MMP-3 deficiency does not influence the length and number of CA1 dendrites of hippocampus of adult mice

Abstract

Over the past two decades, metalloproteinases (MMPs), including MMP-2, MMP-3, and MMP-9, have been implicated as important players in mechanisms underlying various forms of neuroplasticity. In particular, MMP-3 was found to be involved in both cognitive functions and in plasticity phenomena, but the underlying molecular mechanisms remain largely elusive. In general, it is believed that functional plasticity of neurons is associated with morphological alterations. Interestingly, MMP-9, in addition to playing a key role in synaptic plasticity, was found to affect plasticity-related spine morphology changes. Whereas the involvement of MMP-3 in shaping synapse morphology upon induction of synaptic plasticity awaits determination, it has been demostrated that MMP-3 knockout results in clearly altered apical dendrite morphology in pyramidal neurons in mouse visual cortex. Considering that the involvement of MMP-3 in synaptic plasticity has been most extensively documented for the CA1 hippocampal region, we decided to investigate whether genetic deletion of MMP-3 affects neuronal morphology in this area. To this end, we used Golgi staining to compare dendritic morphology of pyramidal neurons in the CA1 region in MMP-3-deficient and wild-type mice. Surprisingly, in contrast to the results obtained in cortex, extensive analysis of dendritic morphology in the CA1 region revealed no significant differences between MMP-3 knockout and wild-type groups. These results suggest that the impact of MMP-3 on neuronal morphology may be region-specific.

Extracellular Metalloproteinases in the Plasticity of Excitatory and Inhibitory Synapses

“…In this study, aberrant neuronal morphology was reported in the visual cortex of MMP3-deficient mice [126]. Similar morphological impairments were described in the cerebellum [127] but not in CA1 hippocampal pyramidal cells [128].…”

Long-term plasticity of inhibitory synapses in the hippocampus and spatial learning depends on matrix metalloproteinase 3

“…However, MMP3 deficiency reduces ECM digestion; therefore, the cognitive enhancement that was observed in the present study cannot be ascribed to extensive ECM cleavage. Although anatomical studies ruled out gross morphological changes in CA1 pyramidal neurons of Mmp3 −/− mice [ 48 ], as well as an impairment in NMDA-dependent excitatory LTP [ 20 ], it cannot be excluded at the present stage that compensatory changes in the genetically modified animals could have contributed to the observed behavioral phenotype in this model.…”

Matrix metalloproteinase-3 in brain physiology and neurodegeneration

“…35 On the contrary, Nowak et al have shown that there are no significant differences between morphology of MMP-3 -/pyramidal neurons in the CA1 hippocampal field in comparison to the wild-type group. 36 Collectively, these studies suggest that the functioning of the MMP-3 in developing CNS is more complex and may depend on the region of the brain.…”