Text

theses

During a stroke there is a reduction of oxygen, glucose, and other nutrients to the surrounding brain tissue causing neuronal death and astrocyte activation. Astrocytes are responsible for protecting the neurons during an injury. Part of the astrocyte activation is the release of various molecules as well as a change in morphology from a polygonal to a stellate state. Astrocyte’s morphological change can eventually lead to a glial scar preventing neurons from reforming connections. Obtaining an effective therapeutic to reduce the negative effects of astrocyte activation could greatly enhance recovery after a stroke. Mesenchymal stem cells (MSCs) have numerous anti-inflammatory and neuroprotective properties and with further development may be developed into an effective therapeutic. MSCs have been shown to regulate the immune response by reducing inflammatory molecules, such as TNF-α. However, there are several limitations with MSCs that must be addressed first, such as low viability, differentiation, and migration away from the injury site. To overcome these limitations the MSCs are encapsulated in alginate. The encapsulation still allows for soluble factors to interact with the MSCs and the host tissue while maintaining viability, keeping the MSCs undifferentiated, and allowing for localization to the injury site. In previous experiments, using encapsulated MSCs, attenuation of neuro-inflammation was achieved by PGE2 secreted by the MSCs. With the encapsulated MSCs, the MSCs can be used as a therapeutic. Stroke is one injury that has few treatments where MSCs could be beneficial. In vitro stroke is modeled as an oxygen glucose deprived system. Rat cerebral astrocytes are plated into a 24 well plate and exposed to 1% O2 and no glucose for 2.5, 5, or 10 hours. Astrocytes are then placed into normoxia conditions and recover for 24 hours. Increased expression of GFAP and elongation of astrocytes, measured by perimeter over area signify a change to a reactive state. There is a significant difference (p<0.05) in a perimeter to area ratio when astrocytes are exposed to OGD compared to control. Both monolayer and encapsulated MSC reduced the perimeter to area ratio of astrocytes exposed to OGD to a control level. GFAP intensity increased after OGD exposure, but MSCs treatment did not significantly reduce GFAP intensity. Given that PGE2 was previously demonstrated to reduce LPS mediated neuro-inflammation, it was hypothesized that PGE2 produced by the MSCs would also reduce GFAP intensity reduction and morphological changes. Total PGE2 levels decreased with OGD, and monolayer MSCs treatment restored PGE2 levels. Encapsulated MSCs increased the total PGE2 levels. However, these differences are not significantly different than control. There is no difference in GFAP intensity with astrocytes exposed to exogenous PGE2 during recovery. These in vitro studies demonstrate that encapsulated MSCs are a viable option for reducing not only LPS mediated increase in neuro-inflammation, but also astrocyte activation. However, PGE2 did not mediate astrocyte attenuation. The mechanism of reducing astrocyte activation is still not understood and further studies are needed.

ETD_7805

M.S.

Includes bibliographical references

by Timo Roehrs

doi:10.7282/T38W3GSS

ETD graduate

The author owns the copyright to this work.