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.

Higher Rate of Postoperative Complications in Delayed Achilles Tendon Repair Compared to Early Achilles Tendon Repair: A Meta-Analysis.

BACKGROUND: Some authors found that delayed repair of Achilles tendon ruptures achieved similar functional outcomes when compared with acute repair of Achilles tendon ruptures. The purpose of our study was to compare functional outcomes and complication rates of acute repair to delayed repair after Achilles tendon ruptures. METHODS: PubMed, Embase (Ovid) and the Cochrane Library were searched. RESULTS: For Achilles tendon rupture score (ATRS), the overall result revealed that there was no significant difference in ATRS between acute repair groups and delayed repair groups (P = 0.59). For Tegner scores, Halasi scores and Achilles tendon resting angle (ATRA), there was no significant difference between the two groups (P = 0.28, P = 0.47 and P = 0.68). There was no significant difference in the subjective assessment between acute repair groups and delayed repair groups (P = 0.84). However, delayed repair groups showed a higher incidence of complications than acute repair groups (P = 0.01). Subgroup analyses showed that the mean time from injury to surgery of delayed repair groups affect the pooled result substantially. For mean time less than 28d, there was no difference in the incidence of complications between acute repair groups and delayed repair groups (P = 0.09). However, for mean time more than 28d, delayed repair groups showed a higher incidence of complications than acute repair groups (P = 0.05). CONCLUSION: Our study showed delayed repair could obtain similar functional outcomes and subjective assessment when compared with acute repair. However, the rate of complications after delayed repair was higher than that of early repair. Further high-quality randomized controlled trials (RCT) are needed to evaluate the difference.

Fracture-Dedicated Prosthesis Promotes the Healing Rate of Greater Tuberosity in Reverse Shoulder Arthroplasty: A Meta-Analysis.

Introduction: Reverse shoulder arthroplasty (RSA) is becoming popular in the treatment of complex proximal humeral fractures (PHFs). Greater tuberosity healing may influence functional outcomes and range of motion (ROM) of shoulder after RSA. In addition, the design of prosthesis may impact the healing rate of greater tuberosity. The purpose of this study is to know: (1) does the healing of greater tuberosity affect the functional outcomes and ROM of shoulder? and (2) does the design of prosthesis affect the healing rate of greater tuberosity? Materials and Methods: PubMed, Ovid/Embase, and the Cochrane Library were searched for studies comparing the clinical outcomes between the healed groups and the non-healed groups after RSA. Results: For functional outcomes, the results showed that the healed group had better Constant scores (CSs) (p < 0.0001). For ROM, the healed group showed better flexion (p < 0.0001), abduction (p = 0.02), and external rotation (p < 0.00001) of shoulder. For the design of prosthesis, the mean healing rate of greater tuberosity (82.7%) in patients with fracture-dedicated prosthesis was higher than those (63.0%) in patients with standard prosthesis. Subgroup analyses showed that the CS (p = 0.12) and abduction (p = 0.96) of patients using fracture-dedicated prostheses were not different between the healed groups and the non-healed groups. Meta-regression showed that there was no significant relationship between the design of prosthesis and CS (p = 0.312), flexion (p = 0.422), or external rotation (p = 0.776). Conclusion: Our meta-analysis showed that the healed groups could obtain better functional outcomes and ROM than the non-healed groups. In addition, fracture-dedicated prostheses promoted the healing rate of greater tuberosity. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020157276, PROSPERO: CRD42020157276.

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.

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.

Combined use of Kirschner wires and hinged external fixator for capitellar and trochlear fractures: a minimum 24-month follow-up.

BACKGROUND: Open reduction and internal fixation is the adequate treatment for capitellar and trochlear fractures. Given the low incidence of this type of fractures, it is difficult to constitute a universally accepted method for fixation. Thus, we hypothesised that combined use of Kirschner wires (K-wires), absorbable rods and sutures for fixation and post-operative hinged external fixator for early rehabilitation exercise can restore elbow joint function well. METHODS: This retrospective study included 20 patients with a mean age of 48.3 (range 16-76) years. According to the Dubberley classification, fractures were classified on plain radiographs, computed tomography images and intra-operative findings. All patients were evaluated by the range of motion of the elbow and the Broberg-Morrey score. RESULTS: All fractures had healed without non-union, and the average time was 13.6 (range 8-17) weeks. The mean follow-up was 42.5 (range 24-80) months. The mean flexion was 117.1° (range 90°-135°), and the mean extension was 17.5° (range 0°-45°). The mean pronation was 74.4° (range 45°-85°), and the mean supination was 84.3° (range 60°-90°). The average Broberg-Morrey score was 86.2 (range 68-98) points with 10 excellent, 7 good and 3 fair results. CONCLUSION: K-wires, absorbable rods and sutures combined with hinged external fixator are feasible for fixation of capitellar and trochlear fractures. However, due to the absence of a control group (such as Herbert screw fixation), comparative studies are still needed to demonstrate the safety and reliability of K-wires for fixation.

Nanostructured titanium surfaces fabricated by hydrothermal method: Influence of alkali conditions on the osteogenic performance of implants.

