Differential MMP-2 activity of ligament cells under mechanical stretch injury: an in vitro study on human ACL and MCL fibroblasts.
Recent studies have revealed that following injuries, ligament tissues such as anterior cruciate ligaments (ACL), release large amounts of matrix metalloproteinases (MMPs). These enzymes have a devastating effect on the healing process of the injured ligaments. Although these enzymes are produced following ligament injuries, because of different healing capacities seen between the medial collateral ligament (MCL) and ACL, we were curious to find if the MMP activity was expressed and modulated differently in these tissues. For this purpose ACL and MCL fibroblasts were seeded on equi-biaxial stretch chambers and were stretched in different levels. The stretched cells were assayed using Zymography, Western Blot and global MMP activity assays. The results showed that within 72 h after injurious stretch, production of 72 kD pro-MMP-2 increased in both ACL and MCL. However, the ACL fibroblasts generated significantly more pro-MMP-2 than the MCL fibroblasts. Furthermore we found in ACL pro-MMP-2 was converted more into active form. With 4-aminophenyl mercuric acetate (APMA) treatment, large amounts of pro-MMP-2 were converted into active form in both. This indicates that there is no significant difference between ACL and MCL fibroblasts in post-translational modification of MMP-2. The fluorescent MMP activity assays revealed that the MMP family activities were higher in the injured ACL fibroblasts than the MCL. Since the MMPs are critically involved in extracellular matrix (ECM) turnover, these findings may explain one of the reasons why the injured ACL hardly repairs. The higher levels of active MMP-2 seen in the ACL injuries may disrupt the delicate balance of ECM remodeling process. These results suggest that the generation and modulation of MMP-2 may be directly involved in the different responses seen in ACL and MCL injuries.
Zhou
David
D
Department of Bioengineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412, USA.
Lee
Hwa Sung
HS
Villarreal
Francisco
F
Teng
Annabelle
A
Lu
Erick
E
Reynolds
Shirley
S
Qin
Chuan
C
Smith
Joel
J
Sung
K L Paul
KL
D000328:Adult; D016118:Anterior Cruciate Ligament / Q000166:cytology / Q000201:enzymology*; D000070598:Anterior Cruciate Ligament Injuries; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D066298:In Vitro Techniques; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D017888:Medial Collateral Ligament, Knee / Q000166:cytology / Q000201:enzymology* / Q000293:injuries*; D008875:Middle Aged; D010662:Phenylmercuric Acetate / Q000031:analogs & derivatives / Q000494:pharmacology; D013314:Stress, Mechanical; D013439:Sulfhydryl Reagents / Q000494:pharmacology
D017077:Culture Media, Conditioned; D013439:Sulfhydryl Reagents; C010024:4-aminophenylmercuriacetate; D020778:Matrix Metalloproteinase 2; D010662:Phenylmercuric Acetate