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Tendon injuries can result in two major drawbacks. Adhesions to the surrounding tissue may limit the range of motion, while fibrovascular scar formation can lead to poor biomechanical outcomes. Prosthetic devices may help to mitigate those problems. Emulsion electrospinning was used to develop a novel three-layer tube based on the polymer DegraPol (DP), with incorporated insulin-like growth factor-1 (IGF-1) in the middle layer. Scanning electron microscopy was utilized to assess the fiber diameter in IGF-1 containing pure DP meshes. Further characterization was performed with Fourier Transformed Infrared Spectroscopy, Differential Scanning Calorimetry, and water contact angle, as well as through the assessment of mechanical properties and release kinetics from ELISA, and the bioactivity of IGF-1 by qPCR of collagen I, ki67, and tenomodulin in rabbit Achilles tenocytes. The IGF-1-containing tubes exhibited a sustained release of the growth factor up to 4 days and showed bioactivity by significantly upregulated ki67 and tenomodulin gene expression. Moreover, they proved to be mechanically superior to pure DP tubes (significantly higher fracture strain, failure stress, and elastic modulus). The novel three-layer tubes intended to be applied over conventionally sutured tendons after a rupture may help accelerate the healing process. The release of IGF-1 stimulates proliferation and matrix synthesis of cells at the repair site. In addition, adhesion formation to surrounding tissue can be reduced due to the physical barrier.

Liver diseases pose a big global health problem and liver failure may result from viral infection, overnutrition or tumors. Studying pathologic liver tissue demands for accurate and specific histological stainings and immunohistochemical labellings, including chromogenic and fluorescent approaches. Moreover, a reliable set of healthy liver stainings and labellings are required, to provide a baseline or reference for the pathological situation. Here, we used the liver tissue of a healthy rabbit and compared different histological key steps, such as paraffin embedding after formalin fixation versus cryopreservation; or an antigen retrieval (AR) step in processing paraffin sections versus the same procedure without AR; or chromogenic with fluorescent detection system, respectively. Moreover, we provide images of serial sections, where we stained the same morphological structure with different markers, including collagen I, collagen III, fibronectin, α-SMA, elastin, protease-activated receptor-2 (PAR-2) which is an inflammation-related marker, ki67 for proliferating cells, and orcein (as negative control for pathological aberrations like Wilson disease). Differences between conditions were quantitatively assessed by measuring the colour intensity. Generally, we observed that cryosections exhibited a stronger signal intensity in immunohistochemically labelled sections than in paraffin sections; however, the strong staining got slurred, which sometimes hampered proper identification of morphological structures at higher magnifications. Moreover, there was a clear increase in signal intensity for paraffin sections when an AR step was performed compared to condition without AR. Results for mouse isotype staining as a negative control clearly supported those findings. Different stainings of the portal triad, the central vein and the bile ducts revealed a clear-cut distribution of extracellular matrix components, with prominent fibronectin and elastin around the lumen of the central vein as well as a patchy PAR-2 expression. As for the bile ducts, complete absence of α-SMA and PAR-2 was found at the margins, however, collagen I expression and elastin were positive and showed a strong signal. Like this, we provide useful and valuable reference images for researchers using the rabbit liver model. It may help to decide which of the immunohistochemical protocols are valuable to reach a certain aim and which protocols lead to the best visualization of the target structure.

