Effect of book-shaped acellular tendon scaffold with bone marrow mesenchymal stem cells sheets on bone-tendon interface healing

In Situ Construction of Morphologically Different Hydroxyapatite-Mineralized Structures on a Three-Dimensional Bionic Chitin Scaffold

Slow healing at the tendon-bone interface is a prominent factor in the failure of tendon repair surgeries. The development of functional biomaterials with 3D gradient structures is urgently needed to improve tendon-bone integration. The crystalline form of hydroxyapatite (HAP) has a crucial impact on cell behavior, which directly influences protein adsorption, such as bone morphogenetic protein 2, the adhesion, proliferation, and osteogenic differentiation with cells. This work aimed to generate gradient mineral structures in situ by stabilizing calcium and phosphate ions using a polymer-induced liquid precursor process. To regulate the crystalline growth of HAP at the interface of β-chitin, this work made use of the surface properties of the organic matrix found in cuttlefish bone. These techniques allowed us to prepare an organic-inorganic composite gradient scaffold comprising plate-like HAP mineralized in situ on the surface of the scaffold and fibrous HAP in the scaffold's interior. Organic-inorganic composite gradient materials are anticipated for use in tendon-bone healing produced via the in situ construction of gradient-distributed HAP mineralization layers having varying crystalline morphologies on chitin scaffolds that possess a three-dimensional bionic structure.

Cell Sheet Technology: An Emerging Approach for Tendon and Ligament Tissue Engineering

Tendon and ligament injuries account for a substantial proportion of disorders in the musculoskeletal system. While non-operative and operative treatment strategies have advanced, the restoration of native tendon and ligament structures after injury is still challenging due to its innate limited regenerative ability. Cell sheet technology is an innovative tool for tissue fabrication and cell transplantation in regenerative medicine. In this review, we first summarize different harvesting procedures and advantages of cell sheet technology, which preserves intact cell-to-cell connections and extracellular matrix. We then describe the recent progress of cell sheet technology from preclinical studies, focusing on the application of stem cell-derived sheets in treating tendon and ligament injuries, as well as highlighting its effects on mitigating inflammation and promoting tendon/graft-bone interface healing. Finally, we discuss several prerequisites for future clinical translation including the selection of appropriate cell source, optimization of preparation process, establishment of suitable animal model, and the fabrication of vascularized complex tissue. We believe this review could potentially provoke new ideas and drive the development of more functional biomimetic tissues using cell sheet technology to meet the needs of clinical patients.

Activating Mitochondrial Sirtuin 3 in Chondrocytes Alleviates Aging-Induced Fibrocartilage Layer Degeneration and Promotes Healing of Degenerative Rotator Cuff Injury

The present study aimed to examine the impact of mitochondrial sirtuin 3 (SIRT3) on the degenerative rotator cuff injury, which is a prevalent issue among the elderly population primarily due to aging-related tissue degradation. The study hypothesized that SIRT3, as a major deacetylase in mitochondria, is a significant factor in controlling the quality of mitochondria and the deterioration of fibrocartilage, a crucial component of the rotator cuff. Results showed that the aging process led to weakened biomechanical properties and degeneration of the fibrocartilage layer in mice, accompanied by a decrease in SIRT3 expression. SIRT3 activation ameliorated the aging-related disruption of chondrocyte phenotype and fibrocartilage degradation. SIRT3 activator honokiol improved the phenotype of senescent chondrocytes and promoted rotator cuff healing in aged mice through SIRT3 activation. In conclusion, the findings suggested that the decline in SIRT3 levels with age contributes to rotator cuff degeneration and chondrocyte senescence, and that SIRT3 activation through the use of honokiol is an effective approach for promoting rotator cuff healing in the elderly population.

