Biomimetic Structural Protein Based Magnetic Responsive Scaffold for Enhancing Bone Regeneration by Physical Stimulation on Intracellular Calcium Homeostasis.

The bone matrix has distinct architecture and biochemistry which present a barrier to synthesizing bone-mimetic regenerative scaffolds. To mimic the natural structures and components of bone, biomimetic structural decellularized extracellular matrix (ECM)/regenerated silk fibroin (RSF) scaffolds incorporated with magnetic nanoparticles (MNP) are prepared using a facile synthetic methodology. The ECM/RSF/MNP scaffold is a hierarchically organized and interconnected porous structure with silk fibroin twined on the collagen nanofibers. The scaffold demonstrates saturation magnetization due to the presence of MNP, along with good cytocompatibility. Moreover, the ß-sheet crystalline domain of RSF and the chelated MNP could mimic the deposition of hydroxyapatite and enhance compressive modulus of the scaffold by ≈20%. The results indicate that an external static magnetic field (SMF) with a magnetic responsive scaffold effectively promotes cell migration, osteogenic differentiation, neogenesis of endotheliocytes in vitro, and new bone formation in a critical-size femur defect rat model. RNA sequencing reveals that the molecular mechanisms underlying this osteogenic effect involve calsequestrin-2-mediated Ca2+ release from the endoplasmic reticulum to activate Ca2+ /calmodulin/calmodulin-dependent kinase II signaling axis. Collectively, bionic magnetic scaffolds with SMF stimulation provide a potent strategy for bone regeneration through internal structural cues, biochemical composition, and external physical stimulation on intracellular Ca2+ homeostasis.

CX3CL1 in the red bone marrow promotes renal cell carcinoma to metastasize to the spine by involving the Src-related pathway.

Spinal metastasis (SM) frequently occurs in renal cell carcinoma (RCC) patients. Our preliminary work showed that CX3CL1 plays a positive role in SM. The objective of the present study was to verify whether CX3CL1 activates the downstream pathway by binding to CX3CR1 in RCC cells, ultimately promoting RCC to metastasize to the spine. The expression of CX3CL1 and CX3CR1 in tissue samples was detected by immunohistochemistry and western blotting. ELISA was used to quantify the concentration of CX3CL1 in the serum. The expression level of CX3CR1 in RCC cell lines was also detected. The CellTiter-Glo assay and flow cytometry were used to analyze cell viability and apoptosis of RCC cells. Transwell and wound healing assay were used to analyze the effect of CX3CL1 on the invasion and migration ability of RCC cells. Specific inhibitors were used to interfere with key molecules in the signaling pathway to further explore the signal transduction in RCC cells after CX3CL1 stimulation. The expression of CX3CR1 in SM from RCC was higher than that in limb bone metastases. Among the five RCC cell lines, 786O cells expressed the highest level of CX3CR1. CX3CL1 neither inhibited the proliferation of 786O cells nor promoted the apoptosis of 786O cells. However, it promoted the migration and invasion of RCC cells. After CX3CL1 stimulation, Src and Focal adhesion kinase (FAK) phosphorylation levels increased in RCC cells. Bosutinib and PF-00562271 inhibited Src/FAK phosphorylation and cell motility and invasion triggered by CX3CL1 stimulation. CX3CL1 in the red bone marrow of spinal cancellous bone enhances migration and invasion abilities of RCC cells, thereby promoting RCC metastasize to the spine. The migration and invasion of RCC cells activated by CX3CL1 are at least partially dependent on Src/FAK activation.

Autophagy-activated nucleus pulposus cells deliver exosomal miR-27a to prevent extracellular matrix degradation by targeting MMP-13.

