RNA isolation from alveolar bone and gene expression analysis of RANK, RANKL and OPG: A new tool to monitor bone remodeling and healing in different bone substitutes used for prosthetic rehabilitation

Objective:(i) To validate a simple and efficient method for extracting high quality RNA from small samplesof bone tissue, (ii) to test its application on limited amounts of grafted oral bone and (iii) to analyze thegene expression of the OPG/RANK/RANKL system and IL-6 in “spontaneous healing” and grafted tissue.Design: 26 patients in need of extraction of one lower molar tooth were divided in 3 groups. In group A(8 patients) the alveolar socket was left for spontaneous healing, in group B (8 patients) it was filled witha hydroxyapatite scaffold while in group C (10 patients) it was filled with hydroxyapatite granules. Asmall amount of bone was scraped from the alveolar site and sent for analysis. Four months later a newbone specimen was harvested during implant bed preparation.Results: IL-6 increased over time in all groups and in particular to the grafted groups. RANK, RANKL andOPG increased over time in all groups, except for RANK in group B. The RANKL/OPG ratio showed anegative value in group A and even more in group B, while it was positive in group C.Conclusions: The alveolar site grafted with a granular biomaterial behaved similar to the physiologicalhealing group but displayed a slow remodeling process. RANK, RANKL, OPG and the RANKL/OPG ratiomight be able to distinguish among different biomaterials and represent different healing patternsaccording to different clinical conditions.