Humna fetal neural stem cells: Proliferation and differentiation in response to growth factors and role in locomotor recovery after spinal cord contusion injury

Abstract

Human fetal neural stem cells (hNSCs) may be useful for developing a cell-based therapy to treat spinal cord injury (SCI). In these studies we examined the effects of epigenetic mitogens on proliferation and differentiation of hNSCs in vitro and the outcome of hNSC grafting into contusion injured rat spinal cords in vivo.\r\nCells were cultured in seven regimens with basic fibroblast growth factor (bFGF), epidermal growth factor (EGF) and leukemia inhibitory factor (LIF), either alone or in combinations. We found that a combination of bFGF, EGF and LIF expanded hNSCs more efficiently than any other treatment. Differentiation patterns of hNSCs expanded under different conditions were also analyzed. Cells expanded under different mitogen regimens varied in their phenotypic differentiation patterns and also in their response to a priming treatment with a combination of bFGF, heparin and laminin (FHL). Particularly, significant generation of cholinergic cells was observed only in hNSCs expanded with EGF/bFGF or EGF/bFGF/LIF, but not with other treatment regimens. \r\nSubsequently, we examined the effect of temporal transplantation of hNSCs into contusion injured rat spinal cords. FHL-primed or unprimed hNSCs were grafted into the epicenter of injured spinal cords on either the same day, three or nine days after a moderate contusion injury. Histological analyses of the spinal cord revealed that stem cells survived three months post engraftment only in animals that received grafts at 9-day post injury. The survival rates of such cells were significantly lower than those grafted into the intact cord. Both primed and unprimed hNSCs differentiated into neurons; however, only primed cells gave rise to cholinergic neurons. Functional assessment based on the BBB score and exploratory activity three months after grafting showed that hindlimb function and/or trunk stability improved significantly in only the group that received primed hNSC transplants on the ninth day post contusion. \r\nOur results indicate that 1) hNSCs are highly plastic with their proliferation and differentiation potential dependent upon different growth factor treatments; and 2) in vitro stem cells priming is beneficial to achieve the desired differentiating phenotypes in vivo and help to attenuate locomotor deficits after SCI. \r\n