Tissue engineering of an osteochondral interface demands for a gradual transition of chondrocyte- to osteoblast-prevailing tissue. If stem cells are used as a single cell source, an appropriate cue to trigger the desired differentiation is the use of composite materials with different amounts of calcium phosphate. Electrospun meshes of poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/aCaP) in weight ratios of 100:0; 90:10, 80:20, and 70:30 were seeded with human adipose-derived stem cells (ASCs) and cultured in DMEM without chemical supplementation. After 2 weeks of static cultivation, they were either further cultivated statically for another 2 weeks (group 1), or placed in a Bose® bioreactor with a flow rate per area of 0.16 mL cm-2 min-1 (group 2). Markers for stem cell criteria, chondrogenesis, osteogenesis, adipogenesis and angiogenesis were analyzed by quantitative real-time PCR. Cell distribution, Sox9 protein expression and proteoglycans were assessed by histology. In group 2 (perfusion culture), chondrogenic Sox9 was upregulated toward the cartilage-mimicking side compared to pure PLGA. On the bone-mimicking side, Sox9 experienced a downregulation, which was confirmed on the protein level. Vice versa, expression of osteocalcin was upregulated on the bone-mimicking side, while it was unchanged on the cartilage-mimicking side. In group 1 (static culture), CD31 was upregulated in the presence of aCaP compared to pure PLGA, whereas Sox9 and osteocalcin expression were not affected. aCaP nanoparticles incorporated in electrospun PLGA drive the differentiation behavior of human ASCs in a dose-dependent manner. Discrete gradients of aCaP may act as promising osteochondral interfaces. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1833-1843, 2019.

Surgery of the chest wall is potentially required to cover large defects after removal of malignant tumours. Usually, inert and non-degradable Gore-Tex serves to replace the missing tissue. However, novel biodegradable materials combined with stem cells are available that stimulate the healing. Based on poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/aCaP) and pure PLGA, a dual layer biodegradable hybrid nanocomposite was generated. Mouse adipose-derived stem cells were cultered on electrospun disks (ASCs of C57BL/6), and biomechanical tests were performed. The cell-seeded scaffolds were engrafted in C57BL/LY5.1 mice to serve as a chest wall substitute. Cell invasion into the bi-layered material, extent of CD45+ cells, inflammatory response, neo-vascularization and ECM composition were determined at 1 and 2 months post-surgery, respectively. The bi-layered hybrid nanocomposite was stable after a 2-week in vitro culture, in contrast to PLGA/aCaP without a PLGA layer. There was a complete biointegration and good vascularization in vivo. The presence of ASCs attracted more CD45+ cells (hematopoietic origin) compared to cell-free scaffolds. Inflammatory reaction was similar for both groups (±ASCs) at 8 weeks. A bi-layered hybrid nanocomposite fabricated of electrospun PLGA/aCaP and a reinforcing layer of pristine PLGA is an ideal scaffold for chest wall reconstruction. It is stable and allows a proper host tissue integration. If ASCs are seeded, they attract more CD45+ cells, supporting the regeneration process., Scientific Reports, 9 (1), ISSN:2045-2322

Investigation and studies of pulmonary diseases and injuries require pre-clinical animal models. The rabbit lung model is widely used and allows for a diverse set of readouts. Among them, histology and immunohistochemistry are of invaluable merit because qualitative and quantitative information about tissue morphology and composition can be easily obtained. In this technical note, we performed several histological and immunohistochemical stainings in the rabbit healthy naïve lung tissue. Overnight formalin fixation with subsequent paraffin embedding was compared to cryopreservation with a subsequent 10-minute formalin fixation prior to staining. Antigen retrieval (AR) for paraffin embedded sections proved to enhance the corresponding signals compared to analogous staining without AR. Advantages and disadvantages of chromogenic versus immunofluorescence stainings were discussed. In addition, several morphological structures, such as the intrapulmonary bronchus with its mucosal folds, the pulmonary artery, the alveoli and the lymph nodes, were stained with various stainings at the same site in order to give a comprehensive picture of their composition. Besides Haematoxylin&Eosin and Elastica van Gieson staining, collagen I, collagen III, fibronectin, α-SMA, ki-67 and protease-activated receptor-2 (PAR-2) immunohistochemistry was performed. Collagen I, collagen III and fibronectin expression was positive at the outer rim of the pulmonary arteries, while the inner rim was collagen III positive. Moreover, the fibronectin staining in the intrapulmonary bronchus showed an opposite trend when compared to the collagen III staining. The alveoli exhibited PAR-2 expression, while PAR-2 was not expressed in lymph nodes of the healthy rabbit lung., Acta Histochemica, 122 (8), ISSN:0065-1281, ISSN:1618-0372

