Promoted Angiogenesis and Osteogenesis by Dexamethasone-loaded Calcium Phosphate Nanoparticles/Collagen Composite Scaffolds with Microgroove Networks

Tissue scaffolds mimicking hierarchical bone morphology as biomaterials for oral maxillofacial surgery with augmentation: structure, properties, and performance evaluation forin vitrotesting

In this study, tissue scaffolds mimicking hierarchical morphology are constructed and proposed for bone augmentation. The scaffolds are fabricated using lyophilization, before coating them with collagen (Col). Subsequently, the Col-coated scaffolds undergo a second lyophilization, followed by silk fibroin (SF) coating, and a third lyophilization. Thereafter, the scaffolds are divided into six groups with varying ratios of Col to SF: Col/SF = 7:3, 5:5, 3:7, 10:0, and 0:10, with an SF scaffold serving as the control group. The scaffold morphology is examined using a scanning electron microscope, while molecular and structural formations are characterized by Fourier transform infrared spectrometer and differential scanning calorimeter, respectively. Physical and mechanical properties including swelling and compression are tested. Biological functions are assessed throughin vitroosteoblast cell culturing. Biomarkers indicative of bone formation-cell viability and proliferation, alkaline phosphatase activity, and calcium content-are analyzed. Results demonstrate that scaffolds coated with Col and SF exhibit sub-porous formations within the main pore. The molecular formation reveals interactions between the hydrophilic groups of Col and SF. The scaffold structure contains bound water and SF formation gets disrupted by Col. Physical and mechanical properties are influenced by the Col/SF ratio and morphology due to coating. The biological functions of scaffolds with Col and SF coating show enhanced potential for promoting bone tissue formation, particularly the Col/SF (7:3) ratio, which is most suitable for bone augmentation in small defect areas.

Dexamethasone Long-Term Controlled Release from Injectable Dual-Network Hydrogels with Porous Microspheres Immunomodulation Promotes Bone Regeneration

Long-lasting, controlled-release, and minimally invasive injectable platforms that provide a stable blood concentration to promote bone regeneration are less well developed. Using hexagonal mesoporous silica (HMS) loaded with dexamethasone (DEX) and poly(lactic-co-glycolic acid) (PLGA), we prepared porous DEX/HMS/PLGA microspheres (PDHP). In contrast to HMS/PLGA microspheres (HP), porous HMS/PLGA microspheres (PHP), DEX/PLGA microspheres (DP), and DEX/HMS/PLGA microspheres (DHP), PDHP showed notable immuno-coordinated osteogenic capabilities and were best at promoting bone mesenchymal stem cell proliferation and osteogenic differentiation. PDHP were combined with methacrylated silk (SilMA) and sodium alginate (SA) to form an injectable photocurable dual-network hydrogel platform that could continuously release the drug for more than 4 months. By adjusting the content of the microspheres in the hydrogel, a zero-order release hydrogel platform was obtained in vitro for 48 days. When the microsphere content was 1%, the hydrogel platform exhibited the best biocompatibility and osteogenic effects. The expression levels of the osteogenic gene alkaline phosphatases, BMP-2 and OPN were 10 to 15 times higher in the 1% group than in the 0% group, respectively. In addition, the 1% microsphere hydrogel strongly stimulated macrophage polarization to the M2 phenotype, establishing an immunological milieu that supports bone regrowth. The aforementioned outcomes were also observed in vivo. The most successful method for correcting cranial bone abnormalities in SD rats was to use a hydrogel called SilMA/SA containing 1% drug-loaded porous microspheres (PDHP/SS). The angiogenic and osteogenic effects of this treatment were also noticeably greater in the PDHP/SS group than in the control and blank groups. In addition, PDHP/SS polarized M2 macrophages and suppressed M1 macrophages in vivo, which reduced the local immune-inflammatory response, promoted angiogenesis, and cooperatively aided in situ bone healing. This work highlights the potential application of an advanced hydrogel platform for long-term, on-demand, controlled release for bone tissue engineering.

Research progress of vascularization strategies of tissue-engineered bone

The bone defect caused by fracture, bone tumor, infection, and other causes is not only a problematic point in clinical treatment but also one of the hot issues in current research. The development of bone tissue engineering provides a new way to repair bone defects. Many animal experimental and rising clinical application studies have shown their excellent application prospects. The construction of rapid vascularization of tissue-engineered bone is the main bottleneck and critical factor in repairing bone defects. The rapid establishment of vascular networks early after biomaterial implantation can provide sufficient nutrients and transport metabolites. If the slow formation of the local vascular network results in a lack of blood supply, the osteogenesis process will be delayed or even unable to form new bone. The researchers modified the scaffold material by changing the physical and chemical properties of the scaffold material, loading the growth factor sustained release system, and combining it with trace elements so that it can promote early angiogenesis in the process of induced bone regeneration, which is beneficial to the whole process of bone regeneration. This article reviews the local vascular microenvironment in the process of bone defect repair and the current methods of improving scaffold materials and promoting vascularization.

Novel scaffold platforms for simultaneous induction osteogenesis and angiogenesis in bone tissue engineering: a cutting-edge approach

Despite the recent advances in the development of bone graft substitutes, treatment of critical size bone defects continues to be a significant challenge, especially in the elderly population. A current approach to overcome this challenge involves the creation of bone-mimicking scaffolds that can simultaneously promote osteogenesis and angiogenesis. In this context, incorporating multiple bioactive agents like growth factors, genes, and small molecules into these scaffolds has emerged as a promising strategy. To incorporate such agents, researchers have developed scaffolds incorporating nanoparticles, including nanoparticulate carriers, inorganic nanoparticles, and exosomes. Current paper provides a summary of the latest advancements in using various bioactive agents, drugs, and cells to synergistically promote osteogenesis and angiogenesis in bone-mimetic scaffolds. It also discusses scaffold design properties aimed at maximizing the synergistic effects of osteogenesis and angiogenesis, various innovative fabrication strategies, and ongoing clinical studies.

Kaempferol-loaded bioactive glass-based scaffold for bone tissue engineering: in vitro and in vivo evaluation

Due to the increasing prevalence of bone disorders among people especially in average age, the future of treatments for osseous abnormalities has been illuminated by scaffold-based bone tissue engineering. In this study, in vitro and in vivo properties of 58S bioactive glass-based scaffolds for bone tissue engineering (bare (B.SC), Zein-coated (C.SC), and Zein-coated containing Kaempferol (KC.SC)) were evaluated. This is a follow-up study on our previously published paper, where we synthesized 58S bioactive glass-based scaffolds coated with Kaempferol-loaded Zein biopolymer, and characterized from mostly engineering points of view to find the optimum composition. For this aim, in vitro assessments were done to evaluate the osteogenic capacity and biological features of the scaffolds. In the in vivo section, all types of scaffolds with/without bone marrow-derived stem cells (BMSC) were implanted into rat calvaria bone defects, and potential of bone healing was assessed using imaging, staining, and histomorphometric analyses. It was shown that, Zein-coating covered surface cracks leading to better mechanical properties without negative effect on bioactivity and cell attachment. Also, BMSC differentiation proved that the presence of Kaempferol caused higher calcium deposition, increased alkaline phosphatase activity, bone-specific gene upregulation in vitro. Further, in vivo study confirmed positive effect of BMSC-loaded KC.SC on significant new bone formation resulting in complete bone regeneration. Combining physical properties of coated scaffolds with the osteogenic effect of Kaempferol and BMSCs could represent a new strategy for bone regeneration and provide a more effective approach to repairing critical-sized bone defects.

A Tunable Calcium Phosphate Coating to Drive in vivo Osseointegration of Composite Engineered Tissues

Varying degrees of hydroxyapatite (HA) surface functionalization have been implicated as the primary driver of differential osteogenesis observed in infiltrating cells. The ability to reliably create spatially controlled areas of mineralization in composite engineered tissues is of growing interest in the field, and the use of HA-functionalized biomaterials may provide a robust solution to this challenge. In this study, we successfully fabricated polycaprolactone salt-leached scaffolds with two levels of a biomimetic calcium phosphate coating to examine their effects on MSC osteogenesis. Longer duration coating in simulated body fluid (SBF) led to increased HA crystal nucleation within scaffold interiors as well as more robust HA crystal formation on scaffold surfaces. Ultimately, the increased surface stiffness of scaffolds coated in SBF for 7 days in comparison to scaffolds coated in SBF for 1 day led to more robust osteogenesis of MSCs in vitro without the assistance of osteogenic signaling molecules. This study also demonstrated that the use of SBF-based HA coatings can promote higher levels of osteogenesis in vivo. Finally, when incorporated as the endplate region of a larger tissue-engineered intervertebral disc replacement, HA coating did not induce mineralization in or promote cell migration out of neighboring biomaterials. Overall, these results verified tunable biomimetic HA coatings as a promising biomaterial modification to promote discrete regions of mineralization within composite engineered tissues.

