Target finding of pain nerve fibers: neural growth mechanisms in the tooth pulp.
The tooth pulp has a dense sensory innervation which, upon stimulation, conveys sensory signals perceived as pain. This innervation, which originates from the trigeminal ganglion, is established through a series of regulated steps during development, and represents an interesting example of tissue targeting by pain-specific nerves. We have investigated various potentially neurotrophic and neurorepulsive influences during this process. The dental papilla/pulp appears to secrete neurite growth inhibitory molecular factors at early stages, which prevent nerve fibers from entering the tissue at what appears to be inappropriate timepoints. Later, a shift from repulsive to attractive factors apparently takes place, and nerve fibers then enter the tooth. When nerve fibers have invaded the dental mesenchyme, a complicated interplay of secreted and membrane-bound factors probably directs the nerve terminals to appropriate sites. Laminin-8 (alpha4beta1gamma1, Lm-411), which is produced by pulpal cells, emerges as an important candidate molecule in this context. Insights into the interactions between the dental pulp nerve fibers and their environment may become important in the search for novel ways to ameliorate pain in the tooth, as well as at other sites.
Fried
Kaj
K
Karolinska Institutet, Center for Oral Biology, Department of Odontology, Novum, P.O.Box 4064, S-141 04 Huddinge, Sweden. Kaj.Fried@ki.se
Lillesaar
Christina
C
Sime
Wondossen
W
Kaukua
Nina
N
Patarroyo
Manuel
M
D000818:Animals; D003782:Dental Pulp / Q000294:innervation* / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000502:physiology*; D006801:Humans; D009411:Nerve Endings / Q000254:growth & development; D009414:Nerve Growth Factors / Q000378:metabolism*; D016501:Neurites / Q000502:physiology*; D009619:Nociceptors / Q000254:growth & development*; D015398:Signal Transduction / Q000502:physiology; D014070:Tooth / Q000294:innervation / Q000378:metabolism
D016326:Extracellular Matrix Proteins; D009414:Nerve Growth Factors