Silicone is an important material family used for various medical implants. It is biocompatible, but its bioinertness prevents cell attachment, and thus tissue biointegration of silicone implants. This often results in constrictive fibrosis and implant failure. Bioglass 45S5® (BG) could be a suitable material to alter the properties of silicone, render it bioactive and improve tissue integration. Therefore, BG micro- or nanoparticles were blended into medical-grade silicone and 2D as well as 3D structures of the resulting composites were analyzed in ovo by a chick chorioallantoic membrane (CAM) assay. The biomechanical properties of the composites were measured and the bioactivity of the composites was verified in simulated body fluid. The bioactivity of BG-containing composites was confirmed visually by the formation of hydroxyapatite through scanning electron microscopy as well as by infrared spectroscopy. BG stiffens as prepared non-porous composites by 13% and 36% for micro- and nanocomposites respectively. In particular, after implantation for 7 days, the Young's modulus had increased significantly from 1.20 ± 0.01 to 1.57 ± 0.03 MPa for microcomposites and 1.44 ± 0.03 to 1.69 ± 0.29 MPa to for nanocpmosites. Still, the materials remain highly elastic and are comparably soft. The incorporation of BG into silicone overcame the bioinertness of the pure polymer. Although the overall tissue integration was weak, it was significantly improved for BG-containing porous silicones (+72% for microcomposites) and even further enhanced for composites containing nanoparticles (+94%). These findings make BG a suitable material to improve silicone implant properties. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1180-1188, 2019.

A major problem after tendon laceration is the low mechanical strength of the repaired tissue. One viable strategy for improving the functional and biomechanical properties of ruptured and repaired tendons is the delivery of growth factors at the injury site. Here, bioactive and reversibly expandable double-layered emulsion and coaxially electrospun tubes made from biodegradable DegraPol® (DP) (polyester urethane), delivering platelet-derived growth factor BB (PDGF-BB), are explored as implants to improve tendon healing in a rabbit Achilles tendon full laceration model. In vitro studies showed that both emulsion and coaxially electrospun scaffolds allow sustained delivery of bioactive PDGF-BB with similar release kinetics (150-190 pg PDGF-BB/mg of DP scaffold) over a period of 30 days. In vivo assessment after three weeks showed that PDGF-BB delivery through the bioactive DP tubes increased the tensile strength of the treated tendons 2-fold without additional pro-fibrotic effects, i.e., cell hyperproliferation or increase in α-smooth muscle actin expression at the wound site. While no major differences in ECM composition at the wound site were observed for ± PDGF-BB treated samples, collagen I and III were upregulated and fibronectin was downregulated compared to native tendons. In areas away from the wound, increased fibronectin expression was observed qualitatively in regions with lower collagen I and III expression. Both types of bioactive DP tubes provided surgeon-friendly and stable implants to deliver bioactive molecules and positively affected the strength of the repaired tendons after 3 weeks, thus presenting promising bioactive implants for clinical applications in the tendon repair field.

Peritendinous fibrotic adhesions after tendon surgery are still a problem up-to-date. Approaches to overcome or at least minimize adhesion formation include implantation of barrier materials, application of lubricants or combinations of materials and functionalized drugs that are controllably released and support the healing tendon to glide and achieve the full range of motion after regeneration. Although a huge amount of different materials have been experimentally tested, the optimal strategy with respect to material and method has not yet been determined. In this review, we present a historical overview of physical barriers as well as liquid agents that have been used in order to prevent peritendinous adhesion formation. The materials are divided according to their first publication into two time frames; before and after 1980. There is no claim to include all materials tested neither will the “best” material be chosen; however, we present several materials that were experimentally tested in different animal trials as well as in clinical trials in contrast to other materials that were only tested once and disappeared from the assortment of anti-adhesives; which as such is a valuable information about its applicability for this purpose. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 212–228, 2015.

