Insulin-like growth factor 1 receptor signaling in tenocytes is required for adult tendon growth

Abstract

Tenocytes serve to synthesize and maintain collagen fibrils and other matrix proteins in tendon. The underlying biological mechanisms of postnatal tendon growth and repair are not well understood. Insulin-like growth factor 1 (IGF1) plays an important role in the growth and remodeling of numerous tissues, but less is known about IGF1 in tendon. We hypothesized that IGF1 signaling is required for proper tendon growth in response to mechanical loading through regulation of collagen synthesis and cell proliferation. We conditionally deleted the IGF1 receptor (IGF1R) in scleraxis (Scx) expressing tenocytes, and compared to control Scx:IGF1R+ mice, Scx:IGF1RΔ mice demonstrated reduced tenocyte proliferation and smaller tendons in response to mechanical loading. Additionally, we identified that both the PI3K/Akt and ERK pathways are activated downstream of IGF1 and interact in a coordinated manner to regulate cell proliferation and protein synthesis. These studies indicate that IGF1 signaling is required for proper postnatal tendon growth.