RESUMEN
The myotendinous junction (MTJ) is the muscle-tendon interface and constitutes an integrated mechanical unit to force transmission. Joint immobilization promotes muscle atrophy via disuse, while physical exercise can be used as an adaptative stimulus. In this study, we aimed to investigate the components of the MTJ and their adaptations and the associated elements triggered with aquatic training after joint immobilization. Forty-four male Wistar rats were divided into sedentary (SD), aquatic training (AT), immobilization (IM), and immobilization/aquatic training (IMAT) groups. The samples were processed to measure fiber area, nuclear fractal dimension, MTJ nuclear density, identification of telocytes, sarcomeres, and MTJ perimeter length. In the AT group, the maintenance of ultrastructure and elements in the MTJ region were observed; the IM group presented muscle atrophy effects with reduced MTJ perimeter; the IMAT group demonstrated that aquatic training after joint immobilization promotes benefits in the muscle fiber area and fractal dimension, in the MTJ region shows longer sarcomeres and MTJ perimeter. We identified the presence of telocytes in the MTJ region in all experimental groups. We concluded that aquatic training is an effective rehabilitation method after joint immobilization due to reduced muscle atrophy and regeneration effects on MTJ in rats.
Asunto(s)
Adaptación Fisiológica , Inmovilización , Articulaciones , Condicionamiento Físico Animal , Esfuerzo Físico , Tendones/fisiología , Animales , Masculino , Fibras Musculares Esqueléticas/citología , Fibras Musculares Esqueléticas/metabolismo , Fibras Musculares Esqueléticas/ultraestructura , Ratas , Sarcómeros/ultraestructura , Tendones/citología , Tendones/ultraestructuraRESUMEN
The study aims to describe the tissue plasticity of MTJ through the morphological analysis of MTJ soleus in ovariectomized aged female Wistar rats submitted to aquatic training. Forty aged Wistar rats, 1 year and 2 months of age, were divided into four groups: sedentary (S), trained (T), ovariectomized (O), and trained/ovariectomized (OT). Employing the transmission electron microscopy, the ultrastructural and morphometric elements were revealed. In the S group, changes in morphological characteristics as a consequence of the aging process were seen, demonstrated by the conical shape of the muscle cell extremity, a large area with collagen deposit, and misalignment of sarcomeres in series. The T group presented ample adjustments when revealed the organization of MTJ, through the increase of the contact area and greater lengths of sarcoplasmatic invaginations and evaginations. The O group revealed extensive tissue disorganization with muscle atrophy, reduction of MTJ contact area, and consequently, changes in sarcoplasmatic invaginations and evaginations. The OT group demonstrated extensive remodeling with restructuring MTJ through the increase of tissue contact area, extensive organization, parallel arrangement, and increased length of sarcoplasmatic invaginations and evaginations. The distal sarcomeres presented higher lengths compared to the proximal sarcomeres in both the groups. We conclude that aquatic training was effective in the organization and structural remodeling of the myotendinous interface of ovariectomized aged rats. There was a greater area of contact, and consequently, greater resistance in the myotendinous interface promoting a lower predisposition to injuries.
Asunto(s)
Adaptación Fisiológica , Músculo Esquelético/fisiología , Músculo Esquelético/ultraestructura , Ovariectomía , Condicionamiento Físico Animal , Tendones/fisiología , Tendones/ultraestructura , Animales , Femenino , Microscopía Electrónica de Transmisión , Células Musculares/ultraestructura , Ratas WistarRESUMEN
Tendon collagen fibrils are the basic force-transmitting units of the tendon. Yet, surprisingly little is known about the diversity in tendon anatomy and ultrastructure, and the possible relationships between this diversity and locomotor modes utilized. Our main objectives were to investigate: (a) the ultra-structural anatomy of the tendons in the digits of frogs; (b) the diversity of collagen fibril diameters across frogs with different locomotor modes; (c) the relationship between morphology, as expressed by the morphology of collagen fibrils and tendons, and locomotor modes. To assess the relationship between morphology and the locomotor modes of the sampled taxa we performed a principal component analysis considering body length, fibrillar cross sectional area (CSA) and tendon CSA. A MANOVA showed that differences between species with different locomotor modes were significant with collagen fibril diameter being the discriminating factor. Overall, our data related the greatest collagen fibril diameter to the most demanding locomotor modes, conversely, the smallest collagen fibril CSA and the highest tendon CSA were observed in animals showing a hopping locomotion requiring likely little absorption of landing forces given the short jump distances.
Asunto(s)
Anuros/anatomía & histología , Locomoción/fisiología , Tendones/anatomía & histología , Animales , Matriz Extracelular/metabolismo , Colágenos Fibrilares/metabolismo , Análisis de Componente Principal , Tendones/ultraestructuraRESUMEN
The plantaris longus tendon (PLT) in bullfrog develops a fibrocartilage-like tissue in the area that is functionally subject to compressive forces. The aim of this study was to analyze the modifications of the pressure-bearing region in bullfrog PLT with different ages (7, 180, and 1,080 days after the end of metamorphosis) using histomorphometric, ultrastructural and biochemical methods. Weak basophilia and cells with a fibroblastic phenotype were observed in the compression region at 7 days of age. On the other hand, a large area of intense tissue basophilia associated with a chondroblast-like cell population was noted at the other ages. Collagen fibers exhibited a three-dimensional network-like arrangement at all ages. The number of connective tissue cells increased between 7 and 180 days of age and was reduced in older animals. The 180-day-old animals presented a well-developed pericellular matrix rich in proteoglycans. The mean diameter of collagen fibrils increased from 7 to 180 days and was the same at 1,080 days. Glycosaminoglycan content was higher in 7-day-old animals. A higher amount of hydroxyproline was observed at 180 and 1,080 days. The swelling test showed a significant increase of wet weight in 7-day-old animals. In conclusion, the alterations that occur in the pressure-bearing of bullfrog PLT are the result of physiological alterations of the animal with the maturation and aging.
Asunto(s)
Envejecimiento/fisiología , Rana catesbeiana/fisiología , Tendones/ultraestructura , Animales , Glicosaminoglicanos/análisis , Hidroxiprolina/análisis , Microscopía , Microscopía Electrónica de Transmisión , Rana catesbeiana/anatomía & histología , Tendones/química , Tendones/fisiología , Soporte de Peso/fisiologíaRESUMEN
The myotendinous junction (MTJ) is a major area for transmitting force from the skeletal muscle system and acts in joint position and stabilization. This study aimed to use transmission electron microscopy to describe the ultrastructural features of the MTJ of the sternomastoid muscle in Wistar rats from newborn to formation during adulthood and possible changes with aging. Ultrastructural features of the MTJ from the newborn group revealed pattern during development with interactions between muscle cells and extracellular matrix elements with thin folds in the sarcolemma and high cellular activity evidenced through numerous oval mitochondria groupings. The adult group had classical morphological features of the MTJ, with folds in the sarcolemma forming long projections called "finger-like processes" and sarcoplasmic invaginations. Sarcomeres were aligned in series, showing mitochondria near the Z line in groupings between collagen fiber bundles. The old group had altered "finger-like processes," thickened in both levels of sarcoplasmic invaginations and in central connections with the lateral junctions. We conclude that the MTJ undergoes intense activity from newborn to its formation during adulthood. With increasing age, changes to the MTJ were observed in the shapes of the invaginations and "finger-like processes" due to hypoactivity, potentially compromising force transmission and joint stability.
Asunto(s)
Músculos/ultraestructura , Músculos del Cuello/ultraestructura , Tendones/ultraestructura , Envejecimiento , Animales , Animales Recién Nacidos , Matriz Extracelular/ultraestructura , Microscopía Electrónica de Transmisión , Células Musculares/ultraestructura , Ratas , Ratas Wistar , SarcolemaRESUMEN
Tendons are formed by dense connective tissue composed of an abundant extracellular matrix (ECM) that is constituted mainly of collagen molecules, which are organized into fibrils, fibers, fiber bundles and fascicles helicoidally arranged along the largest axis of the tendon. The biomechanical properties of tendons are directly related to the organization of the collagen molecules that aggregate to become a super-twisted cord. In addition to collagen, the ECM of tendons is composed of non-fibrillar components, such as proteoglycans and non-collagenous glycoproteins. The capacity of tendons to resist mechanical stress is directly related to the structural organization of the ECM. Collagen is a biopolymer and presents optical anisotropies, such as birefringence and linear dichroism, that are important optical properties in the characterization of the supramolecular organization of the fibers. The objective of this study was to present a review of the composition and organization of the ECM of tendons and to highlight the importance of the anisotropic optical properties in the study of alterations in the ECM.