Although biomechanical tendon and ligament tissue properties are being improved during regeneration after rupture, laceration, and tendinopathies (tendinosis and tendinitis), the biomechanical characteristics of healthy native tendons and ligaments should be known in order to compare surgical and rehabilitation outcomes to a baseline. Such baseline values are presented in this chapter for humans as well as for animals. As preclinical studies often use animal models to investigate novel surgical techniques as well as implantation of tissue engineered constructs, there is an inevitable need to choose an appropriate animal model in terms of biomechanics. An overview of rabbit, sheep, mouse, rat, dog, pig, monkey, and horse tendon and ligament models is given and the models are not only discussed in terms of suitability to represent the human situation, they are also compared to each other and with respect to their practicability.

Biomechanical characterization of tendons and ligaments on all levels of structural hierarchy demands different experimental methods. Whole ex vivo specimen may be biomechanically characterized in classic static tensile testing machines, giving load–displacement or stress–strain curves where ultimate load, stiffness, maximum stress, and elastic modulus can be assessed. Collagen fiber and fascicle characterization may need additional techniques such as atomic force microscopy or transmission electron microscopy. Besides static tensile (and also compressive) testing, dynamic tests are in use in order to determine the fatigue behavior of the tissue under view. Finally in vivo biomechanical characterization is presented with ultrasound being one of the most often used noninvasive imaging methods.

The application of cells to support tendon and ligament healing is one promising option to improve the biomechanical properties of the regenerated tissues. Obviously, tenoblasts and tenocytes might be a useful cell source as they are the predominant cell types in healthy tendons and ligaments. However, also stem cells with their intrinsic capacity for self-renewal and lineage-specific differentiation might be supporting full tissue integration and an adequate generation of new tissue. As such, stem cells of different origin, such as bone marrow or adipose tissue, have been explored in tendon healing. Application methods may also be an important factor regulating the outcome; therefore, cells seeded on different constructs such as decellularized tendon tissue or synthetic polymers like poly(lactic- co -glycolic acid) have been explored and investigated in vitro and in vivo in terms of their biomechanical functionality and their capacity to form tendon- and ligament-like connective tissue. Also direct injection at the wound site or intravenous injection of cells with the intention to accelerate and support healing has been reported in preclinical studies. Here, we discuss different approaches and their biological and biomechanical outcome. Furthermore, an overview of current clinical practice is given.

There are many viable options to image tendons and ligaments. Depending on the structure under view, ultrasound, magnetic resonance imaging (MRI), light microscopy, fluorescence microscopy (FM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (X-ray-D), atomic force microscopy (AFM), or second-harmonic generation (SHG) is used. For macroscopic investigations including anatomical questions, ultrasound and MRI are preferred imaging methods, while for smaller entities such as fiber bundles, fascicles, or tenocytes, light microscopy, FM, and SEM are in use. Finally, on the collagen molecule level, X-ray-D, TEM, AFM, or SHG are the methods of choice. In this chapter, each methodology is introduced with respect to the physical background, and its application demonstrated in a large variety of reports dealing with tendon and ligaments. A special focus is set on biomechanical measurements based on imaging methods.

Cellular responses occurring as cascades of inflammatory cells and tenocytes immigrating the wound site orchestrate the healing process in lacerated tendons and ligaments. Time-dependent concentrations of cytokines accompany this very well-balanced sequence of inflammation, remodelling, and maturation in the healing tissue. Extrinsic healing (cells migrating from synovium or tendon sheath towards the wound site) and intrinsic healing (cells primarily from endotenon and epitenon contribute to wound healing) lead to regeneration. However, unwanted scar-like tissue may be formed, associated with an insufficient resolution of inflammation and excessive remodelling. Scar tissue exhibits lower biomechanical properties and is prone to rerupture. Ways to promote scarless healing are discussed. In addition, gene expression and growth factor levels as a function of time after injury are presented.

Tendons and ligaments are connective tissues that serve as the force transmitting entities and enable musculoskeletal motion. Typical features of normal tendon tissue are parallel-aligned collagen I fibers and tenocytes. Moreover, the extracellular matrix (ECM) is composed of proteoglycans, glycoproteins, and elastin. The tissue has almost no vessels and the nutrition as well as oxygen are supplied at the vascularized myotendinous and osteotendinous junctions. Growth factors such as transforming growth factor beta are important for tendon development, homeostasis, and regeneration. Structural changes upon aging and tendinopathy include the extent of vascularization (aging causes less tendinopathy and more vascularization), the ECM (age-related lower collagen content and in tendinopathy collagen disorganization), and the proteoglycan content (older tendons having less, tendinopathic tendons more proteoglycans), which will be addressed in detail in this chapter.

Collagen is the main component of native tendons and ligaments. Tissue-engineered constructs as well as tendon and ligament (TL collagen sponges, gels, films, or ribbons among others are used and different processing methods are currently investigated including cross-linking or extrusion. Biomechanical assessment of differently fabricated collagen-based scaffold materials is reported for in vitro studies, either cell-free or seeded with cells and either statically or dynamically treated. In addition, many studies report biomechanical outcomes of collagen scaffolds after implantation to close a full defect as well as augmentation devices in vivo. In this chapter, an overview of different strategies using collagen as a means for T&L reconstruction is presented and discussed.

The topic of emerging trends in a certain field of research is always bound to the actual situation. As books usually have quite a long production process, emerging trends in tendon and ligament healing in this chapter refer mostly to the situation of April 2016. At that time, it was found that reports and publications mostly dealt with combinations of earlier findings to improve tendon and ligament healing by the application of especially fabricated grafts with several features addressing antiadhesion, acceleration of healing processes, and stimulation of neo-angiogenesis, among others. Moreover, cellular approaches were being investigated where transduction approaches as well as the application of cell mixtures, platelet rich plasma, or whole blood were used and shown to have beneficial effects in terms of biomechanical properties of the regenerated tendons or ligaments.

Polymeric synthetic scaffold materials for tendon and ligament rupture repair and augmentation include inert and biodegradable materials. As for the inert materials such as polyethylene terephthalate, approaches of covering the surface with more biocompatible materials are investigated. On the other hand, for the biodegradable polymeric scaffolds like PLGA (poly(lactic- co -glycolic acid)), different processing methods are in use in order to tailor the biomechanical properties of the tendon and ligament grafts according to their future destination. Biomechanics of polymeric grafts depend on cell seeding, including the type of cell and its cultivation method (static or dynamic). Moreover, also appropriate (growth) factors or other biological components serving as tendon healing supportive entities may be incorporated in synthetic polymeric scaffold materials, and their release kinetics are investigated to be tuned according to their aim, mostly mimicking natural healing patterns.

In order to regenerate lacerated tendons and ligaments, one viable option is to transplant autologous tendon or ligament tissue (autograft). The problem going along with this approach is primarily limited availability. Therefore, also allogeneic tendon and ligament (T&L) tissue is in use, however, the tissue has to be decellularized before transplanting it to the defect site in order to avoid tissue rejection. Such decellularized T&L grafts can also be reseeded by autologous cells in order to facilitate later biointegration. These two processing steps, however, prolong the time window to have a graft ready. Finally, also xenografts are in use, again decellularized to avoid rejection by the host. In the following chapter, auto-, allo-, and xenografts are discussed and possible processing options such as in vitro preseeding, static versus dynamic cultivation, and incorporation of growth factors such as basal fibroblast growth factor, platelet-derived growth factor, or epidermal growth factor among others are presented.

