Chronic expression of PPAR-[delta] by oligodendrocyte lineage cells in the injured rat spinal cord

• Published in: Journal of comparative neurology (1911) 2010-03, Vol.518 (6), p.785
• Main Authors: Almad, Akshata, McTigue, Dana M
• Format: Article
• Language: English
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.22242

The transcription factor peroxisome proliferator-activated receptor (PPAR)-[delta] promotes oligodendrocyte differentiation and myelin formation in vitro and is prevalent throughout the brain and spinal cord. Its expression after injury, however, has not been examined. Thus, we used a spinal contusion model to examine the spatiotemporal expression of PPAR-[delta] in naïve and injured spinal cords from adult rats. As previously reported, PPAR-[delta] was expressed by neurons and oligodendrocytes in uninjured spinal cords; PPAR-[delta] was also detected in NG2 cells (potential oligodendrocyte progenitors) within the white matter and gray matter. After spinal cord injury (SCI), PPAR-[delta] mRNA and protein were present early and increased over time. Overall PPAR-[delta]+ cell numbers declined at 1 day post injury (dpi), likely reflecting neuron loss, and then rose through 14 dpi. A large proportion of NG2 cells expressed PPAR-[delta] after SCI, especially along lesion borders. PPAR-[delta]+ NG2 cell numbers were significantly higher than naive by 7 dpi and remained elevated through at least 28 dpi. PPAR-[delta]+ oligodendrocyte numbers declined at 1 dpi and then increased over time such that >20% of oligodendrocytes expressed PPAR-[delta] after SCI compared with 10% in uninjured tissue. The most prominent increase in PPAR-[delta]+ oligodendrocytes was along lesion borders where at least a portion of newly generated oligodendrocytes (bromodeoxyuridine+) were PPAR-[delta]+. Consistent with its role in cellular differentiation, the early rise in PPAR-[delta]+ NG2 cells followed by an increase in new PPAR-[delta]+ oligodendrocytes suggests that this transcription factor may be involved in the robust oligodendrogenesis detected previously along SCI lesion borders. J. Comp. Neurol. 518:785-799, 2010. © 2009 Wiley-Liss, Inc.