Preventive effects of siRNA targeting PPARγ gene on steroid-induced osteonecrosis in rabbits

Recent advances in osteonecrosis of the femoral head: a focus on mesenchymal stem cells and adipocytes

Osteonecrosis of the femoral head (ONFH) is a debilitating orthopedic disease characterized by femoral head collapse and destruction of bone and articular cartilage, resulting in severe joint pain and loss of hip mobility. Bone marrow mesenchymal stem cells (BMSCs) exhibit multilineage differentiation potential, including osteoblasts, adipocytes, fibroblasts, chondrocytes, and neurocytes. The imbalance between osteogenesis and adipogenesis in BMSCs plays a critical role in ONFH pathogenesis. Factors such as alcohol consumption and glucocorticoid exposure promote adipogenic differentiation while inhibiting osteogenic differentiation, leading to excessive adipocyte accumulation, reduced bone formation, and vascular impairment. We highlight the molecular mechanisms underlying ONFH with a particular focus on the role of BMSCs and further discuss the involvement of adipocytes. Moreover, we suggest that the use of adipose-derived mesenchymal stem cells (ADMSCs) is a viable approach for stem cell therapy and may have immense potential in ONFH. Several signaling pathways, including the Wnt, TGFβ/BMP, and PI3K/AKT pathways, along with various RNAs and other regulators, govern the osteogenesis and adipogenesis of BMSCs. These signaling pathways target essential transcription factors, such as Runx2 for osteogenesis and PPARγ and C/EBPs for adipogenesis. Adipocytes and their secreted adipokines, including leptin and adiponectin, strongly influence ONFH progression. Emerging therapies involving ADMSCs show potential for promoting bone regeneration and neovascularization. Our review provides a comprehensive overview of the current understanding of ONFH mechanisms by focusing on mesenchymal stem cells and adipocytes and suggests future research directions for therapeutic interventions.

B-Lymphoid Tyrosine Kinase Crosslinks Redox and Apoptosis Signaling Networks to Promote the Survival of Transplanted Bone Marrow Mesenchymal Stem Cells

Stress-induced apoptosis presents an obstacle to bone marrow mesenchymal stem cell (BMSC) transplantation to repair steroid-induced osteonecrosis of the femoral head (SONFH). Thus, appropriate intervention strategies should be explored to mitigate this. In our previous study, we discovered a new subgroup of BMSCs-the oxidative stress-resistant BMSCs (OSR-BMSCs)-which can survive the oxidative stress microenvironment in the osteonecrotic area, through a mechanism that currently remains unclear. In this study, we found that B-lymphoid tyrosine kinase (BLK) may be the crucial factor regulating the oxidative stress resistance of OSR-BMSCs, as it is highly expressed in these cells. Knockdown of BLK eliminated oxidative stress resistance, aggravated oxidative stress-induced apoptosis, reduced the survival of OSR-BMSCs in the oxidative stress microenvironment of the osteonecrotic area, and greatly weakened the transplantation efficacy of OSR-BMSCs for SONFH. By contrast, BLK was weakly expressed in oxidative stress-sensitive BMSCs (OSS-BMSCs). Overexpression of BLK in susceptible OSS-BMSCs allowed them to acquire oxidative stress resistance, inhibited oxidative stress-induced apoptosis, promoted their survival in the osteonecrotic area, and improved the transplantation efficacy of OSS-BMSCs for SONFH. Mechanistically, BLK concurrently activates redox and apoptotic signaling networks through its tyrosine kinase activity, which confers oxidative stress resistance to BMSCs and inhibits their stress-induced apoptosis of BMSCs. Herein, we report that OSR-BMSCs have intrinsic oxidative stress resistance that is conferred and mediated by BLK. This finding provides a potential new intervention strategy for improving the survival of transplanted BMSCs and the therapeutic efficacy of BMSC transplantation for SONFH.

