Regulation Of Osteoblasts Research Articles

P53 deficiency promotes bone regeneration by functional regulation of mesenchymal stromal cells and osteoblasts.

The detailed mechanism of the process during bone healing of drill-hole injury has been elucidated, but a crucial factor in regulating drill-hole healing has not been identified. The transcription factor p53 suppresses osteoblast differentiation through inhibition of osterix expression. In present study, we demonstrate the effects of p53 deficiency on the capacity of MSCs and osteoblasts during drill-hole healing. Mesenchymal stromal cells (MSCs) and osteoblasts were collected from bone marrow and calvaria of p53 knockout (KO) mice, respectively. The activities of cell mobility, cell proliferation, osteoblast differentiation, and wound healing of MSCs and/or osteoblasts were determined by in vitro experiments. In addition, bone healing of drill-hole injury in KO mice was examined by micro-CT and immunohistological analysis using anti-osterix, Runx2, and sclerostin antibodies. KO MSCs stimulated cell mobility, cell proliferation, and osteoblast differentiation. Likewise, KO osteoblasts enhanced cell proliferation and wound healing. KO MSCs and osteoblasts showed high potency in the inflammation and callus formation phases compared to those from wild-type (WT) mice. In addition, increased expression of osterix and Runx2 was observed in KO MSCs and osteoblasts that migrated in the drill-hole. Conversely, sclerostin expression was inhibited in KO mice. Eventually, KO mice exhibited high repairability of drill-hole injury, suggesting a novel role of p53 in MSCs and osteoblasts in improving bone healing. p53 Deficiency promotes bone healing of drill-hole injury by enhancing the bone-regenerative ability of MSCs and osteoblasts.

Research Progress of the Role of Anthocyanins on Bone Regeneration.

Bone regeneration in osteoporosis and fragility fractures which are highly associated with age remains a great challenge in the orthopedic field, even though the bone is subjected to a continuous process of remodeling which persists throughout lifelong. Regulation of osteoblast and osteoclast differentiation is recognized as effective therapeutic targets to accelerate bone regeneration in osteopenic conditions. Anthocyanins (ACNs), a class of naturally occurring compounds obtained from colored plants, have received increasing attention recently because of their well-documented biological effects, such as antioxidant, anti-inflammation, and anti-apoptosis in chronic diseases, like osteoporosis. Here, we summarized the detailed research progress on ACNs on bone regeneration and their molecular mechanisms on promoting osteoblast differentiation as well as inhibiting osteoclast formation and differentiation to explore their promising therapeutic application in repressing bone loss and helping fragility fracture healing. Better understanding the role and mechanisms of ACNs on bone regeneration is helpful for the prevention or treatment of osteoporosis and also for the exploration of new bone regenerative medicine.

Signaling Pathway and Transcriptional Regulation in Osteoblasts during Bone Healing: Direct Involvement of Hydroxyapatite as a Biomaterial.

Bone defects and periodontal disease are pathological conditions that may become neglected diseases if not treated properly. Hydroxyapatite (HA), along with tricalcium phosphate and bioglass ceramic, is a biomaterial widely applied to orthopedic and dental uses. The in vivo performance of HA is determined by the interaction between HA particles with bone cells, particularly the bone mineralizing cells osteoblasts. It has been reported that HA-induced osteoblastic differentiation by increasing the expression of osteogenic transcription factors. However, the pathway involved and the events that occur in the cell membrane have not been well understood and remain controversial. Advances in gene editing and the discovery of pharmacologic inhibitors assist researchers to better understand osteoblastic differentiation. This review summarizes the involvement of extracellular signal-regulated kinase (ERK), p38, Wnt, and bone morphogenetic protein 2 (BMP2) in osteoblastic cellular regulation induced by HA. These advances enhance the current understanding of the molecular mechanism of HA as a biomaterial. Moreover, they provide a better strategy for the design of HA to be utilized in bone engineering.

Regulation of Bone Cell Differentiation and Activation by Microbe-Associated Molecular Patterns.

