Fibroblasts inhibit osteogenesis by regulating nuclear-cytoplasmic shuttling of YAP in mesenchymal stem cells and secreting DKK1.

BACKGROUND: Fibrous scars frequently form at the sites of bone nonunion when attempts to repair bone fractures have failed. However, the detailed mechanism by which fibroblasts, which are the main components of fibrous scars, impede osteogenesis remains largely unknown. RESULTS: In this study, we found that fibroblasts compete with osteogenesis in both human bone nonunion tissues and BMP2-induced ectopic osteogenesis in a mouse model. Fibroblasts could inhibit the osteoblastic differentiation of mesenchymal stem cells (MSCs) via direct and indirect cell competition. During this process, fibroblasts modulated the nuclear-cytoplasmic shuttling of YAP in MSCs. Knocking down YAP could inhibit osteoblast differentiation of MSCs, while overexpression of nuclear-localized YAP-5SA could reverse the inhibition of osteoblast differentiation of MSCs caused by fibroblasts. Furthermore, fibroblasts secreted DKK1, which further inhibited the formation of calcium nodules during the late stage of osteogenesis but did not affect the early stage of osteogenesis. Thus, fibroblasts could inhibit osteogenesis by regulating YAP localization in MSCs and secreting DKK1. CONCLUSIONS: Our research revealed that fibroblasts could modulate the nuclear-cytoplasmic shuttling of YAP in MSCs, thereby inhibiting their osteoblast differentiation. Fibroblasts could also secrete DKK1, which inhibited calcium nodule formation at the late stage of osteogenesis.

Fibroblasts inhibit osteogenesis by regulating nuclear-cytoplasmic shuttling of YAP in mesenchymal stem cells and secreting DKK1

BACKGROUND: Fibrous scars frequently form at the sites of bone nonunion when attempts to repair bone fractures have failed. However, the detailed mechanism by which fibroblasts, which are the main components of fibrous scars, impede osteogenesis remains largely unknown. RESULTS: In this study, we found that fibroblasts compete with osteogenesis in both human bone nonunion tissues and BMP2-induced ectopic osteogenesis in a mouse model. Fibroblasts could inhibit the osteoblastic differentiation of mesenchymal stem cells (MSCs) via direct and indirect cell competition. During this process, fibroblasts modulated the nuclear-cytoplasmic shuttling of YAP in MSCs. Knocking down YAP could inhibit osteoblast differentiation of MSCs, while overexpression of nuclear-localized YAP-5SA could reverse the inhibition of osteoblast differentiation of MSCs caused by fibroblasts. Furthermore, fibroblasts secreted DKK1, which further inhibited the formation of calcium nodules during the late stage of osteogenesis but did not affect the early stage of osteogenesis. Thus, fibroblasts could inhibit osteogenesis by regulating YAP localization in MSCs and secreting DKK1. CONCLUSIONS: Our research revealed that fibroblasts could modulate the nuclear-cytoplasmic shuttling of YAP in MSCs, thereby inhibiting their osteoblast differentiation. Fibroblasts could also secrete DKK1, which inhibited calcium nodule formation at the late stage of osteogenesis.

[Application of a new universal locking anatomical plate in treatment of tibial plateau posterolateral column fractures].

