Small intestine submucosa sponge for in vivo support of tissue-engineered bone formation in the presence of rat bone marrow stem cells

The osteogenic and angiogenic potential of microRNA-26a delivered via a non-viral delivery peptide for bone repair

Bone-related injuries and diseases are among the most common causes of morbidity worldwide. Current bone-regenerative strategies such as auto- and allografts are invasive by nature, with adverse effects such as pain, infection and donor site morbidity. MicroRNA (miRNA) gene therapy has emerged as a promising area of research, with miRNAs capable of regulating multiple gene pathways simultaneously through the repression of post-transcriptional mRNAs. miR-26a is a key regulator of osteogenesis and has been found to be upregulated following bone injury, where it induces osteodifferentiation of mesenchymal stem cells (MSCs) and facilitates bone formation. This study demonstrates, for the first time, that the amphipathic, cell-penetrating peptide RALA can efficiently deliver miR-26a to MSCs in vitro to regulate osteogenic signalling. Transfection with miR-26a significantly increased expression of osteogenic and angiogenic markers at both gene and protein level. Using a rat calvarial defect model with a critical size defect, RALA/miR-26a NPs were delivered via an injectable, thermo-responsive Cs-g-PNIPAAm hydrogel to assess the impact on both rate and quality of bone healing. Critical defects treated with the RALA/miR-26a nanoparticles (NPs) had significantly increased bone volume and bone mineral density at 8 weeks, with increased blood vessel formation and mechanical properties. This study highlights the utility of RALA to deliver miR-26a for the purpose of bone healing within an injectable biomaterial, warranting further investigation of dose-related efficacy of the therapeutic across a range of in vivo models.

Bioinformatic analysis of the molecular mechanisms underlying the progression of bone defects

Background

The pathophysiology of bone defects (BDs) is complex, and the treatment for bone defects, in particular massive bone defects, remains a major clinical challenge. Our study was conducted to explore the molecular events related to the progression of bone defects a common clinical condition.

Methods

First, microarray data of GSE20980 were obtained from the Gene Expression Omnibus (GEO) database, where 33 samples in total were used to analyze the molecular biological processes related to bone defects. Next, the original data were normalized and differentially expressed genes (DEGs) were identified. Additionally, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were conducted. Finally, a protein-protein interaction (PPI) network was constructed and the trends of the different genes were confirmed.

Results

Compared with the samples of non-critical size defects (NCSD), the samples of critical size defects (CSD) had 2057, 827, and 1,024 DEGs at 7, 14, and 21 days post injury, respectively. At day 7, the DEGs were significantly enriched in metabolic pathways, at day 14 the DEGs were predominantly enriched in G-protein coupled signaling pathways and the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway, and at day 21 the DEGs were mainly enriched in circadian entrainment and synaptic-related functions. The PPI network showed similar results. Quantitative real-time PCR (qRT-PCR) and western blot (WB) were performed to validate the partial results of sequencing.

Conclusion

This study provides some clues about the molecular mechanism behind bone defects, which should contribute to scientific research and clinical treatment of this condition.

Bioactive impact of manuka honey and bone char incorporated into gelatin and chitosan cryogels in a rat calvarial fracture model

Bone tissue engineered scaffolds are designed to mimic the natural environment for regeneration when typical healing is inhibited. Autografts are the current gold standard for treatment but are limited by available bone and supplementary surgical sites that broaden complications and comorbidities. Cryogels are an ideal scaffold in bone regeneration due to their mechanical integrity and marcoporous structure that elicits angiogenesis and subsequently new bone tissue formation. To aid in bioactivity and osteoinductivity, manuka honey (MH) and bone char (BC) were added to gelatin and chitosan cryogels (CG). Manuka honey has powerful antimicrobial properties to aid against graft infection, and bone char is composed of 90% hydroxyapatite, a well-studied bioactive material. These additives are natural, abundant, easy to use, and cost effective. CG cryogels incorporated with either BC or MH, and plain CG cryogels were implanted into rat calvarial fracture models for cortical bone regeneration analysis. We found indication of bioactivity with both bone char and manuka honey through the presence of woven bone structure in histology stains and micro computed tomography (microCT) data. Overall, plain CG cryogels supported greater bone regeneration capabilities than the BC or MH incorporated cryogels due to a lack of advanced organized tissue formation and collagen deposition after 8 weeks of implantation; however, future work should explore varying additive concentrations and delivery methods to further assess additive potential.

Potential of Aligned Electrospun PLGA/SIS Blended Nanofibrous Membrane for Tendon Tissue Engineering

Tendons are responsible for transmitting mechanical forces from muscles to bones for body locomotion and joint stability. However, tendons are frequently damaged with high mechanical forces. Various methods have been utilized for repairing damaged tendons, including sutures, soft tissue anchors, and biological grafts. However, tendons experience a higher rate of retear post-surgery due to their low cellularity and vascularity. Surgically sutured tendons are vulnerable to reinjury due to their inferior functionality when compared with native tendons. Surgical treatment using biological grafts also has complications such as joint stiffness, re-rupture, and donor-site morbidity. Therefore, current research is focused on developing novel materials that can facilitate the regeneration of tendons with histological and mechanical characteristics similar to those of intact tendons. With respect to the complications in association with the surgical treatment of tendon injuries, electrospinning may be an alternative for tendon tissue engineering. Electrospinning is an effective method for fabrication of polymeric fibers with diameters ranging from nanometers to micrometers. Thus, this method produces nanofibrous membranes with an extremely high surface area-to-volume ratio, which is similar to the extracellular matrix structure, making them suitable candidates for application in tissue engineering. Moreover, it is possible to fabricate nanofibers with specific orientations that are similar to those of the native tendon tissue using an adequate collector. To increase the hydrophilicity of the electrospun nanofibers, natural polymers in addition to synthetic polymers are used concurrently. Therefore, in this study, aligned nanofibers composed of poly-d,l-lactide-co-glycolide (PLGA) and small intestine submucosa (SIS) were fabricated using electrospinning with rotating mandrel. The diameter of aligned PLGA/SIS nanofibers was 568.44 ± 135.594 nm, which closely resembles that of native collagen fibrils. Compared to the results of the control group, the mechanical strength exhibited by the aligned nanofibers was anisotropic in terms of break strain, ultimate tensile strength, and elastic modulus. Elongated cellular behavior was observed in the aligned PLGA/SIS nanofibers using confocal laser scanning microscopy, indicating that the aligned nanofibers were highly effective with regard to tendon tissue engineering. In conclusion, considering its mechanical properties and cellular behavior, aligned PLGA/SIS is a promising candidate for tendon tissue engineering.

