Expression of TrkB-like immunoreactivity in non-neural cells of rat periodontal ligament.
The Trk family, a group of high-affinity neurotrophin receptors, is divided into three subtypes, TrkA, TrkB and TrkC. These were originally found in neural elements, and are involved in neural development, maintenance and survival. Recent studies have shown that non-neural cells in vitro also express mRNA encoding some neurotrophin receptors. In our preliminary study, TrkB-like immunoreactivity (LI) was found in the various non-neural cells in the rat periodontal ligament. The present study was undertaken to clarify which cell types express Trk-LI, in particular two types of TrkB-LI, in the periodontal ligament of mature rats, using an immunocytochemical technique with polyclonal antibodies. Intense full-length TrkB-LI was clearly recognized in non-neural cells such as fibroblasts, osteoclasts, odontoclasts and cementoblasts as well as in neural elements. Relatively large cells with many cytoplasmic processes were also frequently immunopositive for full-length TrkB. Immunocytochemistry for TrkB[TK-], a truncated type, also demonstrated a similar immunostaining pattern to that of full-length TrkB in non-neural periodontal cells, and intense positive reactions in endothelial cells. Some non-neural cells were positive for TrkA and TrkC. These findings suggest that neurotrophic factors, the ligands of the Trk family, have certain effects on the proliferation and/or differentiation of non-neural cells, as well as on their neurotrophic functions.
Ochi
K
K
Department of Orthodontics, Niigata University School of Dentistry, Japan.
Saito
I
I
Hanada
K
K
Maeda
T
T
D000818:Animals; D002352:Carrier Proteins; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008565:Membrane Proteins; D008854:Microscopy, Electron; D009414:Nerve Growth Factors / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010513:Periodontal Ligament / Q000378:metabolism* / Q000648:ultrastructure; D011505:Protein-Tyrosine Kinases; D051381:Rats; D017208:Rats, Wistar; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D020801:Receptor, Ciliary Neurotrophic Factor; D020917:Receptor, trkA / Q000378:metabolism; D020813:Receptor, trkB / Q000378:metabolism; D020812:Receptor, trkC / Q000276:immunology / Q000378:metabolism; D017475:Receptors, Nerve Growth Factor / Q000378:metabolism*; D013194:Staining and Labeling / Q000379:methods
D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D020801:Receptor, Ciliary Neurotrophic Factor; D017475:Receptors, Nerve Growth Factor; C064371:Ntrk2 protein, mouse; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases; D020917:Receptor, trkA; D020813:Receptor, trkB; D020812:Receptor, trkC