Osteoblast/fibroblast coculture derived bioactive ECM with unique matrisome profile facilitates bone regeneration

Advancing bone regeneration: Unveiling the potential of 3D cell models in the evaluation of bone regenerative materials

Bone, a rigid yet regenerative tissue, has garnered extensive attention for its impressive healing abilities. Despite advancements in understanding bone repair and creating treatments for bone injuries, handling nonunions and large defects remains a major challenge in orthopedics. The rise of bone regenerative materials is transforming the approach to bone repair, offering innovative solutions for nonunions and significant defects, and thus reshaping orthopedic care. Evaluating these materials effectively is key to advancing bone tissue regeneration, especially in difficult healing scenarios, making it a critical research area. Traditional evaluation methods, including two-dimensional cell models and animal models, have limitations in predicting accurately. This has led to exploring alternative methods, like 3D cell models, which provide fresh perspectives for assessing bone materials' regenerative potential. This paper discusses various techniques for constructing 3D cell models, their pros and cons, and crucial factors to consider when using these models to evaluate bone regenerative materials. We also highlight the significance of 3D cell models in the in vitro assessments of these materials, discuss their current drawbacks and limitations, and suggest future research directions. STATEMENT OF SIGNIFICANCE: This work addresses the challenge of evaluating bone regenerative materials (BRMs) crucial for bone tissue engineering. It explores the emerging role of 3D cell models as superior alternatives to traditional methods for assessing these materials. By dissecting the construction, key factors of evaluating, advantages, limitations, and practical considerations of 3D cell models, the paper elucidates their significance in overcoming current evaluation method shortcomings. It highlights how these models offer a more physiologically relevant and ethically preferable platform for the precise assessment of BRMs. This contribution is particularly significant for "Acta Biomaterialia" readership, as it not only synthesizes current knowledge but also propels the discourse forward in the search for advanced solutions in bone tissue engineering and regeneration.

Construction of a Decellularized Multicomponent Extracellular Matrix Interpenetrating Network Scaffold by Gelatin Microporous Hydrogel 3D Cell Culture System

Interface tissue repair requires the construction of biomaterials with integrated structures of multiple protein types. Hydrogels that modulate internal porous structures provide a 3D microenvironment for encapsulated cells, making them promise for interface tissue repair. Currently, reduction of intrinsic immunogenicity and increase of bioactive extracellular matrix (ECM) secretion are issues to be considered in these materials. In this study, gelatin methacrylate (GelMA) hydrogel is used to encapsulate chondrocytes and construct a phase transition 3D cell culture system (PTCC) by utilizing the thermosensitivity of gelatin microspheres to create micropores within the hydrogel. The types of bioactive extracellular matrix protein formation by chondrocytes encapsulated in hydrogels are investigated in vitro. After 28 days of culture, GelMA PTCC forms an extracellular matrix predominantly composed of collagen type II, collagen type I, and fibronectin. After decellularization, the protein types and mechanical properties are well preserved, fabricating a decellularized tissue-engineered extracellular matrix and GelMA hydrogel interpenetrating network hydrogel (dECM-GelMA IPN) consisting of GelMA hydrogel as the first-level network and the ECM secreted by chondrocytes as the second-level network. This material has the potential to mediate the repair and regeneration of tendon-bone interface tissues with multiple protein types.

Fibroblast-derived extracellular vesicles as trackable efficient transporters of an experimental nanodrug with fibrotic heart and lung targeting

The discovery of extracellular vesicles (EVs) as efficient exogenous biotransporters of therapeutic agents into cells across biological membranes is an exciting emerging field. Especially the potential of EVs as targeted delivery systems for diseases with selective treatments, such as fibrosis, whose treatment causes side effects in other organs not involved in the disease. Methods: In this study, we collected embryonic fibroblast-derived EVs from two different centrifugation fractions, 10 K g and 100 K g fractions from a NIH-3T3 cell line loaded with an experimental drug. Mice with fibrotic hearts and lungs were obtained by administration of angiotensin II. We generated fluorescent EVs and bioluminescent drug to observe their accumulation by colocalization of their signals in fibrotic heart and lung. The biodistribution of the drug in various organs was obtained by detecting the Au present in the drug nanostructure. Results: The drug-loaded EVs successfully reduced fibrosis in pathological fibroblasts in vitro, and modified the biodistribution of the experimental drug, enabling it to reach the target organs in vivo. We described the pre-analytical characteristics of EVs related to physical variables, culture and harvesting conditions, crucial for their in vivo application as nanotransporters using a previously validated protein-based antifibrotic drug. The results showed the colocalization of EVs and the experimental drug in vivo and ex vivo and the efficient reduction of fibrosis in vitro. This work demonstrates that 10K-EVs and 100K-EVs derived from fibroblasts can act as effective biotransporters for targeted drug delivery to profibrotic fibroblasts, lungs, or heart. Conclusion: We observed that fibroblast-derived 10K-EVs and 100K-EVs are useful biotransporters encapsulating a new generation drug leading to a reduction of fibrosis in profibrotic fibroblasts in vitro. In addition, drug containing EVs were shown to reach fibrotic heart and lungs in vivo, enhancing free drug biodistribution.

