Angiogenesis in a delayed revascularization model is accelerated by angiogenic oligosaccharides of hyaluronan.

BACKGROUND

A delayed revascularisation model has been used to assess the angiogenic activity of hyaluronan fragments on impaired wound healing.

EXPERIMENTAL DESIGN

Revascularisation of single, full thickness skin autografts in rats was delayed by subjecting isolated grafts to a sublethal cryoinjury (freeze injury) before implantation. Hyaluronan fragments were delivered to the grafts using slow release pellets (ethylene vinyl acetate copolymer). Rates of release were measured in vitro by ELISA. The angiogenic response to the application of 100 micrograms of low (1 to 4 kDa) molecular weight hyaluronan and 100 micrograms of medium (33 kDa) molecular weight hyaluronan was tested in separate groups of 15 rats and was compared with unstimulated cryoinjured controls (n = 40). The effect of low (1 to 4 kDa) molecular weight hyaluronan on uninjured grafts was also investigated. Return of graft blood flow was measured on anesthetised animals over a 10-day period using laser Doppler flowmetry and 133Xe clearance. Quantitative histologic assessment of the graft vasculature was performed on Days 3, 7, and 10 after implantation.

RESULTS

The 1- to 4-kDa hyaluronan fragments increased blood flow (p < 0.001), as measured by both flow measuring techniques, and increased graft vessel growth, as assessed histologically at each of the three time points (p < 0.05). By contrast, the 33-kDa fragments had no such effect on graft blood flow or vessel growth. Low molecular weight hyaluronan had no effect on either graft blood flow or on vessel growth in uninjured skin grafts.

CONCLUSIONS

The hypothesis that there may be physiologic regulation of angiogenesis by hyaluronan and its metabolites is supported by the results of these studies. The data provide further evidence of the utility of the cryoinjured graft model for the study of in vivo angiogenesis.