A systematic review of bone marrow stromal cells and periosteum-derived cells for bone regeneration

Bone marrow stromal cells (BMSCs) and periosteum-derived cells (PDCs) represent promising skeletal stem cell sources to treat critical-size bone defects. However, the large number of preclinical tests with a variety of in vivo data complicates the selection of cells for further clinical translation. This systematic review aims to analyze the in vivo bone-forming efficacy of BMSCs- and PDCs-based approaches in all published preclinical experiments until November 2020. For this purpose, four databases (PubMed, Embase, Cochrane Central Register of Controlled Trial, and Web of Science) were searched for eligible literature, which yielded a total of 94 full-text articles for systematic review. This review generated an evidence-based list of BMSC- or PDC-based approaches, which have been evaluated for bone formation in different animal models. Among them, 74 studies were included for pairwise and network meta-analysis. The results revealed that both PDC and BMSC had beneficial bone-forming efficacy compared to bare scaffold. In addition, BMSC- and PDC-based approaches had no significant difference regarding in vivo bone-forming efficacy. However, BMSC-based approach had a higher probability to be ranked better than PDC-based approach. Furthermore, the review discusses (i) the possible risk of bias of the in vivo evaluation of cell-based approaches, (ii) the difficulty in replication of such experiments due to frequent poor reporting of the methods and results, and (iii) the clinical relevance of the currently utilized BMSC- and PDC-based approaches. Systematic review registration: The study was prospectively registered in PROSPERO, Registration No. CRD42021270922.

UC-MSCs seeded on small intestinal submucosa to repair the uterine wall injuries

OBJECTIVE

The effectiveness of tissue engineering materials combining porcine small intestine submucosa (SIS) and umbilical cord mesenchymal stem cells (UC-MSCs) on uterine injury in female rat after full-thickness uterine resection was evaluated as a basis for clinical treatment of postoperative uterine injury.

METHODS

After complex culture with SIS and UC-MSCs, cell adhesion, growth and proliferation were assessed . Before the implantation, a surgical procedure of bilateral full-thickness uterine resection (0.5 ~ 2.0 cm long and 0.3 cm wide) was performed to obtain the rat uterine injury model, while the sham-operated rats were used as controls. H&E staining results and fertility of female rats in each group were assessed to determine the critical resection length of the full-thickness uterine resection. Then SIS or UC-MSCs-SIS were implanted into the female rats from the uterine injury group, followed by assessments of H&E staining, the expressions of ki67, α-SMA and LIF, and fertility to determine the effectiveness of SIS and UC-MSCs-SIS on uterine injury in female rat.

RESULTS

At 24, 48 and 72 h, the cells grew progressively on the SIS material. In the 1.5 cm and 2.0 cm groups, the pregnancy rate, proportion of the uterus supporting live embryo growth, number of live embryos, and proportion of live embryos were all significantly less than those in the 0.5 cm and sham-operated groups. In the 2.0 cm group, there was little tissue regeneration at the center of the injury and not conducive to subsequent assessment. The UC-MSCs-SIS and SIS groups were better on morphological development, cell proliferation, LIF expression and fertility than the control group.

CONCLUSION

UC-MSCs show good adhesion, growth, and proliferation on the SIS scaffold material. The optimal resection length in full-thickness uterine resection on female rat is 1.5 cm. UC-MSCs-SIS is the effective treatment for repairing a injury after the full-thickness resection of the uterus in this research.

Guided bone regeneration with extracellular matrix scaffold of small intestinal submucosa membrane

Guided bone regeneration (GBR) is a promising strategy for repairing bone defects using bioactive membranes. In this study, a new type of GBR membrane based on the small intestinal submucosa (SIS) was created, and its surface structure, cytological characteristics, and bone defect repair ability were compared with commonly used membranes. Our results show that compared to the Heal-all and Dentium membranes, the SIS membrane has an asymmetric structure that does not affect the proliferation of bone marrow mesenchymal stem cells (BMSCs). Instead, it increased their formation of calcium nodules and expression of bone morphogenetic protein-2 (BMP-2), alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), and osteopontin (OPN). Six weeks after their insertion into a rat calvarial defect model, increased bone growth was observed in the SIS membrane group. Our results indicate that the SIS membrane has good biocompatibility and is more effective in promoting early bone formation than existing membranes. Given the wide range of source materials and simple preparation processes available, SIS membrane is a promising candidate for guided bone regeneration.

Chitosan-CaP microflowers and metronidazole loaded calcium alginate sponges with enhanced antibacterial, hemostatic and osteogenic properties for the prevention of dry socket after tooth removal

Tooth removal, particularly for patients with severe periodontitis, can frequently cause massive bleeding, postoperative infection, and bone resorption, resulting in a dry socket. Thus, developing bio-multifunctional materials with excellent antibacterial, hemostatic, and osteogenic characteristics for the prevention of dry sockets after tooth removal is highly desirable in clinical applications. Herein, chitosan-CaP microflowers (CM) and metronidazole (MD) loaded calcium alginate (CA) sponges (CA@CM/MD) with enhanced antibacterial, hemostatic, and osteogenic properties were developed via Ca²⁺ crosslinking, lyophilization, and electrostatic interaction for the prevention of dry socket after tooth removal. The fabricated CM particles display 3-dimensional, relatively homogeneous, and flower-shaped architectures. The CA@CM/MD composite sponges were facilely shaped into the tooth root as well as exhibit interconnected porous and lamellar structures with remarkable porosity, suitable maximum swelling ratio, as well as excellent compressive and hemostatic performance. Besides, the in vitro cellular assessment demonstrates that the prepared CA@CM/MD composite sponges possess satisfactory cytocompatibility. Importantly, the designed sponges significantly suppress the growth of S. aureus and E. coli, as well as promote cellular osteogenic differentiation by upregulating the formation of alkaline phosphatase. Our findings indicate that the tooth root-shaped composite sponges hold great promise for wound management after tooth removal.

Hydroxyapatite formation in biomimetic synthesis with the interface of a pDA@SIS membrane

Porcine decellularized small intestine submucosa (SIS) is a collagen membrane, which offers great potential as an organic substrate template in mineralization processes due to its good biodegradability and biocompatibility. However, a long period of mineralization and low efficiency are apparent, and the mechanism of collagen fiber mineralization has often been neglected in the previous literature. Thus, in this paper, we present a novel model of biomimetic collagen mineralization which uses dopamine (DA) molecules with the activating and retouching function of SIS collagen membranes and regulating collagen mineralization to construct the structure of mineralized collagen hard tissues. The crystal biomimetic mineralization growth of calcium phosphate on membranes is studied in different solid-liquid interfaces with a double ion self-assembled diffusion system under the simulated physiological microenvironment. In the system, pDA@SIS membranes are used to control the concentration of Ca²⁺ and PO₄ ^3- ionic diffusion to generate supersaturation reaction conditions in 1-14 days. The system can successfully obtain polycrystals with low crystallinity on the pDA-collagen complex template surface of collagen fibers and along the collagen fibers. It initiates a generalized bionic mineralization pathway which can reduce the nucleation interfacial energy to promote rapid hydroxyapatite (HAP) nucleation and crystallization and accelerate the rate of collagen fiber mineralization. The pDA@SIS mineralized collagen membrane shows good biocompatibility with 100% cellular activity in the CCK-8 test, which significantly improved the adhesion proliferation of MC3T3-E1 cells. The pDA-SIS collagen complex, as a new type of mineralization template, may propose a new collagen mineralization strategy to produce a mineralized pDA@SIS scaffold bone-like material for tissue engineering or can potentially be applied in bone repair and regeneration.

