Tannic Acid-Modified Decellularized Tendon Scaffold with Antioxidant and Anti-Inflammatory Activities for Tendon Regeneration.

Tendon regeneration is greatly influenced by the oxidant and the inflammatory microenvironment. Persistent inflammation during the tendon repair can cause matrix degradation, tendon adhesion, and excessive accumulation of reactive oxygen species (ROS), while excessive ROS affect extracellular matrix remodeling and tendon integration. Herein, we used tannic acid (TA) to modify a decellularized tendon slice (DTS) to fabricate a functional scaffold (DTS-TA) with antioxidant and anti-inflammatory properties for tendon repair. The characterizations and cytocompatibility of the scaffolds were examined in vitro. The antioxidant and anti-inflammatory activities of the scaffold were evaluated in vitro and further studied in vivo using a subcutaneous implantation model. It was found that the modified DTS combined with TA via hydrogen bonds and covalent bonds, and the hydrophilicity, thermal stability, biodegradability, and mechanical characteristics of the scaffold were significantly improved. Afterward, the results demonstrated that DTS-TA could effectively reduce inflammation by increasing the M2/M1 macrophage ratio and interleukin-4 (IL-4) expression, decreasing the secretion of interleukin-6 (IL-6) and interleukin-1ß (IL-1ß), as well as scavenging excessive ROS in vitro and in vivo. In summary, DTS modified with TA provides a potential versatile scaffold for tendon regeneration.

Facilely Prepared Thirsty Granules Arouse Tough Wet Adhesion on Overmoist Wounds for Hemostasis and Tissue Repair.

Bioadhesives have been widely used in hemostasis and tissue repair, but the overmoist and wet nature of wound surface (due to the presence of blood and/or wound exudate) has led to poor wet adhesion of bioadhesives, which interrupts the continuous care of wounds. Here, a thirsty polyphenolic silk granule (Tan@SF-pwd-hydro), which absorbs blood and exudate to self-convert to robust bioadhesives (Tan@SF-gel-hydro) in situ, was facilely developed in this study for enhanced wet adhesion toward hemostasis and tissue repair. Tan@SF-pwd-hydro could shield wounds' wetness and immediately convert itself to Tan@SF-gel-hydro to seal wounds for hemorrhage control and wound healing. The maximum adhesiveness of Tan@SF-gel-hydro over wet pigskin was as high as 59.8 ± 2.1 kPa. Tan@SF-pwd-hydro is a promising transformative dressing for hemostasis and tissue repair since its hemostatic time was approximately half of that of the commercial hemostatic product, CeloxTM, and its healing period was much shorter than that of the commercial bioadhesive product, TegadermTM. This pioneering study utilized adverse wetness over wounds to arouse robust adhesiveness by converting thirsty granules to bioadhesives in situ, creatively turning adversity into opportunities. The facile fabrication approach also offers new perspectives for manufacturing sustainability of biomaterials.

Chitosan/silk fibroin nanofibers-based hierarchical sponges accelerate infected diabetic wound healing via a HClO self-producing cascade catalytic reaction.

The diabetic chronic wound healing is extremely restricted by issues such as hyperglycemia, excessive exudate and reactive oxygen species (ROS), and bacterial infection, causing significant disability and fatality rate. Herein, the chitosan/silk fibroin nanofibers-based hierarchical 3D sponge (CSSF-P/AuGCs) with effective exudate transfer and wound microenvironment modulation are produced by integrating cascade reactor (AuGC) into sponge substrates with parallel-arranged microchannels. When applied to diabetic wounds, the uniformly parallel-arranged microchannels endow CSSF-P/AuGCs with exceptional exudate absorption capacity, keeping the wound clean and moist; additionally, AuGCs efficiently depletes glucose in wounds to generate H2O2, which is then converted into HClO via cascade catalytic reaction to eliminate bacterial infection and reduce inflammation. Experiments in vitro demonstrated that the antibacterial activity of CSSF-P/AuGCs against S. aureus and E. coli was 92.7 and 94.27 %, respectively. Experiments on animals indicated that CSSF-P/AuGC could cure wounds in 11 days, displaying superior wound-healing abilities when compared to the commercial medication Tegaderm™. This versatile CSSF-P/AuGCs dressing may be an attractive choice for expediting diabetic wound healing with little cytotoxicity, providing a novel therapeutic method for establishing a favorable pathological microenvironment for tissue repair.