Pathological mechanisms and related markers of steroid-induced osteonecrosis of the femoral head

BACKGROUND

Osteonecrosis of the femoral head (ONFH) is a refractory orthopedic disease with a high disability rate. Long-term administration of steroids is the most common pathogenic factor for non-traumatic ONFH. Early diagnosis of steroid-induced osteonecrosis of the femoral head (SONFH) is difficult and mainly depends on imaging.

OBJECTIVES

The objectives of this review were to examine the pathological mechanisms of SONFH, summarize related markers of SONFH, and identify areas for future studies.

METHODS

We reviewed studies on pathological mechanisms and related markers of SONFH and discussed the relationship between them, as well as clinical applications and the outlook of potential markers.

RESULTS

The pathological mechanisms of SONFH included decreased osteogenesis, lipid accumulation, increased intraosseous pressure, and microcirculation disruption. Differential proteomics and genomics play crucial roles in the occurrence, progression, and outcome of SONFH, providing novel insights into SONFH. Additionally, the biological functions of mesenchymal stem cells (MSCs) and exosomes (Exos) in SONFH have attracted increasing attention.

CONCLUSIONS

The pathological mechanisms of SONFH are complex. The related markers mentioned in the current review can predict the occurrence and progression of SONFH, which will help provide effective early clinical prevention and treatment strategies for SONFH.

Preliminary study of the role of histone deacetylase (HDAC) in steroid-induced avascular necrosis of the femoral head induced by BMSC adipogenic differentiation

Our previous research revealed a close association between the acetylation of peroxisome proliferator-activated receptor γ (PPARγ) histone H3K27 and the adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). We preliminarily explored the epigenetic mechanism of steroid-induced avascular necrosis of the femoral head (SANFH) development, but the specific histone deacetylase (HDAC) involved in this regulatory process remains unknown. In this study, we combined cell, animal, and clinical specimen experiments to screen for specific HDAC genes that could regulate BMSC adipogenic differentiation and to explore their roles. The results showed that dexamethasone (DEX) significantly exacerbated the imbalance between the adipogenic and osteogenic differentiation of BMSCs, and there were differences in HDAC expression in the adipogenic differentiation cell models, with histone deacetylase 10 (HDAC10) showing the most significant decrease in expression. Subsequent use of a chromatin immunoprecipitation assay kit and quantitative polymerase chain reaction (ChIP‒qPCR) revealed a decrease in HDAC10 expression at predicted potential sites within the PPARγ promoter, indicating a significant decrease in HDAC10 enrichment in the PPARγ promoter region of BMSCs, thereby promoting sustained PPARγ expression. Additionally, immunohistochemistry of samples collected from mice and humans with SANFH and normal femoral heads revealed an imbalance between adipogenic and osteogenic differentiation in the necrotic area of femoral heads, with a significant decrease in the relative expression of HDAC10 in the necrotic area of femoral heads with SANFH. In summary, we speculate that HDAC10 affects the progression of SANFH by regulating BMSC adipogenic differentiation, a process possibly related to PPARγ histone acetylation. These findings provide a promising direction for the treatment of SANFH.

The PPAR-γ/SFRP5/Wnt/β-catenin signal axis regulates the dexamethasone-induced osteoporosis

BACKGROUND

The inhibition of glucocorticoid (GC) on osteoblastic differentiation of bone marrow stromal stem cells (BMSC) is an important pathway for GC to reduce bone formation. Recent studies implicated an important role of peroxisome proliferator-activated receptor-gamma (PPAR-γ) in GC-mediated cell proliferation and differentiation. Thus, our purpose is to investigate the role of PPAR-γ in regulating rat BMSC (rBMSC) osteoblastic differentiation.

METHODS

The rBMSC treated with dexamethasone (Dex) was used to construct an in vitro cell model of GC-induced osteoporosis. The expressions of PPAR-γ, RUNX2, ALP, OPN and SFRP5 in cells were detected by RT-qPCR and western blot assays. Osteogenic differentiation of rBMSC was measured by Alizarin Red S (ARS) staining analysis. Lentivirus-delivered shRNA was used to knock down PPAR-γ or SFRP5, and lentivirus-delivered constructs were used to overexpress SFRP5 in rBMSC to verify the effect of PPAR-γ or SFRP5 on cell osteogenic differentiation.

RESULTS

Dex significantly reduced rBMSC osteoblastic differentiation. The expression of PPAR-γ was enhanced in Dex treated rBMSC. PPAR-γ down-regulation improved Dex inhibition of rBMSC osteogenic differentiation. Moreover, PPAR-γ knockdown promoted protein levels of RUNX2, ALP, OPN and Dex-decreased rBMSC osteogenic differentiation. The expression of SFRP5 was reduced while Wnt and β-catenin were increased in PPAR-γ knockdown and Dex treated rBMSC. Moreover, the up-regulation of SFRP5 reversed the osteogenic differentiation of rBMSC induced by PPAR-γ knockdown.

CONCLUSION

These data indicated that in GC-induced osteoporosis, PPAR-γ/SFRP5 affects osteogenic differentiation by regulating the Wnt/β-catenin signaling pathway.

Study on the molecular mechanism of BuShenHuoXue capsule in treatment of steroid-induced osteonecrosis of the femoral head

BACKGROUND

Steroid-induced osteonecrosis of the femoral head (SONFH) is the pathological process caused by the death of the active components of the head of the femur due to the high dose of hormones, which has become a common public health problem. BuShenHuoXue capsule (BSHXC) has been clinically proven to be effective against the SONFH, the main pharmacological action of BSHXC is tonifying kidney and promoting blood circulation, but the mechanism remains to be explored.

METHODS

We established a rat SONFH model by injecting Methylprednisolone (MPS) into the right gluteus muscle 30 mg/kg/d, 3 days of continuous injection every week, 4 weeks in total. According to the clinical dosage of BSHXC (Herba epimedium 3 g, Eucommia ulmoides 15 g, Salvia miltiorrhizae 30 g, Chuanxiong 15 g, Paeonia lactiflora Pall 15 g, Poria cocos 12 g, Achyranthes bidentata 12 g, antler gum 10 g, Cyperus rotundus L. Nine g and Radix Glycyrrhizae 9 g), it was converted into the equivalent dose of rats, and gavage was performed at the weight of 10 mL/kg, once per day. The BSHXC was subjected to experiments in vivo, SONFH pharmacodynamics, bioinformatics, and network of pharmacology to determine the active ingredients, and its protective role against SONFH, Enrichment analysis was performed to explore the possible mechanism of BSHXC, and cell experiments were undertaken to analyze the impact of BSHXC on the hormones associated with bone marrow mesenchymal stem cells (BMSCs) between osteogenesis and apoptosis.

RESULTS

Experiments confirmed that BSHXC could effectively reduce bone loss in SONFH rat models. From bioinformatics and a network constructed from 10 drugs-208 pharmacology-126 targets, the enrichment analysis showed that the core targets were inflammatory reaction, steroid hormones, estrogen receptors, osteoporosis, and adjustment of osteogenesis and osteoclast differentiation, among others. The cell proliferation and staining supported that the mechanism of BSHXC promoted osteogenesis and intervening in apoptosis.

CONCLUSIONS

The BSHXC reduced the inflammatory response, changed steroid response, regulated estrogen receptors, delayed osteoporosis, regulated osteoblast and osteoclast differentiation by regulating related targets, and improved the local microenvironment by a multi-component, multi-target, and multi-link process to delay or reverse the progression of SONFH.

