Mechanical characteristics of native tendon slices for tissue engineering scaffold

Improving Mechanical Properties of Tendon Allograft through Rehydration Strategies: An In Vitro Study

Allogenic tendons grafts sourced from intrasynovial tendons are often used for tendon reconstruction. Processing is achieved through repetitive freeze-thaw cycles followed by lyophilization. Soaking the lyophilized tendon in saline (0.9%) for 24 h is the standard practice for rehydration. However, data supporting saline rehydration over the use of other hydrating solutions are scant. The purpose of the current study was to compare the effects of different rehydration solutions on biomechanical properties of lyophilized tendon allograft. A total of 36 canine flexor digitorum profundus tendons were collected, five freeze-thaw cycles followed by lyophilization were performed for processing, and then divided into three groups rehydrated with either saline solution (0.9%), phosphate-buffered saline (PBS), or minimum essential medium (MEM). Flexural stiffness, tensile stiffness, and gliding friction were evaluated before and after allograft processing. The flexural moduli in both fibrous and fibrocartilaginous regions of the tendons were measured. After lyophilization and reconstitution, the flexural moduli of both the fibrocartilaginous and non-fibrocartilaginous regions of the tendons increase significantly in the saline and MEM groups (p < 0.05). Compared to the saline and MEM groups, the flexural moduli of the fibrocartilaginous and non-fibrocartilaginous regions of tendons rehydrated with PBS are significantly lower (p < 0.05). Tensile moduli of rehydrated tendons are significantly lower than those of fresh tendons for all groups (p < 0.05). The gliding friction of rehydrated tendons is significantly higher than that of fresh tendons in all groups (p < 0.05). There is no significant difference in either tensile moduli or gliding friction between tendons treated with different rehydration solutions. These results demonstrate that allograft reconstitution can be optimized through careful selection of hydrating solution and that PBS could be a better choice as the impact on flexural properties is lower.

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.

Maintenance of Ligament Homeostasis of Spheroid-Colonized Embroidered and Functionalized Scaffolds after 3D Stretch

Anterior cruciate ligament (ACL) ruptures are usually treated with autograft implantation to prevent knee instability. Tissue engineered ACL reconstruction is becoming promising to circumvent autograft limitations. The aim was to evaluate the influence of cyclic stretch on lapine (L) ACL fibroblasts on embroidered scaffolds with respect to adhesion, DNA and sulphated glycosaminoglycan (sGAG) contents, gene expression of ligament-associated extracellular matrix genes, such as type I collagen, decorin, tenascin C, tenomodulin, gap junctional connexin 43 and the transcription factor Mohawk. Control scaffolds and those functionalized by gas phase fluorination and cross-linked collagen foam were either pre-cultured with a suspension or with spheroids of LACL cells before being subjected to cyclic stretch (4%, 0.11 Hz, 3 days). Stretch increased significantly the scaffold area colonized with cells but impaired sGAGs and decorin gene expression (functionalized scaffolds seeded with cell suspension). Stretching increased tenascin C, connexin 43 and Mohawk but decreased decorin gene expression (control scaffolds seeded with cell suspension). Pre-cultivation of functionalized scaffolds with spheroids might be the more suitable method for maintaining ligamentogenesis in 3D scaffolds compared to using a cell suspension due to a significantly higher sGAG content in response to stretching and type I collagen gene expression in functionalized scaffolds.

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.

Transforming Growth Factor Beta 3-Loaded Decellularized Equine Tendon Matrix for Orthopedic Tissue Engineering

