Tissue-engineering approach to regenerating the intervertebral disc

In today's world there is an ever increasing incidence of low back pain, which is generally attributed to degeneration of the intervertebral disc (IVD) in those in their second or third decade of life. The most prevalent treatment modalities involve conservative methods (physical therapy and medications) or surgical fusion of the upper and lower vertebral bodies. In the last 10 years, there has been a surge of interest in applying tissue-engineering principles to treat spinal problems associated with the IVD. Tissue engineering provides many promising advantages to treating disc degeneration; it adopts a more biological and reparative approach, whereby the main goal is to restore the properties of the disc to its pre-degenerative state. This review outlines the physiology of the IVD and the etiology of disc degeneration. Much of the research carried out in the field of tissue engineering is based on three predominant constituents: cells, scaffolds, and signals. Thus, specific attention is given to these constituents and their potential use in repairing the IVD. Some of the significant challenges involved in IVD tissue engineering are also identified, and a brief discussion regarding possible future areas of research follows.     

韧带和肌腱的生物力学和力学生物学研究

国际韧带和肌腱研讨会(The International Symposium on Ligaments and Tendons,ISI&T)于2000年在美国佛罗里达州奥兰多市首次召开。研讨会的宗旨是引起对韧带和肌腱研究的重视,并为生物工程师、生物学家、临床医师提供一个可以分享、评论、讨论韧带和肌腱最新研究成果的论坛。从2000年起,国际韧带和肌腱研讨会已经开展了15届;每届研讨会上涌现了大量令人振奋的关于当前韧带和肌腱研究热点和未来挑战的讨论。多年来,韧带和肌腱领域内的研究数量大幅增加,研究质量不断提升。为纪念《医用生物力学》杂志创刊30周年,本文总结过去30年里韧带和肌腱研究的主要进展,包括组织力学、力学生物学、损伤与治愈机制、组织修复和再生。     

Mechanoreceptors of the ligaments and tendons around the knee

Proprioceptive inputs from the joints and limbs arise from mechanoreceptors in the muscles, ligaments and tendons. The knee joint has a wide range of movements, and proper neuroanatomical organization is critical for knee stability. Four ligaments (the anterior (ACL) and posterior (PCL) cruciate ligaments and the medial (MCL) and lateral (LCL) collateral ligaments) and four tendons (the semitendinosus (STT), gracilis (GT), popliteal (PoT), and patellar (PaT) tendons) from eight fresh frozen cadavers were harvested. Each harvested tissue was divided into its bone insertion side and its tendinous part for immunohistochemical examination using S100 staining. Freeman–Wyke's classification was used to identify the mechanoreceptors. The mechanoreceptors were usually located close to the bone insertion. Free nerve endings followed by Ruffini endings were the most common mechanoreceptors overall. No Pacini corpuscles were observed; free nerve endings and Golgi‐like endings were most frequent in the PCL (PCL‐PaT: P = 0.0.1, PCL‐STT: P = 0.00), and Ruffini endings in the popliteal tendon (PoT‐PaT: P = 0.00, Pot‐STT: P = 0.00, PoT‐LCL: P = 0.00, PoT‐GT: P = 0.00, PoT‐ACL: P = 0.09). The cruciate ligaments had more mechanoreceptors than the medial structures (MS) or the patellar tendon (CR‐Pat: P = 0.000, CR‐MS: P = 0.01). The differences in mechanoreceptor distributions between the ligaments and tendons could reflect the different roles of these structures in the dynamic coordination of knee motion. Clin. Anat. 29:789–795, 2016. © 2016 Wiley Periodicals, Inc.     

