Bioactive cell-derived matrices combined with polymer mesh scaffold for osteogenesis and bone healing

Bone Fillers with Balance Between Biocompatibility and Antimicrobial Properties

Millions of people request bone regeneration every year, and the market for bone grafting materials has a positive trend. The most used biomaterials applied to replace and regenerate bone are based on collagen and different types of ceramics in order to mimic natural bone matrix. However, there are a lot of implant-associated infections after surgery, or the implants are rejected because of reduced biocompatibility, and this is why the research into graft bone materials is still a challenge. This study aims to develop and characterize novel biomimetic bone fillers which have simultaneously both antimicrobial properties and biocompatibility with human bone marrow-derived mesenchymal stem cells (BMSCs). Type I collagen and calcium triphosphate in a ratio of 1:1 were used as a control, according to our previous studies, and ZnO, functionalized with different percentages of Satureja thymbra L. essential oils, was added as an antimicrobial, promoting bone growth, mineralization, and formation. The bone fillers were obtained by freeze-drying in spongious forms and characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), water uptake, biodegradability over time, antimicrobial activity against Staphylococcus aureus and Escherichia coli and viability and proliferation of human BMSCs. The graft material showed a higher porosity with interconnected pores, gradual resorption over time and a balance between antimicrobial properties and biocompatibility and was chosen as an ideal bone filler.

Osteogenic Differentiation of Adipose Tissue-Derived Mesenchymal Stem Cells on Composite Polymeric Scaffolds: A Review

The mesenchymal stem cells (MSCs) are the fundamental part of bone tissue engineering for the emergence of reconstructive medicine. Bone tissue engineering has recently been considered a promising strategy for treating bone diseases and disorders. The technique needs a scaffold to provide an environment for cell attachment to maintain cell function and a rich source of stem cells combined with appropriate growth factors. MSCs can be isolated from adipose tissue (ASCs), bone marrow (BM-MSCs), or umbilical cord (UC-MSCs). In the present study, the potential of ASCs to stimulate bone formation in composite polymeric scaffolds was discussed and it showed that ASCs have osteogenic ability in vitro. The results also indicated that the ASCs have the potential for rapid growth, easier adipose tissue harvesting with fewer donor site complications and high proliferative capacity. The osteogenic differentiation capacity of ASCs varies due to the culture medium and the addition of factors that can change signaling pathways to increase bone differentiation. Furthermore, gene expression analysis has a significant impact on improving our understanding of the molecular pathways involved in ASCs and, thus, osteogenic differentiation. Adding some drugs, such as dexamethasone, to the biomaterial composite also increases the formation of osteocytes. Combining ASCs with scaffolds synthesized from natural and synthetic polymers seems to be an effective strategy for bone regeneration. Applying exopolysaccharides, such as schizophyllan, chitosan, gelatin, and alginate in composite scaffolds enhances the osteogenesis potential of ASCs in bone tissue regeneration.

Cell-Derived Matrix: Production, Decellularization, and Application of Wound Repair

Chronic nonhealing wounds significantly reduce patients' quality of life and are a major burden on healthcare systems. Over the past few decades, tissue engineering materials have emerged as a viable option for wound healing, with cell-derived extracellular matrix (CDM) showing remarkable results. The CDM's compatibility and resemblance to the natural tissue microenvironment confer distinct advantages to tissue-engineered scaffolds in wound repair. This review summarizes the current processes for CDM preparation, various cell decellularization protocols, and common characterization methods. Furthermore, it discusses the applications of CDM in wound healing, including skin defect and wound repair, angiogenesis, and engineered vessels, and offers perspectives on future developments.

Enhanced bone regeneration in rat calvarial defects through BMP2 release from engineered poly(ethylene glycol) hydrogels

The clinical standard therapy for large bone defects, typically addressed through autograft or allograft donor tissue, faces significant limitations. Tissue engineering offers a promising alternative strategy for the regeneration of substantial bone lesions. In this study, we harnessed poly(ethylene glycol) (PEG)-based hydrogels, optimizing critical parameters including stiffness, incorporation of arginine-glycine-aspartic acid (RGD) cell adhesion motifs, degradability, and the release of BMP2 to promote bone formation. In vitro we demonstrated that human bone marrow derived stromal cell (hBMSC) proliferation and spreading strongly correlates with hydrogel stiffness and adhesion to RGD peptide motifs. Moreover, the incorporation of the osteogenic growth factor BMP2 into the hydrogels enabled sustained release, effectively inducing bone regeneration in encapsulated progenitor cells. When used in vivo to treat calvarial defects in rats, we showed that hydrogels of low and intermediate stiffness optimally facilitated cell migration, proliferation, and differentiation promoting the efficient repair of bone defects. Our comprehensive in vitro and in vivo findings collectively suggest that the developed hydrogels hold significant promise for clinical translation for bone repair and regeneration by delivering sustained and controlled stimuli from active signaling molecules.

In vitro spermatogenesis in artificial testis: current knowledge and clinical implications for male infertility

Men's reproductive health exclusively depends on the appropriate maturation of certain germ cells known as sperm. Certain illnesses, such as Klinefelter syndrome, cryptorchidism, and syndrome of androgen insensitivity or absence of testis maturation in men, resulting in the loss of germ cells and the removal of essential genes on the Y chromosome, can cause non-obstructive azoospermia. According to laboratory research, preserving, proliferating, differentiating, and transplanting spermatogonial stem cells or testicular tissue could be future methods for preserving the fertility of children with cancer and men with azoospermia. Therefore, new advances in stem cell research may lead to promising therapies for treating male infertility. The rate of progression and breakthrough in the area of in vitro spermatogenesis is lower than that of SSC transplantation, but newer methods are also being developed. In this regard, tissue and cell culture, supplements, and 3D scaffolds have opened new horizons in the differentiation of stem cells in vitro, which could improve the outcomes of male infertility. Various 3D methods have been developed to produce cellular aggregates and mimic the organization and function of the testis. The production of an artificial reproductive organ that supports SSCs differentiation will certainly be a main step in male infertility treatment.

Highly resilient and fatigue-resistant poly(4-methyl-ε-caprolactone) porous scaffold fabricated via thiol-yne photo-crosslinking/salt-templating for soft tissue regeneration

Elastomeric scaffolds, individually customized to mimic the structural and mechanical properties of natural tissues have been used for tissue regeneration. In this regard, polyester elastic scaffolds with tunable mechanical properties and exceptional biological properties have been reported to provide mechanical support and structural integrity for tissue repair. Herein, poly(4-methyl-ε-caprolactone) (PMCL) was first double-terminated by alkynylation (PMCL-DY) as a liquid precursor at room temperature. Subsequently, three-dimensional porous scaffolds with custom shapes were fabricated from PMCL-DY via thiol-yne photocrosslinking using a practical salt template method. By manipulating the M_n of the precursor, the modulus of compression of the scaffold was easily adjusted. As evidenced by the complete recovery from 90% compression, the rapid recovery rate of >500 mm min^-1, the extremely low energy loss coefficient of <0.1, and the superior fatigue resistance, the PMCL20-DY porous scaffold was confirmed to harbor excellent elastic properties. In addition, the high resilience of the scaffold was confirmed to endow it with a minimally invasive application potential. In vitro testing revealed that the 3D porous scaffold was biocompatible with rat bone marrow stromal cells (BMSCs), inducing BMSCs to differentiate into chondrogenic cells. In addition, the elastic porous scaffold demonstrated good regenerative efficiency in a 12-week rabbit cartilage defect model. Thus, the novel polyester scaffold with adaptable mechanical properties may have extensive applications in soft tissue regeneration.

