scholarly journals Validation of an Empirical Damage Model for Aging and in Vivo Injury of the Murine Patellar Tendon

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Mark R. Buckley ◽  
Andrew A. Dunkman ◽  
Katherine E. Reuther ◽  
Akash Kumar ◽  
Lydia Pathmanathan ◽  
...  
Keyword(s):  
Soft Tissues ◽  
Damage Model ◽  
Damage Parameter ◽  
Post Injury ◽  
Equilibrium Stress ◽  
Physiological Loading ◽  
Age Related ◽  
Injury Group ◽  
Old Mice

While useful models have been proposed to predict the mechanical impact of damage in tendon and other soft tissues, the applicability of these models for describing in vivo injury and age-related degeneration has not been investigated. Therefore, the objective of this study was to develop and validate a simple damage model to predict mechanical alterations in mouse patellar tendons after aging, injury, or healing. To characterize baseline properties, uninjured controls at age 150 days were cyclically loaded across three strain levels and five frequencies. For comparison, damage was induced in mature (120 day-old) mice through either injury or aging. Injured mice were sacrificed at three or six weeks after surgery, while aged mice were sacrificed at either 300 or 570 days old. Changes in mechanical properties (relative to baseline) in the three week post-injury group were assessed and used to develop an empirical damage model based on a simple damage parameter related to the equilibrium stress at a prescribed strain (6%). From the derived model, the viscoelastic properties of the 300 day-old, 570 day-old, and six week post-injury groups were accurately predicted. Across testing conditions, nearly all correlations between predicted and measured parameters were statistically significant and coefficients of determination ranged from R2 = 0.25 to 0.97. Results suggest that the proposed damage model could exploit simple in vivo mechanical measurements to predict how an injured or aged tendon will respond to complex physiological loading regimens.

scholarly journals A damage model for collagen fibres with an application to collagenous soft tissues

2020 ◽  
Vol 476 (2236) ◽  
pp. 20190821
Author(s):  
Gerhard A. Holzapfel ◽  
Ray W. Ogden
Keyword(s):  
Soft Tissues ◽  
Damage Model ◽  
Three Dimensional ◽  
Collagen Fibres ◽  
Physiological Loading ◽  
Cross Links ◽  
Complex Boundary ◽  
Tail Tendon ◽  
Similar Basis ◽  
Rat Tail

We propose a mechanical model to account for progressive damage in collagen fibres within fibrous soft tissues. The model has a similar basis to the pseudoelastic model that describes the Mullins effect in rubber but it also accounts for the effect of cross-links between collagen fibres. We show that the model is able to capture experimental data obtained from rat tail tendon fibres, and the combined effect of damage and collagen cross-links is illustrated for a simple shear test. The proposed three-dimensional framework allows a straightforward implementation in finite-element codes, which are needed to analyse more complex boundary-value problems for soft tissues under supra-physiological loading or tissues weakened by disease.

scholarly journals Global Gene Expression Analysis Identifies Age-Related Differences in Knee Joint Transcriptome during the Development of Post-Traumatic Osteoarthritis in Mice

2020 ◽  
Vol 21 (1) ◽  
pp. 364 ◽  
Author(s):  
Aimy Sebastian ◽  
Deepa K. Murugesh ◽  
Melanie E. Mendez ◽  
Nicholas R. Hum ◽  
Naiomy D. Rios-Arce ◽  
...  
Keyword(s):  
Knee Joint ◽  
Age Groups ◽  
Knee Joints ◽  
Compression Injury ◽  
Post Injury ◽  
Transcriptional Responses ◽  
Molecular Changes ◽  
Age Related ◽  
Post Traumatic ◽  
Old Mice

