- Tissue-like structures of hippocampal neurons were established in a crystalline three-dimensional (3D) aragonite biomatrix obtained from the exoskeleton of the coral Porites lutea. Cultures were maintained in vitro for up to 5 weeks. Cell viability and regeneration of neuronal properties were studied by immunocytochemical methods, light microscopy image analysis techniques, and scanning electron microscopy. Some portions of the cell population acquired the morphological characteristics of hippocampal pyramidal or granule neurons with axons and dendrites extending in a 3D manner along the surfaces of the crystalline biomatrix. The neurons usually grew on a sheet of glial cells. Within the pore void areas, multiple layers of neurons were formed, many of the neurons growing with no attachment to the crystalline surfaces. The neurons developed mature synaptic connections, with presynaptic sites expressing the synaptic vesicle protein 2 and postsynaptic sites having the shape of dendritic spines and expressing type 1 glutamate receptors, as these cells do under conventional culture conditions. The findings of the present study suggest that neuronal networks growing in a strong 3D aragonite support may find application as tissue replacement material for the central nervous system.