Fabrication of elliptically constructed liquid crystalline elastomeric scaffolds for 3D artificial tissues

Inspired by the orientation and the fibrous structure of human muscle tissues, we fabricated preconstructed porous liquid crystalline (LC) scaffolds through a two-step polymerization and salt leaching method. A novel strategy combining the aligning properties of LCs and the ease of processing of elastomers for the preparation of elliptical scaffolds for muscle cell culture was proposed in this research. Different from the other types of scaffolds, our biocompatible LC scaffold that can be implanted into the human body using a supporting unit to improve the mechanical properties compared with those of natural muscle. To evaluate the synthesized scaffolds, in vitro experiments using normal human dermal fibroblast (NHDF) cells and smooth muscle cells from rats were carried out, and the sample cells were cultured on each sample scaffold. Based on the results of long-term culture of NHDF cells on the LC scaffolds, it can be confirmed that all three kinds of LC scaffolds have good biocompatibility and provide enough space for cell growth. The addition of gelatin can significantly enhance the biocompatibility of the synthesized scaffolds. Evaluation of scaffold morphologies on cell growth indicates that the molecular arrangement on the scaffolds can induce the growth direction of smooth muscle cells to a certain extent, thereby increasing the formation of highly ordered arrangement tissues. The population doubling time of NHDF cells on the different scaffolds suggest that gelatin can improve the attachment and growth of cells. Investigation of cell viability on LC scaffolds shows that the original LC scaffolds already possess excellent biocompatibility. Additionally, the average cell viability of smooth muscle cells was above 90%, showing that the LC scaffolds in this research are suitable for application in muscle tissue engineering. Based on the results, the gelatin-coated scaffolds are more conducive to the growth of cells in this research and provide promising candidates for tissue engineering in biomedical fields and research fields.

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.

Discriminant Principal Component Analysis of ToF-SIMS Spectra for Deciphering Compositional Differences of MSC-Secreted Extracellular Matrices

Identifying characteristic extracellular matrix (ECM) variants is a key challenge in mechanistic biology, bioengineering, and medical diagnostics. The reported study demonstrates the potential of time-of-flight secondary ion mass spectrometry (ToF-SIMS) to detect subtle differences between human mesenchymal stromal cell (MSC)-secreted ECM types as induced by exogenous stimulation or emerging pathology. ToF-SIMS spectra of decellularized ECM samples are evaluated by discriminant principal component analysis (DPCA), an advanced multivariate analysis technique, to decipher characteristic compositional features. To establish the approach, signatures of major ECM proteins are determined from samples of pre-defined mixtures. Based on that, sets of ECM variants produced by MSCs in vitro are analyzed. Differences in the content of collagen, fibronectin, and laminin in the ECM resulting from the combined supplementation of MSC cultures with polymers that induce macromolecular crowding and with ascorbic acid are detected from the DPCA of ToF-SIMS spectra. The results are verified by immunostaining. Finally, the comparative ToF-SIMS analysis of ECM produced by MSCs of healthy donors and patients suffering from myelodysplastic syndrome display the potential of the novel methodology to reveal disease-associated alterations of the ECM composition.

Functional acellular matrix for tissue repair

In view of their low immunogenicity, biomimetic internal environment, tissue- and organ-like physicochemical properties, and functionalization potential, decellularized extracellular matrix (dECM) materials attract considerable attention and are widely used in tissue engineering. This review describes the composition of extracellular matrices and their role in stem-cell differentiation, discusses the advantages and disadvantages of existing decellularization techniques, and presents methods for the functionalization and characterization of decellularized scaffolds. In addition, we discuss progress in the use of dECMs for cartilage, skin, nerve, and muscle repair and the transplantation or regeneration of different whole organs (e.g., kidneys, liver, uterus, lungs, and heart), summarize the shortcomings of using dECMs for tissue and organ repair after refunctionalization, and examine the corresponding future prospects. Thus, the present review helps to further systematize the application of functionalized dECMs in tissue/organ transplantation and keep researchers up to date on recent progress in dECM usage.

Effect of Decellularized Extracellular Matrix Bioscaffolds Derived from Fibroblasts on Skin Wound Healing and Remodeling

The mammalian tissue extracellular matrix (ECM) has been used as a scaffold to facilitate the repair and reconstruction of numerous tissues. However, the material properties of decellularized ECM (dECM) from in vitro cell cultures and the effect of these properties on wound remodeling remain unclear. To elucidate its biological activity, we extracted dECM from human lung fibroblasts, fabricated it into a patch, and applied it to a full-thickness skin wound. The fibroblast-derived dECM (fdECM) maintained the content of collagen Ⅰ, collagen Ⅳ, and elastin, and the extraction process did not damage its critical growth factors. The fdECM-conjugated collagen patch (COL-fdECM) facilitated wound contraction and angiogenesis in the proliferative phase when applied to the in vivo full-thickness skin wound model. Moreover, the COL-fdECM treated wound showed increased regeneration of the epidermal barrier function, mature collagen, hair follicle, and subepidermal nerve plexus, suggesting qualitative skin remodeling. This therapeutic efficacy was similarly observed when applied to the diabetic ulcer model. fdECM was shown to help remodel the tissue by regulating fibroblast growth factors, matrix metalloproteinases, and tissue inhibitors of metalloproteinases via the p38 and ERK signaling pathways in an in vitro experiment for understanding the underlying mechanism. These results provide a biological basis for cell-derived ECM as a multi-functional biomaterial applicable to various diseases.

Synergistically Promoting Bone Regeneration by Icariin-Incorporated Porous Microcarriers and Decellularized Extracellular Matrix Derived From Bone Marrow Mesenchymal Stem Cells

Multifunctionality has becoming essential for bone tissue engineering materials, such as drug release. In this study, icariin (ICA)-incorporated poly(glycolide-co-caprolactone) (PGCL) porous microcarriers were fabricated and then coated with decellularized extracellular matrix (dECM) which was derived from bone marrow mesenchymal stem cells (BMSC). The porous structure was generated due to the soluble gelatin within the microcarriers. The initial released ICA in microcarriers regulated osteogenic ECM production by BMSCs during ECM formation. The dECM could further synergistically enhance the migration and osteogenic differentiation of BMSCs together with ICA as indicated by the transwell migration assay, ALP and ARS staining, as well as gene and protein expression. Furthermore, in vivo results also showed that dECM and ICA exhibited excellent synergistic effects in repairing rat calvarial defects. These findings suggest that the porous microcarriers loaded with ICA and dECM coatings have great potential in the field of bone tissue engineering.

