A bilayered tissue engineered in vitro model simulating the tooth periodontium.

Due to the complexity of the structure of the tooth periodontium, regeneration of the full tooth attachment is not a trivial task. There is also a gap in models that can represent human tooth attachment in vitro and in vivo. The aim of this study was to develop a bilayered in vitro construct that simulated the tooth periodontal ligament and attached alveolar bone, for the purpose of tissue regeneration and investigation of physiological and orthodontic loading. Two types of materials were used to develop this construct: sol-gel 60S10Mg derived scaffold, representing the hard tissue component of the periodontium, and commercially available Geistlich Bio-Gide® collagen membrane, representing the soft tissue component of the tooth attachment. Each scaffold was dynamically seeded with human periodontal ligament cells (HPDLCs). Scaffolds were either cultured separately, or combined in a bilayered construct, for 2 weeks. Characterisation of the individual scaffolds and the bilayered constructs included biological characterisation (cell viability, scanning electron microscopy to confirm cell attachment, gene expression of periodontium regeneration markers), and mechanical characterisation of scaffolds and constructs. HPDLCs enjoyed a biocompatible 3-dimensional environment within the bilayered construct components. There was no drop in cellular gene expression in the bilayered construct, compared to the separate scaffolds.

Investigating the vascularization capacity of a decellularized dental pulp matrix seeded with human dental pulp stem cells: in vitro and preliminary in vivo evaluations.

AIM: To investigate the vascularization capacity of a decellularized dental pulp matrix (DDP) of bovine origin seeded with human dental pulp stem cells (hDPSCs) in vitro and to present preliminary in vivo findings. METHODOLOGY: Bovine dental pulps were decellularized and then analysed using histological staining and DNA quantification. The resultant DDPs were characterized using immunohistochemical staining for the retention of vascular endothelial growth factor A (VEGF-A) and fibroblast growth factor 2 (FGF-2). Furthermore, DDPs were recellularized with hDPSCs and analysed histologically. The expression of markers involved in angiogenesis by hDPSCs colonizing the DDPs was assessed in vitro. A preliminary in vivo study was then conducted in which hDPSCs-seeded and unseeded DDPs were inserted in debrided human premolars root slices and implanted subcutaneously in immunodeficient mice. Samples were retrieved after 30 days and analysed using histological and immunohistochemical staining. The independent samples t-test, analysis of variance and a Kruskal-Wallis test were used to analyse the quantitative data statistically depending on the group numbers and normality of data distribution. The difference between the groups was considered significant when the P-value was less than 0.05. RESULTS: Acellular dental pulp matrices were generated following bovine dental pulp decellularization. Evaluation of the developed DDPs revealed a significant DNA reduction (P < 0.0001) with preservation of the native histoarchitecture and vasculature and retention of VEGF-A and FGF-2. Upon recellularization of the DDPs with hDPSCs, the in vitro analyses revealed cell engraftment with progressive repopulation of DDPs' matrices and vasculature and with enhanced expression of markers involved in angiogenesis. In vivo implantation of root slices with hDPSCs-seeded DDPs revealed apparent vascularization enhancement as compared to the unseeded DDP group (P < 0.0001). CONCLUSIONS: The developed decellularized dental pulp matrix had pro-angiogenic properties characterized by the retention of native vasculature and angiogenic growth factors. Seeding of hDPSCs into the DDP led to progressive repopulation of the vasculature, enhanced expression of markers involved in angiogenesis in hDPSCs and improved in vivo vascularization capacity. The se suggest that a combination of DDP and hDPSCs have the potential to provide a promising vascularization promoting strategy for dental pulp regeneration.

A biocompatible decellularized pulp scaffold for regenerative endodontics.

AIM: To investigate the feasibility of decellularizing the entire dental pulp using a mild treatment protocol to develop a decellularized biological extracellular matrix scaffold for use in regenerative endodontic procedures. METHODOLOGY: Decellularized human dental pulps were assessed using histological and immunohistochemical methods, scanning electron microscope and DNA quantification assay. Cytotoxicity assays to determine decellularized scaffold biocompatibility were also performed. Decellularized scaffolds were seeded with human dental pulp stem cells and cell viability assessed using Live/Dead® stain. Quantitative data were analysed statistically using Student's t-test and one-way analysis of variance to compare mean values between groups depending on group numbers. RESULTS: Assessment of decellularized tissues revealed an acellular matrix with preservation of native tissue histoarchitecture and composition. Decellularized tissues showed no evidence of cytotoxicity, with cell growth in direct contact with the scaffold and no reduction in cellular activity following extract incubation. Furthermore, the scaffold was able to support human dental pulp stem cell viability and attachment following recellularization. CONCLUSIONS: Promising results were observed in developing a decellularized biological scaffold derived from the dental pulp with the perseveration of extracellular structural components which are required for tissue-specific regeneration.

Molecular interface characterization in human bone matrix. I. Biochemical and IR spectroscopic studies.

The aim of this work is the characterization of interfaces in calcified tissues. In order to separate the non-collagenous bone proteins, according to their interaction with collagen or hydroxyapatite crystals, 10 sequential bone demineralizations using EDTA alone were carried out, followed by four sequential extractions using both EDTA and GuHCl. The extracts were characterized by SDS-PAGE, IR spectrum analysis, and kinetics of demineralization and proteins released. A great proportion of non-collagenous proteins are bound to the collagen matrix, many of which have a high affinity to it. This work demonstrates that collagen is not directly linked to the mineralized phase.

Disaster transfusion experience : