and FST, we then investigated locomotor activity with the open field test (OFT) and found that MRL/lpr mice presented no general locomotor defects (Supplemental Figure 1, E and F).
Figure 1MSCT alleviates depression in MRL/lpr mice. (A) Timeline of the experimental procedure for MRL/lpr mice. (B–D) Evaluation of depression-like behavior in MRL/lpr mice and wild-type (MRL/mpj) controls (n = 11 mice/group). The SPT (B), TST (C), and FST (D) were performed at 8 and 18 weeks. (E) Experimental protocol for the treatment of MRL/lpr mice by MSCT. (F–H) Effects of MSCT on depression-like behavior in MRL/lpr mice (n = 11 mice/group). Five-week-old MRL/lpr mice were intravenously injected with hUCMSCs (5 × 105 cells in 500 μL of PBS) or PBS (as a control). The SPT (F), TST (G), and FST (H) were performed 3 weeks after MSC/PBS injection. The data are presented as mean ± SEM. *P < 0.05; **P < 0.01, determined using 1-way ANOVA followed by Tukey’s post hoc test (B–D), or 2-tailed unpaired t test (F–H). SPT, sucrose preference test; TST, tail suspension test; FST, forced swim test. See also Supplemental Figures 1–4.
For confirmation, we evaluated the behavior of C57BL/6J mice in which lupus was induced by intraperitoneal (i.p.) injection of pristane (28). Ten weeks after pristane injection (early stage), the mice were subjected to behavioral tests (Supplemental Figure 2A). Compared with mineral oil–treated control mice, pristane-treated mice presented a reduced sucrose preference and increased immobility time in both the TST and the FST (Supplemental Figure 2, B–D) and developed typical lupus nephritis–like changes, with increased albuminuria levels and C3 deposition until 5–6 months after pristane treatment (active stage; Supplemental Figure 2, E and F), as reported previously (28). Together, these data indicate that both genetically prone and induced-lupus mice develop depression in the early stage of the disease before the appearance of overt peripheral pathology.
MSCT alleviates depression by attenuating dendritic loss in the brains of lupus mice. MSCT can alleviate various CNS disorders, including autoimmune-related and nonautoimmune-related disorders (21, 29). Here, we investigated whether the transplantation of human umbilical cord MSCs (hUCMSCs), which were delineated (Supplemental Figure 3, A and B) and prepared as previously reported (30), alleviated depression-like behavior in SLE models. We treated 5-week-old MRL/lpr mice with hUCMSCs and assessed depressive behavior 3 weeks later (Figure 1E). Compared with PBS, MSCT ameliorated the decrease in sucrose preference in MRL/lpr mice (Figure 1F). The decrease in immobility time in both the TST (Figure 1G) and the FST (Figure 1H) was markedly ameliorated in the mice that underwent MSCT. In addition, we conducted complementary experiments in pristane-induced lupus mice. Four weeks after pristane injection, the mice were infused with MSCs or PBS and subjected to behavioral tests 6 weeks later (Supplemental Figure 4A). The results observed in the pristane-induced model were consistent with those in MRL/lpr mice (Supplemental Figure 4, B–D).
To determine whether MSCT altered key pathological deficits associated with depressive behavior, we measured the numbers of neurons and dendritic spines in the brains of lupus mice. MRL/lpr mice showed no anatomical damage (Supplemental Figure 5A), no change in the ratio of brain weight to body mass (Supplemental Figure 5, B and C), and no marked neuronal loss in the hippocampus at 8 weeks of age (Supplemental Figure 5, D and E). Golgi staining of hippocampal sections revealed that the number of dendritic spines was significantly reduced in MRL/lpr mice and that this decrease was effectively prevented by MSCT (Figure 2, A and B). In parallel, superresolution fluorescence microscopy revealed that the numbers of both presynaptic (synaptophysin, SYP) and postsynaptic terminals (PSD-95) were substantially decreased in the brains of MRL/lpr mice and that this change was reversed by MSCT (Figure 2, C–E). MSCT also alleviated early-onset splenomegaly and reduced serum anti-dsDNA antibody levels (Supplemental Figure 5, F and G). MSCT-mediated preservation of synaptic terminals was also observed in the pristane-induced model (Supplemental Figure 5H). These results indicate that MSCT substantially alleviates depression-like behavior and prevents hippocampal dendritic loss in lupus mice.