Fabrication of a bio-instructive scaffold conferred with a favorable microenvironment allowing for superior implant osseointegration and accelerated in situ vascularized bone regeneration via type H vessel formation

The potential translation of bio-inert polymer scaffolds as bone substitutes is limited by the lack of neovascularization upon implantation and subsequently diminished ingrowth of host bone, most likely resulted from the inability to replicate appropriate endogenous crosstalk between cells. Human umbilical vein endothelial cell-derived decellularized extracellular matrix (HdECM), which contains a collection of angiocrine biomolecules, has recently been demonstrated to mediate endothelial cells(ECs) - osteoprogenitors(OPs) crosstalk. We employed the HdECM to create a PCL (polycaprolactone)/fibrin/HdECM (PFE) hybrid scaffold. We hypothesized PFE scaffold could reconstitute a bio-instructive microenvironment that reintroduces the crosstalk, resulting in vascularized bone regeneration. Following implantation in a rat femoral bone defect, the PFE scaffold demonstrated early vascular infiltration and enhanced bone regeneration by microangiography (μ-AG) and micro-computational tomography (μ-CT). Based on the immunofluorescence studies, PFE mediated the endogenous angiogenesis and osteogenesis with a substantial number of type H vessels and osteoprogenitors. In addition, superior osseointegration was observed by a direct host bone-PCL interface, which was likely attributed to the formation of type H vessels. The bio-instructive microenvironment created by our innovative PFE scaffold made possible superior osseointegration and type H vessel-related bone regeneration. It could become an alternative solution of improving the osseointegration of bone substitutes with the help of induced type H vessels, which could compensate for the inherent biological inertness of synthetic polymers.

Segmentally Demineralized Cortical Bone With Stem Cell-Derived Matrix Promotes Proliferation, Migration and Differentiation of Stem Cells in vitro

A recent study has shown that demineralized cortical bone (DCB) did not improve the healing of tendon-bone interface. Considering that there is a gradient of mineral content in the tendon-bone interface, we designed a segmentally demineralized cortical bone (sDCB) scaffold with two different regions: undemineralized cortical bone section within the scaffold (sDCB-B) and complete demineralized cortical bone section within the scaffold (sDCB-D), to mimic the natural structure of the tendon-bone interface. Furthermore, the extracellular matrix (ECM) from tendon-derived stem cells (TDSCs) was used to modify the sDCB-D region of sDCB to construct a novel scaffold (sDCB-ECM) for enhancing the bioactivity of the sDCB-D. The surface topography, elemental distribution, histological structure, and surface elastic modulus of the scaffold were observed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, histological staining and atomic force microscopy. Cell proliferation of bone marrow mesenchymal stem cells (BMSCs) and TDSCs cultured on scaffolds was evaluated using the Cell Counting kit-8, and cell viability was assessed by Live/Dead cell staining. Cell morphology was detected by fluorescent staining. The ability of the scaffolds to recruit stem cells was tested using transwell migration assay. The expression levels of bone-, cartilage- and tendon-related genes and proteins in stem cells were assessed by the polymerase chain reaction and western blotting. Our results demonstrated that there was a gradient of Ca and P elements in sDCB, and TDSC-derived ECM existed on the surface of the sDCB-D region of sDCB. The sDCB-ECM could promote stem cell proliferation and migration. Moreover, the sDCB-B region of sDCB-ECM could stimulate osteogenic and chondrogenic differentiation of BMSCs, and the sDCB-D-ECM region of sDCB-ECM could stimulate chondrogenic and tenogenic differentiation of TDSCs when compared to DCB. Our study indicated that sDCB-ECM might be a potential bioscaffold to enhance the tendon-bone interface regeneration.

In situ mineralized PLGA/zwitterionic hydrogel composite scaffold enables high-efficiency rhBMP-2 release for critical-sized bone healing

Osteoconductive and osteoinductive scaffolds are highly desirable for functional restoration of large bone defects. Here, we report an in situ mineralized poly(lactic-co-glycolic acid)/poly[2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide hydrogel (PLGA/PSBMA) scaffold as a novel high-efficiency carrier for recombinant human bone morphogenetic protein-2 (rhBMP-2) for bone tissue regeneration. By virtue of the oppositely charged structure, the zwitterionic PSBMA component is able to template well-integrated dense mineralization of calcium phosphate throughout the PLGA/PSBMA scaffold. The high affinity between rhBMP-2 and the mineralized matrix, combined with the capability of the zwitterionic hydrogel to sequester and to enable sustained release of ionic proteins, endows the mineralized PLGA/PSBMA scaffolds with high-efficiency sustained release of rhBMP-2 (only 1.7% release within 35 days), thus enabling robust healing of critical-sized (5 mm) nonunion calvarial defects in rats at an ultralow dosage of rhBMP-2 (150 ng per scaffold), at which level successful healing of critical-sized bone defects has never been reported. These findings show that the mineralized PLGA/PSBMA scaffold is promising for bone defect repair.

Carbon nanotube-reinforced cell-derived matrix-silk fibroin hierarchical scaffolds for bone tissue engineering applications

In bone tissue engineering, the development of advanced biomimetic scaffolds has led to the quest for biomotifs in scaffold design that better recreate the bone matrix structure and composition and hierarchy at different length scales. In this study, an advanced hierarchical scaffold consisting of silk fibroin combined with a decellularized cell-derived extracellular matrix and reinforced with carbon nanotubes was developed. The goal of the carbon nanotube-reinforced cell-derived matrix-silk fibroin hierarchical scaffolds is to harvest the individual properties of their constituents to introduce hierarchical capacity in order to improve standard silk fibroin scaffolds. The scaffolds were fabricated using enzymatic cross-linking, freeze modeling, and decellularization methods. The developed scaffolds were assessed for the pore structure and mechanical properties showing satisfying results to be used in bone regeneration. The developed carbon nanotube-reinforced cell-derived matrix-silk fibroin hierarchical scaffolds were shown to be bioactive in vitro and expressed no hemolytic effect. Furthermore, cellular in vitro studies on human adipose-derived stem cells (hASCs) showed that scaffolds supported cell proliferation. The hASCs seeded onto these scaffolds evidenced similar metabolic activity to standard silk fibroin scaffolds but increased ALP activity. The histological staining showed cell infiltration into the scaffolds and visible collagen production. The expression of several osteogenic markers was investigated, further supporting the osteogenic potential of the developed carbon nanotube-reinforced cell-derived matrix-silk fibroin hierarchical scaffolds. The hemolytic assay demonstrated the hemocompatibility of the hierarchical scaffolds. Overall, the carbon nanotube-reinforced cell-derived matrix-silk fibroin hierarchical scaffolds presented the required architecture for bone tissue engineering applications.