Distinguished biomimetic dECM system facilitates early detection of metastatic breast cancer cells

Breast cancer is the most prevalent malignant tumor affecting women's health. Bone is the most common distant metastatic organ, worsening the quality of life and increasing the mortality of patients. Early detection of breast cancer bone metastasis is urgent for halting disease progression and improving tumor prognosis. Recently, extracellular matrix (ECM) with biomimetic tissue niches opened a new avenue for tumor models in vitro. Here, we developed a biomimetic decellularized ECM (dECM) system to recapitulate bone niches at different situations, bone mimetic dECM from osteoblasts (BM-ECM) and bone tumor mimetic dECM from osteosarcoma cells (OS-ECM). The two kinds of dECMs exhibited distinct morphology, protein composition, and distribution. Interestingly, highly metastatic breast cancer cells tended to adhere and migrate on BM-ECM, while lowly metastatic breast cancer cells preferred the OS-ECM niche. Epithelial-to-mesenchymal transition was a potential mechanism to initiate the breast cancer cell migration on different biomimetic dECMs. Importantly, in the nude mice model, the dECM system captured metastatic breast cancer cells as early as 10 days after orthotopic transplantation in mammary gland pads, with higher signal on BM-ECM than that on OS-ECM. Collectively, the biomimetic dECM system might be a promising tumor model to distinguish the metastatic ability of breast cancer cells in vitro and to facilitate early detection of metastatic breast cancer cells in vivo, contributing to the diagnosis of breast cancer bone metastasis.

A biomimetic in situ mineralization ECM composite scaffold to promote endogenous bone regeneration

Bone tissue engineering scaffolds constructed from single-component organic materials have inherent limitations. Inspired by the hierarchical structure of physiological natural bone hard tissues, our research explores the construction of organic-inorganic composite scaffold for bone regeneration. In this study, we used a natural and readily obtainable extracellular matrix (ECM) material, i.e., decellularized small intestinal submucosa (SIS), to build the organic component of a phosphorylated hydroxyapatite nanocrystal-containing composite scaffold (nHA@SIS). Guided by polymer-induced liquid-precursor theory, we introduced a soluble inorganic mineralization solution to achieve an inorganic component of nHA@SIS. Using in situ mineralization, we successfully formed inorganic component within SIS and constructed nHA@SIS composite scaffold. We analyzed the physicochemical properties and the osteogenic role of nHA@SIS via a series of in vitro and in vivo studies. Compared with SIS scaffold, the nHA@SIS possessed suitable physicochemical properties, maintained the excellent cell activity of SIS and better guided reorganization of the cell skeleton, thereby achieving superior osteoconductivity and maintaining osteoinductivity at the protein and gene levels. Furthermore, the rat cranial defect area in the nHA@SIS scaffold group was mostly repaired after 12 weeks of implantation, with a larger amount of higher-density new bone tissue being visible at the edge and center than SIS and blank control group. This significantly improved in vivo osteogenic ability indicated the great potential of nHA@SIS for bone tissue engineering applications.

The enhanced properties and bioactivity of poly-ε-caprolactone/poly lactic-co-glycolic acid doped with carbonate hydroxyapatite-egg white

Synthetic polymers, such as PCL and PLGA, are among the main material choices in tissue engineering because of their stable structures and strong mechanical properties. In this study, we designed polycaprolactone (PCL)/polylactic-co-glycolate acid (PLGA) nanofibers doped with carbonate hydroxyapatite (CHA) and egg white (EW) with enhanced properties. The addition of CHA and EW significantly influenced the properties and morphology of PCL/PLGA nanofibers; whereby the CHA substitution (PCL/PLGA/CHA) greatly increased the mechanical properties related to the Young's modulus and EW doping (PCL/PLGA/CHA/EW) increased the elongation at break. Bioactivity tests of PCL/PLGA/CHA/EW after immersion in the SBF for 3 to 9 days showed increased fiber diameters and a good swelling capacity that could improve cell adhesion, while biocompatibility tests with NIH-3T3 fibroblast cells showed good cell proliferation (85%) after 48 h and antibacterial properties against S. aureus.