Biofabricating the vascular tree in engineered bone tissue

The development of tissue engineering strategies for treatment of large bone defects has become increasingly relevant, given the growing demand for bone substitutes. Native bone is composed of a dense vascular network necessary for the regulation of bone development, regeneration and homeostasis. A major obstacle in fabricating living, clinically relevant-sized bone mimics (1-10 cm³) is the limited supply of nutrients, including oxygen to the core of the construct. Therefore, strategies to support vascularization are pivotal for the development of tissue engineered bone constructs. Creating a functional bone construct integrated with a vascular network, capable of delivering the necessary nutrients for optimal tissue development is imperative for translation into the clinics. The vascular system is composed of a complex network that runs throughout the body in a tree-like hierarchical branching fashion. A significant challenge for tissue engineering approaches lies in mimicking the intricate, multi-scale structures consisting of larger vessels (macro-vessels) which interconnect with multiple sprouting vessels (microvessels) in a closed network. The advent of biofabrication has enabled complex, out of plane channels to be generated and has laid the groundwork for the creation of multi-scale vasculature in recent years. This review highlights the key state-of-the-art achievements for the development of vascular networks of varying scales in the field of biofabrication with a particular focus for its application in developing a functional tissue engineered bone construct. STATEMENT OF SIGNIFICANCE: There is a growing need for bone substitutes to overcome the limited supply of patient-derived bone. Bone tissue engineering aims to overcome this by combining stem cells with scaffolds to restore missing bone. The current bottleneck in upscaling is the lack of an integrated vascular network, required for the delivery of nutrients to cells. 3D bioprinting techniques has enabled the creation of complex hollow structures of varying dimensions that resemble native blood vessels. The convergence of multiple materials, cell types and fabrication approaches, opens the possibility of developing clinically-relevant sized vascularized bone constructs. This review provides an up-to-date insight of the technologies currently available for the generation of complex vascular networks, with a focus on their application in bone tissue engineering.

Effective treatment of intractable diseases using nanoparticles to interfere with vascular supply and angiogenic process

Angiogenesis is a vital biological process involving blood vessels forming from pre-existing vascular systems. This process contributes to various physiological activities, including embryonic development, hair growth, ovulation, menstruation, and the repair and regeneration of damaged tissue. On the other hand, it is essential in treating a wide range of pathological diseases, such as cardiovascular and ischemic diseases, rheumatoid arthritis, malignancies, ophthalmic and retinal diseases, and other chronic conditions. These diseases and disorders are frequently treated by regulating angiogenesis by utilizing a variety of pro-angiogenic or anti-angiogenic agents or molecules by stimulating or suppressing this complicated process, respectively. Nevertheless, many traditional angiogenic therapy techniques suffer from a lack of ability to achieve the intended therapeutic impact because of various constraints. These disadvantages include limited bioavailability, drug resistance, fast elimination, increased price, nonspecificity, and adverse effects. As a result, it is an excellent time for developing various pro- and anti-angiogenic substances that might circumvent the abovementioned restrictions, followed by their efficient use in treating disorders associated with angiogenesis. In recent years, significant progress has been made in different fields of medicine and biology, including therapeutic angiogenesis. Around the world, a multitude of research groups investigated several inorganic or organic nanoparticles (NPs) that had the potential to effectively modify the angiogenesis processes by either enhancing or suppressing the process. Many studies into the processes behind NP-mediated angiogenesis are well described. In this article, we also cover the application of NPs to encourage tissue vascularization as well as their angiogenic and anti-angiogenic effects in the treatment of several disorders, including bone regeneration, peripheral vascular disease, diabetic retinopathy, ischemic stroke, rheumatoid arthritis, post-ischemic cardiovascular injury, age-related macular degeneration, diabetic retinopathy, gene delivery-based angiogenic therapy, protein delivery-based angiogenic therapy, stem cell angiogenic therapy, and diabetic retinopathy, cancer that may benefit from the behavior of the nanostructures in the vascular system throughout the body. In addition, the accompanying difficulties and potential future applications of NPs in treating angiogenesis-related diseases and antiangiogenic therapies are discussed.

