A potential function for MicroRNA-124 in normal and pathological bone conditions.

Cells produce short single-stranded non-coding RNAs (ncRNAs) called microRNAs (miRNAs), which actively regulate gene expression at the posttranscriptional level. Several miRNAs have been observed to exert significant impacts on bone health and bone-related disorders. One of these, miR-124, is observed in bone microenvironments and is conserved across species. It affects bone cell growth and differentiation by activating different transcription factors and signaling pathways. In-depth functional analyses of miR-124 have revealed several physiological and pathological roles exerted through interactions with other ncRNAs. Deciphering these RNA-mediated signaling networks and pathways is essential for understanding the potential impacts of dysregulated miRNA functions on bone biology. In this review, we aim to provide a comprehensive analysis of miR-124's involvement in bone physiology and pathology. We highlight the importance of miR-124 in controlling transcription factors and signaling pathways that promote bone growth. This review reveals therapeutic implications for the treatment of bone-related diseases.

Regulatory and therapeutic implications of competing endogenous RNA network in breast cancer progression and metastasis: A review.

Breast cancer (BC) is a global health concern, and development of diagnostic tools and targeted treatments for BC remains challenging. Therapeutic approaches for BC often involve a combination of surgery, radiation therapy, chemotherapy, targeted therapy, and hormone therapy. In recent years, there has been a growing interest in the role of noncoding RNAs (ncRNAs), including long ncRNAs (lncRNAs) and microRNAs (miRNAs), in BC and their therapeutic implications. Various biological processes such as cell proliferation, migration, and apoptosis rely on the activities of these ncRNAs, and their dysregulation has been implicated in BC progression. The regulatory function of the competitive endogenous RNA (ceRNA) network, which comprises lncRNAs, miRNAs, and mRNAs, has been the subject of extensive pathophysiological research. Most lncRNAs serve as molecular sponges for miRNAs and sequester their activities, thereby regulating the expression of target mRNAs and contributing to the promotion or inhibition of BC progression. This review summarizes recent findings on the role of ceRNA networks in BC progression, metastasis, and therapeutic resistance, and highlights the association of ceRNA networks with transcription factors and signaling pathways. Understanding the ceRNA network can lead to the discovery of biomarkers and targeted treatment methods to prevent the spread and metastasis of BC.

In vivo validation of the functional role of MicroRNA-4638-3p in breast cancer bone metastasis.

PURPOSE: Skeletal metastases are increasingly reported in metastatic triple-negative breast cancer (BC) patients. We previously reported that TGF-ß1 sustains activating transcription factor 3(ATF3) expression and is required for cell proliferation, invasion, and bone metastasis genes. Increasing studies suggest the critical regulatory function of microRNAs (miRNAs) in governing BC pathogenesis. TGF-ß1 downregulated the expression of miR-4638-3p, which targets ATF3 in human BC cells (MDA-MB-231). In the present study, we aimed to identify the functional role of miR-4638-3p in BC bone metastasis by the caudal artery injection of the MDA-MB-231 cells overexpressing mir-4638 in the mice. METHODS: MDA-MB-231 cells overexpressing miR-4638 were prepared by stable transfections. Reverse transcriptase quantitative PCR was carried out to determine the expression of endogenous miR-4638-3p and bone resorption marker genes. X-ray, micro-CT, and Hematoxylin & Eosin studies were used to determine osteolytic lesions, trabecular structure, bone mineral density, and micrometastasis of cells. RESULTS: The mice injected with MDA-MB-231 cells overexpressing miR-4638-3p decreased the expression of bone resorption marker genes, compared to MDA-MB-231 cells injection. Reduced osteolytic lesions and restored bone density by MDA-MB-231 cells overexpressing miR-4638-3p were observed. Similarly, the mice injected with MDA-MB-231 cells overexpressing miR-4638-3p showed a better microarchitecture of the trabecular network. A few abnormal cells seen in the femur of MDA-MB-231 cells-injected mice were not found in MDA-MB-231 cells overexpressing miR-4638. CONCLUSION: The identified functional role of ATF3 targeting miR-4638-3p in BC bone metastasis in vivo suggests its candidature as BC therapeutics in the future.

Chitosan nanocarriers for non-coding RNA therapeutics: A review.

