Zinc deficiency impairs axonal regeneration and functional recovery after spinal cord injury by modulating macrophage polarization via NF-κB pathway.

Background: Spinal cord injury (SCI) is a devastating disease that results in permanent paralysis. Currently, there is no effective treatment for SCI, and it is important to identify factors that can provide therapeutic intervention during the course of the disease. Zinc, an essential trace element, has attracted attention as a regulator of inflammatory responses. In this study, we investigated the effect of zinc status on the SCI pathology and whether or not zinc could be a potential therapeutic target. Methods: We created experimental mouse models with three different serum zinc concentration by changing the zinc content of the diet. After inducing contusion injury to the spinal cord of three mouse models, we assessed inflammation, apoptosis, demyelination, axonal regeneration, and the number of nuclear translocations of NF-κB in macrophages by using qPCR and immunostaining. In addition, macrophages in the injured spinal cord of these mouse models were isolated by flow cytometry, and their intracellular zinc concentration level and gene expression were examined. Functional recovery was assessed using the open field motor score, a foot print analysis, and a grid walk test. Statistical analysis was performed using Wilcoxon rank-sum test and ANOVA with the Tukey-Kramer test. Results: In macrophages after SCI, zinc deficiency promoted nuclear translocation of NF-κB, polarization to pro-inflammatory like phenotype and expression of pro-inflammatory cytokines. The inflammatory response exacerbated by zinc deficiency led to worsening motor function by inducing more apoptosis of oligodendrocytes and demyelination and inhibiting axonal regeneration in the lesion site compared to the normal zinc condition. Furthermore, zinc supplementation after SCI attenuated these zinc-deficiency-induced series of responses and improved motor function. Conclusion: We demonstrated that zinc affected axonal regeneration and motor functional recovery after SCI by negatively regulating NF-κB activity and the subsequent inflammatory response in macrophages. Our findings suggest that zinc supplementation after SCI may be a novel therapeutic strategy for SCI.

Macrophages play a leading role in determining the direction of astrocytic migration in spinal cord injury via ADP-P2Y1R axis.

After spinal cord injury (SCI), inflammatory cells such as macrophages infiltrate the injured area, and astrocytes migrate, forming a glial scar around macrophages. The glial scar inhibits axonal regeneration, resulting in significant permanent disability. However, the mechanism through which glial scar-forming astrocytes migrate to the injury site has not been clarified. Here we show that migrating macrophages attract reactive astrocytes toward the center of the lesion after SCI. Chimeric mice with bone marrow lacking IRF8, which controls macrophage centripetal migration after SCI, showed widely scattered macrophages in the injured spinal cord with the formation of a huge glial scar around the macrophages. To determine whether astrocytes or macrophages play a leading role in determining the directions of migration, we generated chimeric mice with reactive astrocyte-specific Socs3-/- mice, which showed enhanced astrocyte migration, and bone marrow from IRF8-/- mice. In this mouse model, macrophages were widely scattered, and a huge glial scar was formed around the macrophages as in wild-type mice that were transplanted with IRF8-/- bone marrow. In addition, we revealed that macrophage-secreted ATP-derived ADP attracts astrocytes via the P2Y1 receptor. Our findings revealed a mechanism through which migrating macrophages attract astrocytes and affect the pathophysiology and outcome after SCI.

Bone marrow-derived fibroblast migration via periostin causes irreversible arthrogenic contracture after joint immobilization.

