Demineralized bone matrix scaffold modified with mRNA derived from osteogenically pre-differentiated MSCs improves bone repair

Multi-scale cellular PLA-based bionic scaffold to promote bone regrowth and repair

Large bone defects have presented a significant challenge in orthopedic treatments, and the emergence of tissue-engineered scaffolds has introduced new avenues for treatment. Nonetheless, the clinical application of such scaffolds has been hindered by drawbacks like inadequate mechanical properties, and deficient osteogenesis. Herein, a biocompatible polylactic acid (PLA) based composite was proposed to emulate cancellous bone's morphology by incorporating nano-hydroxyapatite (nHA). In addition, a quantity of Mg²⁺ and chitosan (CS) as active osteogenic factors were adopted to imitate the bone marrow mesenchymal components in vivo. Using a pre-evaporated solvent and sacrificial multi-template techniques, the cellular PLA-based tissue engineering scaffolds containing macropores larger than 100 μm and micropores smaller than 10 μm were developed. The scaffold's bionic structure, osteogenic active component, and multi-scale cellular make it comparable to cancellous bone, with favorable mechanical properties and hydrophilicity. Vitro tests using Sprague-Dawley (SD) rat bone marrow mesenchymal stem cells (rBMSCs) demonstrated the scaffold's excellent biocompatibility to induce high efficiency of osteogenic differentiation. The bionic porous scaffold with multi-scale cellular structure also can recruit rBMSCs, promote bone regrowth and osteogenic differentiation, and facilitate the regeneration of defective bone tissue for repair. This contribution presented a promising strategy for future advancements in bone tissue engineering.

Evaluation of Biocompatibility of New Osteoplastic Xenomaterials Containing Zoledronic Acid and Strontium Ranelate

Background. The problem of improving the functional characteristics of implanted devices and materials used in traumatology and orthopedics is a topical issue. Aim of the study to study biocompatibility of bovine bone matrix xenomaterials modified by zoledronic acid and strontium ranelate when implanted into the bone defect cavity. Methods. The study was performed on 24 male rabbits of the Soviet Chinchilla breed. Test blocks of bone matrix were implanted into the cavity of bone defects of the femur. Group 1 animals (n = 8, control group) were implanted with bone xenogenic material (Bio-Ost osteoplastic matrix). Group 2 animals (n = 8) were implanted with bone xenogenic material impregnated with zoledronic acid. Group 3 animals (n = 8) were implanted with bone xenogeneic material impregnated with strontium ranelate. Supercritical fluid extraction technology was used to purify the material and impregnate it with zoledronic acid and strontium ranelate. Radiological, pathomorphological, histological and laboratory (hematology and blood biochemistry) diagnostic methods were used to assess biocompatibility. Follow-up period was 182 days after implantation. Results. It was found out that on the 182nd day after implantation the median area of the newly-formed bone tissue in the defect modeling area in Group 1 was 79%, in Group 2 0%, in Group 3 67%. In Group 2 the maximum area by this period was filled with connective tissue 77%. Median relative area of implanted material fragments in Group 1 was 4%, in Group 2 23%, in Group 3 15%. No infection or material rejection was observed in animals of all groups. There were no signs of intoxication or prolonged systemic inflammatory reaction. Laboratory parameters did not change significantly over time. One animal in each group experienced one-time increase in C-reactive protein level against the background of leukocytosis. Two animals in Group 1 had a slight migration of implanted material under the skin, one animal developed arthritis of the knee joint. Conclusion. Osteoplastic materials based on bovine bone xenomatrix and filled with zoledronic acid and strontium ranelate have acceptable values of biocompatibility including their safety profile.

Comparison of a Thiolated Demineralized Bone Matrix Hydrogel to a Clinical Product Control for Regeneration of Large Sheep Cranial Defects

