Figure 1.

LPA promotes inflammation and cell death in zebrafish after SCI. A: LPA₁ expressed in the brain and spinal cord of adult zebrafish. B, brain; L, liver; M, muscle; SC, spinal cord; NC, negative control consisting of no cDNA in the PCR. B and C: In intact adult zebrafish spinal cord, in situ hybridization shows LPA₁ expression in large neuronal cells along the spinal cord (arrowheads) and in glial cells along the midline in spinal cord tissue (arrows). Six hours after SCI in the mpx:GFP line, there is little infiltration of neutrophils into the control fish and some TUNEL-labeled cells (D); however, in LPA-treated animals, increased neutrophil infiltration and neuronal apoptosis was demonstrated by TUNEL staining (E). F: Quantitation of neutrophils at the lesion site reveals a significant increase in LPA treatment versus control (Con). Results are given as mean ± SEM (n = 5 in each group). *P < 0.001 by two-tailed t-test, 95% confidence. G: Three days after SCI in the mpeg1:GFP line demonstrating infiltration of mpeg1-expressing cells in the lesion site (box enlargement; H) and their presence distal from the lesion site (box enlargement; I). J: LPA treatment increased the presence of mpeg1-expressing cells distal to the lesion site (box enlargement; K), with similar macrophage infiltration (box enlargement; L). M: Quantitation of macrophages/microglia shows a significant increase in LPA-treated versus control (Con) spinal cords. Results are mean ± SEM (n = 8 in each group) *P < 0.001 by two-tailed t-test, 95% confidence. Scale bars: 50 μm (B, C, H, I, K, and L); 100 μm (D and E); 300 μm (G and J).