Mesenchymal Stem Cell-Derived Extracellular Vesicles for Bone Defect Repair

The repair of critical bone defects is a hotspot of orthopedic research. With the development of bone tissue engineering (BTE), there is increasing evidence showing that the combined application of extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) (MSC-EVs), especially exosomes, with hydrogels, scaffolds, and other bioactive materials has made great progress, exhibiting a good potential for bone regeneration. Recent studies have found that miRNAs, proteins, and other cargo loaded in EVs are key factors in promoting osteogenesis and angiogenesis. In BTE, the expression profile of the intrinsic cargo of EVs can be changed by modifying the gene expression of MSCs to obtain EVs with enhanced osteogenic activity and ultimately enhance the osteoinductive ability of bone graft materials. However, the current research on MSC-EVs for repairing bone defects is still in its infancy, and the underlying mechanism remains unclear. Therefore, in this review, the effect of bioactive materials such as hydrogels and scaffolds combined with MSC-EVs in repairing bone defects is summarized, and the mechanism of MSC-EVs promoting bone defect repair by delivering active molecules such as internal miRNAs is further elucidated, which provides a theoretical basis and reference for the clinical application of MSC-EVs in repairing bone defects.

Dexamethasone: Insights into Pharmacological Aspects, Therapeutic Mechanisms, and Delivery Systems

Dexamethasone (DEX) has been widely used to treat a variety of diseases, including autoimmune diseases, allergies, ocular disorders, cancer, and, more recently, COVID-19. However, DEX usage is often restricted in the clinic due to its poor water solubility. When administered through a systemic route, it can elicit severe side effects, such as hypertension, peptic ulcers, hyperglycemia, and hydro-electrolytic disorders. There is currently much interest in developing efficient DEX-loaded nanoformulations that ameliorate adverse disease effects inhibiting advancements in scientific research. Various nanoparticles have been developed to selectively deliver drugs without destroying healthy cells or organs in recent years. In the present review, we have summarized some of the most attractive applications of DEX-loaded delivery systems, including liposomes, polymers, hydrogels, nanofibers, silica, calcium phosphate, and hydroxyapatite. This review provides our readers with a broad spectrum of nanomedicine approaches to deliver DEX safely.

Restoration of critical defects in the rabbit mandible using osteoblasts and vascular endothelial cells co-cultured with vascular stent-loaded nano-composite scaffolds

The success of large bone defect repair with tissue engineering technology depends mainly on angiogenesis and osteogenesis. In this study, we prepared poly-caprolactone/nano-hydroxyapatite/beta-calcium phosphate (PCL/nHA/β-TCP) composite scaffolds loaded with poly-(lactic-co-glycolic acid)/nano-hydroxyapatite/collagen/heparin sodium (PLGA/nHA/Col/HS) nanofiber small vascular stent by electrospinning and hot press forming-particle leaching methods. Supramolecular electrostatic self-assembly technology was used to modify the surfaces of small vascular stents to aid in hydrophilicity and anticoagulation. The surfaces of composite scaffolds were modified with an Arg-Gly-Asp (RGD) short peptide by physical adsorption to supply cell adhesion sites. The scaffolds were then combined with rabbit bone marrow-derived osteoblasts (OBs) and rabbit bone marrow-derived vascular endothelial cells (RVECs) to construct large, biologically active vascularized tissue-engineered bone in vitro; this bone was then used to repair critical bone defects in rabbit mandibles. Mechanical and biocompatibility testing results showed that PCL/nHA/β-TCP composite scaffolds loaded with small vascular stents had good surface structure, mechanical properties, biocompatibility, and bone-regeneration induction potential. Twelve weeks after implantation, histological analysis and X-ray scans showed that the use of osteoblasts and vascular endothelial cells co-cultured with PCL/nHA/β-TCP scaffolds was sufficient to repair critical defects in rabbit mandibles.

