Sodium hyaluronate increases vascular ingrowth in the rabbit ear chamber

The rabbit ear-chamber model was used to study the effect of sodium hyaluronate (NaHe, Healon) on the rate of ingrowth of vascular structures of healing granulation tissue. The chamber area covered by granulation tissue was determined by in-vivo microscopy at regular intervals during a period of 32 days. Daily injections of 1% NaHe into the ear chamber, 50 microliters from day 0 to day 7 and 25 microliters from day 8 to day 21, significantly inhibited ingrowth as observed between days 20 and 26, compared with buffer-injected controls. There was no difference between the latter and non-injected chambers. Intermittent injections of 1% NaHe, 50 microliters on days 1 and 5 and 25 microliters on days 9, 13 and 22 significantly increased the ingrowth as observed between days 6 and 18. It was noted that wound macrophages internalized fluorescein-labelled NaHe. The inhibitory effect of daily injections on angiogenesis was probably due to physical hindrance caused by the NaHe. The stimulatory effect of intermittent administration of NaHe on angiogenesis may have several explanations, including activation of macrophages and their release of angiogenetic factors.