New Imaging Biomarkers for Muscular Diseases - Multispectral Optoacoustic Imaging in Spinal Muscular Atrophy

SMA is an autosomal-recessive disorder, characterized by progressive muscle weakness and atrophy with an incidence of 1/10,000. The condition is caused by a homozygous deletion or mutation in the survival motor neuron 1 (SMN1), resulting in reduced expression of the survival motor neuron (SMN) protein. This leads to the degeneration of motor neurons in the spinal cord and brain stem. A nearby related gene, survival motor neuron 2 (SMN2), could partially compensate the loss of SMN1. Individuals with a higher copy number of SMN2 do in general have a milder phenotype. New therapeutic approaches, e.g. nusinersen (spinraza©), an antisense oligonucleotide medication that modulates pre-messenger RNA splicing of the survival motor neuron 2 (SMN2) gene, are promising to help the formerly incurable children. However, most clinical trials lack primary outcomes other than clinical testing. At the moment there are no prospective, quantitative biomarkers available to detect muscle atrophy at an early age, and to follow up disease progression. As a new imaging modality, optoacoustic imaging (OAI) combines benefits of optical (high contrast) and acoustic (high resolution) imaging. Multispectral optoacoustic tomography (MSOT) is therefore capable of visualizing the distribution of endogenous absorbers by initiating laser-induced thermoelastic expansion and detection of resulting pressure waves. This imaging technique enables the label-free detection and quantification of different endogenous chromophores, such as melanin, hemoglobin, deoxyhemoglobin and lipids. Previously, it was demonstrated that MSOT is capable to monitor disease severity in Crohn's disease by detecting different signal levels of hemoglobin as markers of intestinal inflammatory activity. In this study we want to refine the capability of MSOT to characterize muscle tissue and to determine a non-invasive, quantitative biomarker for the disease assessment in SMA patients from birth using MSOT.