In situ generation of bioadhesives using dry tannic silk particles: a wet-adhesion strategy relying on removal of hydraulic layer over wet tissues for wound care.

Tissue adhesives have been widely used in biomedical applications. However, the presence of a hydrated layer on the surface of wet tissue severely hinders their adhesion capacities, resulting in ineffective wound treatment. To address this issue, a dry particle dressing (plas@SF/tann-hydro-pwd) capable of removing the hydrated layer and converting in situ to bioadhesives (plas@SF/tann-hydro-gel) was fabricated via simple physical mixing based on the hydrophobic-hydrogen bonding synergistic effect and Schiff-base reaction. It was found that the plas@SF/tann-hydro-gel bioadhesive, which was changed from plas@SF/tann-hydro-pwd dressing by adsorption of water, exhibited good wet adhesion to diverse biological tissues. In addition, the wet adhesion qualities of the plas@SF/tann-hydro-gel adhesive was studied under a variety of demanding conditions, including a wide range of temperatures, varying pH levels, highly concentrated salt solutions, and simulated fluids. Experiments on animals had showed that the adhesive plas@SF/tann-hydro-gel has superior wet adhesion qualities and superior wound healing properties compared to the commercial product Tegaderm™. This study develops a new wet-adhesion technique employing dry particle dressing to eliminate the hydrated layer over wet tissues for the in situ creation of gel bioadhesives for wound healing.

Constructing a highly bioactive tendon-regenerative scaffold by surface modification of tissue-specific stem cell-derived extracellular matrix.

Developing highly bioactive scaffold materials to promote stem cell migration, proliferation and tissue-specific differentiation is a crucial requirement in current tissue engineering and regenerative medicine. Our previous work has demonstrated that the decellularized tendon slices (DTSs) are able to promote stem cell proliferation and tenogenic differentiation in vitro and show certain pro-regenerative capacity for rotator cuff tendon regeneration in vivo. In this study, we present a strategy to further improve the bioactivity of the DTSs for constructing a novel highly bioactive tendon-regenerative scaffold by surface modification of tendon-specific stem cell-derived extracellular matrix (tECM), which is expected to greatly enhance the capacity of scaffold material in regulating stem cell behavior, including migration, proliferation and tenogenic differentiation. We prove that the modification of tECM could change the highly aligned surface topographical cues of the DTSs, retain the surface stiffness of the DTSs and significantly increase the content of multiple ECM components in the tECM-DTSs. As a result, the tECM-DTSs dramatically enhance the migration, proliferation as well as tenogenic differentiation of rat bone marrow-derived stem cells compared with the DTSs. Collectively, this strategy would provide a new way for constructing ECM-based biomaterials with enhanced bioactivity for in situ tendon regeneration applications.

Biomechanically and biochemically functional scaffold for recruitment of endogenous stem cells to promote tendon regeneration.

Tendon regeneration highly relies on biomechanical and biochemical cues in the repair microenvironment. Herein, we combined the decellularized bovine tendon sheet (DBTS) with extracellular matrix (ECM) from tendon-derived stem cells (TDSCs) to fabricate a biomechanically and biochemically functional scaffold (tECM-DBTS), to provide a functional and stem cell ECM-based microenvironment for tendon regeneration. Our prior study showed that DBTS was biomechanically suitable to tendon repair. In this study, the biological function of tECM-DBTS was examined in vitro, and the efficiency of the scaffold for Achilles tendon repair was evaluated using immunofluorescence staining, histological staining, stem cell tracking, biomechanical and functional analyses. It was found that tECM-DBTS increased the content of bioactive factors and had a better performance for the proliferation, migration and tenogenic differentiation of bone marrow-derived stem cells (BMSCs) than DBTS. Furthermore, our results demonstrated that tECM-DBTS promoted tendon regeneration and improved the biomechanical properties of regenerated Achilles tendons in rats by recruiting endogenous stem cells and participating in the functionalization of these stem cells. As a whole, the results of this study demonstrated that the tECM-DBTS can provide a bionic microenvironment for recruiting endogenous stem cells and facilitating in situ regeneration of tendons.