Figure 2MSCT inhibits microglia-mediated synaptic stripping to rescue dendritic loss in the brains of lupus mice. (A and B) Images and quantification of Golgi-stained dendritic spines in dentate gyrus granule neurons from MRL/mpj mice and MSCT/PBS-treated MRL/lpr mice (n = 5 mice/group). Scale bar: 5 μm. (C–E) Immunostaining of presynaptic (synaptophysin, red) and postsynaptic (PSD-95, green) proteins in hippocampal sections from MRL/mpj mice and MSCT/PBS-treated MRL/lpr mice (C) and quantification of the levels of these proteins (D and E) (n = 5 mice/group, with an average of 3–4 slices per mouse). Scale bar: 10 μm. (F) Heatmap showing the relative expression of significantly altered genes in the hippocampi of MRL/mpj and MRL/lpr mice treated with or without MSCT according to RNA-seq (see Methods). The color scale represents the genewise z score calculated from the normalized gene expression levels. Each column represents an individual group (n = 3 mice/group). (G and H) Orthogonal view of a microglial cell (IBA-1, red) showing PSD-95 inclusions (green, upper in G) and colocalization with CD68 (red, upper in H). These findings suggest that microglia eliminate synapses in the hippocampi of MRL/lpr mice. Bottom: 3D reconstruction of the cell in G and lysosome in H (red) and PSD-95 inclusions (green) with Imaris software. Scale bars: 5 μm. (I) Quantification of reconstructed PSD-95+ spheres and PSD-95+CD68+ spheres inside microglia in the indicated mice (n = 20 cells from 4–5 mice). The data are presented as mean ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001 by 1-way ANOVA followed by Tukey’s post hoc test. See also Supplemental Figures 5 and 6.
MSCT inhibits microglia-mediated synaptic stripping to rescue dendritic loss. Microglia act as key mediators of brain circuit connectivity by pruning synapses (31). We then hypothesized that MSCT rescued depression-like behavior and synapse loss in MRL/lpr mice by preventing microglia-mediated synaptic elimination. To test this hypothesis, we employed RNA sequencing (RNA-seq) to compare the gene transcription profiles of microglia isolated from mice after MSCT. The purity of the microglia isolated with an anti-CD11b microbead kit was verified by flow cytometry (Supplemental Figure 6A). Gene Ontology enrichment analysis confirmed that genes enriched in reactive microglia-related pathways, including phagocytosis, engulfment, and the cellular response to IFN-γ and the NF-κB signaling pathway, were upregulated in sorted microglia from MRL/lpr mice (Supplemental Figure 6, B and C). Notably, the expression of phagocytosis-related genes was also upregulated in the hippocampi of MRL/lpr mice, and the changes in the expression of most of these genes were reversed by MSCT (Figure 2F). Immunostaining analysis revealed that MSCT reversed the increase in the phagocytic activity of monocytes in MRL/lpr mouse brain, as evidenced by a reduction in the number of CD68+IBA-1+ microglia and the staining intensity of CD68 in the hippocampus (Supplemental Figure 6, D–F). Moreover, almost all of the IBA-1+ cells in the CNS of MRL/lpr were enriched with the microglia-specific marker TMEM119 (32) (Supplemental Figure 6G), which confirmed the microglia-derived origin of these cells.
We further performed staining for presynaptic (SYP), postsynaptic (PSD-95), microglial (IBA-1), and lysosomal (CD68) markers in mouse hippocampal slices and then evaluated synapse phagocytosis via 3-dimensional (3D) reconstruction to confirm synapse engulfment by microglia (Figure 2, G and H). Quantitative analysis revealed that the number of PSD-95+ puncta in microglia (both within and outside the CD68+ lysosomal compartment) in MRL/lpr mice was markedly higher than that in control mice and that this change was reversed by MSCT (Figure 2I). We also detected an increase in the number of PSD-95+ puncta in IBA-1+ cells in pristane-induced lupus mice, which was alleviated by MSCT (Supplemental Figure 5, I and J). In addition, depletion of microglia with PLX5622, a selective inhibitor of colony-stimulating factor 1 receptor (CSF1R), maintained dendritic integrity and alleviated depressive behavior in MRL/lpr mice (Supplemental Figure 6, H–K), suggesting that microglia-mediated engulfment contributes to synapse loss in lupus mice. These results collectively indicate that MSCT ameliorates depression in a lupus mouse model by inhibiting microglial phagocytosis and rescuing synaptic connectivity.