Gut microbiota has emerged as an important regulator of bone homeostasis. In particular, the modulation of innate immunity and bone homeostasis is mediated through the interaction between microbe-associated molecular patterns (MAMPs) and the host pattern recognition receptors including Toll-like receptors and nucleotide-binding oligomerization domains. Pathogenic bacteria such as Porphyromonas gingivalis and Staphylococcus aureus tend to induce bone destruction and cause various inflammatory bone diseases including periodontal diseases, osteomyelitis, and septic arthritis. On the other hand, probiotic bacteria such as Lactobacillus and Bifidobacterium species can prevent bone loss. In addition, bacterial metabolites and various secretory molecules such as short chain fatty acids and cyclic nucleotides can also affect bone homeostasis. This review focuses on the regulation of osteoclast and osteoblast by MAMPs including cell wall components and secretory microbial molecules under in vitro and in vivo conditions. MAMPs could be used as potential molecular targets for treating bone-related diseases such as osteoporosis and periodontal diseases.

Gene expression of intracortical bone demonstrates loading-induced increases in Wnt1 and Ngf and inhibition of bone remodeling processes.

Osteocytes are the primary mechanosensitive cells in bone. However, their location in mineralized matrix has limited the in vivo study of osteocytic genes induced by mechanical loading. Laser Capture Microdissection (LCM) allows isolation of intracortical bone (Intra-CB), enriched for osteocytes, from bone tissue for gene expression analysis. We used microarray to analyze gene expression from mouse tibial Intra-CB dissected using LCM 4h after a single loading bout or after 5days of loading. Osteocyte enrichment was supported by greater expression of Sost, Dmp1, Dkk1, and Mepe in Intra-CB regions vs. Mixed regions containing periosteum and muscle (fold-change (FC)=3.4, 2.2, 5.1, 3.0, respectively). Over 150 differentially expressed genes (DEGs) due to loading (loaded vs. contralateral control) in Intra-CB were found on Day 1 and Day 5, but only 10 genes were differentially expressed on both days, including Ngf (Day 1 FC=13.5, Day 5 FC=11.1) and Wnt1 (Day 1 FC=1.5, Day 5 FC=5.1). The expression of Ngf and Wnt1 within Intra-CB was confirmed by in situ hybridization, and a significant increase in number of Wnt1 mRNA molecules occurred on day 1. We also found changes in extracellular matrix remodeling with Timp1 (FC=3.1) increased on day 1 and MMP13 (FC=0.3) decreased on day 5. Supporting this result, IHC for osteocytic MMP13 demonstrated a marginal decrease due to loading on day 5. Gene Ontology (GO) biological processes for loading DEGs indicated regulation of vasculature, neuronal and immune processes while cell-type specific gene lists suggested regulation of osteoclast, osteoblast, and endothelial related genes. In summary, microarray analysis of microdissected Intra-CB revealed differential regulation of Ngf, Wnt1, and MMP13 due to loading in osteocytes.

Pitavastatin prevents ovariectomy-induced osteoporosis by regulating osteoclastic resorption and osteoblastic formation

Excessive osteoclast activity, along with relatively weak osteoblast function, is strongly associated with bone disease. Therefore, studies to identify novel anti-osteoporosis candidates with dual actions of inhibiting osteoclastogenesis and increasing osteoblastogenesis may provide an ideal approach for treating osteoporosis. Pitavastatin, an inhibitor of 3-hydroxy-3 methyl-glutaryl coenzyme A reductase, has demonstrated various pharmacological activities, including anti-inflammation, bone anabolic effects, vasodilation, and inhibition of revascularization; however, the precise effects and mechanisms of pitavastatin on the regulation of osteoblast and osteoclast activity need to be comprehensively elucidated. Herein, we demonstrated that pitavastatin is a potential candidate for treating osteoporosis by enhancing osteoblast differentiation and bone growth and inhibiting osteoclast differentiation and bone resorption. Pitavastatin exerted dose-dependent inhibitory effects on receptor activator of nuclear factor kappa-B ligand-induced osteoclast formation, bone resorption, and osteoclast-specific marker gene expression. These inhibitory effects were achieved by inhibiting the Akt, NF-κB, and mitogen-activated protein kinase (p38, ERK, and JNK) signaling pathways, resulting in the downregulation of major transcription factors c-Fos and NFATc1. Furthermore, pitavastatin potentially stimulated osteoblast differentiation by activating alkaline phosphatase (ALP), enhancing mineralization by Alizarin Red S, and increasing the expression of osteoblastogenic marker genes such as runt-related transcription factor 2, ALP, osteocalcin, and collagen type 1 alpha. Furthermore, we evaluated the therapeutic potential of pitavastatin in ovariectomy-induced systematic bone loss based on micro-computed tomography and histological analysis of femurs. Our findings demonstrated a new function and mechanism for pitavastatin in bone remodeling, indicating its potential as a therapeutic candidate in treating osteoporosis by inhibiting osteoclastic resorption and promoting osteoblastic formation.

