Figure 1.

Elevated expression of periostin in OA cartilage. A) Total RNA was isolated from 6 pools of normal and OA cartilage. For each pool, 5–10 individual cartilage samples (1 g each) were pooled. RNA was hybridized against human U133A arrays. After normalization, periostin expression was expressed in arbitrary units. B) RT-qPCR analysis of periostin mRNA in 13 normal and 19 OA cartilage specimens from human knee joints. ELISA (C) and Western blot analysis (D) of periostin levels in protein extracts from 6 OA and 4 non-OA cartilage samples. ELISA periostin values were normalized to total cartilage protein. Horizontal lines: mean values. E) Immunohistochemical analysis of lesional and nonlesional OA knee cartilage identified cell-associated periostin in lesional areas. OA knee cartilage from a total knee replacement was sectioned and stained for periostin with Vectastain reagents (Vector Laboratories, Burlingame, CA, USA). A, B) Mann-Whitney test. C) Nonparametric 2-tailed Student’s t test.