Aging and injury are two major risk factors for osteoarthritis (OA). Yet, very little is known about how aging and injury interact and contribute to OA pathogenesis. In the present study, we examined age- and injury-related molecular changes in mouse knee joints that could contribute to OA. Using RNA-seq, first we profiled the knee joint transcriptome of 10-week-old, 62-week-old, and 95-week-old mice and found that the expression of several inflammatory-response related genes increased as a result of aging, whereas the expression of several genes involved in cartilage metabolism decreased with age. To determine how aging impacts post-traumatic arthritis (PTOA) development, the right knee joints of 10-week-old and 62-week-old mice were injured using a non-invasive tibial compression injury model and injury-induced structural and molecular changes were assessed. At six-week post-injury, 62-week-old mice displayed significantly more cartilage degeneration and osteophyte formation compared with young mice. Although both age groups elicited similar transcriptional responses to injury, 62-week-old mice had higher activation of inflammatory cytokines than 10-week-old mice, whereas cartilage/bone metabolism genes had higher expression in 10-week-old mice, suggesting that the differential expression of these genes might contribute to the differences in PTOA severity observed between these age groups.

scholarly journals HDAC6 inactivates Runx2 promoter to block osteogenesis of bone marrow stromal cells in age-related bone loss of mice

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chao Ma ◽  
Juan Gao ◽  
Jun Liang ◽  
Weixiang Dai ◽  
Zhenfei Wang ◽  
...  
Keyword(s):  
Bone Loss ◽  
Bone Formation ◽  
Osteogenic Differentiation ◽  
Differentiation Potential ◽  
Runx2 Expression ◽  
Aged Mice ◽  
Age Related ◽  
Old Mice

Abstract Background Senile osteoporosis can cause bone fragility and increased risk for fractures and has been one of the most prevalent and severe diseases affecting the elderly population worldwidely. The underlying mechanisms are currently intensive areas of investigation. In age-related bone loss, decreased bone formation overweighs increased bone resorption. The molecular mechanisms underlying defective bone formation in age-related bone loss are not completely understood. In particular, the specific role of histone acetylation in age-related bone loss has not been examined thoroughly. Methods We employed 6- and 18-month-old mice to investigate the mechanisms of defective bone formation in age-related bone loss. Bone marrow stromal cells (BMSCs) were induced to undergo in vitro osteogenic differentiation. Chromatin immunoprecipitation (ChIP) was used to investigate the binding of histone deacetylases (HDACs) on Runx2 promoter in BMSCs. Luciferase reporter and transient transfection assay were employed to study Runx2 gene expression modulation by HDAC and androgen receptor (AR). siRNA and HDAC6 inhibitor, Tubastatin A, were used to inhibit HDAC6 in vitro. And systemic administration of Tubastatin A was used to block HDAC6 in vivo. Results Age-related trabecular bone loss was observed in 18-month-old mice compared with 6-month-old mice. In vitro osteogenic differentiation potential of BMSCs from 18-month-old mice was weaker than 6-month-old mice, in which there was Runx2 expression inactivation in BMSCs of 18-month-old mice compared with 6-month-old mice, which was attributable to HDAC6-mediated histone hypoacetylation in Runx2 promoter. There was competitive binding of HDAC6 and AR on Runx2 promoter to modulate Runx2 expression in BMSCs. More importantly, through siRNA- or specific inhibitor-mediated HDAC6 inhibition, we could activate Runx2 expression, rescue in vitro osteogenesis potential of BMSCs, and alleviate in vivo age-related bone loss of mice. Conclusion HDAC6 accumulation and histone hypoacetylation on Runx2 promoter contributed to the attenuation of in vitro osteogenic differentiation potential of BMSCs from aged mice. Through HDAC6 inhibition, we could activate Runx2 expression and osteogenic differentiation potential of BMSCs from aged mice and alleviate the age-related bone loss of aged mice. Our study will benefit not only for understanding the age-related bone loss, but also for finding new therapies to treat senile osteoporosis.

scholarly journals Healthy Brain Aging Modifies Microglial Calcium Signaling In Vivo

