Mesenchymal stromal cells (MSCs) have shown great promise in experimental traumatic brain injury (TBI), conferring protection mainly through the release of bioactive factors (secretome). In vitro models, mimicking the in vivo condition in a simpler but representative environment may be fundamental to investigate secretome mechanisms of action. Nonetheless, TBI research lacks relevant 3D in vitro models that can serve as a bridging approach between cell culture and in vivo experiments. The aim of this study was to develop an in vitro model of brain contusion on organotypic brain slices and to test the efficacy of MSC-secretome obtained from human umbilical cord perivascular tissues.
Organotypic brain slices from the prefrontal cortex of newborn mice were subjected to controlled biomechanical impact (CCI) by an electromagnetic device. Compared to the control (CTRL) condition, CCI slices showed a time-dependent increase in cell death evaluated by lactate dehydrogenase (LDH) and propidium iodide incorporation (PI) assays. More in-depth, regional specific analysis of PI showed the highest values at the lesion core, and a gradual decrease moving away from it. An overtime increase in neuronal damage was revealed by neurofilament light (NFL) biomarker released in culture medium. Gene expression analysis 48h after injury showed significant downregulation of neuronal (MAP2) and upregulation of pan glial markers (CD11b and GFAP) after CCI.
MSC-secretome delivered 1h post-injury reduced PI values at the lesion core of CCI slices and reduced neuronal damage, as revealed by the reduction of NFL release in the medium and by a rescue effect of CCI-induced downregulation of both mRNA MAP-2 and BDNF.
In conclusion, we established a reliable in vitro model that recapitulates key features of TBI pathology and provided evidence for the protective efficacy of MSC-secretome.