Comparison of pulp and periodontal ligament cells using DNA microarray

Objectives: To evaluate the difference of gene expression human pulp cells (PC) and periodontal ligament cells (PDLC) by using DNA microarray assay and differently expressed genes were confirmed by reverse transcription polymerase chain reaction (RT-PCR). Methods: Pulp and periodontal ligament tissues were collected from extracted 3rd molar (n=10). They were plated and cultured in DMED with 10% fetal bovine serum (FBS). Cells from each tissue were cultured before experiments (5 passages). Total RNA were extracted with RNeasy Mini Kit according to the manufacture's instructions. DNA microarray (Human-8K, digital genomics, Seoul, Korea) was used to analyze 8170 genes with cDNA chip. Characteristic 6 genes out of differently expressed genes (more than 2 folds in each sample) were selected and analyzed by RT-PCR (LUM, WISP1, MMP1, ITGA4, NEFH, TGFβ2). Results: The transcription level of the majority (99%) of 8170 genes remained unchanged between PC and PDLC, exhibiting less than 2-fold differentially expression. DNA microarray revealed that about 1% (70 genes) of all genes were found differentially expressed by 2-fold among them, 51 genes were found to be comparatively more abundant in PC, whereas 19 genes were expressed at higher level in PDLC. RT-PCR revealed that the band intensity of ITGA4, NEFH, and TGF β2 were higher in PC than in PDLC, while that of MMP1, WISP1, and LUM were higher in PDLC than in PC. Conclusion: PC and PDLC appear to display different gene expression patterns that may reflect intrinsic functional difference of the two cell populations. This differential expression of genes may well coordinate with their tissue specific activities during inflammatory/immune responses and in the maintenance of tissue homeostasis.