Asunto(s)
Matriz Extracelular/química , Matriz Extracelular/ultraestructura , Tendones/química , Tendones/ultraestructura , Animales , Anisotropía , Humanos , Fenómenos MecánicosRESUMEN
This study analyzed the ultrastructural characteristics of the myotendinous junction (MTJ) between anterior belly of digastrics muscle and the intermediate tendon in adult rats. Six male Wistar rats were used and were anesthetized with an overdose of urethane and sacrificed by intracardiac perfusion with modified Karnovsky solution, postfixed in 1% osmium tetroxide, dehydrated in increasing series of alcohols and embedded in Spurr resin for transmission electron microscopic analysis. Ultrastructural analysis showed conical shape of the fiber extremity in MTJ region, highlighting the presence of numerous mitochondria arranged in groups in the subsarcolemmal and intermyofibrillary regions. Atypical MTJ characteristics were seen interspersed with bundles of collagen fibers. Classic characteristics such as finger-like processes by means of sarcoplasmic projections were observed among interdigitations. Terminals and periphericals bundles of myofibrils showed close relationship with the adjacent muscle fiber's endomysium through lateral junctions. In the distal portion, it was observed that the communication region of microtendons forming the intermediate tendon of digastric muscle, and it can highlight the columns disposition of tenocytes. In conclusion, the MTJ ultrastructure between the anterior belly of digastric muscle and intermediate tendon of adult rats showed classical morphologic descriptions and presented an atypical region revealed by the subspecialization between the myofibrils bundles and collagen fibers in the MTJ region.
Asunto(s)
Músculos/ultraestructura , Tendones/ultraestructura , Animales , Colágeno/ultraestructura , Matriz Extracelular/ultraestructura , Masculino , Microscopía Electrónica de Transmisión , Células Musculares/ultraestructura , Orgánulos/ultraestructura , Ratas , Ratas WistarRESUMEN
The myotendon junction (MTJ) is a specialised area into the muscle fibers where the sarcoplasmic membranes connect to the collagen fibers bundles. There are few data about plasticity of the MTJ in aging processes. The aim of this study is to analyse the ultrastructure characteristics of MTJ of medial pterygoid muscle of adult and aged rats. Employing the transmission electron microscopy method, twenty male rats Wistar (Rattus norvegicus) were divided into two groups: A (n=10) with 12 months of age; B (n=10) 24 months of age. The animals were anaesthetised with overdose the urethane (3g/kg, i.p.) and sacrified during the perfusion with modified Karnovsky solution. The specimens were post-fixed in a 1% osmium tetroxide solution, dehydrated in ascending concentration of ethanol and embedded in Spurr resin. The thin sections, of 90 nm thick, were counterstained with uranyl acetate and lead citrate solution, and examined in a Jeol 1010 transmission electron microscope. The fine structure of the MTJ of group A revealed the defined interdigitations and disposed in several levels of deep formations containing the collagen fibers. In the group B, such structures did not observed, detecting the projections irregular in shape, and large of extra matrix with in aspect of remodelling. In conclusion it was possible to identify the plasticity of MTJ in the group B which presented several morphological alterations comparing to the adult animals. These data of group B suggested the occurrence of aging processes in the MTJ in rats.
Asunto(s)
Músculos Pterigoideos/ultraestructura , Tendones/ultraestructura , Factores de Edad , Animales , Masculino , Microscopía Electrónica de Transmisión , Ratas , Ratas WistarRESUMEN
Obesity is currently considered to be a world epidemic and one of the major public health problems in many countries, whose incidence is increasing at alarming rates. Genetically obese Zucker rats are used as a model of obesity and were employed in the present study. Tendons transmit contractile force from muscles to bone, thus permitting articular movement. The objective of our study was to analyze the ultrastructural, biochemical, and biomechanical alterations that occur in the deep digital flexor tendon of obese Zucker rats compared to lean animals. Ultrastructural analysis showed differences in collagen fibril diameter distribution and mass-average diameter between obese and lean animals. Regarding mechanical parameters, there was a significant difference in maximum displacement and strain. Hydroxyproline content was higher in obese animals. In view of the excess weight and peculiar conditions to which the tendon of obese animals is submitted, we concluded that obesity provokes alterations in the composition and organization of tendon extracellular matrix components. These alterations might be related to organizational and structural modifications in the collagen bundles, influencing the mechanical properties of the tendon and the progression to a pathological state.
