Figure 3

Transannular puncture injury upregulates matrix metalloproteinase 2 (MMP-2). Immunohistochemical staining of MMP-2 in rat caudal discs subjected to transannular punctures by using hypodermic needles (18-g, 22-g, and 26-g) or subjected to sham surgery (no puncture). Although AF cells in all tissue sections exhibited some immunopositivity, more positive cells were found, and the qualitative intensity of staining was markedly higher in punctured discs, particularly for 18-g needles. We previously showed that 18-g hypodermic needle punctures are associated with a greater incidence of degenerative changes in the AF [16].