G-CSF/SCF exert beneficial effects via anti-apoptosis in rabbits with steroid-associated osteonecrosis

METTL14 benefits the mesenchymal stem cells in patients with steroid-associated osteonecrosis of the femoral head by regulating the m6A level of PTPN6

Imbalanced osteogenic/adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is considered the core pathological characteristic of steroid-associated osteonecrosis of the femoral head (SONFH). N6-Methyladenosine (m6A) is the most common type of RNA modification in eukaryotic cells and participates in various physiological and pathological processes. However, the relationship between m6A modification and SONFH has not been reported. In the present study, we aimed to explore the roles of m6A modifications and methyltransferase METTL14 in SONFH. Our results showed that the m6A levels were down-regulated in femoral head tissues and BMSCs from SONFH patients, and this effect was attributed to the reduction of METTL14. Furthermore, METTL14 overexpression in BMSCs from SONFH patients enhanced cell proliferation and osteogenic differentiation. We further identified PTPN6 as the downstream target of METTL14 by mRNA sequencing. Mechanistically, METTL14 regulated PTPN6 expression by increasing PTPN6 mRNA stability in an m6A-dependent manner. Moreover, PTPN6 knockdown abrogated the beneficial effects of METTL14 overexpression on BMSCs. Additionally, we found that METTL14 activated the Wnt signaling pathway, and this effect was caused by the interaction of PTPN6 and GSK-3β. In conclusion, we elucidated the functional roles of METTL14 and m6A methylation in SONFH BMSCs and identified a novel RNA regulatory mechanism, providing a potential therapeutic target for SONFH.

Glucocorticoids induce osteonecrosis of the femoral head through the Hippo signaling pathway

Osteonecrosis of the femoral head (ONFH) induced by glucocorticoids (GCs) has been considered to be associated with the dysfunction of bone marrow mesenchymal stem cells (BMSCs). Studies have reported that GCs can regulate the normal differentiation of BMSCs. However, the exact mechanism of this regulation remains unclear. In this study, we used methylprednisolone (MPS) to induce BMSCs, and then found that the Hippo signaling pathway was upregulated in a dose-dependent manner compared to that in the control group. In addition, the osteogenic ability of BMSCs was decreased, as evaluated by Alizarin Red S staining analysis and alkaline phosphatase activity assays, accompanied by the downregulated expression of Runx2, osteopontin, and osteocalcin. Additionally, the adipogenic capacity of BMSCs under the MPS conditions was increased, as identified by Oil Red O staining with upregulated triglyceride and PPARγ expression. Moreover, suppression by knockdown of MST1 was found to attenuate the Hippo signaling pathway and adipogenic differentiation, while enhancing osteogenic differentiation. In conclusion, our findings revealed that the Hippo signaling pathway was involved in GC-ONFH by affecting the osteogenic and adipogenic differentiation capacities of BMSCs. Our study could provide a basis for further investigation of the specific function of the Hippo pathway in ONFH.

Hyper-activated platelet lysates prevent glucocorticoid-associated femoral head necrosis by regulating autophagy

Platelet Rich Plasma (PRP) can activate angiogenic and osteogenic pathways, making it a highly promising therapeutic agent for bone growth. Super active platelet lysate (sPL) is derived from platelet-rich plasma (PRP) through ultra-low temperature freeze-thawing. The aim of this study was to evaluate the potential therapeutic effect of sPL on glucocorticoid (GC)-induced osteonecrosis of the femoral head (ONFH). sPL increased the proliferation of GC-treated osteoblasts and endothelial cells, and inhibited apoptosis in vitro. Furthermore, sPL promoted healing of necrotic bone tissues in a rat ONFH model by restraining GC-induced apoptosis and increase autophagy of the osteoblasts. Overall, the results of this study provide a theoretical basis for the clinical application of sPL in ONFH.

Multiscale Stem Cell Technologies for Osteonecrosis of the Femoral Head

The last couple of decades have seen brilliant progress in stem cell therapies, including native, genetically modified, and engineered stem cells, for osteonecrosis of the femoral head (ONFH). In vitro studies evaluate the effect of endogenous or exogenous factor or gene regulation on osteogenic phenotype maintenance and/or differentiation towards osteogenic lineage. The preclinical and clinical outcomes accelerate the clinical translation. Bone marrow mesenchymal stem cells and adipose-derived stem cells have demonstrated better effects in the treatment of femoral head necrosis. Various materials have been used widely in the ONFH treatment in both preclinical and clinical trials. In a word, in vivo and multiscale efforts are expected to overcome obstacles in the approaches for treating ONFH and provide clinical relevance and commercial strategies in the future. Therefore, we will discuss the above aspects in this paper and present our opinions.