Computational Fine-Tuning of Functional Single Nucleotide Polymorphisms Associated with ACP5 Gene to Characterize Missense Mutations

Acid phosphatase 5 (ACP5) gene plays a vibrant role in the synthesis of a tartrate-resistant acid phosphatase (TRAP5) enzyme. TRAP5 is ~35 KD glycosylated di-iron metalloenzyme responsible for the regulation of osteopontin (protein) activity. There are two isoforms of TRAP5, TRAP5a, and TRAP5b. TRAP5a functions with low enzymatic activity due to a loop interacting with the active site and the more active TRAP5b is generated upon proteolytic cleavage of this loop. TRAP5a works as a marker for systematic macrophage function and chronic inflammation activity, while TRAP5b for osteoclast activity. ACP5 is evolutionarily conserved in nature and acts as a multifunctional protein that involves generations of reactive oxygen species, normal bone development, macrophage function, and osteoblast regulation, affecting a series of pathways, as well as reflecting bone resorption and osteoclast activity. To understand its fundamental role, a functional investigation of missense mutations of the ACP5 gene was carried out through an in-silico approach. Two nsSNPs G109R and L201P were predicted to be deleterious using multiple computational tools like SIFT, Polyphen-1, PolyPhen-2, MAPP, SNAP, Predict SNP and PhD-SNP. Additionally, the structural analysis was performed. The result is that there was no similarity between the native and mutant structures. Therefore, these reported mutations in ACP5 modify the expression, function, and structure of a TRAP5 protein. These findings suggest that TRAP5 can be a therapeutic target in immunological disorders, cancer, and metabolic bone diseases. These deleterious mutations can be lethal to its function and may hamper its therapeutic strategy leading to various diseases such as autoimmune cytopenia, systemic lupus erythematosus (SLE) immune-osseous dysplasia, spasticity with leukodystrophy, moyamoya syndrome, and sjogren's syndrome.

Cyanidin-3-glucoside Regulates Osteoblast Differentiation via the ERK1/2 Signaling Pathway.

Osteoporosis, characterized by a gradual decrease in the number of osteoblasts and a gradual increase in bone resorption of osteoclasts in bone tissue, is a global chronic disease, which severely impairs the quality of life of the elderly. Therefore, it is extremely urgent to study the prevention and treatment of osteoporosis. It has been reported that anthocyanins can regulate bone metabolism and prevent osteoporosis. Cyanidin-3-O-glucoside (C3G), the most common type of anthocyanin in nature, widely exists in a variety of vegetables and fruits. Although it has been shown that C3G has multiple effects on osteoclasts, its impact(s) and underlying mechanism(s) on osteoblasts are still not clear. Here, we evaluated the effect of C3G on cell proliferation and differentiation of osteoblasts (extracted from the hip joint of patients with osteoporosis) and MC3T3-E1 (a kind of osteoblast cell line from mice). We also test the ability of osteoblasts to mineralize after C3G treatment. To find the underlying mechanism of the above effects, we further evaluated the role of the ERK signaling pathway in C3G regulation of osteoblasts. The results showed that C3G treatment enhanced osteoblast proliferation rate, osteoblast mineralization points, the mRNA levels and protein expression levels of OC (osteocalcin), and the level of ERK phosphorylation, which could be blocked by pretreatment with ERK signaling pathway inhibitor. The above results not only indicate that the ERK pathway was involved in C3G regulation of osteoblast differentiation but also provide strong suggestive evidence that osteoblasts may be promising targets in preventive and therapeutic strategies for osteoporosis.

