Influence of GH and IGF-1 on the Structural and Ultrastructural Organization of the Calcaneal Tendon and Its Biomechanical and Functional Effects.

• Grant number: 25/21761-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: November 01, 2025
• End date: October 31, 2026
• Field of knowledge: Biological Sciences - Morphology - Anatomy
• Principal Investigator: Diego Pulzatto Cury
• Grantee: Tamiris Ferrarotto dos Santos
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 24/02974-7 - INVESTIGATION OF THE EFFECTS OF THE GH/IGF-1 AXIS ON TENDON MAINTENANCE AND REPAIR THROUGH COLLAGEN SYNTHESIS IN TRANSGENIC MICE., AP.R

Abstract

The calcaneal tendon is formed by the fusion of the insertion tendons of the soleus and gastrocnemius muscles, being the largest and strongest tendon in the human body, capable of withstanding tensile loads of up to ten times body weight. To ensure this resistance, its composition is predominantly made up of type I collagen, a fibrillar form highly resistant to tensile forces, with thick fibers organized in a parallel arrangement. These fibers exhibit a characteristic twist: those originating from the tibial side of the muscle mass run obliquely from the deep to the superficial portion, crossing the tendon surface toward the lateral side. Conversely, the fibers originating from the fibular side traverse the deep portion of the tendon toward the tibial side at the insertion. This structural arrangement provides the necessary strength to the tissue. It is well established that conditions such as tendinopathies and hormonal alterations affect this fibrillar organization, modifying the proportion of collagen types and increasing the amount of type III collagen. This type of collagen, being thinner and arranged in networks, has lower resistance to tensile forces, resulting in tendon weakening and increasing the risk of ruptures. Considering that the GH/IGF-1 axis is a regulator of collagen synthesis, this subproject of the Regular Research Grant (FAPESP process no. 2024/02974-7) aims to evaluate, through transgenic mice, how GH action dissociated from IGF-1 alters collagen morphological patterns at the structural and ultrastructural levels, and how these modifications impact the biomechanical and functional properties of the calcaneal tendon. (AU)