Trelagliptin stimulates osteoblastic differentiation by increasing runt-related transcription factor 2 (RUNX2): a therapeutic implication in osteoporosis

Uniaxial static strain enhances osteogenic and angiogenic potential under hypoxic conditions in distraction osteogenesis

OBJECTIVE

Bone incision leads to interrupted and sluggish blood flow in the process of distraction osteogenesis (DO), creating a hypoxia (0-2% oxygen tension) at the center of the bone callus. This hypoxia is critical in the coupling of osteogenesis and angiogenesis during DO. This study aimed to investigate the effect of Uniaxial Static Strain (USS) on osteogenesis in osteoblasts under hypoxic conditions, with a focus on the expression of osteogenic markers and angiogenic factors.

METHODS

The USS was made by a multi-unit tension compression device.Osteoblasts were subjected to 10% USS made under hypoxic conditions to mimic the process of DO in vitro. The cell proliferation, alkaline phosphatase (ALP) activity, mineralized nodule formation, and expression of osteogenic and angiogenic markers were evaluated by using a CCK-8 assay, alkaline phosphatase (ALP) staining, ALP activity assay, alizarin red S staining, qRT-PCR, Western blotting and ELISA.

RESULTS

Hypoxia inhibited osteoblast cell proliferation, ALP activity, mineralized nodule formation, and the expression of runt-related transcription factor 2 (Runx- 2), osteopontin(OPN), osteocalcin (OCN), collagen type I (Col1a1). Conversely, hypoxia upregulated the expression of hypoxia-inducible factor 1-alpha (HIF-1α) and vascular endothelial growth factor (VEGF), which are associated with angiogenesis. However, the application of USS enhanced osteoblasts' osteogenic capacity and upregulated angiogenic factors under hypoxic conditions.

CONCLUSION

USS can enhance osteogenesis in osteoblasts under hypoxic conditions. Moreover, it may stimulate angiogenesis by promoting the expression of VEGF, which further contributes to bone formation. This finding provides important implications for understanding the mechanisms involved in bone regeneration and may have clinical applications in optimizing the effectiveness of DO techniques.

Dehydrocostus lactone (DHC) promotes osteoblastic differentiation and mineralization through p38/RUNX-2 signaling

Dysregulation of osteoblastic differentiation is an important risk factor of osteoporosis, the therapy of which is challenging. Dehydrocostus lactone (DHC), a sesquiterpene isolated from medicinal plants, has displayed anti-inflammatory and antitumor properties. In this study, we investigated the effects of DHC on osteoblastic differentiation and mineralization of MC3T3-E1 cells. Interestingly, we found that DHC increased the expression of marker genes of osteoblastic differentiation, such as alkaline phosphatase (ALP), osteocalcin (OCN), and osteopontin (OPN). Additionally, DHC increased the expressions of collagen type I alpha 1 (Col1a1) and collagen type I alpha 2 (Col1a2). We also demonstrate that DHC increased ALP activity. Importantly, the Alizarin Red S staining assay revealed that DHC enhanced osteoblastic differentiation of MC3T3-E1 cells. Mechanistically, it is shown that DHC increased the expression of Runx-2, a central regulator of osteoblastic differentiation. Treatment with DHC also increased the levels of phosphorylated p38, and its blockage using its specific inhibitor SB203580 abolished the effects of DHC on runt-related transcription factor 2 (Runx-2) expression and osteoblastic differentiation, suggesting the involvement of p38. Based on these findings, we concluded that DHC might possess a capacity for the treatment of osteoporosis by promoting osteoblastic differentiation.

The OSR9 Regimen: A New Augmentation Strategy for Osteosarcoma Treatment Using Nine Older Drugs from General Medicine to Inhibit Growth Drive

As things stand in 2023, metastatic osteosarcoma commonly results in death. There has been little treatment progress in recent decades. To redress the poor prognosis of metastatic osteosarcoma, the present regimen, OSR9, uses nine already marketed drugs as adjuncts to current treatments. The nine drugs in OSR9 are: (1) the antinausea drug aprepitant, (2) the analgesic drug celecoxib, (3) the anti-malaria drug chloroquine, (4) the antibiotic dapsone, (5) the alcoholism treatment drug disulfiram, (6) the antifungal drug itraconazole, (7) the diabetes treatment drug linagliptin, (8) the hypertension drug propranolol, and (9) the psychiatric drug quetiapine. Although none are traditionally used to treat cancer, all nine have attributes that have been shown to inhibit growth-promoting physiological systems active in osteosarcoma. In their general medicinal uses, all nine drugs in OSR9 have low side-effect risks. The current paper reviews the collected data supporting the role of OSR9.

