American journal of physiology. Cell physiology最新文献

Most mammals produce vocal signals through vocal fold oscillations in the larynx, driven by airflow. Common species used as models (e.g., house mice, rats, and rabbits) may not reflect the cellular specializations or developmental adaptations needed to support diverse vocal strategies or tissue repair under the mechanical stresses of phonation in humans. This study investigates vocal fold structure and function in California mice (Peromyscus californicus) to inform a new model of vocal fold biomechanics. These mice can produce extremely high fundamental frequencies (f₀) via airflow-induced vocal fold vibration and maintain this ability throughout life. We examined how vocal fold structure relates to function in California mice across three developmental stages. Vocal folds grow with negative allometry, undergoing changes in shape and composition. The epithelium is made up of 1-2 layers of squamous cells, and the lamina propria contains a fibrous matrix rich in collagen and hyaluronan but low in elastin. In vitro, California mouse vocal fold fibroblasts differed from those of house mice (Mus musculus) in size, shape, and α-smooth muscle actin expression. In addition, intrinsic laryngeal muscle myofibers doubled in diameter during the first 3 wk of life. We propose that the differentiated allometric growth of the larynx and vocal folds helps stabilize f₀ across development. A species-specific fibroblast phenotype may support vibration and enhance tissue resilience. These findings suggest that cellular adaptations in the vocal folds may play a larger role in species-specific vocal function and stability than previously recognized.NEW & NOTEWORTHY California mice produce high-pitched vocalizations through specialized vocal fold structures that grow and develop uniquely across life stages. Unlike common lab species, their vocal folds show distinct cellular traits that support vibration and durability. This study highlights key differences in tissue composition and fibroblast behavior, suggesting that species-specific vocal fold adaptations may be crucial for stable vocal function-offering new insights into voice biomechanics and potential models for human vocal health research.

Eccentric exercise has been shown to increase serial sarcomere number (SSN) through sarcomerogenesis in both animal and human models. However, eccentric contractions rarely occur in isolation and are often used in conjunction with concentric movements, limiting the ability to evoke a maximal eccentric contraction. Eccentric overload training provides an increased eccentric stimulus, yet its impact on muscle morphology and mechanics is not widely understood. We compared the effects of eccentric overload training (ECC_OVERLOAD) and conventional resistance training (CONV) on morphological [SSN, fascicle length (FL), sarcomere length (SL), physiological cross-sectional area (PCSA), wet weight] and mechanical changes (torque, normalized torque, power, passive torque) pre- to post-training. Nineteen Sprague-Dawley (n = 10; ECC_OVERLOAD, n = 9; CONV) male and female rats (13-14 wk, 317 g) completed 4 wk (3× week) of training. SSN increased with training by 17% in the soleus (P < 0.001) and 6% in the medial gastrocnemius (P = 0.021) in the ECC_OVERLOAD group, compared with 2% and 4% in the CONV group. Peak plantar flexion torque increased ∼27% in the ECC_OVERLOAD and ∼21% in the CONV group (P < 0.001) but did not differ between groups (P = 0.318). There was a 26% increase in normalized torque for the ECC_OVERLOAD, as compared with 2.5% in the CONV group at 90°, demonstrating an interaction of training × group (P < 0.001). Power increased ∼9%, with an interaction of sex × training × group (P = 0.021) driven by increases in torque at peak power in the ECC_OVERLOAD male group. These findings indicate that overload training provided a more robust stimulus for longitudinal muscle remodeling than conventional resistance training.NEW & NOTEWORTHY Eccentric overload training promotes greater sarcomerogenesis than conventional resistance training in male and female rats.

Duchenne muscular dystrophy (DMD) is one of the most severe forms of inheritable muscular dystrophies, caused by a genetic mutation resulting in the loss of dystrophin. Dystrophin loss initiates a cascade of negative mechanistic changes in skeletal muscle, such as disrupted protein homeostasis and mitochondrial dysfunction. Recent evidence suggests the leucine metabolite, β-hydroxy-β-methylbutyrate (HMB), may improve physical function in DMD boys and improve aspects of the dystrophic phenotype in preclinical mdx mice. HMB has been shown to modulate protein turnover and mitochondrial function, both of which are dysregulated in DMD. Therefore, this study examined the effect of 3-wk of HMB supplementation (0.75 mg/g/day via drinking water), starting at 3-wk of age in mdx mice. HMB-treated mdx mice exhibited increased full-body grip strength and holding impulse, compared with mdx controls. HMB treatment also increased normalized muscle mass of the fast-twitch extensor digitorum longus (EDL) muscle, which coincided with increased average fiber size and improved absolute/specific in vitro force production. Moreover, HMB-treated EDL muscles displayed increased mitochondrial complex II succinate dehydrogenase activity, alongside upregulated markers of mammalian target of rapamycin complex 1 (mTORC1) signalling (p70S6K1 and 4EBP1 phosphorylation), suggestive of increased protein synthesis. Finally, muscle fibers isolated from HMB-treated mdx mice showed improved mitochondrial efficiency that was associated with increased maximal respiration, spare respiratory capacity, and ATP synthesis. This study is the first to show HMB-induced improvements on in vitro and in vivo measures of mdx skeletal muscle force production that are coupled with improved mitochondrial function, suggesting that HMB may be a viable treatment option for DMD.NEW & NOTEWORTHY This is the first study to examine the effect of HMB in 3-wk-old mdx mice undergoing extensive muscle damage and regeneration both in vivo and in vitro. HMB treatment increased voluntary grip strength and holding impulse, while elevating force production of isolated mdx EDL muscles, which were associated with improved muscle mass, muscle fiber size, and succinate dehydrogenase activity. Finally, these improvements coincided with increased markers of mTORC1 signalling, mitochondrial respiration, and ATP production.