Hydrothermal method is an easy-to-use approach for creating nanostructured surfaces on titanium (Ti). However, whether the alkali conditions of this method influence the osteogenic potential of the modified surfaces remains unknown. In this study, we fabricated nanostructured surfaces, termed the Ti-1, Ti-5, and Ti-10 groups, by using the hydrothermal method in 1 M, 5 M, and 10 M NaOH aqueous solutions, respectively. An untreated Ti surface served as a control. The osteogenic performance of modified surfaces was systemically investigated, including the proliferation and osteogenic differentiation of human osteoblast-like MG63 cells in vitro and the osteointegration of implants in a rabbit femoral condyle defect model. After hydrothermal treatment, the hydrophilicity of modified surfaces was greatly enhanced. The Ti-1 group showed a nanowire-like topography, while the Ti-5 and Ti-10 groups exhibited a nanopetal-like topography with different pore sizes. Compared with the untreated Ti surface, the modified surfaces showed good cytocompatibility and enhanced the osteogenic differentiation of MG-63 cells. Compared with the other modified surfaces, the Ti-5 group was the most favourable for the osteogenic differentiation of cells, showing higher levels of alkaline phosphatase activity, osteogenic gene expression, mineralization and osteoprotegerin secretion. Twelve weeks after implantation at the bone defects, the Ti-5 group showed superior peri-implant bone regeneration and higher peak push-out force than the other groups. Overall, this study revealed the crucial role of alkali conditions of hydrothermal method in modulating the material characteristics of modified surfaces and their osteogenic performance in vitro and in vivo, highlighting the need for optimizing the processing conditions of hydrothermal method for enhanced osteointegration.

The impact of associated injuries and fracture classifications on the treatment of capitellum and trochlea fractures: A systematic review and meta-analysis.

BACKGROUND: Capitellum and trochlea fractures are truly rare and the treatment is not fully appreciated. So we evaluate the impact of associated injuries and fracture classifications on elbow functional outcomes after open reduction and internal fixation. MATERIALS AND METHODS: PubMed, Embase, Ovid Medline, and the Cochrane Library were searched from January 1, 1974 to January 1, 2017. All English literature with the treatment of capitellum and trochlea fractures by open reduction and internal fixation were included. RESULTS: For associated injuries, the results suggested that the MEPI score of patients without associated injuries was higher than that of patients with associated injuries (P = 0.001). However, there was no significant difference in the arc of motion between the two groups (P = 0.052). For Bryan and Morrey classification, there was no significant difference in the MEPI score (P = 0.622) and in the arc of motion (P = 0.652) between type-I fractures and type-IV fractures. For Dubberley classification, there was significant difference only in the MEPI score between subtype-A fractures and subtype-B fractures (P = 0.005). CONCLUSION: The associated injury of fracture may have a negative impact on the functional outcomes of elbow. And Dubberley classification is more suitable to classify this kind of fracture. Furthermore, high-quality studies are required to attain robust evidence.

Appropriate excision time of heterotopic ossification in elbow caused by trauma.

OBJECTIVE: The aim of this study was to investigate the optimal timing for the resection of heterotopic ossification (HO) of the elbow. METHODS: We retrospectively reviewed 42 patients who were treated operatively for heterotopic ossification of the elbow from March 2010 to December 2014 at our institution. The patients were divided into early (before 12 months) and late (after 12 months) excision groups. In the early excision group (17 patients), the average time from the initial injury to HO excision was 7.4 (3-11) months, and in the late excision group (25 patients), the average time was 33.5 (12-240) months. Every patient was evaluated by range of motion (ROM), the Mayo Elbow Performance Score (MEPS), postoperative complications and HO recurrence. RESULTS: The preoperative mean ROM in the late excision group was greater than that of the early excision group, suggesting that the ROM is expected to increase even without surgery. Both early and late surgery increased ROM and MEPS, but early surgery improved ROM and MEPS more than late surgery did (p < .05). CONCLUSIONS: Early excision of HO can provide better elbow function, as indicated by ROM and MEPS. Considering that there were no notable differences in postoperative ROM and MEPS, HO recurrence, or postoperative complications, we concluded that early excision is safe and that the time from an elbow injury to surgery may be shortened. LEVEL OF EVIDENCE: Level III, therapeutic study.

Efficacy and safety of small intestinal submucosa in dural defect repair in a canine model.

Dural defects are a common problem, and inadequate dural closure can lead to complications. Several types of dural substitute materials have recently been discarded or modified owing to poor biocompatibility or mechanical properties and adverse reactions. The small intestinal submucosa (SIS) is a promising material used in a variety of applications. Based on the limitations of previous studies, we conducted an animal study to evaluate the efficacy and safety of the SIS in preclinical trials. Twenty-four male beagle dogs were subjected to surgical resection to produce dural defects. SIS or autologous dural mater was patched on the dural defect. Gross and histological evaluations were carried out to evaluate the efficacy and safety of the therapy. Our findings demonstrated that the SIS, which stimulated connective and epithelial tissue responses for dural regeneration and functional recovery without immunological rejection, could provide prolonged defect repair and prevent complications. The mechanical properties of the SIS could be adjusted by application of multiple layers, and the biocompatibility of the material was appropriate. Thus, our data suggested that this material may represent an alternative option for clinical treatment of dural defects.