2019 ◽  
Vol 20 (3) ◽  
pp. 589 ◽  
Author(s):  
Maria Olmedillas del Moral ◽  
Nithi Asavapanumas ◽  
Néstor Uzcátegui ◽  
Olga Garaschuk
Keyword(s):  
Young Adult ◽  
Brain Aging ◽  
Critical Role ◽  
Low Grade ◽  
Middle Aged ◽  
Senescent Phenotype ◽  
Adult Mice ◽  
Age Related ◽  
Old Mice

Brain aging is characterized by a chronic, low-grade inflammatory state, promoting deficits in cognition and the development of age-related neurodegenerative diseases. Malfunction of microglia, the brain-resident immune cells, was suggested to play a critical role in neuroinflammation, but the mechanisms underlying this malfunctional phenotype remain unclear. Specifically, the age-related changes in microglial Ca2+ signaling, known to be linked to its executive functions, are not well understood. Here, using in vivo two-photon imaging, we characterize intracellular Ca2+ signaling and process extension of cortical microglia in young adult (2–4-month-old), middle-aged (9–11-month-old), and old (18–21-month-old) mice. Our data revealed a complex and nonlinear dependency of the properties of intracellular Ca2+ signals on an animal’s age. While the fraction of cells displaying spontaneous Ca2+ transients progressively increased with age, the frequencies and durations of the spontaneous Ca2+ transients followed a bell-shaped relationship, with the most frequent and largest Ca2+ transients seen in middle-aged mice. Moreover, in old mice microglial processes extending toward an ATP source moved faster but in a more disorganized manner, compared to young adult mice. Altogether, these findings identify two distinct phenotypes of aging microglia: a reactive phenotype, abundantly present in middle-aged animals, and a dysfunctional/senescent phenotype ubiquitous in old mice.

scholarly journals Serine and Glycine Are Essential for Skeletal Muscle Regeneration Following Injury

2020 ◽  
Vol 4 (Supplement_2) ◽  
pp. 81-81
Author(s):  
Anna Thalacker-Mercer ◽  
Jamie Blum ◽  
Brandon Gheller
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Essential Amino Acids ◽  
Regenerative Process ◽  
Skeletal Muscle Regeneration ◽  
Post Injury ◽  
Foreign Study ◽  
Funding Sources ◽  
Age Related ◽  
Old Mice

Abstract Objectives Skeletal muscle (SkM) regeneration post injury is reliant on SkM-specific stem cells (muscle progenitor cells [MPCs]) and a well-orchestrated myogenic program. The regenerative process is impaired with advancing age, potentiating pathological SkM remodeling (infiltration of fat and fibrotic tissues). We have previously demonstrated that the nutritionally non-essential amino acids serine (Ser) and glycine (Gly) are required for early stages of SkM regeneration (MPC proliferation). However, Ser and Gly availability (SkM and circulating) declines with aging. The objective was to test the hypothesis that reduced endogenous Ser/Gly during regeneration promotes pathological SkM remodeling in aged animals. Methods Old mice (∼20 months of age) were given a Ser/Gly depleted diet (SGdep) or an isonitrogenous, isoenergetic diet containing Ser/Gly (SGcont) for 4 weeks followed by notexin-induced injury to the tibialis anterior (TA) SkM. At 28 days post injury the TA was harvested and histological analysis of SkM morphology (H&E and immunofluorescence [IF]) and gene expression analyses (qPCR) were completed. Results Old mice receiving the SGdep diet had a shift toward reduced myofiber size and enhanced adipocyte infiltration in the SkM. Adipocyte infiltration was confirmed with IF of perilipin-1, an adipocyte marker. Uninjured mice on the SGdep diet did not demonstrate altered SkM morphology. Gene expression analysis of differentially expressed genes underlying SkM remodeling (reduced myofiber size and increased fat infiltration) with SGdep is ongoing. Conclusions Reduced Ser and Gly availability following injury instigates SkM remodeling in old mice, which could explain in part age-related impairments in SkM regeneration. This research underscores the essentiality of Ser and Gly for the SkM regenerative process particularly with advancing age. Funding Sources Canadian Institutes of Health Research Doctoral Foreign Study Award to BG.