Asunto(s)
Colágeno/ultraestructura , Obesidad/patología , Ratas Zucker/fisiología , Tendones/ultraestructura , Animales , Colágeno/fisiología , Matriz Extracelular/química , Matriz Extracelular/metabolismo , Miembro Anterior , Hidroxiprolina/análisis , Hidroxiprolina/metabolismo , Técnicas para Inmunoenzimas , Masculino , Obesidad/genética , Ratas , Estrés Mecánico , Tendones/química , Tendones/metabolismo , Resistencia a la TracciónRESUMEN
Although the myotendinous junction (MTJ) of skeletal striated muscle is well known, more detailed studies regarding the structure of the cardiac MTJ are scarce. The objective of the present study was to investigate the morphological characteristics of the MTJ in hearts of healthy and hypertensive (SHR) female rats using histological, ultrastructural and three-dimensional (SEM) methods, as well as to evaluate the expression of vinculin by immunofluorescence. In the two groups, light microscopy showed branching tendinous cords and collagen bundles penetrating the apex of the finger-like projections of the papillary muscle. SEM analysis revealed an enlarged apex of the papillary muscle in SHR which was not observed in healthy animals. The loss of force transmission appears to be compensated by the amplified connection between the papillary muscle and valvular collagen. A large number of intercalated disks close to the fiber apex, small amounts of an amorphous intercellular substance and numerous vesicles were observed in SHR. In these animals, the expression of vinculin was more marked showing a regular distribution and a pattern of transverse striations along the sarcolemma. The presence of this protein in transverse bands suggests that vinculin surrounds myofibrils in the region of the Z band. Vinculin staining was also more marked in the region of the tendinous cord-papillary muscle junctions of SHR compared to control animals. Vinculin was quantified by electrophoresis and higher amounts of this protein were observed in SHR compared to control animals.
Asunto(s)
Hipertensión/patología , Músculos Papilares/patología , Músculos Papilares/ultraestructura , Tendones/patología , Tendones/ultraestructura , Animales , Colágeno/ultraestructura , Femenino , Hipertensión/metabolismo , Microscopía Electrónica , Microscopía Fluorescente , Músculos Papilares/metabolismo , Ratas , Sarcolema/patología , Sarcolema/ultraestructura , Tendones/metabolismo , Vinculina/biosíntesisRESUMEN
Tendons are parallel arrays of collagenous fibers which are specialized in resisting and transmitting tensile forces. In this work we examined the structure of the superficial digital flexor tendon (SDFT) and the deep digital flexor tendon (DDFT) of pigs, which are considered "wrap around" tendons and so receive compression and tension forces. In both tendons, fibrocartilaginous areas were observed in the regions subjected to compression plus frictional loading. Histological and ultrastructural analyses of the tensional region showed an extracellular matrix (ECM) rich in collagen bundles, that were all arranged in the same direction. Fibroblasts were seen closely associated with the collagen bundles. Chondrocyte-like cells and high levels of glycosaminoglycans (GAGs) were observed in the compressional regions. The collagen bundles in the compressional region were arranged in several directions and were associated with proteoglycans (PGs). The crimp pattern detected in the tensional region showed that the collagen fibrils were ordered aggregates which formed helical superstructures.
Asunto(s)
Sus scrofa/anatomía & histología , Tendones/ultraestructura , Animales , Colágeno/metabolismo , Colágeno/ultraestructura , Fibroblastos/ultraestructura , Glicosaminoglicanos/metabolismo , Miembro Posterior , Masculino , Microscopía Electrónica , Microscopía Electrónica de Rastreo , Proteoglicanos/metabolismo , Sus scrofa/metabolismo , Tendones/metabolismoRESUMEN
Tendon composition changes according to differentiation, mechanical load, and aging. In this study, we attempted to identify, localize, and quantify type VI collagen in bovine tendons. Type VI collagen was identified by the electrophoretic behavior of the alpha chains and Western blotting, and by rotary shadowing. Type VI collagen was extracted from powdered tendon with three sequential 24-h extractions with 4 M guanidine-HCl. The amount of type VI collagen was determined by enzyme-linked immunosorbent assay for purely tensional areas and for the compressive fibrocartilage regions of the deep flexor tendon of the digits, for the corresponding fetal and calf tendons, and for the extensor digital tendon. The distal fibrocartilaginous region of the adult tendon was richer in type VI collagen than the tensional area, reaching as much as 3.3 mg/g (0.33%) of the wet weight. Calf tendons showed an accumulation of type VI at the fibrocartilage site. Immunocytochemistry demonstrated that type VI collagen was evenly distributed in the tensional areas of tendons but was highly concentrated around the fibrochondrocytes in the fibrocartilages. The results demonstrate that tendons are variable with regard to the presence and distribution of type VI collagen. The early accumulation of type VI collagen in the region of calf tendon that will become fibrocartilage in the adult suggests that it is a good marker of fibrocartilage differentiation. Furthermore, the distribution of type VI collagen in tendon fibrocartilage indicates that it organizes the pericellular environment and may represent a survival factor for these cells.
