RESUMO
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.
Assuntos
Adaptação Fisiológica , Imobilização , Articulações , Condicionamento Físico Animal , Esforço Físico , Tendões/fisiologia , Animais , Masculino , Fibras Musculares Esqueléticas/citologia , Fibras Musculares Esqueléticas/metabolismo , Fibras Musculares Esqueléticas/ultraestrutura , Ratos , Sarcômeros/ultraestrutura , Tendões/citologia , Tendões/ultraestruturaRESUMO
The superficial digital flexor tendon (SDFT) connects the superficial digital flexor muscle to the digits and its main function is to participate in digit flexion. The SDFT presents different regions along its length, which adapt to different biomechanical forces. During growth and maturation, the tendon may present changes in the regions subjected to compression and tension, with variations in the composition of the extracellular matrix (ECM), in the arrangement of collagen fibers and cellularity. With the purpose of analyzing the morphological and biochemical alterations of ECM of tendons during the growth and maturation, Gallus domesticus were euthanized at 1, 5, and 8 months of age and their SDFT were divided into regions of tension/compression (Sp) and tension (Sd). From 1 month of age, the Sp region already presented fibrocartilage characteristics with cells similar to chondrocytes. At 5 and 8 months, the Sd region displayed formation of a new structure similar to bone matrix, and intense metachromasia. The animals of 5 and 8 months presented an increase in MMP-2 and -9 activities and a lower number of cells when compared with the animals of 1 month, in both regions. In conclusion, structural and biochemical alterations occur during the maturation process of the SDFT, involving a decrease in the number of cells and changes in the degradation and composition of the ECM. Anat Rec, 302:964-972, 2019. © 2018 Wiley Periodicals, Inc.
Assuntos
Matriz Extracelular/metabolismo , Gelatinases/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Músculo Esquelético/metabolismo , Tendões/anatomia & histologia , Tendões/metabolismo , Animais , Galinhas , Músculo Esquelético/anatomia & histologia , Músculo Esquelético/citologia , Tendões/citologiaRESUMO
Present study provides a numerical investigation on multiscale boundary conditions in the computational homogenization of a representative volume element (RVE) of tendon fascicles. A three-dimensional hexagonal-helicoidal finite element RVE composed of two material phases (collagen fibers and cells) and three finite strain viscoelastic models (collagen fibrils, matrix of fibers and cells) compose the multiscale model. Due to the unusual helical geometry of the RVE, the performance of four multiscale boundary conditions is evaluated: the linear boundary displacements model, the minimally constrained model and two mixed boundary conditions allying characteristics of both, linear and minimal models. Numerical results concerning microscopic kinematic fields and macroscopic stress-strain curves point out that one of the mixed models is able to predict the expected multiscale mechanics of the RVE, presenting sound agreement with experimental facts reported in literature, for example: characteristic non-linear shape of the stress-strain curves; macroscopic energy loss by hysteresis; axial rotation of fascicles observed in tensile tests; collagen fibrils are the main load-bearing components of tendons; cells contribute neither to the stiffness nor to the macroscopic energy loss. Moreover, the multiscale model provides important insights on the micromechanics of tendon fascicles, predicting a non-homogeneous and relevant strain localization on cells, even under physiological macroscopic strain amplitudes.
Assuntos
Fenômenos Mecânicos , Modelos Biológicos , Tendões/citologia , Tendões/metabolismo , Fenômenos Biomecânicos , Colágeno/metabolismo , Análise de Elementos Finitos , Estresse MecânicoRESUMO
Sesamoids are skeletal elements rarely considered in studies of the vertebrate skeleton. In this work, we integrate ontogenetic data of anuran sesamoids in two species (Leptodactylus latinasus and Pleurodema cf. guayapae), the related structures (tendons, muscles, and joints) in L. latinasus, and a survey of sesamoid distribution in 185 anuran taxa. Our main goals are: (1) to contribute to the knowledge of the comparative anatomy of sesamoids in tetrapods; (2) to provide additional developmental evidence to interpret the ontogenetic pattern of sesamoids in anurans, as a key to elucidate that of tetrapods in general; (3) to provide data about tendon development in relation to sesamoid development in anurans for the first time; and (4) to propose a pattern of anuran sesamoid distribution. The homologies of sesamoids across tetrapods are discussed here. Observations were made in cleared and stained skeletal whole-mounts. Fifty-four sesamoids were found in anurans, thirty-seven of which occur in L. latinasus. The traditional point of view of embedded sesamoids always resulting from biomechanical stimuli of a previously existing tendon is not sustained by our data. Many sesamoids arise before the differentiation of a tendinous tissue. Our survey results in a data set where the two big anuran clades, Hyloides (12 families) and Ranoides (14 families), were represented. The matrix has 38% missing entries. Most of the surveyed sesamoids have multiple origins, with only three of them (about 19%) having one origin.
Assuntos
Anuros/anatomia & histologia , Ossos Sesamoides/anatomia & histologia , Animais , Anuros/fisiologia , Evolução Biológica , Desenvolvimento Ósseo/fisiologia , Diferenciação Celular , Extremidades/anatomia & histologia , Músculo Esquelético/anatomia & histologia , Filogenia , Ossos Sesamoides/crescimento & desenvolvimento , Especificidade da Espécie , Tendões/anatomia & histologia , Tendões/citologiaRESUMO
OBJECTIVE: The purpose of this study was to histologically analyze allografts from cadaveric semitendinous muscle after cryopreservation at -80 degrees C in comparison to a control group kept at only -4 degrees C to test the hypothesis that the histological characteristics of the tissue are maintained when the tendons are kept at lower temperatures. METHODS: In a tissue bank, 10 semitendinous tendons from 10 cadavers were frozen at -80 degress C as a storage method for tissue preservation. They were kept frozen for 40 days, and then a histological study was carried out. Another 10 tendon samples were analyzed while still "fresh". RESULTS: There was no histological difference between the fresh and frozen samples in relation to seven variables. CONCLUSIONS: Semitendinous muscle tendon allografts can be submitted to cryopreservation at -80 degrees C without suffering histological modifications.
