Biology subjects

Morton, A. B.

Publications and source records attributed to Morton, A. B..

4 recordsLinked to original sources

bioRxiv2025

Skeletal Muscle Regeneration is Accelerated Following Injection of Time Release Ion Matrix in Injured Mice

IntroductionSkeletal muscle injury remains a significant cause of disability with limited treatment options. Here we report accelerated skeletal muscle regeneration following injection of an inorganic biomaterial alone, cobalt oxide time-release ion matrix (CoO-TRIM). MethodsThe tibialis anterior (TA) muscle of adult C57BL/6J mice was injured with 70 {micro}L of barium chloride, with uninjured limbs serving as contralateral controls. Following the acute inflammatory phase (3 days post injury, dpi), mice were randomly separated into three groups: untreated controls, 70 {micro}l sterile saline injection alone (vehicle control) or 70 {micro}l CoO-TRIM (5 {micro}g/{micro}l) and evaluated at 8- and 14 dpi. Results14 dpi, injured TA muscles receiving a single injection of CoO-TRIM exhibited greater recovery of maximal force production (means {+/-} SEM: Healthy; TRIM, 31.8 {+/-} 0.6 N/cm3; Untreated, 31.7 {+/-} 0.8 N/cm3; Saline, 31.6 {+/-} 0.8 N/cm3, Injured; TRIM, 31.8 {+/-} 0.8 N/cm3; Untreated, 26.1 {+/-} 1.1 N/cm3, P= <0.01 vs. TRIM Injured; Saline, 26.0 {+/-} 1.3 N/cm3, P= <0.01 vs. TRIM Injured), increased fiber size (Healthy; TRIM, 2466 {+/-} 128 {micro}m2 vs. Untreated, 2351 {+/-} 131 {micro}m2; vs. Saline, 2460 {+/-} 129 {micro}m2, Injured; TRIM, 2179 {+/-} 63 {micro}m2 vs. Untreated, 1525 {+/-} 52 {micro}m2, P= <0.01; vs. Saline, 1470 {+/-} 99 {micro}m2, P= <0.01), and accelerated muscle regeneration (TRIM, 32.7 {+/-} 6.8 eMyHC+ fibers/mm2 vs. Untreated, 91.8 {+/-} 11.8 eMyHC+ fibers/mm2, P= <0.01; vs. Saline, 94.0 {+/-} 9.6 eMyHC+ fibers/mm2, P= <0.01). Vascular endothelial growth factor was elevated 14 dpi (TRIM, 17.3 {+/-} 2.9 pg/mg vs. Untreated, 10.3 {+/-} 1.1 pg/mg, P= 0.04; Saline, 5.5 {+/-} 1.2 pg/mg, P= <0.01), with increased muscle microvascular area (TRIM, 119.9 {+/-} 4.2 {micro}m2/fiber vs. Untreated, 94.9 {+/-} 4.2 {micro}m2/fiber, P= <0.01; Saline, 91.3 {+/-} 4.0 {micro}m2/fiber, P= <0.01) following CoO-TRIM treatment. There were early increases in inflammatory responses 8 dpi in injured TA muscles receiving CoO-TRIM (IL-6; TRIM, 29.1 {+/-} 8.2 pg/ml vs. Untreated, 12.4 {+/-} 1.5 pg/ml, P= 0.02; Saline, 11.7 {+/-} 0.8 pg/mg, P= 0.01), with early resolution of degenerative inflammatory cytokines and elevated regenerative cytokines 14 dpi (IL-10; SEM: TRIM, 2.4 {+/-} 0.1 pg/ml vs. Untreated, 2.1 {+/-} 0.1 pg/ml, P= 0.25; Saline, 2.0 {+/-} 0.1 pg/ml, P= 0.04). No differences were observed in healthy contralateral limbs following treatment with CoO-TRIM compared to healthy control mice at 8- and 14 dpi. DiscussionThis work suggests CoO-TRIM enhances muscle regeneration following injury, possibly through an immune cell-mediated mechanism. Statement of Clinical RelevanceThis is the first report of an injected, inorganic biomaterial alone to accelerate regeneration of injured skeletal muscle with no observed effects on healthy muscle. These findings suggest enhancements to skeletal muscle regeneration following CoO-TRIM treatment may be immune cell mediated with an increased local inflammatory response and subsequent improvements to muscle microvasculature and myogenic regulatory factors.

physiology↗

bioRxiv2025

Characterization of Gait Kinematics and Muscle Function in Becker Muscular Dystrophy Pigs: a pilot study