Independent effects of structural optimization and resveratrol functionalization on extracellular matrix scaffolds for bone regeneration

Due to their natural biological activity and low immunogenicity, decellularized extracellular matrix (ECM) materials have aroused interest as potential scaffold materials in tissue engineering. Decellularized small intestinal submucosa (SIS) is one ECM biomaterial that can be easily sourced. In the present study, we tested whether the osteogenesis of SIS scaffolds was enhanced via structural optimization and resveratrol (RSV) functionalization and explored the independent effects of these modifications. We obtained SIS scaffolds with different pore structures by controlling the preparation concentration. The group with superior osteogenic properties was further RSV-functionalized via covalent immobilization. We conducted a series of in vitro and in vivo studies to explore the effects of these two optimization strategies on the osteogenic properties of SIS scaffolds. The results showed that pore structure and RSV functionalization significantly affected the osteogenic properties of SIS scaffolds. With a fabrication concentration of 1%, the SIS scaffolds had superior osteogenic properties. Through covalent coupling, RSV was successfully grafted onto SIS scaffolds, where it was slowly released. The most significant improvements in osteogenic properties were obtained with a coupling concentration of 1%. Furthermore, in in vivo experiments, vascular and new bone tissue formation was enhanced with RSV/SIS scaffolds compared with SIS scaffolds and the blank control group at 4 weeks after implantation. These findings indicate that the RSV/SIS scaffolds obtained via dual optimization strategies show promise as biomaterials in bone tissue engineering.

3D printing of Ti3C2-MXene-incorporated composite scaffolds for accelerated bone regeneration

Grafting of bone-substitute biomaterials plays a vital role in the reconstruction of bone defects. However, the design of bioscaffolds with osteoinductive agents and biomimetic structures for regeneration of critical-sized bone defects is difficult. Ti3C2 MXene-belonging to a new class of two-dimensional (2D) nanomaterials-exhibits excellent biocompatibility, and antibacterial properties, and promotes osteogenesis. However, its application in preparing 3D-printed tissue-engineered bone scaffolds for repairing bone defects has not been explored. In this work, Ti3C2 MXene was incorporated into composite scaffolds composed of hydroxyapatite (HA) and sodium alginate (SA) via extrusion-based 3D printing to evaluate its potential in bone regeneration. MXene composite scaffolds were fabricated and characterized by SEM, XPS, mechanical properties and porosity. The biocompatibility and osteoinductivity of MXene composite scaffolds were evaluated by cell adhesion, CCK-8 test, qRT-PCR, ALP activity and ARS tests of BMSCs. A rat calvarial defect model was performed to explore the osteogenic activity of the MXene composite scaffolds in vivo. The results showed the obtained scaffold had a uniform structure, macropore morphology, and high mechanical strength. In vitro experimental results revealed that the scaffold exhibited excellent biocompatibility with bone mesenchymal stem cells, promoted cell proliferation, upregulated osteogenic gene expression, enhanced alkaline phosphatase activity, and promoted mineralized-nodule formation. The experimental results confirmed that the scaffold effectively promoted bone regeneration in a model of critical-sized calvarial- bone-defect in vivo and promoted bone healing to a significantly greater degree than scaffolds without added Ti3C2 MXene did. Conclusively, the Ti3C2 MXene composite 3D-printed scaffolds are promising for clinical bone defect treatment, and the results of this study provide a theoretical basis for the development of practical applications for tissue-engineered bone scaffolds.

Tough, Flexible, and Bioactive Amphoteric Copolymer-Based Hydrogel for Bone Regeneration without Encapsulation of Seed Cells/Simulating Cues

Bone tissue scaffolds with good bulk or surface osteoconductivity are always pursued by biomaterial scientists. In this paper, we design a tough and flexible amphoteric copolymer-based (AC) hydrogel with bioactive groups for bone regeneration. In detail, our hydrogels are copolymerized with N-acyl glycinamide (NAGA), anionic acrylate alendronate (AcAln), and cationic (2-(acryloyloxy)ethyl) trimethyl ammonium chloride (DMAEA-Q) by free radical polymerization. There are three kinds of synergetic physical cross-links among our polyamphion hydrogels: (1) double hydrogen bonds between amide groups in NAGA to provide toughness, (2) hydrogen bonds between dual bisphosphite groups in AcAln, and (3) weak ionic pairs between the anionic bisphosphite groups and the cationic quaternary ammonium groups in DMAEA-Q to offer flexibility. The AC hydrogel shows osteoid-like viscoelasticity, which makes the AC hydrogel osteogenesis inductive. During the repairing process, the bioactive bisphosphite groups accelerate the calcium fixation to expedite the mineralization of the new-formed bone. At the same time, the surface charge property of AC hydrogels also prevents fibrous cyst formation, thus guaranteeing osseointegration. Our in vitro data strongly demonstrate that the AC hydrogel is an excellent matrix to induce osteogenesis of rat bone marrow mesenchymal stem cells. More importantly, the following in vivo experiments further prove that the AC hydrogel can reach satisfactory bone regeneration without encapsulation of seed cells or application of external simulating cues. These exciting results demonstrate that our AC hydrogel is a promising scaffold for bone regeneration. Our work can also inspire the constituent and structure design of biomaterial scaffolds for tissue regeneration.

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.

Migration and phenotype switching of macrophages at early-phase of bone-formation by secretomes from bone marrow derived mesenchymal stem cells using rat calvaria bone defect model

Background/purpose

Conditioned media of cultured mesenchymal stem cells (MSCs) contain numerous kinds of secretomes such as cytokines and chemokines. We previously reported that conditioned media of bone marrow-derived MSCs (MSC-CM) promote bone formation. Recently, macrophage phenotype switching from the pro-inflammatory M1 type to the anti-inflammatory M2 type has been reported to be an important phenomenon during tissue regeneration. Some studies reported that this phenotype switching is regulated by secretomes. In this study, macrophage phenotype during bone formation by MSC-CM was investigated.

Materials and methods

Human MSCs (hMSCs) were cultured in serum-free medium and the collected medium was defined as MSC-CM. Macrophage-related gene expressions in hMSCs cultured with MSC-CM were evaluated by quantitative real-time polymerase chain reaction. MSC-CM was implanted and the evaluations by micro-CT and immunohistochemistry were performed using a rat the calvaria bone defect model.

Results

Two and four weeks after implantation, the MSC-CM group demonstrated enhanced bone regeneration. Gene expressions of C–C motif chemokine 2 (CCL2), colony-stimulating factor 2 (CSF2) and CD163 was significantly upregulated in cells exposed to MSC-CM. Immunohistochemical staining revealed that iNOS-positive M1 macrophages were reduced, while CD204-positive M2 macrophages were increased in the MSC-CM group at 72 h after implantation, and the M2/M1 ratio increased only in the MSC-CM group.

Conclusion

MSC-CM enhances macrophage migration and induces M1 to M2 type macrophage switching at an early stage of osteogenesis. Such phenotype switching provides a favorable environment for angiogenesis, cellular migration, and osteogenesis and contributes to MSC-CM-induced early bone formation.

Vascularized nanocomposite hydrogel mechanically reinforced by polyelectrolyt-modified nanoparticles

Vascularization plays an important role in the initial stage of triggering the bone defects repair. The combination of bioactive small molecule drugs and biomaterials has been a powerful strategy for...

Decellularization of Small Intestinal Submucosa

Small intestinal submucosa (SIS) is the most studied extracellular matrix (ECM) for repair and regeneration of different organs and tissues. Promising results of SIS-ECM as a vascular graft, led scientists to examine its applicability for repairing other tissues. Overall results indicated that SIS grafts induce tissue regeneration and remodeling to almost native condition. Investigating immunomodulatory effects of SIS is another interesting field of research. SIS can be utilized in different forms for multiple clinical and experimental studies. The aim of this chapter is to investigate the decellularization process of SIS and its common clinical application.