Transforming growth factor beta 3 (TGFβ3) promotes tenogenic differentiation and may enhance tendon regeneration in vivo. This study aimed to apply TGFβ3 absorbed in decellularized equine superficial digital flexor tendon scaffolds, and to investigate the bioactivity of scaffold-associated TGFβ3 in an in vitro model. TGFβ3 could effectively be loaded onto tendon scaffolds so that at least 88% of the applied TGFβ3 were not detected in the rinsing fluid of the TGFβ3-loaded scaffolds. Equine adipose tissue-derived multipotent mesenchymal stromal cells (MSC) were then seeded on scaffolds loaded with 300 ng TGFβ3 to assess its bioactivity. Both scaffold-associated TGFβ3 and TGFβ3 dissolved in the cell culture medium, the latter serving as control group, promoted elongation of cell shapes and scaffold contraction (p < 0.05). Furthermore, scaffold-associated and dissolved TGFβ3 affected MSC musculoskeletal gene expression in a similar manner, with an upregulation of tenascin c and downregulation of other matrix molecules, most markedly decorin (p < 0.05). These results demonstrate that the bioactivity of scaffold-associated TGFβ3 is preserved, thus TGFβ3 application via absorption in decellularized tendon scaffolds is a feasible approach.

[A rapid histological preparation method for observation of morphology and composition distribution of tendon collagen fascicle and endotendinium]

Objective

To explore a rapid histological preparation method to observe morphology and composition distribution of tendon collagen fascicle and endotendinum.

Methods

Taking porcine superflexor tendon of foot as an example, tendons were sliced into sections with 6 μm by frozen section technology, after which general observation of the section integrity was carried out. After fixed with 10% neutral buffered formalin and performed with HE staining, the tissue integrity and ice crystal formation were observed under microscope. Sections were then divided into 5 groups by different methods of dyeing. Group A: Priodic acid-Shiff (PAS) staining; group B: Masson staining; group C: reticular fibers staining; group D: immunohistochemical and immunofluorescent staining of type Ⅲ collagen; group E: the sections were baked at 65℃ for 10 minutes and stained with Masson. The composition distribution of tendon collagen fascicle and endotendinum in different groups were observed.

Results

From general observation, the frozen section of tendon tissue was complete and continuous. Although the tissue integrity in the tendon sections could be seen and no ice crystal was formed, the composition distribution could not be identified by HE staining. The entire tendons in groups A, B, and C were dyed, and the composition distribution of collagen fascicle and endotendinum could not be identified. The endotendinum in group D was stained weakly positive for type Ⅲ collagen alone, and the two components were differentiated dyed but the contrast was not obvious. In group E, the collagen fascicle and endotendinium were differentiated dyed and the two components in tendon tissue were clearly visible.

Conclusion

The morphology and the composition distribution of tendon collagen fascicle and endotendinum can be characterized rapidly and accurately, using a combination of baking at 65℃ for 10 minutes and Masson staining after porcine superflexor tendons were sliced by frozen section technology.

Growth Factor-Mediated Tenogenic Induction of Multipotent Mesenchymal Stromal Cells Is Altered by the Microenvironment of Tendon Matrix

Age-related degenerative changes in tendon tissue represent a common cause for acute tendon pathologies. Although the regenerative potential of multipotent mesenchymal stromal cells (MSC) was reported to restore functionality in injured tendon tissue, cellular mechanisms of action remain partly unclear. Potential tenogenic differentiation of applied MSC is affected by various intrinsic and extrinsic factors. The current study presents an in vitro model to evaluate the combined extrinsic effects of decellularized equine tendon matrix, transforming growth factor beta 3 (TGFβ3) and bone morphogenetic protein 12 (BMP12) on the tenogenic fate of equine adipose tissue-derived MSC. Monolayer MSC cultures supplemented with TGFβ3 and BMP12 as well as MSC cultured on tendon matrix scaffolds preloaded with the growth factors were incubated for 3 and 5 days. Histological evaluation and real time reverse transcription polymerase chain reaction (RT-PCR) revealed that growth factor-mediated tenogenic induction of MSC was modified by the conditions of the surrounding microenvironment. While the gene expression pattern in monolayer cultures supplemented with TGFβ3 or TGFβ3 and BMP12 revealed an upregulation for collagen 1A2, collagen 3A1, tenascin c, scleraxis and mohawk (p < 0.05), the presence of tendon matrix led to an upregulation of decorin and osteopontin as well as to a downregulation of smad8 (p < 0.05). Preloading of scaffolds with either TGFβ3, or with TGFβ3 and BMP12 promoted a tenocyte-like phenotype and improved cell alignment. Furthermore, gene expression in scaffold culture was modulated by TGFβ3 and/or BMP12, with downregulation of collagen 1A2, collagen 3A1, decorin, scleraxis, smad8 and osteopontin, whereas gene expression of tenascin c was increased. This study shows that growth factor-induced tenogenic differentiation of equine MSC is markedly altered by topographical constraints of decellularized tendon tissue in vitro. While TGFβ3 represents an effective mediator for tenogenic induction, the role of BMP12 in tenogenesis may be of modulatory character and needs further evaluation.