Substrate Stiffness of Bone Microenvironment Controls Functions of Pre-Osteoblasts and Fibroblasts In Vitro

The formation of bone in a bone defect is accomplished by osteoblasts, while the over activation of fibroblasts promotes fibrosis. However, it is not clear how the extracellular matrix stiffness of the bone-regeneration microenvironment affects the function of osteoblasts and fibroblasts. This study aim to investigate the effect of bone-regeneration microenvironment stiffness on cell adhesion, cell proliferation, cell differentiation, synthesizing matrix ability and its potential mechanisms in mechanotransduction, in pre-osteoblasts and fibroblasts. Polyacrylamide substrates mimicking the matrix stiffness of different stages of the bone-healing process (15 kPa, mimic granulation tissue; 35 kPa, mimic osteoid; 150 kPa, mimic calcified bone matrix) were prepared. Mouse pre-osteoblasts MC3T3-E1 and mouse fibroblasts NIH3T3 were plated on three types of substrates, respectively. There were significant differences in the adhesion of pre-osteoblasts and fibroblasts on different polyacrylamide substrates. Runx2 expression increased with increasing substrate stiffness in pre-osteoblasts, while no statistical differences were found in the Acta2 expression in fibroblasts on three substrates. OPN expression in pre-osteoblasts, as well as Fn1 and Col1a1 expression in fibroblasts, decreased with increasing stiffness. The difference between the cell traction force generated by pre-osteoblasts and fibroblasts on substrates was also found. Our results indicated that substrate stiffness is a potent regulator of pre-osteoblasts and fibroblasts with the ability of promoting osteogenic differentiation of pre-osteoblasts, while having no effect on myofibroblast differentiation of fibroblasts.

Mesenchymal Stem Cells and Exosomes: A Novel Therapeutic Approach for Corneal Diseases

The cornea, with its delicate structure, is vulnerable to damage from physical, chemical, and genetic factors. Corneal transplantation, including penetrating and lamellar keratoplasties, can restore the functions of the cornea in cases of severe damage. However, the process of corneal transplantation presents considerable obstacles, including a shortage of available donors, the risk of severe graft rejection, and potentially life-threatening complications. Over the past few decades, mesenchymal stem cell (MSC) therapy has become a novel alternative approach to corneal regeneration. Numerous studies have demonstrated the potential of MSCs to differentiate into different corneal cell types, such as keratocytes, epithelial cells, and endothelial cells. MSCs are considered a suitable candidate for corneal regeneration because of their promising therapeutic perspective and beneficial properties. MSCs compromise unique immunomodulation, anti-angiogenesis, and anti-inflammatory properties and secrete various growth factors, thus promoting corneal reconstruction. These effects in corneal engineering are mediated by MSCs differentiating into different lineages and paracrine action via exosomes. Early studies have proven the roles of MSC-derived exosomes in corneal regeneration by reducing inflammation, inhibiting neovascularization, and angiogenesis, and by promoting cell proliferation. This review highlights the contribution of MSCs and MSC-derived exosomes, their current usage status to overcome corneal disease, and their potential to restore different corneal layers as novel therapeutic agents. It also discusses feasible future possibilities, applications, challenges, and opportunities for future research in this field.

Fabrication and Evaluation of Porous dECM/PCL Scaffolds for Bone Tissue Engineering

Porous scaffolds play a crucial role in bone tissue regeneration and have been extensively investigated in this field. By incorporating a decellularized extracellular matrix (dECM) onto tissue-engineered scaffolds, bone regeneration can be enhanced by replicating the molecular complexity of native bone tissue. However, the exploration of porous scaffolds with anisotropic channels and the effects of dECM on these scaffolds for bone cells and mineral deposition remains limited. To address this gap, we developed a porous polycaprolactone (PCL) scaffold with anisotropic channels and functionalized it with dECM to capture the critical physicochemical properties of native bone tissue, promoting osteoblast cells' proliferation, differentiation, biomineralization, and osteogenesis. Our results demonstrated the successful fabrication of porous dECM/PCL scaffolds with multiple channel sizes for bone regeneration. The incorporation of 100 μm grid-based channels facilitated improved nutrient and oxygen infiltration, while the porous structure created using 30 mg/mL of sodium chloride significantly enhanced the cells' attachment and proliferation. Notably, the mechanical properties of the scaffolds closely resembled those of human bone tissue. Furthermore, compared with pure PCL scaffolds, the presence of dECM on the scaffolds substantially enhanced the proliferation and differentiation of bone marrow stem cells. Moreover, dECM significantly increased mineral deposition on the scaffold. Overall, the dECM/PCL scaffold holds significant potential as an alternative bone graft substitute for repairing bone injuries.

