The effects of fibrin and fibrin-agarose on the extracellular matrix profile of bioengineered oral mucosa.

Several studies have developed efficient oral mucosa constructs using different types of scaffold. However, the changes in the morphology and gene and protein expression profile that could occur in these artificial constructs remain unknown. This study compared the histology and expression of several extracellular matrix molecules in human artificial oral mucosa developed using two different types of scaffolds: fibrin and fibrin-agarose. To that end, bioengineered oral mucosa stromas were constructed from biopsy samples of human oral mucosa and the substitute generated was analyzed at different periods of time in culture. Histological analysis was carried out by light and transmission electron microscopy and the expression of collagen types I, III, and VI, the proteoglycans decorin and biglycan, and the different chains of laminin, were assessed by immunoperoxidase technique. This study found that fibrin scaffolds accelerated fibroblast growth and remodeling of the scaffold, thus enhancing collagen fibrillogenesis. In the fibrin-agarose scaffold, the morphology and organization of the fibroblasts did not change during the culture period. All extracellular matrix proteins analyzed were expressed in both scaffolds. However, in fibrin scaffolds, these proteins were widely distributed and replaced the scaffold during the follow-up period. These results show that the substitutes generated showed histological and molecular similarities with native human oral mucosa stroma. In addition, it was observed that the nature of the biomaterial influenced the behaviour of the oral stromal fibroblasts, thereby modulating their growth, protein synthesis, and collagen fibrillogenesis.

Rheological characterization of human fibrin and fibrin-agarose oral mucosa substitutes generated by tissue engineering.

In regenerative medicine, the generation of biocompatible substitutes of tissues by in vitro tissue engineering must fulfil certain requirements. In the case of human oral mucosa, the rheological properties of tissues deserve special attention because of their influence in the acoustics and biomechanics of voice production. This work is devoted to the rheological characterization of substitutes of the connective tissue of the human oral mucosa. Two substitutes, composed of fibrin and fibrin-agarose, were prepared in cell culture for periods in the range 1-21 days. The time evolution of the rheological properties of both substitutes was studied by two different experimental procedures: steady-state and oscillatory measurements. The former allows the plastic behaviour of the substitutes to be characterized by estimating their yield stress; the latter is employed to quantify their viscoelastic responses by obtaining the elastic (G') and viscous (G'') moduli. The results demonstrate that both substitutes are characterized by a predominant elastic response, in which G' (order 100 Pa) is roughly one order of magnitude larger than G'' (order 10 Pa). But the most relevant insight is the stability, throughout the 21 days of culture time, of the rheological quantities in the case of fibrin-agarose, whereas the fibrin substitute shows a significant hardening. This result provides evidence that the addition to fibrin of a small amount of agarose allows the rheological stability of the oral mucosa substitute to be maintained. This feature, together with its viscoelastic similitude with native tissues, makes this biomaterial appropriate for potential use as a scaffold in regenerative therapies of human oral mucosa.