Growth factor expression after lesion creation in the avascular zone of the meniscus: a quantitative PCR study in rabbits.

Purpose: To define the variations in the expression of 5 growth factor genes in meniscal tissue after a lesion is created in the avascular zone of the medial meniscus of the rabbit.

Methods: A longitudinal lesion was created in the avascular zone of the anterior horn of the medial meniscus in 42 rabbits. Six animals were killed at 0, 1, 3, 7, 14, 21, and 120 days after lesion creation. Meniscal tissue from the avascular and vascular zones was harvested. A quantitative polymerase chain reaction analysis was performed to evaluate the expression levels of 5 different growth factors: vascular endothelial growth factor A (VEGF-A), insulin-like growth factor 1 (IGF-1), transforming growth factor β1 (TGF-β1), platelet-derived growth factor β (PDGF-β), and interleukin 1β.

Results: The basal expression levels of all the growth factors studied were similar in the avascular and vascular zones. There was an increase in VEGF-A expression in the avascular zone on the 14th day, an increase in IGF-1 expression in the vascular zone on the 14th day, a decrease in PDGF-β expression in both zones in the first week, an increase in interleukin 1β expression in both zones on the first day, and a decrease in TGF-β1 expression in the vascular zone in the first week. At 120 days, the expression levels of all 5 growth factors returned to basal levels.

Conclusions: There are significant variations in the expression of the growth factors studied during the first weeks after meniscal lesion creation. The preinjury expression levels are similar in the avascular and vascular zones and are not significantly different from the basal levels 4 months after injury.

Clinical Relevance: This study identifies potential therapeutic molecular targets (VEGF-A, IGF-1, TGF-β1, and PDGF-β) that can be used in the treatment of meniscal tears.