A novel decellularized matrix of Wnt signaling-activated osteocytes accelerates the repair of critical-sized parietal bone defects with osteoclastogenesis, angiogenesis, and neurogenesis

Cell source is the key to decellularized matrix (DM) strategy. This study compared 3 cell types, osteocytes with/without dominant active Wnt/β-catenin signaling (daCO and WTO) and bone marrow stromal cells (BMSCs) for their DMs in bone repair. Decellularization removes all organelles and >95% DNA, and retained >74% collagen and >71% GAG, maintains the integrity of cell basement membrane with dense boundaries showing oval and honeycomb structure in osteocytic DM and smooth but irregular shape in the BMSC-DM. DM produced higher cell survival rate (90%) and higher proliferative activity. In vitro, daCO-DM induces more and longer stress fibers in BMSCs, conducive to cell adhesion, spreading, and osteogenic differentiation. 8-wk after implantation of the critical-sized parietal bone defect model, daCO-DM formed tight structures, composed of a large number of densely-arranged type-I collagen under polarized light microscope, which is similar to and integrated with host bone. BV/TV (>54%) was 1.5, 2.9, and 3.5 times of WTO-DM, BMSC-DM, and none-DM groups, and N.Ob/T.Ar (3.2 × 10²/mm²) was 1.7, 2.9, and 3.3 times. At 4-wk, daCO-DM induced osteoclastogenesis, 2.3 times higher than WTO-DM; but BMSC-DM or none-DM didn't. daCO-DM increased the expression of RANKL and MCSF, Vegfa and Angpt1, and Ngf in BMSCs, which contributes to osteoclastogenesis, angiogenesis, and neurogenesis, respectively. daCO-DM promoted H-type vessel formation and nerve markers β3-tubulin and NeuN expression. Conclusion: daCO-DM produces metabolic and neurovascularized organoid bone to accelerate the repair of bone defects. These features are expected to achieve the effect of autologous bone transplantation, suitable for transformation application.

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Decellularized matrix of osteocytes with dominant-active β-catenin (daCO-DM) promotes osteogenesis for regenerative repair.

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daCO-DM induces BMSCs to form stress fibers, conducive to cell adhesion, spreading, and differentiation towards osteoblasts.

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daCO-DM-induced osteoblasts have strong activity secreting dense and orderly-arranged type I collagen as host bone’s.

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daCO-DM induces BMSCs to express pre-osteoclastogenic cytokine RANKL and MCSF for osteoclastogenesis of marrow monocytes.

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daCO-DM enhances BMSCs to express angiogenic Vegfa and Angpt1, and neurogenic Ngf potentially for neurovascularization.

Self-Adaptive Antibacterial Scaffold with Programmed Delivery of Osteogenic Peptide and Lysozyme for Infected Bone Defect Treatment

Bone defects caused by disease or trauma are often accompanied by infection, which severely disrupts the normal function of bone tissue at the defect site. Biomaterials that can simultaneously reduce inflammation and promote osteogenesis are effective tools for addressing this problem. In this study, we set up a programmed delivery platform based on a chitosan scaffold to enhance its osteogenic activity and prevent implant-related infections. In brief, the osteogenic peptide sequence (YGFGG) was modified onto the surface of cowpea chlorotic mottle virus (CCMV) to form CCMV-YGFGG nanoparticles. CCMV-YGFGG exhibited good biocompatibility and osteogenic ability in vitro. Then, CCMV-YGFGG and lysozyme were loaded on the chitosan scaffold, which exhibited a good antibacterial effect and promoted bone regeneration for infected bone defect treatment. As a delivery platform, the scaffold showed staged release of lysozyme and CCMV-YGFGG, which facilitates the regeneration of infected bone defects. Our study provides a novel and promising strategy for the treatment of infected bone defects.

ATBF1 is a potential diagnostic marker of histological grade and functions via WNT5A in breast cancer

BACKGROUND

Histological grade has been demonstrated to be an important factor of breast cancer outcome and is associated with cell differentiation and is currently being evaluated via H&E-stained sections. Molecular biomarkers are essential to improve the accuracy of histological grading. ATBF1, a large transcription factor, has been considered a tumor suppressor gene with frequent mutations or deletions in multiple cancers. In breast cancer, ATBF1 was reported to function in cell differentiation and mammary development. However, its role in the clinic has rarely been reported.

