Enhanced osseointegration of three-dimensional supramolecular bioactive interface through osteoporotic microenvironment regulation

Novel Nanohydroxyapatite (nHAp)-Based Scaffold Doped with Iron Oxide Nanoparticles (IO), Functionalized with Small Non-Coding RNA (miR-21/124) Modulates Expression of Runt-Related Transcriptional Factor 2 and Osteopontin, Promoting Regeneration of Osteoporotic Bone in Bilateral Cranial Defects in a Senescence-Accelerated Mouse Model (SAM/P6). PART 2

Purpose

Healing of osteoporotic defects is challenging and requires innovative approaches to elicit molecular mechanisms promoting osteoblasts-osteoclasts coupling and bone homeostasis.

Methods

Cytocompatibility and biocompatibility of previously characterised nanocomposites, i.e Ca₅(PO₄)₃OH/Fe₃O₄ (later called nHAp/IO) functionalised with microRNAs (nHAp/IO@miR-21/124) was tested. In vitro studies were performed using a direct co-culture system of MC3T3-E1 pre-osteoblast and 4B12 pre-osteoclasts. The analysis included determination of nanocomposite influence on cultures morphology (confocal imaging), viability and metabolic activity (Alamar Blue assay). Pro-osteogenic signals were identified at mRNA, miRNA and protein level with RT-qPCR, Western blotting and immunocytochemistry. Biocompatibility of biomaterials was tested using bilateral cranial defect performed on a senescence-accelerated mouse model, ie SAM/P6 and Balb/c. The effect of biomaterial on the process of bone healing was monitored using microcomputed tomography.

Results

The nanocomposites promoted survival and metabolism of bone cells, as well as enhanced functional differentiation of pre-osteoblasts MC3T3-E1 in co-cultures with pre-osteoclasts. Differentiation of MC3T3-E1 driven by nHAp/IO@miR-21/124 nanocomposite was manifested by improved extracellular matrix differentiation and up-regulation of pro-osteogenic transcripts, ie late osteogenesis markers. The nanocomposite triggered bone healing in a cranial defect model in SAM/P6 mice and was replaced by functional bone in Balb/c mice.

Conclusion

This study demonstrates that the novel nanocomposite nHAp/IO can serve as a platform for therapeutic miRNA delivery. Obtained nanocomposite elicit pro-osteogenic signals, decreasing osteoclasts differentiation, simultaneously improving osteoblasts metabolism and their transition toward pre-osteocytes and bone mineralisation. The proposed scaffold can be an effective interface for in situ regeneration of osteoporotic bone, especially in elderly patients.

3D printing of dual-cell delivery titanium alloy scaffolds for improving osseointegration through enhancing angiogenesis and osteogenesis

BACKGROUND

The repair of large bone defects is a great challenge for orthopedics. Although the development of three-dimensional (3D) printed titanium alloy (Ti6Al4V) implants with optimized the pore structure have effectively promoted the osseointegration. However, due to the biological inertia of Ti6Al4Vsurface and the neglect of angiogenesis, some patients still suffer from postoperative complications such as dislocation or loosening of the prosthesis.

METHODS

The purpose of this study was to construct 3D printed porous Ti6Al4V scaffolds filled with bone marrow mesenchymal stem cells (BMSC) and endothelial progenitor cells (EPC) loaded hydrogel and evaluate the efficacy of this composite implants on osteogenesis and angiogenesis, thus promoting osseointegration.

RESULTS

The porosity and pore size of prepared 3D printed porous Ti6Al4V scaffolds were 69.2 ± 0.9 % and 593.4 ± 16.9 μm, respectively, which parameters were beneficial to bone ingrowth and blood vessel formation. The BMSC and EPC filled into the pores of the scaffolds after being encapsulated by hydrogels can maintain high viability. As a cell containing composite implant, BMSC and EPC loaded hydrogel incorporated into 3D printed porous Ti6Al4V scaffolds enhancing osteogenesis and angiogenesis to repair bone defects efficiently. At the transcriptional level, the composite implant up-regulated the expression levels of the osteogenesis-related genes alkaline phosphatase (ALP) and osteocalcin (OCN), and angiogenesis-related genes hypoxia-inducible factor 1 alpha (HIF-1α), and vascular endothelial growth factor (VEGF).

CONCLUSIONS

Overall, the strategy of loading porous Ti6Al4V scaffolds to incorporate cells is a promising treatment for improving osseointegration.

Extracorporeal Shock Wave Combined with Teriparatide-Loaded Hydrogel Injection Promotes Segmental Bone Defects Healing in Osteoporosis

BACKGROUND

Osteoporosis is a systemic bone disease characterized by decreased bone density and deterioration of bone microstructure, leading to an increased probability of fragility fractures. Once segmental bone defect occurs, it is easy to cause delayed union and nonunion.

