The intracellular pathway involves internalization of collagen and degradation by lysosomal proteases.[62] In the collagen catabolism gene set, genes significantly upregulated in ESR1+ SMC ecotypes from adenomyosis included members of the MMPs (encoded by MMP2, MMP11, MMP15, MMP17, MMP23B, MMP24, MMP28), genes mediating the internalization and lysosomal degradation of collagen (encoded by MRC2), and lysosomal proteases (encoded by CTSB, CTSD, CTSL) (Figure 5I). The gene discussed is CTSB; the disease is adenomyosis.