METHODS

Breast cancer tissues (BCTs) and adjacent noncancerous tissues (ANCTs) were collected to analyze the expression of ATBF1 at the mRNA and protein levels. Three anti-ATBF1 antibodies recognizing independent peptides of ATBF1 (N-terminal end, middle region and C-terminal end) were applied for IHC staining. Small interfering RNA (siRNA) was used to silence ATBF1 expression and to investigate the roles of ATBF1 in MCF7 cells. Microarrays were introduced to analyze the differentially expressed genes, enriched GO terms and KEGG terms regulated by ATBF1 and its potential downstream genes, which were further confirmed in vitro and in clinical samples.

RESULTS

The expression of ATBF1 was reduced in BCTs at both the mRNA and protein levels compared with that in ANCTs. ATBF1 protein was predominantly localized in the nucleus of ANCTs but in the cytoplasm of BCTs. Both the mRNA and protein levels of ATBF1 were significantly correlated with histological grade. Consistently, knockdown of ATBF1 increased stemness marker expression and reduced differentiation markers in vitro. Further analysis identified WNT5A as an essential downstream gene of ATBF1 in breast cancer cells. Treatment of WNT5A disrupted cell proliferation induced by ATBF1 silencing. In BCTs, a significant correlation was observed between the expression of WNT5A and ATBF1.

CONCLUSION

The results indicated that ATBF1 expression might be a useful diagnostic marker associated with histological grade and breast cancer malignancy. WNT5A and its signaling pathway are novel mechanisms by which ATBF1 contributes to breast cancer tumorigenesis.

Recent advances in biofunctional guided bone regeneration materials for repairing defective alveolar and maxillofacial bone: A review

The anatomy of the oral and maxillofacial sites is complex, and bone defects caused by trauma, tumors, and inflammation in these zones are extremely difficult to repair. Among the most effective and reliable methods to attain osteogenesis, the guided bone regeneration (GBR) technique is extensively applied in defective oral and maxillofacial GBR. Furthermore, endowing biofunctions is crucial for GBR materials applied in repairing defective alveolar and maxillofacial bones. In this review, recent advances in designing and fabricating GBR materials applied in oral and maxillofacial sites are classified and discussed according to their biofunctions, including maintaining space for bone growth; facilitating the adhesion, migration, and proliferation of osteoblasts; facilitating the migration and differentiation of progenitor cells; promoting vascularization; providing immunoregulation to induce osteogenesis; suppressing infection; and effectively mimicking natural tissues using graded biomimetic materials. In addition, new processing strategies (e.g., 3D printing) and new design concepts (e.g., developing bone mimetic extracellular matrix niches and preparing scaffolds to suppress connective tissue to actively acquire space for bone regeneration), are particularly worthy of further study. In the future, GBR materials with richer biological functions are expected to be developed based on an in-depth understanding of the mechanism of bone-GBR-material interactions.

Spheroid co-culture of BMSCs with osteocytes yields ring-shaped bone-like tissue that enhances alveolar bone regeneration

Oral and maxillofacial bone defects severely impair appearance and function, and bioactive materials are urgently needed for bone regeneration. Here, we spheroid co-cultured green fluorescent protein (GFP)-labeled bone marrow stromal cells (BMSCs) and osteocyte-like MLO-Y4 cells in different ratios (3:1, 2:1, 1:1, 1:2, 1:3) or as monoculture. Bone-like tissue was formed in the 3:1, 2:1, and 1:1 co-cultures and MLO-Y4 monoculture. We found a continuous dense calcium phosphate structure and spherical calcium phosphate similar to mouse femur with the 3:1, 2:1, and 1:1 co-cultures, along with GFP-positive osteocyte-like cells encircled by an osteoid-like matrix similar to cortical bone. Flake-like calcium phosphate, which is more mature than spherical calcium phosphate, was found with the 3:1 and 2:1 co-cultures. Phosphorus and calcium signals were highest with 3:1 co-culture, and this bone-like tissue was ring-shaped. In a murine tooth extraction model, implantation of the ring-shaped bone-like tissue yielded more bone mass, osteoid and mineralized bone, and collagen versus no implantation. This tissue fabricated by spheroid co-culturing BMSCs with osteocytes yields an internal structure and mineral composition similar to mouse femur and could promote bone formation and maturation, accelerating regeneration. These findings open the way to new strategies in bone tissue engineering.

