engleski

Acetylcholinesterase reactivity in extracellular matrix rich transient synaptic layers of the human fetal cortex

Acetylcholinesterase (AChE ; EC 3.1.1.7) is involved in catabolism of neurotransmitter acetylcholine. However, non-enzymatic roles of AChE have also been suggested, based on finding of different AChE isoforms and cellular localisation. There is evidence for the interaction of AChE and extracellular matrix (ECM) molecules (heparin, laminin-1, perlecan, collagen IV), thus AChE may serve as adhesion protein and participate in morphoregulatory processes. Acetylcholinesterase is present in specific growing fiber bundles and extracellular matrix of the developing cortex. It is our hypothesis that in developing cortex, particularly in transient subplate zone, AChE interacts with ECM molecules (chondroitin sulfate, fibronectin, laminin) and serves as a substrate for growth of axonal afferents. This work presents laminar distribution of diffuse ECM-related AChE reactivity in developing cortical wall of human telencephalon. The presence of AChE and acid mucosubstances was investigated by histochemical methods (Lewi's modification of Koelle's method and PAS-Alcian method, respectively), while demonstration of chondroitin sulfate, fibronectin, and laminin was performed by immunocytochemistry. Series of postmortal human brains ranging from 15-34 postconceptional weeks (PCW) were analyzed. We have found that diffuse AChE activity is distributed throughout synaptic subplate zone beginning from 16 PCW, becoming most prominent during the peak of its development and decreasing with the resolution of subplate zone after 34 PCW. The ECM-related AChE staining spatially and temporally overlaps with alcian staining (acid mucopolysaccharides) and fibronectin expression in the matrix of the cortical wall. Interestingly, histochemical visualisation of laminar distribution of acetylcholinesterase reactivity (and ECM molecules) correlates well with the increase in MRI signal intensity in subplate zone. In conclusion, the coexistence of acetylcholinesterase reactivity and ECM fibronectin may indicate their morphogenetic role in ingrowth and target finding of afferent fibers in developing cerebral cortex.

acetylcholinesterase; human fetal cortex

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