Transcriptomic alterations underline aging of osteogenic bone marrow stromal cells.

BACKGROUNDMultipotent bone marrow stromal cells (BMSCs) are adult stem cells that form functional osteoblasts and play a critical role in bone remodeling. During aging, an increase in bone loss and reduction in structural integrity lead to osteoporosis and result in an increased risk of fracture. We examined age-dependent histological changes in murine vertebrae and uncovered that bone loss begins as early as the age of 1 mo. AIMTo identify the functional alterations and transcriptomic dynamics of BMSCs during early bone loss. METHODSWe collected BMSCs from mice at early to middle ages and compared their self-renewal and differentiation potential. Subsequently, we obtained the transcriptomic profiles of BMSCs at 1 mo, 3 mo, and 7 mo. RESULTSThe colony-forming and osteogenic commitment capacity showed a comparable finding that decreased at the age of 1 mo. The transcriptomic analysis showed the enrichment of osteoblastic regulation genes at 1 mo and loss of osteogenic features at 3 mo. The BMSCs at 7 mo showed enrichment of adipogenic and DNA repair features. Moreover, we demonstrated that the WNT and MAPK signaling pathways were upregulated at 1 mo, followed by increased pro-inflammatory and apoptotic features. CONCLUSIONOur study uncovered the cellular and molecular dynamics of bone aging in mice and demonstrated the contribution of BMSCs to the early stage of age-related bone loss.

Osteogenic Response of MC3T3-E1 and Raw264.7 in the 3D-Encapsulated Co-Culture Environment.

Three-dimensional (3D) in vitro cultures recapitulate the physiological microenvironment and exhibit high concordance with in vivo conditions. Improving co-culture models with different kind of cell types cultured on a 3D scaffold can closely mimic the in vivo environment. In this study, we examined the osteogenic response of pre-osteoblast MC3T3-E1 cells and Raw264.7 mouse monocytes in a 3D-encapsulated co-culture environment composed of the Cellrix® 3D culture system, which provides a physiologically relevant environment. The Cellrix® 3D Bio-Gel scaffolds were used to individually culture or co-culture two type cells in 3D microenvironment. Under 3D culture conditions, osteoblastic behavior was evaluated with an ALP assay and staining. ACP assay and TRAP staining were used as osteoclastic behavior indicator. Treatment with osteoblastic induction factors (+3F) and RANKL had on positively effect on alkaline phosphatase activity but significantly inhibited to acid phosphatase activity during osteoclastic differentiation in 3D co-culture. Interestingly, alkaline phosphatase activity or acid phosphatase activity in 3D co-culture was stimulated with opposite differentiation factors at an early stage of differentiation. We guess that these effects may be related to RANK-RANKL signaling, which is important in osteoblast regulation of osteoclasts. In this study, the osteogenic response of 3D encapsulated pre-osteoblast MC3T3-E1 cells and mouse monocyte Raw264.7 cells was successfully demonstrated. Our 3D culture conditions will be able to provide a foundation for developing a high-throughput in vitro bone model to study the effects of various drugs and other agents on molecular pathways.

Genetics and Genomics of SOST: Functional Analysis of Variants and Genomic Regulation in Osteoblasts.

SOST encodes the sclerostin protein, which acts as a key extracellular inhibitor of the canonical Wnt pathway in bone, playing a crucial role in skeletal development and bone homeostasis. The objective of this work was to assess the functionality of two variants previously identified (the rare variant rs570754792 and the missense variant p.Val10Ile) and to investigate the physical interactors of the SOST proximal promoter region in bone cells. Through a promoter luciferase reporter assay we show that the minor allele of rs570754792, a variant located in the extended TATA box motif, displays a significant decrease in promoter activity. Likewise, through western blot studies of extracellular and intracellular sclerostin, we observe a reduced expression of the p.Val10Ile mutant protein. Finally, using a circular chromosome conformation capture assay (4C-seq) in 3 bone cell types (MSC, hFOB, Saos-2), we have detected physical interactions between the SOST proximal promoter and the ECR5 enhancer, several additional enhancers located between EVT4 and MEOX1 and a distant region containing exon 18 of DHX8. In conclusion, SOST presents functional regulatory and missense variants that affect its expression and displays physical contacts with far reaching genomic sequences, which may play a role in its regulation within bone cells.

Soft tissue injury in the limbs increased regional bone turnover

Pathological conditions after skeletal tissue injury such as trauma and surgical intervention are often accompanied with regional osteoporotic changes, which are recognized to be mainly caused by limb immobility after injury. However, the mechanisms for the progression of regional osteoporotic changes related to the injury remains unknown. Previous studies reported that the pathophysiological conditions related to tissue injury include the acidic micro-environment formation and increased ATP levels. In addition, we previously demonstrated that those changes in the micro-environment induced a high bone turnover state through the activation of TRPV1, ASICs and P2X expressed in bone cells. We, therefore, hypothesized that tissue injury could enhance a high bone turnover state due to those pathophysiological changes in soft tissue in the injured limb. The aim of this study was to examine whether soft tissue injury associated with cutaneous incisions in a limb affects regional bone turnover. Eight-week-old male C57BL/6J mice underwent soft tissue injury associated with cutaneous incisions in the right femoral skin. During the 14 days after the incision, changes in the expression of osteoblast and osteoclast differentiation regulators and ATP were evaluated in comparison with those in uninjured mice. The pain-like behaviors and the expression of those differentiation regulators with and without treatment with bisphosphonate and Cox2 inhibitor were assessed in the injured limb. Consistent with the wound healing process, the expression levels of Osterix, osteocalcin and RANKL in the femur of the incised limb were significantly increased up to 7 days, and then decreased to the same level as those in the control limbs by 14 days after the incisions. The levels of TRAP 5b and ATP were initially significantly increased, and then decreased to the same level as before injury by day 14. Bisphosphonate significantly improved the pain-like behaviors in the injured limb associated with the inhibition of osteoblast and osteoclast differentiation regulators. We believe that the pathophysiological changes in soft tissue resulting from cutaneous incisions could be related to the induction of osteoblast and osteoclast differentiation regulators.

Osteocyte-derived exosomes inhibit osteoblast activity and induce osteoclast formation

Osteocytes, which are the most abundant cell type in bone, regulate osteoblasts and osteoclasts via both cell–cell interactions and paracrine signaling, and osteocyte-derived exosomes might contribute to this paracrine action. In this study, we investigated the effects of osteocyte-derived exosomes on regulating osteoblasts and osteoclasts and studied the potential mechanism. Materials and Methods: Osteocyte-derived exosomes were extracted and identified. PKH67-labeled exosomes were incubated with MC3T3-E1 cells and RAW264.7 cells, and fluorescence confocal microscopy was used to analyze the uptake of exosomes. ALP stain- ing and TRAP staining were used to analyze osteoblast activity and osteoclast formation. The level of miR-214-3p in exosomes was analyzed by qPCR and the incorporation of FAM-labeled miR-214-3p from exosomes into MC3T3-E1 cells was evaluated. The expressions of ephrinA2 and RANKL in exosomes were studied. Results: Our results demonstrated that osteocyte-derived exosomes might recognize osteoblasts through the ephrinA2 protein; thus, miR-214-3p in exosomes was transferred into osteoblasts to inhibit osteoblast activity. Meanwhile, we found that osteocyte-derived exosomes could be transferred into osteoclasts to induce osteoclast formation by releasing RANKL. Conclusion: These findings suggest that osteocyte-derived exosomes play an important role in the regulation of osteoblast and osteoclast activity, which might occur via miR-214-3p and RANKL.