Joint contracture causes distressing permanent mobility disorder due to trauma, arthritis, and aging, with no effective treatment available. A principal and irreversible cause of joint contracture has been regarded as the development of joint capsule fibrosis. However, the molecular mechanisms underlying contracture remain unclear. We established a mouse model of knee joint contracture, revealing that fibrosis in joint capsules causes irreversible contracture. RNA-sequencing of contracture capsules demonstrated a marked enrichment of the genes involved in the extracellular region, particularly periostin (Postn). Three-dimensional magnetic resonance imaging and immunohistological analysis of contracture patients revealed posterior joint capsule thickening with abundant type I collagen (Col1a2) and POSTN in humans. Col1a2-GFPTG ; Postn-/- mice and chimeric mice with Col1a2-GFPTG ; tdTomatoTG bone marrow showed fibrosis in joint capsules caused by bone marrow-derived fibroblasts, and POSTN promoted the migration of bone marrow-derived fibroblasts, contributing to fibrosis and contracture. Conversely, POSTN-neutralizing antibody attenuated contracture exacerbation. Our findings identified POSTN as a key inducer of fibroblast migration that exacerbates capsule fibrosis, providing a potential therapeutic strategy for joint contracture.

Vitamin D status-associated postoperative complications in patients with hip dysplasia after periacetabular osteotomy: A case-control study.

OBJECTIVES: This study aimed to clarify the relationship between vitamin D status and complications after periacetabular osteotomy. METHODS: A total of 46 hips of 39 patients (3 men and 36 women; mean age at surgery, 41.0 years; mean postoperative follow-up duration, 63 months) were reviewed to obtain the following information: patients' serum 25-hydroxyvitamin D [25(OH)D] status, prevalence of postoperative delayed union of osteotomy sites in the greater trochanter (DUGT) and ischiopubic stress fractures (IPSFs), and risk factors. RESULTS: The mean serum 25(OH)D level was 11.9 ng/ml. DUGT and IPSF were found in four (10.3%) and three (7.7%) patients, respectively. Serum 25(OH)D levels ≤ 11 ng/ml were significantly associated with DUGT in female patients (p = .02). Serum 25(OH)D levels ≤ 9 ng/ml and smoking were significantly associated with IPSF (p = 0.01 and 0.02, respectively). Overall, 21.7% of patients with serum 25(OH)D levels ≤ 11 ng/ml developed at least one complication; no complications occurred when serum 25(OH)D levels were >11 ng/ml. CONCLUSION: Severe vitamin D deficiency was highly prevalent in relatively young patients. Vitamin D deficiency and smoking were independent risk factors for postoperative complications. Proactive supplementation is advisable to reduce postoperative complications, especially in patients with serum 25(OH)D levels ≤ 11 ng/ml.

Zinc chelator treatment in crush syndrome model mice attenuates ischemia-reperfusion-induced muscle injury due to suppressing of neutrophil infiltration.

In crush syndrome, massive muscle breakdown resulting from ischemia-reperfusion muscle injury can be a life-threatening condition that requires urgent treatment. Blood reperfusion into the ischemic muscle triggers an immediate inflammatory response, and neutrophils are the first to infiltrate and exacerbate the muscle damage. Since free zinc ion play a critical role in the immune system and the function of neutrophils is impaired by zinc depletion, we hypothesized that the administration of a zinc chelator would be effective for suppressing the inflammatory reaction at the site of ischemia-reperfusion injury and for improving of the pathology of crush syndrome. A crush syndrome model was created by using a rubber tourniquet to compress the bilateral hind limbs of mice at 8 weeks. A zinc chelator N,N,N',N'-tetrakis-(2-pyridylmethyl)-ethylenediamine (TPEN) was administered immediately after reperfusion in order to assess the anti-inflammatory effect of the chelator for neutrophils. Histopathological evaluation showed significantly less muscle breakdown and fewer neutrophil infiltration in TPEN administration group compared with control group. In addition, the expression levels of inflammatory cytokine and chemokine such as IL-6, TNFα, CXCL1, CXCL2, CXCR2, CCL2 in ischemia-reperfusion injured muscle were significantly suppressed with TPEN treatment. Less dilatation of renal tubules in histological evaluation in renal tissue and significantly better survival rate were demonstrated in TPEN treatment for ischemia-reperfusion injury in crush syndrome. The findings of our study suggest that zinc chelators contributed to the resolution of exacerbation of the inflammatory response and attenuation of muscle breakdown in the acute phase after crush syndrome. In addition, our strategy of attenuation of the acute inflammatory reaction by zinc chelators may provide a promising therapeutic strategy not only for crush syndrome, but also for other diseases driven by inflammatory reactions.

