Aortic adaptation to pregnancy: elevated expression of matrix metalloproteinases‐2 and ‐3 in rat gestation

The maternal aorta undergoes substantial functional and structural adaptation in pregnancy. Both aortic diameter and compliance are increased and studies of animal and human gestation indicate that these changes are initiated in early pregnancy and maintained until delivery. The mechanisms underlying aortic adaptation in normal pregnancy remain largely unknown but matrix metalloproteinase enzymes (MMP) are likely to play a key role. Gene expression of candidate MMP and specific tissue inhibitors of MMP (TIMP) were investigated in non‐pregnant, pregnant (days 7, 14, 21) and postpartum (day 7) rat aorta using real‐time PCR. Of the gene transcripts studied (MMP‐2, ‐3, ‐7, ‐9, ‐12, ‐13, MT1MMP, TIMP‐1, ‐2) in rat aorta, only MMP‐3 was significantly elevated with a 24‐fold increase observed in late gestation compared to virgin control (P = 0.0001). MMP‐2 mRNA appeared constitutively expressed and unchanged at time‐points studied, but MMP‐2 activity as assessed by gelatin zymography suggested further modulation after transcription and/or post‐translation in rat aorta with activity increased in early pregnancy (P < 0.01, compared to virgin control). These data suggest that MMP‐2 and MMP‐3 may contribute to adaptive processes in the maternal rat aorta at different gestations and further support a role for this family of enzymes in physiological vascular remodelling.