Non-Specific Inhibition of Dipeptidyl Peptidases 8/9 by Dipeptidyl Peptidase 4 Inhibitors Negatively Affects Mesenchymal Stem Cell Differentiation

DPP4 may play a relevant role in MSC differentiation into osteoblasts or adipocytes. Dipeptidyl peptidase 4 (DPP4) inhibitors (DPP4i), such as sitagliptin and vildagliptin, are used as antidiabetic drugs. However, vildagliptin is not a specific DPP4i and also inhibits DPP8/9, which is involved in energy metabolism and immune regulation. The aim of this study is to evaluate how sitagliptin, vildagliptin or 1G244 (a DPP8/9 specific inhibitor) may influence cell viability, as well as osteogenic and adipogenic differentiation in human mesenchymal stem cells (MSC). Viability, apoptosis, osteoblastogenesis and adipogenesis markers, as well as protein synthesis of β-catenin, were studied in MSC cultures induced to differentiate into osteoblasts or adipocytes in the presence or absence of sitagliptin, vildagliptin or 1G244. The two tested DPP4i did not affect MSC viability, but 1G244 significantly decreased it in MSC and osteoblast-induced cells. Additionally, 1G244 and vildagliptin inhibited osteogenesis and adipogenesis, unlike sitagliptin. Therefore, inhibition of DPP4 did not affect MSC viability and differentiation, whereas inhibition of DPP8/9 negatively affected MSC. To the best of our knowledge, these results show for the first time that DPP8/9 have an important role in the viability and differentiation of human MSC. This data can be considered for human clinical use of drugs affecting DPP8/9 activity.

Therapeutic approach of natural products that treat osteoporosis by targeting epigenetic modulation

Osteoporosis (OP) is a metabolic disease that affects bone, resulting in a progressive decrease in bone mass, quality, and micro-architectural degeneration. Natural products have become popular for managing OP in recent years due to their minimal adverse side effects and suitability for prolonged use compared to chemically synthesized products. These natural products are known to modulate multiple OP-related gene expressions, making epigenetics an important tool for optimal therapeutic development. In this study, we investigated the role of epigenetics in OP and reviewed existing research on using natural products for OP management. Our analysis identified around twenty natural products involved in epigenetics-based OP modulation, and we discussed potential mechanisms. These findings highlight the clinical significance of natural products and their potential as novel anti-OP therapeutics.

LncRNA LINC00205 stimulates osteoporosis and contributes to spinal fracture through the regulation of the miR-26b-5p/KMT2C axis

BACKGROUND

Osteoporosis (OP) is a common bone disease marked by decreased bone strength. Increasing evidence suggests that long non-coding RNA (lncRNAs) play important roles in the occurrence and progression of OP. This study aimed to investigate the role and mechanism of LINC00205 in the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and OP.

METHODS

Bone tissue samples were obtained from healthy controls and patients with osteoporosis with a spinal fracture (OP-Frx) or without a spinal fracture (OP-no-Frx). HMSCs were cultured and induced to undergo osteogenic differentiation. The expression of LINC00205, lysine (K)-specific methyltransferase 2C (KMT2C), and miR-26b-5p in bone tissues and cells was evaluated using western blotting and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). The effects of LINC00205, miR-26b-5p, and KMT2C on calcium deposition, alkaline phosphatase (ALP) activity, and mRNA levels of the osteogenic differentiation marker genes [ALP, osteocalcin (OCN), and runt-related transcription factor 2 (RUNX2)] were investigated using alizarin red S staining, an ALP activity assay, and qRT-PCR, respectively. Dual-luciferase reporter assay was performed to ascertain the binding relationship between miR-26b-5p and LINC00205/KMT2C.

