Proton spin relaxation study with pulsed NMR on the plasticization of Na+ ion-selective electrode membranes prepared from PVCs with different degrees of polymerization.

The proton spin-spin relaxation times (T2) of ion-selective electrode membranes with differences in the polymerization degree of the incorporated poly(vinyl chloride) (PVC) polymers were investigated. T2 measurements were performed using Hahn-Echo, Solid-Echo and Carr-Purcell-Meiboom-Gill (CPMG) pulse sequences. Analyses of the T2 measurements by Hahn-Echo pulse sequences could realize the estimation of the homogeneity and compatibility for a series of ion-selective electrode membranes and reveal a relationship with the electromotive force (EMF) response in the low-concentration region of the Na+ ions. On the other hand, the normalized derivative spectra from T2 measurements by Solid-Echo and CPMG pulse sequences could approximately visualize the degree of plasticization for such potentiometric polymeric membranes. Moreover, differences in the polymerization degrees of the incorporated PVCs were scarcely found to affect the selectivity coefficients of the Na+-ISEs based on bis(12-crown-4).

Identification of superficial zone articular chondrocyte stem/progenitor cells.

Identification of progenitor/stem cell populations that differentiate specifically towards superficial zone articular chondrocytes is an unmet challenge for cartilage tissue engineering. Using fluorescence activated cell sorting (FACS) analysis we found a characteristic pattern of "side population" (SP) stem cells identified by the Hoechst 33342 dye. We established micromass cultures from this population of cells and tested their chondrogeneic potential. Control (untreated) cultures were minimally stained for Alcian blue - a marker of chondrogenesis. However, with BMP-7 treatment, Alcian blue staining was increased. Superficial zone protein - a specific marker for articular cartilage superficial zone chondrocytes - increased with BMP-7 and/or TGF-beta1 treatment in SP micromass cultures. Our results demonstrate the presence of stem/progenitor cells in the SP fraction isolated from the surface zone of bovine cartilage and have the ability to specifically differentiate towards the superficial zone articular chondrocyte.

Immortalization of cementoblast progenitor cells with Bmi-1 and TERT.

UNLABELLED: A cementoblast progenitor cell line designated BCPb8 was successfully isolated from dental follicle cells immortalized with Bmi-1 and hTERT. BCPb8 showed the potential to differentiate into cementoblasts on implantation into immunodeficient mice. BCPb8 was confirmed to be the first established cementoblast progenitor cell line and will provide a useful model for investigating cementogenesis. INTRODUCTION: The dental follicle is the mesenchymal tissue surrounding the developing tooth germ. During tooth root development, progenitor cells present in the dental follicle are believed to play a central role in the formation of periodontal components (cementum, periodontal ligament, and alveolar bone). However, little more is known about the biology of these progenitors. Previously, we observed that cultured bovine dental follicle cells (BDFCs) contained putative cementoblast progenitors. To further analyze the biology of these cells, we attempted to isolate cementoblast progenitors from immortalized BDFC through expression of the polycomb group protein, Bmi-1, and human telomerase reverse transcriptase (hTERT). MATERIALS AND METHODS: BDFCs were transduced with replication-deficient retroviruses carrying human Bmi-1(LXSN-Bmi-1), and hTERT (LXSH-hTERT) for immortalization. Single cell clones were established from immortalized BDFC, and differentiation into cementoblasts was assessed by implantation into immunodeficient mice. RESULTS AND CONCLUSION: BDFCs expressing Bmi-1 and hTERT showed an extended life span-90 population doublings more than normal BDFCs-and still contained cells with the potential to differentiate into cementoblasts on implantation into immunodeficient mice. From these cells, we established a clonal cell line, designated BCPb8, which formed cementum-like tissue that was reactive to the anti-cementum-specific monoclonal antibody 3G9 and expressed mRNA for bone sialoprotein, osteocalcin, osteopontin, and type I collagen on implantation. Thus, by using Bmi-1 and hTERT, we succeeded in immortalizing cementoblast progenitor cells from BDFC without affecting differentiation potential. The BCPb8 cell line is the first immortalized clonal cell line of cementoblast progenitors and could be a useful tool not only to study cementogenesis but also to develop regeneration therapy for patients with periodontitis.

Progenitor cells from dental follicle are able to form cementum matrix in vivo.

To address the molecular mechanisms of cementogenesis, we have isolated dental follicle cells and examined them to see if they contain cementoblast progenitors. Dental follicle tissue was dissected from the root surface of bovine tooth germ and cells were released by digestion with bacterial collagenase. The released cells were maintained as a bovine dental follicle cells (BDFC). To elucidate the differentiation capacity of BDFC, they were transplanted into severe combined immunodeficiency (SCID) mice for 4 weeks. Transplanted BDFC formed cementumlike matrix; in contrast, bovine alveolar osteoblast (BAOB) transplants formed bonelike matrix, and bovine periodontal ligament cells (BPDL) formed a small amount of the cementumlike matrix. Immunohistochemical analysis showed that cementumlike matrix was positive for anti-cementum attachment protein monoclonal antibody, whereas bone-like matrix was negative. These results indicated that the BDFC contained cementoblast progenitors that were able to differentiate to cementoblasts in vivo. They also indicated that the BDFC are phenotypically distinct from BAOB and BPDL, and provide a useful model for investigating molecular mechanisms of cementogenesis.