S100 Calcium Binding Protein A9 Represses Angiogenic Activity and Aggravates Osteonecrosis of the Femoral Head

MicroRNA-29a Mitigates Laminectomy-Induced Spinal Epidural Fibrosis and Gait Dysregulation by Repressing TGF-β1 and IL-6

Spinal epidural fibrosis is one of the typical features attributable to failed back surgery syndrome, with excessive scar development in the dura and nerve roots. The microRNA-29 family (miR-29s) has been found to act as a fibrogenesis-inhibitory factor that reduces fibrotic matrix overproduction in various tissues. However, the mechanistic basis of miRNA-29a underlying the overabundant fibrotic matrix synthesis in spinal epidural scars post-laminectomy remained elusive. This study revealed that miR-29a attenuated lumbar laminectomy-induced fibrogenic activity, and epidural fibrotic matrix formation was significantly lessened in the transgenic mice (miR-29aTg) as compared with wild-type mice (WT). Moreover, miR-29aTg limits laminectomy-induced damage and has also been demonstrated to detect walking patterns, footprint distribution, and moving activity. Immunohistochemistry staining of epidural tissue showed that miR-29aTg was a remarkably weak signal of IL-6, TGF-β1, and DNA methyltransferase marker, Dnmt3b, compared to the wild-type mice. Taken together, these results have further strengthened the evidence that miR-29a epigenetic regulation reduces fibrotic matrix formation and spinal epidural fibrotic activity in surgery scars to preserve the integrity of the spinal cord core. This study elucidates and highlights the molecular mechanisms that reduce the incidence of spinal epidural fibrosis, eliminating the risk of gait abnormalities and pain associated with laminectomy.

The Antagonism of Neuropeptide Y Type I Receptor (Y1R) Reserves the Viability of Bone Marrow Stromal Cells in the Milieu of Osteonecrosis of Femoral Head (ONFH)

Neuropeptide Y (NPY)-Y1 receptor (Y1R) signaling is known to negatively affect bone anabolism. Our study aimed at investigating the impact of NPY-Y1R signaling in the pathogenesis of glucocorticoid-related osteonecrosis of the femoral head (ONFH). Femoral heads were retrieved from 20 patients with and without ONFH, respectively. The bone marrow stromal cells (BMSCs) from ONFH femoral heads were treated with Y1R agonists and antagonists for subsequent analysis. We showed that the local NPY expression level was lower in ONFH heads. The Y1R agonists and antagonists disturb and facilitate the survival of BMSCs. The transcription of stromal derived factor-1 (SDF-1) was enhanced by Y1R antagonists. Our study showed that the local NPY expression level was lower in ONFH heads. Y1R antagonists facilitate the survival of BMSCs and stimulate the transcription of SDF-1 by BMSCs. These findings shed light on the role of NPY-Y1R signaling in the pathogenesis of ONFH.

Osteogenesis-Related Long Noncoding RNA GAS5 as a Novel Biomarker for Osteonecrosis of Femoral Head

Background: The lack of effective biomarkers makes it difficult to achieve early diagnosis and intervention for osteonecrosis of the femoral head (ONFH). Hence, we aimed to identify novel long noncoding RNA (lncRNA) biomarkers for ONFH.

Methods: High-throughput RNA sequencing was performed to detect lncRNA and mRNA expression levels in subchondral bone samples from three patients with ONFH and three patients with femoral neck fractures. Integrated bioinformatics analyses were conducted to identify lncRNAs associated with ONFH development and their potential functions and signaling pathways. A co-expression network was constructed based on the gene time-series expression data in GSE113253. After selecting lncRNA GAS5 as a novel biomarker for ONFH, bone marrow mesenchymal stem cell (BMSC) osteogenic differentiation assays were performed to verify the association between lncRNA GAS5 and osteogenic differentiation. Alkaline phosphatase (ALP) staining and quantitative reverse transcription polymerase chain reaction (RT-qPCR) were used to measure the osteogenic phenotype and lncRNA GAS5 expression. Finally, for further validation, ONFH rat models were established, and lncRNA GAS5 expression in subchondral bone was detected by RT-qPCR.

Results: We identified 126 and 959 differentially expressed lncRNAs and genes, respectively. lncRNA GAS5 expression level was significantly downregulated in patients with ONFH compared to the control group patients. The BMSC osteogenic differentiation assays showed that ALP activity increased gradually from days 3 to 7, while the lncRNA GAS5 expression level was significantly upregulated in the osteogenic differentiation induction groups. Furthermore, in vivo experiments suggested that the bone volume/tissue volume value and trabecular thickness significantly decreased in the ONFH rat model group compared to the control group, whereas the trabecular space significantly increased in the ONFH group compared to the control group. In addition, the lncRNA GAS5 expression level significantly decreased in the ONFH rat model group.

Conclusion: The lncRNA GAS5 expression level was highly associated with BMSC osteogenic differentiation and was significantly downregulated in both the subchondral trabecular bone tissue of ONFH patients and ONFH rat models. Therefore, lncRNA GAS5 can serve as an ONFH osteogenic biomarker to provide an effective target for early diagnosis and molecular therapy of ONFH.

Mesenchymal stem cells-derived and siRNAs-encapsulated exosomes inhibit osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a progressive, obstinate and disabling disease. At present, the treatment of ONFH is still a global medical problem. We aim to explore the role of bone mesenchymal stem cells (BMSCs)‐derived and siRNAs‐encapsulated exosomes (siRNAs‐encapsulated BMSCexos) in ONFH. We first isolated BMSCexos and screened siRNAs of 6 ONFH‐related genes for siRNAs‐encapsulated BMSCexo. The expression of these 6 ONFH‐related genes in dexamethasone (DXM)‐treated MC3T3‐E1 cell, cell model of ONFH, was detected by RT‐qPCR and Western blot analysis. And then, we performed CCK‐8 assay, angiogenesis assay and HE staining analysis to test the promotion role of the siRNAs‐encapsulated BMSCexo for angiogenesis during ONFH repair. The results suggest that the obtained particles were BMSCexos. The screened effective siRNAs could effectively knock down their expression in VECs. Moreover, siRNAs‐encapsulated BMSCexo could effectively knock down the expression of these genes in VECs. In addition, siRNAs‐encapsulated BMSCexo promote angiogenesis during ONFH repair. In conclusion, we found siRNAs‐encapsulated BMSCexos could promote ONFH repair by angiogenesis, and indicated exosome as the new siRNA carrier is of great significance to improve the efficiency of RNAi.

CD41-deficient exosomes from non-traumatic femoral head necrosis tissues impair osteogenic differentiation and migration of mesenchymal stem cells

Non-traumatic osteonecrosis of the femoral head (ONFH) is clinically a devastating and progressive disease without an effective treatment. Mesenchymal stem cells (MSCs) transplantation has been used to treat ONFH in early stage, but the failure rate of this therapy is high due to the reduced osteogenic differentiation and migration of the transplanted MSCs related with pathological bone tissues. However, the mechanism responsible for this decrease is still unclear. Therefore, we assume that the implanted MSCs might be influenced by signals delivered from pathological bone tissue, where the exosomes might play a critical role in this delivery. This study showed that exosomes from ONFH bone tissues (ONFH-exos) were able to induce GC-induced ONFH-like damage, in vivo and impair osteogenic differentiation and migration of MSCs, in vitro. Then, we analyzed the differentially expressed proteins (DEPs) in ONFH-exos using proteomic technology and identified 842 differentially expressed proteins (DEPs). On the basis of gene ontology (GO) enrichment analysis of DEPs, fold-changes and previous report, cell adhesion-related CD41 (integrin α2b) was selected for further investigation. Our study showed that the CD41 (integrin α2b) was distinctly decreased in ONFH-exos, compared to NOR-exos, and downregulation of CD41 could impair osteogenic differentiation and migration of the MSCs, where CD41-integrin β3-FAK-Akt-Runx2 pathway was involved. Finally, our study further suggested that CD41-affluent NOR-exos could restore the glucocorticoid-induced decline of osteogenic differentiation and migration in MSCs, and prevent GC-induced ONFH-like damage in rat models. Taken together, our study results revealed that in the progress of ONFH, exosomes from the pathological bone brought about the failure of MSCs repairing the necrotic bone for lack of some critical proteins, like integrin CD41, and prompted the progression of experimentally induced ONFH-like status in the rat. CD41 could be considered as the target of early diagnosis and therapy in ONFH.