Dental pulp stem cell-derived extracellular matrix: autologous tool boosting bone regeneration

BACKGROUND AIMS

To facilitate artificial bone construct integration into a patient's body, scaffolds are enriched with different biologically active molecules. Among various scaffold decoration techniques, coating surfaces with cell-derived extracellular matrix (ECM) is a rapidly growing field of research. In this study, for the first time, this technology was applied using primary dental pulp stem cells (DPSCs) and tested for use in artificial bone tissue construction.

METHODS

Rat DPSCs were grown on three-dimensional-printed porous polylactic acid scaffolds for 7 days. After the predetermined time, samples were decellularized, and the remaining ECM detailed proteomic analysis was performed. Further, DPSC-secreated ECM impact to mesenchymal stromal cells (MSC) behaviour as well as its role in osteoregeneration induction were analysed.

RESULTS

It was identified that DPSC-specific ECM protein network ornamenting surface-enhanced MSC attachment, migration and proliferation and even promoted spontaneous stem cell osteogenesis. This protein network also demonstrated angiogenic properties and did not stimulate MSCs to secrete molecules associated with scaffold rejection. With regard to bone defects, DPSC-derived ECM recruited endogenous stem cells, initiating the bone self-healing process. Thus, the DPSC-secreted ECM network was able to significantly enhance artificial bone construct integration and induce successful tissue regeneration.

CONCLUSIONS

DPSC-derived ECM can be a perfect tool for decoration of various biomaterials in the context of bone tissue engineering.

Multifunctional GelMA platforms with nanomaterials for advanced tissue therapeutics

Polymeric hydrogels are fascinating platforms as 3D scaffolds for tissue repair and delivery systems of therapeutic molecules and cells. Among others, methacrylated gelatin (GelMA) has become a representative hydrogel formulation, finding various biomedical applications. Recent efforts on GelMA-based hydrogels have been devoted to combining them with bioactive and functional nanomaterials, aiming to provide enhanced physicochemical and biological properties to GelMA. The benefits of this approach are multiple: i) reinforcing mechanical properties, ii) modulating viscoelastic property to allow 3D printability of bio-inks, iii) rendering electrical/magnetic property to produce electro-/magneto-active hydrogels for the repair of specific tissues (e.g., muscle, nerve), iv) providing stimuli-responsiveness to actively deliver therapeutic molecules, and v) endowing therapeutic capacity in tissue repair process (e.g., antioxidant effects). The nanomaterial-combined GelMA systems have shown significantly enhanced and extraordinary behaviors in various tissues (bone, skin, cardiac, and nerve) that are rarely observable with GelMA. Here we systematically review these recent efforts in nanomaterials-combined GelMA hydrogels that are considered as next-generation multifunctional platforms for tissue therapeutics. The approaches used in GelMA can also apply to other existing polymeric hydrogel systems.

Rational integration of defense and repair synergy on PEEK osteoimplants via biomimetic peptide clicking strategy

Polyetheretherketone (PEEK) has been widely used as orthopedic and dental materials due to excellent mechanical and physicochemical tolerance. However, its biological inertness, poor osteoinduction, and weak antibacterial activity make the clinical applications in a dilemma. Inspired by the mussel adhesion mechanism, here we reported a biomimetic surface strategy for rational integration and optimization of anti-infectivity and osteo-inductivity onto PEEK surfaces using a mussel foot proteins (Mfps)-mimic peptide with clickable azido terminal. The peptide enables mussel-like adhesion on PEEK biomaterial surfaces, leaving azido groups for the further steps of biofunctionalizations. In this study, antimicrobial peptide (AMP) and osteogenic growth peptide (OGP) were bioorthogonally clicked on the azido-modified PEEK biomaterials to obtain a dual-effect of host defense and tissue repair. Since bioorthogonal clicking allows precise collocation between AMP and OGP through changing their feeding molar ratios, an optimal PEEK surface was finally obtained in this research, which could long-term inhibit bacterial growth, stabilize bone homeostasis and facilitate interfacial bone regeneration. In a word, this upgraded mussel surface strategy proposed in this study is promising for the surface bioengineering of inert medical implants, in particular, achieving rational integration of multiple biofunctions to match clinical requirements.

Mesenchymal Stem Cell-Derived Exosomes as a Novel Strategy for the Treatment of Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) has been reported to be the most prevalent contributor to low back pain, posing a significant strain on the healthcare systems on a global scale. Currently, there are no approved therapies available for the prevention of the progressive degeneration of intervertebral disc (IVD); however, emerging regenerative strategies that aim to restore the normal structure of the disc have been fundamentally promising. In the last decade, mesenchymal stem cells (MSCs) have received a significant deal of interest for the treatment of IVDD due to their differentiation potential, immunoregulatory capabilities, and capability to be cultured and regulated in a favorable environment. Recent investigations show that the pleiotropic impacts of MSCs are regulated by the production of soluble paracrine factors. Exosomes play an important role in regulating such effects. In this review, we have summarized the current treatments for disc degenerative diseases and their limitations and highlighted the therapeutic role and its underlying mechanism of MSC-derived exosomes in IVDD, as well as the possible future developments for exosomes.