Wild-type transthyretin-derived amyloidosis in various ligaments and tendons

Transthyretin-derived amyloid deposition is commonly found in intercarpal ligaments of patients with senile systemic amyloidosis. However, the frequency of transthyretin-derived amyloid deposits in ligaments of other tissues remains to be elucidated. This study aimed to determine the frequency of amyloid deposition and the precursor proteins of amyloid found in orthopedic disorders. We studied 111 specimens from patients with carpal tunnel syndrome (flexor tenosynovium specimens), rotator cuff tears (rotator cuff tendon specimens), and lumbar canal stenosis (yellow ligament specimens). To identify amyloid precursor proteins, we used immunohistochemical staining with antibodies that react with transthyretin, immunoglobulin light chain, amyloid A protein, and β(2)-microglobulin. By means of Congo red staining, we identified 47 (42.3%) amyloid-positive samples, 39 of which contained transthyretin-derived amyloid (18 flexor tenosynovium specimens, 5 rotator cuff tendon specimens, and 16 yellow ligament specimens). Genetic testing and/or clinical findings suggested that all patients with transthyretin amyloid deposits did not have familial amyloidotic polyneuropathy. The occurrence of amyloid deposition in those tissues depended on age. These results suggest that transthyretin-derived amyloid deposits may occur more frequently in various ligaments and tendons than originally expected. In the future, such amyloid deposits may aid determination of the pathogenesis of ligament and tendon disorders in older patients.     

Fibrocartilage in tendons and ligaments — an adaptation to compressive load

Where tendons and ligaments are subject to compression, they are frequently fibrocartilaginous. This occurs at 2 principal sites: where tendons (and sometimes ligaments) wrap around bony or fibrous pulleys, and in the region where they attach to bone, i.e. at their entheses. Wrap-around tendons are most characteristic of the limbs and are commonly wider at their point of bony contact so that the pressure is reduced. The most fibrocartilaginous tendons are heavily loaded and permanently bent around their pulleys. There is often pronounced interweaving of collagen fibres that prevents the tendons from splaying apart under compression. The fibrocartilage can be located within fascicles, or in endo- or epitenon (where it may protect blood vessels from compression or allow fascicles to slide). Fibrocartilage cells are commonly packed with intermediate filaments which could be involved in transducing mechanical load. The ECM often contains aggrecan which allows the tendon to imbibe water and withstand compression. Type II collagen may also be present, particularly in tendons that are heavily loaded. Fibrocartilage is a dynamic tissue that disappears when the tendons are rerouted surgically and can be maintained in vitro when discs of tendon are compressed. Finite element analyses provide a good correlation between its distribution and levels of compressive stress, but at some locations fibrocartilage is a sign of pathology. Enthesis fibrocartilage is most typical of tendons or ligaments that attach to the epiphyses of long bones where it may also be accompanied by sesamoid and periosteal fibrocartilages. It is characteristic of sites where the angle of attachment changes throughout the range of joint movement and it reduces wear and tear by dissipating stress concentration at the bony interface. There is a good correlation between the distribution of fibrocartilage within an enthesis and the levels of compressive stress. The complex interlocking between calcified fibrocartilage and bone contributes to the mechanical strength of the enthesis and cartilage-like molecules (e.g. aggrecan and type II collagen) in the ECM contribute to its ability to withstand compression. Pathological changes are common and are known as enthesopathies.     

Inhibitors of collagenase in ligaments and tendons of rabbits immobilized for 4 weeks.

Our laboratories have previously measured the capacity for collagenase production by normal and immobilized rabbit periarticular connective tissues (PCT), i.e., anterior cruciate ligaments (ACL), medial collateral ligament (MCL) and patellar tendon (PT). Rabbit limbs were immobilized for 4 weeks and then the tissues were cultured for 4 days. Collagenase and inhibitor (TIMP) were measured in the medium. Collagenase activity was significantly decreased in the medium from all experimental tissues, relative to the levels in contralateral control tissues. On the other hand there was no significant change in inhibitor levels in the three experimental tissues. These results support the idea that collagenase is decreased due to decreased enzyme expression and not to increased inhibitor production.     

