Transient cellular structures in developing corpus callosum of the human brain

Jovanov-Milošević, Nataša and Benjak, Vesna and Kostović, Ivica (2006) Transient cellular structures in developing corpus callosum of the human brain. Collegium Antropologicum, 30 (2). pp. 375-381. ISSN 0350-6134

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Abstract

The corpus callosum connects two cerebral hemispheres as the most voluminous fiber system in the human brain. The developing callosal fibers originate from immature pyramidal neurons, grow through complex pathways and cross the midline using different substrates in transient fetal structures. We analyzed cellular structures in the human corpus callosum on postmortem brains from the age of 18 weeks post conception to adult, using glial fibrillary acidic protein, neuron-specific nuclear protein, and chondroitin sulphate immunocytochemistry. We found the presence of transient cellular structures, callosal septa, which divide major fiber bundles and ventrally merge with subcallosal zone forming grooves for callosal axons. The callosal septa are composed of glial fibrillary acidic protein reactive meshwork, neurones and the chondroitin sulphate immunoreactive extracellular matrix. The developmental window of prominence of the callosal septa is between 18-34 weeks post conception which corresponds to the period of most intensive growth of callosal axons in human. During the early postnatal period the callosal septa become thinner and shorter, lose their neuronal and chondroitin sulphate content. In conclusion, transient expression of neuronal, glial and extracellular, growing substrate in the callosal septa, as septa itself, indicates their role in guidance during intensive growth of callosal fibers in the human brain. These findings shed some light on the complex morphogenetic events during the growth of the corpus callosum and represent normative parameters necessary for studies of structural plasticity after perinatal lesions.

Abstract in Croatian

Corpus callosum (korpus kalozum, žuljevito tijelo) povezuje moždane hemisfere i predstavlja najvoluminozniji snop aksona u ljudskom mozgu. Tijekom razvitka komisuralna kalozalna vlakna polaze većinom od nezrelih piramidnih neurona moždane kore, rastu duž složenih putova, prelaze mediosagitalnu ravninu telencefalona, koristeći pri tom različite stanične supstrate u prolaznim fetalnim strukturama. U ovom radu analizirali smo strukture u korpusu kalozumu na postmortalnim histološkim rezovima ljudskog mozga od fetalne (18. tjedan nakon začeća) do odrasle dobi. Pronašli smo prolazne stanične strukture kalozalne prečage, između ventralnih snopova aksona, koje se spajaju sa subkalozalnom zonom i oblikuju žljebove u kojima su položeni kalozalni snopovi aksona. Prečage sadrže stanice i vlakna immunoreaktivna na glijalni fibrilarni protein, neurone i izvanstraničnu tvar bogatu hondroitin sulfatom. Tijekom ranog postnatalnog razdoblja kalozalne prečage postaju tanje i kraće, ne sadrže neurone i hondroitin sulfat, a ekspresija glijalnog fibrilarnog proteina bitno je smanjena. Razvojni vrhunac kalozalnih prečaga je u razdoblju od 18. do 34. tjedna od začeća, u vrijeme najintenzivnijeg rasta korpusa kalozuma u čovjeka, što ukazuje na razvojnu ulogu ovih struktura u njegovom rastu i oblikovanju. Ovi nalazi rasvjetljavaju dio složenih morfogenetskih zbivanja tijekom rasta korpusa kalozuma i daju neophodne parametre za daljnje proučavanje strukturne plastičnosti nakon perinatalnog oštećenja mozga.

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