Tendon rupture repair is a surgical field where improvements are still required due to problems such as repeat ruptures, adhesion formation and joint stiffness. In the current study, a reversibly expandable and contractible electrospun tube based on a biocompatible and biodegradable polymer was implanted around a transected and conventionally sutured rabbit Achilles tendon. The material used was DegraPol® (DP), a polyester urethane. To make DP softer, more elastic and surgeon-friendly, the synthesis protocol was slightly modified. Material properties of conventional and new DP film electrospun meshes are presented. At 12 weeks post-surgery, tenocyte and tenoblast density, nuclei and width, collagen fibre structure and inflammation levels were analyzed histomorphometrically. Additionally, a comprehensive histological scoring system by Stoll et al. (2011) was used to compare healing outcomes. Results showed that there were no adverse reactions of the tendon tissue following the implant. No differences were found whether the DP tube was applied or not for both traditional and new DP materials. As a result, the new DP material was shown to be an excellent carrier for delivery of growth factors, stem cells and other agents responsible for tendon healing.

In tendon rupture repair, improvements such as higher primary repair strength, anti-adhesion and accelerated healing are needed. We developed a potential carrier system of an electrospun DegraPol® tube, which was tightly implanted around a transected and conventionally sutured rabbit Achilles tendon. Histomorphometric analysis of the tendon tissue 12 weeks postoperation showed that the tenocyte density, tenocyte morphology and number of inflammation zones were statistically equivalent, whether or not DegraPol tube was implanted; only the collagen fibres were slightly less parallelly orientated in the tube-treated case. Comparison of rabbits that were operated on both hind legs with ones that were operated on only one hind leg showed that there were significantly more inflammation zones in the two-leg cases compared to the one-leg cases, while the implantation of a DegraPol tube had no such adverse effects. These findings are a prerequisite for using DegraPol tube as a carrier system for growth factors, cytokines or stem cells in order to accelerate the healing process of tendon tissue. Copyright © 2012 John Wiley & Sons, Ltd.

After tendon rupture repair, two main problems may occur: re-rupture and adhesion formation. Suitable non-murine animal models are needed to study the healing tendon in terms of biomechanical properties and extent of adhesion formation. In this study 24 New Zealand White rabbits received a full transection of the Achilles tendon 2 cm above the calcaneus, sutured with a 4-strand Becker suture. Post-surgical analysis was performed at 3, 6 and 12 weeks. In the 6-week group, animals received a cast either in a 180 deg stretched position during 6 weeks (adhesion provoking immobilization), or were re-casted with a 150 deg position after 3 weeks (adhesion inhibiting immobilization), while in the other groups (3 and 12 weeks) a 180 deg position cast was applied for 3 weeks. Adhesion extent was analyzed by histology and ultrasound. Histopathological scoring was performed according to a method by Stoll et al. (2011), and the main biomechanical properties were assessed. Histopathological scores increased as a function of time, but did not reach values of healthy tendons after 12 weeks (only around 15 out of 20 points). Adhesion provoking immobilization led to an adhesion extent of 82.7±9.7%, while adhesion inhibiting immobilization led to 31.9±9.8% after 6 weeks. Biomechanical properties increased over time, however, they did not reach full strength nor elastic modulus at 12 weeks post-operation. Furthermore, the rabbit Achilles tendon model can be modulated in terms of adhesion formation to the surrounding tissue. It clearly shows the different healing stages in terms of histopathology and offers a suitable model regarding biomechanics because it exhibits similar biomechanics as the human flexor tendons of the hand., Biology Open, 5 (9), ISSN:2046-6390

Background Perfusion bioreactors are used to solve problems in critical size bone tissue engineering. Biominerizable and biocompatible nanocomposites are suitable scaffold materials for this purpose because they offer mineral components in organic carriers. Human adipose derived stem cells (ASCs) can potentially be used to increase bone healing. Materials and methods Electrospun nanocomposite disks of poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/a-CaP) were seeded with ASCs and eight disks were stacked in a bioreactor running with normal culture. Under perfusion and uniaxial cyclic compression, load-displacement curves as a function of time were assessed. Stiffness and energy dissipation were recorded. Moreover, stem cell densities in the layers of the piled scaffold were determined as well as their morphologies and differentiation status. Results While the stiffness of the cell free constructs increased over time based on the transformation of the a-CaP nanoparticles into flake-like apatite, ASC-seeded constructs showed a constant stiffness. Stem cell density gradients had a linear increase from the bottom to the top of the pile ( r 2 >0.95). Stem cells were getting more roundish at higher flow rates. Some osteogenesis was found upon osteopontin immunostaining, while no endothelial cell differentiation and no chondrogenesis was triggered. Conclusions The fabrication of a critical size bone graft is presented based on a biominerizable bone-biomimetic nanocomposite with preserved stiffness when seeded with ASCs. The cell densities of ASCs inside the piled construct varied with a linear gradient. Beginning osteogenesis was triggered by the dynamic culture conditions including perfusion and compression.

