ISOLATION OF MURINE CEMENTOBLASTS - UNIQUE CELLS OR UNIQUELY-POSITIONED OSTEOBLASTS

While cementoblasts express a number of mineral-related proteins, incl uding bone sialoprotein (BSP), osteopontin (OPN) and osteocalcin (OC), these proteins do not appear to be expressed by cells of the intermed iate dental follicle/periodontal ligament (PDL). This information was utilized in an experimental strategy to isolate presumptive cementobla sts from the root surface of day 24 murine mandibular first molars. Us ing microscopic dissection techniques, molars were carefully extracted from their alveolar crypts and subjected to trypsin-collagenase diges tion to remove adherent cells. Primary cultures were established and a ssayed for expression of proteins known to be expressed by cementoblas ts at this timepoint in vivo (i.e. BSP, OPN, OC) and also an odontobla st-specific protein (i.e. DSP) to rule out contamination by pulpal cel ls. A subgroup of cells were found to express Type I collagen (89% of cells), BSP (46%), OPN (23%) and OC (30%); DSP was not detected within these cultures. We propose that cells within this heterogeneous popul ation, which express this profile of osteogenic proteins, represent ce mentoblasts. The availability of a cementoblast cell line will make po ssible rigorous and controlled in vitro analysis of these cells and al low for determination of the unique characteristics of these cells not shared with other cells, particularly osteoblasts.