Non-coding RNA (ncRNA)-based therapies entail delivering ncRNAs to cells to regulate gene expression and produce proteins that combat infections, cancer, neurological diseases, and bone abnormalities. Nevertheless, the therapeutic potential of these ncRNAs has been limited due to the difficulties in delivering them to specific cellular targets within the body. Chitosan (CS), a biocompatible cationic polymer, interacts with negatively charged RNA molecules to form stable complexes. It is a promising biomaterial to develop nanocarriers for ncRNA delivery, overcoming several disadvantages of traditional delivery systems. CS-based nanocarriers can protect ncRNAs from degradation and target-specific delivery by surface modifications and intracellular release profiles over an extended period. This review briefly summarizes the recent developments in CS nanocarriers' synthesis and design considerations and their applications in ncRNA therapeutics for treating various diseases. We also discuss the challenges and limitations of CS-based nanocarriers for ncRNA therapeutics and potential strategies for overcoming these challenges.

MicroRNAs mediated interaction of tumor microenvironment cells with breast cancer cells during bone metastasis.

Breast cancer (BC) bone metastasis is primarily osteolytic and has limited therapeutic options. Metastasized BC cells prime the secondary environment in bone by forming a tumor niche, which favors their homing and colonization. The tumor microenvironment (TME) is primarily generated by the cancer cells. Bone TME is an intricate network of multiple cells, including altered bone, tumor, stromal, and immune cells. Recent findings highlight the significance of small non-coding microRNAs (miRNAs) in influencing TME during tumor metastasis. MiRNAs from TME-resident cells facilitate the interaction between the tumor and its microenvironment, thereby regulating the biological processes of tumors. These miRNAs can serve as oncogenes or tumor suppressors. Hence, both miRNA inhibitors and mimics are extensively utilized in pre-clinical trials for modulating the phenotypes of tumor cells and associated stromal cells. This review briefly summarizes the recent developments on the functional role of miRNAs secreted directly or indirectly from the TME-resident cells in facilitating tumor growth, progression, and metastasis. This information would be beneficial in developing novel targeted therapies for BC.

Chitosan-coated and thymol-loaded polymeric semi-interpenetrating hydrogels: An effective platform for bioactive molecule delivery and bone regeneration in vivo.

Thymol (2-isopropyl-5-methylphenol; Thy) is a monoterpene phenolic phytocompound with medicinal properties; however, its impact on osteogenesis is yet to be thoroughly investigated. Its distribution is often hampered because of its intricate hydrophobic structure, which reduces its bioavailability. In this study, we synthesized a drug delivery vehicle using semi-interpenetrating polymer network (SIPN) hydrogels containing sodium alginate and poly(2-ethyl-2-oxazoline) (SA/Pox) loaded with Thy at varying concentrations (100, 150, and 200 µM). Subsequently, they were coated with chitosan (CS) to increase bioactivity and for sustained and prolonged release of Thy. Thy-loaded CS-coated SIPN hydrogels (SA/Pox/CS-Thy) were developed using ionic gelation and polyelectrolyte-complexation techniques. The addition of CS to hydrogels enhanced their physicochemical and material properties. These hydrogels were cytofriendly toward mouse mesenchymal stem cells (mMSCs). When mMSCs were cultured on hydrogels, Thy stimulated osteoblastic differentiation, as evidenced by calcium deposits at the cellular level. The expression of RUNX2, a key bone transcriptional factor, and other differentiation biomarkers was significantly enhanced in mMSCs cultured on SA/Pox/CS-Thy hydrogels. Notably, Thy in the SA/Pox/CS hydrogels significantly activated the TGF-ß/BMP signaling pathway, which is involved in osteogenesis. A rat tibial bone defect model system revealed that the incorporation of Thy into SA/Pox/CS hydrogels augmented bone regeneration. Thus, sustained and prolonged release of Thy from the SA/Pox/CS hydrogels promoted osteoblast differentiation in vitro and bone formation in vivo. These findings shed light on the effect of Thy bioavailability in fostering osteoblast differentiation and its prospective application in bone rejuvenation.

Circ_CUX1/miR-130b-5p/p300 axis for parathyroid hormone-stimulation of Runx2 activity in rat osteoblasts: A combined bioinformatic and experimental approach.