One of the great challenges in surgical tendon rupture repair is to minimize peritendinous adhesions. In order to reduce adhesion formation, a physical barrier was applied to a sutured rabbit Achilles tendon, with two different immobilization protocols used postoperatively. Methods. Thirty New Zealand white rabbits received a laceration on the Achilles tendon, sutured with a 4-strand Becker suture, and half of the rabbits got a DegraPol tube at the repair site. While fifteen rabbits had their treated hind leg in a 180° stretched position during 6 weeks (adhesion provoking immobilization), the other fifteen rabbits were recasted with a 150° position after 3 weeks (adhesion inhibiting immobilization). Adhesion extent was analysed macroscopically, via ultrasound and histology. Inflammation was determined histologically. Biomechanical properties were analysed. Results. Application of a DegraPol tube reduced adhesion formation by approximately 20%—independently of the immobilization protocol. Biomechanical properties of extracted specimen were not affected by the tube application. There was no serious inflammatory reaction towards the implant material. Conclusions. Implantation of a DegraPol tube tightly set around a sutured tendon acts as a beneficial physical barrier and prevents adhesion formation significantly—without affecting the tendon healing process., BioMed Research International, 2014, ISSN:2314-6133, ISSN:2314-6141

Background Fractures with a critical size bone defect are associated with high rates of delayed- and non-union. The treatment of such complications remains a serious issue in orthopaedic surgery. Adipose derived stem cells (ASCs) combined with biomimetic materials can potentially be used to increase fracture healing. Nevertheless, a number of requirements have to be fulfilled; in particular, the insufficient vascularisation of the bone constructs. Here, the objectives were to study the impact of ASC-derived osteoblasts on ASC-derived endothelial cells in a 3D co-culture and the effect of 40 wt% of amorphous calcium phosphate nanoparticles on the proliferation and differentiation of ASC-derived endothelial cells when present in PLGA. Materials and methods Five primary ASC lines were differentiated towards osteoblasts (OBs) and endothelial cells (ECs) and two of them were chosen based on quantitative PCR results. Either a mono-culture of ASC-derived EC or a co-culture of ASC-derived EC with ASC-derived OB (1:1) was seeded on an electrospun nanocomposite of poly-(lactic-co-glycolic acid) and amorphous calcium phosphate nanoparticles (PLGA/a-CaP; reference: PLGA). The proliferation behaviour was determined histomorphometrically in different zones and the expression of von Willebrand Factor (vWF) was quantified. Results Independently of the fat source (biologic variability), ASC-derived osteoblasts decelerated the proliferation behaviour of ASC-derived endothelial cells in the co-culture compared to the mono-culture. However, expression of vWF was clearly stronger in the co-culture, indicating further differentiation of the ASC-derived EC into the EC lineage. Moreover, the presence of a-CaP nanoparticles in the scaffold slowed the proliferation behaviour of the co-culture cells, too, going along with a further differentiation of the ASC-derived OB, when compared to pure PLGA scaffolds. Conclusions This study revealed significant findings for bone tissue-engineering. Co-cultures of ASC-derived EC and ASC-derived OB stimulate each other's further differentiation. A nanocomposite with a-CaP nanoparticles offers higher mechanical stability, bioactivity and osteoconductivity compared to mere PLGA and can easily be seeded with pre-differentiated EC and OB.