Material Stiffness in Cooperation with Macrophage Paracrine Signals Determines the Tenogenic Differentiation of Mesenchymal Stem Cells

Stiffness is an important physical property of biomaterials that determines stem cell fate. Guiding stem cell differentiation via stiffness modulation has been considered in tissue engineering. However, the mechanism by which material stiffness regulates stem cell differentiation into the tendon lineage remains controversial. Increasing evidence demonstrates that immune cells interact with implanted biomaterials and regulate stem cell behaviors via paracrine signaling; however, the role of this mechanism in tendon differentiation is not clear. In this study, polydimethylsiloxane (PDMS) substrates with different stiffnesses are developed, and the tenogenic differentiation of mesenchymal stem cells (MSCs) exposed to different stiffnesses and macrophage paracrine signals is investigated. The results reveal that lower stiffnesses facilitates tenogenic differentiation of MSCs, while macrophage paracrine signals at these stiffnesses suppress the differentiation. When exposed to these two stimuli, MSCs still exhibit enhanced tendon differentiation, which is further elucidated by global proteomic analysis. Following subcutaneous implantation in rats for 2 weeks, soft biomaterial induces only low inflammation and promotes tendon-like tissue formation. In conclusion, the study demonstrates that soft, rather than stiff, material has a greater potential to guide tenogenic differentiation of stem cells, which provides comprehensive evidence for optimized bioactive scaffold design in tendon tissue engineering.

Bone marrow mesenchymal stem cell-derived exosomal microRNAs target PI3K/Akt signaling pathway to promote the activation of fibroblasts

BACKGROUND

Fibroblast plays a major role in tendon-bone healing. Exosomes derived from bone marrow mesenchymal stem cells (BMSCs) can activate fibroblasts and promote tendon-bone healing via the contained microRNAs (miRNAs). However, the underlying mechanism is not comprehensively understood. Herein, this study aimed to identify overlapped BMSC-derived exosomal miRNAs in three GSE datasets, and to verify their effects as well as mechanisms on fibroblasts.

AIM

To identify overlapped BMSC-derived exosomal miRNAs in three GSE datasets and verify their effects as well as mechanisms on fibroblasts.

METHODS

BMSC-derived exosomal miRNAs data (GSE71241, GSE153752, and GSE85341) were downloaded from the Gene Expression Omnibus (GEO) database. The candidate miRNAs were obtained by the intersection of three data sets. TargetScan was used to predict potential target genes for the candidate miRNAs. Functional and pathway analyses were conducted using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases, respectively, by processing data with the Metascape. Highly interconnected genes in the protein-protein interaction (PPI) network were analyzed using Cytoscape software. Bromodeoxyuridine, wound healing assay, collagen contraction assay and the expression of COL I and α-smooth muscle actin positive were applied to investigate the cell proliferation, migration and collagen synthesis. Quantitative real-time reverse transcription polymerase chain reaction was applied to determine the cell fibroblastic, tenogenic, and chondrogenic potential.

RESULTS

Bioinformatics analyses found two BMSC-derived exosomal miRNAs, has-miR-144-3p and has-miR-23b-3p, were overlapped in three GSE datasets. PPI network analysis and functional enrichment analyses in the GO and KEGG databases indicated that both miRNAs regulated the PI3K/Akt signaling pathway by targeting phosphatase and tensin homolog (PTEN). In vitro experiments confirmed that miR-144-3p and miR-23b-3p stimulated proliferation, migration and collagen synthesis of NIH3T3 fibroblasts. Interfering with PTEN affected the phosphorylation of Akt and thus activated fibroblasts. Inhibition of PTEN also promoted the fibroblastic, tenogenic, and chondrogenic potential of NIH3T3 fibroblasts.

CONCLUSION

BMSC-derived exosomes promote fibroblast activation possibly through the PTEN and PI3K/Akt signaling pathways, which may serve as potential targets to further promote tendon-bone healing.

Combined Verapamil-Polydopamine Nanoformulation Inhibits Adhesion Formation in Achilles Tendon Injury Using Rat Model

Introduction

Topical verapamil has been demonstrated to reduce the fibroproliferative scar. Therefore, it was hypothesized that topical verapamil could reduce adhesion formation after tendon repair. The current study aimed to examine the effects of verapamil-loaded polydopamine nanoparticles (VP-PDA NPs) on the adhesion formation of Achilles tendon laceration and repair in a rat model.

