Inhibition of TGF-β1 signaling reduces fibrosis, neo-angiogenesis, and osteogenesis in the BM of Gata1^low mice. (A) Morphological appearance of a femur (original magnification ×1.5), (B) BM cellularity, and representative (C-D) reticulinic fiber determinations by Gomori-Silver and (E,F) microvessel density determinations by CD34 staining of femur sections from vehicle- and SB431542-treated Gata1^low mice. Original magnification ×20. Quantification with the Methamorph program of the Gomori-Silver and CD34 staining are presented as mean (±SD) of results obtained with 3 mice per experimental point in D and F. Results are compared with those observed in untreated Gata1^low and wild-type littermates (pink and gray horizontal bars). Values statistically different (P < .05) between untreated wild-type and Gata1^low mice and vehicle- and SB431542-treated Gata1^low mice are indicated by ^& and *, respectively. (G) Hematoxylin-eosin staining of femur/tibias from untreated wild-type and Gata1^low mice or from Gata1^low mice treated with either SB431542 or vehicle, as indicated. Representative areas of medulla entrapped within the bone are presented at larger magnification on the right. Blue arrowheads indicate bone trabeculae protruding within the medulla. Red arrowheads indicate MKs embedded in areas of medulla surrounded by the bones. Magnification ×4 and ×20, as indicated.