Stem cells provide a novel potential source to replace dead neurons and supporting tissue in brain damaged by chronic ischemia as seen, for example, in acute hypoxia.  Some investigations of animals and short-term human bone marrow transplants demonstrated that bone marrow cells are a source of neurons and can repair damaged brain (e.g., during stroke). The mechanisms of this functional improvement are currently the focus of intense research, creating a need for new study methodologies to assess the effectiveness of such strategies.  Elucidation of stem-cell related mechanisms of regeneration is crucial to developing effective stem cell-based therapies that could extend the lifespan of patients with diseases that could be treated by tissue regeneration.  One such disorder is chronic brain damage due to hypoxia resulting from sleep apnea.

Recently our group purified from adult murine bone marrow (BM) a homogenous population of rare (~0.01% of BMMNC) CXCR4⁺, Oct-4⁺ SSEA-1⁺, Sca-1⁺ lin^- CD45^- very small embryonic like (VSEL) stem cells.  Direct electron microscopic analysis revealed that these cells are small (~2-4 m), posses large nuclei surrounded by a narrow rim of cytoplasm, and contain open-type chromatin (euchromatin) that is typical for embryonic stem cells.  Based on our preliminary data we presented a novel hypothesis that the pool of CXCR4⁺ epiblast derived VSEL is deposited in the BM during early development.  These cells subsequently serve as a reserve mobile pool of stem cells that may be mobilized into peripheral blood and play an important role in brain regeneration – where they are chemoattracted by an SDF-1 gradient.  Furthermore, we hypothesize that an age-related decrease in the marrow pool of these circulating VSEL may contribute to aging of the central nervous system, resulting in less effective repair.To investigate these issues, we propose the following four specific aims:

Specific Aim # 1.  Neural differentiation of bone marrow-derived VSEL.

Specific Aim # 2.  Optimize mobilization of VSEL into peripheral blood.

Specific Aim # 3.  Develop an approach to expand VSEL.

Specific Aim # 4.  Determine the efficacy of VSEL in brain regeneration in vivo in a murine model of acute hypoxia.