Parathyroid hormone (PTH) regulates the expression of bone remodeling genes by enhancing the activity of Runx2 in osteoblasts. p300, a histone acetyltransferase, acetylated Runx2 to activate the expression of its target genes. PTH stimulated the expression of p300 in rat osteoblastic cells. Increasing studies suggested the potential of non-coding RNAs (ncRNAs), such as microRNAs (miRNAs) and circular RNAs (circRNAs), in regulating gene expression under both physiological and pathological conditions. In this study, we hypothesized that PTH regulates Runx2 activity via ncRNAs-mediated p300 expression in rat osteoblastic cells. Bioinformatics and experimental approaches identified PTH-upregulation of miR-130b-5p and circ_CUX1 that putatively target p300 and miR-130b-5p, respectively. An antisense-mediated knockdown of circ_CUX1 was performed to determine the sponging activity of circ_CUX1. Knockdown of circ_CUX1 promoted miR-130b-5p activity and reduced p300 expression, resulting in decreased Runx2 acetylation in rat osteoblastic cells. Further, bioinformatics analysis identified the possible signaling pathways that regulate Runx2 activity and osteoblast differentiation via circ_CUX1/miR-130b-5p/p300 axis. The predicted circ_CUX1/miR-130b-5p/p300 axis might pave the way for better diagnostic and therapeutic approaches for bone-related diseases.

Regulation of Wnt signaling by non-coding RNAs during osteoblast differentiation.

Bone is a rigid, mineralized connective tissue that constitutes part of the skeleton in most vertebrate animals. Bone remodeling is a complex process that involves the coordination of ossification and bone resorption activities by osteoblasts and osteoclasts, respectively, resulting in maintaining bone mass. This process involves several growth factors/cytokines and hormones regulating the various signaling pathways. Wnt is one of the major molecular signaling pathways that positively regulate the osteogenic differentiation of mesenchymal stem cells. Dysregulation in the Wnt signaling leads to serious bone-related disorders like osteoporosis and osteosclerosis. Recently, several studies reported the critical role of non-coding RNAs (ncRNAs), including microRNAs, long ncRNAs, and circular RNAs, in the regulation of bone homeostasis via modulating the Wnt signaling cascade. This review summarizes the importance of such ncRNAs in mediating the Wnt cascade and its effect on osteoblast differentiation. Understanding the regulatory role of these ncRNAs would serve as a novel therapeutic strategy for treating bone-related disorders.

MiR-4638-3p regulates transforming growth factor-ß1-induced activating transcription factor-3 and cell proliferation, invasion, and apoptosis in human breast cancer cells.

TGF-ß1 (transforming growth factor-beta1), a secreted polypeptide cytokine, stimulates ATF-3 (activating transcription factor-3) expression in a sustained and prolonged manner in human breast cancer cells (MDA-MB231), but not in normal human mammary epithelial cells (MCF-10A). Cyclin A (cell proliferation gene), Runx2 (metastasis gene), and MMP-13 (matrix metalloproteinase-13; invasive gene) were identified as ATF-3 target genes in these cells. Because ATF-3 has very few druggable sites, its direct targeting is difficult. Recent evidence has indicated that microRNAs (miRNAs) are key players in the post-transcriptional modulation of gene expression under several conditions. Bioinformatic analysis suggested a list of putative miRNAs that target ATF-3. Therefore, we hypothesized that TGF-ß1 downregulates the miRNAs that target ATF-3, resulting in the activation of genes that participate in breast cancer progression and skeletal metastasis. Our findings indicate that TGF-ß1 downregulated the expression of miR-4638-3p in MDA-MB231 cells. At the molecular level, forced expression of miR-4638-3p reduced the expression of ATF-3 and its downstream targets, Runx2 and MMP-13, in these cells. At the cellular level, overexpression of miR-4638-3p reduced proliferation, invasion, and migration, and induced G0/G1 cell cycle arrest and apoptosis in MDA-MB231 cells. Overall, this study highlights the possibility of utilizing miR-4638-3p as a therapeutic molecule to curb skeletal metastasis of breast cancer cells.

Chitosan-based scaffolds as drug delivery systems in bone tissue engineering.

The bone tissue engineering approach for treating large bone defects becomes necessary when the tissue damage surpasses the threshold of the inherent regenerative ability of the human body. A myriad of natural biodegradable polymers and scaffold fabrication techniques have emerged in the last decade. Chitosan (CS) is especially attractive as a bone scaffold material to support cell attachment and proliferation and mineralization of the bone matrix. The primary amino groups in CS are responsible for properties such as controlled drug release, mucoadhesion, in situ gelation, and transfection. CS-based smart drug delivery scaffolds that respond to environmental stimuli have been reported to have a localized sustained delivery of drugs in the large bone defect area. This review outlines the recent advances in the fabrication of CS-based scaffolds as a pharmaceutical carrier to deliver drugs such as antibiotics, growth factors, nucleic acids, and phenolic compounds for bone tissue regeneration.