Intra-articular Injection of Kartogenin-Enhanced Bone Marrow-Derived Mesenchymal Stem Cells in the Treatment of Knee Osteoarthritis in a Rat Model

BACKGROUND

In this study, we investigated the in vitro and in vivo chondrogenic capacity of kartogenin (KGN)-enhanced bone marrow-derived mesenchymal stem cells (BMSCs) for cartilage regeneration.

PURPOSE

To determine (1) whether functionalized nanographene oxide (NGO) can effectively deliver KGN into BMSCs and (2) whether KGN would enhance BMSCs during chondrogenesis in vitro and in vivo in an animal model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Functionalized NGO with line chain amine-terminated polyethylene glycol (PEG) and branched polyethylenimine (BPEI) were used to synthesize biocompatible NGO-PEG-BPEI (PPG) and for loading hydrophobic KGN molecules noncovalently via π-π stacking and hydrophobic interactions (PPG-KGN). Then, PPG-KGN was used for the intracellular delivery of hydrophobic KGN by simple mixing and co-incubation with BMSCs to acquire KGN-enhanced BMSCs. The chondrogenic efficacy of KGN-enhanced BMSCs was evaluated in vitro. In vivo, osteoarthritis (OA) was induced by anterior cruciate ligament transection in rats. A total of 5 groups were established: normal (OA treated with nothing), phosphate-buffered saline (PBS; intra-articular injection of PBS), PPG-KGN (intra-articular injection of PPG-KGN), BMSCs (intra-articular injection of BMSCs), and BMSCs + PPG-KGN (intra-articular injection of PPG-KGN-preconditioned BMSCs). At 6 and 9 weeks after the surgical induction of OA, the rats received intra-articular injections of PPG-KGN, BMSCs, or KGN-enhanced BMSCs. At 14 weeks after the surgical induction of OA, radiographic and behavioral evaluations as well as histological analysis of the knee joints were performed.

RESULTS

The in vitro study showed that PPG could be rapidly uptaken in the first 4 hours after incubation, reaching saturation at 12 hours and accumulating in the lysosome and cytoplasm of BMSCs. Thus, PPG-KGN could enhance the efficiency of the intracellular delivery of KGN, which showed a remarkably high chondrogenic differentiation capacity of BMSCs. When applied to an OA model of cartilage injuries in rats, PPG-KGN-preconditioned BMSCs contributed to protection from joint space narrowing, pathological mineralization, OA development, and OA-induced pain, as well as improved tissue regeneration, as evidenced by radiographic, weightbearing, and histological findings.

CONCLUSION

Our results demonstrate that KGN-enhanced BMSCs showed markedly improved capacities for chondrogenesis and articular cartilage repair. We believe that this work demonstrates that a multifunctional nanoparticle-based drug delivery system could be beneficial for stem cell therapy. Our results present an opportunity to reverse the symptoms and pathophysiology of OA.

CLINICAL RELEVANCE

The intracellular delivery of KGN to produce BMSCs with enhanced chondrogenic potential may offer a new approach for the treatment of OA.

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

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

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.

[Preparation and osteogenic effect study of small intestinal submucosa sponge]

OBJECTIVE

To prepare and evaluate the basic properties in vitro of a novel small intestinal submucosa (SIS) sponge, and to describe the bone formation ability of the SIS sponge in vivo.

METHODS

The SIS sponge was prepared by freeze-drying method. To evaluate the physicochemical properties of the sponge, electron microscope observation, porosity test, water absorption ability and mechanical property were conducted in vitro. The cytotoxicity of the SIS sponge was performed by cell counting kit-8 method. In vivo experiments, eighteen extraction sockets of premolar of three Beagle dogs were randomly divided into three groups: SIS sponge group (SIS sponge), positive control group (Bio-Oss granules and Bio-Gide membrane) and control group(no treatment). The animals were sacrificed 4 weeks and 12 weeks after operation, and micro computed tomography (Micro-CT) was applied to measure the bone volume fraction (BV/TV) and bone mineralized density (BMD). The data were analyzed with one-way ANOVA.

RESULTS

The average pore diameter of the SIS sponge was (194.90±30.39) μm, the porosity was 92.31%±0.24%, the water absorption rate was 771.50%±40.90%, and the compressive elastic modulus was (2.20±0.19) kPa. There was no significant difference in cell proliferation ability between SIS sponge and control group (P>0.05). Micro-CT quantitative results showed that BV/TV of SIS sponge group (52.81%±3.21%) and positive control group (58.30%±9.36%) were significantly higher than that of control group (38.65%±4.80%) 4 weeks after operation (P < 0.05). The BMD of SIS sponge group [(887.09±61.02) mg/cm³], positive control group [(952.05±132.78) mg/cm³] and control group [(879.29±74.27) mg/cm³] showed no statistical difference 4 weeks after operation (P>0.05). The BV/TV of positive control group (60.57%± 6.56%) was significantly higher than that of SIS sponge group (47.89%±3.59%) and control group (42.99%±2.54%) 12 weeks after operation (P < 0.05). BMD of SIS sponge group [(1047±89.95) mg/cm³] and positive control group [(1101.37±98.85) mg/cm³] were significantly higher than that of control group [(890.36±79.79) mg/cm³] 12 weeks after operation (P < 0.05).

CONCLUSION

The SIS sponge has satisfying physicochemical properties and biocompatibility. The SIS sponge significantly increased bone volume fraction in the early stage of bone formation (4 weeks) and bone mineralized density in the late stage of bone formation (12 weeks).

2D titanium carbide(MXene) nanosheets and 1D hydroxyapatite nanowires into free standing nanocomposite membrane: in vitro and in vivo evaluations for bone regeneration

Bone loss or insufficiency remains a great challenge for implant integrated and subsequently functional loading, where developing biomaterials to augment bone quantity and regenerate alveolar bone defects at implant site is vitally necessary. Recently, MXene, as a large new family of 2D materials, exhibits a great prospect in biomedical applications owing to its ultrathin structure and morphology with a range of extraordinary properties such as chemical, electronic, optical and biological properties etc. Besides, hydroxyapatite is a favorable biomaterial with outstanding bioactivity and osteogenic capacity. In this study, we prepared free standing UHAPNWs/MXene nanocomposite membranes via introducing ultralong hydroxyapatite nanowires (UHAPNWs) with different weight ratios into MXene to explore their potential in bone regeneration. SEM, XPS, FTIR, XRD, tensile strength, Young's modulus and water contact angles were used to characterize the morphology, chemical composition, surface properties, mechanical properties and hydrophilicity of the materials. Subsequently, in vitro studies like cell adhesion, proliferation and osteogenic differentiation of MC3T3-E1 were evaluated. The incorporation of UHAPNWs improved mechanical properties and hydrophilicity with an enhancement in cell adhesion, proliferation, and osteogenic differentiation. More importantly, 10 wt% UHAPNWs/MXene exhibited the optimal mechanical properties while biological improvement was more pronounced along with the addition of UHAPNWs when the weight fraction of UHAPNWs was from 0 to 30 wt%. Furthermore, in vivo experiments the UHAPNWs/MXene nanocomposite membranes effectively enhanced bone tissue formation quantitatively and qualitatively in a rat calvarial bone defect. Therefore, an appropriate amount of UHAPNWs into MXene plays a positive and evident role in enhancing mechanical properties, biocompatibility and osteoinductivity, leading a novel inorganic composite material for regeneration of bone tissue.