RESULTS

LINC00205 and KMT2C were upregulated in patients with OP-Frx and OP-no-Frx, whereas miR-26b-5p was downregulated. Furthermore, LINC00205 and KMT2C expression decreased, whereas that of miR-26b-5p increased over time from day 7 to 21 of the osteogenic differentiation of hMSCs. The knockdown of LINC00205 and KMT2C significantly increased ALP activity, calcium deposition, and the expression of RUNX2, ALP, and OCN. In contrast, the inhibition of miR-26b-5p yielded the opposite result. These data suggest that LINC00205 inhibits the osteogenic differentiation of hMSCs by modulating the miR-26b-5p/KMT2C signaling axis.

CONCLUSION

LINC00205 promotes OP and is involved in spinal fractures. LINC00205 is also a potential negative regulator of the osteogenic differentiation of hMSCs.

Progress of Wnt Signaling Pathway in Osteoporosis

Osteoporosis, one of the serious health diseases, involves bone mass loss, bone density diminishing, and degeneration of bone microstructure, which is accompanied by a tendency toward bone fragility and a predisposition to fracture. More than 200 million people worldwide suffer from osteoporosis, and the cost of treating osteoporotic fractures is expected to reach at least $25 billion by 2025. The generation and development of osteoporosis are regulated by genetic factors and regulatory factors such as TGF-β, BMP, and FGF through multiple pathways, including the Wnt signaling pathway, the Notch signaling pathway, and the MAPK signaling pathway. Among them, the Wnt signaling pathway is one of the most important pathways. It is not only involved in bone development and metabolism but also in the differentiation and proliferation of chondrocytes, mesenchymal stem cells, osteoclasts, and osteoblasts. Dkk-1 and SOST are Wnt inhibitory proteins that can inhibit the activation of the canonical Wnt signaling pathway and block the proliferation and differentiation of osteoblasts. Therefore, they may serve as potential targets for the treatment of osteoporosis. In this review, we analyzed the mechanisms of Wnt proteins, β-catenin, and signaling molecules in the process of signal transduction and summarized the relationship between the Wnt signaling pathway and bone-related cells. We hope to attract attention to the role of the Wnt signaling pathway in osteoporosis and offer new perspectives and approaches to making a diagnosis and giving treatment for osteoporosis.

Hypoxia During the Consolidation Phase of Distraction Osteogenesis Promotes Bone Regeneration

Background

Hypoxia is the critical driving force for angiogenesis and can trigger the osteogenic-angiogenic coupling followed by the enhancement of bone regeneration. While lots of studies showed that hypoxia administration can accelerate bone formation during distraction osteogenesis (DO), the therapeutic timing for the osteogenic purpose was concentrated on the distraction phase. The outcomes of hypoxia administration in the consolidation phase stay uncertain. The purpose of this study was to determine the osteogenic effectiveness of hypoxia therapy during the consolidation phase, if any, to enhance bone regeneration in a rat femoral DO model.

Methods

A total of 42 adult male Sprague-Dawley rats underwent right femoral mid-diaphysis transverse osteotomy and were randomly divided into Control (NS administration, n = 21) and Group1 (deferoxamine therapy, n = 21) after distraction. During the consolidation phase, Group1 was treated with local deferoxamine (DFO) injection into the distraction zone, while the Control underwent the same dosage of NS. Animals were sacrificed after 2, 4, and 6 weeks of consolidation. The process of bone formation and remodeling was monitored by digital radiographs, and the regenerated bone was evaluated by micro-computed tomography (micro-CT), biomechanical test, and histological analysis. The serum content of hypoxia-inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) were measured by enzyme linked immunosorbent assay (ELISA) for further analysis.

Results

Bone regeneration was significantly enhanced after hypoxia therapy during the consolidation phase. The digital radiograph, micro-CT, and biomechanical evaluation showed better effects regarding volume, continuity, and mechanical properties of the regenerated bone in Group1. The histomorphological evaluation also revealed the hypoxia treatment contributed to accelerate bone formation and remodeling during DO. The higher positive expression of angiogenic and osteogenic markers were observed in Group1 after hypoxia administration according to the immunohistochemical analysis. The serum content of HIF-1α and VEGF was also increased after hypoxia therapy as evidenced from ELISA.

Conclusion

Hypoxia administration during the consolidation phase of distraction osteogenesis has benefits in enhancing bone regeneration, including accelerates the bone formation and remodeling.

