Developmental process and expression patterns of fibroblast growth factor receptors in murine meniscus after birth

Abstract

Objective To observe the developmental process of murine meniscus after birth and investigate the expression patterns of 3 types of fibroblast growth factor receptors (FGFRs) during this process. Methods Mice at different ages (1 d old and 1, 2, 4, 6 and 12 weeks old) were sacrificed and the knee joints were harvested and embedded in paraffin. The sagittal sections of knee joint were stained with Safranin O-fast green to observe the structure of murine meniscus. The expression of type Ⅰ collagen, type Ⅱ collagen, and 3 types of FGFRs were detected by immunohistochemistry. Results At birth, the meniscus exhibited distinguishable inner and outer regions, with proteoglycan of darker staining rich in the inner region, while the outer region lightly stained. At 1-week age, the inner-outer region was more obvious, and the inner region mainly expressed type Ⅱ collagen, while the outer region expressed type Ⅰ collagen. At 2 weeks, some cells in the anterior horn became hypertrophied, and the hypertrophy was further aggravated at 4 weeks of age. By 6 weeks, ossification tissues were observed in the anterior horn of the meniscus. At 12 weeks, the meniscal developmental process after birth was basically completed, and mineralized structure resembling bone marrow cavity was found in the anterior horn. The expression of the 3 types of FGFRs had similar spatiotemporal pattern which reached a peak at 1~2 weeks of age and then gradually decreased (P < 0.05) with its spatial distribution changing from a uniform distribution to an edged distribution in the inner zone of anterior horn. However, the expression of FGFRs in the posterior horn had no obvious changes. Conclusion During the postnatal development of murine meniscus, the cartilage matrix, collagen distribution and expression patterns of 3 types of FGFRs have spatiotemporal specificity, which suggest that FGFRs play an important role in the meniscal development.

Keywords

• meniscus
• development
• fibroblast growth factor receptors
• mice