Assuntos
Criopreservação , Músculo Esquelético/citologia , Tendões/citologia , Adulto , Feminino , Humanos , Masculino , Transplante HomólogoRESUMO
OBJECTIVE: The purpose of this study was to histologically analyze allografts from cadaveric semitendinous muscle after cryopreservation at -80°C in comparison to a control group kept at only -4°C to test the hypothesis that the histological characteristics of the tissue are maintained when the tendons are kept at lower temperatures. METHODS: In a tissue bank, 10 semitendinous tendons from 10 cadavers were frozen at -80ºC as a storage method for tissue preservation. They were kept frozen for 40 days, and then a histological study was carried out. Another 10 tendon samples were analyzed while still "fresh". RESULTS: There was no histological difference between the fresh and frozen samples in relation to seven variables. CONCLUSIONS: Semitendinous muscle tendon allografts can be submitted to cryopreservation at -80ºC without suffering histological modifications.
Assuntos
Adulto , Feminino , Humanos , Masculino , Criopreservação , Músculo Esquelético/citologia , Tendões/citologia , Transplante HomólogoRESUMO
Biochemical and morphological aspects of fibrocartilages of calcaneal and deep digital flexor tendons in rats aged 30, 180 and 730 days were analyzed. In both tendons a stronger staining with Alcian blue, indicating the presence of proteoglycans, was detected in rats of 30 and 180 days. In animals 730 days old, it was restricted to the pericellular area. Ultrastructural analysis showed a more prominent pericellular matrix in calcaneal tendon compared to the deep digital flexor tendon. The biochemical analysis showed higher levels of proteins and glycosaminoglycans in the calcaneal tendon of 30-day-old rats compared to older rats. In the deep digital flexor tendon, no significant differences were observed between ages. The small proteoglycan, fibromodulin, was detected in both tendons of all ages, but in young rats it appeared to be running as a 210 kDa component, probably due to the association with collagen chains or self-association.
Assuntos
Envelhecimento/fisiologia , Fibrocartilagem/química , Fibrocartilagem/citologia , Tendões/química , Tendões/citologia , Animais , Calcâneo/citologia , Calcâneo/ultraestrutura , Eletroforese em Gel de Poliacrilamida , Fibrocartilagem/ultraestrutura , Glicosaminoglicanos/análise , Masculino , Proteínas/análise , Ratos , Ratos Wistar , Ácidos Urônicos/análiseRESUMO
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.
Assuntos
Animais , Colágeno , Fibras Musculares Esqueléticas , Proteoglicanas , Tendões/anatomia & histologia , Tendões/citologia , Tendões/ultraestrutura , Suporte de Carga/fisiologiaRESUMO
The superficial digital flexor tendon of pigs is a wrap around tendon supporting compressive in addition to the tensional forces in its proximal region, and only tensional forces in the intermediate region. Clear distinctions were observed in the physical properties, composition of proteoglycan and morphology for the different regions. A greater swelling in water and a larger amount of glycosaminoglycan were found in the proximal region compared to the intermediate one. Dermatan sulfate was detected in all regions of this tendon, while chondroitin sulfate was prominent only near the bone. In the toluidine blue stained sections, intense metachromasy was observed in the sites under compressive forces, especially in the portion close to the bone. Chondrocyte like cells were also observed in these arms. Crimp morphology, observed in the intermediate region, exhibited a clearly sloped aspect in relation to the main axis of the tendon. Elastic fibers were found in all regions, and were disposed in different directions in the areas under compressive forces, and parallel to the collagen bundles in the region under tension. These results reinforce the idea that mechanical forces contribute to a differentiated composition and organization of the extracellular matrix of tendons.
Assuntos
Glicosaminoglicanos/análise , Tendões/citologia , Animais , Tamanho Celular , Eletroforese em Gel de Ágar/métodos , Glicosaminoglicanos/isolamento & purificação , Membro Posterior , Histocitoquímica/métodos , Especificidade de Órgãos , SuínosRESUMO
Elastic system components have been described in the pressure-bearing tendon of the bullfrog, Rana catesbeiana, as a result of histochemical tests and transmission and scanning electron microscopy. The tension region was shown to possess microfibril bundles, some of which exhibited central deposits of amorphous material. The use of ANS-butanol plus fluorescence microscopy enormously facilitated the identification of elastic system components in both tension and compression regions of the frog tendon. The compression region exhibited pre-elastic and mature elastic fibers, which were shown to be associated with the surface of the convoluted collagen bundles. Thin fibrils were observed in the compression region after ANS treatment. The visceral paratenon had an increased number of elastic fibers located between the collagen bundles and close to the cells. Congo red plus polarization microscopy failed to impart birefringence to the elastic fibers, but they could be identified by their intense staining and isotropic appearance against the bright background of birefringent collagen fibers. SEM demonstrated the three-dimensional aspects of the elastic fibers. They are composed of fibrils of a sinuous nature. The use of ruthenium red in the fixative allowed for the observation of an intimate association of proteoglycan granules with the microfibril bundles. The elastic components identified in the pressure-bearing tendon are assumed to be important for the tissue supramolecular organization, especially in the maintenance of the convoluted state of the collagen fibers in the compression region and their crimp morphology in the tension region. The elastic system must also play an important role in the restoration of the resting shape of the tendon after the deformation achieved during mechanical stimulation.