MSCT targets neuronal CCL8 signaling to inhibit microglial apposition and synaptic stripping. To further determine the mechanism underlying microglial apposition and synapse stripping, we collected hippocampal tissue from MRL/mpj, MRL/lpr, and MRL/lpr + MSCT mice and performed RNA-seq. Among the 1,908 differentially expressed transcripts (1,384 upregulated, 524 downregulated; cutoff of a 1.5-fold change; P < 0.05) in the hippocampi of MRL/lpr mice, MSCT reversed the changes in the expression of 309 transcripts (284 downregulated, 25 upregulated in the MRL/lpr + MSCT group) (Figure 3, A and B, and Supplemental Figure 7A). The top differentially expressed and revised genes were involved in the “cytokine-cytokine receptor interaction” and “chemokine signaling pathway” (Supplemental Figure 7B). Neurons actively regulate the recruitment of phagocytes via paracrine mechanisms (11, 33). We then hypothesized that there are soluble factor(s) produced by neurons that might be responsible for phagocytic microglial apposition. Next, we screened genes from the RNA-seq data and published literature that might be involved in this process and identified CCL8 as a candidate (Figure 3C). The results of quantitative PCR and ELISA confirmed that the expression of CCL8 in the hippocampi of MRL/lpr mice was increased and that this increase was reversed by MSCT (Figure 3, D and E, and Supplemental Figure 7C). The CC-motif chemokine receptor type 5 (Ccr5), which interacts with CC-motif chemokine ligand 8 (Ccl8), was highly expressed in the lupus brain and suppressed by MSCT, as revealed by the RNA-seq data and confirmed by PCR (Figure 3, C and D). RNAscope in situ hybridization (FISH) revealed elevated Ccl8 mRNA expression in MRL/lpr mouse brains, which was detected mainly in Eno2+ neurons but not in TMEM119+ microglia (Figure 3, F and G, and Supplemental Figure 7D). This finding is consistent with the increase in the number of neurons contacted by IBA-1+ microglia in the brains of lupus mice (Supplemental Figure 8, I and J). Additionally, MSCT reduced the number of Ccl8+ neurons in the brains of lupus mice (Figure 3, F and G).
Figure 3MSCT inhibits microglial apposition and synaptic stripping by targeting neuronal CCL8 signaling. (A and B) Mouse hippocampal tissues were harvested, and RNA-seq was subsequently performed. The heatmap shows all genes whose expression was altered in MRL/lpr mice compared with MRL/mpj mice and whose expression was further reversed by MSCT (A). The Venn diagram (B) shows overlapping genes that were significantly upregulated in MRL/lpr mice versus controls and whose expression was reversed by MSCT (downregulated in MSCT-treated mice versus MRL/lpr mice). (C) Heatmap showing the significantly altered genes enriched in “chemokine signaling pathway.” Each column represents an individual group (n = 3 mice/group). The color scale represents the genewise z score calculated from the normalized gene expression levels. Genes are ordered by hierarchical clustering (A and C). (D) Validation of selected genes in a unique set of mice by qPCR (n = 4 mice/group). (E) Validation of CCL8 levels in the serum and hippocampal homogenates of each group by ELISA (n = 6 mice/group). (F) Representative images of FISH for Ccl8 (green) and the neuronal marker Eno2 (red) in hippocampal sections from the indicated mice. Scale bar: 20 μm. (G) Quantitative results for Ccl8+ neurons in the hippocampal sections (n = 7 mice/group). (H–J) Evaluation of depression-like behavior in pristane-treated Ccl8fl/fl and Syn1Cre;Ccl8fl/fl mice (n = 9 mice/group). Ten weeks after pristane injection, the mice were subjected to the SPT (H), TST (I), and FST (J). The data are presented as mean ± SEM. *P < 0.05; ***P < 0.001, determined using 1-way ANOVA followed by Tukey’s post hoc test (D and E), or 2-tailed unpaired t test (H–J). NS, not significant; DEGs, differentially expressed genes; SPT, sucrose preference test; TST, tail suspension test; FST, forced swim test. See also Supplemental Figures 7 and 8.
To examine directly whether neuronal CCL8 chemokine signaling is required for microglial chemotaxis and synaptic injury in SLE, we used Syn1Cre;Ccl8fl/fl mice in which Ccl8 was conditionally knocked out in neurons in the brain parenchyma. Both Ccl8-knockout mice and their controls (Ccl8fl/fl) were subjected to pristane or mineral oil injection (Supplemental Figure 8A). Compared with age-matched littermate controls (Ccl8fl/fl), Syn1Cre;Ccl8fl/fl mice were born normally and presented no obvious abnormalities in body weight or locomotor performance (Supplemental Figure 8, B–D). Neurons expressing Ccl8 were detected in the brains of pristane-treated Ccl8fl/fl but not Syn1Cre;Ccl8fl/fl mice (Supplemental Figure 8E), confirming the conditional neuronal deletion of Ccl8 in these mice. Further analysis revealed that neuronal Ccl8 knockout largely protected mice from depression, as evidenced by reduced depressive behavior (Figure 3, H–J), an increase in the number of synapses in the CA1 region (Supplemental Figure 8, F–H), and a decrease in the number of microglia adjacent to neurons (Supplemental Figure 8, I–L), without affecting the phagocytic activity of microglia (Supplemental Figure 8M).
Together, these findings indicate that aberrant expression of neuronal CCL8 plays an important role in phagocyte apposition and that inhibition of CCL8 expression may be responsible for the ability of MSCT to prevent syn
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