Effect of adipose stem cell exosomes on microvascular brain tissue of rats stimulated with interleukin 1 beta

Abstract

Multiple diseases cause neuroinflammatory processes of the brain. Traumatic brain injury and stroke, as examples, impose a distinguishable burden on the paitents’ life. Given the unassuring results and unavoidable side effects of anti-inflammatory and immunosuppressive drugs, there is a need for new treatments with fewer side effects. Mesenchymal stem cells (MSCs), with their immunemodulating properties, have various applications in regenerative medicine. Recently, therapeutic effects of MSCs have also been observed in the exosomes derived from these cells. The hindered tumorigenic properties, lower immune stimulation, reduced dosage response, and easier control have increased the popularity of exosomes. Material and methods: Inflammation in brain tissue was induced in rats using interleukin 1 beta (IL-1β) through intraperitoneal injection at a dose of 10 μg/kg for six consecutive days. The animals were divided into three groups: IL-1β, cells, and exosomes. Adipose-derived stem cells (ASCs) and exosomes obtained from these cells were injected into the rats’ venous circulation after isolation and identification via flow cytometry. Seven days of post-treatment, brain tissue samples from these animals, along with the control group, were collected. Tissue preparation was conducted using H&E and Evans blue staining, and immunohistochemistry with antibodies (CD68 and GFAP), and examined under a light microscope. Results: H&E staining results indicated that IL-1β caused moderate acute inflammation in cerebral tissue. Additionally, degenerated neurons, and compared to the control, shrincked cells with marginal nuclei were observed. Apparent holes were observed around neurons, and vascular hyperemia, and an increase in the number of pia matter layers were evident. Following systemic injection of adipose mesenchymal stem cells, especially their derived exosomes, neuronal degradation and the dimensions of the holes were diminished. Following exosome treatment, although the neuron morphology was not completely normal, no shrinkage was observed in them. Astrocytes, which normally have scant cytoplasm around the nucleus and represent acidophilic cells, became larger and their number increased as a result of IL-1β injection, but their number decreased more after the injection of exosome than after the injection of stem cells. In Evans Blue staining, we saw an increase in BBB permeability following IL-1β injection compared to the control group, which decreased after the injection of exosomes. In immunohistochemistry (IHC) staining, CD68 expression in microglial and endothelial cells of brain tissue was significantly higher in the IL-1β group than in the control groups. Although the exosome group demonstrated reduced CD68 expression compared to only IL-1β receiving group, the difference appeared to be not significant. Finally, in GFAP IHC, an increase in the size and number of astrocytes was seen following IL-1β injection. With the use of exosomes, astrocytes returned to a near-normal state, but stem cells were not effective in reducing astrocytosis. Furthermore, astrocytes in the cell group had more branched processes than in the exosome group.