scholarly journals Integrated in vivo quantitative proteomics and nutrient tracing reveals age-related metabolic rewiring of pancreatic β-cell function

2018 ◽  
Author(s):  
Matthew Wortham ◽  
Jacqueline R. Benthuysen ◽  
Martina Wallace ◽  
Jeffrey N. Savas ◽  
Francesca Mulas ◽  
...  
Keyword(s):  
Cell Function ◽  
Coupling Factor ◽  
Pancreatic Β Cell ◽  
Β Cell ◽  
Age Related ◽  
Β Cell Function ◽  
One Year ◽  
Old Mice ◽  
Age Related Changes

SummaryPancreatic β-cell physiology changes substantially throughout life; yet, the mechanisms that drive these changes are poorly understood. Here, we performed comprehensive in vivo quantitative proteomic profiling of pancreatic islets from adolescent and one-year-old mice. The analysis revealed striking differences in abundance of enzymes controlling glucose metabolism. We show that these changes in protein abundance are associated with higher activities of glucose metabolic enzymes involved in coupling factor generation as well as increased activity of the coupling factor-dependent amplifying pathway of insulin secretion. Nutrient tracing and targeted metabolomics demonstrated accelerated accumulation of glucose-derived metabolites and coupling factors in islets from one-year-old mice, indicating that age-related changes in glucose metabolism contribute to improved glucose-stimulated insulin secretion with age. Together, our study provides the first in-depth characterization of age-related changes in the islet proteome and establishes metabolic rewiring as an important mechanism for age-associated changes in β-cell function.

scholarly journals In vivo imaging of axonal transport of mitochondria in the diseased and aged mammalian CNS

2015 ◽  
Vol 112 (33) ◽  
pp. 10515-10520 ◽  
Author(s):  
Yuji Takihara ◽  
Masaru Inatani ◽  
Kei Eto ◽  
Toshihiro Inoue ◽  
Alexander Kreymerman ◽  
...  
Keyword(s):  
Axonal Transport ◽  
Ganglion Cells ◽  
Early Stage ◽  
Time Lapse ◽  
Multiphoton Imaging ◽  
Age Related ◽  
Old Mice ◽  
Related Increase ◽  
Mammalian Cns

The lack of intravital imaging of axonal transport of mitochondria in the mammalian CNS precludes characterization of the dynamics of axonal transport of mitochondria in the diseased and aged mammalian CNS. Glaucoma, the most common neurodegenerative eye disease, is characterized by axon degeneration and the death of retinal ganglion cells (RGCs) and by an age-related increase in incidence. RGC death is hypothesized to result from disturbances in axonal transport and in mitochondrial function. Here we report minimally invasive intravital multiphoton imaging of anesthetized mouse RGCs through the sclera that provides sequential time-lapse images of mitochondria transported in a single axon with submicrometer resolution. Unlike findings from explants, we show that the axonal transport of mitochondria is highly dynamic in the mammalian CNS in vivo under physiological conditions. Furthermore, in the early stage of glaucoma modeled in adult (4-mo-old) mice, the number of transported mitochondria decreases before RGC death, although transport does not shorten. However, with increasing age up to 23–25 mo, mitochondrial transport (duration, distance, and duty cycle) shortens. In axons, mitochondria-free regions increase and lengths of transported mitochondria decrease with aging, although totally organized transport patterns are preserved in old (23- to 25-mo-old) mice. Moreover, axonal transport of mitochondria is more vulnerable to glaucomatous insults in old mice than in adult mice. These mitochondrial changes with aging may underlie the age-related increase in glaucoma incidence. Our method is useful for characterizing the dynamics of axonal transport of mitochondria and may be applied to other submicrometer structures in the diseased and aged mammalian CNS in vivo.

