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Aim: As part of regenerative bone surgery, according to the principles of tissue engineering and GBR, the use of biomaterials aims to restore bone deficiencies by restoring both functionality and original morphology of the bone tissue. Besides being biocompatible, biofunctional and reabsorbable, the ideal scaffolding should possess an osteoinductive geometry, which depends on many physical-chemical characteristics and, in particular, on a three-dimensional morphology and the placement of molecules, which would determine pore size and interconnection between them. The purpose of this study was, therefore, to carry out an analysis with a scanning electron microscope, in order to evaluate the effect of the diameter size of the scaffold pores on the bio-molecular interaction between osteoblast-like MG63 cells and four biomaterials with different pore sizes: polylactic-co-glycolic acid, deproteinized bovine bone, equine bone, demineralized bone matrix (DBM)., Methods: Through the observations made with SEM and X-ray microanalysis, it is possible to infer how the morphology, the proliferative ability, the modality of adhesion and the differentiation of MG63 cells are influenced in different ways by the porous structure of the various biomaterials used as a substrate for growth., Results: From among all of the biomaterials examined, DBM represented the best substrate for growth; in fact, there would be a more intense and precocious adhesion of MG-63 cells., Conclusion: The strong osteoconductive effect observed in human DBM, seems to be related to the presence of the organic component, while the osteoinductive effect would be mainly attributed to the presence of BMPs.

Calcineurin (CaN), a calmodulin-dependent heterodimer, is, together with NAF-T, involved in the regulation of the Ca++ pump and in the transmission of the activation signal of the immune response. The CaN inhibitor drugs, such as cyclosporin A (CyA), carried by cyclophillin, and tacrolimus, carried by FK-binding protein-12 (FKBP-12), inhibit the binding with the regulatory subunit CaNB. A meta-analysis, comparing tacrolimus with cyclosporin A, has evidenced that tacrolimus significantly increases the diabetes prevalence one year after renal transplant. The diabetogenic effect is due to a direct effect of both drugs on the beta pancreatic cell, in particular on intracellular Ca++ metabolism, which is involved in the insulin secretion and in the reduction of the number of the secretor granules. Some immunological-hystochemical studies, performed on murine pancreas, have evidenced that the FKBP-12 content is higher in beta cells than in alpha cells. This fact allows a high intracellular store of tacrolimus, and a consequently more toxic effect, inside the insulin secreting structures. On the contrary, the low FKBP-12 content of alpha cells involves a higher content of calcineurin and a higher resistance to toxic effects. Finally, an increased incidence of islet cell antibodies (ICA) has been evidenced in patients treated with tacrolimus, as opposed to those treated with CyA.