Biology subjects

Jaspers, R. T.

Publications and source records attributed to Jaspers, R. T..

6 recordsLinked to original sources

bioRxiv2023

Skeletal Muscle Phenotype-Specific Effects of ACVR1B and TGFBR1 Receptor Signalling on Muscle Transcriptome, Force generation and Metabolism

Transforming growth factor-{beta} (TGF-{beta}) signaling is associated with progressive skeletal muscle wasting and fibrosis, while double knockout of TGF-{beta} type I receptors Acvr1b and Tgfbr1 results in hypertrophy. Gaining insights in how myofibre-specific knockout of these receptors affects muscle transcriptome, strength and mitochondrial activity could aid in the development of therapeutic interventions to improve muscle function. Here, we show that 3 months of myofibre-specific knockout of both receptors (dKO) in mice induced a 1.6-fold increase in gastrocnemius medialis mass and a 1.3-fold increase in maximal force. Soleus muscle mass and maximal force both increased 1.2-fold in dKO mice. Muscle hypertrophy in dKO mice was accompanied by a proportional increase in succinate dehydrogenase enzyme activity. Single receptor knockout caused minor phenotypical alterations. Transcriptome analyses revealed that gastrocnemius medialis had 1811 and soleus had 295 differentially expressed genes, mainly related to muscle contraction, hypertrophy, filament organization and oxidative metabolism. Hgf and Sln genes were strongly upregulated in both muscles of dKO mice, while Sntb1 was downregulated. This in combination of transcriptional changes are associated with muscle hypertrophy and increased mitochondrial biosynthesis. Our study highlights that myofibre-specific interference with both TGF-{beta} type I receptors concurrently stimulates myofibre hypertrophy and mitochondrial activity.

physiology↗

bioRxiv2022

MicroRNA-155 regulates osteogenesis and bone mass phenotype via targeting S1PR1 gene

MicroRNA-155 (miR155) is overexpressed in various inflammatory diseases and cancer, in which bone resorption and osteolysis are frequently observed. However, the role of miR155 on osteogenesis and bone mass phenotype is still unknown. Here, we report a low bone mass phenotype in the long bone of miR155-Tg mice compared with control mice. In contrast, miR155-KO mice showed a high bone mass phenotype. miR155-KO mice showed robust bone regeneration in the ectopic and orthotopic model, but miR155-Tg mice showed compromised bone regeneration compared with the control mice. Similarly, the osteogenic differentiation potential of bone marrow stromal stem cells (BMSCs) from miR155-KO mice was robust and miR155-Tg was compromised compared with that of control mice. Moreover, miR155 knockdown in BMSCs from control mice showed higher osteogenic differentiation potential, supporting the results from miR155-KO mice. TargetScan analysis predicted S1PR1 as a target gene of miR155, which was further confirmed by luciferase assay and miR155 knockdown. S1PR1 overexpression in BMSCs robustly promoted osteogenic differentiation without affecting cell viability and proliferation. Thus, miR155 showed a catabolic effect on osteogenesis and bone mass phenotype via interaction with the S1PR1 gene, suggesting inhibition of miR155 as a potential strategy for bone regeneration and bone defect healing.

cell biology↗

bioRxiv2021

Lack of Tgfbr1 and Acvr1b synergistically stimulates myofibre hypertrophy and accelerates muscle regeneration

In skeletal muscle, transforming growth factor-{beta} (TGF-{beta}) family growth factors, TGF-{beta}1 and myostatin, are involved in atrophy and muscle wasting disorders. Simultaneous interference with their signalling pathways may improve muscle function, however little is known about their individual and combined receptor signalling. Here we show that inhibition of TGF-{beta} signalling by simultaneous muscle-specific knockout of TGF-{beta} type I receptors Tgfbr1 and Acvr1b simultaneously, induces substantial hypertrophy, while such effect does not occur by single receptor knockout. Hypertrophy is induced by increased phosphorylation of Akt and p70S6K and reduced E3 ligases expression, while myonuclear number remains unaltered. Combined knockout of both TGF-{beta} type I receptors increases the number of satellite cells, macrophages and improves regeneration post cardiotoxin-induced injury by stimulating myogenic differentiation. Extra cellular matrix gene expression is exclusively elevated in muscle with combined receptor knockout. Tgfbr1 and Acvr1b are synergistically involved in regulation of myofibre size, regeneration and collagen deposition.

physiology↗

bioRxiv2020

Myotube hypertrophy is associated with cancer-like metabolic reprogramming and limited by PHGDH