Epidural Fat Tissue Is More Effective for Scar Prevention Than Conventional Subcutaneous Fat Grafting After Laminectomy in a Mouse Model.

STUDY DESIGN: Basic science study. OBJECTIVE: The aim of this study was to examine whether epidural fat tissue (EFT) transplantation can prevent epidural adhesion after laminectomy more efficiently than subcutaneous fat tissue (SFT) transplantation. SUMMARY OF BACKGROUND DATA: Epidural adhesion is almost inevitable after laminectomy. Although many materials have been used to prevent adhesion, none has been widely accepted. As EFT is an ectopic fat tissue located on the dura mater and there is no adhesion between EFT and the dura mater, we focused on the efficacy of EFT for adhesion prevention. METHODS: We examined the differences in histology and gene expression between EFT and SFT of mice. We performed laminectomy at the 10th thoracic level and immediately transplanted EFT or SFT to the dura mater in mice. At 6 weeks after transplantation, we performed histological and gene expression analyses and evaluated the adhesion tenacity. In addition, we examined the characteristic differences between human EFT and SFT. RESULTS: The adipocytes of EFT were significantly smaller than those of SFT in mice and humans. The gene expression of inflammatory cytokine and fibrosis-related factors was significantly higher in SFT than in EFT. At 6 weeks after transplantation, the percentage of the remaining fat area over the dura mater was significantly greater in the EFT group than in SFT group, and the adhesion tenacity score was significantly lower in the EFT group than that in the SFT group. An RNA sequencing analysis revealed 1921 differentially expressed genes (DEGs) between human EFT and SFT, and a Gene Ontology term associated with the inflammatory response was most highly enriched in SFT. CONCLUSION: EFT has different molecular and histological profiles from SFT and EFT grafting is more effective for epidural adhesion prevention than conventional SFT transplantation after laminectomy in a mouse model.Level of Evidence: N/A.

Risk Factors of Periprosthetic Infection in Patients with Tumor Prostheses Following Resection for Musculoskeletal Tumor of the Lower Limb.

Tumor prostheses for the lower limb following resection of musculoskeletal tumors is useful limb salvage management; however, as compared with routine total joint replacement, an increased incidence of deep periprosthetic infection of tumor prosthesis has been observed. The risk factors for periprosthetic infection of tumor prosthesis remain unclear. This study examines the risk factors and outcomes of periprosthetic infection. This was a retrospective observational study including 121 patients (67 males and 54 females) who underwent tumor prosthesis of the lower limb after resection of musculoskeletal tumors between 1 January 2000 and 30 November 2018. Among a total of 121 tumor prostheses, 7 were total femurs, 47 were proximal femurs, 47 were distal femurs, and 20 were proximal tibias. The incidence of postoperative infection and its risk factors were analyzed. Forty-five patients (37%) had osteosarcoma, 36 patients (30%) had bone metastasis, and 10 patients (8%) had soft-tissue tumors invading the bone. The mean operating time was 229 min, and the mean follow-up duration was 5.9 years. Deep periprosthetic infection was noted in 14 patients (12%). In the multivariate analysis, the risk factors for postoperative infection were identified as being male (hazard ratio [HR], 11.2316; p = 0.0100), soft-tissue tumor (HR, 52.2443; p = 0.0003), long operation (HR, 1.0056; p = 0.0184), and radiotherapy (HR, 6.5683; p = 0.0476). The incidence of periprosthetic infection in our institution was similar to that of previous reports. Patients undergoing tumor prosthesis of the lower limb who were male, had a soft-tissue tumor, were predicted to have a long operation, and who underwent radiation, had an increased possibility of postoperative infection.