Exosomes in bone remodeling and breast cancer bone metastasis.

Exosomes are endosome-derived microvesicles that carry cell-specific biological cargo, such as proteins, lipids, and noncoding RNAs (ncRNAs). They play a key role in bone remodeling by enabling the maintenance of a balance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption. Recent evidence indicates that exosomes disrupt bone remodeling that occurs during breast cancer (BC) progression. The bone is a preferred site for BC metastasis owing to its abundant osseous reserves. In this review, we aimed to highlight the roles of exosomes derived from bone cells and breast tumor in bone remodeling and BC bone metastasis (BCBM). We also briefly outline the mechanisms of action of ncRNAs and proteins carried by exosomes secreted by bone and BCBM. Furthermore, this review highlights the potential of utilizing exosomes as biomarkers or delivery vehicles for the diagnosis and treatment of BCBM.

Orsellinic acid-loaded chitosan nanoparticles in gelatin/nanohydroxyapatite scaffolds for bone formation in vitro.

AIM: Orsellinic acid (2,4-Dimethoxy-6-methylbenzoic acid) (OA) is a hydrophobic polyphenolic compound with therapeutic potential, but its impact on actuating osteogenesis remains unknown. The bioavailability of OA is hampered by its hydrophobic nature. This study aimed to fabricate nano-drug delivery system-based scaffolds for OA and test its potential for osteogenesis in vitro. MATERIALS AND METHODS: OA was loaded into chitosan nanoparticles (nCS + OA) using the ionic gelation technique at different concentrations. nCS + OA were incorporated onto the scaffolds containing gelatin (Gel) and nanohydroxyapatite (nHAp) by the lyophilization method. Biocomposite scaffolds were examined for their physicochemical and material characteristic properties. The effect of OA in the scaffolds for osteoblast differentiation was determined by alizarin red and von Kossa staining at the cellular level and by reverse transcriptase-qPCR and western blot analysis at the molecular level. KEY FINDINGS: The scaffolds showed excellent physiochemical and material characteristics and remained cyto-friendly to mouse mesenchymal stem cells (mMSCs, C3H10T1/2). The release of OA from Gel/nHAp/nCS scaffolds enhanced the differentiation of mMSCs towards osteoblasts, as observed through cellular and molecular studies. Moreover, the osteogenic potential of OA was mediated by the activation of FAK and ERK signaling pathways through integrins. SIGNIFICANCE: The inclusion of OA into Gel/nHAp/nCS biocomposite scaffolds at 80 µM concentration promoted osteoblast differentiation via cell adhesion mediated signaling, compared with that shown by Gel/nHAp/nCS alone. Overall, this study identified the potential therapeutic OA containing Gel/nHAp/nCS scaffolds, accelerating its potential for clinical application towards bone regeneration.

Role of p300, a histone acetyltransferase enzyme, in osteoblast differentiation.

Bone is a dynamic and tough connective tissue that undergoes constant remodeling throughout life. Bone-forming osteoblasts respond to various hormones, cytokines, and growth factors, and synthesize extracellular matrix components. Runx2 (Runt-related transcription factor 2), a bone transcription factor, is essential for ossification by stimulating the expression of osteoblast differentiation marker genes, including type I collagen, alkaline phosphatase, and osteocalcin. Coactivators, such as p300, CBP (CREB-binding protein), and PCAF (p300/CBP associated factor) tightly regulate osteoblast differentiation via Runx2. There is growing evidence indicating the role of p300, which possesses histone acetyltransferase (HAT) activity, in regulating histones and transcription factors such as Runx2 during osteoblast differentiation. In this review, we aim to delineate the role of p300 at the molecular level, emphasizing the importance of its HAT activity during osteoblast differentiation. Furthermore, this review intends to highlight the regulation of p300 at multiple levels, including post-translational and ncRNAs, that might exert an indirect influence on bone formation.

Preparation and characterization of chitosan/carboxymethyl pullulan/bioglass composite films for wound healing.