KIT as a therapeutic target for non-oncological diseases

KIT is a receptor tyrosine kinase that after binding to its ligand stem cell factor activates signaling cascades linked to biological processes such as proliferation, differentiation, migration and cell survival. Based on studies performed on SCF and/or KIT mutant animals that presented anemia, sterility, and/or pigmentation disorders, KIT signaling was mainly considered to be involved in the regulation of hematopoiesis, gametogenesis, and melanogenesis. More recently, novel animal models and ameliorated cellular and molecular techniques have led to the discovery of a widen repertoire of tissue compartments and functions that are being modulated by KIT. This is the case for the lung, heart, nervous system, gastrointestinal tract, pancreas, kidney, liver, and bone. For this reason, the tyrosine kinase inhibitors that were originally developed for the treatment of hemato-oncological diseases are being currently investigated for the treatment of non-oncological disorders such as asthma, rheumatoid arthritis, and alzheimer's disease, among others. The beneficial effects of some of these tyrosine kinase inhibitors have been proven to depend on KIT inhibition. This review will focus on KIT expression and regulation in healthy and pathologic conditions other than cancer. Moreover, advances in the development of anti-KIT therapies, including tyrosine kinase inhibitors, and their application will be discussed.

Granulocyte-Colony Stimulating Factor (G-CSF) Accelerates Wound Healing in Hemorrhagic Shock Rats by Enhancing Angiogenesis and Attenuating Apoptosis

Background

Following severe trauma, treatment of cutaneous injuries is often delayed by inadequate blood supply. The aim of the present study was to determine whether granulocyte-colony stimulating factor (G-CSF) protects endothelial cells (ECs) and enhances angiogenesis in a rat model of hemorrhagic shock (HS) combined with cutaneous injury after resuscitation.

Material/Methods

The HS rats with full-thickness defects were resuscitated and randomly divided into a G-CSF group (200 μg/kg body weight), a normal saline group, and a blank control group. Histological staining was to used estimate the recovery and apoptosis of skin. Apoptosis- and angiogenesis-related factors were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot (WB). Scratch assay, tube formation, and WB experiments were performed to verify the functional effects of G-CSF on HUVECs in vitro.

Results

H&E staining and Masson trichrome staining showed earlier inflammation resolution and collagen synthesis in the G-CSF-treated group. Angiogenesis-related factors were elevated at mRNA and protein levels. TUNEL staining suggested fewer apoptotic cells in the G-CSF group. The apoptotic-related factors were down-regulated and anti-apoptotic factors were up-regulated in the G-CSF-treated group. Scratch assay and tube formation experiments revealed that G-CSF facilitated migration ability and angiogenic potential of HUVECs. The angiogenic and anti-apoptotic effects were also enhanced in vitro.

Conclusions

Our results suggest that G-CSF after resuscitation attenuates local apoptosis and accelerates angiogenesis. These findings hold great promise for improving therapy for cutaneous injury in severe trauma and ischemia diseases.

IL-4 administration exerts preventive effects via suppression of underlying inflammation and TNF-α-induced apoptosis in steroid-induced osteonecrosis

Macrophages play an important role during the development of steroid-induced osteonecrosis. Interleukin (IL)-4 administration helped reduce the infiltration of M1 phenotypic macrophages and maintain the activation of M2 phenotypic macrophages, resulting in restriction of inflammation and decrease in osteocyte apoptosis. The results indicated the therapeutic potential of IL-4 in prevention of steroid-induced osteonecrosis.

INTRODUCTION

Steroid-induced osteonecrosis (ON) is a debilitating disease characterized by the activation and infiltration of macrophages into the necrotic site. This study aimed to investigate the effects of IL-4 administration on macrophage polarization and the involved signaling pathways.