Lecithin-Cholesterol Acyltransferase Induced By  <i>PPSacα</i> Deficiency in Liver Regulates the Homeostasis of Liver/Bone Axis and Ameliorates Hepatic Osteodystrophy Diseas

Hepatic osteodystrophy (HOD) is a metabolic bone disease caused by chronic liver injuries and complicated with osteopenia or osteoporosis. Here, we identified LCAT as a hepatokine, regulated by PP2Acα, which prevents bone loss, as well as ameliorates chronic liver injury. Conversely, loss of function of LCAT markedly exacerbated the bone loss phenotype of HOD. Mechanistically, we found that LCAT activation is mediated by PP2Acα/USF1 signaling and demonstrated that alteration of the cholesterol levels is involved in the regulation of osteoblast and osteoclast activities. Additionally, LCAT improves the liver fibrosis and liver function by reversing cholesterol transport in HOD. In summary, we discovered that PP2A-regulated hepatokine LCAT controls HOD by maintaining the balance of the liver-bone axis.

Def6 regulates endogenous type-I interferon responses in osteoblasts and suppresses osteogenesis.

Bone remodeling involves a balance between bone resorption and formation. The mechanisms underlying bone remodeling are not well understood. DEF6 is recently identified as a novel loci associated with bone mineral density. However, it is unclear how Def6 impacts bone remodeling. We identify Def6 as a novel osteoblastic regulator that suppresses osteoblastogenesis and bone formation. Def6 deficiency enhances both bone resorption and osteogenesis. The enhanced bone resorption in Def6-/- mice dominates, leading to osteoporosis. Mechanistically, Def6 inhibits the differentiation of both osteoclasts and osteoblasts via a common mechanism through endogenous type-I IFN-mediated feedback inhibition. RNAseq analysis shows expression of a group of IFN stimulated genes (ISGs) during osteoblastogenesis. Furthermore, we found that Def6 is a key upstream regulator of IFNβ and ISG expression in osteoblasts. Collectively, our results identify a novel immunoregulatory function of Def6 in bone remodeling, and shed insights into the interaction between immune system and bone.

Synthetic Function and Regulation of Osteoblasts: Current Knowledge and Applications

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The diverse origin of bone-forming osteoblasts.

Osteoblasts are the only cells that can give rise to bones in vertebrates. Thus, one of the most important functions of these metabolically active cells is mineralized matrix production. Because osteoblasts have a limited lifespan, they must be constantly replenished by preosteoblasts, their immediate precursors. Because disruption of the regulation of bone-forming osteoblasts results in a variety of bone diseases, a better understanding of the origin of these cells by defining the mechanisms of bone development, remodeling, and regeneration is central to the development of novel therapeutic approaches. In recent years, substantial new insights into the origin of osteoblasts-largely owing to rapid technological advances in murine lineage-tracing approaches and other single-cell technologies-have been obtained. Collectively, these findings indicate that osteoblasts involved in bone formation under various physiological, pathological, and therapeutic conditions can be obtained from numerous sources. The origins of osteoblasts include, but are not limited to, chondrocytes in the growth plate, stromal cells in the bone marrow, quiescent bone-lining cells on the bone surface, and specialized fibroblasts in the craniofacial structures, such as sutures and periodontal ligaments. Because osteoblasts can be generated from local cellular sources, bones can flexibly respond to regenerative and anabolic cues. However, whether osteoblasts derived from different cellular sources have distinct functions remains to be investigated. Currently, we are at the initial stage to aptly unravel the incredible diversity of the origins of bone-forming osteoblasts. © 2021 American Society for Bone and Mineral Research (ASBMR).

Green Tomato Extract Prevents Bone Loss in Ovariectomized Rats, a Model of Osteoporosis.

Although drug therapies are available for postmenopausal osteoporosis, these drugs are not free of side effects and long-term adherence to them are low. A safe and effective nutritional approach to counter postmenopausal osteoporosis is an important research goal. We fed ovariectomized (OVX) Sprague–Dawley rats a diet supplemented with 1% or 2% green tomato extract (GTE). After 12 weeks, micro-computed tomography scans revealed that GTE supplementation effectively prevented distal femur bone loss. This prevention was due to improved bone formation and suppressed bone resorption as observed by the regulation of osteoblast and osteoclast activities. GTE supplementation also improved bone formation through Bmp2-Smad 1/5/8-Runx2 signaling, while bone resorption was regulated by the receptor activator of nuclear factor kappa-B (RANKL)/osteoprogeterin (OPG) pathway. These results suggest that GTE supplementation prevents severe postmenopausal bone loss by maintaining the regulation of bone homeostasis in OVX rats. GTE as a diet supplement might be a potential novel alternative for the prevention of postmenopausal osteoporosis.

Hydroxyapatite-modified micro/nanostructured titania surfaces with different crystalline phases for osteoblast regulation

Surface structures and physicochemical properties critically influence osseointegration of titanium (Ti) implants. Previous studies have shown that the surface with both micro- and nanoscale roughness may provide multiple features comparable to cell dimensions and thus efficiently regulate cell-material interaction. However, less attention has been made to further optimize the physicochemical properties (e.g., crystalline phase) and to further improve the bioactivity of micro/nanostructured surfaces. Herein, micro/nanostructured titania surfaces with different crystalline phases (amorphous, anatase and anatase/rutile) were prepared and hydroxyapatite (HA) nanorods were deposited onto the as-prepared surfaces by a spin-assisted layer-by-layer assembly method without greatly altering the initial multi-scale morphology and wettability. The effects of crystalline phase, chemical composition and wettability on osteoblast response were investigated. It is noted that all the micro/nanostructured surfaces with/without HA modification presented superamphiphilic. The activities of MC3T3-E1 cells suggested that the proliferation trend on the micro/nanostructured surfaces was greatly influenced by different crystalline phases, and the highest proliferation rate was obtained on the anatase/rutile surface, followed by the anatase; but the cell differentiation and extracellular matrix mineralization were almost the same among them. After ultrathin HA modification on the micro/nanostructured surfaces with different crystalline phases, it exhibited similar proliferation trend as the original surfaces; however, the cell differentiation and extracellular matrix mineralization were significantly improved. The results indicate that the introduction of ultrathin HA to the micro/nanostructured surfaces with optimized crystalline phase benefits cell proliferation, differentiation and maturation, which suggests a favorable biomimetic microenvironment and provides the potential for enhanced implant osseointegration in vivo.

Mechanisms by which electroacupuncture‑mediated histone acetylation mitigates bone loss in rats with ovariectomy‑induced osteoporosis

The aim of the present study was to investigate the effectiveness of electroacupuncture (EA) on ovariectomy-induced osteoporotic rats to elucidate potential mechanisms by which EA regulates acetylation of histones in caput femoris. A total of 40 female Sprague-Dawley rats were randomly allocated into four groups: Sham operation, ovariectomy-induced osteoporosis (OVX), EA and 17β-estradiol (E2) treatments. After 8 weeks of intervention, the trabecular morphology of each group was measured by micro-computed tomography. Biomarkers of bone metabolism in serum were detected. The protein expression of histone deacetylase 2 (HDAC2), histone H3, Ac-histone H3 and downstream cytokines involved in osteoblast and osteoclast differentiation were detected. The results showed that EA and E2 both prevented bone loss and improved trabecular morphology in OVX rats. EA was found to suppress the protein expression of HDAC2 and promoted the acetylation of histone H3 compared with the OVX model group. The results indicated that EA promoted the differentiation of osteoblasts, and suppressed that of osteoclasts, thereby improving the trabecular morphology. E2 was shown to regulate the expression of runt-related transcription factor 2 and receptor activator of nuclear factor-κB ligand without modulating the expression of HDAC2, and therefore diverged mechanistically from EA. Overall, the results of the present study suggested that the mechanisms through which EA improved bone mineral density and trabecular morphology may involve the modulation of histone H3 acetylation and regulation of osteoblast and osteoclast differentiation.