Enhancement of Migration and Tenogenic Differentiation of Macaca Mulatta Tendon-Derived Stem Cells by Decellularized Tendon Hydrogel.

Decellularized tendon hydrogel from human or porcine tendon has been manufactured and found to be capable of augmenting tendon repair in vivo. However, no studies have clarified the effect of decellularized tendon hydrogel upon stem cell behavior. In the present study, we developed a new decellularized tendon hydrogel (T-gel) from Macaca mulatta, and investigated the effect of T-gel on the proliferation, migration and tenogenic differentiation of Macaca mulatta tendon-derived stem cells (mTDSCs). The mTDSCs were first identified to have universal stem cell characteristics, including clonogenicity, expression of mesenchymal stem cell and embryonic stem cell markers, and multilineage differentiation potential. Decellularization of Macaca mulatta Achilles tendons was confirmed to be effective by histological staining and DNA quantification. The resultant T-gel exhibited highly porous structure or similar nanofibrous structure and approximately swelling ratio compared to the collagen gel (C-gel). Interestingly, stromal cell-derived factor-1 (SDF-1) and fibromodulin (Fmod) inherent in the native tendon extracellular matrix (ECM) microenvironment were retained and the values of SDF-1 and Fmod in the T-gel were significantly higher than those found in the C-gel. Compared with the C-gel, the T-gel was found to be cytocompatible with NIH-3T3 fibroblasts and displayed good histocompatibility when implanted into rat subcutaneous tissue. More importantly, it was demonstrated that the T-gel supported the proliferation of mTDSCs and significantly promoted the migration and tenogenic differentiation of mTDSCs compared to the C-gel. These findings indicated that the T-gel, with its retained nanofibrous structure and some bioactive factors of native tendon ECM microenvironment, represents a promising hydrogel for tendon regeneration.

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

BACKGROUND: Poor healing of the tendon-bone interface after rotator cuff repair is one of the main causes of surgical failure. Previous studies demonstrated that demineralized cortical bone (DCB) could improve healing of the enthesis. PURPOSE: To evaluate the outcomes of hierarchically demineralized cortical bone (hDCB) coated with stem cell-derived extracellular matrix (hDCB-ECM) in the repair of the rotator cuff in a rabbit model. STUDY DESIGN: Controlled laboratory study. METHODS: Tendon-derived stem cells (TDSCs) were isolated, cultured, and identified. Then, hDCB was prepared by the graded demineralization procedure. Finally, hDCB-ECM was fabricated via 2-week cell culture and decellularization, and the morphologic features and biochemical compositions of the hDCB-ECM were evaluated. A total of 24 rabbits (48 samples) were randomly divided into 4 groups: control, DCB, hDCB, and hDCB-ECM. All rabbits underwent bilateral detachment of the infraspinatus tendon, and the tendon-bone interface was repaired with or without scaffolds. After surgery, 8 rabbits were assessed by immunofluorescence staining at 2 weeks, and the others were assessed by micro-computed tomography (CT) examination, immunohistochemical staining, histological staining, and biomechanical testing at 12 weeks. RESULTS: TDSCs were identified to have universal stem cell characteristics including cell markers, clonogenicity, and multilineage differentiation. The hDCB-ECM contained 3 components (bone, partial DCB, and DCB coated with ECM) with a gradient of calcium and phosphorus elements, and the ECM had stromal cell-derived factor 1, biglycan, and fibromodulin. Macroscopic observations demonstrated the absence of infection and rupture around the enthesis. The results of immunofluorescence staining showed that hDCB-ECM promoted stromal cell recruitment. Results of micro-CT analysis, immunohistochemical staining, and histological staining showed that hDCB-ECM enhanced bone and fibrocartilage formation at the tendon-bone interface. Biomechanical analysis showed that the hDCB-ECM group had higher ultimate tensile stress and Young modulus than the DCB group. CONCLUSION: The administration of hDCB-ECM promoted healing of the tendon-bone interface. CLINICAL RELEVANCE: hDCB-ECM could provide useful information for the design of scaffolds to repair the tendon-bone interface, and further studies are needed to determine its effectiveness.

