Growth factors, stem cells, and stroke.

Postischemic neurogenesis has been identified as a compensatory mechanism to repair the damaged brain after stroke. Several factors are released by the ischemic tissue that are responsible for proliferation, differentiation, and migration of neural stem cells. An understanding of their roles may allow future therapies based on treatment with such factors. Although damaged cells release a variety of factors, some of them are stimulatory whereas some are inhibitory for neurogenesis. It is interesting to note that factors like insulin-like growth factor-I can induce proliferation in the presence of fibroblast growth factor-2 (FGF-2), and promote differentiation in the absence of FGF-2. Meanwhile, factors like transforming growth factor-beta can induce the differentiation of neurons while inhibiting the proliferation of neural stem cells. Therefore, understanding the role of each factor in the process of neurogenesis will help physicians to enhance the endogenous response and improve the clinical outcome after stroke. In this article the authors discuss the role of growth factors and stem cells following stroke.