Early fetal development of the rotator interval region of the shoulder with special reference to topographical relationships among related tendons and ligaments

Purpose  

There is a little information on the early fetal development of the rotator interval region of the shoulder, particularly with regard to whether topographical relationships among the ligaments and tendons change during development.     

Physical activity and its influence on the repair process of medial collateral ligaments

The purpose of this investigation was to determine whether alterations in physical activity would modify the repair process of ligaments as evaluated by tissue DNA, collagen synthesis, and tensile strength. Compared to immobilization, progressive exercise markedly enhanced the healing process by inducing a more rapid return of tissue DNA, collagen synthesis, and separation force to within "normal" limits. Exercise also significantly increased wet and dry weights of repaired ligaments whereas immobilization markedly decreased these measurements because of the change in total collagen content. However, it remains uncertain whether progressive exercise can cause a shift in the equilibrium rates between collagen synthesis and collagen degradation.     

Where tendons and ligaments meet bone: attachment sites ('entheses') in relation to exercise and/or mechanical load

Entheses (insertion sites, osteotendinous junctions, osteoligamentous junctions) are sites of stress concentration at the region where tendons and ligaments attach to bone. Consequently, they are commonly subject to overuse injuries (enthesopathies) that are well documented in a number of sports. In this review, we focus on the structure-function correlations of entheses on both the hard and the soft tissue sides of the junction. Particular attention is paid to mechanical factors that influence form and function and thus to exploring the relationship between entheses and exercise. The molecular parameters indicative of adaptation to mechanical stress are evaluated, and the basis on which entheses are classified is explained. The application of the 'enthesis organ' concept (a collection of tissues adjacent to the enthesis itself, which jointly serve the common function of stress dissipation) to understanding enthesopathies is considered and novel roles of adipose tissue at entheses are reviewed. A distinction is made between different locations of fat at entheses, and possible functions include space-filling and proprioception. The basic anchorage role of entheses is considered in detail and comparisons are explored between entheses and other biological 'anchorage' sites. The ability of entheses for self-repair is emphasized and a range of enthesopathies common in sport are reviewed (e.g. tennis elbow, golfer's elbow, jumper's knee, plantar fasciitis and Achilles insertional tendinopathies). Attention is drawn to the degenerative, rather than inflammatory, nature of most enthesopathies in sport. The biomechanical factors contributing to the development of enthesopathies are reviewed and the importance of considering the muscle-tendon-bone unit as a whole is recognized. Bony spur formation is assessed in relation to other changes at entheses which parallel those in osteoarthritic synovial joints.     

Heal thyself: using endogenous regeneration to repair bone

Bone has the capacity to repair itself after an injury, and this occurs in normal fracture repair. This reparative process can be harnessed to regenerate segments of bone using distraction osteogenesis, in which the healing bone is slowly stretched. The use of animal models is identifying the important sources of cells for this endogenous bone regeneration, signaling molecules that regulate this reparative process, and the environmental cues important for success bone regeneration. A more complete understanding of the cells and pathways involved in this process can be applied to improve the outcome of distraction osteogenesis and to the development of methods to enhance endogenous bone regeneration.     

Stem cells in lung repair and regeneration

Repair or regeneration of defective lung tissue would be of great clinical use. Potential cellular sources for the regeneration of lung tissue in vivo or lung tissue engineering in vitro include endogenous pulmonary stem cells, extrapulmonary circulating stem cells and embryonic stem cells. This review summarizes the recent research on each of these stem cell types and their potential for use in the treatment of lung injury and disease.     