Although autophagy may be beneficial for maintaining the metabolic balance of the extracellular matrix (ECM) in the nucleus pulposus (NP) and its vitality under inflammation, the underlying mechanism still remains unclear. A previous study found that autophagy activation stimulated the release of exosomes in normal chondrocytes, which are located in a similar avascular environment and share many common features with those of nucleus pulposus cells (NPCs). This study explored the protective effect on matrix degradation in the NP by exosomes derived from autophagy-activated NPCs and exosomal microRNAs. NPCs-derived exosomes (NPCs-Exos) were isolated from culture medium of either normal NPCs or rapamycin-treated NPCs and quantified by nanoparticle tracking analysis. The effect of rapamycin-treated NPC-derived exosomes on NPCs were assessed by coculture with interleukin 1ß (IL-1ß)-stimulated NPCs. After examination of six major proteinases of the ECM, matrix metalloproteinase 13 (MMP-13) was chosen for further study. miR-27a, which targets MMP-13, was investigated through previous studies and bioinformatics tool. The levels of miR-27a were upregulated in both rapamycin-treated NPCs and their exosomes, compared to the control. When exosomal miR-27a was transferred into NPCs, it alleviated IL-1ß-induced degradation of the NPC ECM by targeting MMP-13. Autophagy activation may promote the release of NPCs-derived exosomes and thereby prevent the NPC matrix from degradation. Autophagy activation also alleviates intervertebral disc degeneration (IDD), at least partly via exosomal miR-27a, which restrains MMP-13 expression under IL-1ß stimulation. Our work elucidates a new mechanism for how autophagy may participate in preventing IDD, which may be a promising therapeutic strategy.

Autophagy regulates exosome secretion in rat nucleus pulposus cells via the RhoC/ROCK2 pathway.

Our present study investigated whether exosome secretion of nucleus pulposus cells (NPCs) is regulated by autophagy. Different autophagic states of NPCs were induced by rapamycin (Rap), bafilomycin A1 (Baf) and other agents, and it was found that exosomes were secreted in an autophagy-dependent manner. Activation or inhibition of autophagy increased or decreased, respectively, the amount of exosomes that were released into the extracellular space. In addition, in order to confirm that Rap-promoted release of exosomes was mediated by autophagy rather than other pathways, we used autophagy associated gene 5 (ATG5) small-interfering RNA (siRNA) to silence the expression of ATG5 gene, which is indispensable for autophagy. The results showed that siRNA against ATG5 (siATG5) induced an accumulation of intraluminal vesicles (ILVs) in NPCs and a concomitant decrease in the amount of exosomes isolated from supernatant. Ras homolog gene (Rho) and Rho-associated coiled-coil forming protein kinase (ROCK) family molecules are capable of cytoskeletal remodeling and affecting vesicle transport. Therefore, we carried out targeted interventions and evaluated the effects of the RhoC/ROCK2 pathway on the secretion of exosomes within autophagic environment. Knockdown of RhoC and ROCK2 with corresponding siRNA significantly inhibited the secretion of exosomes originating from ILVs in NPCs, even when NPCs were subsequently treated with Rap. Taken together, our findings suggest that autophagy positively regulates expression levels of RhoC and ROCK2, and that the RhoC/ROCK2 pathway exerts a key function on NPCs-derived exosome secretion.

Hsa_circ_0006571 promotes spinal metastasis through sponging microRNA-138 to regulate sirtuin 1 expression in lung adenocarcinoma.

BACKGROUND: Circular RNAs (circRNAs) are known to participate in lung cancer. However, their role in spinal metastasis (SM) of lung adenocarcinoma remains elusive. In this study, we determined that hsa_circ_0006571 serves as a sponge for miR-138, which targets sirtuin 1 (Sirt1) in the development of SM. METHODS: A human circRNA microarray was performed to compare SM and lung adenocarcinoma samples. The expression of hsa_circ_0006571 and miR-138 was determined using quantitative polymerase chain reaction (qPCR) in vitro and in vivo. Cell proliferation was performed by Cell Counting Kit-8 (CCK-8) and apoptosis was analyzed by Annexin V/PI staining. RNA-pulldown and RNA immunoprecipitation (RIP) were used to analyze the interaction between hsa_circ_0006571. Tumor metastasis was determined through a xenograft experiment in vivo. RESULTS: Hsa_circ_0006571 was observed to be significantly upregulated in SM tissues through circRNA microarray and qPCR. We detected a lower expression of miR-138 in SM tissues compared with lung adenocarcinoma. Hsa_circ_0006571 silencing suppressed lung cancer cell proliferation and migration while promoting apoptosis. Hsa_circ_0006571 interacted with miR-138 to promote expression of Sirt1, leading to activation of epithelial-mesenchymal transition (EMT). Xenograft experiments showed that downregulation of hsa_circ_0006571 delayed the SM of lung adenocarcinoma cells via the miR-138-Sirt1 axis. CONCLUSIONS: Hsa_circ_0006571 promoted tumor cell migration and invasion via the miR-138/Sirt1 pathway. Our observations indicate that circRNAs are possible novel therapeutic targets for SM of lung adenocarcinoma.

