3.1 Demographic and clinical characteristics
The data from patients with NMO (n = 24), MS (n = 15), autoimmune GFAP astrocytopathy (n = 10) and 18 controls are presented in Table 1. The median EDSS score (with IQR) was 4.0 (3.13, 4.88) for the NMO group, 2.5 (2.00, 3.00) for the MS group and 2.75 (2.38, 3.50) for the autoimmune GFAP astrocytopathy group (Table 1). There were no statistically significant differences in sex or age among groups.
3.2 Increased HS, HA and related cytokine levels in serum and CSF in patients with NMO, MS and autoimmune GFAP astrocytopathy
As shown in Table 1, the median concentrations of IFNγ and IL17A in CSF and serum of NMO, MS and autoimmune GFAP astrocytopathy patients were higher than those of the control group (All p < 0.001). For MMP1, CSF concentrations but not serum were elevated in patients with NMO, MS and autoimmune GFAP astrocytopathy compared with those of the control group(CSF: p < 0.01; Seurm: p > 0.05). To further assess the severity of BBB injury in these autoimmune encephalitis patients, we compared the levels of HS and HA among patients with NMO, MS and autoimmune GFAP astrocytopathy and controls. Concentrations of HS and HA in plasma and CSF were elevated in the autoimmune encephalitis group compared with those in the control group (serum HS: NMO p < 0.001, MS p = 0.022, GFAP p < 0.001, respectively, Fig. 1A; CSF HS: NMO p < 0.001, MS p < 0.001, GFAP p < 0.001, respectively, Fig. 1B. serum HA: NMO p < 0.001, MS p < 0.001, GFAP p < 0.001, respectively, Fig. 1C; CSF HA: NMO p < 0.001, MS p < 0.001, GFAP p = 0.057, respectively, Fig. 1D). However, no significant differences in levels of serum or CSF glycocalyx molecules or other cytokine parameters were found among NMO, MS and autoimmune GFAP astrocytopathy patients. To assess relationships between the levels of glycocalyx molecules in CSF and serum, correlation tests were performed in autoimmune encephalitis subgroups. Positive correlation between CSF and serum levels was only present for HS in NMO and HA in MS (NMO HS: p = 0.029, r = 0.447; MS HA: p = 0.005, r = 0.696).
3.3 Correlations between CSF and plasma HS and HA levels and EDSS scores
To assess possible links between CSF and plasma glycocalyx levels and the severity of these three disorders, we examined correlations among them (Fig. 2). In patients with NMO, MS or autoimmune GFAP astrocytopathy, we detected a significant positive correlation between concentrations of CSF HS and HA and EDSS scores (NMO HS: p = 0.024, r = 0.460; MS HS: p = 0.004, r = 0.707; autoimmune GFAP astrocytopathy HS: p = 0.047, r = 0.650; NMO HA: p = 0.010, r = 0.514; MS HA: p = 0.030, r = 568; autoimmune GFAP astrocytopathy HA: p = 0.037, r = 0.675). For serum levels and EDSS scores, we only found a significant correlation between serum HS and EDSS scores in the NMO group (p = 0.043, r = 0.417). Positive correlations between other serum levels and EDSS scores were detected but they did not reach statistical significance (NMO HA: p = 0.051, r = 0.403. MS HS: p = 0.064, r = 495; HA: p = 0.104, r = 440. autoimmune GFAP astrocytopathy HS: p = 0.241, r = 0.409; HA: p = 0.065, r = 0.613).
3.4 Associations between CSF glycocalyx molecules and other cytokine parameters
Previous studies have found elevated levels of pro-inflammatory cytokines in CSF of patients with NMO, MS and autoimmune GFAP astrocytopathy. Here, we detected associations among CSF glycocalyx molecules and IFNγ, IL17A and MMP1 (Fig. 3). Interestingly, in the CSF of patients with NMO, MS or autoimmune GFAP astrocytopathy, there was a universal positive correlation between concentrations of HS and MMP1 (NMO, p = 0.032, r = 0.483; MS, p = 0.024, r = 0.586; GFAP, p = 0.025, r = 0.711) (Fig. 3A, C, E). Moreover, significant positive correlations were also found between CSF HS and IFNγ (p = 0.022, r = 0.465) and CSF HA and MMP1 (p = 0.001, r = 0.622) in the NMO group (Fig. 3A, B), CSF HS and IL17A (p = 0.043, r = 0.533) and CSF HA and IFNγ (p = 0.014, r = 0.629) in the MS group (Fig. 3C, D), and CSF HA and IL17A (p = 0.035, r = 0.685) in the autoimmune GFAP astrocytopathy group (Fig. 3F).