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.

The effects of varying frequency and duration of mechanical stimulation on a tissue-engineered tendon construct

Decellularized, discarded human tissues, such as the human umbilical vein, have been widely utilized for tissue engineering applications, including tendon grafts. When recellularized, such natural scaffolds are cultured in 3D dynamic culture environments (bioreactor systems). For tendon tissue-engineered grafts, such systems often employ oscillatory mechanical stimulation in the form uniaxial tensile strain. The three main parameters of such stimulation are frequency, duration, and force. In this study we investigated the effects of changing the duration (0.5, 1, and 2 h/day) and frequency (0.5, 1, 2 cycles/min) of stimulation of a human umbilical vein seeded with mesenchymal stem cells cultured for up to 7 days. Strain of the construct was held constant at 2%. The highest proliferation rates were observed in the 0.5 h/day duration and 1 cycle/min frequency (203% increase) with a close second being 1 h/day and 1 cycle/min frequency (170% increase). Static cultures along with a 2 cycles/min frequency and a 2 h/day duration of stretching did not increase cellular proliferation significantly. Extracellular matrix quality and alignment of the construct fibers had a direct relation to cellularity and those groups with the highest cellularity improved the most. Gene expression indicated cellular activity consistent with tendon-like tissue remodeling. In addition, scleraxis, tenascin-C, and tenomodulin were upregulated in certain groups after 7 days, with osteoblast, chondrocyte, and adipocyte phenotypes depressed. The stimulation parameters investigated in this study indicated that slower frequencies and shorter durations were best for construct quality in early stage cultures.

The revitalisation of flexor tendon allografts with bone marrow stromal cells and mechanical stimulation: An ex vivo model revitalising flexor tendon allografts

Objectives

The present study describes a novel technique for revitalising allogenic intrasynovial tendons by combining cell-based therapy and mechanical stimulation in an ex vivo canine model.

Methods

Specifically, canine flexor digitorum profundus tendons were used for this study and were divided into the following groups: (1) untreated, unprocessed normal tendon; (2) decellularised tendon; (3) bone marrow stromal cell (BMSC)-seeded tendon; and (4) BMSC-seeded and cyclically stretched tendon. Lateral slits were introduced on the tendon to facilitate cell seeding. Tendons from all four study groups were distracted by a servohydraulic testing machine. Tensile force and displacement data were continuously recorded at a sample rate of 20 Hz until 200 Newton of force was reached. Before testing, the cross-sectional dimensions of each tendon were measured with a digital caliper. Young’s modulus was calculated from the slope of the linear region of the stress-strain curve. The BMSCs were labeled for histological and cell viability evaluation on the decellularized tendon scaffold under a confocal microscope. Gene expression levels of selected extracellular matrix tendon growth factor genes were measured. Results were reported as mean ± SD and data was analyzed with one-way ANOVAs followed by Tukey’s post hoc multiple-comparison test.

Results

We observed no significant difference in cross-sectional area or in Young’s modulus among the four study groups. In addition, histological sections showed that the BMSCs were aligned well and viable on the tendon slices after two-week culture in groups three and four. Expression levels of several extracellular matrix tendon growth factors, including collagen type I, collagen type III, and matrix metalloproteinase were significantly higher in group four than in group three (p < 0.05).

Conclusion

Lateral slits introduced into de-cellularised tendon is a promising method of delivery of BMSCs without compromising cell viability and tendon mechanical properties. In addition, mechanical stimulation of a cell-seeded tendon can promote cell proliferation and enhance expression of collagen types I and III in vitro.