Music facilitate the neurogenesis, regeneration and repair of neurons

Experience has shown that therapy using music for therapeutic purposes has certain effects on neuropsychiatric disorders (both functional and organic disorders). However, the mechanisms of action underlying music therapy remain unknown, and scientific clarification has not advanced. While that study disproved the Mozart effect, the effects of music on the human body and mind were not disproved. In fact, more scientific studies on music have been conducted in recent years, mainly in the field of neuroscience, and the level of interest among researchers is increasing. The results of past studies have clarified that music influences and affects cranial nerves in humans from fetus to adult. The effects of music at a cellular level have not been clarified, and the mechanisms of action for the effects of music on the brain have not been elucidated. We propose that listening to music facilitates the neurogenesis, the regeneration and repair of cerebral nerves by adjusting the secretion of steroid hormones, ultimately leading to cerebral plasticity. Music affects levels of such steroids as cortisol (C), testosterone (T) and estrogen (E), and we believe that music also affects the receptor genes related to these substances, and related proteins. In the prevention of Alzheimer's disease and dementia, hormone replacement therapy has been shown to be effective, but at the same time, side effects have been documented, and the clinical application of hormone replacement therapy is facing a serious challenge. Conversely, music is noninvasive, and its existence is universal and mundane. Thus, if music can be used in medical care, the application of such a safe and inexpensive therapeutic option is limitless.     

56例关节镜下同种异体肌腱重建膝关节前后交叉韧带的临床观察

膝关节前后交叉韧带是稳定膝关节的重要结构.交叉韧带损伤后,不仅会造成膝关节不稳,且能造成继发性损害,造成半月板损伤和继发性关节炎,交叉韧带自愈困难,通常需要重建修复.同种异体肌腱移植修复前后交叉韧带损伤越来越受到关注[1].我科56例前后韧带断裂患者采用同种异体肌腱重建治疗,取得了较为满意的临床效果,现报告如下.     

Bioengineering skin using mechanisms of regeneration and repair

The development and use of artificial skin in treating acute and chronic wounds has, over the last 30 years, advanced from a scientific concept to a series of commercially viable products. Many important clinical milestones have been reached and the number of artificial skin substitutes licensed for clinical use is growing, but they have yet to replace the current "gold standard" of an autologous skin graft. Currently available skin substitutes often suffer from a range of problems that include poor integration (which in many cases is a direct result of inadequate vascularisation), scarring at the graft margins and a complete lack of differentiated structures. The ultimate goal for skin tissue engineers is to regenerate skin such that the complete structural and functional properties of the wounded area are restored to the levels before injury. New synthetic biomaterials are constantly being developed that may enable control over wound repair and regeneration mechanisms by manipulating cell adhesion, growth and differentiation and biomechanics for optimal tissue development. In this review, the clinical developments in skin bioengineering are discussed, from conception through to the development of clinically viable products. Central to the discussion is the development of the next generation of skin replacement therapy, the success of which is likely to be underpinned with our knowledge of wound repair and regeneration.     

腓骨长肌腱转位修复膝关节不稳的应用

目的：为带血供腓骨长肌腱转位修复膝关节不稳提供应用解剖学基础。方法：在１２０侧成人下肢标本对腓骨长肌外踝以上段的形态，血供及神经支配进行解剖观测。并在标本上进行模拟术式设计。结果：腓骨长肌腱平均长男６．９±１．３ｃｍ，女６．５±１．６ｃｍ，宽度男０．９±０．３ｃｍ，女０．８±０．３１ｃｍ；营养血管来自胫动脉的占５７．８％，来自腓动脉的占３６．４％；腓浅神经分支入肌处距腓骨头下方，男１．５±０．５ｃｍ，女１．５±０．４ｃｍ。结论：可以上述血管之一为蒂设计腓骨长肌腱转位修复膝关节交叉韧带及侧副韧带损伤的术式，术式具有可行性。     

周围神经损伤修复与再生中的基因治疗

背景：周围神经损伤后功能恢复不够理想。基因治疗为其功能修复提供了新的方法。 目的：从功能基因、转染载体选择、基因翻译因子生物学效应3方面进行综述,为周围神经损伤的基因治疗研究提供参考。 方法：由第一作者应用计算机检索PubMed和中国期刊全文数据库(CNKI)2006/2010相关文献。在标题、摘要、关键词中以“peripheral nerve injury, gene therapy, virus vector”或“周围神经损伤、基因治疗、病毒载体”为检索词进行检索。选择与周围神经损伤的基因治疗有关的文献,同一领域文献则选择近期发表及发表在权威杂志的文章。 结果与结论：共检索到35篇文章,按纳入和排除标准对文献进行筛选,保留20篇文章进行综述。目前,周围神经损伤的基因治疗技术已经日趋成熟,如转基因的腺病毒表达的骨形态发生蛋白7和Ad-32Ep65-Flag基因等,有望成为临床修复周围神经损伤的重要手段。     

