Regeneration of periodontal Ruffini endings in adults and neonates

Abstract

We reviewed the regeneration of periodontal Ruffini endings, primary mechanoreceptors in the periodontal ligament, following injury to the inferior alveolar nerve (IAN) in adult and neonatal rats. Morphologically, mature Ruffini endings are characterized by an extensive arborization of axonal terminals and association with specialized Schwann cells, called lamellar or terminal Schwann cells. Following injury to IAN in the adult, the periodontal Ruffini endings of the rat lower incisor ligament regenerate more rapidly than Ruffini endings in other tissues. During regeneration, terminal Schwann cells migrate into regions where they are never found under normal conditions. The development of periodontal Ruffini endings of the rat incisor is closely associated with the eruption of the teeth; the morphology and distribution of the terminal Schwann cells became almost identical to those in adults during postnatal days 15-18 (PN 15-18d) when the first molars appear in the oral cavity, while the axonal elements showed extensive ramification around PN 28d when the functional occlusion commences. When the IAN was injured in neonates, the regeneration of periodontal Ruffini endings was delayed compared with the adults. The migration of terminal Schwann cells is also observed following IAN injury, after which the distribution of terminal Schwann cells became almost identical to that of the adults, i.e., PN 14d. Since the interaction between axon and Schwann cell is important during regeneration and development, further studies are required to elucidate its molecular mechanism during the regeneration as well as the development of the periodontal Ruffini endings.

Interaction between Schwann Cells and Osteoblasts In Vitro

“…In periodontal ligament, Schwann cells extend their cytoplasmic processes toward the axon terminals of Ruffini endings and wrap themselves around them. Some bioactive molecules produced by Schwann cells make an important contribution to the maturation and regeneration of periodontal Ruffini endings (Alkhamrah et al, 2003;Wakisaka and Atsumi, 2003). When a Schwann cell graft has been applied to repair peripherial nerve injuries, it has been reported to have a preferential effect on functional recovery (Hess et al, 2007;Wakao et al, 2010).…”

Surface functionalization of TiO2 nanotubes with minocycline and its in vitro biological effects on Schwann cells

“…It was reported that a variety of neurotrophic factors secreted by Schwann cells could induce stem cells to differentiate into neuron-like cells [ 14 ]. Moreover, bioactive molecules secreted by these cells significantly contribute to the maturation and regeneration of periodontal Ruffini endings [ 15 ]. Therefore, Schwann cells were served as an in vitro cell model to investigate the enhancement of osseoperception around dental implants.…”

Effect of implant surface microtopography on proliferation, neurotrophin secretion, and gene expression of Schwann cells

“…Schwann cells are the glial cells of the peripheral nerve system and play indispensable roles during neural development and regeneration 13–15. In addition, bioactive molecules secreted by these cells significantly contribute to the maturation and regeneration of periodontal Ruffini endings 16, 17. Grafting of Schwann cells to repair peripheral nerve injuries in vivo has been reported to be effective in nerve regeneration and functional recovery 18, 19.…”