Research Interests

My research focuses on two major dentin noncollagenous proteins  dentin sialoprotein (DSP) and phosphoporyn (PP) which are encoded within a single DSP-PP transcript. Their appearance is coupled to the conversion of uncalcified predentin to calcified dentin and PP in particular is believed to participate in the initiation and control of hydroxyapatite formation. Mutations in the DSP coding regions are linked to dentinogenesis imperfecta I and II, a defective dentin disease affecting 1 in 7000 newborns. DSP-PP expression is tightly restricted to odontoblasts and preameloblasts, although a small amount of DSP protein has been detected in bone. Furthermore, multiple DSP-PP transcripts were identified in teeth which likely result in various DSP/PP isoforms with different functions during various mineralization phases. We are currently defining DSP-PP transcript expression and DSP/PP protein function in dentin mineralization. Our long-term goal is to better define the fundamental molecular/genetic processes contributing to odontoblast differentiation, function and dentin mineralization and to apply this knowledge to better facilitate tooth regeneration, and to possibly correct defective dentin mineralization diseases such as dentinogenesis imperfecta II.

Selected Publications

Ritchie HH and Li XR.  "The identification of a rat dentin DSP cDNA only sequence".  Eur. J. Oral Sciences.  109:342-347, 2001.

Ritchie HH, Wang LH, and Knudtson K.  "A Novel Rat 523 Amino Acid Phosphophoryn: Nucleotide Sequence and Genomic Organization.” Biochemica et Biophysica Acta 1520:212-222, 2001. 

Ritchie HH, Jun Liu, Kasugai S and Moller PM.  "Mineralization and Phosphophoryn Expression in an Odontoblastic Cell Culture with a Dentin-like Structure." In Vitro Cellular & Developmental Biology-Animal 38:25-29, 2002.

Ritchie HH, Li XR, Hanks CT, Knudtson K and Wang L-H.  The conservation and regulation of rat DSP-PP gene.  Connective Tissue Research. 43:331-337, 2002. 

Lundquist P, Ritchie HH, Moore K, Lundgren T and Linde A.  Phosphate and calcium uptake by rat odontoblast-like MRPC-1 cells concomitant with mineralization. J Bone and Mineral Research 17:1801-1813, 2002.

Nakamura Y, Slaby I, Matsumoto K, Ritchie HH, and Lyngstadaas, SP. Immunohistochemical Characterization of Rapid Dentin Formation Induced by Enamel Matrix Derivative.  Calcified Tissue International.  Accepted. 2003.