Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 6 de 6
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
J Biomech Eng ; 146(6)2024 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-37792487

RESUMO

During pregnancy and breastfeeding, women undergo hormonal fluctuations required for fetal development, parturition, and infant growth. These changes have secondary consequences on the maternal musculoskeletal system, increasing the risk for joint pain and osteoporosis. Though hormone levels return to prepregnancy levels postpartum, women may experience lasting musculoskeletal pain. Sex disparities exist in the prevalence of musculoskeletal disorders, but it remains unclear how reproductive history may impact sex differences. Specifically, the effects of both reproductive history and sex on the rotator cuff have not been studied. Pregnancy and lactation affect bone microstructure, suggesting possible impairments at the enthesis of rotator cuff tendons, where tears commonly occur. Therefore, our objective was to evaluate how reproductive history affects sex differences of the supraspinatus tendon and proximal humerus using male, virgin female, and female rats with a history of reproduction (referred to as reproductive females). We hypothesized tendon mechanical properties and humeral bone microstructure would be inferior in reproductive females compared to virgin females. Results showed sex differences independent of reproductive history, including greater tendon midsubstance modulus but lower subchondral bone mineral density (BMD) in females. When considering reproductive history, reproductive rats exhibited reduced tendon insertion site modulus and trabecular bone micro-architecture compared to virgin females with no differences from males. Overall, our study identified long-term changes in supraspinatus tendon mechanical and humeral trabecular bone properties that result following pregnancy and lactation, highlighting the importance of considering reproductive history in investigations of sex differences in the physiology and pathology of rotator cuff injuries.


Assuntos
Lesões do Manguito Rotador , Manguito Rotador , Humanos , Gravidez , Ratos , Feminino , Masculino , Animais , Manguito Rotador/patologia , Aleitamento Materno , Fenômenos Biomecânicos , Lesões do Manguito Rotador/patologia , Reprodução , Tendões , Úmero , Lactação
2.
Connect Tissue Res ; 64(1): 75-81, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-35816119

RESUMO

PURPOSE: A growing interest in the mechanisms that govern tendon healing has resulted in the develop-ment of tools, such as the tamoxifen-inducible mouse knockdown model, to address these questions. However, tamoxifen is a selective estrogen receptor modulator and may interfere with the tendon healing process. The objective of this study was to evaluate the effects of tamoxifen on post-injury tendon mechanics in wild-type mice. METHODS: The mice underwent treatment at the time of injury using an established mouse injury model and the injured tendons were evaluated 3 weeks post-injury. The treatment contained tamoxifen suspended in corn oil and was compared to a treatment with only corn oil, as well as mice with no treatment. Tendons were evaluated by measuring the quasi-static and viscoelastic mechanics, collagen fiber realignment, cellularity, and nuclear morphology. RESULTS: Mechanical testing of the tendons post-injury revealed no changes to viscoelastic mechanics, quasi-static mechanics, or collagen realignment during loading after tamoxifen treatment with the dosage regimen utilized (three daily injections of 4.5 mg/40 g body weight). Additionally, histological analysis revealed no changes to cellularity or cell nuclear shape. CONCLUSION: Overall, this study revealed that tamoxifen treatment at the time of tendon injury did not result in changes to tendon mechanics or the histological parameters at 3 weeks post-injury.


Assuntos
Tamoxifeno , Traumatismos dos Tendões , Camundongos , Animais , Tamoxifeno/farmacologia , Óleo de Milho , Tendões/patologia , Traumatismos dos Tendões/patologia , Colágeno , Modelos Animais de Doenças
3.
J Biomech Eng ; 142(11)2020 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-32577720

RESUMO

Pregnant women experience weight gain, gait changes, and biochemical fluctuations that impair joint function and alter the maternal skeleton. Hormonal changes increase pelvic ligament laxity in preparation for childbirth and affect peripheral joint laxity. Calcium demands also rise during pregnancy and lactation, resulting in reduced bone mineral density (BMD) and maternal bone loss. Altered tendon properties and bone loss during pregnancy and lactation may impact tendon insertion sites, such as rotator cuff tendons where insertion site ruptures are common. However, the effects of pregnancy and lactation at the tendon-to-bone interface have not been investigated. Therefore, the objective of this study was to evaluate supraspinatus tendon mechanical properties and insertion site microstructure during pregnancy, lactation, and postweaning recovery in female rats. We hypothesized that pregnancy and lactation would compromise supraspinatus tendon mechanical properties and subchondral bone microstructure. Female rats were divided into virgin, pregnancy, lactation, and recovery groups, and supraspinatus tendons were mechanically evaluated. Surprisingly, tendon mechanics was unaffected by pregnancy and lactation. However, tendon modulus decreased two-weeks postweaning. Additionally, tendons failed by bony avulsion at the insertion site, and the lactation group exhibited reduced failure properties corresponding to decreased subchondral bone mineralization. Lactation also resulted in dramatic bone loss at the epiphysis, but trabecular bone microarchitecture recovered postweaning. In conclusion, lactation following pregnancy impaired trabecular bone microstructure and subchondral bone mineralization, leading to reduced supraspinatus tendon-to-bone insertion site failure properties. These findings will contribute toward understanding the pathogenesis of tendon-to-bone disorders.