Peritendinous fibrotic adhesions after tendon surgery are still a problem up-to-date. Approaches to overcome or at least minimize adhesion formation include implantation of barrier materials, application of lubricants or combinations of materials and functionalized drugs that are controllably released and support the healing tendon to glide and achieve the full range of motion after regeneration. Although a huge amount of different materials have been experimentally tested, the optimal strategy with respect to material and method has not yet been determined. In this review, we present a historical overview of physical barriers as well as liquid agents that have been used in order to prevent peritendinous adhesion formation. The materials are divided according to their first publication into two time frames; before and after 1980. There is no claim to include all materials tested neither will the "best" material be chosen; however, we present several materials that were experimentally tested in different animal trials as well as in clinical trials in contrast to other materials that were only tested once and disappeared from the assortment of anti-adhesives; which as such is a valuable information about its applicability for this purpose.

Static and dynamic high-frequency ultrasound of healing rabbit Achilles tendons were set in relationship to histomorphometric analyses at three and six weeks post-surgery.Twelve New Zealand White rabbits received a clean-cut Achilles tendon laceration (the medial and lateral Musculus gastrocnemius) and were repaired with a four-strand Becker suture. Six rabbits got additionally a tight polyester urethane tube at the repair site in order to vary the adhesion extent. Tendons were analysed by static and dynamic ultrasound (control: healthy contralateral legs). The ultrasound outcome was corresponded to the tendon shape, tenocyte and tenoblast density, tenocyte and tenoblast nuclei width, collagen fibre orientation and adhesion extent.The spindle-like morphology of healing tendons (ultrasound) was confirmed by the swollen epitenon (histology). Prediction of adhesion formation by dynamic ultrasound assessment was confirmed by histology (contact region to surrounding tissue). Hyperechogenic areas corresponded to acellular zones with aligned fibres and hypoechogenic zones to not yet oriented fibres and to cell-rich areas.These findings add new in-depth structural knowledge to the established non-invasive analytical tool, ultrasound.

Tendon rupture repair is a surgical field where improvements are still required due to problems such as repeat ruptures, adhesion formation and joint stiffness. In the current study, a reversibly expandable and contractible electrospun tube based on a biocompatible and biodegradable polymer was implanted around a transected and conventionally sutured rabbit Achilles tendon. The material used was DegraPol® (DP), a polyester urethane. To make DP softer, more elastic and surgeon-friendly, the synthesis protocol was slightly modified. Material properties of conventional and new DP film electrospun meshes are presented. At 12 weeks post-surgery, tenocyte and tenoblast density, nuclei and width, collagen fibre structure and inflammation levels were analyzed histomorphometrically. Additionally, a comprehensive histological scoring system by Stoll et al. (2011) was used to compare healing outcomes. Results showed that there were no adverse reactions of the tendon tissue following the implant. No differences were found whether the DP tube was applied or not for both traditional and new DP materials. As a result, the new DP material was shown to be an excellent carrier for delivery of growth factors, stem cells and other agents responsible for tendon healing.

In tendon rupture repair, improvements such as higher primary repair strength, anti-adhesion and accelerated healing are needed. We developed a potential carrier system of an electrospun DegraPol tube, which was tightly implanted around a transected and conventionally sutured rabbit Achilles tendon. Histomorphometric analysis of the tendon tissue 12 weeks postoperation showed that the tenocyte density, tenocyte morphology and number of inflammation zones were statistically equivalent, whether or not DegraPol tube was implanted; only the collagen fibres were slightly less parallelly orientated in the tube-treated case. Comparison of rabbits that were operated on both hind legs with ones that were operated on only one hind leg showed that there were significantly more inflammation zones in the two-leg cases compared to the one-leg cases, while the implantation of a DegraPol tube had no such adverse effects. These findings are a prerequisite for using DegraPol tube as a carrier system for growth factors, cytokines or stem cells in order to accelerate the healing process of tendon tissue.