Platelet-rich plasma promotes bone formation, restrains adipogenesis and accelerates vascularization to relieve steroids-induced osteonecrosis of the femoral head

Steroid-associated necrosis of the femoral head (SANFH) is one of the most common and refractory chronic diseases with increasing incidence. The typical pathological changes of SANFH include decreased osteogenic differentiation, enhanced intramedullary adipocytes deposition and impaired osseous circulation. In this study, we investigated the effects and potential mechanisms of Platelet-rich plasma (PRP) on SANFH. Sixty Sprague-Dawley rats were randomly divided into the control, PRP donor, model, and PRP groups. Compared to the model group, PRP treatment significantly increased the hemorheological indexes and serum levels of bone gla-protein (BGP) and vascular endothelial growth factor (VEGF), while decreased the levels of triglyceride (TG) and total cholesterol (TC). Meanwhile, Micro-CT and histopathological stain (Hematoxylin-eosin and Alcian blue-hematoxylin/orange G staining) were performed on the femoral head for morphological and histopathological evaluation, indicating that bone trabecular microstructure and bone mineral density (BMD) were significantly improved after PRP treatment. Immunohistochemical analysis revealed that PRP remarkably up-regulated the expression of osteogenic markers including β-catenin and alkaline phosphatase (ALP), angiogenic markers containing VEGF and platelet endothelial cell adhesion molecule-1 (CD31), while down-regulated adipogenic markers involving fatty acid-binding protein (FABP-4), and peroxisome proliferator-activated receptor gamma (PPAR-γ) in SANFH rat models. In summary, for the first time, PRP was demonstrated to prevent the development of SANFH through stimulating bone formation and vascularization as well as retarding adipogenesis.

Chrysophanic acid shifts the differentiation tendency of BMSCs to prevent alcohol-induced osteonecrosis of the femoral head

Objectives

Osteonecrosis of the femoral head (ONFH), largely caused by alcohol abuse, is a refractory bone disease characterized by the impaired capacity of osteogenic differentiation of bone mesenchymal stem cells (BMSCs), as well as the disordered adipocyte accumulation. Chrysophanic acid (CPA) is a natural anthraquinone which has lipid regulation and bone protection capacity. The aim of this study was to reveal the potential function of CPA and the underlying mechanisms for the alcohol‐induced ONFH.

Materials and Methods

The effects of alcohol and CPA on BMSCs were investigated by cell proliferation, induced differentiation assays and immunofluorescent staining. Meanwhile, the function of PI3K/AKT and AMPK pathway was investigated in the process of osteogenic and adipogenic differentiation, respectively. Furthermore, we established the rat model of alcohol‐induced ONFH to reveal the pharmacotherapeutic effect of CPA in vivo using radiographical and histopathological methods.

Results

In vitro, alcohol significantly inhibited the proliferation and osteogenic differentiation of BMSCs but stimulated the adipogenic differentiation. However, CPA could counteract the anti‐osteogenesis of alcohol partly via PI3K/AKT pathway and retard the promotion of alcohol‐induced adipogenesis via AMPK pathway. In vivo, radiographical and histopathological findings showed that CPA could alleviate alcohol‐induced ONFH and substantially restore the bone volume.

Conclusions

We demonstrated that CPA ameliorated alcohol‐induced ONFH possibly via regulating the differentiation tendency of BMSCs. Hence, CPA may become a beneficial herb extract to alleviate alcohol‐induced ONFH.

Osthole stimulates bone formation, drives vascularization and retards adipogenesis to alleviate alcohol-induced osteonecrosis of the femoral head

Characteristic pathological changes in osteonecrosis of the femoral head (ONFH) include reduced osteogenic differentiation of bone mesenchymal stem cells (BMSCs), impaired osseous circulation and increased intramedullary adipocytes deposition. Osthole is a bioactive derivative from coumarin with a wide range of pharmacotherapeutic effects. The aim of this study was to unveil the potential protective role of osthole in alcohol‐induced ONFH. In vitro, ethanol (50 mmol/L) remarkably decreased the proliferation and osteogenic differentiation of BMSCs and impaired the proliferation and tube formation capacity of human umbilical vein endothelial cell (HUVECs), whereas it substantially promoted the adipogenic differentiation of BMSCs. However, osthole could reverse the effects of ethanol on osteogenesis via modulating Wnt/β‐catenin pathway, stimulate vasculogenesis and counteract adipogenesis. In vivo, the protective role of osthole was confirmed in the well‐constructed rat model of ethanol‐induced ONFH, demonstrated by a cascade of radiographical and pathological investigations including micro‐CT scanning, haematoxylin‐eosin staining, TdT‐mediated dUTP nick end labelling, immunohistochemical staining and fluorochrome labelling. Taken together, for the first time, osthole was demonstrated to rescue the ethanol‐induced ONFH via promoting bone formation, driving vascularization and retarding adipogenesis.

