Cell based therapy reduces secondary damage and increases extent of microglial activation following cortical injury.

Cortical injury elicits long-term cytotoxic and cytoprotective mechanisms within the brain and the balance of these pathways can determine the functional outcome for the individual. Cytotoxicity is exacerbated by production of reactive oxygen species, accumulation of iron, and peroxidation of cell membranes and myelin. There are currently no neurorestorative treatments to aid in balancing the cytotoxic and cytoprotective mechanisms following cortical injury. Cell based therapies are an emerging treatment that may function in immunomodulation, reduction of secondary damage, and reorganization of surviving structures. We previously evaluated human umbilical tissue-derived cells (hUTC) in our non-human primate model of cortical injury restricted to the hand area of primary motor cortex. Systemic hUTC treatment resulted in significantly greater recovery of fine motor function compared to vehicle controls. Here we investigate the hypothesis that hUTC treatment reduces oxidative damage and iron accumulation and increases the extent of the microglial response to cortical injury. To test this, brain sections from these monkeys were processed using immunohistochemistry to quantify oxidative damage (4-HNE) and activated microglia (LN3), and Prussian Blue to quantify iron. hUTC treated subjects exhibited significantly reduced oxidative damage in the sublesional white matter and iron accumulation in the perilesional area as well as a significant increase in the extent of activated microglia along white matter pathways. Increased perilesional iron accumulation was associated with greater perilesional oxidative damage and larger reconstructed lesion volume. These findings support the hypothesis that systemic hUTC administered 24 h after cortical damage decreases the cytotoxic response while increasing the extent of microglial activation.

Geometric Navigation of Axons in a Cerebral Pathway: Comparing dMRI with Tract Tracing and Immunohistochemistry.

Brain fiber pathways are presumed to follow smooth curves but recent high angular resolution diffusion MRI (dMRI) suggests that instead they follow 3 primary axes often nearly orthogonal. To investigate this, we analyzed axon pathways under monkey primary motor cortex with (1) dMRI tractography, (2) axon tract tracing, and (3) axon immunohistochemistry. dMRI tractography shows the predicted crossings of axons in mediolateral and dorsoventral orientations and does not show axon turns in this region. Axons labeled with tract tracer in the motor cortex dispersed in the centrum semiovale by microscopically sharp axonal turns and/or branches (radii ≤15 µm) into 2 sharply defined orientations, mediolateral and dorsoventral. Nearby sections processed with SMI-32 antibody to label projection axons and SMI-312 antibody to label all axons revealed axon distributions parallel to the tracer axons. All 3 histological methods confirmed preponderant axon distributions parallel with dMRI axes with few axons (<20%) following smooth curves or diagonal orientations. These findings indicate that axons navigate deep white matter via microscopic sharp turns and branches between primary axes. They support dMRI observations of primary fiber axes, as well as the prediction that fiber crossings include navigational events not yet directly resolved by dMRI. New methods will be needed to incorporate coherent microscopic navigation into dMRI of connectivity.