METHODS

The aim of this study is to investigate the efficacy of extracorporeal shock wave (ESW) and teriparatide-loaded hydrogel (T-Gel) combined strategy on the cell activity and differentiation of osteoporosis derived bone marrow mesenchymal stem cells (OP-BMSCs) in vitro and bone regeneration in osteoporotic segmental bone defects in vivo.

RESULTS

In vitro, the strategy of combining ESW and T-Gel significantly enhanced OP-BMSCs proliferation, survival, migration, and osteogenic differentiation by up-regulating the alkaline phosphatase activity, mineralization, and expression of runt-related transcription factor-2, type I collagen, osteocalcin, and osteopontin. In the segmental bone defect models of osteoporotic rabbits, Micro-CT evaluation and histological observation demonstrated this ESW-combined with T-Gel injection significantly induced bone healing by enhancing the osteogenic activity of the local microenvironment in osteoporotic defects.

CONCLUSION

In conclusion, ESW-combined with T-Gel injection could regulate the poor osteogenic microenvironment in osteoporotic defects and show potential for enhancing fragility fractures healing.

Additively manufactured titanium scaffolds and osteointegration - meta-analyses and moderator-analyses of in vivo biomechanical testing

Introduction

Maximizing osteointegration potential of three-dimensionally-printed porous titanium (3DPPT) is an ongoing focus in biomaterial research. Many strategies are proposed and tested but there is no weighted comparison of results.

Methods

We systematically searched Pubmed and Embase to obtain two pools of 3DPPT studies that performed mechanical implant-removal testing in animal models and whose characteristics were sufficiently similar to compare the outcomes in meta-analyses (MAs). We expanded these MAs to multivariable meta-regressions (moderator analysis) to verify whether statistical models including reported scaffold features (e.g., “pore-size”, “porosity”, “type of unit cell”) or post-printing treatments (e.g., surface treatments, adding agents) could explain the observed differences in treatment effects (expressed as shear strength of bone-titanium interface).

Results

“Animal type” (species of animal in which the 3DPPT was implanted) and “type of post-treatment” (treatment performed after 3D printing) were moderators providing statistically significant models for differences in mechanical removal strength. An interaction model with covariables “pore-size” and “porosity” in a rabbit subgroup analysis (the most reported animal model) was also significant. Impact of other moderators (including “time” and “location of implant”) was not statistically significant.

Discussion/conclusion

Our findings suggest a stronger effect from porosity in a rat than in a sheep model. Additionally, adding a calcium-containing layer does not improve removal strength but the other post-treatments do. Our results provide overview and new insights, but little narrowing of existing value ranges. Consequent reporting of 3DPPT characteristics, standardized comparison, and expression of porosity in terms of surface roughness could help tackle these existing dilemmas.

Graphical abstract

Printing New Bones: From Print-and-Implant Devices to Bioprinted Bone Organ Precursors

Regenerating large bone defects remains a significant clinical challenge, motivating increased interest in additive manufacturing and 3D bioprinting to engineer superior bone graft substitutes. 3D bioprinting enables different biomaterials, cell types, and growth factors to be combined to develop patient-specific implants capable of directing functional bone regeneration. Current approaches to bioprinting such implants fall into one of two categories, each with their own advantages and limitations. First are those that can be 3D bioprinted and then directly implanted into the body and second those that require further in vitro culture after bioprinting to engineer more mature tissues prior to implantation. This review covers the key concepts, challenges, and applications of both strategies to regenerate damaged and diseased bone.

Simvastatin-Incorporated Drug Delivery Systems for Bone Regeneration

Local drug delivery systems composed of biomaterials and osteogenic substances provide promising strategies for the reconstruction of large bone defects. In recent years, simvastatin has been studied extensively for its pleiotropic effects other than lowering of cholesterol, including its ability to induce osteogenesis and angiogenesis. Accordingly, several studies of simvastatin incorporated drug delivery systems have been performed to demonstrate the feasibility of such systems in enhancing bone regeneration. Therefore, this review explores the molecular mechanisms by which simvastatin affects bone metabolism and angiogenesis. The simvastatin concentrations that promote osteogenic differentiation are analyzed. Furthermore, we summarize and discuss a variety of simvastatin-loaded drug delivery systems that use different loading methods and materials. Finally, current shortcomings of and future development directions for simvastatin-loaded drug delivery systems are summarized. This review provides various advanced design strategies for simvastatin-incorporated drug delivery systems that can enhance bone regeneration.

3D‑printed Ti6Al4V scaffolds combined with pulse electromagnetic fields enhance osseointegration in osteoporosis

The loosening and displacement of prostheses after dental implantation and arthroplasty is a substantial medical burden due to the complex correction surgery. Three-dimensional (3D)-printed porous titanium (pTi) alloy scaffolds are characterized by low stiffness, are beneficial to bone ingrowth, and may be used in orthopedic applications. However, for the bio-inert nature between host bone and implants, titanium alloy remains poorly compatible with osseointegration, especially in disease conditions, such as osteoporosis. In the present study, 3D-printed pTi scaffolds with ideal pore size and porosity matching the bone tissue, were combined with pulse electromagnetic fields (PEMF), an exogenous osteogenic induction stimulation, to evaluate osseointegration in osteoporosis. In vitro, external PEMF significantly improved osteoporosis-derived bone marrow mesenchymal stem cell proliferation and osteogenic differentiation on the surface of pTi scaffolds by enhancing the expression of alkaline phosphatase, runt-related transcription factor-2, osteocalcin, and bone morphogenetic protein-2. In vivo, Microcomputed tomography analysis and histological evaluation indicated the external PEMF markedly enhanced bone regeneration and osseointegration. This novel therapeutic strategy has potential to promote osseointegration of dental implants or artificial prostheses for patients with osteoporosis.

Intra-articular Injection of Chitosan-Based Supramolecular Hydrogel for Osteoarthritis Treatment

BACKGROUND

Pain and cartilage destruction caused by osteoarthritis (OA) is a major challenge in clinical treatment. Traditional intra-articular injection of hyaluronic acid (HA) can relieve the disease, but limited by the difficulty of long-term maintenance of efficacy.

METHODS

In this study, an injectable and self-healing hydrogel was synthesized by in situ crosslinking of N-carboxyethyl chitosan (N-chitosan), adipic acid dihydrazide (ADH), and hyaluronic acid-aldehyde (HA-ALD).

RESULTS

This supramolecular hydrogel sustains good biocompatibility for chondrocytes. Intra-articular injection of this novel hydrogel can significantly alleviate the local inflammation microenvironment in knee joints, through inhibiting the inflammatory cytokines (such as TNF-α, IL-1β, IL-6 and IL-17) in the synovial fluid and cartilage at 2- and even 12-weeks post-injection. Histological and behavioral test indicated that hydrogel injection protected cartilage destruction and relieved pain in OA rats, in comparison to HA injection.

CONCLUSION

This kind of novel hydrogel, which is superior to the traditional HA injection, reveals a great potential for the treatment of OA.

Synergistic anti-inflammatory and osteogenic n-HA/resveratrol/chitosan composite microspheres for osteoporotic bone regeneration

The development of functional materials for osteoporosis is ultimately required for bone remodeling. However, grafts were accompanied by increasing pro-inflammatory cytokines that impaired bone formation. In this work, nano-hydroxyapatite (n-HA)/resveratrol (Res)/chitosan (CS) composite microspheres were designed to create a beneficial microenvironment and help improve the osteogenesis by local sustained release of Res. Study of in vitro release confirmed the feasibility of n-HA/Res/CS microspheres for controlled Res release. Notably, microspheres had anti-inflammatory activity evidenced by the decreased expression of pro-inflammatory cytokines TNF-α, IL-1β and iNOS in RAW264.7 cells in a dose dependent manner. Further, enhanced adhesion and proliferation of BMSCs seeded onto microspheres demonstrated that composite microspheres were conducive to cell growth. The ability to enhance osteo-differentiation was supported by up-regulation of Runx2, ALP, Col-1 and OCN, and substantial mineralization in osteogenic medium. When implanted into bone defects in the osteoporotic rat femoral condyles, enhanced entochondrostosis and bone regeneration suggested that the n-HA/Res/CS composite microspheres were more favorable for impaired fracture healing. The results indicated that optimized n-HA/Res/CS composite microspheres could serve as promising multifunctional fillers for osteoporotic bone defect/fracture treatment.

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The microspheres with sustained Res release possessed obvious anti-inflammatory activity.

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The microspheres were favorable for cell growth and osteo-differentiation.

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Higher Res-loaded microspheres significantly improved entochondrostosis and bone remodeling.

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The microspheres are promising bone fillers for the healing of osteoporotic bone defects/fractures.