The Role of Growth Factors in Bioactive Coatings

With increasing obesity and an ageing population, health complications are also on the rise, such as the need to replace a joint with an artificial one. In both humans and animals, the integration of the implant is crucial, and bioactive coatings play an important role in bone tissue engineering. Since bone tissue engineering is about designing an implant that maximally mimics natural bone and is accepted by the tissue, the search for optimal materials and therapeutic agents and their concentrations is increasing. The incorporation of growth factors (GFs) in a bioactive coating represents a novel approach in bone tissue engineering, in which osteoinduction is enhanced in order to create the optimal conditions for the bone healing process, which crucially affects implant fixation. For the application of GFs in coatings and their implementation in clinical practice, factors such as the choice of one or more GFs, their concentration, the coating material, the method of incorporation, and the implant material must be considered to achieve the desired controlled release. Therefore, the avoidance of revision surgery also depends on the success of the design of the most appropriate bioactive coating. This overview considers the integration of the most common GFs that have been investigated in in vitro and in vivo studies, as well as in human clinical trials, with the aim of applying them in bioactive coatings. An overview of the main therapeutic agents that can stimulate cells to express the GFs necessary for bone tissue development is also provided. The main objective is to present the advantages and disadvantages of the GFs that have shown promise for inclusion in bioactive coatings according to the results of numerous studies.

Controlled delivery of bone morphogenic protein-2-related peptide from mineralised extracellular matrix-based scaffold induces bone regeneration

Ideal bone tissue engineering scaffolds composed of extracellular matrix (ECM) require excellent osteoconductive ability to imitate the bone environment. We developed a mineralised tissue-derived ECM-modified true bone ceramic (TBC) scaffold for the delivery of aspartic acid-modified bone morphogenic protein-2 (BMP-2) peptide (P28) and assessed its osteogenic capacity. Decellularized ECM from porcine small intestinal submucosa (SIS) was coated onto the surface of TBC, followed by mineralisation modification (mSIS/TBC). P28 was subsequently immobilised onto the scaffolds in the absence of a crosslinker. The alkaline phosphatase activity and other osteogenic differentiation marker results showed that osteogenesis of the P28/mSIS/TBC scaffolds was significantly greater than that of the TBC and mSIS/TBC groups. In addition, to examine the osteoconductive capability of this system in vivo, we established a rat calvarial bone defect model and evaluated the new bone area and new blood vessel density. Histological observation showed that P28/mSIS/TBC exhibited favourable bone regeneration efficacy. This study proposes the use of mSIS/TBC loaded with P28 as a promising osteogenic scaffold for bone tissue engineering applications.

Human nasal septal chondrocytes (NSCs) preconditioned on NSC-derived matrix improve their chondrogenic potential

Background

Extracellular matrix (ECM) has a profound effect on cell behaviors. In this study, we prepare a decellularized human nasal septal chondrocyte (NSC)-derived ECM (CHDM), as a natural (N-CHDM) or soluble form (S-CHDM), and investigate their impact on NSCs differentiation.

Methods

N-CHDM, S-CHDM were obtained from NSC. To evaluate function of NSC cultured on each substrate, gene expression using chondrogenic marker, and chondrogenic protein expression were tested. Preconditioned NSCs-loaded scaffolds were transplanted in nude mice for 3 weeks and analyzed.

Results

When cultivated on each substrate, NSCs exhibited similar cell spread area but showed distinct morphology on N-CHDM with significantly lower cell circularity. They were highly proliferative on N-CHDM than S-CHDM and tissue culture plastic (TCP), and showed more improved cell differentiation, as assessed via chondrogenic marker (Col2, Sox9, and Aggrecan) expression and immunofluorescence of COL II. We also investigated the effect of NSCs preconditioning on three different 2D substrates while NSCs were isolated from those substrates, subsequently transferred to 3D mesh scaffold, then cultivated them in vitro or transplanted in vivo. The number of cells in the scaffolds was similar to each other at 5 days but cell differentiation was notably better with NSCs preconditioned on N-CHDM, as assessed via real-time q-PCR, Western blot, and immunofluorescence. Moreover, when those NSCs-loaded polymer scaffolds were transplanted subcutaneously in nude mice for 3 weeks and analyzed, the NSCs preconditioned on the N-CHDM showed significantly advanced cell retention in the scaffold, more cells with a chondrocyte lacunae structure, and larger production of cartilage ECM (COL II, glycosaminoglycan).

Conclusions

Taken together, a natural form of decellularized ECM, N-CHDM would present an advanced chondrogenic potential over a reformulated ECM (S-CHDM) or TCP substrate, suggesting that N-CHDM may hold more diverse signaling cues, not just limited to ECM component.

Hierarchically Demineralized Cortical Bone Combined With Stem Cell-Derived Extracellular Matrix for Regeneration of the Tendon-Bone Interface

BACKGROUND

Poor healing of the tendon-bone interface after rotator cuff repair is one of the main causes of surgical failure. Previous studies demonstrated that demineralized cortical bone (DCB) could improve healing of the enthesis.

PURPOSE

To evaluate the outcomes of hierarchically demineralized cortical bone (hDCB) coated with stem cell-derived extracellular matrix (hDCB-ECM) in the repair of the rotator cuff in a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Tendon-derived stem cells (TDSCs) were isolated, cultured, and identified. Then, hDCB was prepared by the graded demineralization procedure. Finally, hDCB-ECM was fabricated via 2-week cell culture and decellularization, and the morphologic features and biochemical compositions of the hDCB-ECM were evaluated. A total of 24 rabbits (48 samples) were randomly divided into 4 groups: control, DCB, hDCB, and hDCB-ECM. All rabbits underwent bilateral detachment of the infraspinatus tendon, and the tendon-bone interface was repaired with or without scaffolds. After surgery, 8 rabbits were assessed by immunofluorescence staining at 2 weeks, and the others were assessed by micro-computed tomography (CT) examination, immunohistochemical staining, histological staining, and biomechanical testing at 12 weeks.

RESULTS

TDSCs were identified to have universal stem cell characteristics including cell markers, clonogenicity, and multilineage differentiation. The hDCB-ECM contained 3 components (bone, partial DCB, and DCB coated with ECM) with a gradient of calcium and phosphorus elements, and the ECM had stromal cell-derived factor 1, biglycan, and fibromodulin. Macroscopic observations demonstrated the absence of infection and rupture around the enthesis. The results of immunofluorescence staining showed that hDCB-ECM promoted stromal cell recruitment. Results of micro-CT analysis, immunohistochemical staining, and histological staining showed that hDCB-ECM enhanced bone and fibrocartilage formation at the tendon-bone interface. Biomechanical analysis showed that the hDCB-ECM group had higher ultimate tensile stress and Young modulus than the DCB group.

CONCLUSION

The administration of hDCB-ECM promoted healing of the tendon-bone interface.

