IBEC PhD Discussions
by Yolanda Castillo and Marc Molina
Assessment of trunk function in patients with spinal cord injury using electromyography and smartphone accelerometry
Yolanda Castillo, Biomedical Signal Processing and Interpretation
Spinal cord injury (SCI) causes motor and sensory impairment below the level of the injury, but also many other health problems. A common consequence of SCI is the lack of control over trunk muscles, leading to deficits in postural control and balance while sitting. Since trunk stability is essential to maintain upright posture and support functional movements, impaired trunk function constitutes a major cause of motor disability in SCI patients, limiting their independence and quality of life. However, trunk stability is rarely examined in studies of mobility after SCI, and one of the reasons is the lack of quantitative measures for assessing trunk function. Here we propose to record and analyze electromyographic (EMG) and smartphone accelerometric data to extract quantitative measures for the evaluation of trunk function. Our aims were: 1) to characterize muscle activity and movement patterns of trunk flexion during a reaching task in healthy subjects and patients with SCI, 2) to compare the impact of cervical and thoracic injuries in trunk function, and 3) to investigate the potentially destabilizing effects of a startling acoustic stimulus in this task. For these purposes, during a reaching movement requiring trunk flexion, we recorded the EMG activity of 8 trunk, neck, and shoulder muscles and smartphone accelerometer data from individuals with cervical SCI, thoracic SCI, and healthy control subjects. We analyzed these signals and extracted different features, including the response time until pressing a target button, EMG onset latencies and amplitudes, and trunk tilt, lateral deviation, and other movement features from accelerometry. The proposed outcome measures revealed deficits in postural control and compensatory strategies employed by SCI patients, including delayed responses and higher lateral deviations, which might have important consequences for rehabilitation. The combination of EMG and smartphone accelerometer data can help to develop more suitable methods for the assessment of trunk function in individuals with SCI, thus improving the follow-up and management of these patients.
Development of a model of “macro” substrates for the analysis of 3D chromatin structure and transcriptional profiling
Marc Molina, Cellular and Molecular Mechanobiology
Mechanically-induced changes in the genome are increasingly recognized as major drivers of cell and tissue function. However, current and past studies on this topic in vitro have often been limited by the sample size required for these genomic analyses. Here we describe the development of a polyacrylamide gel (pAAg) substrate with larger area than gels previously generated in labs worldwide. These substrates display the same tunable stiffness as their smaller counterparts and are particularly suitable to accommodate large numbers of cells. We tested the substrates to assess the effect that changes in rigidity have in the cell’s genome, both at the level of chromatin organization and transcriptional regulation. For this, two different rigidities were used (soft vs stiff) with three conditions which included: i) a control group, ii) a transiently expressing mutant of RanQ69L that prevents all nucleocytoplasmic transport and iii) a transiently expressing mutant of NES1-KASH that prevents force transmission to the nucleus. Our preliminary results suggest that cells seeded on pAAg substrates of different rigidities display differences in chromatin structure and gene expression, but more data will be necessary to further support these results. Ultimately, the aim of our project is to understand down the road how changes in rigidity affect: i) the 3D structure and interaction map of chromatin and ii) the activated or repressed transcriptional programs in soft and stiff substrates. Overall, this new model will help us to characterize how the genome is affected by rigidity both at the structural and transcriptional levels. More broadly, we expect the potential findings of this work to help the community detailing the effect of changes in tissue stiffness in the genome spatial organization.
This PhD Discussion will be hybrid. Yolanda Castillo will be doing her presentation online and Marc from the Baobab room, located in tower I floor 11. To follow the session online, find here the link, we will be using the GoToMeeting app. If you wish to attend in person, the free spots will be assigned on a first come first served basis, the capacity of the room is for 30 people.