Figure 2.

Extracellular processing of TGFβ is decreased in the absence of Spp1. (A) Western blot analysis of concentrated CM from Spp1−/−mdx and Spp1+/+mdx fibroblasts revealed that levels of proteolytically processed (25 kDa) TGFβ are decreased in CM lacking Spp1. Ponceau staining demonstrates equal loading of the concentrated CM. (B) Schematic representation of the hypothesis that Spp1 is required for normal extracellular processing of TGFβ that in turn controls collagen I expression. (C) Western blot analysis of total muscle extracts from Spp1+/+mdxB10 and Spp1−/−mdxB10 mice demonstrates decreased levels of processed TGFβ in the absence of Spp1. n = 4 of each genotype. Quantitative analysis of the western blot is shown in (D). Asterisk indicates statistical significance of P < 0.05. The nitrocellulose membrane was stained with ponceau after transfer and used to assess gel loading. Molecular weight markers were run in the middle lane and used to estimate TGFβ size.