Muscle fiber size and oxidative metabolism are inversely related, suggesting that a glycolytic metabolism may offer a growth advantage in muscle fibers. However, the mechanisms underlying this advantage remains unknown. Nearly 100 years ago, Warburg reported that cancer cells take up more glucose to produce glycolytic intermediates for anabolic reactions such as amino acid-protein synthesis. The aim of this study was to test whether glycolysis contributes to anabolic signalling responses and hypertrophy in post-mitotic muscle cells. Skeletal muscle hypertrophy was induced in vitro by treating mouse C2C12 myotubes with IGF-1. 14C glucose was added to differentiation medium and radioactivity in isolated protein was measured. We exposed differentiated C2C12 and primary mouse myotubes, to 2-deoxyglucose (2DG) and PHGDH siRNA upon which we assessed myotube diameter and signaling pathways involved in the regulation of muscle fiber size. Here, we present evidence that, hypertrophying C2C12 myotubes undergo a cancer-like metabolic reprogramming. First, IGF-1-induced C2C12 myotube hypertrophy increases shunting of carbon from glucose into protein. Second, reduction of glycolysis through 2-deoxy-D-glucose (2DG) lowers C2C12 and primary myotube size 16-40%. Third, reducing the cancer metabolism-associated enzyme PHGDH decreases C2C12 and primary myotube size 25-52%, whereas PHGDH overexpression increases C2C12 myotube size {approx}20%. Fourth, the muscle hypertrophy-promoting kinase AKT regulates PHGDH expression. Together these results suggest that glycolysis is important for hypertrophying C2C12 myotubes by reprograming their metabolism similar to cancer cells.

molecular biology↗

bioRxiv2020

Glycine receptor subunit-β -deficiency in a mouse model of spasticity results in attenuated physical performance, growth and muscle strength

Spasticity is the most common neurological disorder associated with increased muscle contraction causing impaired movement and gait. The aim of this study was to characterize physical performance and skeletal muscle function and phenotype of mice with a hereditary spastic mutation (B6.Cg-Glrbspa/J). Motor function, gait and physical activity of juvenile and adult spastic mice and the morphological, histological and mechanical characteristics of their soleus (SO) and gastrocnemius medialis (GM) muscles were compared with their wild-type (WT) littermates. Spastic mice showed attenuated growth, impaired motor function and low physical activity. Gait of spastic mice was characterized by a typical hopping pattern. Spastic mice showed lower muscle forces, which were related to the smaller physiological cross-sectional area of spastic muscles. The muscle-tendon complex length-force relationship of adult GM was shifted towards shorter lengths, which was explained by attenuated longitudinal tibia growth. Spastic GM was more fatigue resistant than WT GM. This was largely explained by a higher mitochondrial content in muscle fibers and relatively higher percentage of slow type muscle fibers. Muscles of juvenile spastic mice showed similar differences compared to WT juvenile mice, but these were less pronounced than between adult mice. This study shows that in spastic mice, disturbed motor function and gait is likely the result hyperactivity of skeletal muscle and impaired skeletal muscle growth, which progress with age.

physiology↗

bioRxiv2020

Myofiber stretch induces tensile and shear deformation of muscle stem cells in their native niche

BackgroundMuscle stem cells (MuSCs) are requisite for skeletal muscle regeneration and homeostasis. Proper functioning of MuSCs, including activation, proliferation, and fate decision, is determined by an orchestrated series of events and communication between MuSCs and their niche consisting of the host myofiber and neighbouring cells. A multitude of biochemical stimuli are known to regulate fate and function of MuSCs. However, in addition to biochemical factors, it is conceivable that MuSCs residing between basal lamina and sarcolemma of myofibers are subjected to mechanical forces during muscle stretch-shortening cycles due to myofascial connections between MuSCs and myofibers. MuSCs have been shown to respond to mechanical forces in vitro but it remains to be proven whether physical forces are also exerted on MuSCs in their native niche and whether they contribute to the functioning and fate of MuSCs. MethodsMuSCs deformation in their native niche resulting from mechanical loading of ex vivo myofiber bundles were visualized utilizing mT/mG double-fluorescent Cre-reporter mouse and multiphoton microscopy. MuSCs were subjected to 1 hour pulsating fluid shear stress with a peak shear stress rate of 8.8 Pa/s. After treatment, nitric oxide and mRNA expression levels of genes involved in regulation of MuSC proliferation and differentiation were determined. ResultsEx vivo stretching of extensor digitorum longus and soleus myofiber bundles caused compression as well as tensile and shear deformation of MuSCs in their niche. MuSCs responded to pulsating fluid shear stress in vitro with increased nitric oxide production and an upward trend in iNOS mRNA levels, while nNOS expression was unaltered. Pulsating fluid shear stress enhanced gene expression of c-Fos, Cdk4, and IL-6, while expression of Wnt1, MyoD, Myog, Wnt5a, COX2, Rspo1, Vangl2, Wnt10b, and MGF remained unchanged. ConclusionsWe conclude that MuSCs in their native niche are subjected to force-induced deformations due to myofiber stretch-shortening. Moreover, MuSCs are mechanoresponsive as evident by pulsating fluid shear stress-mediated expression of factors by MuSCs known to promote proliferation.

cell biology↗