Enhanced proliferation and differentiation effects of a CGRP- and Sr-enriched calcium phosphate cement on bone mesenchymal stem cells

ATF2-driven osteogenic activity of enoxaparin sodium-loaded polymethylmethacrylate bone cement in femoral defect regeneration

BACKGROUND

Polymethylmethacrylate (PMMA) bone cement loaded with enoxaparin sodium (PMMA@ES) has been increasingly highlighted to affect the bone repair of bone defects, but the molecular mechanisms remain unclear. We addressed this issue by identifying possible molecular mechanisms of PMMA@ES involved in femoral defect regeneration based on bioinformatics analysis and network pharmacology analysis.

METHODS

The upregulated genes affecting the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) were selected through bioinformatics analysis, followed by intersection with the genes of ES-induced differentiation of BMSCs identified by network pharmacology analysis. PMMA@ES was constructed. Rat primary BMSCs were isolated and cultured in vitro in the proliferation medium (PM) and osteogenic medium (OM) to measure alkaline phosphatase (ALP) activity, mineralization of the extracellular matrix, and the expression of RUNX2 and OCN using gain- or loss-of-function experiments. A rat femoral bone defect model was constructed to detect the new bone formation in rats.

RESULTS

ATF2 may be a key gene in differentiating BMSCs into osteoblasts. In vitro cell assays showed that PMMA@ES promoted the osteogenic differentiation of BMSCs by increasing ALP activity, extracellular matrix mineralization, and RUNX2 and OCN expression in PM and OM. In addition, ATF2 activated the transcription of miR-335-5p to target ERK1/2 and downregulate the expression of ERK1/2. PMMA@ES induced femoral defect regeneration and the repair of femoral defects in rats by regulating the ATF2/miR-335-5p/ERK1/2 axis.

CONCLUSION

The evidence provided by our study highlighted the ATF2-mediated mechanism of PMMA@ES in the facilitation of the osteogenic differentiation of BMSCs and femoral defect regeneration.

Facile Fabrication of 3D-Printed Porous Ti6Al4V Scaffolds with a Sr-CaP Coating for Bone Regeneration

To improve osseointegration caused by the stress-shielding effect and the inert nature of titanium-based alloys, in this work, we successfully constructed a strontium calcium phosphate (Sr-CaP) coating on three-dimensional (3D)-printed Ti6Al4V scaffolds to address this issue. The energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) results indicated that the coatings with and without Sr doping mainly consisted of CaHPO₄. The bonding strength of Sr doping coating met the required ISO 13 779-4-2018 standard (≥15 MPa). The in vitro results suggested that the Sr-CaP-modified Ti6Al4V scaffolds were found to effectively promote mice bone-marrow stem cell (mBMSC) adhesion, spreading, and osteogenesis. The in vivo experiments also showed that the Sr-CaP-modified Ti6Al4V scaffolds could significantly improve bone regeneration and osseointegration. More importantly, Sr-doped CaP-coated Ti6Al4V scaffolds were found to accelerate bone healing in comparison to CaP-coated Ti6Al4V scaffolds. The Sr-CaP-modified Ti6Al4V scaffolds are considered a promising strategy to develop bioactive surfaces for enhancing the osseointegration between the implant and bone tissue.

Myokine Irisin promotes osteogenesis by activating BMP/SMAD signaling via αV integrin and regulates bone mass in mice

Irisin is well-known to contribute to bone homeostasis due to its bidirectional regulation on osteogenesis and osteoclastogenesis. However, the mechanisms of irisin involved in mesenchymal stem/stromal cells (MSCs)-derived osteogenesis are still under investigated. Fibronectin type III domain-containing protein 5 (FNDC5) is the precursor protein of irisin, compare with wild type (WT) littermates, FNDC5^-/- mice lost bone mass significantly, collectively evidenced by the decrease of bone mineral density (BMD), impaired bone formation and reduced N-terminal propertied of type I procollagen (P1NP) in sera. Meanwhile, the bone resorbing of FNDC5^-/- mice has enhanced accompanied by increased tartrate phosphatase (TRAP) staining cells morphologically and cross-Linked C-telopeptide of type 1 collagen (CTX) level in sera. In vitro study showed that lack of irisin impeded the MSC-derived osteogenesis of FNDC5^-/- mice. The addition of irisin promote the osteogenesis of WT and irisin-deficient MSCs, by activating αV integrin-induced ERK/STAT pathway, subsequently enhancing bone morphogenetic protein 2 (BMP2) expression and BMP/SMAD signaling activation. Taken together, these findings further indicate that irisin regulates bone homeostasis. Moreover, irisin promotes MSC-derived osteogenesis by binding to αV integrin and activating BMP/SMAD signaling consequently. Thus, irisin may be a promising therapeutic target for osteoporosis and bone defects.

Exploring the effect of the "quaternary regulation" theory of "peripheral nerve-angiogenesis-osteoclast-osteogenesis" on osteoporosis based on neuropeptides

Osteoporosis is a common bone metabolic disease among the middle-aged and elderly, with its high incidence rate and a major cause of disability and mortality. Early studies found that bone metabolic homeostasis is achieved through osteogenesis-osteoclast coupling. Although current anti-osteoporosis drugs can attenuate bone loss caused by aging, they present specific side effects. With the discovery of CD31^hi Emcn^hi blood vessels in 2014, the effect of H-type blood vessels on bone metabolism has been valued by researchers, and the ternary regulation theory of bone metabolism of "Angiogenesis-Osteoclast-Osteogenesis" has also been recognized. Nowadays, more studies have confirmed that peripheral nerves substantially impact bone metabolism. However, due to the complex function of peripheral nerves, the crosstalk mechanism of "Peripheral nerve-Angiogenesis-Osteoclast-Osteogenesis" has not yet been fully revealed. Neuropeptide serves as signaling molecules secreted by peripheral nerves that regulate blood vessels, osteoblasts, and osteoclasts' functions. It is likely to be the breakthrough point of the quaternary regulation theory of "Peripheral nerve-Angiogenesis-Osteoclast-Osteogenesis". Here, we discuss the effect of peripheral nerves on osteoporosis based on neuropeptides.