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

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

Influence of the integrity of tendinous membrane and fascicle on biomechanical characteristics of tendon-derived scaffolds.

The biomechanical characteristics of tendon grafts is essential for tendon reconstructive surgery due to its great role in providing a good mechanical environment for tendon healing and regeneration. In our previous studies, the decellularized tendon slices (DTSs) and decellularized bovine tendon sheets (DBTSs) scaffolds were successfully developed. However, the influence of the integrity of tendinous membrane (endotenon and epitenon) and fascicle on biomechanical characteristics of these two scaffolds was not investigated. In this study, we assessed the integrity of tendinous membrane and fascicle of the tendon derived scaffolds and its effect on the biomechanical characteristics. The results of histological staining indicated that the DBTSs had complete endotenon and epitenon, while DTSs had no epitenon at all, only part of endotenon was remained. Furthermore, the DBTSs, and DTSs with thickness of 900 µm had complete fascicles, while DTSs with thickness less than 600 µm had almost no complete fascicles. The fibrous configuration of epitenon was well-preserved in the surface of the DBTSs but the surface ultrastructure of the DTSs was aligned collagen fibers based on scanning electron microscopy examination. The results of transmission electron microscopy showed that there was no significant difference between the DBTSs and DTSs. Mechanically, the DBTSs and DTSs with thickness of 900 µm showed similar ultimate tensile strength and stiffness to native tendon segments (NTSs). The strain at break and suture retention strength of the DBTSs showed much higher than that of the DTSs (p < 0.05). Additionally, the DBTSs showed higher ultimate load than the DTSs when these scaffolds were sutured with NTSs (p < 0.05) through the modified Kessler technique based on a uniaxial tensile test. This study demonstrated that DTSs may be used as a patch for reinforcing tendon repair, while DBTSs may be used as a bridge for reconstructing tendon defects.

Enhancement of tenogenic differentiation of rat tendon-derived stem cells by biglycan.

Biglycan (BGN) has been identified as one of the critical components of the tendon-derived stem cells (TDSCs) niche and may be related to tendon formation. However, so far, no study has demonstrated whether the soluble BGN could induce the tenogenic differentiation of TDSCs in vitro. The aim of this study was to investigate the effect of BGN on the tenogenic differentiation of TDSCs. The proliferation and tenogenic differentiation of TDSCs exposed to different concentrations of BGN (0, 50, 100, and 500 ng/ml) were determined by the live/dead cell staining assay, CCK-8 assay, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot analysis. The BGN signaling pathway of TDSCs (with and without 50 ng/ml of BGN) was determined by western blot analysis and qRT-PCR analysis. At a concentration of 50 ng/ml, BGN increased the expression of the tenogenic markers THBS-4 and TNMD at both the messenger RNA (mRNA) and protein levels. Meanwhile, 50 ng/ml of BGN inhibited the expression of the chondrogenic and osteogenic markers SOX9, ACN, and RUNX2 at both the mRNA and protein levels. Moreover, BGN (50 ng/ml) affected the expression of the components of the extracellular matrix of TDSCs. Additionally, BGN activated the Smad1/5/8 pathway as indicated by an increase in phosphorylation and demonstrated by inhibition experiments. Upregulation in the gene expression of BMP-associated receptors (BMPRII, ActR-IIa, and BMPR-Ib) and Smad pathway components (Smad4 and 8) was observed. Taken together, BGN regulates tenogenic differentiation of TDSCs via BMP7/Smad1/5/8 pathway and this regulation may provide a basic insight into treating tendon injury.

Effects of hydrogen peroxide on biological characteristics and osteoinductivity of decellularized and demineralized bone matrices.