Objective: To investigate the effectiveness of a new tibial plateau posterolateral column universal locking anatomical plate (hereinafter referred to as "new universal locking anatomical plate") in the treatment of tibial plateau posterolateral column fractures. Methods: Between October 2020 and December 2021, 14 patients with tibial plateau posterolateral column fracture were treated with a new universal locking anatomical plate. There were 7 males and 7 females with an average age of 59 years ranging from 29 to 75 years. There were 5 cases on the left side and 9 cases on the right side. The causes of injury included falling from height in 5 cases, traffic accident in 7 cases, and other injuries in 2 cases. The time from injury to operation ranged from 3 to 10 days, with an average of 6 days. According to Schatzker classification, there were 4 cases of type Ⅱ, 8 cases of type Ⅴ, and 2 cases of type Ⅵ. All fractures involved the posterolateral tibial plateau. Three column classification: two columns (anterolateral column+posterior column) in 4 cases, three columns in 10 cases. The operation time, intraoperative blood loss, fracture healing, and complications were recorded. The reduction of tibial plateau fracture was evaluated by Rasmussen radiographic score, and the recovery of knee function was evaluated by Hospital for Special Surgery (HSS) score. Results: All 14 cases completed the operation successfully. The operation time was 95-180 minutes, with an average of 154 minutes, and the intraoperative blood loss was 100-480 mL, with an average of 260 mL. All patients were followed up 6-19 months, with an average of 12.5 months. All fractures healed, and the healing time was 15-24 weeks, with an average of 18.7 weeks. During the follow-up, there was 1 case of common peroneal nerve palsy and 1 case of traumatic osteoarthritis. There was no other complication such as vascular injury, incision infection, deep venous thrombosis of lower limbs, heterotopic ossification, bone nonunion, and failure of internal fixation. The reduction of tibial plateau fractures was good immediately after operation, and the Rasmussen radiological score was 10-18, with an average of 15.7; 3 cases were excellent, 10 cases were good, and 1 case was fair, with an excellent and good rate of 92.9%. The scores and grades of HSS at 3 months after operation and at last follow-up significantly improved when compared with those before operation ( P<0.05). There was no significant difference between 3 months after operation and last follow-up ( P>0.05). Conclusion: For the fractures involving the posterolateral column of the tibial plateau, the new universal locking anatomical plate can provide strong fixation, satisfactory postoperative fracture reduction, and good recovery of knee function.

A minimally invasive bipolar surgical approach for the treatment of patellar fracture using the tension-band wiring technique.

Objective: Minimally invasive surgical techniques are becoming increasingly popular for the treatment of traumatic injuries. Although some minimally invasive techniques in the management of patellar fractures have been reported, the limited exposure in such methods may cause technical difficulties during surgery and restrict their wide application. In this context, this study aims to introduce a bipolar incision and assess the clinical outcomes of patellar fractures treated via this type of incision. Materials and methods: Patients who suffered patellar fractures and who received surgical treatment via bipolar incision between 2018 and 2020 in our hospital were retrospectively reviewed and included in this study. The clinical and radiological records of all patients were reviewed. A classification of the fractures was done and intraoperative parameters, Visual Analog Scale (VAS) score, knee range of motion, and the Hospital for Special Surgery (HSS) knee score of the patients were evaluated and summarized. Results: The study included 19 patients who met the inclusion criteria. All patellar fractures were operated through the minimally invasive bipolar surgical approach. The mean time of operation was 69.0 ± 8.5 min. The mean time to union was 12.8 ± 2.1 weeks. The average total knee range of motion was 131.8 ± 4.4°, and the average HSS score was 97.1 ± 2.6 at 1-year post-operation. No surgical-related complications were observed. Conclusions: The knee functional outcomes were favorable when patellar fractures were treated through the minimally invasive bipolar incision method. This bipolar surgical approach was found to be a feasible method for treating patellar fractures.

Platycodon D-induced A549 Cell Apoptosis through RRM1-Regulated p53/VEGF/ MMP2 Pathway.

BACKGROUND: Lung cancer is one of the leading causes of cancer-related deaths worldwide. Platycodin D (PD), a major pharmacological constituent from the Chinese medicinal herb named Platycodonis Radix, has shown potent anti-tumor activity. Also, it is reported that PD could inhibit cellular growth in the non-small-cell lung carcinoma (NSCLC) A549 cell line. However, the underlying mechanism is not fully clarified. METHODS: Cell proliferation was measured by MTT assay. Annexin V and propidium iodide (PI) assay were employed to study the apoptosis effects of PD on A549 cells. Western blot analysis was used to evaluate protein expression. Also, we used a siRNA against p53, as well as a plasmid-based RRM1 over-expression to investigate their functions. RESULTS: It is demonstrated that PD inhibited A549 cell proliferation in a dose- and time-dependent manner. Further investigations showed that PD induced cell apoptosis, which was supported by dose-dependent and time-dependent caspase-3 activation and p53/VEGF/MMP2 pathway regulation. Also, PD demonstrated the inhibition effect of ribonucleotide reductase M1 (RRM1), whose role in various tumors is contradictory. Remarkably, in this work, RRM1 overexpression in A549 cells could have a negative impact on the regulation of the p53/VEGF/MMP2 pathway induced by PD treatment. Note that RRM1 overexpression also attenuated cell apoptosis and inhibition of cell proliferation of A549 treated with PD. CONCLUSION: The results suggested that PD could inhibit A549 cell proliferation and induce cell apoptosis by regulating p53/VEGF/MMP2 pathway, in which RRM1 plays an important role directly.