Asunto(s)
Colágeno Tipo VI/análisis , Tendones/química , Animales , Bovinos , Matriz Extracelular/química , Matriz Extracelular/ultraestructura , Inmunohistoquímica , Tendones/ultraestructuraRESUMEN
Few studies have discussed the relationship between the molecular organization and the physicochemical and biomechanical properties of pig tendons. In this work, we examined the extracellular matrix of the deep digital flexor tendon of pigs, which was subjected to tensional (proximal region) and compressive (distal and terminal regions) forces. The three regions of the tendon were used for swelling tests and their glycosaminoglycan content was determined. Longitudinal sections of the tendon were stained and observed using polarized light microscopy. The distal and terminal regions were swole more in water than the proximal region. After staining with toluidine blue the metachromasy was more intense in the distal and terminal regions, indicating an accumulation of proteoglycans in these regions. Analysis of the glycosaminoglycans by agarose gel electrophoresis showed that dermatan sulfate was present in all regions, whereas chondroitin sulfate occurred only in the regions of compression. The shape of the fibroblasts changed along the tendon: rounded cells occurred in regions under compression, while in the region under tension, elongated cells predominated. The organization and distribution of the collagen bundles were different for each region. Birefringence analysis revealed a more regular crimp pattern in the region under tension than in the regions under compressive forces. The elastic fibers also showed a different distribution in each region. These results indicate that the regional differences in the structure and composition of the deep digital flexor tendon of pigs are related to the biomechanical properties of the tendon.
Asunto(s)
Animales , Colágeno , Fibras Musculares Esqueléticas , Proteoglicanos , Tendones/anatomía & histología , Tendones/citología , Tendones/ultraestructura , Soporte de Peso/fisiologíaRESUMEN
Chickens were divided into two groups, one caged and the other penned. Superficial digital flexor tendons from penned chickens showed greater tensile strength, withstanding a greater strain before rupture than tendons from caged chickens. The tensile region of tendons from penned chickens showed more swelling in acetic acid and a higher hydroxyproline concentration compared with caged chickens, indicating the presence of large collagen amounts in the former. The tensile region of penned chickens presented higher glycosaminoglycan concentrations than the same region of caged chickens. For both groups, the predominant glycosaminoglycan in the compression regions was chondroitin sulfate, whereas dermatan sulfate was found in the tensile regions. N-terminal analysis identified the small proteoglycans fibromodulin and decorin. SDS-PAGE indicated that decorin was present in all regions and fibromodulin was mainly observed in the tensile region. These results indicate that an external condition, in this case the area available for locomotion, might influence the synthesis of extracellular matrix components and the mechanical properties of the tendon.