In Vitro and In Vivo Biocompatibility Studies of a Cast and Coated Titanium Alloy

The biocompatibility of a cast porous and with a calcium titanate reaction layer functionalized titanium alloy (Ti-6Al-7Nb) was tested by means of cell culture, and a small (rat) and large animal (sheep) model. The uncoated titanium material served as a control. In-vitro tests included the validation of osteoblast-like cells attached to the surface of the material with scanning electron microscopy and immunofluorescence of cytoskeletal actin as well as their osteogenic development, the ability to mineralize, and their vitality. Following the in-vitro tests a small animal (rat) and big animal (sheep) model were accomplished by inserting a cylindrical titanium implant into a drill hole defect in the femoral condyle. After 7, 14, and 30 days (rat) and 6 months (sheep) the condyles were studied regarding histological and histomorphometrical characteristics. Uncoated and coated material showed a good biocompatibility both in cell culture and animal models. While the defect area in the rat is well consolidated after 30 days, the sheep show only little bone inside the implant after 6 months, possibly due to stress shielding. None of the executed methods indicated a statistically significant difference between coated and uncoated material.

Synergistic Fabrication of Dose-Response Chitosan/Dextran/β-Glycerophosphate Injectable Hydrogel as Cell Delivery Carrier for Cardiac Healing After Acute Myocardial Infarction

The human mesenchymal stem cells (hMSCs) therapy offering an encouraging the new methods to establish the conveying on the chitosan (C)/dextran (D)/β-glycerophosphate (β-GP) loaded with hMSCs to enhance the acute myocardial infarctions. The synthesized hMSCs-CD@β-GP system displayed the ratio of determination modules, size of the pore, absorbency, and the swellings ratio in the assortment of the 65 ka, 149 ± 39.8 µm, 92.2%, 42 ± 1.38, and 29 ± 1.9, respectively. The fabricated hMSCs-CD@β-GP was highly stable and physicochemical investigated and confirmed the suitability of the materials for cardiac regeneration applications. The in vitro examinations of the injectable hydrogels with hMSCs-CD@β-GP have recognized that the improved survival rate of the cells, increased the pro-inflammatory expressions factors, pro-angiogenic factors analysis confirmed the promising results of the ejection of fractions, fibrosis area, vessel density with decreased infractions size, with suggesting that the remarkable improvement of the heart regenerative function after myocardial infarctions. The new synergistic approach of the injectable hydrogels with hMSCs could able appropriate for the effective treatment of cardiac therapies after acute myocardial infarctions.

Regulation of inflammatory microenvironment using a self-healing hydrogel loaded with BM-MSCs for advanced wound healing in rat diabetic foot ulcers

A diabetic foot ulcer (DFUs) is a state of prolonged chronic inflammation, which can result in amputation. Different from normal skin wounds, various commercially available dressings have not sufficiently improved the healing of DFUs. In this study, a novel self-healing hydrogel was prepared by in situ crosslinking of N-carboxyethyl chitosan (N-chitosan) and adipic acid dihydrazide (ADH) with hyaluronic acid-aldehyde (HA-ALD), to provide a moist and inflammatory relief environment to promote stem cell proliferation or secretion of growth factors, thus accelerating wound healing. The results demonstrated that this injectable and self-healing hydrogel has excellent swelling properties, stability, and mechanical properties. This biocompatible hydrogel stimulated secretion of growth factors from bone marrow mesenchymal stem cells (BM-MSCs) and regulated the inflammatory environment by inhibiting the expression of M1 macrophages and promoting the expression of M2 macrophages, resulting in granulation tissue formation, collagen deposition, nucleated cell proliferation, neovascularization, and enhanced diabetic wound healing. This study showed that N-chitosan/HA-ALD hydrogel could be used as a multifunctional injectable wound dressing to regulate chronic inflammation and provide an optimal environment for BM-MSCs to promote diabetic wound healing.

The combination of multi-functional ingredients-loaded hydrogels and three-dimensional printed porous titanium alloys for infective bone defect treatment

Biomaterial with the dual-functions of bone regeneration and antibacterial is a novel therapy for infective bone defects. Three-dimensional (3D)-printed porous titanium (pTi) benefits bone ingrowth, but its microporous structure conducive to bacteria reproduction. Herein, a multifunctional hydrogel was prepared from dynamic supramolecular assembly of sodium tetraborate (Na2B4O7), polyvinyl alcohol (PVA), silver nanoparticles (AgNPs) and tetraethyl orthosilicate (TEOS), and composited with pTi as an implant system. The pTi scaffolds have ideal pore size and porosity matching with bone, while the supramolecular hydrogel endows pTi scaffolds with antibacterial and biological activity. In vitro assessments indicated the 3D composite implant was biocompatible, promoted bone marrow mesenchymal stem cells (BMSCs) proliferation and osteogenic differentiation, and inhibited bacteria, simultaneously. In vivo experiments further demonstrated that the implant showed effective antibacterial ability while promoting bone regeneration. Besides distal femur defect, the innovative scaffolds may also serve as an ideal biomaterial (e.g. dental implants) for other contaminated defects.