Expression of angiogenic factors in the mammalian senescent cell sustaining Trichinella spp. muscle larvae.

Muscle larvae of the mammalian parasitic nematode Trichinella spp. live in a senescent nurse cell (NC). The NC is formed from a portion of the invaded myofiber and muscle satellite cells that fuse with it. In continuation of our previous research, which documented a senescent phenotype in a fully developed NC analyzed 7 months post-infection, we show in this current study that cellular senescence is a primary event during NC establishment, and occurs as early as 26 days post-infection. At both stages of the formation process, 26 days and 7 months post-infection, the NC was found to express angiogenic factors: angiopoietin 2, interleukin 1β, matrix metallopeptidase 2, platelet-derived growth factor D, and vascular endothelial growth factor C. We hypothesize that the nuclei of the degenerating myofiber transforms the senescent program to the fusing satellite cells. Hypersecretory activity of the senescent NC may facilitate the development of a circulatory rete, which has long been known to accompany the formation of the NC-larva complex.