Methods

We randomly assigned 72 male Sprague-Dawley rats to the control, the PDA NPs, and the VP-PDA NPs groups (n = 24 per group). The quality of tendon healing was evaluated by the maximal tensile strength four and six weeks after surgery. The degree of tendon adhesion was scored on days 4, 15, 29, and 43 after surgery. The expressions of transforming growth factor-beta 1 (TGF-β1), vimentin, α-smooth muscle actin (α-SMA), and collagens type I and III were detected through Western blotting or immunohistochemistry at four weeks after surgery.

Results

In vitro release tests revealed that 61.3% of verapamil was released from VP-PDA NPs in four weeks. There was a significant increase in average failure to load in the VP-PDA NPs group (89.27 ± 5.09 N) compared with the PDA NPs group (65.52 ± 2.04 N) (p = 0.003) and the control group (74.52 ± 4.24 N) (p = 0.029). Adhesion scores were significantly reduced in the VP-PDA NPs group at six weeks (3.175 ± 0.08) and four weeks (3.35 ± 0.25) compared with the other groups. Moreover, VP-PDA NPs significantly reduced the expression of vimentin, α-SMA, TGF-β1, and collagens type I and III.

Conclusion

These data suggest that VP-PDA NPs reduced adhesion formation and enhanced tendon healing during rat tendon injury. Since topical verapamil has been used in clinics without side effects, VP-PDA NPs would have direct translation implications. However, its anti-adhesive effects on intrasynovial tendon injury must be examined.

TGF-β1-supplemented decellularized annulus fibrosus matrix hydrogels promote annulus fibrosus repair

Annulus fibrosus (AF) repair remains a challenge because of its limited self-healing ability. Endogenous repair strategies combining scaffolds and growth factors show great promise in AF repair. Although the unique and beneficial characteristics of decellularized extracellular matrix (ECM) in tissue repair have been demonstrated, the poor mechanical property of ECM hydrogels largely hinders their applications in tissue regeneration. In the present study, we combined polyethylene glycol diacrylate (PEGDA) and decellularized annulus fibrosus matrix (DAFM) to develop an injectable, photocurable hydrogel for AF repair. We found that the addition of PEGDA markedly improved the mechanical strength of DAFM hydrogels while maintaining their porous structure. Transforming growth factor-β1 (TGF-β1) was further incorporated into PEGDA/DAFM hydrogels, and it could be continuously released from the hydrogel. The in vitro experiments showed that TGF-β1 facilitated the migration of AF cells. Furthermore, PEGDA/DAFM/TGF-β1 hydrogels supported the adhesion, proliferation, and increased ECM production of AF cells. In vivo repair performance of the hydrogels was assessed using a rat AF defect model. The results showed that the implantation of PEGDA/DAFM/TGF-β1 hydrogels effectively sealed the AF defect, prevented nucleus pulposus atrophy, retained disc height, and partially restored the biomechanical properties of disc. In addition, the implanted hydrogel was infiltrated by cells resembling AF cells and well integrated with adjacent AF tissue. In summary, findings from this study indicate that TGF-β1-supplemented DAFM hydrogels hold promise for AF repair.

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Injectable DAFM derived hydrogel with mechanical property matching natural AF and sustained TGF-β1 release was developed.

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DAFM derived hydrogels promote AF cell proliferation, migration and ECM production.

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DAFM derived hydrogels display good integration with host AF tissue.

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DAFM derived hydrogels facilitate AF repair and restore intervertebral disc biomechanics.

Intermittent fasting promotes repair of rotator cuff injury in the early postoperative period by regulating the gut microbiota

Background

The repair of rotator cuff injury is affected by lifestyle and metabolic factors. Intermittent fasting (IF) can promote repair of damaged tissue by regulating intestinal flora, which provides an idea of therapy for rotator cuff injury. The aim of this study was to investigate the effects of fasting on rotator cuff repair after injury, and the role of intestinal flora or a single strain in this process.