CLINICAL RELEVANCE

hDCB-ECM could provide useful information for the design of scaffolds to repair the tendon-bone interface, and further studies are needed to determine its effectiveness.

Effect of cyclic mechanical loading on immunoinflammatory microenvironment in biofabricating hydroxyapatite scaffold for bone regeneration

It has been proven that the mechanical microenvironment can impact the differentiation of mesenchymal stem cells (MSCs). However, the effect of mechanical stimuli in biofabricating hydroxyapatite scaffolds on the inflammatory response of MSCs remains unclear. This study aimed to investigate the effect of mechanical loading on the inflammatory response of MSCs seeded on scaffolds. Cyclic mechanical loading was applied to biofabricate the cell-scaffold composite for 15 min/day over 7, 14, or 21 days. At the predetermined time points, culture supernatant was collected for inflammatory mediator detection, and gene expression was analyzed by qRT-PCR. The results showed that the expression of inflammatory mediators (IL1B and IL8) was downregulated (p < 0.05) and the expression of ALP (p < 0.01) and COL1A1 (p < 0.05) was upregulated under mechanical loading. The cell-scaffold composites biofabricated with or without mechanical loading were freeze-dried to prepare extracellular matrix-based scaffolds (ECM-based scaffolds). Murine macrophages were seeded on the ECM-based scaffolds to evaluate their polarization. The ECM-based scaffolds that were biofabricated with mechanical loading before freeze-drying enhanced the expression of M2 polarization-related biomarkers (Arginase 1 and Mrc1, p < 0.05) of macrophages in vitro and increased bone volume/total volume ratio in vivo. Overall, these findings demonstrated that mechanical loading could dually modulate the inflammatory responses and osteogenic differentiation of MSCs. Besides, the ECM-based scaffolds that were biofabricated with mechanical loading before freeze-drying facilitated the M2 polarization of macrophages in vitro and bone regeneration in vivo. Mechanical loading may be a promising biofabrication strategy for bone biomaterials.

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Compressive mechanical loading is applied to biofabricate the MSCs-hydroxyapatite composites for bone regeneration.

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Mechanical loading can modulate the inflammatory responses and osteogenic differentiation of MSCs seeded on scaffold.

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ECM-based scaffolds from initially loading biofabrication facilitated the M2 polarization of macrophages and bone repair.

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Mechanical loading may be a promising biofabrication strategy for bone biomaterials.

Anterior cruciate ligament reconstruction in a rabbit model using a silk-collagen scaffold modified by hydroxyapatite at both ends: a histological and biomechanical study

Background

To investigate osteointegration at the graft-bone interface and the prevention of osteoarthritis after anterior cruciate ligament (ACL) reconstruction using a silk-collagen scaffold with both ends modified by hydroxyapatite (HA) in a rabbit model.

Methods

The HA/silk-collagen scaffold was fabricated using a degummed, knitted silk scaffold, collagen I matrix, and simulated body fluid (SBF). The HA/silk-collagen scaffold was rolled up to make a graft for replacing the native ACL in the experimental group (HA group), and the silk-collagen scaffold was used in the control (S group). All specimens were harvested at 16 weeks postoperatively to evaluate graft-bone healing and osteoarthritis prevention.

Results

Histological staining revealed the massive formation of more mature bone at the tendon-bone interface, and immunohistochemistry staining revealed more collagen I and osteocalcin deposition in the HA group than in the S group. Higher signals indicating more bone mineral formation were detected in the HA group than in the S group, which was consistent with the results of biomechanical testing. Better osteoarthritis prevention was also observed in the HA group, indicating a more stable knee joint in the HA group than in the S group.

Conclusion

The HA/silk-collagen scaffold promotes osteointegration at the tendon-bone interface after ACL reconstruction and has great potential for clinical applications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02281-0.

Stem-cell-derived ECM sheet-implant complexes for enhancing osseointegration

Numerous treatment methods have been developed to modify the surface of dental implants to improve cell migration and proliferation, removal torque, and osseointegration. Recent studies have constructed cell sheet-implant complexes with enhanced osteogenic capabilities. However, these complexes have some limitations, such as requirements for complex preparation processes, cell vitality maintenance, strict preservation conditions, and the induction of immunogenicity. Extracellular matrix (ECM) sheets without cells may be a more desirable material. To date, the effect of ECM sheets on implant osseointegration has not been reported. In this study, we fabricated ECM sheet-implant complexes through the combination of rat bone marrow mesenchymal stem cell (BMSC)-derived ECM sheets with sandblasted, large-grit, acid-etched (SLA) implants. These complexes were characterized by light microscopy, scanning electron microscopy (SEM), and immunofluorescence (IF) assays. The adhesion, proliferation, and osteogenic differentiation of BMSCs cultured on ECM sheets were detected in vitro. Then, the ECM sheet-implant complexes were transplanted into the metaphysis of the tibias of rats to evaluate the implant osseointegration in vivo. The results showed that ECM sheets were successfully constructed and showed significantly improved adhesion and proliferation. BMSCs cultured on ECM sheets upregulated the expression levels of the osteogenic-related genes alkaline phosphatase (ALP), bone morphogenetic protein 2 (BMP2), and runt-related transcription factor 2 (Runx2) compared to controls. In vivo, ECM sheet-implant complexes demonstrated superior new bone formation. Our findings proved that the BMSC-derived ECM sheets promoted osseointegration in vitro and in vivo. The current study indicated that the ECM sheet could be an ideal tissue engineering material, and ECM sheet-implant complexes could provide a strategy with low immunogenicity and easy storage and transportation. This research provides a novel strategy for the development of implant surface modification approaches.

Cell-Derived Extracellular Matrix for Tissue Engineering and Regenerative Medicine

Cell-derived extracellular matrices (CD-ECMs) captured increasing attention since the first studies in the 1980s. The biological resemblance of CD-ECMs to their in vivo counterparts and natural complexity provide them with a prevailing bioactivity. CD-ECMs offer the opportunity to produce microenvironments with costumizable biological and biophysical properties in a controlled setting. As a result, CD-ECMs can improve cellular functions such as stemness or be employed as a platform to study cellular niches in health and disease. Either on their own or integrated with other materials, CD-ECMs can also be utilized as biomaterials to engineer tissues de novo or facilitate endogenous healing and regeneration. This review provides a brief overview over the methodologies used to facilitate CD-ECM deposition and manufacturing. It explores the versatile uses of CD-ECM in fundamental research and therapeutic approaches, while highlighting innovative strategies. Furthermore, current challenges are identified and it is accentuated that advancements in methodologies, as well as innovative interdisciplinary approaches are needed to take CD-ECM-based research to the next level.