scholarly journals Phytoecdysteroids Accelerate Recovery of Skeletal Muscle Function Following in vivo Eccentric Contraction-Induced Injury in Adult and Old Mice

2021 ◽  
Vol 2 ◽  
Author(s):  
Kevin A. Zwetsloot ◽  
R. Andrew Shanely ◽  
Joshua S. Godwin ◽  
Charles F. Hodgman
Keyword(s):  
Skeletal Muscle ◽  
Muscle Damage ◽  
Muscle Function ◽  
Recovery Period ◽  
Eccentric Contraction ◽  
Eccentric Contractions ◽  
Post Injury ◽  
Skeletal Muscle Function ◽  
Old Mice

Background: Eccentric muscle contractions are commonly used in exercise regimens, as well as in rehabilitation as a treatment against muscle atrophy and weakness. If repeated multiple times, eccentric contractions may result in skeletal muscle injury and loss of function. Skeletal muscle possesses the remarkable ability to repair and regenerate after an injury or damage; however, this ability is impaired with aging. Phytoecdysteroids are natural plant steroids that possess medicinal, pharmacological, and biological properties, with no adverse side effects in mammals. Previous research has demonstrated that administration of phytoecdysteroids, such as 20-hydroxyecdysone (20E), leads to an increase in protein synthesis signaling and skeletal muscle strength.Methods: To investigate whether 20E enhances skeletal muscle recovery from eccentric contraction-induced damage, adult (7–8 mo) and old (26–27 mo) mice were subjected to injurious eccentric contractions (EC), followed by 20E or placebo (PLA) supplementation for 7 days. Contractile function via torque-frequency relationships (TF) was measured three times in each mouse: pre- and post-EC, as well as after the 7-day recovery period. Mice were anesthetized with isoflurane and then electrically-stimulated isometric contractions were performed to obtain in vivo muscle function of the anterior crural muscle group before injury (pre), followed by 150 EC, and then again post-injury (post). Following recovery from anesthesia, mice received either 20E (50 mg•kg−1 BW) or PLA by oral gavage. Mice were gavaged daily for 6 days and on day 7, the TF relationship was reassessed (7-day).Results: EC resulted in significant reductions of muscle function post-injury, regardless of age or treatment condition (p < 0.001). 20E supplementation completely recovered muscle function after 7 days in both adult and old mice (pre vs. 7-day; p > 0.05), while PLA muscle function remained reduced (pre vs. 7-day; p < 0.01). In addition, histological markers of muscle damage appear lower in damaged muscle from 20E-treated mice after the 7-day recovery period, compared to PLA.Conclusions: Taken together, these findings demonstrate that 20E fully recovers skeletal muscle function in both adult and old mice just 7 days after eccentric contraction-induced damage. However, the underlying mechanics by which 20E contributes to the accelerated recovery from muscle damage warrant further investigation.

scholarly journals Senescence Is Associated With Elevated Intracellular Resting [Ca2 +] in Mice Skeletal Muscle Fibers. An in vivo Study

2021 ◽  
Vol 11 ◽  
Author(s):  
Alfredo Mijares ◽  
Paul D. Allen ◽  
Jose R. Lopez
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Muscle Cells ◽  
Ros Production ◽  
Middle Aged ◽  
Age Related ◽  
Tnf Α ◽  
Intracellular Ca ◽  
Old Mice