Surface modification of small intestine submucosa in tissue engineering

With the development of tissue engineering, the required biomaterials need to have the ability to promote cell adhesion and proliferation in vitro and in vivo. Especially, surface modification of the scaffold material has a great influence on biocompatibility and functionality of materials. The small intestine submucosa (SIS) is an extracellular matrix isolated from the submucosal layer of porcine jejunum, which has good tissue mechanical properties and regenerative activity, and is suitable for cell adhesion, proliferation and differentiation. In recent years, SIS is widely used in different areas of tissue reconstruction, such as blood vessels, bone, cartilage, bladder and ureter, etc. This paper discusses the main methods for surface modification of SIS to improve and optimize the performance of SIS bioscaffolds, including functional group bonding, protein adsorption, mineral coating, topography and formatting modification and drug combination. In addition, the reasonable combination of these methods also offers great improvement on SIS surface modification. This article makes a shallow review of the surface modification of SIS and its application in tissue engineering.

Repair strategies for injured peripheral nerve: Review

Compromised functional regains in about half of the patients following surgical nerve repair pose a serious socioeconomic burden to the society. Although surgical strategies such as end-to-end neurorrhaphy, nerve grafting and nerve transfer are widely applied in distal injuries leading to optimal recovery; however in proximal nerve defects functional outcomes remain unsatisfactory. Biomedical engineering approaches unite the efforts of the surgeons, engineers and biologists to develop regeneration facilitating structures such as extracellular matrix based supportive polymers and tubular nerve guidance channels. Such polymeric structures provide neurotrophic support from injured nerve stumps, retard the fibrous tissue infiltration and guide regenerating axons to appropriate targets. The development and application of nerve guidance conduits (NGCs) to treat nerve gap injuries offer clinically relevant and feasible solutions. Enhanced understanding of the nerve regeneration processes and advances in NGCs design, polymers and fabrication strategies have led to developing modern NGCs with superior regeneration-conducive capacities. Current review focuses on the advances in surgical and engineering approaches to treat peripheral nerve injuries. We suggest the incorporation of endothelial cell growth promoting cues and factors into the NGC interior for its possible enhancement effects on the axonal regeneration process that may result in substantial functional outcomes.

Bone Augmentation of Peri-Implant Dehiscence Defects Using Multilaminated Small Intestinal Submucosa as a Barrier Membrane: An Experimental Study in Dogs

Objective

The aim of the study is to evaluate the effects of multilaminated small intestinal submucosa (mSIS) combined with bone substitute material to repair peri-implant defects during guided bone regeneration procedures.

Methods

Twelve implants were placed in bilateral lower premolars of three beagle dogs, and a peri-implant buccal bone defect (3 mm width and 4 mm height) was created at each implant site. A total of 12 sites were filled with a particulate bone substitute material and then randomly divided into three treatment groups: covered by mSIS membrane (mSIS group), covered by collagen membrane (BG group), and no treatment (control group), each group of four sites. After 12 weeks of healing, all of the animals were euthanized and dissected blocks were obtained for micro-computed tomography (micro-CT) and histological analyses.

Results

Micro-CT results revealed similar horizontal width of augmented tissue and new bone formation between mSIS and BG groups (P < 0.05). Histological analyses revealed that the differences in horizontal widths of newly formed bone and bone-to-implant contact between mSIS and BG groups were not significant (P > 0.05). All of these parameters were significantly different from those in the control group (P < 0.05).

Conclusions

These findings confirmed that mSIS combined with the bone substitute material enhanced bone regeneration in peri-implant defects, in a manner similar to that of a collagen membrane.

Protective mechanism of artemisinin on rat bone marrow-derived mesenchymal stem cells against apoptosis induced by hydrogen peroxide via activation of c-Raf-Erk1/2-p90rsk-CREB pathway

Background

Bone marrow-derived mesenchymal stem cell (BMSC) transplantation is one of the new therapeutic strategies for treating ischemic brain and heart tissues. However, the poor survival rate of transplanted BMSCs in ischemic tissue, due to high levels of reactive oxygen species (ROS), limits the therapeutic efficacy of this approach. Considering that BMSC survival may greatly enhance the effectiveness of transplantation therapy, development of effective therapeutics capable of mitigating oxidative stress-induced BMSC apoptosis is an important unmet clinical need.

Methods

BMSCs were isolated from the 4-week-old male Sprague Dawley rats by whole bone marrow adherent culturing, and the characteristics were verified by morphology, immunophenotype, adipogenic, and osteogenic differentiation potential. BMSCs were pretreated with artemisinin, and H₂O₂ was used to induce apoptosis. Cell viability was detected by MTT, FACS, LDH, and Hoechst 33342 staining assays. Mitochondrial membrane potential (ΔΨm) was measured by JC-1 assay. The apoptosis was analyzed by Annexin V-FITC/PI and Caspase 3 Activity Assay kits. ROS level was evaluated by using CellROX® Deep Red Reagent. SOD, CAT, and GPx enzymatic activities were assessed separately using Cu/Zn-SOD and Mn-SOD Assay Kit with WST-8, Catalase Assay Kit, and Total Glutathione Peroxidase Assay Kit. The effects of artemisinin on protein expression of BMSCs including p-Erk1/2, t-Erk1/2, p-c-Raf, p-p90^rsk, p-CREB, BCL-2, Bax, p-Akt, t-Akt, β-actin, and GAPDH were measured by western blotting.

Results

We characterized for the first time the protective effect of artemisinin, an anti-malaria drug, using oxidative stress-induced apoptosis in vitro, in rat BMSC cultures. We found that artemisinin, at clinically relevant concentrations, improved BMSC survival by reduction of ROS production, increase of antioxidant enzyme activities including SOD, CAT, and GPx, in correlation with decreased Caspase 3 activation, lactate dehydrogenase (LDH) release and apoptosis, all induced by H₂O₂. Artemisinin significantly increased extracellular-signal-regulated kinase 1/2 (Erk1/2) phosphorylation, in a concentration- and time-dependent manner. PD98059, the specific inhibitor of the Erk1/2 pathway, blocked Erk1/2 phosphorylation and artemisinin protection. Similarly, decreased expression of Erk1/2 by siRNA attenuated the protective effect of artemisinin. Additionally, when the upstream activator KRAS was knocked down by siRNA, the protective effect of artemisinin was also blocked. These data strongly indicated the involvement of the Erk1/2 pathway. Consistent with this hypothesis, artemisinin increased the phosphorylation of Erk1/2 upstream kinases proto-oncogene c-RAF serine/threonine-protein kinase (c-Raf) and of Erk1/2 downstream targets p90 ribosomal s6 kinase (p90^rsk) and cAMP response element binding protein (CREB). In addition, we found that the expression of anti-apoptotic protein B cell lymphoma 2 protein (BcL-2) was also upregulated by artemisinin.