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

Extracellular matrix (ECM) with mimetic tissue niches was attractive to facilitate tissue regeneration in situ via recruitment of endogenous cells and stimulation of self-healing process. However, how to engineer the complicate tissue specific ECM with unique matrisome in vitro was a challenge of ECM-based biomaterials in tissue engineering and regenerative medicine. Here, we introduced coculture system to engineer bone mimetic ECM niche guided by cell-cell communication. In the cocultures, fibroblasts promoted osteogenic differentiation of osteoblasts via extracellular vesicles. The generated ECM (MN-ECM) displayed a unique appearance of morphology and biological components. The advantages of MN-ECM were demonstrated with promotion of multiple cellular behaviors (proliferation, adhesion and osteogenic mineralization) in vitro and bone regeneration in vivo. Moreover, proteomic analysis was used to clarify the molecular mechanism of MN-ECM, which revealed a specific matrisome signature. The present study provides a novel strategy to generate ECM with tissue mimetic niches via cell-cell communication in a coculture system, which forwards the development of tissue-bioactive ECM engineering along with deepening the understanding of ECM niches regulated by cells for bone tissue engineering.

Learning from BMPs and their biophysical extracellular matrix microenvironment for biomaterial design

It is nowadays well-accepted that the extracellular matrix (ECM) is not a simple reservoir for growth factors but is an organization center of their biological activity. In this review, we focus on the ability of the ECM to regulate the biological activity of BMPs. In particular, we survey the role of the ECM components, notably the glycosaminoglycans and fibrillary ECM proteins, which can be promoters or repressors of the biological activities mediated by the BMPs. We examine how a process called mechano-transduction induced by the ECM can affect BMP signaling, including BMP internalization by the cells. We also focus on the spatio-temporal regulation of the BMPs, including their release from the ECM, which enables to modulate their spatial localization as well as their local concentration. We highlight how biomaterials can recapitulate some aspects of the BMPs/ECM interactions and help to answer fundamental questions to reveal previously unknown molecular mechanisms. Finally, the design of new biomaterials inspired by the ECM to better present BMPs is discussed, and their use for a more efficient bone regeneration in vivo is also highlighted.

Magnetic-Field-Assisted Cellular Osteogenic Differentiation on Magnetic Zinc Ferrite Coatings via MEK/ERK Signaling Pathways

Combining an external stimulus and stimuli-responsive biomaterials can regulate cellular behaviors. In this paper, a magneto-responsive zinc ferrite (ZnFe₂O₄) coating was designed to gain insight into the preosteoblasts behaviors and osteogenic differentiation mechanism under a static magnetic field (SMF). ZnFe₂O₄ coatings with distinct magnetization (low, medium, and high magnetizations) were prepared by being annealed at different temperatures. Cellular biology experiments indicated that all ZnFe₂O₄ coatings with the assistance of SMF could promote the early proliferation (3 days) and osteogenic differentiation of MC3T3-E1 cells. Among different ZnFe₂O₄ samples, low and medium magnetization of ZnFe₂O₄ showed a higher osteogenesis-related gene expression (Runx2, Col-I, OCN) than that of high magnetization ZnFe₂O₄ under SMF, while cellular adhesion and proliferation cultured on different ZnFe₂O₄ samples presented insignificant differences. Molecular biology tests showed that the combination of ferromagnetic ZnFe₂O₄ and SMF could significantly improve the expression level of α2β1 integrin and p-ERK. However, the addition of the inhibitor U0126 sharply reduced the expression level of p-ERK, which indicated that α2β1 integrin-mediated MEK/ERK signaling pathways play a key role in SMF-assisted cellular osteogenic differentiation over ZnFe₂O₄ coatings. This work provides an attractive strategy to enhance cellular osteogenic differentiation in a remote-control way, which exhibited enormous potential in the field of bone tissue repair and regeneration.

Osteogenic-differentiated mesenchymal stem cell-secreted extracellular matrix as a bone morphogenetic protein-2 delivery system for ectopic bone formation

While human bone morphogenetic protein-2 (BMP-2) is a promising growth factor for bone regeneration, a major challenge in biomedical applications is finding an optimal carrier for its delivery at the site of injury. Because of their natural affinities for growth factors (including BMP-2) as well as their role in instructing cell function, cultured cell-derived extracellular matrices (ECM) are of special interest. We hereby hypothesized that a "bony matrix" containing mineralized, osteogenic ECM is a potential efficacious carrier of BMP-2 for promoting bone formation and, therefore, compared the efficacy of the decellularized ECM derived from osteogenic-differentiated human mesenchymal stem cells (hMSCs) to the one obtained from ECM from undifferentiated hMSCs. Our results provided evidence that both ECMs can bind BMP-2 and promote bone formation when implanted ectopically in mice. The osteoinductive potential of BMP-2, however, was greater when loaded within an osteogenic MSC-derived ECM; this outcome was correlated with higher sequestration capacity of BMP-2 over time in vivo. Interestingly, although the BMP-2 mainly bound onto the mineral crystals contained within the osteogenic MSC derived-ECM, these mineral components were not involved in the observed higher osteoinductivity, suggesting that the organic components were the critical components for the matrix efficacy as BMP-2 carrier.

Innovative Options for Bone Metastasis Treatment: An Extensive Analysis on Biomaterials-Based Strategies for Orthopedic Surgeons

Bone is the third most frequent site of metastasis, with a particular incidence in breast and prostate cancer patients. For example, almost 70% of breast cancer patients develop several bone metastases in the late stage of the disease. Bone metastases are a challenge for clinicians and a burden for patients because they frequently cause pain and can lead to fractures. Unfortunately, current therapeutic options are in most cases only palliative and, although not curative, surgery remains the gold standard for bone metastasis treatment. Surgical intervention mostly provides the replacement of the affected bone with a bioimplant, which can be made by materials of different origins and designed through several techniques that have evolved throughout the years simultaneously with clinical needs. Several scientists and clinicians have worked to develop biomaterials with potentially successful biological and mechanical features, however, only a few of them have actually reached the scope. In this review, we extensively analyze currently available biomaterials-based strategies focusing on the newest and most innovative ideas while aiming to highlight what should be considered both a reliable choice for orthopedic surgeons and a future definitive and curative option for bone metastasis and cancer patients.

Polymeric nanofibrous scaffolds laden with cell-derived extracellular matrix for bone regeneration

Bone tissue engineering aims to alleviate the shortage of available autograft material and the biological/mechanical incompatibility of allografts through fabrication of bioactive synthetic bone graft substitutes. However, these substitute grafting materials have insufficient biological potency that limits their clinical efficacy in regenerating large defects. Extracellular matrix, a natural tissue scaffold laden with biochemical and structural cues regulating cell adhesion and tissue morphogenesis, may be a versatile supplement that can extend its biological functionality to synthetic grafts. Embedding decellularized extracellular matrix (dECM) into synthetic polymers offers a promising strategy to enhance cellular response to synthetic materials, mitigate physical and mechanical limitations of dECMs, and improve clinical utility of synthetic bone grafts. Enriched with dECM biochemical cues, synthetic polymers can be readily fabricated into complex biocomposite grafts that mimic bone structure and stimulate endogenous cells to regenerate bone. In this study, cell-derived dECMs from osteoblast and endothelial cells were incorporated into polycaprolactone (PCL) solutions for electrospinning dual-layer nanofibrous scaffolds with osteogenic and vascular cues. The study examined the bioactivity of dECM scaffolds in osteoblast cultures for cell number, mineral deposits, and osteogenic markers, as well as regeneration of cortical bone defect in a rat femur. Scaffolds with osteoblast dECM had a significantly robust osteoblast proliferation, Alizarin Red staining/concentration, and osteopontin-positive extracellular deposits. Implanted scaffolds increased bone growth in femoral defects, and constructs with both osteogenic and vascular cues significantly improved cortical width. These findings demonstrate the potential to fabricate tailored biomimetic grafts with dECM cues and fibrous architecture for bone applications.