Cite this article: J. H. Wu, A. R. Thoreson, A. Gingery, K. N. An, S. L. Moran, P. C. Amadio, C. Zhao. The revitalisation of flexor tendon allografts with bone marrow stromal cells and mechanical stimulation: An ex vivo model revitalising flexor tendon allografts. Bone Joint Res 2017;6:179–185. DOI: 10.1302/2046-3758.63.BJR-2016-0207.R1.

Rotator cuff repair augmentation in a rat model that combines a multilayer xenograft tendon scaffold with bone marrow stromal cells

HYPOTHESIS

A composite of multilayer tendon slices (COMTS) seeded with bone marrow stromal cells (BMSCs) may impart mechanical and biologic augmentation effects on supraspinatus tendon repair under tension, thereby improving the healing process after surgery in rats.

METHODS

Adult female Lewis rats (n = 39) underwent transection of the supraspinatus tendon and a 2-mm tendon resection at the distal end, followed by immediate repair to its bony insertion site under tension. Animals received 1 of 3 treatments at the repair site: (1) no augmentation, (2) COMTS augmentation alone, or (3) BMSC-seeded COMTS augmentation. BMSCs were labeled with a fluorescent cell marker. Animals were euthanized 6 weeks after surgery, and the extent of healing of the repaired supraspinatus tendon was evaluated with biomechanical testing and histologic analysis.

RESULTS

Histologic analysis showed gap formation between the repaired tendon and bone in all specimens, regardless of treatment. Robust fibrous tissue was observed in rats with BMSC-seeded COMTS augmentation; however, fibrous tissue was scarce within the gap in rats with no augmentation or COMTS-only augmentation. Labeled transplanted BMSCs were observed throughout the repair site. Biomechanical analysis showed that the repairs augmented with BMSC-seeded COMTS had significantly greater ultimate load to failure and stiffness compared with other treatments. However, baseline (time 0) data showed that COMTS-only augmentation did not increase mechanical strength of the repair site.

CONCLUSION

Although the COMTS scaffold did not increase the initial repair strength, the BMSC-seeded scaffold increased healing strength and stiffness 6 weeks after rotator cuff repair in a rat model.

A bioreactor system for in vitro tendon differentiation and tendon tissue engineering

There is significant clinical demand for functional tendon grafts in human and veterinary medicine. Tissue engineering techniques combining cells, scaffolds, and environmental stimuli may circumvent the shortcomings of traditional transplantation processes. In this study, the influence of cyclic mechanical stimulation on graft maturation and cellular phenotype was assessed in an equine model. Decellularized tendon scaffolds from four equine sources were seeded with syngeneic bone marrow-derived mesenchymal stem cells and subjected to 0%, 3%, or 5% strain at 0.33 Hz for up to 1 h daily for 11 days. Cells cultured at 3% strain integrated deep into their scaffolds, altered extracellular matrix composition, adopted tendon-like gene expression profiles, and increased construct elastic modulus and ultimate tensile strength to native levels. This bioreactor protocol is therefore suitable for cultivating replacement tendon material or as an in vitro model for studying differentiation of stem cells toward tendon.

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.

Laminar Tendon Composites with Enhanced Mechanical Properties

PURPOSE

A strong isotropic material that is both biocompatible and biodegradable is desired for many biomedical applications, including rotator cuff repair, tendon and ligament repair, vascular grafting, among others. Recently, we developed a technique, called "bioskiving" to create novel 2D and 3D constructs from decellularized tendon, using a combination of mechanical sectioning, and layered stacking and rolling. The unidirectionally aligned collagen nanofibers (derived from sections of decellularized tendon) offer good mechanical properties to the constructs compared with those fabricated from reconstituted collagen.

METHODS

In this paper, we studied the effect that several variables have on the mechanical properties of structures fabricated from tendon slices, including crosslinking density and the orientation in which the fibers are stacked.

RESULTS

We observed that following stacking and crosslinking, the strength of the constructs is significantly improved, with crosslinked sections having an ultimate tens ile strength over 20 times greater than non-crosslinked samples, and a modulus nearly 50 times higher. The mechanism of the mechanical failure mode of the tendon constructs with or without crosslinking was also investigated.

CONCLUSIONS

The strength and fiber organization, combined with the ability to introduce transversely isotropic mechanical properties makes the laminar tendon composites a biocompatiable material that may find future use in a number of biomedical and tissue engineering applications.