Due to the similar collagen composition and closely physiological relationship with soft connective tissues, demineralized bone matrices (DBMs) were used to repair the injured tendon or ligament. However, the osteoinductivity of DBMs would be a huge barrier of these applications. Hydrogen peroxide (H2 O2 ) has been proved to reduce the osteoinductivity of DBMs. Nevertheless, the biological properties of H2 O2 -treated DBMs have not been evaluated completely, while the potential mechanism of H2 O2 compromising osteoinductivity is also unclear. Hence, the purpose of this study was to characterize the biological properties of H2 O2 -treated DBMs and search for the proof that H2 O2 could compromise osteoinductivity of DBMs. Decellularized and demineralized bone matrices (DCDBMs) were washed by 3% H2 O2 for 12 h to fabricate the H2 O2 -treated DCDBMs (HPTBMs). Similar biological properties including collagen, biomechanics, and biocompatibility were observed between DCDBMs and HPTBMs. The immunohistochemistry staining of bone morphogenetic protein 2 (BMP-2) was negative in HPTBMs. Furthermore, HPTBMs exhibited significantly reduced osteoinductivity both in vitro and in vivo. Taken together, these findings suggest that the BMP-2 in DCDBMs could be the target of H2 O2 . HPTBMs could be expected to be used as a promising scaffold for tissue engineering. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

Stem Cell Extracellular Matrix-Modified Decellularized Tendon Slices Facilitate the Migration of Bone Marrow Mesenchymal Stem Cells.

It is highly desirable to develop a novel scaffold that can induce stem cell migration in tendon tissue engineering and regeneration. The objective of this study is to assess the effect of stem cell extracellular matrix-modified decellularized tendon slices (ECM-DTSs) on bone marrow mesenchymal stem cells (BMSCs) migration and explore the possible molecular mechanisms. Native ECM produced by BMSCs and tendon-derived stem cells (TDSCs) was deposited on DTSs, denoted as bECM-DTSs and tECM-DTSs, respectively, and the migration of BMSCs treated with the extracts from ECM-DTSs was studied. Almost all the seeded stem cells were removed from the stem cell-DTS composites, while ECM produced by stem cells completely covered the surface of the DTSs. Significantly higher levels of chemokines, including stromal cell-derived factor-1 (SDF-1) and monocyte chemotactic protein-1 (MCP-1) were released by ECM-DTSs than by bare DTSs (p < 0.05), according to ELISA, and tECM-DTSs exhibited the highest release within 72 h. bECM-DTSs and tECM-DTSs markedly improved BMSCs migration compared to bare DTSs, with tECM-DTSs yielding the best recruitment effects. The ECM-DTSs led to early cytoskeletal changes compared to bare DTSs (p < 0.05). Migration-related gene and protein expression was significantly up-regulated in BMSCs treated with ECM-DTSs via the PI3K/AKT signaling pathway (p < 0.05), indicating that ECM-DTSs could enhance BMSCs migration via the PI3K/AKT signal pathway, and the effect of tECM-DTSs on BMSCs migration is superior to that of bECM-DTSs. This may provide the experimental and theoretical evidence for using stem cell-derived ECM-modified scaffold as a novel approach to recruit stem cells.

Bridging Repair of Large Rotator Cuff Tears Using a Multilayer Decellularized Tendon Slices Graft in a Rabbit Model.

PURPOSE: The purpose of this study was to evaluate the efficacy of an extracellular matrix scaffold with multilayer decellularized tendon slices (MDTSs) for reconstructing large rotator cuff tears in a rabbit model. METHODS: Large defects in the infraspinatus tendons were created bilaterally in 36 rabbits. The graft group underwent bridging repair of the defects with the MDTSs grafts from Achilles tendons of adult beagle dogs, and the control group underwent repair with the autologous excised tendon. Specimens underwent histologic observation, biomechanical testing, and microcomputed tomography analysis at 2, 4, and 8 weeks after surgery. RESULTS: Histologic analysis confirmed that the MDTSs graft promoted cell ingrowth and tissue integration, and fibrocartilage and Sharpey fibers formed at the enthesis at 8 weeks. Accordingly, the MDTSs graft generated a histologic appearance similar to that of the autogenous tendon graft. Mechanical testing revealed a significant increase of the regenerated tendons in ultimate load and stiffness from 4 to 8 weeks postoperatively, which was similar to autologous tendon repair. Microcomputed tomography analysis demonstrated that the MDTSs graft promoted bone formation at the tendon-bone insertion, thus improving the mechanical properties of the repair tendon. CONCLUSIONS: The MDTSs graft used to bridge large rotator cuff defects in a rabbit model promoted host cell ingrowth, enhanced the remodeling of regenerated tendon, and promoted fibrocartilage formation, thus improving the biomechanical properties of the repaired tendon. This study thereby provides fundamental information for rotator cuff regeneration with the MDTSs graft. CLINICAL RELEVANCE: Rotator cuff regeneration using MDTSs grafts is a promising procedure for large rotator cuff tears.