Inhibition of PPARγ by bisphenol A diglycidyl ether ameliorates dexamethasone-induced osteoporosis in a mouse model

Objectives

Bisphenol A diglycidyl ether (BADGE) is an antagonist for PPARγ that reduces bone marrow adiposity and increases bone formation in some animal models of osteoporosis and osteonecrosis. However, the effect of BADGE treatment on glucocorticoid-induced osteoporosis is unknown. This study investigated the preventive effects of BADGE on steroid-induced osteoporosis in mice.

Methods

Thirty-six female C57BL/6J mice were randomly divided into normal (phosphate-buffered saline), model (50 mg/kg dexamethasone sodium phosphate [Dex]), and BADGE (30 mg/kg of BADGE, combined with Dex) groups. All groups received intraperitoneal injections of their treatments, daily for 4 weeks. Protein and mRNA expression levels of gene markers were measured. Micro-computed tomography was used to measure physical parameters of femurs. Bone histomorphology was analyzed by hematoxylin and eosin staining. ELISA was used to measure serum osteocalcin and C-terminal telopeptide of type I collagen (CTX-1).

Results

Glucocorticoid treatment enlarged the marrow fat, concomitant with bone deterioration; BADGE treatment reversed steroid-induced marrow adiposity. Compared with the model group, BADGE treatment improved bone quality and increased bone volume, while increasing osteogenic markers and reducing adipogenic markers at both mRNA and protein levels; moreover, it reduced serum CTX-1 and increased serum osteocalcin.

Conclusion

BADGE treatment ameliorates glucocorticoid-induced osteoporosis by inhibiting PPARγ.

Salvianolic Acid B Improves Mitochondrial Function in 3T3-L1 Adipocytes Through a Pathway Involving PPARγ Coactivator-1α (PGC-1α)

Purpose: Mitochondrial dysfunction in adipose tissue has emerged as key to the development of obesity and diabetes. Salvianolic acid B (SalB) is a water-soluble ingredient derived from Salvia miltiorrhiza that has been shown to possess potential anti-obese and anti-diabetic activities. However, the cellular mechanism of SalB on mitochondrial function with respect to these metabolic disorders has not been elucidated. Therefore, we aim to investigate the effects of SalB on mitochondrial function in 3T3-L1 adipocytes and analyze the underlying molecular mechanism. Methods: The effects of SalB on adipocyte differentiation, glucose uptake, and glycerol release were evaluated in 3T3-L1 adipocytes. Differentiated adipocytes were treated with SalB (50 μM) with or without PPARγ antagonist (GW9662, 20 μM) for 48 h, and mitochondrial oxygen consumption rate (OCR) as well as extracellular acidification rate (ECAR) were assessed using an XF Extracellular Flux Analyzer. The mitochondrial distribution of adipocytes was assessed using Mito Tracker Green (MTG) and observed under a fluorescent microscope. In addition, the mRNA expression levels of peroxisome proliferators-activated receptor γ/α (PPARγ/α), CCAAT/enhancer binding proteinα (C/EBPα), Nuclear respiratory factor 1/2 (NRF1/2), Uncoupling protein 2 (UCP2), and phosphofructokinase 2/fructose-2, 6-bisphosphatase 2 (PFKFB2) were detected by RT-PCR. Finally, changes in the protein levels of peroxisome proliferators-activated receptor γ coactivator-1α (PGC-1α) were determined by western blotting and immunofluorescence analysis. Results: Treatment with SalB increased glucose uptake and mitochondrial respiration, reduced glycerol release and promoted adipocyte differentiation by increasing mRNA expression of adipogenic transcription factors including PPARγ, C/EBPα, and PPARα. Furthermore, SalB enhanced adipocytes mitochondrial content, mitochondrial respiration and glycolysis capacity, which had been attenuated by GW9662 treatment through the increased expression of PGC-1α. Conclusion: Our results provide novel insights into the role of PGC-1α and mitochondria as probable mediators of SalB activity in the regulation of adipocyte differentiation in 3T3-L1 adipocytes.

