Sodium hyaluronate regulating angiogenesis during Achilles tendon healing

The aim of this study was to evaluate the effect of SH (sodium hyaluronate-NaHA) on vascular endothelial growth factor (VEGF) and type IV collagen expression during the Achilles-tendon healing process. Adult New Zealand white rabbits (n=32) aged 4 months and weighing 2.7-3.9 kg were used. The rabbits were randomly divided into two groups, and each group was divided into two subgroups and monitored for 6 and 12 weeks. Tendo calcanei were incised transversely and repaired. An injection of 0.5 ml NaHA (15 mg/ml) was administered between the tendon and paratenon of the right leg and repeated twice at one-week intervals. Equal numbers of animals were sacrificed at the 6th and 12th weeks, and the repaired tissue was examined macroscopically and histologically for the presence of VEGF and type IV collagen expression every week. The decrease in the amount of adhesion tissue and the acceleration of tendon healing in the NaHA group were significantly high when compared with control groups at 6 and 12 weeks (p<0.001, p<0.05). In the NaHA group, due to vascular proliferation VEGF immunostaining was strongly positive in the 6th week (p<0.05), and remained positive in the 12th week (p<0.05). Similar immunostaining findings were detected for type IV collagen in the 6th week. However, there was a significant decline in immunostaining rate in the 12th week (p<0.05). The increases in VEGF and type IV collagen expression following SH administration might be an indication that SH may partly be involved in regulation of angiogenesis.