Evaluation of Decellularized Bovine Tendon Sheets for Achilles Tendon Defect Reconstruction in a Rabbit Model.

BACKGROUND: Achilles tendon (AT) defects frequently occur in trauma and chronic injuries. Currently, no method can satisfactorily reconstruct the AT with completely restored function. PURPOSE: To evaluate the postoperative outcomes of AT defect reconstruction with decellularized bovine tendon sheets (DBTSs) in a rabbit model. STUDY DESIGN: Controlled laboratory study. METHODS: DBTSs were prepared from bovine tendons after compression, decellularization, antigen extraction, freeze drying, and sterilization. Platelet-rich plasma (PRP) was obtained by differential centrifugation. Sixty-three rabbits were used in this study, and the AT defect model was created bilaterally. All rabbits were divided into 3 groups (n = 21). In the DBTS group and the DBTS + PRP group, 2-cm-long AT was excised and reconstructed by DBTSs or PRP-treated DBTSs. In the control group, the rabbits underwent AT transection, and stumps were sutured. After surgery, all rabbits were assessed by ultrasonography and magnetic resonance imaging and then sacrificed for histological examination and biomechanical testing at 4, 8, or 12 weeks. RESULTS: Gross observations demonstrated the absence of immunologic incompatibility and rejection. Histological examination showed that DBTSs promoted host cell infiltration and new fibrous tissue integration as compared with the control group. In each group, there was an AT-like structure formation and aligned collagen fiber deposition at 12 weeks. Mechanical properties of the reconstructed AT were not significantly different among the 3 groups at 4, 8, and 12 weeks after surgery ( P > .05). Ultrasonography and magnetic resonance imaging results illustrated that the reconstructed AT from each group maintained remodeling, and there was no significant difference in the echogenicity scoring ( P > .05) and percentages of good and excellent ( P > .05) among the 3 groups. CONCLUSION: DBTSs, which retain the native tendon structure and bioactive factors, had the ability to remodel and integrate into the rabbit AT and improve the healing process. CLINICAL RELEVANCE: DBTSs could serve as an effective bioscaffold to reconstruct AT defects.

An engineered tendon/ligament bioscaffold derived from decellularized and demineralized cortical bone matrix.

Demineralized bone matrix (DBM), as an extracellular matrix (ECM), has had limited use as a medical replacement although studies have reported a possibility for its use in tendon or ligament tissue engineering. To be an acid-extracted organic matrix, DBM contains much of bone protein, with a small amount of inorganic solids and some cell debris. However, cell debris is a critical factor that triggers inflammatory reaction in clinical reconstructions using ECM. In this study, we used a protocol incorporating the use of detergent with nuclease treatment to prepare decellularized DBM (DCDBM). DNA quantification analysis and histological observation confirmed that cells were completely removed from DBM. The inherent ultrastructure of DBM was well preserved after decellularization as observed through scanning electron microscopy. Additionally, calcium and phosphorus were absent and the specific functional groups of collagen remained after decellularization. Moreover, 79.71% of the tensile strength of DBM was retained and the viscoelastic properties were similar to the ligament. Furthermore, DCDBM promoted the adhesion and proliferation of NIH-3T3 fibroblasts in vitro and triggered less inflammation response at 12 weeks subcutaneous implantation in a rat model. These results demonstrate that the DCDBM has the potential to be used for tendon and ligament replacement. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 468-478, 2018.

Fabrication and characterization of a decellularized bovine tendon sheet for tendon reconstruction.