Asunto(s)
Pollos/anatomía & histología , Tendones/fisiología , Secuencia de Aminoácidos , Animales , Fenómenos Biomecánicos , Pollos/fisiología , Decorina , Matriz Extracelular/ultraestructura , Proteínas de la Matriz Extracelular/química , Fibromodulina , Glicosaminoglicanos/análisis , Miembro Posterior , Vivienda para Animales , Datos de Secuencia Molecular , Condicionamiento Físico Animal , Proteoglicanos/química , Homología de Secuencia de Aminoácido , Tendones/ultraestructura , Resistencia a la TracciónRESUMEN
Wave-like structures (WLS also known as crimp) have generally been reported to be planar structures. However, there is evidence that a helical superstructure, rather than a planar one, should be considered. Conditions dictated by supramolecular chemistry, molecular recognition and self-assembly favor the idea of a helical arrangement for collagen bundles in a supramolecular structure. The aim of this work is to provide additional data in support of a helical superstructure for collagen bundles in tendons. Cryosections of fixed flexor bovine tendons and sections of resin-embedded peeled rat tail were studied using polarized light, interference, and phase contrast microscopy. Image analysis was used to find appropriate mathematical descriptors for WLS. Interference colors due to the dispersion of birefringence allowed the detection of a gradual, intertwined twisted fiber organization in WLS, as the angle of the tendon axis was rotated relative to the polarizers. Helical movements of the images of the WLS bands were produced using animation methods. Interference microscopy revealed interference colors associated with different orientations and dry mass concentrations in the fibers, especially in tendon cross-sections, which also exhibited Maltese-cross birefringence images. Similar images were detected by interference microscopy, suggesting a spiral organization of fibers in the section plane. The helical orientation of the fibers was detected by focusing through different planes of sections. Based on a comparison of this superstructure with mesophases, the twisted grain boundary concept is considered to be the most appropriate for the classification of tendon WLS.
Asunto(s)
Procesamiento de Imagen Asistido por Computador , Tendones/química , Tendones/ultraestructura , Animales , Birrefringencia , Bovinos , Colágeno , Microscopía de Interferencia , Microscopía de Polarización , Ratas , Cola (estructura animal)RESUMEN
Morphological, immunocytochemical and ultrastructural methods were used to investigate the role of cells during elastogenesis in the elastic tendon of the chicken wing. Intimate contact of the cell processes with elastic fibers was observed in adult birds. During development there was a sequential appearance of microfibril bundles that became progressively impregnated with amorphous elastin, which eventually predominated in fully developed elastic fibers. The growing elastic fibers were usually enveloped by recesses of the cell surface. The tendon cells were polarized in their association with fibrous components of the extracellular matrix. This arrangement suggests that these cells secrete and organize elastic and collagen fibers to different extracellular compartments. These results show that cells are intimately involved in producing components of different extracellular matrix fibers, in controlling their assembly, and in defining their borders and associations during development.
Asunto(s)
Tejido Elástico/ultraestructura , Tendones/ultraestructura , Alas de Animales/ultraestructura , Animales , Embrión de Pollo , Pollos , Tejido Elástico/química , Tejido Elástico/embriología , Tendones/química , Tendones/embriología , Alas de Animales/química , Alas de Animales/embriologíaRESUMEN
The high positive linear dichroism (LD) exhibited by silver-impregnated collagen fibers are thought to be caused by an ordered binding of silver nanoparticles to the collagen fibers. A correlation between LD, established by image analysis, and the size of silver particles as measured by electron microscopy was investigated in the same sections of silver-impregnated tendon collagen fibers. Silver particles were found to be periodically ordered along the collagen fibers, with some preference for the 67 nm collagen period and collagen a bands. The silver particle diameter for a sample of n=279 was 18.51 nm on average, with 95% of the values ranging between 17.90 and 19.14 nm. The finding that interference colors are correlated to abnormal dispersion of birefringence characteristics supports the concept that collagen fibers induce an ordered binding of silver distributed along the fibers.
Asunto(s)
Colágeno/química , Colágeno/ultraestructura , Microscopía Electrónica/métodos , Animales , Anisotropía , Birrefringencia , Bovinos , Colorantes , Técnicas In Vitro , Estructura Molecular , Plata , Tendones/química , Tendones/ultraestructuraRESUMEN
The proximal region of the superficial digital flexor tendon of pigs passes under the tibiotarsal joint, where it is subjected to compressional and tensional forces. This region was divided into a surface portion (sp), which is in direct contact with the bone and into a deep portion (dp), which is the layer opposite the articulating surface. The purpose of this work was to analyse the distribution and organisation of the collagen bundles and proteoglycans in the extracellular matrix in sp and dp. Toluidine-blue-stained sections were analysed under a polarising microscope. Strong basophilia and metachromasia were observed in sp, demonstrating accumulation of proteoglycan in a region bearing compression, but the intensity was reduced the further layers were from the bone. Linear dichroism confirmed that the glycosaminoglycan molecules were disposed predominantly parallel to the longest axis of the collagen fibrils. Birefringence analysis showed a higher molecular order and aggregation of the collagen bundles in areas where the tension was more prominent. The crimp pattern was more regular in dp than in sp, probably as a requirement for tendon stretching. The optical anisotropy exhibited by the collagen bundles also confirmed the helical organisation of the collagen bundles in the tendon. Hyaluronidase digestion caused a decrease in the basophilia, but this was not eliminated, supporting the idea that in the matrix, proteoglycans are not completely available to the enzyme action.