BMSCs and Osteoblast-Engineered ECM Synergetically Promotes Osteogenesis and Angiogenesis in an Ectopic Bone Formation Model

Bone mesenchymal stem cells (BMSCs) have been extensively used in bone tissue engineering because of their potential to differentiate into multiple cells, secrete paracrine factors, and attenuate immune responses. Biomaterials are essential for the residence and activities of BMSCs after implantation in vivo. Recently, extracellular matrix (ECM) modification with a favorable regenerative microenvironment has been demonstrated to be a promising approach for cellular activities and bone regeneration. The aim of the present study was to evaluate the effects of BMSCs combined with cell-engineered ECM scaffolds on osteogenesis and angiogenesis in vivo. The ECM scaffolds were generated by osteoblasts on the small intestinal submucosa (SIS) under treatment with calcium (Ca)-enriched medium and icariin (Ic) after decellularization. In a mouse ectopic bone formation model, the SIS scaffolds were demonstrated to reduce the immune response, and lower the levels of immune cells compared with those in the sham group. Ca/Ic-ECM modification inhibited the degradation of the SIS scaffolds in vivo. The generated Ca/Ic-SIS scaffolds ectopically promoted osteogenesis according to the results of micro-CT and histological staining. Moreover, BMSCs on Ca/Ic-SIS further increased the bone volume percentage (BV/TV) and bone density. Moreover, angiogenesis was also enhanced by the Ca/Ic-SIS scaffolds, resulting in the highest levels of neovascularization according to the data ofCD31 staining. In conclusion, osteoblast-engineered ECM under directional induction is a promising strategy to modify biomaterials for osteogenesis and angiogenesis. BMSCs synergetically improve the properties of ECM constructs, which may contribute to the repair of large bone defects.

The inclusion of leukocytes into platelet rich plasma reduces scaffold stability and hinders extracellular matrix remodelling

BACKGROUND

Scaffolds should have controllable degradation rate and allow cells to produce their own extracellular matrix. Platelet rich plasma (PRP) is a source of autologous growth factors and proteins embedded in a 3D fibrin scaffold. There is no consensus regarding the obtaining conditions and composition of PRPs. The aim of this study was to evaluate how the inclusion of leukocytes (L-PRP) in plasma rich in growth factors (PRGF) may alter the process of fibrinolysis. The effect of different combinations of cellular phenotypes with PRGF and L-PRP clots on both the fibrinolysis and matrix deposition process was also determined.

METHODS

PRGF and L-PRP clots were incubated for 14 days and D-dimer and type I collagen were determined in their conditioned media to evaluate clots' stability. For remodelling assays, gingival fibroblasts, alveolar osteoblasts and human umbilical vein endothelial cells (HUVEC) were seeded onto the two types of clots for 14 days. D-dimer, type I collagen, and laminin α4 were measured by ELISA kits in their conditioned media. Morphological and histological analysis were also performed. Cell proliferation was additionally determined RESULTS: PRGF clots preserved their stability as shown by the low levels of both D-dimer and collagen type I compared to those obtained for L-PRP clots. The inclusion of both gingival fibroblasts and alveolar osteoblasts stimulated a higher fibrinolysis in the PRGF clots. In contrast to this, the degradation rates of both PRGF and L-PRP clots remained unchanged after culturing with the endothelial cells. In all cases, type I collagen and laminin α4 levels were in line with the degree of clots' degradation. In all phenotypes, cell proliferation was significantly higher in PRGF than in L-PRP clots.

CONCLUSION

The inclusion of leukocytes in PRGF scaffolds reduced their stability, decreased cell number and slowed down cell remodelling.

