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Express Yourself

December 15, 2011

During a major portion of its recently completed century of existence as a separate profession, dentistry grew away from medicine.  It became largely a mechanical art.  But during this period of time, it became increasingly apparent that the dividing line between medicine and dentistry is an artificial one; dental conditions are influenced by general physical conditions and vice versa.

Donald A. Wallace and Harold L. Hansen
American Dental Association, September 1940

Salivary gland tissueMore than 70 years later, the dividing line remains written into popular thought.  Dentistry over here, medicine over there.  But scientists continue to make discoveries that show, from a purely biological perspective, just how artificial the distinction really is.  A nice example is the recent work on dentin sialophosphoprotein, or DSPP.  This protein was first identified in the late 1990s as regulating the mineralization, or hardening, of collagen fibers in dentin, the main part of the tooth beneath the enamel and surrounding dental pulp.  Subsequent work has led to two fascinating threads of research.  One, DSPP may have originated back in the mists of time from a gene duplication in reptiles (see The Power of Genomics, May 2011). Two, preliminary work shows DSPP evolved not only to help make dentin but is expressed and likely has filled other biological niches in cementum, bone, cartilage, and, interestingly, several soft tissues.  The latter include secretory cells in the salivary glands, kidneys, lungs, tear ducts, and sweat glands.

But the list of DSPP-expressing tissues has remained incomplete and very much a work in progress.  In the November issue of the Journal of Histochemistry & Cytochemistry, NIDCR grantees for the first time systematically evaluated DSPP expression in a broad array of soft tissues in mice.  They found that the protein is produced in the salivary glands, cartilage, liver, kidney, and brain.  Interestingly, in all of these tissues, except the brain, the expression levels were higher than in bone, indicating important and unexplored functions in these tissues.  Of note, the authors also found that DSPP is not expressed in the heart or spleen.  “In conclusion, this study indicates that DSPP may serve multiple purposes in addition to its role in biomineralization,” the authors summarized.  “Further studies are needed to elucidate the molecular mechanisms by which DSPP functions in non-mineralized tissues."

  • Prasad M, Zhu Q, Sun Y, Wang X, Kulkarni A, Boskey A, Feng JQ, and Qin C, “Expression of Dentin Sialophosphoprotein in Non-mineralized Tissues,” J Histochem Cytochem 2011 Nov 59(11)1009-1021.

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This page last updated: February 26, 2014