Regeneration of calvarial bone remains a major challenge in the clinic as available options do not sufficiently regenerate bone in larger defect sizes. Calvarial bone regeneration cases involving secondary medical conditions, such as brain herniation during traumatic brain injury (TBI) treatment, further exacerbate treatment options. Hydrogels are well-positioned for severe TBI treatment, given their innate flexibility and potential for bone regeneration to treat TBI in a single-stage surgery. The current study evaluated a photocrosslinking pentenoate-modified hyaluronic acid polymer with thiolated demineralized bone matrix (i.e., TDBM hydrogel) capable of forming a completely interconnected hydrogel matrix for calvarial bone regeneration. The TDBM hydrogel demonstrated a setting time of 120 s, working time of 3 to 7 days, negligible change in setting temperature, physiological setting pH, and negligible cytotoxicity, illustrating suitable performance for in vivo application. Side-by-side ovine calvarial bone defects (19 mm diameter) were employed to compare the TDBM hydrogel to the standard-of-care control material DBX®. After 16 weeks, the TDBM hydrogel had comparable healing to DBX® as demonstrated by mechanical push-out testing (~800 N) and histology. Although DBX® had 59% greater new bone volume compared to the TDBM hydrogel via micro-computed tomography, both demonstrated minimal bone regeneration overall (15 to 25% of defect volume). The current work presents a method for comparing the regenerative potential of new materials to clinical products using a side-by-side cranial bone defect model. Comparison of novel biomaterials to a clinical product control (i.e., standard-of-care) provides an important baseline for successful regeneration and potential for clinical translation.

Matrices Activated with Messenger RNA

Over two decades of preclinical and clinical experience have confirmed that gene therapy-activated matrices are potent tools for sustained gene modulation at the implantation area. Matrices activated with messenger RNA (mRNA) are the latest development in the area, and they promise an ideal combination of efficiency and safety. Indeed, implanted mRNA-activated matrices allow a sustained delivery of mRNA and the continuous production of therapeutic proteins in situ. In addition, they are particularly interesting to generate proteins acting on intracellular targets, as the translated protein can directly exert its therapeutic function. Still, mRNA-activated matrices are incipient technologies with a limited number of published records, and much is still to be understood before their successful implementation. Indeed, the design parameters of mRNA-activated matrices are crucial for their performance, as they affect mRNA stability, device immunogenicity, translation efficiency, and the duration of the therapy. Critical design factors include matrix composition and its mesh size, mRNA chemical modification and sequence, and the characteristics of the nanocarriers used for mRNA delivery. This review aims to provide some background relevant to these technologies and to summarize both the design space for mRNA-activated matrices and the current knowledge regarding their pharmaceutical performance. Furthermore, we will discuss potential applications of mRNA-activated matrices, mainly focusing on tissue engineering and immunomodulation.

Recent advances in gene therapy for bone tissue engineering

Autografting, a major treatment for bone fractures, has potential risks related to the required surgery and disease transmission. Bone morphogenetic proteins (BMPs) are the most common osteogenic factors used for bone-healing applications. However, BMP delivery can have shortcomings such as a short half-life and the high cost of manufacturing the recombinant proteins. Gene delivery methods have demonstrated promising alternative strategies for producing BMPs or other osteogenic factors using engineered cells. These approaches can also enable temporal overexpression and local production of the therapeutic genes in the target tissues. This review addresses recent progress on engineered viral, non-viral, and RNA-mediated gene delivery systems that are being used for bone repair and regeneration. Advances in clustered regularly interspaced short palindromic repeats/Cas9 genome engineering for bone tissue regeneration also is discussed.

A cell-free difunctional demineralized bone matrix scaffold enhances the recruitment and osteogenesis of mesenchymal stem cells by promoting inflammation resolution

The dialogue between host macrophages (Mφs) and endogenous mesenchymal stem cells (MSCs) promotes M2 Mφs polarization to resolve early-stage inflammation, thereby effectively guiding in situ bone regeneration. Once inflammation is unresolved/incontrollable, it will induce the impediment of MSCs homing at bone defect site, implying the seasonable resolution of inflammation in balancing bone homeostasis. Repeatedly, evidence elucidated that specialized pro-resolving mediators (SPMs) could conduce to proper resolve inflammation and promote the repairing of bone defect. A difunctional demineralized bone matrix (DBM) scaffold co-modified by maresin 1 (MaR1) and aptamer 19S (Apt19S) was fabricated to facilitate the osteogenesis of MSCs. To confirm the osteogenesis and immunomodulatory role of the difunctional DBM scaffold, the proliferation, recruitment, and osteogenic differentiation of MSCs and the Mφs M2 subtype polarization were evaluated in vitro. Then, the DBM scaffolds were implanted into mice model with critical size calvarial defect to evaluate bone repair efficiency. Finally, the specific resolution mechanism in Mφs cultured on the difunctional DBM scaffold was further in-depth investigated. This difunctional DBM scaffold exhibited an enhanced function on the recruitment, proliferation, migration, osteogenesis of MSCs and the resolution of inflammation, finally improved bone-scaffold integration. At the same time, MaR1 modified on the difunctional DBM scaffold increased the biosynthesis of 12-lipoxygenase (12-LOX) and 12S-hydroxy-eicosatetraenoic acid (12S-HETE), and also directly stimulated lipid droplets (LDs) biogenesis in Mφs, which suggested that MaR1 regulated Mφ lipid metabolism at bone repair site. Findings based on this synergy strategy demonstrated that Mφ lipid metabolism was essential in bone homeostasis, which might provide a theoretical direction for the treatment-associated application of MaR1 in inflammatory bone disease.

