The 4th lumbar vertebrae and the left femur of all of the mice were
collected and fixed in 4% paraformaldehyde for 48 h. After dehydration
and embedding, the 4th lumbar vertebrae and the distal femur were
embedded in polymethyl-methacrylate (PMMA) and processed into
240-mm-thick sections in the coronal plane using a rotation microtome.
Subsequently, all of the sections were hand-grounded to a thickness
of 20 mm for VG staining, which was used for staining collagen
fiber [32].