Neurotrophic factors

Neurotrophic factors, sometimes abbreviated NTFs, are a family of proteins that support the growth, survival, and differentiation of both developing and mature neurons.^[1][2] NTFs exert their trophic effects on neurons by signaling through tyrosine kinases,^[1] usually a receptor tyrosine kinase. Recent research has shown that neurotrophic factors promote the initial growth and development of neurons in the central nervous system and peripheral nervous system and that they are capable of regrowing damaged neurons in test tubes and animal models.^[3] Neurotrophic factors are often released by the target tissue in order to guide the growth of developing axons. Most neurotrophic factors belong to one of three families: (1) neurotrophins, (2) glial cell-line derived neurotrophic factor family ligands (GFLs), and (3) neuropoietic cytokines.^[3] Each family has its own distinct signaling family though the cellular responses elicited often do overlap.^[3]

Currently, neurotrophic factors are being intensely studied for use in bioartificial nerve conduits because they are necessary in vivo for directing axon growth and regeneration. In studies, neurotrophic factors are normally used in conjunction with other techniques such as biological and physical cues created by the addition of cells and specific topographies. The neurotrophic factors may or may not be immobilized to the scaffold structure, though immobilization is preferred because it allows for the creation of permanent, controllable gradients. In some cases, such as neural drug delivery systems, they are loosely immobilized such that they can be selectively released at specified times and in specified amounts.

References

1. Malenka RC, Nestler EJ, Hyman SE (2009). "Chapter 8: Atypical Neurotransmitters". In Sydor A, Brown RY. Molecular Neuropharmacology: A Foundation for Clinical Neuroscience (2nd ed.). New York: McGraw-Hill Medical. pp. 199, 215. ISBN 9780071481274. Neurotrophic factors are polypeptides or small proteins that support the growth, differentiation, and survival of neurons. They produce their effects by activation of tyrosine kinases.
2. Zigmond MJ, Cameron JL, Hoffer BJ, Smeyne RJ (2012). "Neurorestoration by physical exercise: moving forward". Parkinsonism Relat. Disord. 18 Suppl 1: S147–50. doi:10.1016/S1353-8020(11)70046-3. PMID 22166417. As will be discussed below, exercise stimulates the expression of several neurotrophic factors (NTFs).
3. Deister, C. and C.E. Schmidt, Optimizing neurotrophic factor combinations for neurite outgrowth. Journal of Neural Engineering, 2006. 3: p. 172-179.