Rheological properties of skeletal muscles in a Duchenne muscular dystrophy murine model before and after autologous cell therapy

The influence of cooling on biomechanical time since death estimations using ovine brain tissue

The significance of biomechanical analyses for forensic time since death estimations has recently been demonstrated. Previous biomechanical analyses successfully discriminated post-mortem brain tissue from tissue with a post-mortem interval of at least one day when held at 20 °C. However, the practical utility of such analyses beyond day one at 20 °C was limited. This study investigates the storage, loss, and complex shear modulus of various brain regions in sheep stored at 4 °C in 24-hour intervals over four days post-mortem using rheometry tests. The aim is to identify the critical biomechanical tissue property values to predict post-mortem time and assess the temperature sensitivity of the rheometry method by comparing results to recent findings at 20 °C. Thirty sheep brains were examined, including the frontal lobe, parietal lobe, anterior and posterior deep brain, superior colliculi, pons, medulla, and cerebellum. Rheometry tests were conducted, and receiver operator characteristic analyses were employed to establish cut-off values. At 4 °C storage, all investigated biomechanical properties of the examined brain regions remained stable for at least one day post-mortem. Using cerebellar samples stored at 4 °C, a post-mortem interval of at least two days could be determined with excellent diagnostic ability. Complex shear modulus values below 1435 Pa or storage modulus values below 1313 Pa allowed prediction of two or more days post-mortem. Comparisons between 4 °C and 20 °C revealed brain region-specific results. For instance, the complex shear moduli of the anterior deep brain at 4 °C were significantly higher on all individual testing days when compared to 20 °C. In contrast, the combined medulla and pons samples were similar on each day. Rheometry testing of brain tissue consistently stored at 4 °C since death proved valuable for forensic time since death estimations starting from two days after death.

Intersection of Immunity, Metabolism, and Muscle Regeneration in an Autoimmune-Prone MRL Mouse Model

Due to the limited capacity of mammals to regenerate complex tissues, researchers have worked to understand the mechanisms of tissue regeneration in organisms that maintain that capacity. One example is the MRL/MpJ mouse strain with unique regenerative capacity in ear pinnae that is absent from other strains, such as the common C57BL/6 strain. The MRL/MpJ mouse has also been associated with an autoimmune phenotype even in the absence of the mutant Fas gene described in its parent strain MRL/lpr. Due to these findings, the differences between the responses of MRL/MpJ versus C57BL/6 strain are evaluated in volumetric muscle injury and subsequent material implantation. One salient feature of the MRL/MpJ response to injury is robust adipogenesis within the muscle. This is associated with a decrease in M2-like polarization in response to biologically derived extracellular matrix scaffolds. In pro-fibrotic materials, such as polyethylene, there are fewer foreign body giant cells in the MRL/MpJ mice. As there are reports of both positive and negative influences of adipose tissue and adipogenesis on wound healing, this model can provide an important lens to investigate the interplay between stem cells, adipose tissue, and immune responses in trauma and material implantation.

Ectopic adipogenesis in response to injury and material implantation in an autoimmune mouse model

Due to the limited capacity of mammals to regenerate complex tissues, researchers have worked to understand the mechanisms of tissue regeneration in organisms that maintain that capacity. One example is the MRL/MpJ mouse strain with unique regenerative capacity in ear pinnae that is absent from other strains, such as the common C57BL/6 strain. The MRL/MpJ mouse has also been associated with an autoimmune phenotype even in the absence of the mutant Fas gene described in its parent strain MRL/lpr. Due to these findings, we evaluated the differences between the responses of MRL/MpJ versus C57BL/6 strain in traumatic muscle injury and subsequent material implantation. One salient feature of the MRL/MpJ response to injury was a robust adipogenesis within the muscle. This was associated with a decrease in M2-like polarization in response to biologically derived extracellular matrix scaffolds. In pro-fibrotic materials, such as polyethylene, there were fewer foreign body giant cells in the MRL/MpJ mice. As there are reports of both positive and negative influences of adipose tissue and adipogenesis on wound healing, this model could provide an important lens to investigate the interplay between stem cells, adipose tissue, and immune responses in trauma and materials implantation.

Anisotropy in ultrasound shear wave elastography: An add-on to muscles characterization

Ultrasound shear wave elastography was developed the past decade, bringing new stiffness biomarker in clinical practice. This biomarker reveals to be of primarily importance for the diagnosis of breast cancer or liver fibrosis. In muscle this biomarker become much more complex due to the nature of the muscle itself: an anisotropic medium. In this manuscript we depict the underlying theory of propagating waves in such anisotropic medium. Then we present the available methods that can consider and quantify this parameter. Advantages and drawbacks are discussed to open the way to imagine new methods that can free this biomarker in a daily clinical practice.