Human β-defensin-2 gene transduction of dental pulp cells: A model for pulp antimicrobial gene therapy

The objective of this study was to determine whether cells from human pulp can be transduced to express the antimicrobial peptide--human β-defensin-2 (HBD-2). Primary human pulp cells and gingival fibroblasts from normal tissue, as well as two mouse cell lines (NIH 3T3 and AT-84) and a human cell line SCC-9 were transduced with a retroviral vector carrying HBD-2 cDNA. ELISA and Northern blot analyses were performed to detect HBD-2 expression by these transduced cells. Antimicrobail assays using recombinant HBD-2 were performed on two caries-associated bacteria Streptococcus mutnas and Lactobacillus acidophilus. The results showed that transduced pulp cells secreted 62.4 ± 27.2 ng/3 days of HBD-2, which was comparable to that by NIH 3T3 (78.0 ± 14.1 ng/4 days), and higher than those by gingival fibroblasts (17.9 ± 7.9 ng/3 days), AT-84 (2.6 ± 1.0 ng/3 days), and SCC-9 (47.6 ± 9.9 ng/3 days). Northern blot analysis showed that the levels of HBD-2 mRNA expression correlated with their protein secretion levels. There was approximately 50% reduction of growth when S. mutans and L. acidophilus were exposed to HBD-2 at 1 µM. Pulp cells appear to be suitable for HBD-2 transduction using retroviral vectors, suggesting a potential for use in controlling pulpal infections.