The present study aims at evaluating, in a rat model of cartilage defect, the potential of various polymers as filling and repair biomaterials. The macroscopic and histological observations are compared to biochemical parameters in order to appreciate the pertinence of the latter as suitable criteria in tissue engineering.
A hydrogel, consisting of hyaluronic acid (HA), covalently substituted by hydrophobic alkyl chains (HA12, HA18) and an alginate sponge, alone (Asp) or combined with HA (AHAsp) or combined with HA and chondrocytes (HYBsp) were evaluated. Cartilage lesions were drilled in femoral trochlea of rats. The analyses were performed on trochlea as well as on patella and condyles.
Repairs achieved with hydrogels had a similar macroscopic appearance than those afforded by AHAsp and HYBsp. Best macroscopic and histological scores were obtained with HA18 and HYBsp in comparison with alginate group (P< 0.01 and P< 0.02 respectively). Biochemical evaluations confirmed the presence of similar amounts of proteoglycans in the repaired zones and in the controls, though with different DeltadiC4S/DeltadiC6S ratios and enhanced HA levels.
Hydrogels or sponges proved to be colonized by cells synthesizing a matrix with a high HA content. The matrix obtained eventually turns hyaline and takes over the scaffold. The addition of HA and/or chondrocytes to Asp significantly improves the macroscopic and histological scores (P< 0.05 and P< 0.02 respectively). However, biochemical parameters are significantly different of those evaluated in native cartilage. The present study shows that only biochemical parameters allow to discriminate between various biomaterials in tissue engineering and are essential informations which should be taken into account in addition to macroscopic and histological observations.