Methods

Mice underwent rotator cuff injury were treated with intermittent fasting or fed ad libitum. Fasting began one month before surgery and continued until euthanasia. Fresh feces were collected at 2 weeks before surgery, on the day of surgery, and 2, 4, 8 weeks postoperatively for 16S rRNA microbiome sequencing. Supraspinatus tendon-humerus ​(SSTH) complex was collected at 2, 4 and 8 weeks after surgery. Live parabacteroides distasonis (Parabacteroides distasonis) was used for repair of rotator cuff injury, with equal amount of pasteurized P. distasonis (KPD) or sterile anaerobic phosphate buffer saline (PBS) as control. Biomechanical, radiological, histological analysis were used to assess the effect of rotator cuff repair.

Results

Biomechanical, radiological and histological analysis indicated that intermittent fasting significantly promoted the repair of rotator cuff injury in the early postoperative period (P ＜ 0.05), but significantly inhibited the repair of rotator cuff injury at 4 weeks postoperatively (P ＜ 0.05). 16S rRNA Microbiome sequencing result showed that P. distasonis was the species with the most obvious changes in intestinal flora of mice after fasting. The results of tensile test, X-ray analysis and histological analysis indicated that the live P. distasonis (LPD) significantly impaired the biomechanical properties, bone regeneration and fibrocartilage regeneration of enthesis postoperatively (P ＜ 0.05).

Conclusion

Intermittent fasting promoted repair of rotator cuff injury in the early postoperative period by regulating the gut microbiota, in which P. distasonis played an important role.

The translational potential of this article

Intermittent fasting (IF) may be a beneficial lifestyle for the repair of rotator cuff injury in the early postoperative period in clinical, and the influence of a certain strain on the repair of rotator cuff injury may also provide an idea for the treatment of rotator cuff injury in the future.

Engineering an enthesis-like graft for rotator cuff repair: An approach to fabricate highly biomimetic scaffold capable of zone-specifically releasing stem cell differentiation inducers

Rotator cuff (RC) attaches to humerus across a triphasic yet continuous tissue zones (bone-fibrocartilage-tendon), termed "enthesis". Regrettably, rapid and functional enthesis regeneration is challenging after RC tear. The existing grafts bioengineered for RC repair are insufficient, as they were engineered by a scaffold that did not mimic normal enthesis in morphology, composition, and tensile property, meanwhile cannot simultaneously stimulate the formation of bone-fibrocartilage-tendon tissues. Herein, an optimized decellularization approach based on a vacuum aspiration device (VAD) was developed to fabricate a book-shaped decellularized enthesis matrix (O-BDEM). Then, three recombinant growth factors (CBP-GFs) capable of binding collagen were synthesized by fusing a collagen-binding peptide (CBP) into the N-terminal of BMP-2, TGF-β3, or GDF-7, and zone-specifically tethered to the collagen of O-BDEM to fabricate a novel scaffold (CBP-GFs/O-BDEM) satisfying the above-mentioned requirements. After ensuring the low immunogenicity of CBP-GFs/O-BDEM by a novel single-cell mass cytometry in a mouse model, we interleaved urine-derived stem cell-sheets into this CBP-GFs/O-BDEM to bioengineer an enthesis-like graft. Its high-performance on regenerating enthesis was determined in a canine model. These findings indicate this CBP-GFs/O-BDEM may be an excellent scaffold for constructing enthesis-like graft to patch large/massive RC tears, and provide breakthroughs in fabricating graded interfacial tissue.

Mechanical Behavior of Biomimetic Oriented Cell Sheets from a Perspective of Living Materials

When compared to random cell organization, cell sheets with well-organized cell orientation are similar to natural tissues exhibiting better mechanical strength. Furthermore, as living materials, the mechanical strength of cell...

Effects of Platelet-Rich Plasma on Tendon-Bone Healing After Anterior Cruciate Ligament Reconstruction

OBJECTIVE

To investigate the effect of platelet-rich plasma on tendon-bone healing after anterior cruciate ligament reconstruction.