Conclusion

These studies demonstrate the proof of concept of artemisinin therapeutic potential to improve survival in vitro of BMSCs exposed to ROS-induced apoptosis and suggest that artemisinin-mediated protection occurs via the activation of c-Raf-Erk1/2-p90^rsk-CREB signaling pathway.

Short-term use of resveratrol in alloplastic graft material applied with calvarial bone defects in rats

PURPOSE

The effects of resveratrol administration on calvarial bone defects with alloplastic graft material was investigated for osteoinductive reaction and bone development in rats.

METHODS

Healthy male rats were randomly divided into 3 groups consisting of 10 rats. Groups were as follows: control (defect) group, defect + graft group, and defect + graft + resveratrol group. A calvarial bone defect was created in all groups, alloplastic bone grafts were applied to the defect in the 2nd and 3rd group, resveratrol (5 mg/kg/day) was added to the drinking water of the animals following graft application for 28 days in the 3rd group.

RESULTS

Increase in osteoclasts and necrotic changes were observed histopathologically in the control group. In the 2nd group, reduction of inflammation, congestion of blood vessels, increased osteblastic activity, osteoinductive effect, progression of osteocyte development and increased collagen fibers in connective tissue were observed. In the 3rd group, osteoblasts seemed to secrete bone matrix and accelerate osteoinductive effect with increased osteopregenitor activity and positive osteopontin and osteonectin expressions.

CONCLUSION

Resveratrol treatment was thought to be an alternative and supportive drug for implant application by inducing new bone formation in the calvaral defect region as a result of short-term treatment.

A Biomimicking Polymeric Cryogel Scaffold for Repair of Critical-Sized Cranial Defect in a Rat Model

Mineralized polymeric cryogels with interconnective macroporous structure have demonstrated their potential as promising scaffolding material in bone tissue engineering. However, their capability in inducing osteogenic differentiation of mesenchymal stem cells (MSCs) in vitro and osteogenesis in vivo has not been explored yet. In this work, the roles of the mineralized cryogel on osteogenesis are systematically studied. Mineralized macroporous poly(ethylene glycol)-co-2-hydroxyethyl methacrylate cryogel promotes osteogenic differentiation of rat MSCs, particularly in upregulating the activity of alkaline phosphatase (ALP, ∼5.7-folds) and expression of related osteogenic gene markers (ALP ∼16-folds, osteocalcin ∼133-folds) at 14 days. In vivo implantation reveals that mineralized cryogels could promote fast osteogenesis and angiogenesis in critical-sized cranial bone defect of a Sprague-Dawley rat model in 4 weeks. The adsorption, entrapment, and concentration of osteogenic growth factors (bone morphogenetic protein 2) and angiogenesis growth factor (vascular endothelial growth factor [VEGF]) in the matrices in vivo may possibly participate in the process of osteogenesis and angiogenesis. Notably, the adsorption of larger amount of VEGF in nonmineralized cryogels facilitates obvious angiogenesis and comparable osteogenesis in bone defect in 8 weeks. Graphical abstract [Figure: see text] Impact Statement The current work reported the fabrication and characterization of a biomimicking mineralized polymeric cryogel as scaffolding material in bone regeneration. In addition to its three dimensional porous structure and the osteogenic potential, this biomimicking scaffold was also found to enhance the adsorption of biochemical cues, which in turn greatly promoted the angiogenesis as well as the tissue regeneration.

The effect of graft application and allopurinol treatment on calvarial bone defect in rats1

Purpose

To investigate the effects of allopurinol administration on osteoinductive reaction and bone development with graft material.

Methods

Thirty-six Wistar albino rats were divided into 3 groups. In the control group, calvarial bone defect was only created without any treatment. In the Defect + Graft group, allograft treatment was performed by forming 8 mm calvarial bone defect. In the Defect + Graft + Allopurinol group, alloplastic bone graft was placed in the calvarial bone defect and then, allopurinol (50 mg/kg/day) treatment was intraperitoneally applied for 28 days.

Results

Histopathological examination revealed inflammation, congestion in the vessels, and an increase in osteoclast cells in the defect area. We also observed that new osteocyte cells, increase in connective tissue fibers, and new bone trabeculae. Osteopontin expression was positive in osteoblast cells and lacunated osteocyte cells were located in the periphery of the new bone trabeculae. Osteopontin expression was also positive in osteoblasts and osteocytes cells of new bone trabeculae in the graft site.

Conclusion

It has been shown that allopurinol treatment in rat calvaria defects may induce osteoblastic activity, matrix development, mature bone cell formation and new bone formation when used with autogenous grafts.

METTL3 inhibits BMSC adipogenic differentiation by targeting the JAK1/STAT5/C/EBPβ pathway via an m6A-YTHDF2-dependent manner

Bone marrow stem cells (BMSCs) are multipotent stem cells that can regenerate mesenchymal tissues, such as adipose tissue, bone, and muscle. Recent studies have shown that N⁶-methyladenosine (m⁶A) methylation, one of the most prevalent epigenetic modifications, is involved in the development process. However, whether it plays roles in BMSC differentiation is still elusive. Here, we found that the deletion of m⁶A "writer" protein methyltransferase-like (METTL)3 in porcine BMSCs (pBMSCs) could promote adipogenesis and janus kinase (JAK)1 protein expression via an m⁶A-dependent way. Knockdown of METTL3 decreased mRNA m⁶A levels of JAK1, leading to enhanced YTH m⁶A RNA binding protein 2 (YTHDF2)-dependent JAK1 mRNA stability. We further demonstrated that JAK1 activated signal transducer and activator of transcription (STAT) 5 through regulation of its phosphorylation to bind to the promoter of CCAAT/enhancer binding protein (C/EBP) β, which could ultimately lead to a modulated adipogenic process. Collectively, our results reveal an orchestrated network linking the m⁶A methylation and JAK1/STAT5/C/EBPβ pathway in pBMSCs adipogenic differentiation. Our findings provide novel insights into the underlying molecular mechanisms of m⁶A modification in the regulation of BMSCs differentiating into adipocytes, which may pave a way to develop more effective therapeutic strategies in stem cell regenerative medicine and the treatment of obesity.-Yao, Y., Bi, Z., Wu, R., Zhao, Y., Liu, Y., Liu, Q., Wang, Y., Wang, X. METTL3 inhibits BMSC adipogenic differentiation by targeting the JAK1/STAT5/C/EBPβ pathway via an m⁶A-YTHDF2-dependent manner.