Wound dressings play a vital role in the wound healing process. Although a variety of wound dressings have been developed so far, most of them still have many drawbacks such as rigidity, non-porosity, low mechanical strength, an affinity to stick onto the injury surface and less antimicrobial activity. To overcome these issues, a novel type of porous three-dimensional (3D) film was fabricated using chitosan/carboxymethyl pullulan polyelectrolyte complex (PEC) loaded with 45S5 bioglass (CCMPBG) by the freeze-drying method for wound healing application. The developed films were analysed by FTIR, XRD, EDS and SEM to confirm their chemical nature, microstructure and surface morphologies. The CCMPBG films exhibited rough surface morphology and well-interconnected micropores with an average size range of 101-74 µm. Compared to the control chitosan/carboxymethyl pullulan (CCMP) film, the CCMPBG films showed an enhanced mechanical strength and controlled rate of swelling and biodegradation behaviours due to the interaction of polymer matrix and 45S5 bioglass (BG). Furthermore, CCMPBG films presented the improved biocompatibility, antimicrobial activity and wound closure ability because of the synergistic effects of chitosan, carboxymethyl pullulan (CMP) and BG. The results demonstrated that CCMPBG films can be an effective dressing material for wound therapy.

Parathyroid Hormone-regulation of Runx2 by MiR-290 for Matrix Metalloproteinase-13 Expression in Rat Osteoblastic Cells.

BACKGROUND: The dynamic changes that bone undergoes during the ensemble of remodeling are administered by vital factors like Runx2 (a bone transcription factor) and matrix metalloproteinases (MMPs). AIMS: Parathyroid hormone (PTH), an FDA approved drug for bone-related ailments, was seen to stimulate MMP-13 expression via Runx2 to ultimately aid in the bone remodeling process. MicroRNAs (miRNAs) have been shown to play a major role in controlling bone metabolism, and the use of miRNAs has recently become promising therapeutic avenues for the treatment of many diseases, including bone disorders. Thus, in this study, we attempted to investigate and evaluate the expression of MMP-13 via a miRNA profile targeting Runx2 under PTH-regulation in rat osteoblastic cells. METHODS: PTH stimulated the expression of MMP-13 mRNA significantly at 4 h in rat osteoblastic cells (UMR106-01). Runx2 was required for PTH-stimulation of MMP-13 expression, in silico scrutiny generated 14 unique miRNAs targeting Runx2, and among these miRNAs, miR-290 was significantly downregulated by PTH-treatment in UMR106- 01 cells and in rat primary osteoblasts. RESULTS: Overexpression of miR-290 decreased the expression of Runx2, the binding of Runx2 at the MMP-13 promoter, and the expression of MMP-13 mRNA in PTH-treated UMR106-01 cells. A dual luciferase reporter assay identified the direct targeting of Runx2 mRNA by miR-290 in these cells. CONCLUSION: Our findings indicate that the PTH-responsive miR-290 regulated Runx2- mediated MMP-13 expression in rat osteoblastic cells, suggesting miR-290 as a molecular marker or target in bone and bone-related diseases.

A regulatory role of circRNA-miRNA-mRNA network in osteoblast differentiation.

Osteoblast differentiation is an important process in skeletal development and bone remodelling. Serious bone diseases occur from any delay, defect, or imbalance in osteoblastic differentiation. Non-coding RNAs (ncRNAs) play a regulatory role in controlling the expression of proteins under physiological and pathological conditions via inhibiting mRNA translation or degrading mRNA. Circular RNAs (circRNAs) and microRNAs (miRNAs) are the long and small ncRNAs, respectively, which have been reported to regulate the expression of osteoblast marker genes directly or indirectly. Also, recent studies identified the regulatory mechanisms involving the crosstalk among circRNAs, miRNAs, and mRNAs during osteoblast differentiation. Understanding these regulatory mechanisms behind osteoblastic differentiation would help to diagnose or treat bone and bone-related disorders. Hence, the current review comprehensively discussed the regulatory relationship of circRNAs, miRNAs and mRNAs, and their functional role as circRNA-miRNA-mRNA axis in osteoblast differentiation.

Epigenetic modifications of histones during osteoblast differentiation.

In bone biology, epigenetics plays a key role in mesenchymal stem cells' (MSCs) commitment towards osteoblasts. It involves gene regulatory mechanisms governed by chromatin modulators. Predominant epigenetic mechanisms for efficient osteogenic differentiation include DNA methylation, histone modifications, and non-coding RNAs. Among these mechanisms, histone modifications critically contribute to altering chromatin configuration. Histone based epigenetic mechanisms are an essential mediator of gene expression during osteoblast differentiation as it directs the bivalency of the genome. Investigating the importance of histone modifications in osteogenesis may lead to the development of epigenetic-based remedies for genetic disorders of bone. Hence, in this review, we have highlighted the importance of epigenetic modifications such as post-translational modifications of histones, including methylation, acetylation, phosphorylation, ubiquitination, and their role in the activation or suppression of gene expression during osteoblast differentiation. Further, we have emphasized the future advancements in the field of epigenetics towards orthopaedical therapeutics.

