Blood vessel formation after soft-tissue implantation of hyaluronan-based hydrogel supplemented with copper ions

The possibility of ameliorating bone healing of implanted bone allografts is a field of great interest. Early vascular invasion is a key factor in bone allograft incorporation. It is well known that copper ions (Cu2+) show a proangiogenic action favouring the development of new vessels. In this work a hyaluronan based 50% hydrogel (Hyal-50%) was enriched with (Cu2+) and its proangiogenic activity was evaluated. Fifteen Sprague Dawley female rats were submitted to the subcutaneous implantation of Hyal-50%, freeze-dried bone allografts, Hyal-50%-Cu2+, freeze-dried bone allografts plus Hyal-50% and freeze-dried bone allografts plus Hyal-50%-Cu2+. One month later, histomorphometric analysis evidenced the presence of a fibrous-reactive capsule around all specimens showing significant differences among groups (p<0.0005). The highest thickness of the fibrous capsule was found around the freeze-dried bone implants (p<0.05); as well as the Hyal-50%-Cu2+ plus freeze-dried bone (15.2%, p<0.05) and Hyal 50% plus freeze-dried bone (21.4%, p<0.0005) implants showed a significant higher thickness compared with Hyal 50% and Hyal-50%-Cu2+. Statistical analysis showed a significant (p<0.01) higher vascular density in Hyal- 50%-Cu2+ and Hyal-50%-Cu2+ plus freeze-dried bone group when compared to other groups. The present preliminary results suggest the advantages offered by the combined use of a well-known biocompatible and tissue healing promoting material (Hyal-50%) and a new technique that consists of stimulating tissue vascularization using Cu2+ and that bone allograft incorporation may benefit from this technology.