Stattic sensitizes osteosarcoma cells to epidermal growth factor receptor inhibitors via blocking the interleukin 6-induced STAT3 pathway.

Osteosarcoma (OS), the most common malignant bone tumor with high metastatic potential, frequently affects children and adolescents. Epidermal growth factor receptor (EGFR)-targeted tyrosine kinase inhibitors exhibit encouraging anti-tumor activity for patients with solid tumors, whereas their effects on OS remain controversial. In the present study, we aimed to elucidate the anti-tumor activity of gefitinib for OS, as well as to explore the underlying mechanisms. Gefitinib inhibits cell viability, tumor growth, cell migration, and invasion and promotes cell apoptosis and G1 cycle arrest in OS at a relatively high concentration via suppressing the PI3K/Akt and ERK pathways. However, gefitinib treatment results in the feedback activation of signal transducer and activator of transcription 3 (STAT3) induced by interleukin 6 (IL-6) secretion. Combined treatment with gefitinib and stattic, an inhibitor for STAT3 phosphorylation, engenders more evident inhibitory effects on cell proliferation, migration, and invasion and promotive effects on cell apoptosis and G1 phase arrest in OS, compared with the single exposure to gefitinib or stattic. Western blot analysis demonstrates that stattic treatment in gefitinib-treated OS abrogates the IL-6-induced STAT3 activation and subsequently further restrains the activities of EGFR, Akt, and ERK pathways in tumor cells. This study confirms that the EGFR inhibitor of gefitinib has moderate anti-tumor effects on OS through IL-6 secretion-mediated STAT3 activation. Additional administration of stattic in EGFR-targeted therapies may contribute to improve the efficacy for OS.

Inhibition of BUB1 suppresses tumorigenesis of osteosarcoma via blocking of PI3K/Akt and ERK pathways.

Osteosarcoma (OS) is a primary malignant bone tumour that mainly affects teenagers, with patients displaying poor prognosis. Budding uninhibited by benzimidazoles 1 (BUB1), a type of serine/threonine kinase that is linked to pro-tumorigenic phenomena, has not been well studied in OS. Hence, this study aimed to explore the role of BUB1 in OS. The expression of BUB1 in OS specimens and cell lines was assessed using immunohistochemistry and Western blot analysis. Univariate and multivariate analyses were applied to evaluate the impact of BUB1 on patient survival. Cell counting kit-8, wound-healing and Transwell assays, as well as flow cytometry, were used to investigate the influence of BUB1 inhibition on OS in vitro. Moreover, a tumour xenograft model was established to investigate the in vivo effect of BUB1 inhibition on OS tumour growth. Results showed that BUB1 was overexpressed in OS specimens and cell lines. Furthermore, BUB1 overexpression was closely associated with the poor clinical outcomes of patients with OS. Inhibition of BUB1 markedly suppressed cell proliferation and tumour growth, cell migration, invasion and induced cell apoptosis of OS by blocking the PI3K/Akt and ERK signalling pathways. Thus, our study suggested that overexpression of BUB1 protein contributed to poor survival of OS patients and that inhibition of BUB1 resulted in considerable anti-tumour activity associated with proliferation, migration, invasion and apoptosis of OS.

[Indirect reduction technique via Nice knot for transverse fracture of patella].