Effects of urolithin A on osteoclast differentiation induced by receptor activator of nuclear factor-κB ligand via bone morphogenic protein 2

Urolithin A (UA) is an intestinal microbial metabolite derived from ellagitannins and a promising agent for treating osteoarthritis. However, its effects on osteoporosis are unclear. This study explored the effects of urolithin A (UA) on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclasts and its underlying molecular mechanisms. RANKL treatment significantly increased tartrate-resistant acid phosphatase (TRACP) or osteoclast marker levels (P < 0.05), while adding UA decreased the RANKL-induced levels (P < 0.05) in RAW264.7 cells. Total RNA isolated from RANKL- or RANKL + UA-treated cells was sequenced, and the obtained transcriptome dataset revealed 2,399 differentially expressed genes. They were enriched in multiple pathways involved in rheumatoid arthritis, ERK1 and ERK2 cascade, regulation of inflammatory response, ECM-receptor interactions, and TNF signaling. Scanning electron microscopy showed that RANKL promoted bone resorption pits in bone biopsy specimens, whereas UA inhibited their formation. When bone morphogenic protein 2 (BMP2) was shRNA-silenced, the bone resorption pits were restored. Moreover, while RANKL significantly enhanced the levels of p-ERK2/ERK2, p-p38/p38, p-Akt1/Akt1, p-ERK1/ERK1, and osteoclast-related proteins (P < 0.05), UA reduced them. BMP2 silencing also reversed the UA inhibitory effect. Thus, UA represses the RANKL-induced osteoclast differentiation of RAW264.7 cells by regulating Akt1, p38, and ERK1/2 signaling, and BMP2 likely reverses the UA inhibitory effect via these pathways. We propose BMP2 as a potential drug target for treating bone metabolic diseases, such as osteoporosis.

Epidermal growth factor-like domain protein 6 recombinant protein facilitates osteogenic differentiation in adipose stem cells via bone morphogenetic protein 2/recombinant mothers against decapentaplegic homolog 4 signaling pathway

Adipose-derived mesenchymal stem cells (ADSCs) are a class of pluripotent stem cells isolated from the adipose tissue; they can differentiate into osteoblasts after induction and play an important role in bone repair. EGFL6 protein is secreted by adipocytes and osteoblasts and can promote endothelial cell migration and angiogenesis. This study aimed to explore the effect of recombinant EGFL6 protein on the osteogenic differentiation of ADSCs. The cells were incubated with fluorescein isothiocyanate-conjugated antibodies and analyzed by flow cytometry. Alizarin red staining and alkaline phosphatase staining were used to detect the osteogenic differentiation ability. mRNA expression was analyzed by real-time quantitative polymerase chain reaction (RT-qPCR). Protein expression was determined using Western blotting. The osteogenic differentiation ability of ADSCs isolated from the adipose tissue was significantly weakened after EGFL6 knockdown; this ability was restored upon the addition of EGFL6 recombinant protein. BMP2 knockdown inhibited the effect of EGFL6 recombinant protein on osteogenic differentiation. EGFL6 recombinant protein promoted osteogenic differentiation of ADSCs through the BMP2/SMAD4 signaling pathway. This may provide a potential target for the osteogenic differentiation of ADSCs.

Linagliptin in Combination With Metformin Ameliorates Diabetic Osteoporosis Through Modulating BMP-2 and Sclerostin in the High-Fat Diet Fed C57BL/6 Mice

BACKGROUND

Diabetic osteoporosis is a poorly managed serious skeletal complication, characterized by high fracture risk, increased bone resorption, reduced bone formation, and disrupted bone architecture. There is a need to investigate drugs that can improve bone health along with managing glycemic control. DPP-4 inhibitors and metformin have proven benefits in improving bone health. Here, we investigated the effects of linagliptin, a DPP inhibitor, and metformin alone and in combination to treat diabetic osteoporosis in high-fat-fed mice.

METHODS

C57BL/6 mice were kept on the high-fat diet (HFD) for 22 weeks to induce diabetic osteoporosis. Linagliptin (10mg/Kg), metformin (150mg/Kg), and their combination were orally administered to the diabetic mice from the 18^th-22^nd week. Femur and tibial bone microarchitecture together with bone mineral density (BMD) were evaluated using µCT and histopathological changes were assessed. Further, bone turnover biomarkers namely bone morphogenetic protein-2 (BMP-2), sclerostin, tartrate-resistant acid phosphatase (TRAP), osteocalcin, alkaline phosphatase (ALP), calcium, and pro-inflammatory cytokines were assessed. Additionally, metabolic parameters including body weight, fasting blood glucose (FBG), glucose & insulin tolerance, lipids profile, and leptin were measured.

