Matrix metalloproteinase-7 modulates synaptic vesicle recycling and induces atrophy of neuronal synapses

Matrix metalloproteinase-7 (MMP-7) belongs to a family of zinc dependent endopeptidases that are expressed in a variety of tissues including the brain. MMPs are known to be potent mediators of pericellular proteolysis and likely mediators of dynamic remodelling of neuronal connections. While an association between proteases and the neuronal synapse is emerging, a full understanding of this relationship is lacking. Here, we show that MMP-7 alters the structure and function of presynaptic terminals without affecting neuronal survival. Bath application of recombinant MMP-7 to cultured rat neurons induced long-lasting inhibition of vesicular recycling as measured by synaptotagmin 1 antibody uptake assays and FM4-64 optical imaging. MMP-7 application resulted in reduced abundance of vesicular and active zone proteins locally within synaptic terminals although their general levels remained unaltered. Finally, chronic application of the protease resulted in synaptic atrophy, including smaller terminals and fewer synaptic vesicles, as determined by electron microscopy. Together these results suggest that MMP-7 is a potent modulator of synaptic vesicle recycling and synaptic ultrastructure and that elevated levels of the enzyme, as may occur with brain inflammation, may adversely influence neurotransmission.     

A retrospective study to assess patient satisfaction with implant-stabilized prostheses

This study measured the levels of patient satisfaction in those who received treatment with implant-retained overdentures, and compared their status before and after therapy. Satisfaction questionnaires were mailed to patients who had previously worn a removable prosthesis. Questions addressed eating, aesthetics and comfort before and after the treatment. Eighty-six (79.8%) subjects had problems regarding looseness of their denture prior to treatment. Patients were generally satisfied with their implant-retained overdentures in terms of function, comfort, appearance and speech. The results suggest that unstable, problematic complete dentures can be managed by providing patients with implant-retained overdentures. Clinical Relevance: From the patients' perspective, implant-supported overdentures offer overall satisfaction and improvement.