OBJECTIVE: To assess the outcomes in indirect reduction technique via Nice knot for transverse patellar fractures. METHODS: The clinical data of 25 patients with transverse patellar fractures meeting the inclusion criteria between January 2017 and December 2018 were retrospectively analyzed. The patients were divided into trial group ( n=13) and control group ( n=12) according to different intraoperative reduction methods. No significant difference was found in gender, age, affected side, cause of fracture, classification, or the time from injury to operation between the two groups ( P>0.05). In the trial group, No.2 suture was used to cross the quadriceps tendon and patellar tendon to construct the Nice knot, then the suture was tightened to make the distal and proximal fracture segments contact in an indirect reduction pattern. Depend on Nice knot's sliding compression and self-stabilizing function, the suture mesh created an anterior tension band as a temporary fixation. In the control group, Weber's clamp was used to hold the fracture segments directly and fixed temporarily. After reduction, terminal fixation was conducted using a titanium Kirschner wire with titanium cable in both groups. The operation time, intraoperative blood loss, follow-up time, fracture healing time, and complications were recorded and compared in the two groups. At last follow-up, the knee function was evaluated according to the Böstman scoring criteria for efficacy in patellar fractures. RESULTS: The operation time in the trial group was significantly shorter than that in the control group ( t=-2.165, P=0.041). There was no significant difference of intraoperative blood loss between the two groups ( t=0.514, P=0.612). The incisions of the two groups healed by first intention. All the patients were followed up 12-16 months, with an average of 14.4 months, no significant difference was found in the follow-up time between the two groups ( t=-0.309, P=0.760). One patient in the control group developed soft tissue irritation symptoms at 1 day after operation, and no special treatment was given, the symptoms disappeared at 2 months after operation. The fractures of the two groups healed at the 12-week follow-up. During the follow-up, there was no complication such as loosening and fracture of titanium cables and tendon tissue calcification. At last follow-up, the Böstman score presented no significant difference between the two groups ( t=-0.086, P=0.932). In the trial group, an 80-year-old female patient was evaluated as good (score, 27) due to atrophy of the quadriceps femoris, leg weakness, and affected stair climbing, and the rest 24 patients were all evaluated as excellent. CONCLUSION: The indirect reduction with Nice knot can shorten the operation time in the treatment of transverse patellar fractures, and obtain good effectiveness.

Sulfiredoxin-1 protects spinal cord neurons against oxidative stress in the oxygen-glucose deprivation/reoxygenation model through the bax/cytochrome c/caspase 3 apoptosis pathway.

BACKGROUND: Spinal cord ischemia/reperfusion injury is a common clinical, pathophysiological phenomenon with complex molecular mechanisms. Currently, there are no therapeutics available to alleviate the same. This study investigates the protective effects of sulfiredoxin-1 (Srxn 1) on spinal cord neurons following exposure to oxygen-glucose deprivation/reoxygenation (OGD/R) treatment. MATERIALS AND METHODS: Primary spinal cord neurons were cultured, detected by anti-tubulin ßⅢ, and transfected with adeno-associated virus (AAV)-Srxn 1 to overexpress Srxn 1. They were identified by their morphology and CCK-8 assay. The superoxide dismutase level was measured by superoxide dismutase assay. Malondialdehyde level was measured by malondialdehyde assay. The apoptosis ratio was calculated by Hoechst 33342 and Annexin V-PE/7-AAD staining. Mitochondrial transmembrane potential (Δψm) was detected by tetramethylrhodamine-methyl ester-perchlorate (TMRM) staining. The mRNA expression levels of Srxn 1 and caspase 3 were detected by quantitative reverse transcription-polymerase chain reaction, and the protein expression levels of Srxn 1, bax, bcl-2, cytosolic cytochrome c, and caspase 3 were detected by western blotting. RESULTS: AAV-Srxn 1 up-regulated mRNA and protein levels of Srxn 1 in spinal cord neurons. Following exposure to OGD/R, overexpression of Srxn 1 improved the neuronal viability, alleviated the neuron apoptosis, enhanced the mitochondrial transmembrane potential, increased the SOD level, decreased the MDA level, inhibited the expression of cytosolic cytochrome c, bax, and caspase 3, and promoted the expression of bcl-2. CONCLUSION: Srxn 1 plays a significant role in anti-apoptosis of spinal cord neurons, and Srxn 1 may be a potential therapeutic target for spinal cord I/R injury.

Transplantation of a Peripheral Nerve with Neural Stem Cells Plus Lithium Chloride Injection Promote the Recovery of Rat Spinal Cord Injury.

Transplantation of neural stem cells (NSCs) holds great potential for the treatment of spinal cord injury (SCI). However, transplanted NSCs poorly survive in the SCI environment. We injected NSCs into tibial nerve and transplanted tibial nerve into a hemisected spinal cord and investigated the effects of lithium chloride (LiCl) on the survival of spinal neurons, axonal regeneration, and functional recovery. Our results show that most of the transplanted NSCs expressed glial fibrillary acidic protein, while there was no obvious expression of nestin, neuronal nuclei, or acetyltransferase found in NSCs. LiCl treatment produced less macrosialin (ED1) expression and axonal degeneration in tibial nerve after NSC injection. Our results also show that a regimen of LiCl treatment promoted NSC differentiation into NF200-positive neurons with neurite extension into the host spinal cord. The combination of tibial nerve transplantation with NSCs and LiCl injection resulted in more host motoneurons surviving in the spinal cord, more regenerated axons in tibial nerve, less glial scar area, and decreased ED1 expression. We conclude that lithium may have therapeutic potential in cell replacement strategies for central nervous system injury due to its ability to promote survival and neuronal generation of grafted NSCs and reduced host immune reaction.

Heme Oxygenase-1 Inhibits Neuronal Apoptosis in Spinal Cord Injury through Down-Regulation of Cdc42-MLK3-MKK7-JNK3 Axis.

The mechanism by which spinal cord injury (SCI) induces neuronal death has not been thoroughly understood. Investigation on the molecular signal pathways involved in SCI-mediated neuronal apoptosis is important for development of new therapeutics for SCI. In the current study, we explore the role of heme oxygenase-1 (HO-1) in the modulation of mixed lineage kinase 3/mitogen-activated protein kinase kinase/cJUN N-terminal kinase 3 (MLK3/MKK7/JNK3) signaling, which is a pro-apoptotic pathway, after SCI. We found that MLK3/MKK7/JNK3 signaling was activated by SCI in a time-dependent manner, demonstrated by increase in activating phosphorylation of MLK3, MKK7, and JNK3. SCI also induced HO-1 expression. Administration of HO-1-expressing adeno-associated virus before SCI introduced expression of exogenous HO-1 in injured spinal cords. Exogenous HO-1 reduced phosphorylation of MLK3, MKK7, and JNK3. Consistent with its inhibitory effect on MLK3/MKK7/JNK3 signaling, exogenous HO-1 decreased SCI-induced neuronal apoptosis and improved neurological score. Further, we found that exogenous HO-1 inhibited expression of cell division cycle 42 (Cdc42), which is crucial for MLK3 activation. In vitro experiments indicated that Cdc42 was essential for neuronal apoptosis, while transduction of neurons with HO-1-expressing adeno-associated virus significantly reduced neuronal apoptosis to enhance neuronal survival. Therefore, our study disclosed a novel mechanism by which HO-1 exerted its neuroprotective efficacy. Our discovery might be valuable for developing a new therapeutic approach for SCI.

Heme oxygenase-1 protects spinal cord neurons from hydrogen peroxide-induced apoptosis via suppression of Cdc42/MLK3/MKK7/JNK3 signaling.

The mechanisms by which oxidative stress induces spinal cord neuron death has not been completely understood. Investigation on the molecular signal pathways involved in oxidative stress-mediated neuronal death is important for development of new therapeutics for oxidative stress-associated spinal cord disorders. In current study we examined the role of heme oxygenase-1 (HO-1) in the modulation of MLK3/MKK7/JNK3 signaling, which is a pro-apoptotic pathway, after treating primary spinal cord neurons with H2O2. We found that MLK3/MKK7/JNK3 signaling was substantially activated by H2O2 in a time-dependent manner, demonstrated by increase of activating phosphorylation of MLK3, MKK7 and JNK3. H2O2 also induced expression of HO-1. Transduction of neurons with HO-1-expressing adeno-associated virus before H2O2 treatment introduced expression of exogenous HO-1 in neurons. Exogenous HO-1 reduced phosphorylation of MLK3, MKK7 and JNK3. Consistent with its inhibitory effect on MLK3/MKK7/JNK3 signaling, exogenous HO-1 decreased H2O2-induced neuronal apoptosis and necrosis. Furthermore, we found that exogenous HO-1 inhibited expression of Cdc42, which is crucial for MLK3 activation. In addition, HO-1-induced down-regulation of MLK3/MKK7/JNK3 signaling might be related to up-regulation of microRNA-137 (mir-137). A mir-137 inhibitor alleviated the inhibitory effect of HO-1 on JNK3 activation. This inhibitor also increased neuronal death even when exogenous HO-1 was expressed. Therefore, our study suggests a novel mechanism by which HO-1 exerted its neuroprotective efficacy on oxidative stress.

Overexpressing neuroglobin improves functional recovery by inhibiting neuronal apoptosis after spinal cord injury.

The current study was performed to evaluate the mechanisms and therapeutic effects of overexpressing neuroglobin (Ngb) on spinal cord injury (SCI). Adeno-associated virus (AAV) was injected in the T12 section 7 days before SCI. Animals were randomly divided into four groups: a sham group, a vehicle group, an AAV-EGFP group and an AAV-Ngb group. Recovery of hind limb locomotor function was determined during the 3-week post operation period by the Basso, Beattie and Bresnahan locomotor rating scale. At 24 h after SCI and at the end of the study, the segments of spinal cord, centered with the lesion site were harvested for histopathological analysis. Immunofluorescence was performed using antibodies to recognize neuN in the lesion sections. At 24 h after SCI, the spinal cord tissue samples were removed to analyze tissue concentrations of superoxide dismutase (SOD) and malondialdehyde (MDA). Apoptotic cells were assessed using a terminal deoxynucleotidyl transferase, dUTP nick end labeling (TUNEL) kit. The expression of bcl-2, bax, cytochrome c, and cleaved caspase-3, were determined by Western blot assay and immunostaining analysis. The results showed that animals overexpressing Ngb had significantly greater recovery of locomotor function, less neuronal loss and fewer apoptotic cells. In addition, overexpressing Ngb significantly increased bcl-2 expression and SOD level, decreased bax expression, attenuated the release of cytochrome c from mitochondria to the cytosol fraction, and reduced the activity of caspase-3 and MDA level after SCI. These findings suggest, that overexpressing Ngb can significantly improve the recovery of locomotor function. This neuroprotective effect may be associated with the inhibition of neural apoptosis via the mitochondrial pathway.

FIM-A, a phosphorus-containing sirolimus, inhibits the angiogenesis and proliferation of osteosarcomas.

The mTOR pathway is a central control of cell growth, proliferation, metabolism, and survival, and is deregulated in most cancers. Cancer cells are addicted to increased activity of mTOR kinase-mediated signaling pathways, leading to numerous inhibitors of mTOR signaling in preclinic and clinical trials for cancer therapy. Phosphorus-containing sirolimus (FIM-A), which targets mTOR signaling, inhibits cancer cell growth in vitro. Here we report that FIM-A reduces the angiogenesis and proliferation of osteosarcoma both in vitro and in vivo. In cultured osteosarcoma cell lines, FIM-A inhibited cell proliferation and arrested cells in the G1 phase of the cell cycle, accompanied with reduction of VEGF and HIF-1alpha. With in vivo mouse osteosarcoma xenografts, FIM-A treatment resulted in the inhibition of mTORC1 signaling as demonstrated by the decreased phosphorylation of p70S6K1 and 4E-BP1. Consistent with this finding, FIM-A significantly decreased the average tumor volume, nuclei staining of PCNA, and the number of intratumoral microvessels. Our data demonstrated that targeting mTORC1 by FIM-A inhibited the growth of osteosarcoma in vitro and in vivo, providing the basis for further development of FIM-A as a therapy for osteosarcoma patients.