MMP1 and pulpitis: To determine the underlying mechanisms of TNF-α-induced gene expression in ODs, we detected expression of key molecules in immune-regulatory pathways in dental pulp inflammation under the condition of TNF-α stimulation.24 First, we found that the protein levels of Mmp1, 2, 9, and 13 were positively associated with TNF-α concentrations in A11 (Fig. 3a).