Biomimetic Supramolecular Drug Delivery Hydrogels for Accelerated Skin Tissue Regeneration

Skin tissue is regenerated by the combinational function of skin cells, extracellular matrix (ECM), and bioactive molecules. As an artificial ECM, supramolecular hydrogels exhibited outstanding capability to mimic the physical properties of ECM. However, the lack of biochemical function in supramolecular hydrogels has limited further tissue engineering applications. Here, we developed self-assembling supramolecular drug delivery hydrogels to mimic the skin tissue regeneration process. The supramolecular hydrogels were prepared to encapsulate fibroblasts by the host-guest interaction of cyclodextrin-modified gelatin (GE-CD) and adamantane-modified hyaluronate (Ad-HA) in conjugation with human growth hormone (hGH) for accelerated skin tissue regeneration. In vitro, GE-CD/Ad-HA-hGH hydrogels showed highly facilitated cell growth by the controlled hGH delivery. After a subcutaneous injection into the back of mice, IVIS imaging of bioengineered fibroblasts to express red fluorescence protein (RFP) revealed prolonged cell survival and proliferation in the supramolecular hydrogels for more than 21 days. We could also observe the improved skin tissue regeneration by the facilitated fibroblast proliferation with angiogenesis. Taken together, we could confirm the feasibility of biomimetic supramolecular drug delivery GE-CD/Ad-HA-hGH hydrogels for various tissue engineering applications.

Control Release of Adenosine Potentiate Osteogenic Differentiation within a Bone Integrative EGCG-g-NOCC/Collagen Composite Scaffold toward Guided Bone Regeneration in a Critical-Sized Calvarial Defect

The regeneration of critical-sized bone defects with biomimetic scaffolds remains clinically challenging due to avascular necrosis, chronic inflammation, and altered osteogenic activity. Two confounding mechanisms, efficacy manipulation, and temporal regulation dictate the scaffold's bone regenerative ability. Equally critical is the priming of the mesenchymal stromal cells (MSCs) toward lineage-specific differentiation into bone-forming osteoblast, which particularly depends on varied mechanochemical and biological cues during bone tissue regeneration. This study sought to design and develop an optimized osteogenic scaffold, adenosine/epigallocatechin gallate-N,O-carboxymethyl chitosan/collagen type I (AD/EGCG-g-NOCC@clgn I), having osteoinductive components toward swift bone regeneration in a calvarial defect BALB/c mice model. The ex vivo findings distinctly establish the pro-osteogenic potential of adenosine and EGCG, stimulating MSCs toward osteoblast differentiation with significantly increased expression of alkaline phosphatase, calcium deposits, and enhanced osteocalcin expression. Moreover, the 3D matrix recapitulates extracellular matrix (ECM) properties, provides a favorable microenvironment, structural support against mechanical stress, and acts as a reservoir for sustained release of osteoinductive molecules for cell differentiation, proliferation, and migration during matrix osteointegration observed. Evidence from in vivo experiments, micro-CT analyses, histology, and histomorphometry signify accelerated osteogenesis both qualitatively and quantitatively: effectual bone union with enhanced bone formation and new ossified tissue in 4 mm sized defects. Our results suggest that the optimized scaffold serves as an adjuvant to guide bone tissue regeneration in critical-sized calvarial defects with promising therapeutic efficacy.

Three dimensional printed nanostructure biomaterials for bone tissue engineering

The suffering from organ dysfunction due to damaged or diseased tissue/bone has been globally on the rise. Current treatment strategies for non-union bone defects include: the use of autografts, allografts, synthetic grafts and free vascularized fibular grafts. Bone tissue engineering has emerged as an alternative for fracture repair to satisfy the current unmet need of bone grafts and to alleviate the problems associated with autografts and allografts. The technology offers the possibility to induce new functional bone regeneration using synergistic combination of functional biomaterials (scaffolds), cells, and growth factors. Bone scaffolds are typically made of porous biodegradable materials that provide the mechanical support during repair and regeneration of damaged or diseased bone. Significant progress has been made towards scaffold materials for structural support, desired osteogenesis and angiogenesis abilities. Thanks for innovative scaffolds fabrication technologies, bioresorbable scaffolds with controlled porosity and tailored properties are possible today. Despite the presence of different bone scaffold fabrication methods, pore size, shape and interconnectivity have not yet been fully controlled in most of the methods. Moreover, scaffolds with tailored porosity for specific defects are still difficult to manufacture. Nevertheless, such scaffolds can be designed and fabricated using three dimensional (3D) printing approaches. 3D printing technology, as an advanced tissue scaffold fabrication method, offers the opportunity to produce complex geometries with distinct advantages. The technology has been used for the production of various types of bodily constructs such as blood vessels, vascular networks, bones, cartilages, exoskeletons, eyeglasses, cell cultures, tissues, organs and novel drug delivery devices. This review focuses on 3D printed scaffolds and their application in bone repair and regeneration. In addition, different classes of biomaterials commonly employed for the fabrication of 3D nano scaffolds for bone tissue engineering application so far are briefly discussed.