Effect of mechanical stimulation on bone marrow stromal cell-seeded tendon slice constructs: a potential engineered tendon patch for rotator cuff repair

Cell-based tissue engineered tendons have potential to improve clinical outcomes following rotator cuff repair, especially in large or massive rotator cuff tears, which pose a great clinical challenge. The aim of this study was to develop a method of constructing a functional engineered tendon patch for rotator cuff repair with cyclic mechanical stimulation. Decellularized tendon slices (DTSs) were seeded with BMSCs and subjected to cyclic stretching for 1, 3, or 7 days. The mechanical properties, morphologic characteristics and tendon-related gene expression of the constructs were investigated. Viable BMSCs were observed on the DTS after 7 days. BMSCs penetrated into the DTSs and formed dense cell sheets after 7 days of mechanical stretching. Gene expression of type I collagen, decorin, and tenomodulin significantly increased in cyclically stretched BMSC-DTS constructs compared with the unstrained control group (P < 0.05). The ultimate tensile strength and stiffness of the cyclically stretched tendon constructs were similar to the unstrained control group (P > 0.05). In conclusion, mechanical stimulation of BMSC-DTS constructs upregulated expression of tendon-related proteins, promoted cell tenogenic differentiation, facilitated cell infiltration and formation of cell sheets, and retained mechanical properties. The patch could be used as a graft to enhance the surgical repair of rotator cuff tears.

Factors influencing the long-term behavior of extracellular matrix-derived scaffolds for musculoskeletal soft tissue repair

Musculoskeletal connective tissues such as tendon, ligament, and cartilage possess a limited ability for self-repair. Tissue engineering seeks to use combinations of cells, bioactive molecules, and biomaterials to develop new treatment options for the repair or replacement of damaged tissues. The use of native extracellular matrix as scaffold material for tissue engineering has become increasingly attractive because such tissues can not only provide structural support, but also regulate cell behavior. Although demineralized bone matrix has long been recognized for its osteoinductive abilities, recent studies have identified the ability of cartilage and tendon extracellular matrices to stimulate the differentiation of mesenchymal or adipose-derived adult stem cells toward chondrogenic or tenogenic lineages, respectively. This review discusses the motivation for fabricating scaffolds from musculoskeletal tissues, the in vitro and in vivo efficacy of these tissue-derived scaffolds, and various processing techniques such as decellularization or cross-linking that can mitigate immunogenic responses, moderate the degradation profile, and enhance the mechanical properties of these constructs following long-term implantation in vivo.

Slicing, stacking and rolling: fabrication of nanostructured collagen constructs from tendon sections

A novel method for fabricating both multilayer stacked 2D and 3D tubular constructs composed of sheets of aligned collagen fibers is described. These structures are created by decellularizing native tendon and sectioning the material into thin sheets using a cryo-microtome. This fabrication method preserves the collagens natural strength as well as the fiber structure which would aid in directing aligned cell growth.

Functional characterization of detergent-decellularized equine tendon extracellular matrix for tissue engineering applications

Natural extracellular matrix provides a number of distinct advantages for engineering replacement orthopedic tissue due to its intrinsic functional properties. The goal of this study was to optimize a biologically derived scaffold for tendon tissue engineering using equine flexor digitorum superficialis tendons. We investigated changes in scaffold composition and ultrastructure in response to several mechanical, detergent and enzymatic decellularization protocols using microscopic techniques and a panel of biochemical assays to evaluate total protein, collagen, glycosaminoglycan, and deoxyribonucleic acid content. Biocompatibility was also assessed with static mesenchymal stem cell (MSC) culture. Implementation of a combination of freeze/thaw cycles, incubation in 2% sodium dodecyl sulfate (SDS), trypsinization, treatment with DNase-I, and ethanol sterilization produced a non-cytotoxic biomaterial free of appreciable residual cellular debris with no significant modification of biomechanical properties. These decellularized tendon scaffolds (DTS) are suitable for complex tissue engineering applications, as they provide a clean slate for cell culture while maintaining native three-dimensional architecture.