METHODS

This retrospective study included 85 patients (range, 18-50 years; mean age, 33.95 ± 10.53 years; male/female, 49/36) who underwent anterior cruciate ligament reconstruction using autologous hamstring tendons between August 2017 and June 2019 at our institute. The participants in the study group (n = 42) were injected with platelet-rich plasma at both ends of the tendon graft, while those in the control group (n = 43) received an injection of normal saline. Magnetic resonance imaging signal/noise quotient values of the femoral and tibial ends, knee Lysholm scores, and International Knee Documentation Committee scores were compared at 3, 6, and 12 months postoperatively.

RESULTS

The signal/noise quotient values of the femoral and tibial ends in both groups were higher at 6 months than at 3 and 12 months postoperatively. The signal/noise quotient values of the tibial end were significantly lower in the platelet-rich plasma group than in the normal saline group at all follow-up time points (P < 0.05). The signal/noise quotient values of the tibial and femoral ends in both groups were significantly different at 3, 6, and 12 months postoperatively (P < 0.05). Additionally, the signal/noise quotient values of the tibia were significantly lower than those of the femur in both groups (P < 0.05). The Lysholm and International Knee Documentation Committee scores were significantly better in the platelet-rich plasma group than in the normal saline group only at 3 months postoperatively. No complications, such as knee joint infection or vascular and nerve injuries, occurred in any of the 85 patients. The knee flexion of all patients were more than 90°, and the straight degree was 0°. No joint stiffness was observed in all patients.

CONCLUSION

Platelet-rich plasma can promote tendon-bone healing in grafts and can improve early postoperative knee joint function.

A Systematic Review of Tissue Engineering Scaffold in Tendon Bone Healing in vivo

Background: Tendon-bone healing is an important factor in determining the success of ligament reconstruction. With the development of biomaterials science, the tissue engineering scaffold plays an extremely important role in tendon-bone healing and bone tissue engineering. Materials and Methods: Electronic databases (PubMed, Embase, and the Web of Science) were systematically searched for relevant and qualitative studies published from 1 January 1990 to 31 December 2019. Only original articles that met eligibility criteria and evaluated the use of issue engineering scaffold especially biomaterials in tendon bone healing in vivo were selected for analysis. Results: The search strategy identified 506 articles, and 27 studies were included for full review including two human trials and 25 animal studies. Fifteen studies only used biomaterials like PLGA, collage, PCL, PLA, and PET as scaffolds to repair the tendon-bone defect, on this basis, the rest of the 11 studies using biological interventions like cells or cell factors to enhance the healing. The adverse events hardly ever occurred, and the tendon bone healing with tissue engineering scaffold was effective and superior, which could be enhanced by biological interventions. Conclusion: Although a number of tissue engineering scaffolds have been developed and applied in tendon bone healing, the researches are mainly focused on animal models which are with limitations in clinical application. Since the efficacy and safety of tissue engineering scaffold has been proved, and can be enhanced by biological interventions, substantial clinical trials remain to be done, continued progress in overcoming current tissue engineering challenges should allow for successful clinical practice.

Current Advances on the Regeneration of Musculoskeletal Interfaces

The regeneration of the musculoskeletal system has been widely investigated. There is now detailed knowledge about the organs composing this system. Research has also investigated the zones between individual tissues where physical, mechanical, and biochemical properties transition. However, the understanding of the regeneration of musculoskeletal interfaces is still lacking behind. Numerous disorders and injuries can degrade or damage tissue interfaces. Their inability to regenerate can delay the tissue repair and regeneration process, leading to graft instability, high morbidity, and pain. Moreover, the knowledge of the mechanism of tissue interface development is not complete. This review presents an overview of the most recent approaches of the regeneration of musculoskeletal interfaces, including the latest in vitro, preclinical, and clinical studies. Impact statement Interfaces between soft and hard tissues are ubiquitous within the body. These transition zones are crucial for joint motion, stabilisation and load transfer between tissues, but do not seem to regenerate well after injury or deterioration. The knowledge about their biology is vast, but little is known about their development. Various musculoskeletal disorders in combination with risk factors including aging and unhealthy lifestyle, can lead to local imbalances, misalignments, inflammation, pain and restricted mobility. Our manuscript reviews the current approaches taken to promote the regeneration of musculoskeletal interfaces through in vitro, pre-clinical and clinical studies.