Anodized Biomedical Stainless-Steel Mini-Implant for Rapid Recovery in a Rabbit Model

The study aimed to analyze the recovery period of the anodized 316L biomedical stainless steel (BSS) mini-implant through its implantation on femur of rabbit model. The 316L BSS mini-implant was modified by an electrochemical anodization approach with different voltages. The anodized samples were characterized via field-emission scanning electron microscopy, X-ray diffractometry, and X-ray photoelectron spectroscopy. The biocompatibility was assessed by cell culture assay. The anodized mini-implant was implanted on rabbit’s femur then evaluated histologically after 4 and 8 weeks. Analytical results indicated that the topography of the anodized mini-implant at 5 V for 5 min consisted of a dual (micro/nano) porous structure. Oxide film of Cr2O3 was formed on the surface of anodized mini-implant after anodizing with 5 V for 5 min. In vitro cell culture assay revealed that fibroblast cells (NIH-3T3) on the anodized samples were more firmly attached as compared with the control sample. Moreover, histological analysis demonstrated that the anodized mini-implant improved bone recovering at 4 weeks after implantation. Thus, this study suggests that the anodized 316L BSS mini-implant could be a potential choice as anchorage device for effective and efficient orthodontic treatment.

Microgravity Effects on the Matrisome

Gravity is fundamental factor determining all processes of development and vital activity on Earth. During evolution, a complex mechanism of response to gravity alterations was formed in multicellular organisms. It includes the "gravisensors" in extracellular and intracellular spaces. Inside the cells, the cytoskeleton molecules are the principal gravity-sensitive structures, and outside the cells these are extracellular matrix (ECM) components. The cooperation between the intracellular and extracellular compartments is implemented through specialized protein structures, integrins. The gravity-sensitive complex is a kind of molecular hub that coordinates the functions of various tissues and organs in the gravitational environment. The functioning of this system is of particular importance under extremal conditions, such as spaceflight microgravity. This review covers the current understanding of ECM and associated molecules as the matrisome, the features of the above components in connective tissues, and the role of the latter in the cell and tissue responses to the gravity alterations. Special attention is paid to contemporary methodological approaches to the matrisome composition analysis under real space flights and ground-based simulation of its effects on Earth.

Engineering hiPSC-CM and hiPSC-EC laden 3D nanofibrous splenic hydrogel for improving cardiac function through revascularization and remuscularization in infarcted heart

Cell therapy has been a promising strategy for cardiac repair after myocardial infarction (MI), but a poor ischemic environment and low cell delivery efficiency remain significant challenges. The spleen serves as a hematopoietic stem cell niche and secretes cardioprotective factors after MI, but it is unclear whether it could be used for human pluripotent stem cell (hiPSC) cultivation and provide a proper microenvironment for cell grafts against the ischemic environment. Herein, we developed a splenic extracellular matrix derived thermoresponsive hydrogel (SpGel). Proteomics analysis indicated that SpGel is enriched with proteins known to modulate the Wnt signaling pathway, cell-substrate adhesion, cardiac muscle contraction and oxidation-reduction processes. In vitro studies demonstrated that hiPSCs could be efficiently induced into endothelial cells (iECs) and cardiomyocytes (iCMs) with enhanced function on SpGel. The cytoprotective effect of SpGel on iECs/iCMs against oxidative stress damage was also proven. Furthermore, in vivo studies revealed that iEC/iCM-laden SpGel improved cardiac function and inhibited cardiac fibrosis of infarcted hearts by improving cell survival, revascularization and remuscularization. In conclusion, we successfully established a novel platform for the efficient generation and delivery of autologous cell grafts, which could be a promising clinical therapeutic strategy for cardiac repair and regeneration after MI.

Implantable PEKK/tantalum microparticles composite with improved surface performances for regulating cell behaviors, promoting bone formation and osseointegration

Polyetherketoneketone (PEKK) exhibits admirable biocompatibility and mechanical performances but bioinert while tantalum (Ta) possesses excellent osteogenesis and osseointegration but high elastic modulus and density, and processing is too difficult and expensive. In the present study, combining of the advantages of both PEKK and Ta, implantable composites of PEKK/Ta were fabricated by blending PEKK with Ta microparticles of 20 v% (PT20) and 40 v% (PT40) content. In comparison with PT20 and PEKK, the surface hydrophilicity, surface energy, roughness and proteins adsorption as well as mechanical performances of PT40 significantly increased because of the higher Ta particles content in PEKK. Furthermore, PT40 exhibited the mechanical performances (e.g., compressive strength and modulus of elasticity) close to the cortical bone of human. Compared with PT20 and PEKK, PT40 with higher Ta content remarkably enhanced the responses (including adhesion, proliferation and osteogenic differentiation) of MC3T3-E1 cells in vitro. Moreover, PT40 markedly improved bone formation as well as osseointegration in vivo. In short, incorporation of Ta microparticles into PEKK created implantable composites with improved surface performances, which played key roles in stimulating cell responses/bone formation as well as promoting osseointegration. PT40 might have great potential for bear-loading bone substitute.