Bi-layered electrospun nanofibrous membrane with osteogenic and antibacterial properties for guided bone regeneration

Guided bone regeneration (GBR) membranes have the potential to prevent the invasion of epithelial and connective tissues as well as to maintain a stable space for facilitating the ingrowth of regenerative bone tissue. However, the bioactivity and regeneration potential of currently available membranes still need to be improved. In this study, a novel bi-layered membrane with both osteogenic and antibacterial functions was developed for GBR applications. The loose layer (LL) of the membrane was composed of conjugated electrospun poly (lactic-co-glycolic acid) (PLGA)/gelatin nanofibers incorporating dexamethasone-loaded mesoporous silica nanoparticles (DEX@MSNs), while the dense layer (DL) of the membrane consisted of traditionally electrospun PLGA nanofibers loaded with the broad-spectrum antibiotic doxycycline hyclate (DCH). Morphological results showed that the LL (DEX@MSNs/PLGA/Gel) membrane exhibited a porous and loosely packed structure, which was beneficial for cell adhesion and infiltration, while the DL (DCH/PLGA) membrane remained dense enough to act as a barrier. In vitro drug release tests indicated that both DEX and DCH followed a favorable sustained release profile. The cell viability evaluation suggested that the electrospun membranes possessed good cytocompatibility. Furthermore, in vitro osteogenesis analyses demonstrated that the DEX@MSNs/PLGA/Gel composite membrane possessed an enhanced osteoinductive capacity for rat bone marrow stem cells (BMSCs), which was verified by the increased alkaline phosphatase (ALP) activity, the enhanced calcium deposition, and the upregulated osteocalcin (OCN) expression. In vitro antimicrobial experiments revealed the effective antibacterial potency of the DCH/PLGA membrane. In conclusion, the prepared nanocarrier-incorporated bi-layered composite membrane with combined osteogenic and antibacterial properties may be a promising candidate for GBR application.

Amorphous carbon modification on implant surface: a general strategy to enhance osteogenic differentiation for diverse biomaterials via FAK/ERK1/2 signaling pathways

Amorphous carbon coatings enhance osteogenic differentiation via FAK/ERK1/2 signaling pathways.

Bioactive gel self-assembled from phosphorylate biomimetic peptide: A potential scaffold for enhanced osteogenesis

Bone morphogenetic protein-2 biomimetic peptide (BMPBP) is a potent osteoinductive cytokine and plays a critical role during bone regeneration. Efforts to prepare hydrogels with surface modification or physical absorption of bioactive molecules do not provide sufficient bioactivity to meet the requirements of clinical application. The goal of this study was to form a three-dimensional hydrogel comprised of BMP-2 core sequence oligopeptide, phosphoserine, a synthetic cell adhesion peptide (RGDS), and polyaspartic acid to synergistically promote osteogenesis. Experiments performed in vitro revealed that the peptide gel was conducive to adhesion and proliferation of rat marrow mesenchymal stem cells (rMSCs). In addition, RT-PCR analysis indicated that rMSCs allowed better expression of osteogenesis-related genes such as BMP-2, runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), osteocalcin (OCN), and osteopontin (OPN). Use of the rat cranial bone defects model with micro-CT 3D reconstruction showed that bone regeneration patterns occurred from one side edge toward the center of the area implanted with the prepared biomimetic peptide hydrogels, demonstrating significantly accelerated bone regeneration. This work will provide a basis to explore the further application potential of this bioactive scaffold.

Porous nanofibrous scaffold incorporated with S1P loaded mesoporous silica nanoparticles and BMP-2 encapsulated PLGA microspheres for enhancing angiogenesis and osteogenesis

Repair of bone defects remains a major clinical challenge due to inadequate or abnormal vascularization in bone substitutes, which commonly leads to inferior bone formation or bone nonunion. Therefore, healing of bone defects requires the coordinated processes of angiogenesis and osteogenesis. In this study, sphingosine-1-phosphate (S1P) was initially loaded into mesoporous silica nanoparticles (MSNs) to form angiogenic microcarriers, which were subsequently embedded into porous nanofibrous poly-l-lactide (PLLA) scaffolds during a thermally induced phase separation (TIPS) process, while bone morphogenetic protein-2 (BMP-2) was encapsulated into poly(lactic-co-glycolic acid) (PLGA) microspheres to obtain osteogenic microcarriers, which were then integrated onto a MSNs/PLLA nanofibrous scaffold by a post seeding method. The osteogenic and angiogenic activities of the resulting dual-bioactive factor containing scaffolds were evaluated both in vitro and in vivo. The simulated drug release studies indicated that both bioactive factors will be released simultaneously and continuously from the fabricated composite scaffold. Moreover, the ectopic bone formation results showed that the sustained release of S1P and BMP-2 from the composite scaffold resulted in a synergistic effect on blood vessel formation and bone regeneration. Taken together, the results showed the promising application of the dual-bioactive factor loaded nanofibrous scaffold for enhanced bone regeneration.

Use of an anionic collagen matrix made from bovine intestinal serosa for in vivo repair of cranial defects

Polymeric biomaterials composed of extracellular matrix components possess osteoconductive capacity that is essential for bone healing. The presence of collagen and the ability to undergo physicochemical modifications render these materials a suitable alternative in bone regenerative therapies. The objective of this study was to evaluate the osteogenic capacity of collagen-based matrices (native and anionic after alkaline hydrolysis) made from bovine intestinal serosa (MBIS). Twenty-five animals underwent surgery to create a cranial defect to be filled with native and anionic collagen matrixes, mmineralized and non mineralized. The animals were killed painlessly 6 weeks after surgery and samples of the wound area were submitted to routine histology and morphometric analysis. In the surgical area there was new bone formation projecting from the margins to the center of the defect. More marked bone neoformation occurred in the anionic matrices groups in such a way that permitted union of the opposite margins of the bone defect. The newly formed bone matrix exhibited good optical density of type I collagen fibers. Immunoexpression of osteocalcin by osteocytes was observed in the newly formed bone. Morphometric analysis showed a greater bone volume in the groups receiving the anionic matrices compared to the native membranes. Mineralization of the biomaterial did not increase its osteoregenerative capacity. In conclusion, the anionic matrix exhibits osteoregenerative capacity and is suitable for bone reconstruction therapies.

Biomimetic Composite Scaffold Containing Small Intestinal Submucosa and Mesoporous Bioactive Glass Exhibits High Osteogenic and Angiogenic Capacity

Biomaterials with excellent osteogenic and angiogenic activities are desirable to repair massive bone defects. Decellularized matrix from porcine small intestinal submucosa (SIS) has attracted particular attention for tissue regeneration because it has strong angiogenic effects and retains plentiful bioactive components. However, it has inferior osteoinductivity and osteoconductivity. In this study, we developed porous composite of SIS combined with mesoporous bioactive glass (SIS/MBG) with the goal of improving the mechanical and biological properties. SIS/MBG scaffolds showed uniform interconnected macropores (∼150 μm), high porosity (∼76%), and enhanced compressive strength (∼0.87 MPa). The proliferation and osteogenic gene expression (Runx2, ALP, Ocn, and Col-Iα) of rat bone marrow stromal cells (rBMSCs) as well as the proliferation, angiogenic gene expression (VEGF, bFGF, and KDR), and tube formation capacity of human umbilical vein endothelial cells (HUVECs) in SIS/MBG scaffolds were significantly upregulated compared with nonmesoporous bioactive glass (BG)-modified SIS (SIS/BG) and SIS-only scaffolds. Western blot analysis revealed that SIS/MBG induced rBMSCs to osteogenic differentiation through the activation of Wnt/β-Catenin signaling pathway, and SIS/MBG enhanced angiogenic activity of HUVEC through the activation of PI3k/Akt pathways. The in vivo results demonstrated that SIS/MBG scaffolds significantly enhanced new bone formation and neovascularization simultaneously in critical-sized rat calvarial defects as compared with SIS/BG and SIS. Collectively, the osteostimulative and angiostimulative biomimetic composite scaffold SIS/MBG represents an exciting biomaterial option for bone regeneration.