A Review on the Enhancement of Calcium Phosphate Cement with Biological Materials in Bone Defect Healing

Calcium phosphate cement (CPC) is a promising material used in the treatment of bone defects due to its profitable features of self-setting capability, osteoconductivity, injectability, mouldability, and biocompatibility. However, the major limitations of CPC, such as the brittleness, lack of osteogenic property, and poor washout resistance, remain to be resolved. Thus, significant research effort has been committed to modify and reinforce CPC. The mixture of CPC with various biological materials, defined as the materials produced by living organisms, have been fabricated by researchers and their characteristics have been investigated in vitro and in vivo. This present review aimed to provide a comprehensive overview enabling the readers to compare the physical, mechanical, and biological properties of CPC upon the incorporation of different biological materials. By mixing the bone-related transcription factors, proteins, and/or polysaccharides with CPC, researchers have demonstrated that these combinations not only resolved the lack of mechanical strength and osteogenic effects of CPC but also further improve its own functional properties. However, exceptions were seen in CPC incorporated with certain proteins (such as elastin-like polypeptide and calcitonin gene-related peptide) as well as blood components. In conclusion, the addition of biological materials potentially improves CPC features, which vary depending on the types of materials embedded into it. The significant enhancement of CPC seen in vitro and in vivo requires further verification in human trials for its clinical application.

Calcitonin gene‑related peptide regulates FOSL2 expression and cell proliferation of BMSCs via mmu_circRNA_003795

Circular RNAs (circRNAs) are a class of non-coding RNAs that may have important regulatory potency in various biological processes. However, the role of circRNAs and their potential functions in bone marrow mesenchymal stem cells of mice (BMSCs) are still ambiguous. The current study aims to examine the expression of circRNAs and to investigate their effects on FOS like 2 AP-1 transcription factor subunit (FOSL2) expression following stimulation of BMSCs with calcitonin gene-related peptide (CGRP). RNA generated from BMSCs stimulated with or without CGRP was used in a microarray to detect expression of circRNAs. There were 58 significantly differentially expressed circRNAs following CGRP treatment, with 44 circRNAs downregulated and 14 upregulated. Bioinformatics analysis and regulatory networks were used to identify the potential interactions between circRNAs and microRNAs (miRs). mmu_circRNA_003795 was significantly increased in the CGRP-stimulated BMSCs compared with the blank control. Silencing of mmu_circRNA_003795, significantly increased the expression of mmu_miR-504-3p, whereas FOSL2 expression and cell proliferation were decreased. Furthermore, silencing of mmu_mir-504-3p using an miR inhibitor led to increased FOSL2 expression. Additionally, silencing of mmu_circRNA_003795 using small interfering RNA induced marked alterations in the cell cycle of BMSCs. The results demonstrated that mmu_circRNA_003795 can indirectly regulate FOSL2 expression via sponging of miR-504-3p, resulting in alterations in BMSC proliferation.

A unique heterologous fibrin sealant (HFS) as a candidate biological scaffold for mesenchymal stem cells in osteoporotic rats

Background

The injection of mesenchymal stem cells (MSCs) directly into the bone of osteoporotic (OP) patients for rapid recovery has been studied worldwide. Scaffolds associated with MSCs are used to maintain and avoid cell loss after application. A unique heterologous fibrin sealant (HFS) derived from snake venom was evaluated for the cytotoxicity of its main components and as a three-dimensional biological scaffold for MSCs to repair a critical femur defect in osteoporotic rats.

Methods

The cytotoxicity of HFS was assessed using a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazoliumbromide (MTT) assay and transmission electron microscopy. The cells were cultured, characterized by flow cytometry and differentiated into the osteogenic lineage. Two-month-old rats underwent ovariectomy to induce OP. After 3 months, a 5 mm critical bone defect was made in the distal end of the rat femurs and filled with HFS; HFS + MSCs; and HFS + MSCs D (differentiated into the osteogenic lineage) to evaluate the effects. An injury control group (injury and no treatment) and blank control group (no injury and no treatment) were also included. The animals were observed at days 14 and 28 by microtomographic (micro-CT) analyses, histologic and biochemical analysis, as well as scanning electron microscopy.

Results

The results revealed that one of the compounds of HFS, the thrombin-like enzyme extracted from snake venom, had no cytotoxic effects on the MSCs. OP was successfully induced, as demonstrated by the significant differences in the levels of 17β-estradiol, Micro-CT analyses and alkaline phosphatase between the ovariectomized (OVX) and non-ovariectomized (NOVX) groups. The histological data revealed that at 14 days after surgery in both the OVX and NOVX animals, the HFS + CTMs and HFS + CTMsD showed a higher formation of bone cells at the site in relation to the control group (without treatment). Collagen formation was evidenced through bone neoformation in all treated and control groups. No morphological differences in the femurs of the NOVX and OVX animals were observed after the surgical procedure. Scanning electron microscopy (SEM) confirmed the histological analysis.

Conclusions

The new HFS composed of two non-toxic components for MSCs showed capacity to promote the recovery of the bone lesions in OVX and NOVX animals at 14 days after surgery. In addition, the HFS enabled the differentiation of MSCs into MSCs D in the group treated with HFS + MSCs. Using the MSCs and/or MSCs D together with this biopharmaceutical could potentially enable significant advances in the treatment of osteoporotic fractures. Future clinical trials will be necessary to confirm these results.