Attempts to label matrix synthesis of human root cementum in vitro.
The present study describes the dynamic process of both acellular extrinsic (AEFC) and acellular/cellular intrinsic fiber cementum (AIFC/CIFC) matrix production on growing human teeth. Selected erupting maxillary and mandibular premolars with roots grown to about 70%-95% of their final length were placed in organ culture immediately following extraction. Twelve teeth for short-time labeling were pulse-incubated for 15 min in medium containing 3H-proline and chased for various times in order to follow the migration and secretion of the tracer. Eight teeth for long-time incubation were labeled continuously for 5 h before being chased for 1-8 days in order to label cementum matrix accumulation. After decalcification in ethylene diaminetetraacetic acid (EDTA), their roots were subdivided into about 20 slices each. Epon-embedded sections were prepared for light- and electron-microscopic as well as autoradiographic examination. During CIFC-formation, cementoblasts revealed high intracytoplasmic silver grain concentrations within the first hour after 3H-proline administration. The release of the tracer occurred between 60 to 120 min after administration. After 2 h, cementoblasts and the cementum matrix appeared to be labeled about equally. After 5 h, most of the labeled proteins appeared to be localized in the cementoid. Silver grains increased in number over the cementum matrix from 5-24 h. Very high intracellular grain concentrations within very large cementoblasts corresponded to regions of rapid cementum formation. Tracer-halos around entrapped cells lend support to a multipolar mode of matrix production during CIFC-initiation. The fate of the tracer during the development of early AEFC-matrix was less clear. However, fibroblasts revealed dense intracytoplasmic grain accumulations within the first hour after 3H-proline administration. Thereafter, the tracer localization was vague. This indistinct grain localization reflected the particular mode of AEFC-matrix production characterized by addition of new fibril segments to pre-existing fibers of a collagenous fringe.
Bosshardt
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DD
Department of Oral Structural Biology, University of Zurich, Switzerland.
Schroeder
H E
HE
D000293:Adolescent; D001345:Autoradiography; D001641:Bicuspid / Q000254:growth & development / Q000378:metabolism; D025021:Cementogenesis; D002648:Child; D003094:Collagen / Q000096:biosynthesis; D003739:Dental Cementum / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism*; D005260:Female; D006801:Humans; D007553:Isotope Labeling; D008297:Male; D009924:Organ Culture Techniques; D011392:Proline / Q000493:pharmacokinetics; D014078:Tooth Eruption; D014316:Tritium / Q000493:pharmacokinetics
D014316:Tritium; D003094:Collagen; D011392:Proline