Vertebrate animal models of Becker muscular dystrophy (BMD) have been developed. Here, we characterized the gait kinematics and muscle function of a naturally occurring BMD pig model of dystrophin insufficiency. BMD pigs tended to have alterations in hip range of motion (ROM): hip (67%, 95% CI -0.64 to 14.12 degrees). While parameters were unaltered in extensor muscles, the dystrophin levels in flexor tibiotarsal joint muscles correlated with fatigue index as well as reduced isometric force (48%, 95% CI -1.86 to -0.61 N-m), and a 33% increase in fatigue index (95% CI -36.25 to 96.71 percent); the extensor muscles had no observable reductions in muscle force, with a 48% increase in fatigue index (95% CI -232.6 to 472.6 percent). Histological analysis of muscle biopsies supported a BMD phenotype in the flexor muscles of BMD pigs, with a 75% (95% CI -55.14 to -15.66 percent) decrease in large and a 43% (95% CI 17.74 to 57.38 percent) increase in small muscle fiber cross-sectional area. Dystrophin protein abundance was 28% less in flexor muscles from BMD pigs (95% CI -49.63 to 11.41 arbitrary units). Together, our model may serve as a clinically relevant model of BMD to assess safety and efficacy of therapeutics.

pathology↗

bioRxiv2025

Methods for In situ Quantification of Mitochondrial Morphology In Muscle and Terminal Schwann Cells of Mice

Mitochondrial dysfunction is well described in many chronic illnesses including musculoskeletal, neurodegenerative, and cardiovascular diseases. Mitochondrial network morphology has been implicated as a biomarker of disease, correlating increased mitochondrial fragmentation to impaired cellular function. While advancements in imaging techniques further our understanding of mitochondrial dynamics in live cells, easily accessible approaches for accurate quantification of in situ mitochondrial networks in low abundance tissues are lacking. The purpose of this study was to validate a proof-of-concept method capable of quantifying 3D mitochondrial network morphology in whole mount skeletal muscle and then applying it to mitochondrial morphology analysis in cell types otherwise difficult to image within their native environment, terminal Schwann cells (tSCs). Herein, we report that mitochondrial networks were fragmented in dystrophic mouse muscle compared to healthy controls, as observed by others, and correlated with muscle pathology as expected. Using S100{beta} reporter mice to identify Schwann cells, we labeled tSC mitochondrial networks in vivo prior to rapid imaging in situ with high-resolution confocal microscopy. Moreover, these methods offer a comprehensive and novel approach enabling the quantification of mitochondria network morphology across multiple cell types (like muscle fibers and tSCs) using standard microscopy available in university core facilities. SummaryLocal injections of mitochondrial dye are used to label terminal Schwann cells for confocal microscopy imaging after proof of concept was demonstrated in skeletal muscle tissue from mice with healthy or diseased muscle.

cell biology↗

bioRxiv2022

Angiogenesis precedes myogenesis during regenerationfollowing biopsy injury in skeletal muscle

BackgroundAcute injury to skeletal muscle damages myofibers and fragments capillaries, impairing contractile function and local perfusion. Myofibers and microvessels regenerate from satellite cells and from surviving microvessel fragments, respectively, to restore intact muscle. However, it is unknown whether myofiber regeneration and microvascular regeneration reflect interdependent processes or may proceed sequentially. MethodsTo investigate the temporal relationship between myogenesis and angiogenesis during regeneration, a punch biopsy (diameter, 2 mm) was performed through the center of the gluteus maximus (GM) muscle. Complete removal of all tissue components created a void into which regeneration was evaluated through 21 days post injury (dpi). Confocal imaging and histological analyses of whole-mount GM preparations and GM cross sections assessed the growth of microvessels and myofibers into the wound. Regeneration of perfused microvessels was evaluated in vivo by injecting fluorescent dextran into the circulation during intravital imaging. ResultsA provisional matrix filled with PDGFR+ and CD45+ cells spanned the wound within 1 dpi. Regenerating microvessels advanced into the matrix by 7 dpi. At 10 dpi, sprouting and intussusceptive angiogenesis produced disorganized microvascular networks and spanned the wound with perfusion by 14 dpi. In striking contrast, the wound remained devoid of myofibers at 7 and 10 dpi. Myogenesis into the wound began by 14 dpi with nascent myofibers traversing the wound by 21 dpi. Regenerating myofibers and microvessels were less well organized than in the surrounding (uninjured) muscle. ConclusionsAngiogenesis precedes myogenesis following punch biopsy injury of adult skeletal muscle. Regenerating microvessels encompass the wound and become perfused with blood prior to colocalization with regenerating myofibers. These findings infer that a microvascular supply supports the metabolic demands of regenerating skeletal muscle. Finding that regenerated microvascular networks and myofibers are disorganized within the biopsy site suggests that loss of guidance cues upon complete tissue removal impairs re-establishment of canonical skeletal muscle structure.

physiology↗