TGF-ß1-stimulation of NFATC2 and ATF3 proteins and their interaction for matrix metalloproteinase 13 expression in human breast cancer cells.

Activating transcription factor 3 (ATF3), an inducible stress gene, is stimulated by transforming growth factor-beta1 (TGF-ß1) in a protracted and relentless manner in human mammary cancer cells (hBC cells; MDA-MB231). The molecular mechanism behind this stable expression of ATF3 via TGF-ß1 in MDA-MB231 cells is unknown. This study found that TGF-ß1 stimulated the expression of the nuclear factor of activated T Cells 2 (NFATC2) in MDA-MB231 cells and provided evidence of its interaction with ATF3. The functional characterization of NFATC2 in association with ATF3 was determined by silencing of NFATC2 using siRNA. Knock-down of NFATC2 decreased the expression of both ATF3 and its target gene MMP13 (matrix metalloproteinase 13, a critical invasive gene) in hBC cells. Chromatin immunoprecipitation revealed that TGF-ß1 promoted NFATC2 binding and NFATC2-ATF3 complex binding at the MMP13 promoter region, whereas silencing of NFATC2 decreased their binding in hBC cells. Thus, we uncovered the mechanism of interaction between NFATC2 and ATF3 regulated by TGF-ß1, and NFATC2 acted as a pivotal factor in providing ATF3 stability and further drove MMP13 transcription. Targeting NFATC2 and blocking its association with ATF3 could therefore help to slow the progression of breast cancer.

A computational approach on studying the regulation of TGF-ß1-stimulated Runx2 expression by MicroRNAs in human breast cancer cells.

BACKGROUND: Transforming growth factor-beta1 (TGF-ß1) acts as a most effective growth inhibitor for normal epithelial cells. Loss of this anti-proliferative factor in breast tissues favors invasion and development of osteolytic metastases, aided by a master transcription factor, runt-related transcription factor 2 (Runx2). Several reports identified Runx2 regulation with the help of non-coding RNAs such as microRNAs (miRNAs) under physiological and pathological conditions. METHODS: Using bioinformatics tools such as miRDB, STarMir, Venny, TarBase, a unique list of miRNAs that putatively target the 3' UTR Runx2 was identified. Further, the expression patterns of those miRNAs at the precursor and mature levels were studied by RT-qPCR analyses. Following this, computational analyses using software like TransmiR and bc-GenExMiner v4.6 were done to speculate the miRNA's other target genes that indirectly regulate Runx2 activity in breast cancer. RESULTS: There were 13 miRNAs that putatively target Runx2 identified using bioinformatics tools. Among these miRNAs, miR-5703 expression was significantly downregulated at both precursor and mature levels upon TGF-ß1-treatment in human breast cancer cells. Computational analyses speculated an indirect targeting of Runx2 by miR-5703 by influencing multiple Runx2 regulatory signaling pathways including Jak/Stat, MAPK, Wnt/ß-Catenin, Notch, BMP, and PKA pathways. Furthermore, a correlation of the expression profiles of the speculated genes and Runx2 with miR-5703 was depicted in triple-negative breast cancer patients. CONCLUSION: Identification of miR-5703 and its network for Runx2 regulation directly or indirectly in breast cancer cells could significantly advance our understanding of breast cancer-mediated bone metastasis. In addition, it would potentially pave the way for miRNAs to be used as biomarkers and therapeutic agents in cancer research.

Chitosan-based 3D-printed scaffolds for bone tissue engineering.

Despite the spontaneous regenerative properties of autologous bone grafts, this technique remains dilatory and restricted to fractures and injuries. Conventional grafting strategies used to treat bone tissue damage have several limitations. This highlights the need for novel approaches to overcome the persisting challenges. Tissue-like constructs that can mimic natural bone structurally and functionally represent a promising strategy. Bone tissue engineering (BTE) is an approach used to develop bioengineered bone with subtle architecture. BTE utilizes biomaterials to accommodate cells and deliver signaling molecules required for bone rejuvenation. Among the various techniques available for scaffold creation, 3D-printing technology is considered to be a superior technique as it enables the design of functional scaffolds with well-defined customizable properties. Among the biomaterials obtained from natural, synthetic, or ceramic origins, naturally derived chitosan (CS) polymers are promising candidates for fabricating reliable tissue constructs. In this review, the physicochemical-biological properties and applications of CS-based 3D-printed scaffolds and their future perspectives in BTE are summarized.