A Cell-Engineered Small Intestinal Submucosa-Based Bone Mimetic Construct for Bone Regeneration

Extracellular matrix (ECM)-ornamented biomaterials have attracted attention due to their high potential to improve the biofunctionality of original materials. It is thought that ECM with a bone mimetic microenvironment generated by the specific induction of osteoblasts would be more beneficial for bone regeneration than a regular ECM. In this study, we developed an osteogenic and mineralized ECM construct (Os/M-ECM-SIS) under the guidance of osteoblasts on a small intestinal submucosa (SIS) scaffold cotreated with icariin and calcium. The generated Os/M-ECM-SIS scaffolds exhibited similar morphology and inorganic components as natural bone and higher mechanical strength than ECM-SIS. Cell adhesion, proliferation, and differentiation of osteoblasts and fibroblasts were also enhanced in the cells cultured on the Os/M-ECM-SIS scaffolds. The Os/M-ECM-SIS scaffolds even promoted transdifferentiation of fibroblasts with an upregulation of osteogenic differentiation markers. In a calvarial defect model, new bone formation was greatly enhanced in defects implanted with the Os/M-ECM-SIS scaffolds compared with ECM-SIS scaffolds. Further study showed that the Os/M-ECM-SIS scaffolds promoted bone regeneration in vitro and in vivo via the Bmp/Smad-signaling pathway. Thus, this work proposes a valuable method for generating a mineralized bone mimetic scaffold with SIS as off-the-shelf bone graft substitute that provides an excellent osteogenic microenvironment, making it suitable for application in bone tissue engineering.

Enhanced bone repair induced by human adipose-derived stem cells on osteogenic extracellular matrix ornamented small intestinal submucosa

AIM

Our aim was to design an osteogenic extracellular matrix (ECM) coated bioscaffold and to apply it to critical bone defect repair with adipose-derived stem cells (ADSCs).

MATERIALS & METHODS

Morphology of scaffolds was scanned by scanning electron microscope. Cell adhesion, proliferation and osteogenic differentiation of ADSCs on ECM-small intestinal submucosa (SIS) were evaluated by immunofluorescences staining, cell counting kit-8 and real-time qPCR, respectively. A mouse calvarial defect model was used to assess effects on bone regeneration in vivo.

RESULTS

Abundant ECM was coated on SIS, which facilitated cell adhesion and proliferation of ADSCs. ECM-SIS induced osteogenic differentiation of ADSCs even without osteogenic inductive factors. Bone regeneration in vivo was enhanced by ECM-SIS + ADSCs via BMP/SMAD pathway.

CONCLUSION

This work suggested a biofabricated SIS scaffold coated with osteogenic ECM-facilitated bone regeneration with ADSCs synergistically.

In vivo investigation of tissue-engineered periosteum for the repair of allogeneic critical size bone defects in rabbits

Aim: The aim of the study was to evaluate the efficacy of tissue-engineered periosteum (TEP) in repairing allogenic bone defects in the long term. Materials & methods: TEP was biofabricated with osteoinduced rabbit bone marrow mesenchymal stem cells and porcine small intestinal submucosa (SIS). A total of 24 critical sized defects were created bilaterally in radii of 12 New Zealand White rabbits. TEP/SIS was implanted into the defect site. Bone defect repair was evaluated with radiographic and histological examination at 4, 8 and 12 weeks. Results: Bone defects were structurally reconstructed in the TEP group with mature cortical bone and medullary canals, however this was not observed in the SIS group at 12 weeks. Conclusion: The TEP approach can effectively restore allogenic critical sized defects, and achieve maturity of long-bone structure in 12 weeks in rabbit models.

Enhanced tissue remodelling efficacy of adipose-derived mesenchymal stem cells using injectable matrices in radiation-damaged salivary gland model

The present study was conducted to introduce the use of a delivery carrier for local transplantation of human adipose tissue-derived mesenchymal stem cells (AdMSCs) into the salivary gland (SG) and analyse its ability to enhance radioprotection of AdMSCs against irradiation (IR)-induced damage. An injectable porcine small intestinal submucosa (SIS) matrix was used as a cell delivery carrier, and human AdMSCs were contained within SIS hydrogel (AdMSC/SIS). After local injection into SGs of mice following local IR, morphological and functional changes were evaluated in the sham, vehicle [phosphate-buffered saline (PBS)], SIS, AdMSC and AdMSC/SIS groups. Local transplantation of AdMSC resulted in less fibrosis, regardless of the use of a carrier, but the AdMSC/SIS group showed more mucin-producing acini relative to those in the PBS group. Functional restoration of salivation capacity and salivary protein synthesis was achieved in AdMSC and AdMSC/SIS groups, with a greater tendency being observed in the AdMSC/SIS group. AdMSC treatment resulted in tissue remodelling with a greater number of salivary epithelial cells (AQP-5), SG progenitor cells (c-Kit), endothelial cells (CD31) and myoepithelial cells (α-SMA), among which endothelial and myoepithelial cells significantly increased in the AdMSC/SIS group relative to the AdMSC group. AdMSC treatment alleviated IR-induced cell death, and the anti-apoptotic and anti-oxidative effects of AdMSC were enhanced in the AdMSC/SIS group relative to the AdMSC group. These results suggest local transplantation of AdMSC improves tissue remodelling following radiation damage in SG tissue, and that use of a carrier enhances the protective effects of AdMSC-mediated cellular protection against IR via paracrine secretion. Copyright © 2016 John Wiley & Sons, Ltd.

A Gingiva-Derived Mesenchymal Stem Cell-Laden Porcine Small Intestinal Submucosa Extracellular Matrix Construct Promotes Myomucosal Regeneration of the Tongue

In the oral cavity, the tongue is the anatomic subsite most commonly involved by invasive squamous cell carcinoma. Current treatment protocols often require significant tissue resection to achieve adequate negative margins and optimal local tumor control. Reconstruction of the tongue while preserving and/or restoring its critical vocal, chewing, and swallowing functions remains one of the major challenges in head and neck oncologic surgery. We investigated the in vitro feasibility of fabricating a novel combinatorial construct using porcine small intestinal submucosa extracellular matrix (SIS-ECM) and human gingiva-derived mesenchymal stem cells (GMSCs) as a GMSC/SIS-ECM tissue graft for the tongue reconstruction. We developed a rat model of critical-sized myomucosal defect of the tongue that allowed the testing of therapeutic effects of an acellular SIS-ECM construct versus a GMSC/SIS-ECM construct on repair and regeneration of the tongue defect. We showed that the GMSC/SIS-ECM construct engrafted at the host recipient site, promoted soft tissue healing, and regenerated the muscular layer, compared to the SIS-ECM alone or nontreated defect controls. Furthermore, our results revealed that transplantation of the GMSC/SIS-ECM construct significantly increased the expression of several myogenic transcriptional factors and simultaneously suppressed the expression of type I collagen at the wounded area of the tongue. These compelling findings suggest that, unlike the tongue contracture and fibrosis of the nontreated defect group, transplantation of the combinatorial GMSC/SIS-ECM constructs accelerates wound healing and muscle regeneration and maintains the overall tongue shape, possibly by both enhancing the function of endogenous skeletal progenitor cells and suppressing fibrosis. Together, our findings indicate that GMSC/SIS-ECM potentially served as a myomucosal graft for tongue reconstruction postsurgery of head and neck cancer.