Obtaining a performing decellularized tendon scaffold with proper dimensions and adequate availability is highly desirable. However, the combined study of complete decellularization and detailed characterization of native tendon extracellular matrix (ECM) from large animals is still lacking. In the present study, we developed a new decellularization protocol, including physical methods and enzymatic solutions for processing bovine Achilles tendons, and produced a decellularized bovine tendon sheet (DBTS) scaffold for tendon reconstruction. The decellularization effectiveness was demonstrated by DNA quantification and histological qualification. The removal of the alpha-gal epitopes was confirmed by ELISA analysis and immunohistochemical staining. After decellularization, there were no significant alterations of the native tendon extracellular matrix (ECM) properties, including the internal ultrastructure, biochemical compositions such as collagen, glycosaminoglycans (GAGs), basic fibroblast growth factor (bFGF) and transforming growth factor-ß1 (TGF-ß1), fibronectin and decorin, as well as substantial mechanical strength. Furthermore, the DBTS scaffold showed no cytotoxic and promoted the proliferation of NIH-3T3 fibroblasts in vitro. When implanted into rat subcutaneous tissue, the DBTS scaffold displayed excellent histocompatibility in vivo. Our results, while offering a new decellularization protocol for large tendons, can provide a promising biologic scaffold with a combination of mechanical strength and tendon ECM bioactive factors that may have many potential applications in tendon reconstruction. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2299-2311, 2017.

The utilization of decellularized tendon slices to provide an inductive microenvironment for the proliferation and tenogenic differentiation of stem cells.

The extracellular matrix (ECM) microenvironment for the stem cell niches, including but not limited to the biochemical composition, matrix topography, and stiffness, is crucial to stem cell proliferation and differentiation. The purpose of this study was to explore the capacity of the decellularized tendon slices (DTSs) to induce stem cell proliferation and tenogenic differentiation. Rat adult stem cells, including tendon-derived stem cells (TDSCs) and bone marrow-derived stem cells (BMSCs), were identified to have universal stem cell characteristics. The DTSs were found to retain the native tendon ECM microenvironment cues, including the inherent surface topography, well-preserved tendon ECM biochemical composition and similar stiffness to native tendon. When the TDSCs and BMSCs were cultured on the DTSs respectively, the LIVE/DEAD assay, alamarBlue® assay, scanning electron microscopy examination and qRT-PCR analysis demonstrated that the DTSs have the capacity to support these stem cells homogeneous distribution, alignment, significant proliferation and tenogenic differentiation. Taken together, the findings of this study indicate that the DTSs can provide a naturally inductive microenvironment for the proliferation and tenogenic differentiation of TDSCs and BMSCs, supporting the use of decellularized tendon ECM as a promising and valuable approach for tendon repair/reconstruction.

Rotator cuff repair using a decellularized tendon slices graft: an in vivo study in a rabbit model.

PURPOSE: Although varieties of surgical repair techniques and materials have been used to repair rotator cuff defects, re-tearing frequently occurs. The purpose of this study is to evaluate the postoperative outcomes of rotator cuff repairs with a decellularized tendon slices (DTSs) graft in a rabbit model. METHODS: Large defects in the infraspinatus tendons were created bilaterally in 21 rabbits. The graft group underwent reconstruction of the defects with the DTSs grafts, while the defect group did not undergo any treatment. The specimens underwent histological observation, biomechanical testing, and magnetic resonance imaging (MRI) detection at 4, 8, and 12 weeks after surgery. In addition, 2 rabbits that were not operated on were used for MRI detection as a normal reference. RESULTS: Histological analysis revealed that the graft promoted host cell ingrowth and tissue integration, and a tendon-like structure developed at 12 weeks. The ultimate tensile load had a significant difference between specimens at 4 and 12 weeks in the graft group, but there was no significant difference between the graft group and the defect group. In the graft group, the stiffness at 12 weeks was significantly greater than that at 4 or 8 weeks, and it was also greater than the stiffness in the defect group at 12 weeks. MRI demonstrated that the signal strength of the regenerative tissue from the graft group at 12 weeks was similar to that of normal infraspinatus tendon. CONCLUSION: The DTSs graft allowed for incorporation of host tendon and improved the biomechanical performance of the regenerative tendon. Therefore, the graft could be a promising bioscaffold to enhance the surgical repair of large rotator cuff defects and consequently improve the clinical outcome of rotator cuff tears.