The Duo of Osteogenic and Angiogenic Differentiation in ADSC-Derived Spheroids

Bone formation during embryogenesis is driven by interacting osteogenesis and angiogenesis with parallel endothelial differentiation. Thence, all in vitro bioengineering techniques are aimed at pre-vascularization of osteogenic bioequivalents to provide better regeneration outcomes upon transplantation. Due to appearance of cell-cell and cell-matrix interactions, 3D cultures of adipose-derived stromal cells (ADSCs) provide a favorable spatial context for the induction of different morphogenesis processes, including vasculo-, angio-, and osteogenesis and, therefore, allow modeling their communication in vitro. However, simultaneous induction of multidirectional cell differentiation in spheroids from multipotent mesenchymal stromal cells (MMSCs) was not considered earlier. Here we show that arranging ADSCs into spheroids allows rapid and spontaneous acquiring of markers of both osteo- and angiogenesis compared with 2D culture. We further showed that this multidirectional differentiation persists in time, but is not influenced by classical protocols for osteo- or angio-differentiation. At the same time, ADSC-spheroids retain similar morphology and microarchitecture in different culture conditions. These findings can contribute to a better understanding of the fundamental aspects of autonomous regulation of differentiation processes and their cross-talks in artificially created self-organizing multicellular structures. This, in turn, can find a wide range of applications in the field of tissue engineering and regeneration.

Collagen at the maternal-fetal interface in human pregnancy

The survival and development of a semi-allogenic fetus during pregnancy require special immune tolerance microenvironment at the maternal fetal interface. During the establishment of a successful pregnancy, the endometrium undergoes a series of changes, and the extracellular matrix (ECM) breaks down and remodels. Collagen is one of the most abundant ECM. Emerging evidence has shown that collagen and its fragment are expressed at the maternal fetal interface. The regulation of expression of collagen is quite complex, and this process involves a multitude of factors. Collagen exerts a critical role during the successful pregnancy. In addition, the abnormal expressions of collagen and its fragments are associated with certain pathological states associated with pregnancy, including recurrent miscarriage, diabetes mellitus with pregnancy, preeclampsia and so on. In this review, the expression and potential roles of collagen under conditions of physiological and pathological pregnancy are systematically discussed.

NADPH oxidases and HIF1 promote cardiac dysfunction and pulmonary hypertension in response to glucocorticoid excess

Cardiovascular side effects are frequent problems accompanying systemic glucocorticoid therapy, although the underlying mechanisms are not fully resolved. Reactive oxygen species (ROS) have been shown to promote various cardiovascular diseases although the link between glucocorticoid and ROS signaling has been controversial. As the family of NADPH oxidases has been identified as important source of ROS in the cardiovascular system we investigated the role of NADPH oxidases in response to the synthetic glucocorticoid dexamethasone in the cardiovascular system in vitro and in vivo in mice lacking functional NADPH oxidases due to a mutation in the gene coding for the essential NADPH oxidase subunit p22phox. We show that dexamethasone induced NADPH oxidase-dependent ROS generation, leading to vascular proliferation and angiogenesis due to activation of the transcription factor hypoxia-inducible factor-1 (HIF1). Chronic treatment of mice with low doses of dexamethasone resulted in the development of systemic hypertension, cardiac hypertrophy and left ventricular dysfunction, as well as in pulmonary hypertension and pulmonary vascular remodeling. In contrast, mice deficient in p22phox-dependent NADPH oxidases were protected against these cardiovascular side effects. Mechanistically, dexamethasone failed to upregulate HIF1α levels in these mice, while vascular HIF1α deficiency prevented pulmonary vascular remodeling. Thus, p22phox-dependent NADPH oxidases and activation of the HIF pathway are critical elements in dexamethasone-induced cardiovascular pathologies and might provide interesting targets to limit cardiovascular side effects in patients on chronic glucocorticoid therapy.