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related deaths, and its incidence is expected to rise. Skeletal muscle wasting (SMW) is a debilitating comorbidity of PDAC with unknown etiology. Previously, our lab demonstrated that systemic increases in insulin-like growth factor-binding protein-3 (IGFBP-3) are associated with SMW and pathologic myocellular lipid accumulation in an orthotopic murine model of PDAC [Ptf1a^tm1-cre/+;Kras^tm4Tyj;Muc1^-/- (KCKO)]. Here we show that PDAC tumor cells secrete high levels of IGFBP-3 and that genetic ablation of IGFBP-3 (IGFBP-3^-/-) in the KCKO and Ptf1a^{tm1(cre)Cvw/WT};Kras^tm4Tyj/WT;Trp53^{tm5Tyj/tm5Tyj} (KP2) orthotopic models of PDAC increases survival by at least 30 days in both models without affecting tumor progression. Mice with IGFBP-3^-/- tumors lost 10- and 3-fold less appendicular lean mass, and experienced a five- and sixfold decrease in myocellular lipid accumulation versus mice with parental KCKO and KP2 tumors, respectively, at failure to thrive endpoints. Gene expression studies demonstrated increases in the ubiquitin-proteasome pathway (fbxo32 and trim32), autophagy (ULK1 and LC3bII), and transforming growth factor-β receptor (TGF-βR) signaling (tgfβr1 and FoxO1) in skeletal muscle of mice inoculated with parental PDAC tumors, which was absent in mice with IGFBP-3^-/- tumors. In vitro studies confirmed a role for IGFBP-3 in stimulating TGF-β receptors and regulating SMAD3 nuclear localization. Moreover, IGFBP-3 deletion in tumor cells and small molecule inhibition of TGF-βR1/2 attenuated myotube wasting. Collectively, these results suggest that PDAC-derived IGFBP-3 promotes SMW via noncanonical binding of TGF-βRs, warranting formal investigation of IGFBP-3 as a potential therapeutic target for PDAC-related SMW through a novel pathway.NEW & NOTEWORTHY The mechanism underlying PDAC-associated SMW is not well understood but has been connected to increases in systemic IGFBP-3 to supraphysiologic levels, resulting in dysregulated protein synthesis and catabolism signaling. Here, we show that genetic deletion of IGFBP-3 in orthotopic PDAC tumors significantly improves survival and muscle phenotypes in mice. Molecular studies suggest the role for noncanonical IGFBP-3 signaling through TGF-β receptors. Thus, IGFBP-3 may be a therapeutic target in the treatment of PDAC-related SMW.

Sympathetic nerves are key regulators of cardiac performance, yet their micro-anatomical relationship with the coronary microcirculation remains incompletely defined. Here, we identify a previously underappreciated cardiac NeuroVascular Unit (NVU), in which sympathetic fibers frequently lie in close anatomical apposition to capillary endothelial cells. Using confocal and ultrastructural imaging in mouse and human hearts, we demonstrate that a substantial fraction of tyrosine hydroxylase-positive processes aligns with the capillary network, suggesting a structural framework for local neurovascular communication. Cardiac aging was associated with fragmentation and rarefaction of sympathetic fibers, accompanied by cardiomyocyte atrophy and capillary remodeling characterized by increased vessel density and reduced caliber. Pharmacological sympathectomy in young mice reproduced these changes, establishing a causal link between sympathetic integrity, cardiomyocyte trophism, and microvascular organization. Control experiments excluded direct vascular toxicity of 6-hydroxydopamine, and combined adrenalectomy-sympathectomy confirmed that these effects were independent of circulating catecholamines. Analysis of transplanted human hearts - an established clinical model of abrupt cardiac denervation - revealed an early-established and persistent reduction in capillary diameter compared with controls, mirroring the phenotype observed in mice. Together, these findings define the cardiac NVU as a structural neurovascular interface integrating sympathetic, endothelial, and myocyte compartments, with potential functional implications. Recognition of this neurovascular architecture revises current paradigms of cardiac autonomic regulation and suggests new avenues for targeting microvascular-neuronal apposition in cardiac aging and transplantation.