METHODS

Fifty-six BALB/c mice were randomly divided into two groups, group M (model group) and group MI (treatment group), each containing 28 mice. ON model was induced by the injection of methylprednisolone (MPS). The mice in group MI received intra-abdominal injections of 2 μg/100 g/day of rIL-4 for five consecutive days, following the administration of MPS. Osteonecrosis was verified by histopathological staining. The expression of tumor necrosis factor-alpha (TNF-α) was analyzed by ELISA and immunohistochemistry. The infiltration of M1/M2 macrophages was examined by the expression of specific makers of F4/80, CD11c, and CD206 protein. Cell apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay, and the apoptotic signal molecules such as STAT1 and caspase-3 were examined.

RESULTS

Histopathological observations indicated that IL-4 administration reduced the incidence of ON and the accumulation of osteoclasts. IL-4 administration inhibited the expression of TNF-α and reduced the infiltration of M1 phenotypic macrophages and maintained relatively high level of M2 phenotypic macrophages. Additionally, TUNEL assay suggested that IL-4 intervention could reduce the number of apoptotic cells in the necrotic zone. The anti-apoptotic mechanisms were related to STAT1 phosphorylation and the activation of caspase-3.

CONCLUSIONS

Il-4 administration could alleviate steroid associated ON in mice by inhibiting the inflammatory response, the infiltration of M1 phenotypic macrophages, and suppressing TNF-a-induced osteocytic apoptosis by inhibiting the STAT1-caspase-3 signal pathway.

Vitamin K2 Prevents Glucocorticoid-induced Osteonecrosis of the Femoral Head in Rats

Glucocorticoid medication is one of the most common causes of atraumatic osteonecrosis of the femoral head (ONFH), and vitamin K₂ (VK₂) has been shown to play an important and beneficial role in bone metabolism. In this study, we hypothesized that VK₂ could decrease the incidence of glucocorticoid-induced ONFH in a rat model. Using in vitro studies, we investigated how bone marrow-derived stem cells in the presence of methylprednisolone proliferate and differentiate, specifically examining osteogenic-related proteins, including Runx2, alkaline phosphatase and osteocalcin. Using in vivo studies, we established glucocorticoid-induced ONFH in rats and investigated the preventive effect of VK₂. We employed micro-CT scanning, angiography of the femoral head, and histological and immunohistochemical analyses, which demonstrated that VK₂ yielded beneficial effects for subchondral bone trabecula. In conclusion, VK₂ is an effective antagonist for glucocorticoid on osteogenic progenitors. The underlying mechanisms include acceleration of BMSC propagation and promotion of bone formation-associated protein expression, which combine and contribute to the prevention of glucocorticoid-induced ONFH in rats.

Abnormal subchondral bone microstructure following steroid administration is involved in the early pathogenesis of steroid-induced osteonecrosis

Loss of bone microstructure integrity is thought to be related to osteonecrosis. But the relationship between the time when bone microstructure integrity loss appears and the onset of osteonecrosis has not yet been determined. Our study demonstrated abnormal changes of subchondral bone microstructure involved in the early pathogenesis of osteonecrosis.

INTRODUCTION

Using a rabbit model, we investigated the changes of subchondral bone microstructure following steroid administration to identify the onset of abnormal bone microstructure development in steroid-induced osteonecrosis.

METHODS

Fifty-five adult female Japanese White rabbits (mean body weight 3.5 kg; mean age 24 months) were used and randomly divided among three time points (3, 7, and 14 days) consisting of 15 rabbits each, received a single intramuscular injection of methylprednisolone acetate (MP; Pfizer Manufacturing Belgium NV) at a dose of 4 mg/kg, and a control group consisting of 10 rabbits was fed and housed under identical conditions but were not given steroid injections. A micro-CT scanner was applied to detect changes in the trabecular region of subchondral bone of excised femoral head samples. Parameters including bone volume fraction (BV/TV), bone surface (BS), trabecular bone pattern factor (Tb.Pf), trabecular thickness/number/separation (Tb.Th, Tb.N, and Tb.Sp), and structure model index (SMI) were evaluated using the software CTAn (SkyScan). After micro-CT scans, bilateral femoral heads were cut in the coronal plane at a thickness of 4 μm. The sections were then stained with haematoxylin-eosin and used for the diagnosis of osteonecrosis and the rate of development of osteonecrosis.

RESULTS

The BV/TV, BS, Tb.Th and Tb.N demonstrated a time-dependent decline from 3, 7, and 14 days compared with the control group, while the Tb.Pf, Tb.Sp and SMI demonstrated an increase at 3, 7, and 14 days compared with the control group. For the histopathology portion, osteonecrosis was not seen 3 days after steroid treatment, but was present 7 days after treatment and was obvious 14 days after treatment. Furthermore, the rate of osteonecrosis appearing between 7 and 14 days was not significantly different. In addition, the presence and variation of BV/TV, BS, Tb.Pf, Tb.Th, Tb.N, and SMI demonstrated significant changes at 7 days compared with the control group except Tb.Sp (at 14 days) and this is the time when osteonecrosis is thought to occur in this model.

CONCLUSION

This study demonstrated that osteonecrosis in rabbits is chronologically associated with changes in subchondral bone microstructure.

Osteonecrosis of the femoral head: treatment with ancillary growth factors

Osteonecrosis (ON) of the femoral head, also known as avascular necrosis (AVN) of the femoral head, is a progressive disease that predominantly affects younger patients. During early stage of ON, decompression of the femoral head has been commonly used to improve pain. The decompression has been augmented with nonvascularized or vascularized bone grafts, mesenchymal stems cells, and growth factors. The use of adjuvant growth factors to supplement the core decompression has mainly been limited to animal models in an attempt to regenerate the necrotic lesion of ON. Factors utilized include bone morphogenetic proteins, vascular endothelial growth factors, hepatocyte growth factors, fibroblast growth factors, granulocyte colony-stimulating factors, and stem cells factors. In animal models, the use of these factors has been shown to increase bone formation and angiogenesis. Although promising, the use of these growth factors and cell-based therapies clinically remains limited.

Steroid-associated osteonecrosis: Epidemiology, pathophysiology, animal model, prevention, and potential treatments (an overview)

Steroid-associated osteonecrosis (SAON) is a common orthopaedic problem caused by administration of corticosteroids prescribed for many nonorthopaedic medical conditions. We summarised different pathophysiologies of SAON which have adverse effects on multiple systems such as bone marrow stem cells (BMSCs) pool, bone matrix, cell apoptosis, lipid metabolism, and angiogenesis. Different animal models were introduced to mimic the pathophysiology of SAON and for testing the efficacy of both prevention and treatment effects of various chemical drugs, biological, and physical therapies. According to the classification of SAON, several prevention and treatment methods are applied at the different stages of SAON. For the current period, Chinese herbs may also have the potential to prevent the occurrence of SAON. In the future, genetic analysis might also be helpful to effectively predict the development of ON and provide information for personalised prevention and treatment of patients with SAON.

Beneficial effect of grape seed proanthocyanidin extract in rabbits with steroid-induced osteonecrosis via protecting against oxidative stress and apoptosis

BACKGROUND

Oxidative damage and apoptosis play dominant roles in the pathogenesis of steroid-induced osteonecrosis (ON). Grape seed proanthocyanidin extract (GSPE) demonstrates antioxidant and antiapoptotic properties. Our aim was to demonstrate the effects of GSPE in preventing steroid-induced ON in rabbits.

METHODS

Osteonecrosis was induced by high-dose methylprednisolone (40 mg/kg). Rabbits in the preventive medicine group were treated with 100 mg/kg/day GSPE for 14 consecutive days, and the presence or absence of ON was examined histopathologically. Oxidative damage in bone tissue was assessed by immunohistochemical staining of 8-oxo-2'-deoxyguanosine (8-OHdG), malondialdehyde (MDA) levels, and activities of antioxidant enzymes Cu/Zn superoxide dismutase (SOD) and phospholipid hydroperoxide glutathione peroxidase (GSH-Px). Apoptosis was detected via quantitative terminal deoxynucleotidyl transferase (TdT) deoxyuridine triphosphate nick end labelling (TUNEL) staining and activated caspase 3 immunoblotting and activity.

RESULTS

GSPE significantly attenuated the changes of immunohistochemical staining of 8-OHdG, MDA levels, and antioxidant enzymes activities, which were caused by methylprednisolone administration. Quantitative TUNEL and caspase 3 assay showed lower apoptosis with GSPE application. Simultaneously, GSPE reduced the incidence of steroid-induced ON in an established rabbit model to 17.6 %, compared with 87.5 % in the steroid-only group.

CONCLUSION

These results reveal that GSPE treatment could inhibit oxidative damage and apoptosis to exert beneficial effects on reducing the incidence of steroid-induced ON in rabbit models.