Mineral-Doped Poly(L-lactide) Acid Scaffolds Enriched with Exosomes Improve Osteogenic Commitment of Human Adipose-Derived Mesenchymal Stem Cells

Exosomes derived from mesenchymal stem cells are extracellular vesicles released to facilitate cell communication and function. Recently, polylactic acid (PLA), calcium silicates (CaSi), and dicalcium phosphate dihydrate (DCPD) have been used to produce bioresorbable functional mineral-doped porous scaffolds-through thermally induced phase separation technique, as materials for bone regeneration. The aim of this study was to investigate the effect of mineral-doped PLA-based porous scaffolds enriched with exosome vesicles (EVs) on osteogenic commitment of human adipose mesenchymal stem cells (hAD-MSCs). Two different mineral-doped scaffolds were produced: PLA-10CaSi-10DCPD and PLA-5CaSi-5DCPD. Scaffolds surface micromorphology was investigated by ESEM-EDX before and after 28 days immersion in simulated body fluid (HBSS). Exosomes were deposited on the surface of the scaffolds and the effect of exosome-enriched scaffolds on osteogenic commitment of hAD-MSCs cultured in proximity of the scaffolds has been evaluated by real time PCR. In addition, the biocompatibility was evaluated by direct-contact seeding hAD-MSCs on scaffolds surface-using MTT viability test. In both formulations, ESEM showed pores similar in shape (circular and elliptic) and size (from 10-30 µm diameter). The porosity of the scaffolds decreased after 28 days immersion in simulated body fluid. Mineral-doped scaffolds showed a dynamic surface and created a suitable bone-forming microenvironment. The presence of the mineral fillers increased the osteogenic commitment of hAD-MSCs. Exosomes were easily entrapped on the surface of the scaffolds and their presence improved gene expression of major markers of osteogenesis such as collagen type I, osteopontin, osteonectin, osteocalcin. The experimental scaffolds enriched with exosomes, in particular PLA-10CaSi-10DCPD, increased the osteogenic commitment of MSCs. In conclusion, the enrichment of bioresorbable functional scaffolds with exosomes is confirmed as a potential strategy to improve bone regeneration procedures.

Vascular Wall-Mesenchymal Stem Cells Differentiation on 3D Biodegradable Highly Porous CaSi-DCPD Doped Poly (α-hydroxy) Acids Scaffolds for Bone Regeneration

Vascularization is a crucial factor when approaching any engineered tissue. Vascular wall-mesenchymal stem cells are an excellent in vitro model to study vascular remodeling due to their strong angiogenic attitude. This study aimed to demonstrate the angiogenic potential of experimental highly porous scaffolds based on polylactic acid (PLA) or poly-e-caprolactone (PCL) doped with calcium silicates (CaSi) and dicalcium phosphate dihydrate (DCPD), namely PLA-10CaSi-10DCPD and PCL-10CaSi-10DCPD, designed for the regeneration of bone defects. Vascular wall-mesenchymal stem cells (VW-MSCs) derived from pig thoracic aorta were seeded on the scaffolds and the expression of angiogenic markers, i.e. CD90 (mesenchymal stem/stromal cell surface marker), pericyte genes α-SMA (alpha smooth muscle actin), PDGFR-β (platelet-derived growth factor receptor-β), and NG2 (neuron-glial antigen 2) was evaluated. Pure PLA and pure PCL scaffolds and cell culture plastic were used as controls (3D in vitro model vs. 2D in vitro model). The results clearly demonstrated that the vascular wall mesenchymal cells colonized the scaffolds and were metabolically active. Cells, grown in these 3D systems, showed the typical gene expression profile they have in control 2D culture, although with some main quantitative differences. DNA staining and immunofluorescence assay for alpha-tubulin confirmed a cellular presence on both scaffolds. However, VW-MSCs cultured on PLA-10CaSi-10DCPD showed an individual cells growth, whilst on PCL-10CaSi-10DCPD scaffolds VW-MSCs grew in spherical clusters. In conclusion, vascular wall mesenchymal stem cells demonstrated the ability to colonize PLA and PCL scaffolds doped with CaSi-DCPD for new vessels formation and a potential for tissue regeneration.

