Activation of matrix metalloproteinase-2 from hepatic stellate cells requires interactions with hepatocytes

Area of Science:

• Biochemistry
• Cell Biology
• Hepatology

Background:

• Matrix metalloproteinase (MMP)-2 activation is vital for extracellular matrix remodeling.
• The precise mechanisms of MMP-2 activation, particularly involving membrane-type MMP (MT-MMP-1) and tissue inhibitor of metalloproteinase (TIMP)-2, remain incompletely understood.
• Investigating cell-cell interactions in the liver is key to deciphering MMP-2 activation pathways.

Purpose of the Study:

• To elucidate the role of cell-cell cooperation in the activation of pro-MMP-2 within the liver microenvironment.
• To determine the specific contributions of hepatocytes and hepatic stellate cells (HSCs) to MMP-2 activation.
• To identify the cellular components and mechanisms responsible for MMP-2 processing.

Main Methods:

• Utilized pure and co-culture systems of primary hepatocytes and HSCs.
• Employed Northern blot analysis and in situ hybridization to assess gene expression (MMP-2, TIMP-2, MT-MMP-1).
• Performed zymography to detect latent and activated forms of MMP-2 and analyzed plasma membrane-enriched fractions.

Main Results:

• HSCs expressed MMP-2, TIMP-2, and MT-MMP-1 mRNA, while hepatocytes did not.
• Latent MMP-2 was detected in HSC cultures, with higher amounts in co-cultures.
• Hepatocytes induced the activation of MMP-2 in HSC-conditioned medium via a plasma membrane-dependent mechanism, confirmed by inhibition studies (EDTA, heat, trypsin).

Conclusions:

• HSC expression of MMP-2, TIMP-2, and MT-MMP-1 alone is insufficient for pro-MMP-2 secretion in its active form.
• Hepatocytes play a critical role in MMP-2 activation through a plasma membrane-associated mechanism.
• Cell-cell interactions between hepatocytes and HSCs are essential for regulating MMP-2 activation in vivo.