Animal models of steroid-induced osteonecrosis of the femoral head-a comprehensive research review up to 2018

Osteonecrosis of the femoral head (ONFH) is a significant cause of both pain and disability that often affects young adults during what ought to be their most productive age. Two broad categories of ONFH exist: traumatic and non-traumatic. Traumatic ONFH results from acute mechanical disruption of the femoral head's blood supply. Many factors that increase the risk of non-traumatic osteonecrosis have been identified. Steroid-induced osteonecrosis of the femoral head (SONFH) is the most common form of non-traumatic ONFH. Many hypotheses as to the pathogenesis of SONFH have been proposed, including intravascular thrombosis, abnormal fat metabolism, intramedullary adipocyte hypertrophy, and osteoporosis; however, the exact mechanism of SONFH is still not clearly understood. Animal models using rats, mice, rabbits, chickens, pigs, and emus have been used to study SONFH. Unfortunately, these models each have limitations. Therefore, it is necessary to establish a reproducible model that better simulates human disease. The present review is intended to summarize the currently available models, evaluative indicators, and application of current understanding to both the prevention and treatment of SONFH.

BADGE, a synthetic antagonist for PPARγ, prevents steroid-related osteonecrosis in a rabbit model

Background

It was indicated that inhibition of PPARγ probably represents a novel therapy for steroid-related osteonecrosis. In this study, we investigated the preventive effects of PPARγ inhibition on steroid-related osteonecrosis in a rabbit model.

Methods

Rabbits were randomly divided into three groups (normal group, model group and BADGE group). Osteonecrosis was induced in rabbits in the model group and the BADGE group. The BADGE group also received bisphenol a diglycidyl ether(BADGE), a PPARγ antagonist, for 6 weeks.

Results

Histopathological results indicated that rabbits treated with BADGE exhibited significantly reduced osteonecrotic changes, incidence of osteonecrosis and bone marrow adiposity. Furthermore, BADGE-treated rabbits exhibited reduced intraosseous pressure and increased femoral blood perfusion. Micro-computed tomography and bone histomorphometry indicated that the BADGE group exhibited significantly improved bone quality and mineral appositional rate compared with the model group. Furthermore, the BADGE group showed a significant increase in circulating levels of the bone formation marker osteocalcin and reduced levels of the bone resorption marker TRACP. Overall, BADGE-treated rabbits exhibited reduced marrow adiposity concomitant with improved bone formation.

Conclusions

In conclusion, these observations demonstrated that pharmacological inhibition of PPARγ might represent an effective therapy for steroid-related osteonecrosis in the near future.

Small non-coding RNAs-based bone regulation and targeting therapeutic strategies

Small non-coding RNAs, which are 20-25 nucleotide ribonucleic acids, have emerged as an important transformation in the biological evolution over almost three decades. microRNAs (miRNAs) and short interfering RNAs (siRNAs) are two significant categories of the small RNAs that exert important effects on bone endocrinology and skeletology. Therefore, clarifying the expression and function of these important molecules in bone endocrine physiology and pathology is of great significance for improving their potential therapeutic value for metabolism-associated bone diseases. In the present review, we highlight the recent advances made in understanding the function and molecular mechanism of these small non-coding RNAs in bone metabolism, especially their potentially therapeutic values in bone-related diseases.