Aging causes skeletal muscles to become atrophied, weak, and easily fatigued. Here, we have tested the hypothesis that normal aging in skeletal muscle cells is associated with Ca2+ intracellular dyshomeostasis and oxidative stress. Intracellular Ca2+ concentration ([Ca2+]i), resting intracellular Na+ concentration ([Na+]i) and reactive oxygen species (ROS) production were measured in vivo (superficial gastrocnemius fibers) using double-barreled ion-selective microelectrodes, and in vitro [isolated single flexor digitorum brevis fibers] using fluorescent ROS sensor CM-H2DCFDA in young (3 months of age), middle-aged (12 months of age), and aged (24 months of age) mice. We found an age-related increase in [Ca2+]i from 121 ± 4 nM in young muscle cells which rose to 255 ± 36 nM in middle-aged and to 409 ± 25 nM in aged cells. [Na+]i also showed an age-dependent elevation, increasing from 8 ± 0.5 mM in young muscle fibers, to 12 ± 1 mM in middle-aged and to 17 ± 1 mM in old muscle fibers. Using the fluorescent ROS sensor CM-H2DCFDA we found that these increases in intracellular cation concentrations were associated with significantly increased basal ROS production as demonstrated by age related increases in the rate of dichlorodihydrofluorescein fluorescence. To determine is this could be modified by reducing ROS and/or blocking sarcolemmal Ca2+ influx we administered flufenamic acid (FFA), a non-steroidal anti-inflammatory drug which is also a non-selective blocker of the transient receptor potential canonical channels (TRPCs), for 4 weeks to determine if this would have a beneficial effect. FFA treatment reduced both basal ROS production and muscle [Ca2+]i and [Na+]i in middle-aged and aged muscle fibers compared to fibers and muscles of untreated 12 and 24-months old mice. [Ca2+]i was reduced to 134 ± 8 nM in middle-aged muscle and to 246 ± 40 nM in muscle from aged mice. Likewise [Na+]i was reduced to 9 ± 0.7 mM in middle-aged muscles and to 13 ± 1 mM in muscle from aged mice. FFA treatment also reduced age associated increases in plasma interleukin 6 and tumor necrosis factor-alpha (TNF-α) concentrations which were elevated in 12 and 24-months old mice compared to young mice and decreased age-related muscle damage as indicated by a reduction in serum creatine kinase (CK) activity. Our data provides a direct demonstration that normal aging is associated with a significant elevation [Ca2+]i, [Na+]i, and intracellular ROS production in skeletal muscle fibers. Furthermore, the fact that FFA reduced the intracellular [Ca2+], [Na+], and ROS production as well as the elevated IL6, TNF-α, and CK levels, led us to suggest that its pharmacological effect may be related to its action both as a TRPC channel blocker and as an anti-inflammatory.

Biological and biomedical applications of collagenous biomaterials

1990 ◽  
Vol 48 (3) ◽  
pp. 856-857
Author(s):  
Yasushi P. Kato ◽  
Michael G. Dunn ◽  
Frederick H. Silver ◽  
Arthur J. Wasserman
Keyword(s):  
Biomedical Applications ◽  
Soft Tissues ◽  
Collagen Fibers ◽  
Bone Collagen ◽  
Cover Slip ◽  
Fibroblast Migration ◽  
Cellular Expression ◽  
Defect Repair

Collagenous biomaterials have been used for growing cells in vitro as well as for augmentation and replacement of hard and soft tissues. The substratum used for culturing cells is implicated in the modulation of phenotypic cellular expression, cellular orientation and adhesion. Collagen may have a strong influence on these cellular parameters when used as a substrate in vitro. Clinically, collagen has many applications to wound healing including, skin and bone substitution, tendon, ligament, and nerve replacement. In this report we demonstrate two uses of collagen. First as a fiber to support fibroblast growth in vitro, and second as a demineralized bone/collagen sponge for radial bone defect repair in vivo.For the in vitro study, collagen fibers were prepared as described previously. Primary rat tendon fibroblasts (1° RTF) were isolated and cultured for 5 days on 1 X 15 mm sterile cover slips. Six to seven collagen fibers, were glued parallel to each other onto a circular cover slip (D=18mm) and the 1 X 15mm cover slip populated with 1° RTF was placed at the center perpendicular to the collagen fibers. Fibroblast migration from the 1 x 15mm cover slip onto and along the collagen fibers was measured daily using a phase contrast microscope (Olympus CK-2) with a calibrated eyepiece. Migratory rates for fibroblasts were determined from 36 fibers over 4 days.

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