RESULTS

HFD feeding resulted in impaired bone microarchitecture, reduced BMD, distorted bone histology, and altered bone turnover biomarkers as indicated by the significant reduction in bone ALP, BMP-2, osteocalcin, and an increase in sclerostin, TRAP, and serum calcium. Interestingly, treatment with linagliptin and its combination with metformin significantly reverted the impaired bone architecture, BMD, and positively modulated bone turnover biomarkers, while metformin alone did not exhibit any significant improvement. Further, HFD induced diabetes and metabolic abnormalities (including an increase in body weight, FBG, impaired glucose and insulin tolerance, leptin, triglycerides, cholesterol), and pro-inflammatory cytokines (TNF-alpha and IL-1β) were successfully reversed by treatment with linagliptin, metformin, and their combination.

CONCLUSION

Linagliptin and its combination with metformin successfully ameliorated diabetic osteoporosis in HFD-fed mice possibly through modulation of BMP-2 and sclerostin. The study provides the first evidence for the possible use of linagliptin and metformin combination for managing diabetic osteoporosis.

Osteopontin, a bridge links osteoarthritis and osteoporosis

Osteoarthritis (OA) is the most prevalent joint disease characterized by degradation of articular cartilage, inflammation, and changes in periarticular and subchondral bone of joints. Osteoporosis (OP) is another systemic skeletal disease characterized by low bone mass and bone mineral density (BMD) accompanied by microarchitectural deterioration in bone tissue and increased bone fragility and fracture risk. Both OA and OP are mainly affected on the elderly people. Recent studies have shown that osteopontin (OPN) plays a vital role in bone metabolism and homeostasis. OPN involves these biological activities through participating in the proliferation, migration, differentiation, and adhesion of several bone-related cells, including chondrocytes, synoviocytes, osteoclasts, osteoblasts, and marrow mesenchymal stem cells (MSCs). OPN has been demonstrated to be closely related to the occurrence and development of many bone-related diseases, such as OA and OP. This review summarizes the role of OPN in regulating inflammation activity and bone metabolism in OA and OP. Furthermore, some drugs that targeted OPN to treat OA and OP are also summarized in the review. However, the complex mechanism of OPN in regulating OA and OP is not fully elucidated, which drives us to explore the depth effect of OPN on these two bone diseases.

MicroRNA miR-874-3p inhibits osteoporosis by targeting leptin (LEP)

MicroRNAs (miRNAs) regulate osteogenic differentiation and influence osteoporosis (OP). The aim of this study was to determine the potential role of miR-874-3p in OP. The expression levels of miR-874-3p and leptin (LEP) in the femoral neck trabeculae of 35 patients with or without OP were measured by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The effects of miR-874-3p or LEP on the cell proliferation and alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), osteocalcin (OCN), and osterix (OSX) levels were observed by upregulating miR-874-3p in human bone marrow mesenchymal stem cells (hBMSCs). Additionally, calcium deposition levels were evaluated using alizarin red staining (ARS). Molecular mechanisms of miR-874-3p and LEP underlying the osteogenic differentiation of hBMSCs were also evaluated using bioinformatics analysis, luciferase reporter assays, and RNA pull-down assays. The miR-874-3p levels were significantly lower in the femoral neck trabeculae of patients with OP than those of the control group, while the opposite was observed regarding the levels of LEP. Expression levels of miR-874-3p in hBMSCs were upregulated during osteogenic differentiation, while those of LEP were downregulated. Moreover, miR-874-3p upregulation promoted ALP, RUNX2, OCN, and OSX mRNA expression, cell proliferation, and calcium deposition in hBMSCs. LEP was found to be a target gene of miR-874-3p. Overexpression of LEP inhibited the expression of osteoblast markers and reversed the effect of osteogenic differentiation induced by the upregulation of miR-874-3p. In conclusion, miR-874-3p promoted the proliferation and differentiation of hBMSCs by downregulating the expression of LEP, thus inhibiting OP.

