Activated Macrophages and Microglia Induce Dopaminergic Sprouting in the Injured Striatum and Express Brain-Derived Neurotrophic Factor and Glial Cell Line-Derived Neurotrophic Factor

• Published in: The Journal of neuroscience Vol. 19; no. 5; pp. 1708 - 1716
• Main Authors: Batchelor, Peter E, Liberatore, Gabriel T, Wong, John Y. F, Porritt, Michelle J, Frerichs, Fenneke, Donnan, Geoffrey A, Howells, David W
• Format: Journal Article
• Language: English
• Published: United States Soc Neuroscience 01.03.1999; Society for Neuroscience
• Subjects: Adrenergic Fibers - metabolism; Adrenergic Fibers - physiology; Animals; Astrocytes - cytology; Astrocytes - physiology; Autoradiography; Brain-Derived Neurotrophic Factor - biosynthesis; Cell Size; Corpus Striatum - injuries; Corpus Striatum - physiology; Dopamine - metabolism; Gene Expression; Glial Cell Line-Derived Neurotrophic Factor; Immunohistochemistry; In Situ Hybridization; Macrophage Activation - physiology; Macrophages - cytology; Macrophages - metabolism; Macrophages - physiology; Male; Mice; Mice, Inbred C57BL; Microglia - cytology; Microglia - metabolism; Microglia - physiology; Nerve Growth Factors; Nerve Regeneration - physiology; Nerve Tissue Proteins - biosynthesis; RNA, Messenger - biosynthesis; Wound Healing - physiology
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/jneurosci.19-05-01708.1999

Nigrostriatal dopaminergic neurons undergo sprouting around the margins of a striatal wound. The mechanism of this periwound sprouting has been unclear. In this study, we have examined the role played by the macrophage and microglial response that follows striatal injury. Macrophages and activated microglia quickly accumulate after injury and reach their greatest numbers in the first week. Subsequently, the number of both cell types declines rapidly in the first month and thereafter more slowly. Macrophage numbers eventually cease to decline, and a sizable group of these cells remains at the wound site and forms a long-term, highly activated resident population. This population of macrophages expresses increasing amounts of glial cell line-derived neurotrophic factor mRNA with time. Brain-derived neurotrophic factor mRNA is also expressed in and around the wound site. Production of this factor is by both activated microglia and, to a lesser extent, macrophages. The production of these potent dopaminergic neurotrophic factors occurs in a similar spatial distribution to sprouting dopaminergic fibers. Moreover, dopamine transporter-positive dopaminergic neurites can be seen growing toward and embracing hemosiderin-filled wound macrophages. The dopaminergic sprouting that accompanies striatal injury thus appears to result from neurotrophic factor secretion by activated macrophages and microglia at the wound site.