A brief review of mRNA therapeutics and delivery for bone tissue engineering

The therapeutics for bone tissue regeneration requires constant advancements owing to the steady increase in the number of patients suffering from bone-related disorders, and also to find efficient and cost-effective treatment modalities. One of the major advancements in the field of therapeutics is the development of mRNAs. mRNAs, which have been extensively tested for the vaccines, could be very well utilized as a potential inducer for bone regeneration. The ability of mRNAs to enter the cells and instruct the cellular machinery to produce the required native proteins such as BMP or VEGF is a great way to avoid the issues faced with growth factor deliveries such as the production cost, loss of biological function etc. However, there have been a few hurdles for using mRNAs as an effective therapeutic agent, such as proper dosing, tolerating the degradation by RNases, improving the half-life, controlling the spatio-temporal release and reducing the off-target effects. This brief review discusses the various developments in the field of mRNA therapeutics especially for bone tissue engineering, how nano-formulations are being developed to effectively deliver the mRNAs into the cells by evading the immune responses, how researchers have developed certain strategies to increase the half-life, to successfully deliver the mRNAs to specific bone defect area and bring about effective bone regeneration.

Electrically controlled mRNA delivery using a polypyrrole-graphene oxide hybrid film to promote osteogenic differentiation of human mesenchymal stem cells

Direct messenger ribonucleic acid (mRNA) delivery to target cells or tissues has revolutionized the field of biotechnology. However, the applicability of regenerative medicine is limited by the technical difficulties of various mRNA-loaded nanocarriers. Herein, we report a new conductive hybrid film that could guide osteogenic differentiation of human adipose-derived mesenchymal stem cells (hADMSCs) via electrically controlled mRNA delivery. To find optimal electrical conductivity and mRNA-loading capacity, the polypyrrole-graphene oxide (PPy-GO) hybrid film was electropolymerized on indium tin oxide substrates. We found that the fluorescein sodium salt, a molecule partially mimicking the physical and chemical properties of mRNAs, can be effectively absorbed and released by electrical stimulation (ES). The hADMSCs cultivated on the PPy-GO hybrid film loaded with pre-osteogenic mRNAs showed the highest osteogenic differentiation under electrical stimulation. This platform can load various types of RNAs thus highly promising as a new nucleic acid delivery tool for the development of stem cell-based therapeutics.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (electrochemical and FT-IR analysis on the film, additional SEM, AFM and C-AFM images of the film, optical and fluorescence images of cells, and the primers used for RT-qPCR analysis) is available in the online version of this article at 10.1007/s12274-022-4613-y.

Demineralized and decellularized bone extracellular matrix-incorporated electrospun nanofibrous scaffold for bone regeneration

Extracellular matrix (ECM)-based materials have been employed as scaffolds for bone tissue engineering, providing a suitable microenvironment with biophysical and biochemical cues for cell attachment, proliferation and differentiation. In this study, bone-derived ECM (bECM)-incorporated electrospun poly(ε-caprolactone) (PCL) (bECM/PCL) nanofibrous scaffolds were prepared and their effects on osteogenesis were evaluated in vitro and in vivo. The results showed that the bECM/PCL scaffolds promoted the attachment, spreading, proliferation and osteogenic differentiation of rat mesenchymal stem cells (MSCs), mitigated the foreign-body reaction, and facilitated bone regeneration in a rat calvarial critical size defect model. Thus, this study suggests that bECM can provide a promising option for bone regeneration.