Abbreviations : miRNAs: microRNAs; OP: osteoporosis; hBMSCs: human Bone Marrow Mesenchymal stem cells; LEP: leptin; DEGs: differentially expressed genes

Circular RNA Circ_0005564 promotes osteogenic differentiation of bone marrow mesenchymal cells in osteoporosis

Circular RNA (CircRNA) plays a potential role in bone formation. We aimed to study the circRNAs expression profiles and their functions in osteogenic differentiation of human bone marrow stromal cells (BMSCs). Firstly, we established osteogenic differentiation of BMSCs displaying increased mRNA expression of osteogenic differentiation marker (RUNX2, OPN, and OCN), increased ALP activity and protein expression, and increased mineralized nodules formation, as well as morphological alteration. Then, we employed high-throughput sequencing to analyze circRNA expression and found that 3440 and 3893 circRNAs in non-induced and induced groups, respectively. We further validated the 10 differentially expressed circRNAs with the most significant difference between induced and non-induced groups. Among these ten circRNAs, five of them with more than one miRNA binding site were used to construct a ceRNA network exhibiting 81 miRNAs and 182 target mRNAs. Furthermore, among these five circRNAs, we found only circ_0005564 significantly reduced the mRNA expression of RUNX2, OPN, and OCN. The circularity of circ_0005564 was verified. Our results showed that knockdown of circ_0005564 inhibited osteoblast differentiation in BMSCs. Taken together, our study demonstrates that circ_0005564 is a potential positive regulator of osteogenic differentiation of BMSCs.

Inhibitory effect of Astragalus Membranaceus on osteoporosis in SAMP6 mice by regulating vitaminD/FGF23/Klotho signaling pathway

Spontaneous senile osteoporosis severely threatens the health of the senior population which has emerged as a severe issue for society. A SAMP6 mouse model was utilized to estimate the impact of intragastrically administered Astragalus Membranaceus (AR) on spontaneous senile osteoporosis. Bone mineral density (BMD) and bone microstructure were measured using Micro-CT; contents of calcium and phosphorus were determined with the colorimetric method; and gene and protein expressions of fibroblast growth factor 23 (FGF23), Klotho, Vitamin D receptor (VDR), CYP27B1 and CYP24A1 were detected using qPCR, Western blot and ELISA assays, respectively. The findings indicated that AR could improve the femoral BMD and bone microstructure, elevate the contents of calcium and phosphorus, and increase the expression of Klotho, VDR, and CYP27B1 whereas decreasing the expression of FGF23 and CYP24A1 in SAMP6 mice in a dose independent manner. The present study has demonstrated that AR can promote osteogenesis and alleviate osteoporosis. It is also expected to provide a new insight for the treatment of spontaneous senile osteoporosis and to serve as a research basis for AR application.

Relationship between miRNA-433 and SPP1 in the presence of fracture and traumatic brain injury

Limb fracture combined with traumatic brain injury (TBI) is one of the most common multiple injuries and patients often suffer from severe craniocerebral injury combined with long bone fracture of the limbs. The present study examined the expression of osteopontin (SPP1) in the tibial fracture callus and heterotopic ossification tissues in craniocerebral injury and investigated its relationship with miR-433. A total of 26 patients with tibial fracture combined with brain injury were included in the TBI group, and 26 patients with simple tibial fracture were included in the control group. The patients received immobilization treatment and callus was collected during the operation. At the time of steel plate removal tissue ossification samples from patients with heterotopic ossification were collected. Peripheral blood was collected from all patients on the morning of the operation day. Expression of miR-433 and SPP1 mRNA was determined by reverse transcription-quantitative PCR and SPP1 protein expression was measured by western blotting. Dual luciferase reporter assay was used to identify the direct interaction between miR-433 and SPP1 mRNA. The human osteoblast line hFOB1.19 was transfected with agomiR-433 to overexpress miR-433 and expression of SPP1 was also examined. TBI enhanced the incidence of callus formation and heterotopic ossification in patients with fracture but did not alter fracture healing time. SPP1 mRNA and protein expression was elevated in patients who had tibial fracture in combination with craniocerebral injury in comparison with controls By contrast, expression of miR-433 was decreased in patients who had tibial fracture in combination with craniocerebral injury in comparison with controls. miR-433 regulated the expression of SPP1 mRNA and protein by directly binding to the 3'-untranslated region of SPP1 mRNA. The present study suggests that SPP1 mRNA and protein levels are increased in the callus, heterotopic ossification tissues and plasma from patients with tibial fracture combined with brain injury in comparison with controls. This elevation may be due to the reduced expression of miR-433.