A. N. Belozersky Research Institute of Physico-Chemical Biology MSU
<h4>Background</h4>Mesenchymal stem/stromal cells (MSCs) are the focus of increasing research as a potential therapeutic agent for a range of nervous system diseases, due to their unique capacity for self-renewal and differentiation. The subsequent tracking of cells post-transplantation into the organism is of pivotal significance, as it elucidates their fate, distribution, and enables the timely monitoring of any adverse effects. In the context of cell monitoring, the utilization of a non-toxic label that exhibits long-term stability is of paramount importance.<h4>Methods</h4>A human immortalized MSCs cell line was engineered to express a green fluorescent protein (GFP) and bacterial nanocompartments (high-molecular-weight icosahedral capsid-like protein complexes) via lentiviral transduction. The obtained cells were characterized by inductively coupled plasma mass spectrometry (ICP-MS) and Perls staining as well as using the nonlinear magnetization method, confocal microscopy and flow cytometry. An animal study was conducted in Sprague-Dawley rats.<h4>Results</h4>In this study, an immortalized human MSCs cell line with stable expression of a novel magnetic resonance (MR) reporter label was established for the first time. GFP was genetically produced for utilization as an optical tag. A nanocompartment of the bacterium Quasibacillus thermotolerans (Qt) was used as a carrier of the magnetic label. The Qt nanocompartment consists of a shell and a ferroxidase cargo protein. Ferroxidase provides the biomineralization of iron ions within the nanocompartment shell. As a result, ferric oxide nanoparticles are formed inside the encapsulin nanocompartments, which have T2-contrast properties and serve as genetically encoded labels for magnetic resonance imaging (MRI) and for quantification by the nonlinear magnetization method.<h4>Conclusions</h4>The experimental results indicate that the use of two complementary labels allows for the multimodal visualization of the derived cells post-transplantation into the rat brain striatum, which is promising for monitoring MSCs-based therapy.