Asunto(s)
Porcinos/metabolismo , Tendones/ultraestructura , Animales , Anisotropía , Birrefringencia , Colágeno/análisis , Matriz Extracelular/química , Masculino , Microscopía de Polarización , Proteoglicanos/análisis , Estrés Mecánico , Tendones/metabolismoRESUMEN
The elastic tendon of the avian wing has been described by others as a unique structure with elastic properties due to the predominance of elastic fibers in the midsubstance. Further analyses of the tendon have shown it to possess five anatomically distinct regions. Besides the major elastic region, a distally located fibrocartilage and three tendinous regions are present. The tendinous regions connect: (1) the muscle to the elastic region, (2) the elastic region to the fibrocartilage and (3) the latter to the insertion site. The elastic region possesses thick and abundant elastic fibers and very thin, interconnecting collagen fibers. The collagen fibers in the sesamoid fibrocartilage are thick and interwoven, defining spaces occupied by fibrochondrocytes embedded in a non-fibrillar and highly metachromatic matrix. Biochemical analyses have shown that the fibrocartilage has about tenfold the amount of glycosaminoglycans (GAGs) found in the other regions. The main GAG in this region was chondroitin sulfate (CS) (plus keratan sulfate as detected immunocytochemically), while the other regions showed variable amounts of CS, dermatan sulfate (DS) and heparan sulfate. Further analyses have shown that a large CS-bearing proteoglycan is found in the fibrocartilage. The elastic region possesses two main proteoglycans, a large CS-bearing proteoglycan (which reacted with an antibody against keratan sulfate after chondroitinase ABC treatment) and a predominant DS-bearing proteoglycan, which showed immunoreactivity when assayed with an anti-biglycan antibody. The results demonstrate that the elastic tendon is a complex structure with complex regional structural and compositional adaptations, suited to different biomechanical roles.
Asunto(s)
Pollos/anatomía & histología , Tejido Elástico/anatomía & histología , Tejido Elástico/química , Proteoglicanos/análisis , Tendones/anatomía & histología , Tendones/química , Alas de Animales/anatomía & histología , Alas de Animales/química , Animales , Cartílago/anatomía & histología , Cartílago/química , Cartílago/ultraestructura , Colágeno/análisis , Tejido Elástico/ultraestructura , Glicosaminoglicanos/análisis , Glicosaminoglicanos/aislamiento & purificación , Histocitoquímica , Inmunohistoquímica , Microscopía Electrónica , Proteoglicanos/aislamiento & purificación , Tendones/ultraestructura , Alas de Animales/ultraestructuraRESUMEN
Structural and compositional variations are marked in tendon fibrocartilages, which appear at the insertion to bone and in areas subjected to compressive plus frictional loading regime. We are interested in characterizing the extracellular matrix adaptations in these areas, in an attempt to understand cellular responses to biomechanics. In this work, we have applied immunocytochemistry and an ATP treatment for the ultrastructural identification of type VI collagen, to tendons subjected to compressive forces in different species. Immunocytochemistry, after testicular hyaluronidase or pepsin digestion, revealed the presence of type VI collagen in tensional and compressive areas of the plantaris longus tendon of the bullfrog, in the deep flexor tendon of dogs and rabbits, in the calcanear tendon and the suprapatela of rats and in the gastrocnemius tendon of chickens. In each tendon, the tensional region showed a weak reaction, restricted to the collagen fiber surface. However, the compression region was especially rich in type VI collagen, which accumulates in the interfibrillar spaces and is concentrated around the fibrochondrocytes. Intense reaction was also found in the paratenon. The ATP treatment not only allowed for the detection of the typical ladder-like aggregates of type VI collagen in the same areas identified by immunocytochemistry, but also demonstrated that type VI collagen forms a microfibrillar network around the fibrochondrocytes. Besides the function of organizing groups of collagen fibrils, type VI collagen seems to assemble the pericellular matrix in tendon fibrocartilages, perhaps through physical interactions with the large proteoglycans that concentrate in the same area.