The Bone Extracellular Matrix in Bone Formation and Regeneration

Bone regeneration repairs bone tissue lost due to trauma, fractures, and tumors, or absent due to congenital disorders. The extracellular matrix (ECM) is an intricate dynamic bio-environment with precisely regulated mechanical and biochemical properties. In bone, ECMs are involved in regulating cell adhesion, proliferation, and responses to growth factors, differentiation, and ultimately, the functional characteristics of the mature bone. Bone ECM can induce the production of new bone by osteoblast-lineage cells, such as MSCs, osteoblasts, and osteocytes and the absorption of bone by osteoclasts. With the rapid development of bone regenerative medicine, the osteoinductive, osteoconductive, and osteogenic potential of ECM-based scaffolds has attracted increasing attention. ECM-based scaffolds for bone tissue engineering can be divided into two types, that is, ECM-modified biomaterial scaffold and decellularized ECM scaffold. Tissue engineering strategies that utilize the functional ECM are superior at guiding the formation of specific tissues at the implantation site. In this review, we provide an overview of the function of various types of bone ECMs in bone tissue and their regulation roles in the behaviors of osteoblast-lineage cells and osteoclasts. We also summarize the application of bone ECM in bone repair and regeneration. A better understanding of the role of bone ECM in guiding cellular behavior and tissue function is essential for its future applications in bone repair and regenerative medicine.

Effect of the nano/microscale structure of biomaterial scaffolds on bone regeneration

Natural bone is a mineralized biological material, which serves a supportive and protective framework for the body, stores minerals for metabolism, and produces blood cells nourishing the body. Normally, bone has an innate capacity to heal from damage. However, massive bone defects due to traumatic injury, tumor resection, or congenital diseases pose a great challenge to reconstructive surgery. Scaffold-based tissue engineering (TE) is a promising strategy for bone regenerative medicine, because biomaterial scaffolds show advanced mechanical properties and a good degradation profile, as well as the feasibility of controlled release of growth and differentiation factors or immobilizing them on the material surface. Additionally, the defined structure of biomaterial scaffolds, as a kind of mechanical cue, can influence cell behaviors, modulate local microenvironment and control key features at the molecular and cellular levels. Recently, nano/micro-assisted regenerative medicine becomes a promising application of TE for the reconstruction of bone defects. For this reason, it is necessary for us to have in-depth knowledge of the development of novel nano/micro-based biomaterial scaffolds. Thus, we herein review the hierarchical structure of bone, and the potential application of nano/micro technologies to guide the design of novel biomaterial structures for bone repair and regeneration.

Extracellular matrix decorated polycaprolactone scaffolds for improved mesenchymal stem/stromal cell osteogenesis towards a patient-tailored bone tissue engineering approach

The clinical demand for tissue-engineered bone is growing due to the increase of non-union fractures and delayed healing in an aging population. Herein, we present a method combining additive manufacturing (AM) techniques with cell-derived extracellular matrix (ECM) to generate structurally well-defined bioactive scaffolds for bone tissue engineering (BTE). In this work, highly porous three-dimensional polycaprolactone (PCL) scaffolds with desired size and architecture were fabricated by fused deposition modeling and subsequently decorated with human mesenchymal stem/stromal cell (MSC)-derived ECM produced in situ. The successful deposition of MSC-derived ECM onto PCL scaffolds (PCL-MSC ECM) was confirmed after decellularization using scanning electron microscopy, elemental analysis, and immunofluorescence. The presence of cell-derived ECM within the PCL scaffolds significantly enhanced MSC attachment and proliferation, with and without osteogenic supplementation. Additionally, under osteogenic induction, PCL-MSC ECM scaffolds promoted significantly higher calcium deposition and elevated relative expression of bone-specific genes, particularly the gene encoding osteopontin, when compared to pristine scaffolds. Overall, our results demonstrated the favorable effects of combining MSC-derived ECM and AM-based scaffolds on the osteogenic differentiation of MSC, resulting from a closer mimicry of the native bone niche. This strategy is highly promising for the development of novel personalized BTE approaches enabling the fabrication of patient defect-tailored scaffolds with enhanced biological performance and osteoinductive properties.

Topography induced stiffness alteration of stem cells influences osteogenic differentiation

Topography-driven alterations to single cell stiffness rather than alterations in cell morphology, is the underlying driver for influencing cell biological processes, particularly stem cell differentiation.

Effects of a Coating of Nano Silicon Nitride on Porous Polyetheretherketone on Behaviors of MC3T3-E1 Cells in Vitro and Vascularization and Osteogenesis in Vivo

To improve the bioperformances of porous polyetheretherketone (PPK) for bone repair, silicon nitride-coated PPK (CSNPPK) was prepared by a method of suspension coating and melt binding. The results revealed that, as compared with PPK, the surface roughness, compressive strength, and water absorption of CSNPPK increased, while the pore size and porosity of CSNPPK exhibited no obvious changes. In addition, the cellular responses (including attachment, proliferation, and differentiation as well as osteogenically related gene expressions) of the MC3T3-E1 cells to CSNPPK were remarkably promoted compared with PPK and dense polyetheretherketone in vitro. Moreover, in the model of rabbit femoral condyle defects, the results of micro computed tomography and histological and mechanical evaluation revealed that the ingrowth of new vessels and bone tissues into CSNPPK was significantly greater than that into PPK in vivo. Furthermore, the load-displacement and push-out loads for CSNPPK with bone tissues were higher than for PPK, indicating good osseointegration. In short, CSNPPK not only promoted vascularization but also enhanced osteogenesis as well as osseointegration in vivo. Therefore, it can be suggested that CSNPPK with good biocompatibility, osteogenic activity, and vascularization might be a promising candidate as an implant for bone substitute and repair.

