Fig. 6. Impaired growth-plate angiogenesis in Bmpr1a^CKO mice. (A) H/E-stained sections from E16.5 distal femurs. (B) Adjacent sections immunostained for PECAM. In wild-type mice, blood vessels are restricted to the chondro-osseous junction (boxed area in B), where apoptotic chondrocytes are located. In Bmpr1a^CKO mutants, blood vessels can be seen invading the region of the growth plate occupied by late hypertrophic chondrocytes.