A nano-scaled and multi-layered recombinant fibronectin/cadherin chimera composite selectively concentrates osteogenesis-related cells and factors to aid bone repair

Microfluidic synthesis of fibronectin-coated polydopamine nanocomplexes for self-supplementing tumor microenvironment regulation and MR imaging-guided chemo-chemodynamic-immune therapy

Development of nanomedicines to overcome the hindrances of tumor microenvironment (TME) for tumor theranostics with alleviated side effects remains challenging. We report here a microfluidic synthesis of artesunate (ART)-loaded polydopamine (PDA)/iron (Fe) nanocomplexes (NCs) coated with fibronectin (FN). The created multifunctional Fe-PDA@ART/FN NCs (FDRF NCs) with a mean size of 161.0 ​nm exhibit desired colloidal stability, monodispersity, r₁ relaxivity (4.96 ​mM^-1s^-1), and biocompatibility. The co-delivery of the Fe²⁺ and ART enables enhanced chemodynamic therapy (CDT) through improved intracellular reactive oxygen species generation via a cycling reaction between Fe³⁺ and Fe²⁺ caused by the Fe³⁺-mediated glutathione oxidation and Fe²⁺-mediated ART reduction/Fenton reaction for self-supplementing TME regulation. Likewise, the combination of ART-mediated chemotherapy and the Fe²⁺/ART-regulated enhanced CDT enables noticeable immunogenic cell death, which can be collaborated with antibody-mediated immune checkpoint blockade to exert immunotherapy having significant antitumor immunity. The combined therapy improves the efficacy of primary tumor therapy and tumor metastasis inhibition by virtue of FN-mediated specific targeting of FDRF NCs to tumors with highly expressed α_vβ₃ integrin and can be guided through the Fe(III)-rendered magnetic resonance (MR) imaging. The developed FDRF NCs may be regarded as an advanced nanomedicine formulation for chemo-chemodynamic-immune therapy of different tumor types under MR imaging guidance.

Treatment of Acute Wounds With Recombinant Human-Like Collagen and Recombinant Human-Like Fibronectin in C57BL/6 Mice Individually or in Combination

Wound repair is accomplished by the interaction between the cells involved in the repair and the extracellular matrix (ECM). Collagen is the main component of ECM, which is involved in transduction of signal, transportation of growth factors and cytokines. Fibronectin (FN) is also an important ECM, which participates in the initiation of fibroblast cell (FC) and promotes adhesion, migration, proliferation and differentiation of target cells. Compared with natural protein, the recombinant protein prepared by artificial method has the advantages of poor immunogenicity, wide range of sources, low cost and high activity. In this study, we used recombinant human-like collagen (RHC) and recombinant human-like fibronectin (rhFN) to treat acute wounds in C57BL/6 mice individually or in combination, and explored their effects on wound healing. Our study confirmed that these two recombinant proteins could effectively promote the proliferation, migration and adhesion of FCs. Meanwhile, it could positively regulate the healing speed and quality of acute wounds, re-epithelialization, collagen deposition, inflammation and angiogenesis. Moreover, we proved that the combination of the two was better than the treatment alone. Consequently, it has a good prospect as a new tissue material in the field of skin repair.

Tissue-Specific Hydrogels for 3D Printing and Potential Application in Peripheral Nerve Regeneration

Decellularized extracellular matrix hydrogel (dECM-G) has demonstrated its significant tissue-specificity, high biocompatibility, and versatile utilities in tissue engineering. However, the low mechanical stability and fast degradation are major drawbacks for its application in 3D printing. Herein, we report a hybrid hydrogel system consisting of dECM-Gs and photocrosslinkable gelatin methacrylate (GelMA), which resulted in significantly improved printability and structural fidelity. These pre-mixed hydrogels retained high bioactivity and tissue-specificity due to their containing dECM-Gs. More specifically, it was realized that the hydrogel containing dECM-G derived from porcine peripheral nerves (GelMA/pDNM-G) effectively facilitated neurite growth and Schwann cell migration from 2D cultured dorsal root ganglion explants. The nerve cells were also encapsulated in the GelMA/pDNM-G hydrogel for 3D culture or underwent cell-laden bioprinting with high cell viability. The preparation of such GelMA/dECM-G hydrogels enabled the recapitulation of functional tissues through extrusion-based bioprinting, which holds great potential for applications in regenerative medicine.

Recent Trends in the Development of Bone Regenerative Biomaterials

The goal of a biomaterial is to support the bone tissue regeneration process at the defect site and eventually degrade in situ and get replaced with the newly generated bone tissue. Biomaterials that enhance bone regeneration have a wealth of potential clinical applications from the treatment of non-union fractures to spinal fusion. The use of bone regenerative biomaterials from bioceramics and polymeric components to support bone cell and tissue growth is a longstanding area of interest. Recently, various forms of bone repair materials such as hydrogel, nanofiber scaffolds, and 3D printing composite scaffolds are emerging. Current challenges include the engineering of biomaterials that can match both the mechanical and biological context of bone tissue matrix and support the vascularization of large tissue constructs. Biomaterials with new levels of biofunctionality that attempt to recreate nanoscale topographical, biofactor, and gene delivery cues from the extracellular environment are emerging as interesting candidate bone regenerative biomaterials. This review has been sculptured around a case-by-case basis of current research that is being undertaken in the field of bone regeneration engineering. We will highlight the current progress in the development of physicochemical properties and applications of bone defect repair materials and their perspectives in bone regeneration.

Laminin alpha 4 promotes bone regeneration by facilitating cell adhesion and vascularization

Selective cell retention (SCR) has been widely used as a bone tissue engineering technique for the real-time fabrication of bone grafts. The greater the number of mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) retained in the scaffold, the better the osteoinductive and angiogenic properties of the scaffold's microenvironment. Improved bioscaffold properties in turn lead to improved bone graft survival, bone regeneration, and angiogenesis. Laminin plays a key role in cell-matrix adhesion, cell proliferation, and differentiation. We designed a collagen-binding domain (CBD) containing the core functional amino acid sequences of laminin α4 (CBD-LN peptide) to supplement the functional surface of a collagen-based decalcified bone matrix (DBM) scaffold. This scaffold promoted MSCs and EPCs early cell adhesion through up-regulating the expression of integrin α5β1 and integrin αvβ3 respectively, thus accelerated the following cell spreading, proliferation, and differentiation. Interestingly, it promoted the retention of MSCs (CD90⁺/CD105⁺ cells) and EPCs (CD31⁺ cells) in the scaffold following the use of clinical SCR technology. Furthermore, the DBM/CBD-LN scaffold induced the formation of type H vessels through the activation of the HIF-1α signaling pathway. The DBM/CBD-LN scaffold displayed rapid bone formation and angiogenesis in vivo, suggesting that it might be used as a new biomaterial in bone tissue engineering. STATEMENT OF SIGNIFICANCE: Selective cell retention technology (SCR) has been utilized in clinical settings to manufacture bioactive bone grafts. Specifically, demineralized bone matrix (DBM) is a widely-used SCR clinical biomaterial but it displays poor adhesion performance and angiogenic activity. In this work, we designed a collagen-binding domain (CBD) containing the core functional amino acid sequences of laminin α4 to supplement the functional surface of a collagen-based DBM scaffold. This bioscaffold promoted SCR-mediated MSCs and EPCs early cell adhesion, thus accelerated the following cell spreading, proliferation, and differentiation. Our results indicate this bioscaffold greatly induced osteogenesis and angiogenesis in vivo. In general, this bioscaffold has a good prospect for SCR application and may provide highly bioactive bone implant in clinical environment.

Fibronectin in Fracture Healing: Biological Mechanisms and Regenerative Avenues

The importance of extracellular matrix (ECM) proteins in mediating bone fracture repair is evident, and fibronectin (FN) has emerged as a pivotal regulator of this process. FN is an evolutionarily conserved glycoprotein found in all tissues of the body, and functions in several stages of fracture healing. FN acts as a three-dimensional scaffold immediately following trauma, guiding the assembly of additional ECM components. Furthermore, FN regulates cellular behavior via integrin-binding and growth factor-binding domains, promoting downstream responses including cell recruitment, proliferation and differentiation. Due to its diverse functions, the development of FN-based strategies to promote fracture healing is under intense research. In this review, we discuss the recent advancements in utilizing FN-based biomaterials, showing promise in tissue engineering and regenerative medicine applications.