Biomechanics of the ligaments of the human knee and of artificial ligaments

Summary The treatment of serious sprains and chronic laxity of the knee calls for a knowledge of the mechanical properties of the stabilizing structures. The mechanical characteristics indicate an elasticity rate of from 21 to 30% for the cruciate ligaments and average of 11% for the lateral ligments. Preservation methods markedly influence mechanical properties. In the case of chronic laxity, natural ligaments can be replaced by artificial ones. This comparative biomechanical study of natural and artificial ligaments provides a classification to help the user in his choice.

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Biomécanique des ligaments du genou humain et des ligaments artificiels

Résumé Les méthodes thérapeutiques des entorses graves et des laxités chroniques du genou nécessitent une connaissance des propriétés mécaniques des structures de stabilisation. Les caractéristiques mécaniques des ligaments croisés objectivent un pourcentage d'élasticité compris entre 21 et 30% pour les ligaments croisés et 11 % en moyenne pour les ligaments latéraux. Les propriétés mécaniques sont influencées par les méthodes de conservation. Un ligament artificiel remplace un ligament naturel dans le cas d'une laxité chronique. Le résultat d'une étude biomécanique comparative entre ligaments naturels et artificiels permet d'optimiser le choix de l'utilisateur.

     

Bioactive hydrogel-filament scaffolds for nerve repair and regeneration

The design of novel biomaterials is crucial for the advancement of tissue engineering in nerve regeneration. In this study we developed and evaluated novel biosynthetic scaffolds comprising collagen crosslinked with a terpolymer of poly(N-isopropylacrylamide) (PNiPAAm) as conduits for nerve growth. These collagen-terpolymer (collagen-TERP) scaffolds grafted with the laminin pentapeptide YIGSR were previously used as corneal substitutes in pigs and demonstrated enhanced nerve regeneration compared to allografts. The purpose of this project was to enhance neuronal growth on the collagen-TERP scaffolds through the incorporation of supporting fibers. Neuronal growth on these matrices was assessed in vitro using isolated dorsal root ganglia as a nerve source. Statistical significance was assessed using a one-way ANOVA. The incorporation of fibers into the collagen-TERP scaffolds produced a significant increase in neurite extension (p<0.05). The growth habit of the nerves varied with the type of fiber and included directional growth of the neurites along the surface of certain fiber types. Furthermore, the presence of fibers in the collagen-TERP scaffolds appeared to influence neurite morphology and function; neurites grown on fibers-incorporated collagen-TERP scaffolds expressed higher levels of Na channels compared to the scaffolds without fiber. Overall, our results suggest that incorporation of supporting fibers enhanced neurite outgrowth and that surface properties of the scaffold play an important role in promoting and guiding nerve regeneration. More importantly, this study demonstrates the potential value of tissue engineered collagen-TERP hybrid scaffolds as conduits in peripheral nerve repair.     

Skin tissue engineering for tissue repair and regeneration

Tissue-engineered skin is a significant advance in the field of wound healing. It has mainly been developed because of limitations associated with the use of autografts and allografts where the donor site suffers from pain, infection, and scarring. Recently, tissue-engineered skin replacements have been finding widespread application, especially in the case of burns, where the major limiting factor is the availability of autologous skin. The development of a bioartificial skin facilitates the treatment of patients with deep burns and various skin-related disorders. The present review gives a comprehensive overview of the developments and future prospects of scaffolds as skin substitutes for tissue repair and regeneration.