PhD Student Ankara University Ankara, Ankara, Turkey
Abstract: Spinal muscular atrophy (SMA) is a genetic disorder characterized by motor neuron degeneration, leading to muscle weakness and atrophy due to SMN protein deficiency in infants. The discovery of the genetic cause of SMA has led to the development of several treatment options; however, thus far there is no complete cure for SMA. Since the in vitro evaluation of human spinal motor neurons is not possible without the use of postmortem tissue, induced pluripotent stem cells (iPSCs) have emerged as a promising avenue to understand the pathophysiology of SMA and represent a radical tool in the quest for effective SMA treatments. In this study, we aimed to generate iPSCs from PBMCs of SMA patients and healthy controls using the Sendai viral vector system, differentiate these iPSCs into motor neurons, and establish a disease model to determine the effect and participation of ion channels and metabolic processes. During differentiation, electrophysiological activities were evaluated via patch clamp, and motor neuron and ion channel-specific gene expressions were examined via qPCR in SMA and control motor neurons. We have found that SMA motor neurons were less developed and smaller in size and axonal length, and ChAT, HB9, and synaptophysin gene expressions were significantly reduced compared to control motor neurons, indicating impaired maturation and synaptic connectivity. Our patch clamp and qPCR data showed a lack of voltage-gated sodium current and reduced voltage-gated potassium current in SMA patients. Voltage-gated calcium, calcium-activated potassium, and hyperpolarization-activated cyclic nucleotide-gated channels also showed reduced activity in SMA. Additionally, in SMA iPSCs, ROS levels were measured to be three times higher than in control iPSCs, indicating mitochondrial dysfunction and overall metabolic complications. Similarly, SMA motor neurons displayed elevated hydrogen peroxide levels. In summary, we were able to generate the first-ever iPSCs from SMA patients in Turkey and to report the molecular, biochemical, electrophysiological, and metabolic differences between SMA and control motor neurons. iPSCs’ ability to model SMA and facilitate the development of targeted therapies underscores their significance in advancing our understanding and management of this debilitating condition.
Funding Source: This work was funded by the Scientific and Technological Research Institution of Turkey (TUBITAK) 1004 project.
