Association between secreted phosphoprotein-1 (SPP1) polymorphisms and low bone mineral density in women

The effect of genetic polymorphisms on treatment duration following premolar extraction

To elucidate genetic factors affecting orthodontic treatment duration, we employed targeted next-generation sequencing on DNA from the saliva of 117 patients undergoing orthodontic treatment after premolar extraction. The clinical characteristics of patients are summarized, and the association of clinical variables with treatment duration was assessed. Patients whose treatment duration deviated from the average were classified into an extreme long group or an extreme short group. We identified nine single nucleotide polymorphisms (SNPs) of six genes that significantly differed in the two groups via targeted sequencing. The frequency of the CC genotypes of WNT3A, SPP1 (rs4754, rs9138), and TNFSF11, TT genotype of SPP1 (rs1126616), and GG genotype of SFRP2 was significantly higher in the extreme long group than in the short group. In the extreme short group, the TC genotype of SPP1, AA genotype of P2RX7, CT genotype of TNFSF11, and AG genotype of TNFRSF11A tended to exhibit higher frequency than in the long group. Taken together, we identified genetic polymorphisms related to treatment duration in Korean orthodontic patients undergoing premolar extraction. Our findings could lead to further studies predicting the prolongation of the orthodontic treatment duration, and will be of great aid to patients as well as orthodontists.

Amelotin is expressed in retinal pigment epithelium and localizes to hydroxyapatite deposits in dry age-related macular degeneration

Deposition of hydroxyapatite (HAP) basal to the retinal pigment epithelium (RPE) is linked to the progression of age-related macular degeneration (AMD). Serum-deprivation of RPE cells in culture mimics some features of AMD. We now show that serum-deprivation also leads to the induction of amelotin (AMTN), a protein involved in hydroxyapatite mineralization in enamel. HAP is formed in our culture model and is blocked by siRNA inhibition of AMTN expression. In situ hybridization and immunofluorescence imaging of human eye tissue show that AMTN is expressed in RPE of donor eyes with geographic atrophy ("dry" AMD) in regions with soft drusen containing HAP spherules or nodules. AMTN is not found in hard drusen, normal RPE, or donor eyes diagnosed with wet AMD. These findings suggest that AMTN is involved in formation of HAP spherules or nodules in AMD, and as such provides a new therapeutic target for slowing disease progression.

Effect of CBX7 deficiency on the socket healing after tooth extractions

CBX7 is shown to down-regulate the expression of osteopontin (OPN) that is associated with osteoblast function. Here, we studied the role of CBX7 in the wound healing of tooth extraction socket in which osteoblast activity is critical via comparison between CBX7-knockout (CBX7-/-) mice and their wild-type (WT) counterparts of 6 weeks old with maxillary first molar extracted. Mice were euthanized at 7, 14, and 21 days after extractions, and alveolar sockets were assessed by semi-quantitative histomorphometry for hard tissue healing, including new bone fill (Masson's trichrome staining), osteoblast activity (OPN/osterix, Osx), osteoclast activity (tartrate-resistant acid phosphatase, TRAP), and for soft tissue healing, including blood vessels (alpha smooth muscle actin, α-SMA). Also, the bone microarchitecture was evaluated by micro-CT. In radiological analysis, CBX7-/- mice increased bone mass significantly more than WT mice did. Consistently, both the amount of new bone fill and OPN/Osx-immunopositive cells in the extraction sockets were significantly increased in CBX7-/- mice at each time point with respect to their WT siblings, while osteoclast number exhibited a trend of more increase in CBX7-/- mice at all time points as well. In agreement with enhanced bone formation during socket healing, significantly elevated α-SMA-immunopositive area was noted in CBX7-/- mice in contrast to WT mice. Taken together, these data suggest that CBX7 deficiency has a positive effect on tooth extraction socket healing.