Acellular polycaprolactone scaffolds laden with fibroblast/endothelial cell-derived extracellular matrix for bone regeneration

Inconsistencies in graft osteoconduction and osteoinduction present a clinical challenge in regeneration of large bone defects. Deposition of decellularized extracellular matrix (dECM) on tissue engineered scaffolds offers an alternative approach that can enhance these properties by mimicking bone's molecular complexity and direct infiltrating cells to repair damaged bone. However, dECMs derived from homogenous cell populations do not adequately simulate the heterogeneous and vascularized microenvironment of the bone. In this study, successive culture and decellularization of fibroblasts and endothelial cells (ECs) grown on polycaprolactone microfibers was used to develop a bioactive scaffold with heterogeneous dECM mimicking endothelial basement membrane. These scaffolds had greater amount of protein and minimally increased nucleic acid content than scaffolds with homogenous culture dECM. Coomassie Blue and antibody staining revealed extensive tube formation by ECs on fibroblast dECM. Fibroblast/endothelial dECM significantly enhanced osteoblast attachment, alkaline phosphatase activity, and osteocalcin- and osteopontin-positive extracellular mineral deposits. We demonstrated that the osteoconduction of dECMs can be tailored with the appropriate combination of cells to accelerate osteoblast mineral secretion. The overall concept can be expanded to generate increasingly more complex tissue constructs for regeneration of bone defects and other vascularized tissues.

Betaine alleviates alcohol-induced osteonecrosis of the femoral head via mTOR signaling pathway regulation

Osteonecrosis of the femoral head (ONFH) is usually caused by chronic and excessive alcohol dependency, and this condition largely suppresses the osteogenic differentiation of bone mesenchymal stem cells (BMSCs). As a trimethyl derivative of glycine, betaine is an important human nutrient that regulates a series of vital biological processes, including oxidative stress, inflammatory responses, osteoblast differentiation and cellular apoptosis. However, no study has investigated the role of betaine in alcohol-induced ONFH. In this study, we hypothesized that betaine might have protective effects on ethanol-treated BMSCs and decrease the morbidity of alcohol-induced ONFH in a rat model. In vitro, we found that ethanol significantly downregulated the expression of osteocalcin (OCN), collagen 1 (COL1) and RUNX2 via activating the mammalian target of rapamycin (mTOR) signaling cascade. However, the inhibitory effects were rescued by betaine co-treatment at concentrations of 1 mM and 10 mM. In vivo, the typical ONFH pathological changes in a rat model of alcohol-induced ONFH were investigated by using multiple methods, including hematoxylin-eosin staining, micro-CT scans, TdT-mediated dUTP nick end labeling (TUNEL) assays and immunohistochemical staining for OCN and COL1. Osteonecrotic lesions of the femoral head could be alleviated by betaine as evidenced by significant histological and radiological improvements. Collectively, betaine plays a protective role against ethanol-induced suppression of osteogenesis and mineralization of hBMSCs and is thus a potential pharmacotherapy for alcohol-induced ONFH in vivo.

A comparative study on agarose acetate and PDLLA scaffold for rabbit femur defect regeneration

The development of degradable polymer scaffolds is a key issue in bone regeneration. Poly(D, L-lactide) (PDLLA) and its derivatives have usually been applied to the construction of degradable scaffolds, but these scaffolds had problems with acidic degradation products and quick loss of mechanic strength during the later degradation, which usually led to scaffold collapse and cavity formation because of the slower rate of bone regeneration. In the present paper, a polysaccharide derivative, agarose acetate (AGA), was synthesized and a novel porous AGA scaffold was successfully developed through a salt-leaching process. The AGA scaffold had over 90% porosity without swelling in water, and compared to collapse and acidic products of PDLLA scaffold during degradation, the AGA scaffold maintained a stable morphology and a nearly neutral pH value over 18 months' degradation in PBS. A bone mesenchymal stem cells (BMSCs) adhesion and proliferation experiment showed that more cells adhered to the AGA scaffold than to the PDLLA scaffold. A subcutaneous implant test showed that the AGA scaffold slowly degraded and did not cause an inflammatory response surrounding the implantation lesion site. AGA scaffold was implanted into femur defects in New Zealand white rabbits to test its in vivo performance. Results indicated that the AGA scaffold accelerated the process of bone regeneration compared to the PDLLA group and, with time, new bone was formed from the margin toward the center of the scaffolds, and the scaffold left in place retained its porous structure without collapsing. Meanwhile, the AGA scaffold showed a low degradation rate and kept its shape during the in vivo degradation compared to the PDLLA scaffold. This performance could have the benefit of integrated regenerative bone being formed instead of cavities due to the quickly degraded scaffold disappearing. These results demonstrate that the AGA scaffold has significant potential in bone regeneration applications.

Stretchable ECM Patch Enhances Stem Cell Delivery for Post-MI Cardiovascular Repair

Current cell-based therapies administered after myocardial infarction (MI) show limited efficacy due to subpar cell retention in a dynamically beating heart. In particular, cardiac patches generally provide a cursory level of cell attachment due to the lack of an adequate microenvironment. From this perspective, decellularized cell-derived ECM (CDM) is attractive in its recapitulation of a natural biophysical environment for cells. Unfortunately, its weak physical property renders it difficult to retain in its original form, limiting its full potential. Here, a novel strategy to peel CDM off from its underlying substrate is proposed. By physically stamping it onto a polyvinyl alcohol hydrogel, the resulting stretchable extracellular matrix (ECM) membrane preserves the natural microenvironment of CDM, thereby conferring a biological interface to a viscoelastic membrane. Its various mechanical and biological properties are characterized and its capacity to improve cardiomyocyte functionality is demonstrated. Finally, evidence of enhanced stem cell delivery using the stretchable ECM membrane is presented, which leads to improved cardiac remodeling in a rat MI model. A new class of material based on natural CDM is envisioned for the enhanced delivery of cells and growth factors that have a known affinity with ECM.

Tunable Hybrid Biopolymeric Hydrogel Scaffolds Based on Atomic Force Microscopy Characterizations for Tissue Engineering

Developing adequate biomaterials to engineer cell-scaffold interactions has become a promising way for physically regulating the biological behaviors of cells in the field of tissue engineering. Biopolymeric hydrogels have shown great merits as cellular scaffolds due to their biocompatible and biodegradable characteristics. In particular, the advent of atomic force microscopy (AFM) provides a powerful tool for characterizing native specimens at the micro/nanoscale, but utilizing AFM to investigate the detailed structures and properties of hydrogel scaffolds has been still scarce. In this paper, hybrid natural biopolymers are used to form hydrogel scaffolds which exhibit tunable structural and mechanical properties characterized by AFM peak force tapping imaging, and the applications of the formed hydrogel scaffolds in tissue engineering are studied. AFM morphological images showed that the cross-linking reactions of sodium alginate and gum arabic via calcium cations yielded the porous hydrogel scaffolds. By altering the component ratios, AFM mechanical images showed that the porous and mechanical properties (Young's modulus and adhesion force) of the hydrogel scaffolds were tunable. Next, the nanoscale structural and mechanical dynamics of the fabricated hydrogel scaffolds during the degradation process were revealed by AFM peak force tapping imaging. The experimental results on three different types of cells showed that the fabricated hydrogel scaffolds facilitate the formation of cellular spheroids. The research provides a novel idea to design tunable hydrogel scaffolds based on AFM characterizations for investigating cell-scaffold interactions, which will have potential impacts on tissue engineering.