The clinical use of the enriched bone marrow obtained by selective cell retention technology in treating adolescent idiopathic scoliosis

Purpose

This retrospective study aimed to evaluate the curative effect of allografts in combination with bone marrow enrichment realised by selective cell retention (SCR) technology in treating adolescent idiopathic scoliosis (AIS).

Methods

From July 2014 to September 2016, 18 consecutive patients with AIS were treated by posterior fusion and pedicle screw instrumentation. Bone marrow aspirates were obtained and enriched by SCR technology to fabricate bone grafts in combination with allogeneic bones, which were implanted for spinal fusion. Postoperatively, the patients were observed for a minimum of 18 months, with a mean follow-up period of 48 months. The results were assessed both clinically and radiographically. All adverse events and complications were recorded.

Results

A total of 9 male and 9 female patients were included, with an average age of 15.6 years (range, 12–20). The average preoperative Cobb angle was 56° (range, 47°–85°). The average number of levels fused was 11 (range, 9–13). SCR could be accomplished intraoperatively, only consuming approximately 20 ​min. The enriching multiples of measured cellular elements were approximately 2.3–4.2. At final follow-up, the average Cobb angle correction was 83% (range, 61–96%). There was no obvious loss in correction with an average loss of 1.1° (2%). The visual analogue scale score and the Oswestry Disability Index score at final follow-up were significantly ameliorated than those preoperatively. The Scoliosis Research Society 30 questionnaire revealed remarkable improvement in the domains “pain”, “self-image/appearance”, and “satisfaction with management”. There was neither pseudarthrosis nor severe complication.

Conclusion

The use of SCR technology could be considered as an effective method for promoting spinal fusion in treating AIS. We proposed a safe, simple, and rapid approach to obtain effective bone grafts for spinal fusion.

The translational potential of this article

Enriched bone marrow obtained by selective cell retention technology has the potential to promote spinal fusion for the treatment of adolescent idiopathic scoliosis.

Inhibition of protein-tyrosine phosphatase 1B phosphorylation enhances early adhesion of mesenchymal stem cells to facilitate fabrication of tissue-engineered bone

Enhancement of cell-matrix adhesion is preferable and crucial in various fields of tissue engineering. Integrins are important receptors that facilitate cell-matrix adhesion, mediated by intracellular molecules and crosstalk with the cadherin adhesion pathway, which mainly facilitates cell-cell adhesion. Protein-tyrosine phosphatase 1B (PTP1B) has emerged as a pivot in the crosstalk between the cadherin adhesion pathway and the integrin adhesion pathway. The phosphorylation state of PTP1B tyrosine-152 (Y152) plays a central role in balancing the two different cell adhesion forms. In this study, a PTP1B Y152 region mimicking (152RM) peptide was designed to decrease the phosphorylation of PTP1B Y152 via competitive inhibition. As a result, the dissociation of cadherin complexes and the release of PTP1B from cadherin had sharply increased, and Src, an important intracellular component of integrin, was activated, indicating that the cadherin adhesion pathway was inhibited, whereas the integrin adhesion pathway was enhanced. Moreover, upon treatment with the 152RM peptide, we observed that the early adhesion of human bone marrow-derived mesenchymal stem cells (MSCs) was accelerated and the anchoring of MSCs on the surface of integrin ligands was enhanced by an enhanced matrix adhesion ability of MSCs themselves. Importantly, the 152RM peptide significantly promoted the adhesion efficiency of MSCs in the selective cell retention technology, which fabricates instant bone implants in clinical settings, to stimulate osteogenesis in vivo.

Bone Marrow-Derived CD44+ Cells Migrate to Tissue-Engineered Constructs via SDF-1/CXCR4-JNK Pathway and Aid Bone Repair

Background and Aims

Host-derived cells play crucial roles in the regeneration process of tissue-engineered constructs (TECs) during the treatment of large segmental bone defects (LSBDs). However, their identity, source, and cell recruitment mechanisms remain elusive.

