Relevance of tenascin-C and matrix metalloproteinases in vascular abnormalities in murine hypoplastic lungs.
BACKGROUND
Tenascin-C (TN-C), an extracellular matrix glycoprotein, is crucial to cell-migration, proliferation, apoptosis and remodeling of tissues, with a potential role in pathobiology of pulmonary hypertension. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are crucial to the integrity of the extracellular matrix. TN-C and MMPs are counter-regulatory molecules, which influence the vascular integrity through modulations of elastin. We have a murine model of pulmonary hypoplasia with coexistent diaphragmatic hernia, vascular abnormalities and excessive arterial smooth muscle cell (SMC) proliferation.


OBJECTIVE
Our objective was to investigate modulations of TN-C and MMPs in hypoplastic lungs and their possible contribution to the observed pulmonary vascular abnormalities.


METHODS
We addressed our objectives by pursing immunoblotting and immunohistochemistry and zymography/reverse zymography to assess the alterations in activities of MMPs and their inhibitors.


RESULTS
We observed significant down-regulation of MMP-9 activity in hypoplastic lungs at the later fetal developmental stages, whereas MMP-2 activity assessed by gelatin zymography remained unaltered. Reverse zymography revealed up-regulation of activities of TIMP-1, -2, -3 and -4 in hypoplastic lungs during later fetal development, with pronounced increases in TIMP-3 and -4 activities. Furthermore, immunoblot analyses and immunohistochemistry revealed that TN-C protein was down-regulated in developing hypoplastic lungs, compared to normal lungs.


CONCLUSIONS
(1)TN-C is known to inhibit vascular SMC proliferation. But, decrease in TN-C in hypoplastic lungs may support the observed arterial SMC proliferation. (2) Our studies showed that in hypoplastic lungs the SMC apoptosis is not affected, thus suggesting that SMC proliferation and apoptosis may be two separate processes in pulmonary hypoplasia with coexistent diaphragmatic hernia. Together, our data showed an imbalance in the extracellular matrix proteins, which may contribute to the pulmonary vascular abnormalities.
Chinoy
Mala R
MR
Lung Development Research Program, Department of Surgery, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA. mchinoy@psu.edu
Miller
Shane A
SA
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D001808:Blood Vessels / Q000002:abnormalities* / Q000737:chemistry / Q000201:enzymology; D002455:Cell Division / Q000502:physiology; D005260:Female; D047109:Fetal Development; D005865:Gestational Age; D015151:Immunoblotting; D007150:Immunohistochemistry; D008168:Lung / Q000098:blood supply* / Q000737:chemistry* / Q000473:pathology*; D020778:Matrix Metalloproteinase 2 / Q000032:analysis; D020780:Matrix Metalloproteinase 9 / Q000032:analysis; D020782:Matrix Metalloproteinases / Q000032:analysis* / Q000502:physiology; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D020411:Oligonucleotide Array Sequence Analysis; D011247:Pregnancy; D019063:Tenascin / Q000032:analysis* / Q000502:physiology; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000032:analysis; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000032:analysis; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000032:analysis; D019714:Tissue Inhibitor of Metalloproteinases / Q000032:analysis; D000097792:Tissue Inhibitor of Metalloproteinase-4
D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D020782:Matrix Metalloproteinases; D019063:Tenascin; D019715:Tissue Inhibitor of Metalloproteinase-1; D019716:Tissue Inhibitor of Metalloproteinase-2; D019717:Tissue Inhibitor of Metalloproteinase-3; D019714:Tissue Inhibitor of Metalloproteinases; D000097792:Tissue Inhibitor of Metalloproteinase-4