MMP2 and amyotrophic lateral sclerosis: Interestingly, several studies have shown that skin cells share a few typical ALS pathogenic features with neural cells, including the accumulation of proteins such as TDP-43 [59,60], FUS [61] and VCP [62], neuroinflammatory markers such as TNF-a [63] and IL-6 [64], and show increased levels of matrix metalloproteinases 2 and 9 [65].