Methods

A complex model was created using mice by combining methods of GFP⁺ bone marrow transplantation (GFP-BMT), parabiosis (GFP⁺-BMT and wild-type mice), and femoral LSBD, followed by implantation of TECs or DBM scaffolds. Postoperatively, the migration of host BM cells was detected by animal imaging and immunofluorescent staining. Bone repair was evaluated by micro-CT. Signaling pathway repressors including AMD3100 and SP600125 associated with the migration of BM CD44⁺ cells were further investigated. In vitro, transwell migration and western-blotting assays were performed to verify the related signaling pathway. In vivo, the importance of the SDF-1/CXCR4-JNK pathway was validated by ELISA, fluorescence-activated cell sorting (FACS), immunofluorescent staining, and RT-PCR.

Results

First, we found that host cells recruited to facilitate TEC-mediated bone repair were derived from bone marrow and most of them express CD44, indicating the significance of CD44 in the migration of bone marrow cells towards donor MSCs. Then, the predominant roles of SDF-1/CXCR4 and downstream JNK in the migration of BM CD44⁺ cells towards TECs were demonstrated.

Conclusion

Together, we demonstrated that during bone repair promoted by TECs, BM-derived CD44⁺ cells were essential and their migration towards TECs could be regulated by the SDF-1/CXCR4-JNK signaling pathway.

Shape-fitting collagen-PLA composite promotes osteogenic differentiation of porcine adipose stem cells

Craniomaxillofacial bone defects can occur as a result of congenital, post-oncologic, and high-energy impact conditions. The scale and irregularity of such defects motivate new biomaterials to promote regeneration of the damaged bone. We have recently described a mineralized collagen scaffold capable of instructing stem cell osteogenic differentiation and new bone infill in the absence of traditional osteogenic supplements. Herein, we report the integration of a millimeter-scale reinforcing poly (lactic acid) frame fabricated via 3D-printing into the mineralized collagen scaffold with micron-scale porosity to form a multi-scale mineralized collagen-PLA composite. We describe modifications to the PLA frame design to increase the compressive strength (Young's Modulus, ultimate stress and strain) of the composite. A critical challenge beyond increasing the compressive strength of the collagen scaffold is addressing challenges inherent with the irregularity of clinical defects. As a result, we examined the potential for modifying the frame architecture to render the composite with increased compressive strength in one axis or radial compressibility and shape-fitting capacity in an orthogonal axis. A library of mineralized collagen-PLA composites was mechanically characterized via compression testing and push-out test to describe mechanical performance and shape-fitting capacity. We also report in vitro comparison of the bioactivity of porcine adipose derived stem cells in the mineralized collagen-PLA composite versus the mineralized collagen scaffold via metabolic activity, gene expression, and functional matrix synthesis. The results suggest that incorporation of the PLA reinforcing frame does not negatively influence the osteoinductive nature of the mineralized collagen scaffold. Together, these findings suggest a strategy to address often competing bioactivity, mechanical strength, and shape-fitting design requirements for biomaterials for craniomaxillofacial bone regeneration.

Multiple integrin ligands provide a highly adhesive and osteoinductive surface that improves selective cell retention technology

Among various bone tissue engineering strategies, selective cell retention (SCR) technology has been used as a practical clinical method for bone graft manufacturing in real time. The more mesenchymal stem cells (MSCs) are retained, the better the osteoinductive microenvironment provided by the scaffold, which in turn promotes the osteogenesis of the SCR-fabricated bone grafts. Integrin receptors are crucial to cell-matrix adhesion and signal transduction. We designed a collagen-binding domain (CBD)-containing IKVAV-cRGD peptide (CBD-IKVAV-cRGD peptide) to complement the collagen-based demineralized bone matrix (DBM) with a functionalized surface containing multiple integrin ligands, which correspond to the highly expressed integrin subtypes on MSCs. This DBM/CBD-IKVAV-cRGD composite exhibited superior in vitro adhesion capacity to cultured MSCs, as determined by oscillatory cell adhesion assay, centrifugal cell adhesion assay and mimetic SCR. Moreover, it promoted the retention of MSC-like CD271⁺ cells and MSC-like CD90⁺/CD105⁺ cells in the clinical SCR method. Furthermore, the DBM/CBD-IKVAV-cRGD composite induced robust MSC osteogenesis, coupled with the activation of the downstream FAK-ERK1/2 signaling pathway of integrins. The SCR-prepared DBM/CBD-IKVAV-cRGD composite displayed superior in vivo osteogenesis, indicating that it may be potentially utilized as a biomaterial in SCR-mediated bone transplantation. STATEMENT OF SIGNIFICANCE: Selective cell retention technology (SCR) has been utilized in clinical settings to manufacture bioactive bone grafts. Specifically, demineralized bone matrix (DBM) is a widely-used SCR clinical biomaterial but it displays poor adhesion performance and osteoinduction. Improvements of the DBM that promote cell adhesion and osteoinduction will benefit SCR-prepared implants. In this work, we developed a novel peptide that complements the DBM with a functionalized surface of multiple integrin ligands, which are corresponding to integrin subtypes available on human bone marrow-derived mesenchymal stem cells (MSCs). Our results indicate this novel functionalized bioscaffold greatly increases SCR-mediated MSC adhesion and in vivo osteogenesis. Overall, this novel material has promising SCR applications and may likely provide highly bioactive bone implants in clinical settings.

