Objective To investigate the effects of removing microglia from spinal cord on nerve repair and functional recovery after spinal cord injury (SCI) in mice. MethodsThirty-nine 6-week-old female C57BL/6 mice were randomly divided into control group (n=12), SCI group (n=12), and PLX3397+SCI group (n=15). The PLX3397+SCI group received continuous feeding of PLX3397, a colony-stimulating factor 1 receptor inhibitor, while the other two groups were fed a standard diet. After 14 days, both the SCI group and the PLX3397+SCI group were tested for ionized calcium binding adapter molecule 1 (Iba1) to confirm that the PLX3397+SCI group had completely depleted the spinal cord microglia. The SCI model was then prepared by clamping the spinal cord in both the SCI group and the PLX3397+SCI group, while the control group underwent laminectomy. Preoperatively and at 1, 3, 7, 14, 21, and 28 days postoperatively, the Basso Mouse Scale (BMS) was used to assess the hind limb function of mice in each group. At 28 days, a footprint test was conducted to observe the gait of the mice. After SCI, spinal cord tissue from the injury site was taken, and Iba1 immunofluorescence staining was performed at 7 days to observe the aggregation and proliferation of microglia in the spinal cord. HE staining was used to observe the formation of glial scars at the injury site at 28 days; glial fibrillary acidic protein (GFAP) immunofluorescence staining was applied to astrocytes to assess the extent of the injured area; neuronal nuclei antigen (NeuN) immunofluorescence staining was used to evaluate neuronal survival. And 5-hydroxytryptamine (5-HT) immunofluorescence staining was performed to assess axonal survival at 60 days. Results All mice survived until the end of the experiment. Immunofluorescence staining revealed that the microglia in the spinal cord of the PLX3397+SCI group decreased by more than 95% compared to the control group after 14 days of continuous feeding with PLX3397 (P<0.05). Compared to the control group, the BMS scores in the PLX3397+SCI group and the SCI group significantly decreased at different time points after SCI (P<0.05). Moreover, the PLX3397+SCI group showed a further decrease in BMS scores compared to the SCI group, and exhibited a dragging gait. The differences between the two groups were significant at 14, 21, and 28 days (P<0.05). HE staining at 28 days revealed that the SCI group had formed a well-defined and dense gliotic scar, while the PLX3397+SCI group also developed a gliotic scar, but with a more blurred and loose boundary. Immunofluorescence staining revealed that the number of microglia near the injury center at 7 days increased in the SCI group than in the control group, but the difference between groups was not significant (P>0.05). In contrast, the PLX3397+SCI group showed a significant reduction in microglia compared to both the control and SCI groups (P<0.05). At 28 days after SCI, the area of spinal cord injury in the PLX3397+SCI group was significantly larger than that in SCI group (P<0.05); the surviving neurons significantly reduced compared with the control group and SCI group (P<0.05). The axonal necrosis and retraction at 60 days after SCI were more obvious. ConclusionThe removal of microglia in the spinal cord aggravate the tissue damage after SCI and affecte the recovery of motor function in mice, suggesting that microglia played a neuroprotective role in SCI.
ObjectiveTo investigate the six-degree-of-freedom (6-DOF) kinematic characteristics of the knee joint and changes in plasma inflammatory factors during the acute and non-acute phases following anterior cruciate ligament (ACL) injury, thereby providing clinical evidence for the necessity of early intervention after ACL injury. MethodsPatients with ACL injury admitted between August 2024 and June 2025 were enrolled. A total of 56 patients met the inclusion criteria, including 24 in the acute phase (disease duration<30 days) and 32 in the non-acute phase (disease duration≥30 days). Thirty healthy volunteers served as the control group. No significant difference was observed among the three groups in baseline characteristics (P>0.05), including age, height, body weight, body mass index, and the proportion of concomitant meniscal injury. All participants underwent gait analysis using the Opti-Knee system to measure 6-DOF kinematic parameters of the knee joint, including flexion/extension angle, internal/external rotation angle, varus/valgus angle, anterior/posterior displacement, medial/lateral displacement, and superior/inferior displacement. The trends across the gait cycle and differences at key time points among the three groups were assessed. Additionally, venous blood samples were collected to measure the levels of inflammatory factors. Finally, correlation analyses were performed on kinematic parameters and inflammatory factors with significant intergroup differences. ResultsGait analysis showed that compared with the control group, the flexion/extension angle decreased and the anterior/posterior displacement increased in both the acute and non-acute phase groups; the varus/valgus angle and internal/external rotation angle also increased in the non-acute phase group; all differences were significant (P<0.05). However, no significant difference was found in the kinematic parameters between the acute and non-acute phase groups (P>0.05). No significant difference in the medial/lateral displacemen or superior/inferiordisplacement among the three groups (P>0.05). The acute and non-acute phase groups exhibited similar change trends in 6-DOF. Compared with the control group, they showed a smaller flexion angle and greater internal rotation angle, valgus angle, and anterior displacement during the gait cycle. At some key time points, the knee joint displayed abnormal patterns including tibial anterior displacement, valgus, and internal rotation. Blood tests revealed that compared with the control group, the levels of interleukin-6 (IL-6), IL-8, IL-1β, and tumor necrosis factor α (TNF-α) significantly increased in both the acute and non-acute phase groups (P<0.05); and no significant difference was observed between the acute and non-acute phase groups (P>0.05). Correlation analysis showed that anterior/posterior displacement was positively correlated with IL-6, TNF-α, and IL-1β (P<0.05); the flexion/extension angle was negatively correlated with IL-6, IL-8, and TNF-α (P<0.05). ConclusionAfter ACL injury, characteristic dynamic knee instability and a pro-inflammatory microenvironment persist simultaneously. This dual mechanical and biological disturbance may constitute the pathological basis for the development and progression of post-traumatic osteoarthritis, underscoring the necessity of early intervention.