Summary: This proposal addresses the potential use of bone marrow-derived multipotent adult progenitor cells (MAPCs) as vehicles of trophic factor delivery for the autologous and non-invasive treatment of disease. Evidence from a number of in vitro studies show that differentiation of MAPCs in response to nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), or neurotrophin 3 (NT3) can give rise to neural cell progeny that expresses neuronal phenotypes and genes, and that responds to certain stimuli as functional neurons. Following direct transplantation into brain or intravascular injection, MAPCs have been shown to rapidly migrate and become functionally integrated within the CNS. Although the targeting of circulating injected cells in brain were few, these cells were capable of site-specific differentiation and improving brain function. A number of factors may influence the frequency at which MAPCs promote neural development including the availability of specific trophic factors. The neuroprotective properties of one such factor, the secreted alpha-secretase cleavage fragment of the amyloid precursor protein (sAPPalpha), has been well documented. sAPPa induces neuronal proliferation, viability, and function when administered to cultured cells. sAPPalpha secretion is elevated in the presence of other growth factors, like NGF, and with NGF, sAPPalpha has been shown to act synergistically to enhance neuroprotective activity. Evidence from recent studies suggests that sAPPalpha plays a critical role in the response of the brain to injury. Similar to that seen in cell models, the trophic activity of sAPPalpha in brain may activate other endogenous growth factors, to promote growth factor-receptor binding and neuronal proliferation, and to enhance neuroprotection. In Alzheimer's disease (AD), the amyloidogenic processing of APP reduces the formation of sAPPalpha. This decrease in secreted sAPPalpha levels is thought by some to contribute to neurodegeneration. In these studies, we will explore the influence of sAPPalpha and its possible synergy with NGF on promoting neural differentiation of MAPCs. A second objective is to evaluate the use of MAPCs as a vehicle for sAPPalpha delivery to brain where its interactions with endogenous trophic factors could potentiate neuronal differentiation and reduce neurodegeneration by promoting survival.
To investigate the effects of sAPPa on promoting neural lineage development and its potential for enhancing neuroprotection, we will apply immunologic, cellular and molecular approaches in vitro and in vivo to bone-marrow derived MAPCs and to an animal model of Down syndrome (DS) exhibiting cholinergic cell atrophy and elevated Abeta levels, similar to AD. The specific aims are the following: 1) To evaluate the potential of sAPPalpha to promote MAPC neural lineage development and enhance the neurotrophic/neuroprotective activity of NGF in vitro and 2) To determine if the intravascular administration of sAPPalpha to brain by transfected MAPCs delivers a therapeutic level of sAPPalpha that promotes neuroprotection in an animal model with early stage AD-like neurodegeneration, the Ts65DN mouse.