Bone physiology as inspiration for tissue regenerative therapies

The development, maintenance of healthy bone and regeneration of injured tissue in the human body comprise a set of intricate and finely coordinated processes. However, an analysis of current bone regeneration strategies shows that only a small fraction of well-reported bone biology aspects has been used as inspiration and transposed into the development of therapeutic products. Specific topics that include inter-scale bone structural organization, developmental aspects of bone morphogenesis, bone repair mechanisms, role of specific cells and heterotypic cell contact in the bone niche (including vascularization networks and immune system cells), cell-cell direct and soluble-mediated contact, extracellular matrix composition (with particular focus on the non-soluble fraction of proteins), as well as mechanical aspects of native bone will be the main reviewed topics. In this Review we suggest a systematic parallelization of (i) fundamental well-established biology of bone, (ii) updated and recent advances on the understanding of biological phenomena occurring in native and injured tissue, and (iii) critical discussion of how those individual aspects have been translated into tissue regeneration strategies using biomaterials and other tissue engineering approaches. We aim at presenting a perspective on unexplored aspects of bone physiology and how they could be translated into innovative regeneration-driven concepts.

Ectopic osteogenesis effect of antigen-extracted xenogeneic cancellous bone graft with chitosan/rhBMP-2/bFGF sequential sustained-release nanocapsules

To explore the ectopic osteogenesis effect of sequential sustained release application of recombinant human bone morphogenic protein-2 (rhBMP-2) and basic fibroblast growth factor (bFGF). Antigen-extracted xenogeneic cancellous bone coupled with growth factor-loaded chitosan nanocapsules were implanted in rats in intramuscular site in accordance with the following experimental pattern: group A: simultaneous burst release of rhBMP-2 and bFGF; group B: simultaneous sustained release of rhBMP-2 and bFGF; group C: preferential burst release of rhBMP-2, then sustained release of bFGF; group D: preferential burst release of bFGF, then sustained release of rhBMP-2; group E: sustained release of rhBMP-2 alone; group F: sustained release of bFGF alone, blank control group G: antigen-extracted xenogeneic cancellous bone graft only; negative control group H: not filled with anything. Specimens were obtained after executing the animals at 2 and 4 weeks for general observation and weighing, calcium content detection, micro-CT scanning and bone parameter measurement analysis, H&E staining, ALP staining and CD34 staining. The materials weight of A-2, B-2, C-2, A-4, B-4, C-4, D-4 and E-4 were significantly higher than that of preoperative materials ( P < 0.05). The concentration of calcium of group B-4 was the highest (414.7 ± 12.03 mg/dl). Micro-CT scanning and bone parameter measurement analysis showed that the values of bone mineral density and trabecular thickness of group A, B, D, E at 4 weeks were both higher than the ones at 2 weeks ( P < 0.05), and both the bone mineral density (367.52 ± 11.64 mg/cc) and the trabecular thickness (126.17 ± 11.36 μm) of group B-4 were the highest. H&E staining showed that a large region of calcified cartilage and haemopoietic tissues were newly formed, especially in group B-4. ALP staining and CD34 staining showed the most positive expression region in group B-4. Therefore, we conclude that simultaneous sustained release of rhBMP-2 and bFGF is the ideal way to release drug, and has better inducement of antigen-extracted xenogeneic cancellous bone graft.