Investigating the Osteoinductive Potential of a Decellularized Xenograft Bone Substitute

Bone grafting is the second most common tissue transplantation procedure worldwide. One of the alternative methods for bone repair under investigation is a tissue-engineered bone substitute. An ideal property of tissue-engineered bone substitutes is osteoinductivity, defined as the ability to stimulate primitive cells to differentiate into a bone-forming lineage. In the current study, we use a decellularization and oxidation protocol to produce a porcine bone scaffold and examine whether it possesses osteoinductive potential and can be used to create a tissue-engineered bone microenvironment. The decellularization protocol was patented by our lab and consists of chemical decellularization and oxidation steps using combinations of deionized water, trypsin, antimicrobials, peracetic acid, and triton-X100. To test if the bone scaffold was a viable host, preosteoblasts were seeded and analyzed for markers of osteogenic differentiation. The osteoinductive potential was observed in vitro with similar osteogenic markers being expressed in preosteoblasts seeded on the scaffolds and demineralized bone matrix. To assess these properties in vivo, scaffolds with and without preosteoblasts preseeded were subcutaneously implanted in mice for 4 weeks. MicroCT scanning revealed 1.6-fold increased bone volume to total volume ratio and 1.4-fold increase in trabecular thickness in scaffolds after implantation. The histological analysis demonstrates new bone formation and blood vessel formation with pentachrome staining demonstrating osteogenesis and angiogenesis, respectively, within the scaffold. Furthermore, CD31+ staining confirmed the endothelial lining of the blood vessels. These results demonstrate that porcine bone maintains its osteoinductive properties after the application of a patented decellularization and oxidation protocol developed in our laboratory. Future work must be performed to definitively prove osteogenesis of human mesenchymal stem cells, biocompatibility in large animal models, and osteoinduction/osseointegration in a relevant clinical model in vivo. The ability to create a functional bone microenvironment using decellularized xenografts will impact regenerative medicine, orthopedic reconstruction, and could be used in the research of multiple diseases.

Angiogenesis involvement by octacalcium phosphate-gelatin composite-driven bone regeneration in rat calvaria critical-sized defect

Effect of octacalcium phosphate/gelatin composite (OCP/Gel) on angiogenesis was studied by its implantation in rat calvaria critical-sized defect in relation to bone regeneration for 2 and 4 weeks. The implantation of OCP/Gel disks was analyzed by radiomorphometry using a radiopaque material perfusion (Microfil®) method and histomorphometry by hematoxylin and eosin-staining before and after the decalcification. Effect of the OCP dose in the range up to 4 mg per well on the capillary-like tube formation by human umbilical vein endothelial cells (HUVECs) was also examined in a transwell cell culture. The results showed that the blood vessels formation by OCP/Gel group was significantly higher at 2 weeks than other groups but decreased at 4 weeks during the advancement of new bone formation. The capillary-like tube formation was highest in an OCP dose of 1 mg per well while other OCP doses above or below 1 mg did not show such a stimulatory effect. The results established both in vivo and in vitro confirmed that OCP has a positive effect on angiogenesis during bone regeneration in a suitable dose ranges, suggesting that the angiogenesis stimulated by OCP could be involved in the OCP/Gel-enhanced bone regeneration. STATEMENT OF SIGNIFICANCE: We have reported that octacalcium phosphate (OCP) materials display stimulatory capacities on the bone tissue-related cells. However, the effect of OCP on the angiogenesis and its relation to the OCP-enhanced bone regeneration is unknown. This study confirmed the capacity of OCP on angiogenesis before increasing the new bone mass after the implantation of a composite of OCP and gelatin (OCP/Gel). The blood vessels formation took place associated with the area beginning of the new bone formation, which finally decreased together with development of bone formation. Because OCP was ascertained stimulating the capillary-like tube formation in HUVEC culture with a certain OCP dose, the present study is the first report showing the capacity of OCP on angiogenesis during the OCP/Gel-enhanced bone regeneration.