The extracellular matrix (ECM) protease Adamts5 and its ECM substrates are critical regulators of inflammation and fibrosis; whether Adamts5 also regulates muscle regeneration is not known. Right tibialis anterior (TA) muscles from adult Adamts5^--/- mice or wild type mice were injected with glycerol to induce injury. In uninjured muscles and at 7- and 14-days post injury, TA contractile function was determined in situ, followed by an assessment of pathology using histology and immunohistochemistry. Immunoblotting was performed for the versikine fragment which is generated when Adamts5 cleaves its substrate versican. Versikine protein, which correlates with Adamts5 proteolytic activity, was lower in uninjured and injured TA muscles from Adamts5^-/- mice versus wild type mice. In uninjured TA muscles, Adamts5 deletion of the catalytic and ancillary domains decreased the absolute (P_o) and normalized to muscle size (sP_o) force output, with no significant effect on muscle mass and myofiber size. Adamts5 deletion compromised regeneration with greater impairment evident at the later timepoint. Force output (P_o and sP_o) was lower in Adamts5^-/- mice at 7- and 14-days post injury. TA mass and myofiber size were only decreased at 14-days post injury, while embryonic myosin heavy chain expression did not significantly differ between genotypes. Degeneration, mononuclear infiltrates, and ECM deposition including fibronectin protein were greater in injured TA muscles from Adamts5^-/- mice. Resolution of inflammation was also delayed in Adamts5^-/- mice, with more infiltrating macrophages observed at 14-days post injury. In conclusion, Adamts5 regulates the balance between muscle regeneration, fibrosis, and inflammation following glycerol injury.

Endothelial dysfunction occurs early in the pathogenesis of type 2 diabetes (T2D)- associated cardiovascular disease. Previous work has revealed that endothelial glycocalyx mechanosensing structures are degraded in T2D, likely contributing to impaired shear stress mechanotransduction and consequent blunted vasodilation. Evidence from proteomic analysis suggests that glypican-1, a well-known mechanosensor, is a substrate of the proinflammatory enzyme ADAM17. A critical step in ADAM17 activation is externalization of phosphatidylserine (PS) to the outer leaflet of the plasmalemma, which can be enacted by the Ca ²⁺-activated phospholipid scramblase ANO6. However, whether ANO6-mediated activation of ADAM17 leads to glypican-1 shedding in endothelial cells remains unknown. Also unknown are the mechanisms by which this pathway becomes overactive in T2D. We recently reported that the activity of neuraminidase, a soluble enzyme that cleaves sialic acid, is elevated in the plasma of individuals with T2D and that this occurs in concert with increased ADAM17 activity. Here, in an extended cohort of males and females with T2D, we report that this association is also coupled with reduced flow-mediated dilation (FMD). Furthermore, we report that subjecting endothelial cells to neuraminidase increases intracellular Ca ²⁺, which provokes ANO6-mediated PS externalization, leading to ADAM17-dependent reductions of glypican-1. In isolated arteries, intraluminal exposure to neuraminidase impairs FMD, which can be prevented by ANO6 or ADAM17 inhibition. Lastly, isolated arteries from endothelial cell-specific ADAM17 knockout mice fed a Western diet exhibit greater FMD than genetic controls. Collectively, this work identifies the neuraminidase-ANO6-ADAM17 axis as a potential novel mechanism underlying impaired endothelial shear stress mechanotransduction in T2D.

Prostate cancer progression and metastasis is a complex step that is controlled by various molecular and cellular mechanisms. Here, the process of osteomimicry has a vital role in the context of bone metastasis. Osteomimicry phenomenon refers to the ability of cancer cells to acquire bone-like properties, thus enabling them to adapt to and survive in their bone microenvironment. This phenomenon promotes cancer cell and bone microenvironment interactions and contributes directly to tumor survival, growth, and the development of bone metastatic lesions. In this review we discuss the role of different osteomimicry factors in prostate cancer progression and metastasis, highlighting their involvement in each stage of the metastatic cascade. Key factors involved in osteomimicry - such as bone matrix proteins, signaling pathways, and transcriptional regulators - play important roles throughout the various stages of cancer progression. These include the initial development of the tumor, its local invasion into surrounding tissues, entry into the bloodstream (intravasation), spread to other more distant areas (extravasation), and ultimately, colonization and growth in the bone. Gaining a better understanding of how these factors are regulated, interact, and function can shed light on new treatment strategies aimed at targeting osteomimicry to slow down or prevent the progression of prostate cancer and its spread to the bones.