Figure 2

Asymmetric TNF-induced knee arthritis is associated with ipsilateral PLN collapse and decreased afferent lymphatic flow. The mice described in Figure 1 were subjected to NIR-ICG imaging to quantify lymphatic drainage from their lower limbs, prior to sacrifice for histology, and data from a representative animal are shown. The NIR-ICG images of the left (A) and right (B) lower limb of the mouse obtained 30 minutes after the ICG injection into the footpad (red arrows) illustrates the dramatic difference in afferent lymphatic flow to the PLN (green arrows) as evidenced by the lack of signal in the collapsed (A) versus the bright signal in the expanding (B) PLN. Micrographs (5x) of the H&E stained histology of the PLN reveal the shrunken phenotype of the collapsed PLN (C), compared to the expanding PLN with enlarged paracortical sinuses (* in D). Micrographs of the H&E (E, F) and TRAP (G, H) stained histology of the knees taken at 5x and 10x respectively, confirmed the presence of extensive synovitis (arrows in E) and focal erosions (G) in the left knee ipsilateral to the collapsed PLN, in contrast to the very early stage arthritis observed in the right knee ipsilateral to the expanding PLN (F, H).