Search

Spinal cord injury (SCI), a debilitating medical condition that can cause irreversible loss of neurons and permanent paralysis, currently has no cure. However, regenerative medicine may offer a promising treatment. Given that numerous regenerative strategies aim to deliver cells and materials in the form of tissue-engineered therapies, understanding and characterising the mechanical properties of the spinal cord tissue is very important. In this study, we have systematically characterised the spatiotemporal changes in elastic stiffness (elastic modulus, Pa) and viscosity (drop in peak force, %) of injured rat thoracic spinal cord tissues at distinct time points after crush injury using the indentation technique. Our results demonstrate that in comparison with uninjured spinal cord tissue, the injured tissues exhibited lower stiffness (median 3281 Pa versus 9632 Pa; P 0.001) but demonstrated elevated viscosity (median 80% versus 57%; P 0.001) at 3 days postinjury. Between 4 and 6 weeks after SCI, the overall viscoelastic properties of injured tissues returned to baseline values. At 12 weeks after SCI, in comparison with uninjured tissue, the injured spinal cord tissues displayed a significant increase in both elasticity (median 13698 Pa versus 9920 Pa; P 0.001) and viscosity (median 64% versus 58%; P 0.001). This work constitutes the first quantitative mapping of spatiotemporal changes in spinal cord tissue elasticity and viscosity in injured rats, providing a mechanical basis of the tissue for future studies on the development of biomaterials for SCI repair. STATEMENT OF SIGNIFICANCE: Spinal cord injury (SCI) is a devastating disease often leading to permanent paralysis. While enormous progress in understanding the molecular pathomechanisms of SCI has been made, the mechanical properties of injured spinal cord tissue have received considerably less attention. This study provides systematic characterization of the biomechanical evolution of rat spinal cord tissue after SCI using a microindentation test method. We find spinal cord tissue behaves significantly softer but more viscous immediately postinjury. As time passes, the lesion site gradually returns to baseline values and then displays pronounced increased viscoelastic properties. As host tissue mechanical properties are a crucial consideration for any biomaterial implanted into central nervous system, our results may have important implications for further studies of SCI repair.

Spinal cord injury (SCI) is a global problem that brings a heavy burden to both patients and society. Recent investigations indicated degenerative disease is taking an increasing part in SCI with the growth of the aging population. However, little insight has been gained about the effect of cervical degenerative disease on the spinal cord during dynamic activities. In this work, a dynamic fluid-structure interaction model was developed and validated to investigate the effect of anterior and posterior encroachment caused by degenerative disease on the spinal cord during normal extension and flexion. Maximum von-Mises stress and maximum principal strain were observed at the end of extension and flexion. The abnormal stress distribution caused by degenerative factors was concentrated in the descending tracts of the spinal cord. Our finding indicates that the excessive motion of the cervical spine could potentially exacerbate spinal cord injury and enlarge injury areas. Stress and strain remained low compared to extension during moderate flexion. This suggests that patients with cervical degenerative disease should avoid frequent or excessive flexion and extension which could result in motor function impairment, whereas moderate flexion is safe. Besides, encroachment caused by degenerative factors that are not significant in static imaging could also cause cord compression during normal activities.

This study aims to establish and validate a poroelastic L4-L5 finite element model to evaluate the effect of different sitting postures and their durations on the mechanical responses of the disc. During the sustained loading conditions, the height loss, fluid loss and von-Mises stress gradually increased, but the intradiscal pressure decreased. The varying rates of aforementioned parameters were more significant at the initial loading stage and less so at the end. The predicted values in the flexed sitting posture were significantly greater than other postures. The extended sitting posture caused an obvious von-Mises stress concentration in the posterior region of the inter-lamellar matrix. From the biomechanical perspective, prolonged sitting may pose a high risk of lumbar disc degeneration, and therefore adjusting the posture properly in the early stage of sitting time may be useful to mitigate that. Additionally, upright sitting is a safer posture, while flexed sitting posture is more harmful.

Aim: To explore the effectiveness of home-based exercise programs with e-devices (HEPEs) on falls among community-dwelling older adults. Methods: Twelve randomized controlled trials were included in the meta-analysis considering four fall-related outcomes. Results: HEPEs significantly reduced the rate of falls (risk ratio: 0.82; 95% CI: 0.72–0.95; p = 0.006) and improved lower extremity strength (mean difference: -0.94; 95% CI: -1.71 to -0.47; p < 0.001). There was a significant improvement favoring HEPEs on balance if the participants were aged >75 years (mean difference: -0.55; 95% CI: -1.05 to -0.05; p = 0.03), or the intervention duration was at least 16 weeks (mean difference: -0.81; 95% CI: -1.58 to -0.05; p = 0.04). Conclusion: HEPEs demonstrated an overall positive effect on falls among community-dwelling older adults.

Objective Preexisting severe cervical spinal cord compression is a significant risk factor in cervical hyperextension injury, and the neurological function may deteriorate after a slight force to the forehead. There are few biomechanical studies regarding the influence of pathological factors in hyperextension loading condition. The aim of this study is to analyze the effects of preexisting different types of cervical disc herniation and different degrees of compression on the spinal cord in cervical hyperextension. Method A 3D finite element (FE) model of cervical spinal cord was modeled. Local type with median herniation, local type with lateral herniation, diffuse type with median herniation, and diffuse type with lateral herniation were simulated in neutral and extention positions. The compressions which were equivalent to 10%, 20%, 30%, and 40% of the sagittal diameter of the spinal cord were modeled. Results The results of normal FE model were consistent with those of previous studies. The maximum von Mises stresses appeared in the pia mater for all 32 loading conditions. The maximum von Mises stresses in extension position were much higher than in neutral position. In most cases, the maximum von Mises stresses in diffuse type were higher than in local type. Conclusion Cervical spinal cord with preexisting disc herniation is more likely to be compressed in hyperextension situation than in neutral position. Diffuse type with median herniation may cause more severe compression with higher von Mises stresses concentrated at the anterior horn and the peripheral white matter, resulting in acute central cord syndrome from biomechanical point of view.

This study was designed to investigate the inhibitory effect of supernatant from co-culture of human embryonic stem cells and tumor MDA-MB-231 cells on the breast cancer. The direct co-culture system of human embryonic stem cells H9 and breast cancer MDA-MB-231 cells was established, and the supernatant was tested in the inhibition of MDA-MB-231 cells. The inhibitory effects were examined in tumor cell morphology using microscope, cell proliferation with MTT assay, and cell apoptosis using the Hoechst staining and flow cytometry. Transwell assay was used to detect the migration and invasion of tumor cells. The results suggest that the supernatant significantly inhibited the proliferation, invasion and migration, and promoted cell apoptosis of MDA-MB-231 cells. However, the supernatant of H9 cells alone had little effect on MDA-MB-231 cells. Therefore, we conclude that the supernatant of co-culture cells had an inhibitory effect on tumor cells in vitro.