Analysis of Gene Expression in Periapical Lesions Using DNA microarrays

Objective: DNA microarrays allow the assessment of the expression of large numbers of genes simultaneously. The present study utilized microarrays to assess change of gene expression in progress of induced periapical lesions. Methods: The dental pulps of mandibular first and second molars were exposed in BALB/cJ mice. Pulps were inoculated with a mixture of four endodontic pathogens (Prevotella intermedia, Peptostreptococcus micros, Streptococcus intermedius, and Fusobacterium nucleatum) on day 0. Animals were killed on days 3, 14, and 42 (n=4 per group). Non-exposed and non-infected animals were established as negative controls (day 0, n=4). Bone blocks containing molars and surrounding tissues were isolated, and total RNA was extracted. After reverse transcription, cDNA was used to probes for commercially-available DNA microarray systems (R & D Systems and Affymetrix). The levels of gene expression were determined and normalized to a housekeeping genes and internal controls using computer software. Results: In cytokine-related genes, the results demonstrate that signal transduction genes related to immune cell activation and inflammatory cytokine production were expressed on day 3. On day 14, inflammatory cytokine-related genes, TGFb super family-related genes, and angiogenesis factor genes were up-regulated. On day 42, apotosis-related genes were expressed, whereas some TGFb super family genes were down-regulated. Conclusion: We conclude that DNA microarray analysis is useful in providing a Ôgene profileÕ as periapical lesions progress from acute to chronic phases. This study was supported by grants DE-09018 and DE-11664 from the N.I.D.C.R.