ODONTOBLAST PROCESSES IN DEVELOPING TEETH INVESTIGATED BY SERIAL SECTION ELECTRON MICROSCOPY Ninna P. Shuhaibar1,2, Arthur R. Hand 1,2 and Mark Terasaki 1 1Department of Cell Biology, University of Connecticut Health Center, Farmington CT. 2Department of Skeletal, Craniofacial and Oral Biology, University of Connecticut Health Center, Farmington CT. [email protected], [email protected] INTRODUCTION MOUSE INCISOR CROSS-SECTION THREE-DIMENSIONAL VIEW OF ODONTOBLAST PROCESS The tooth is composed mostly of dentin, the highly mineralized collagenous matrix Lingual Odontoblast cell model with its process in a 3D reconstruction. that supports the enamel. A) Side view. B) Rotated 90 degrees. The odontoblast cells are responsible for the assembly, mineralization, maintenance and repair of the dentin matrix. The cell bodies remain at the outer edge of the pulp, A) B) and most of these activities are performed by thin cytoplasmic processes that extend form the cell bodies towards the dentin-enamel junction. Odontoblasts The formation of dentin: Pulp Odontoblasts Predentin Odontoblast Enamel cell body Pulp Dentin Odontoblasts processes Enamel The odontoblast Ameloblasts processes are plates or lamellae Labial 5 week old mouse, toluidine blue stained section (1.5 microns thick) SERIAL SECTIONS Predentin Representative images of ultra-thin serial sections through an odontoblast cell with its Dentinal Tubules process. A total of 200 sections of 75 nm were collected. The section number is shown in Dentin the upper right corner. The image were analyzed by a 3D reconstruction software (Trak EM2 /FIJI/ Image J). We are investigating the three-dimensional structure of the odontoblast process, 139 164 165 166 using serial section electron microscopy. CONCLUSION Odontoblast Our results indicate that the shape of the odontoblast process is a plate, and not a tubule as METHOD FOR SERIAL SECTION ELECTRON MICROSCOPY the textbook figures indicate. 1 FUTURE DIRECTIONS Process with - Compare processes in labial vs buccal regions heavy metals Odontoblast processes - Compare processes in incisors vs molars and Dissect the Predentin - Investigate the morphology of the odontoblast processes in the dentin dehydrate mandible - Compare different stages of incisor development Cardiac Split in 5 segments Embed tissue perfusion Decalcifying - Characterize the branches from the main process in epoxy resin Dentin fix solution - Identify neurons in the predentin/dentin region block 167 168 169 188 2 3 4 Thin serial sections Attach sections on tape Image using scanning ACKNOWLEDGEMENT collected on tape. to a wafer. electron microscopy. - Valentina Baena - Training grant NIH/NIDCR T90DE021989 REFERENCES - Terasaki, M., Shemesh, T., Kasthuri, N., Klemm, R., Schalek, R., et al., 2013, Stacked Endoplasmatic Reticulum Sheets Are Connected by Helicoidal Membrane Motifs, Cell, 154: 285-296. - Kasthuri, N., Hayworth, K., Berger, D., Lee Schalek, R., Conchello J., et al., 2015, Saturated Reconstruction of a Volume of Neocortex, Cell, 162, 648-661. 5 microns - Smith, C. and Nanci, A., 1989, A Method for Sampling the Stage of amelogenesis on Mandibular Rat Incisor Using the Molars as a Reference for Dissection, Anat. Rec., 225:257-266 .