It is estimated that $30 billion are spent on musculoskeletal injuries in the United States each year and tendon/ligament injuries represent ~45% of these cases. Incidence of rupture of the Achilles tendon in North America is 5.5 to 9.9/100,000 habitants. After surgery, the patients return to their activity on approximately 85 days, but may range up to 270 days.

The effect of F1 protein extracted from Hevea brasiliensis in Achilles tendon repair in rats subjected to tenotomy.

Three months‐old male Sprague Dawley rats were divided into 3 experimental groups (90 total n): control (C), Kessler‐Tajima suture (K), Kessler‐Tajima plus F1 protein (KP). Catgut suture 5‐0 was used to surgery. Transmission electron microscopy was used to analyze collagen morphology and ultrastructural aspects; western blotting was used to quantify collagen type I and III and light microscopy under polarized light to demonstrates the collagen distribution. All groups were analyzed 2 and 4 weeks after surgery.

Transmission electron microscopy analysis revealed ultrastructural characteristics, in which the presence of macrophages and mast cell were noted in K and KP groups in both analyzed times. Blood vessels among collagen fibrils were noted especially in the groups analyzed after 4 weeks of injury and surgery independent of the treatment. After 2 weeks of surgery in the treated (KP) and non‐treated (K) groups the tendons' weight was increased ~7 times and decreased to ~5.6 after 4 weeks in both groups. Tendon of K group (2 weeks after injury) presented a higher ratio of collagen type III than type I when compared to all other groups, however treated groups analyzed after 2 and 4 weeks presented more collagen type I than non‐treated groups, as well as a higher density of the fibrils collagen. Polarized light microscopy shows collagen fibers arrangement for all tissue. K and KP groups (2 weeks) presented more collagen type III near muscle, and type I near of calcaneus bone; both groups after 4 weeks presented the two types of collagen along the tissue with predominance of type I. C group had only collagen type I in this type of analyze.

F1 protein increases collagen type I and density of collagen fibrils when compared to non‐treated group, therefore apparently may improve tendon repair.

FAPESP #2015/24087‐3