Value of CT-guided Core Needle Biopsy in Diagnosing Spinal Lesions: A Comparison Study.

OBJECTIVE: A retrospective study was designed to evaluate the effectiveness of CT-guided core needle biopsy in diagnosing spinal lesions through comparison with C-arm guidance. METHODS: From April 2013 to July 2017, a total of 188 patients, who suffered from spinal lesions or had malignant tumor history with a new spinal fracture, were included in this study. There were 96 men and 92 women, with an average of 57.1 years. A total of 238 core needle biopsies were performed. A total of 140 core needle biopsies were carried out under C-arm guidance in 102 patients (group 1); 98 core needle biopsies were carried out under CT guidance in 86 patients (group 2); 108 core needle biopsies were performed in thoracic vertebrae, 116 were in lumbar vertebrae, and 14 were in sacral vertebrae. Seventy-eight patients accepted surgical treatment after biopsies. For these patients, the histological pathologies of the biopsy and surgery were compared to evaluate the accuracy of the biopsy. For the other 110 patients who did not receive surgical treatment, the treatment response and the clinical course were used to evaluate the accuracy of the biopsy. The success rate, the diagnostic accuracy rate, the true positive/negative rate, and complications of the two groups were calculated and compared. RESULTS: There were no significant differences in sex, age, and lesion sites between the C-arm guidance group (group 1) and the CT guidance group (group 2). There were no complications in the two groups. Pathological diagnoses were established in 232 of 238 biopsies. They revealed that 52 were primary malignant tumors, 12 were benign tumors, 70 were metastatic tumors, 4 were tuberculosis, and 94 were classified as "other." The success rate of group 2 was higher than that of group 1, but it was not statistically significant (95.7% vs 100%; P = 0.098). According to the final diagnosis, the diagnostic accuracy rates were calculated and compared. There was no significant difference between the two groups (95.5% vs 96.9%; P = 0.835). The kappa coefficient was used to analyze the concordance between the histological pathologies of the biopsy and the final diagnosis in the two groups. The kappa values of the two group were 0.909 and 0.939, respectively. The results showed good consistency in both groups, but seemed better for group 2. CONCLUSION: CT-guided core needle biopsy is a relatively safe and effective procedure for diagnosing spinal lesions with a high diagnostic accuracy rate and few complications.

Learning curves of percutaneous endoscopic lumbar discectomy in transforaminal approach at the L4/5 and L5/S1 levels: a comparative study.

OBJECTIVES: This study aimed to compare the learning curves of percutaneous endoscopic lumbar discectomy (PELD) in a transforaminal approach at the L4/5 and L5/S1 levels. METHODS: We retrospectively reviewed the first 60 cases at the L4/5 level (Group I) and the first 60 cases at the L5/S1 level (Group II) of PELD performed by one spine surgeon. The patients were divided into subgroups A, B, and C (Group I: A cases 1-20, B cases 21-40, C cases 41-60; Group II: A cases 1-20, B cases 21-40, C cases 41-60). Operation time was thoroughly analyzed. RESULTS: Compared with the L4/5 level, the learning curve of transforaminal PELD at the L5/S1 level was flatter. The mean operation times of Groups IA, IB, and IC were (88.75±17.02), (67.75±6.16), and (64.85±7.82) min, respectively. There was a significant difference between Groups A and B (P<0.05), but no significant difference between Groups B and C (P=0.20). The mean operation times of Groups IIA, IIB, and IIC were (117.25±13.62), (109.50±11.20), and (92.15±11.94) min, respectively. There was no significant difference between Groups A and B (P=0.06), but there was a significant difference between Groups B and C (P<0.05). There were 6 cases of postoperative dysesthesia (POD) in Group I and 2 cases in Group IIA (P=0.27). There were 2 cases of residual disc in Group I, and 4 cases in Group II (P=0.67). There were 3 cases of recurrence in Group I, and 2 cases in Group II (P>0.05). CONCLUSIONS: Compared with the L5/S1 level, the learning curve of PELD in a transforaminal approach at the L4/5 level was steeper, suggesting that the L4/5 level might be easier to master after short-term professional training.