Asurvey of new factors which involve in development and regeneration process of the periodontal Ruffini endings

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Our previous studies haw revealed an immuno-expression of trk B, a high affinity neurotrophin receptor in the periodontal ligament. Furthermore, we have shown the involvement of BDNF and NT-4/5, ligands for trkB, in the development/regeneration of the periodontal Ruffini endings. However, no information available for the molecules involved in their maturation process to date. Thus, the present study was undertaken to investigate expression of GDNF (glial-cell line derived neutrotrophic factor) and galectin in the periodontal Ruffini endings of the rat incisors. The main results obtained from this study are as follows.1. APCR analysis detected intense signals far GDNF, GFRαl and Ret mRNAs in the trigeminal ganglion. Immunocytochemical analysis demonstrated positive reaction for GFRαl and Ret in about 30% trigeminral neurons, almost which were categorized in medium-sized neurons that mediate mechanotransduction by an image analysis. GDNF-immunoreaction was localized infix satellite cells … More , never in the neurons.2. The mature periodontal Ruffini endings exhibited GDNF, GFRαl and Ret-immunoreactions in the terminal Schwann cells. However, their axon terminals were devoid of GDNF-immunoreaclion. Furthermore, no immunoreaction existed in the periodontal Ruffini endings.3. The periodontal Ruffini endings lacked all kinds of immunoreaction at postnatal 3 days. At postnatal week 1, the terminal Schwarm cells became positive for GFRαl. Apart of the axon terminals showed Ret-immunoreaction at week 2, and a few GDNF-reactive terminal Schwann cells occurred near the thickening axon terminals. Thereafter, the GDNF-positive terminal Schwann cells increase in number.4. An experiment to resect inferior alveolar nerve showed first appearance of the GDNF-positivity in the terminal Schwann cells, spindle-in shape, at postoperative 2 weeks. Maine terminal Schwann cells which had round profile were detectable as GDNF-immunopositive after postoperative 3 weeks. These stage-specific expression patterns might be related to the maturation and maintenance of the periodontal Ruffini endings. Less