Assuntos
Manguito Rotador , Animais , Feminino , Gravidez , Ratos , Traumatismos dos Tendões , Tendões
4.
J Orthop Res ; 41(10): 2238-2249, 2023 10.
Artigo em Inglês | MEDLINE | ID: mdl-37132501

RESUMO

The small leucine-rich proteoglycans, decorin and biglycan, are minor components of the tendon extracellular matrix that regulate fibrillogenesis and matrix assembly. Our study objective was to define the temporal roles of decorin and biglycan during tendon healing using inducible knockout mice to include genetic knockdown at specific phases of healing: time of injury, the proliferative phase, and the remodeling phase. We hypothesized that knockdown of decorin or biglycan would adversely affect tendon healing, and that by prescribing the timing of knockdown, we could elucidate the temporal roles of these proteins during healing. Contrary to our hypothesis, decorin knockdown did not affect tendon healing. However, when biglycan was knocked down, either alone or coupled with decorin, tendon modulus was increased relative to wild-type mice, and this finding was consistent among all induction timepoints. At 6 weeks postinjury, we observed increased expression of genes associated with the extracellular matrix and growth factor signaling in the biglycan knockdown and compound decorin-biglycan knockdown tendons. Interestingly, these groups demonstrated opposing trends in gene expression as a function of knockdown-induction timepoint, highlighting distinct temporal roles for decorin and biglycan. In summary, this study finds that biglycan plays multiple functions throughout tendon healing, with the most impactful, detrimental role likely occurring during late-stage healing. Statement of clinical importance: This study helps to define the molecular factors that regulate tendon healing, which may aid in the development of new clinical therapies.


Assuntos
Tendões , Cicatrização , Animais , Camundongos , Biglicano/genética , Biglicano/metabolismo , Decorina , Proteínas da Matriz Extracelular/metabolismo , Camundongos Knockout , Tendões/fisiologia , Cicatrização/fisiologia
5.
Am J Sports Med ; 50(1): 170-181, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34851182

RESUMO

BACKGROUND: Achilles tendon ruptures are painful and debilitating injuries and are most common in middle-aged patients. There is a lack of understanding of the underlying causes for increased rupture rates in middle-aged patients and how healing outcomes after a rupture might be affected by patient age. Therefore, the objective of this study was to define age-specific Achilles tendon healing by assessing ankle functional outcomes and Achilles tendon mechanical and histological properties after a rupture using a rat model. HYPOTHESIS: Rats representing the middle-aged patient population would demonstrate reduced healing capability after an Achilles tendon rupture, as demonstrated by a slower return to baseline ankle functional properties and inferior biomechanical and histological tendon properties. STUDY DESIGN: Controlled laboratory study. METHODS: Fischer 344 rats were categorized by age to represent young, middle-aged, and old patients, and Achilles tendon ruptures were induced in the right hindlimb. Animals were allowed to heal and were euthanized at 3 or 6 weeks after the injury. In vivo functional assays and ultrasound imaging were performed throughout the healing period, and ex vivo tendon mechanical and histological properties were assessed after euthanasia. RESULTS: Rats representing middle-aged patients displayed reduced healing potential compared with the other age groups, as they demonstrated decreased recovery of in vivo functional and ultrasound assessment parameters and inferior mechanical and histological properties after an Achilles tendon rupture. CONCLUSION: These findings may help explain the increased rupture rate observed clinically in middle-aged patients by suggesting that there may be altered tendon responses to daily trauma. CLINICAL RELEVANCE: The results provide novel data on age-specific healing outcomes after an Achilles tendon rupture, which underscores the importance of considering a patient's age during treatment and expectations for outcomes.


Assuntos
Tendão do Calcâneo , Traumatismos dos Tendões , Tendão do Calcâneo/diagnóstico por imagem , Animais , Humanos , Ratos , Ratos Endogâmicos F344 , Ruptura , Resultado do Tratamento , Cicatrização
6.
J Biomech ; 67: 184-189, 2018 01 23.
Artigo em Inglês | MEDLINE | ID: mdl-29248194

RESUMO

Macroscopic tendon loads modulate the cellular microenvironment leading to biological outcomes such as degeneration or repair. Previous studies have shown that damage accumulation and the phases of tendon healing are marked by significant changes in the extracellular matrix, but it remains unknown how mechanical forces of the extracellular matrix are translated to mechanotransduction pathways that ultimately drive the biological response. Our overarching hypothesis is that the unique relationship between extracellular matrix strain and cell deformation will dictate biological outcomes, prompting the need for quantitative methods to characterize the local strain environment. While 2-D methods have successfully calculated matrix strain and cell deformation, 3-D methods are necessary to capture the increased complexity that can arise due to high levels of anisotropy and out-of-plane motion, particularly in the disorganized, highly cellular, injured state. In this study, we validated the use of digital volume correlation methods to quantify 3-D matrix strain using images of naïve tendon cells, the collagen fiber matrix, and injured tendon cells. Additionally, naïve tendon cell images were used to develop novel methods for 3-D cell deformation and 3-D cell-matrix strain, which is defined as a quantitative measure of the relationship between matrix strain and cell deformation. The results support that these methods can be used to detect strains with high accuracy and can be further extended to an in vivo setting for observing temporal changes in cell and matrix mechanics during degeneration and healing.


Assuntos
Matriz Extracelular/metabolismo , Imageamento Tridimensional , Estresse Mecânico , Tendões/citologia , Tendões/efeitos dos fármacos , Animais , Anisotropia , Humanos , Mecanotransdução Celular
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA