The role of cell surface markers and enamel matrix derivatives on human periodontal ligament mesenchymal progenitor responses in vitro.

Periodontitis is a chronic-, infectious-disease of the human periodontium that is characterized by the loss of supporting tissues surrounding the tooth such as the periodontal ligament (PDL), cementum and alveolar bone. Regeneration of the periodontium is dependent on the participation of mesenchymal stem/stromal cells (MSC) resident in the PDL. Enamel matrix derivative (EMD), an extract from immature porcine enamel rich in amelogenin protein but that also contain bone morphogenetic protein (BMP), is used to treat periodontal defects. The effects of EMD on MSC cells of the PDL are not well characterized. In this in vitro study, we identify PDL progenitor cells from multiple individuals and demonstrate that EMD stimulates them. We show that the effect of EMD on cell proliferation and migration is mediated through the amelogenin it contains, while the differentiation of these progenitor cells to cell types of mineralized tissue is mainly due to BMP signaling.

Absence of the lysophosphatidic acid receptor LPA1 results in abnormal bone development and decreased bone mass.

Lysophosphatidic acid (LPA) is a lipid mediator that acts in paracrine systems via interaction with a subset of G protein-coupled receptors (GPCRs). LPA promotes cell growth and differentiation, and has been shown to be implicated in a variety of developmental and pathophysiological processes. At least 6 LPA GPCRs have been identified to date: LPA1-LPA6. Several studies have suggested that local production of LPA by tissues and cells contributes to paracrine regulation, and a complex interplay between LPA and its receptors, LPA1 and LPA4, is believed to be involved in the regulation of bone cell activity. In particular, LPA1 may activate both osteoblasts and osteoclasts. However, its role has not as yet been examined with regard to the overall status of bone in vivo. We attempted to clarify this role by defining the bone phenotype of LPA1((-/-)) mice. These mice demonstrated significant bone defects and low bone mass, indicating that LPA1 plays an important role in osteogenesis. The LPA1((-/-)) mice also presented growth and sternal and costal abnormalities, which highlights the specific roles of LPA1 during bone development. Microcomputed tomography and histological analysis demonstrated osteoporosis in the trabecular and cortical bone of LPA1((-/-)) mice. Finally, bone marrow mesenchymal progenitors from these mice displayed decreased osteoblastic differentiation. These results suggest that LPA1 strongly influences bone development both qualitatively and quantitatively and that, in vivo, its absence results in decreased osteogenesis with no clear modification of osteoclasis. They open perspectives for a better understanding of the role of the LPA/LPA1 paracrine pathway in bone pathophysiology.

The effect of microstructured surfaces and laminin-derived peptide coatings on soft tissue interactions with titanium dental implants.

In the present study, we investigated the dental implant protection from peri-implant inflammation by improving the soft tissue adhesion on the titanium surface. Porous titanium was used to create, at the level of the transmucosal part of the implants (the "neck"), a microstructured 3-dimensional surface that would tightly seal the interface between the implant and soft tissue. Cell-specific adhesion properties were induced via an adhesion peptide derived from laminin-5 coupled to native or cross-linked PLL/PGA multilayered polyelectrolyte films (MPFs), which are used for biomedical device coatings. Porous titanium exhibited good cell-adhesion properties, but the colonisation of the material was further improved by a coating with laminin-5 functionalised MPFs and especially with (PLL/PGA)(6,5)-PGA-peptide film. Focal contact formation was observed on cross-linked architectures, reflecting cell anchorage on these surfaces. In contrast, when seeded on laminin-5-functionalised native films, epithelial cells formed only very diffuse focal contacts, but adhered via hemidesmosome formation. In vivo experiments confirmed that the porous titanium was colonised by cells of soft tissue. Altogether, the results indicate that the microstructure of the implant neck combined with a specific bioactive coating could constitute efficient routes to improve the integration of soft tissue on titanium dental implants, which could significantly protect implants from peri-implant inflammation and enhance long-term implant stabilisation.

Human dental follicle cells acquire cementoblast features under stimulation by BMP-2/-7 and enamel matrix derivatives (EMD) in vitro.

