Figure 3.

Histological and immunohistochemical (IHC) analysis of the tibia growth plate shows disrupted growth plate morphology and retention of mutant matrilin-3 protein. (A) H&E staining of newborn (NB), 7- and 21-day-old tibia growth plates of wild-type (wt) mice and of mice either heterozygous (wt/m) or homozygous (m/m) for the mutation (PFA-fixed 6 μm sections). The growth plates of new born mice show no overt dysplasia. However, from day 7 and, in particular, at day 21 m/m mice have a disrupted proliferative zone with disorganized columns (insert) and some areas of hypocellularity. (B) IHC using an anti-matrilin-3 antibody on NB, day 7 and 21 tibia growth plates from wt, wt/m and m/m mice (ethanol/acetic acid-fixed 6 μm sections). Chondrocytes in the hypertrophic zone of NB mice homozygous for the mutation show the retention of mutant matrilin-3. By day 7 this retention is more widespread and affects all zones of the growth plate. By day 21 the retention of matrilin-3 has become more extensive and there are significantly reduced levels of staining in the matrix. By day 21 mice heterozygous for the mutation are also exhibiting low-levels of matrilin-3 retention but the amount of matrilin-3 in the ECM appears to be within normal limits.