Expression of metalloproteases by cardiac myocytes and fibroblasts in vitro
Related Experiment Video
Updated: Apr 12, 2026
Isolation and Characterization of Adult Cardiac Fibroblasts and Myofibroblasts
Published on: March 12, 2020
K T Borg1, W Burgess1, L Terracio1
1Department of Developmental Biology and Anatomy, University of South Carolina, Columbia, South Carolina USA.
Abstract:
Regulation of the turnover of extracellular matrix (ECM) components has been attributed in part to matrix metalloproteases (MMP). Isolated cardiac myocytes and fibroblasts from different developmental stages express different patterns of MMPs in vitro. Zymography of media and cell extracts of fibroblasts and myocytes indicated several apparent molecular weights (Mr) with gelatinolytic activity with prominent bands at 92 and 72 kDa. No caseinolytic activity was detected. These MMPs were characteristic of known MMP-2 and MMP-9. Fibroblasts predominantly expressed the latent 72-kDa MMP, whereas myocytes expressed a latent 92-kDa MMP. Expression of these MMPs was not affected by density of culture or the type of ECM substrate on which the cells were grown. Sodium dodecyl sulfate (SDS)-activated MMP-2 showed specific cleavage patterns on collagen types I and III but not on fibronectin, collagen type IV, or laminin. The reaction of SDS-activated MMP-2 produced a 140-kDa fragment from collagen types I and III. No specific substrate patterns were observed with activated MMP-9. MMP-2 from fibroblasts could also be activated by mechanical tension developed by fibroblasts within collagen gels or by cyclically stretching Silastic membranes on which the fibroblasts were grown. When mechanical tension was inhibited in collagen gels by antibodies against the β1 integrin, the 72-kDa MMP, or cytochalasin D, the activated band at 62 kDa was not detected. Immunocytochemical localization with antibodies against MMP-2 showed a weak reaction on cardiac myocytes, but intense staining around the focal adhesions of migrating fibroblasts. In collagen gels, staining was localized to the leading pseudopodia of the fibroblasts. Together, these data indicate that the rat MMP-2 is a collagenase primarily associated with cardiac fibroblasts, activated by mechanical tension, and may be important in cellular ECM interactions.
Insights
Matrix metalloproteinases (MMPs) regulate extracellular matrix turnover. Cardiac fibroblasts primarily express MMP-2, activated by mechanical tension, suggesting a role in cardiac ECM remodeling.
Area of Science:
- Biochemistry
- Cell Biology
- Cardiovascular Research
Background:
- Extracellular matrix (ECM) turnover is crucial for tissue homeostasis and is partly regulated by matrix metalloproteinases (MMPs).
- Cardiac myocytes and fibroblasts exhibit distinct MMP expression patterns during development.
- MMPs are implicated in various physiological and pathological processes, including cardiac remodeling.
Purpose of the Study:
- To investigate the expression, activation, and substrate specificity of MMPs in cardiac myocytes and fibroblasts.
- To determine the role of mechanical tension in the activation of MMPs in cardiac fibroblasts.
- To elucidate the specific contribution of MMP-2 and MMP-9 in cardiac ECM regulation.
Main Methods:
- Zymography was used to detect gelatinolytic activity in cell extracts and media.
- SDS-PAGE and Western blotting were employed to characterize MMPs.
- Immunocytochemistry localized MMPs within cardiac tissues.
- Mechanical tension was applied to fibroblasts cultured in collagen gels and on Silastic membranes.
Main Results:
- Cardiac fibroblasts predominantly expressed latent MMP-2 (72 kDa), while myocytes expressed latent MMP-9 (92 kDa).
- Activated MMP-2 specifically cleaved collagen types I and III, producing a 140-kDa fragment.
- Mechanical tension, but not culture density or ECM substrate, activated MMP-2 in fibroblasts.
- Inhibition of mechanical tension or β1 integrin signaling abolished MMP-2 activation.
Conclusions:
- Rat MMP-2 functions as a collagenase primarily associated with cardiac fibroblasts.
- Mechanical tension is a key regulator of MMP-2 activation in cardiac fibroblasts.
- MMP-2 activation by mechanical forces may play a significant role in cardiac fibroblast-mediated ECM remodeling.