Differential proteomic screening and identification for non-traumatic necrotic femoral osseous tissue

Currently, there is a lack of effective early screening and detection methods for femoral head necrosis. Current research on most orthopedic diseases focuses on proteomics in the preliminary stage. The recent fluorescence differential in gel electrophoresis (DIGE) has advantages such as a high reproducibility, high sensitivity, high throughput, and high dynamic range. It is currently one of the most widely used quantitative proteomic research means. We conducted this study to investigate the pathogenesis of non-traumatic femoral head necrosis using the fluorescence DIGE to screen non-traumatic femoral head necrosis based on proteomics and provide a theoretical basis for screening possible biomarkers and molecular targeted treatment. The DIGE technique was used to separate the protein. An electrophoretogram was established on the basis of scanning and analysis. Identification and a bioinformatics analysis were conducted for the differential protein. The protein with differential expression of over 2-fold was excavated and ionized by means of substrate assisted laser desorption. The flight time was identified with a mass spectrometer (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, MALDI-TOF/TOF). The formation on sequences, structures and functions of these proteins were obtained through database retrieval. Western blot analysis was used to verify the differential protein expression and the reliability of the DIGE result was verified. DIGE was used to successfully separate 1,500±40 protein spots. There were 252 significant differential protein spots. The Ettan™ Spot Picker automatic work station was used to excavate 49 significant differential protein spots with expression difference over 2-fold. The MALDI-TOF/TOF mass spectrometer was used to identify these differential protein spots. Six proteins were identified in total, which include apolipoprotein A1 (APOA1), fibrous protein original chain, fibrous protein original chain, serum albumin, sulfur-oxygen protein peroxiredoxin 2 (PRDX2) and actin. APOA1 and PRDX2 were subject to western blot analysis detection; results were consistent with the DIGE result. Based on an analysis of the biological information, these proteins may be associated with the incidence and progression of femoral head necrosis.

P-glycoprotein overexpression in bone marrow-derived multipotent stromal cells decreases the risk of steroid-induced osteonecrosis in the femoral head

P-glycoprotein (P-gp) plays a role in steroid-induced osteonecrosis of the femoral head (ONFH), but the underlying mechanism remains unknown. We hypothesized that P-gp overexpression can prevent ONFH by regulating bone marrow-derived multipotent stromal cell (BMSC) adipogenesis and osteogenesis. BMSCs from Sprague-Dawley rats were transfected with green fluorescent protein (GFP) or the multidrug resistance gene 1 (MDR1) encoding GFP and P-gp. Dexamethasone was used to induce BMSC differentiation. Adipogenesis was determined by measuring peroxisome proliferator-activated receptor (PPAR-γ) expression and the triglyceride level. Osteogenesis was determined by measuring runt-related transcription factor 2 (Runx2) expression and alkaline phosphatase activity. For in vivo experiments, rats were injected with saline, BMSCs expressing GFP (GFP-BMSCs) or BMSCs expressing GFP-P-gp (MDR1-GFP-BMSCs). After dexamethasone induction, adipogenesis was determined by measuring PPAR-γ expression and fatty marrow, whereas osteogenesis was detected by measuring Runx2 expression, trabecular parameters and the mineral apposition rate, followed by evaluation of the incidence of ONFH. Overexpression of P-gp in BMSCs resulted in markedly decreased expression of adipogenic markers and increased expression of osteogenic markers. Compared with rats injected with saline, rats injected with GFP-BMSCs showed reduced ONFH, and the injected GFP-positive BMSCs attached to trabecular surfaces and exhibited an osteoblast-like morphology. Compared with the rats injected with BMSCs expressing GFP alone, rats injected with BMSCs overexpressing GFP and P-gp showed lower adipocytic variables, higher osteogenic variables and lower incidence of ONFH. Overexpression of P-gp inhibited BMSC adipogenesis and promoted osteogenesis, which reduced the incidence of steroid-induced ONFH.