The dental follicle (DF) surrounding the developing tooth germ is an ectomesenchymal tissue composed of various cell populations derived from the cranial neural crest. Human dental follicle cells (HDFC) are believed to contain precursor cells for cementoblasts, periodontal ligament cells, and osteoblasts. Bone morphogenetic proteins (BMPs) produced by Hertwig's epithelial root sheath or present in enamel matrix derivatives (EMD) seem to be involved in the control of DF cell differentiation, but their precise function remains largely unknown. We report the immunolocalization of STRO-1 (a marker of multipotential mesenchymal progenitor cells) and BMP receptors (BMPR) in DF in vivo. In culture, HDFC co-express STRO-1/BMPR and exhibit multilineage properties. Incubation with rhBMP-2 and rhBMP-7 or EMD for 24 h increases the expression of BMP-2 and BMP-7 by HDFC. Long-term stimulation of these cells by rhBMP-2 and/or rhBMP-7 or EMD significantly increases alkaline phosphatase activity (AP) and mineralization. Expression of cementum attachment protein (CAP) and cementum protein-23 (CP-23), two putative cementoblast markers, has been detected in EMD-stimulated whole DF and in cultured HDFC stimulated with EMD or BMP-2 and BMP-7. RhNoggin, a BMP antagonist, abolishes AP activity, mineralization, and CAP/CP-23 expression in HDFC cultures and the expression of BMP-2 and BMP-7 induced by EMD. Phosphorylation of Smad-1 and MAPK is stimulated by EMD or rhBMP-2. However, rhNoggin blocks only Smad-1 phosphorylation under these conditions. Thus, EMD may activate HDFC toward the cementoblastic phenotype, an effect mainly (but not exclusively) involving both exogenous and endogenous BMP-dependent pathways.

Guided tissue regeneration in human Class II furcation defects using a diphenylphosphorylazide-cross-linked collagen membrane: a consecutive case series.

BACKGROUND: Several bioabsorbable collagen membranes are either currently available or under investigation for use in guided tissue regeneration (GTR) procedures. The aim of this 12-month reentry study was to evaluate a diphenylphosphorylazide (DPPA)-cross-linked bovine type I collagen membrane in the healing of mandibular Class II furcation defects. The DPPA technique prevents the inclusion of foreign cytotoxic cross-linking substances in the reticulated molecules, thus providing a more biocompatible product. METHODS: Forty non-smoking periodontally compromised adult subjects volunteered for this study, and one defect was randomly selected in each patient. At baseline, plaque index (PI), gingival index (GI), probing depth (PD), gingival margin location (GML), clinical attachment level (CAL), and width of the attached gingiva (AG) were measured. Intrasurgical hard tissue measurements consisted of the vertical open probing attachment level (V-OPAL) and horizontal open probing attachment level (H-OPAL), as well as furcation entrance width (FW) and height (FH) and subclassification of defects according to vertical bone loss. All soft tissue measurements were repeated 12 months after membrane placement using conservative flap reentry surgeries; hard tissue parameters were also assessed at this time. RESULTS: DPPA-cross-linked collagen membranes demonstrated good handling characteristics, and no postoperative adverse tissue reactions or clinically detectable localized allergic responses were observed. GI and PI remained low during the entire study period. When the one year reentry values were compared to the baseline measurements, a significant reduction in PD (1.9 +/- 1.4), FW (2.1 +/- 1.7), FH (2.9 +/- 1.6), and gain in CAL (1.7 +/- 1.5), V-OPAL (2.1 +/- 1.9), and H-OPAL (4.7 +/- 1.4) were observed (P < or = 0.05). However, there were no significant differences in GML or AG. Hard tissue improvements resulted in the complete closure of 30% (12) of the defects, and transformation of 67.5% (27) of the defects to Class I, while one defect remained a Class II (2.5%). CONCLUSIONS: Based on this 12-month clinical reentry study, a DPPA-cross-linked collagen membrane could be beneficial in GTR treatment of Class II mandibular furcation involvements, both in terms of soft and hard tissue improvements.

Radiographic and histologic evaluation of a sinus augmentation with composite bone graft: a clinical case report.

BACKGROUND: The purpose of the present study was to present a clinical case report of a sinus augmentation with a composite bone graft and delayed implant placement with a 5-year follow-up. METHODS: A 40-year-old female in good health required replacement of her partial upper removable denture with a prosthesis supported by implants. Due to insufficient bone, she had to undergo a sinus lift. A block graft of autogenous chin bone, along with anorganic bovine bone covered by collagen, was utilized. Eight months postsurgery, a biopsy core was taken and 3 endosseous implants were placed. RESULTS: The sinus lift and implantation site are illustrated with clinical, radiological, and histological data. The discussion covers the problems raised by the choice of the surgical technique, grafting material, and immediate or delayed placement of the appropriate implant design. CONCLUSION: Our results show that a maxillary sinus augmentation with a composite bone graft is a possible method for creating adequate bone volume before implantation.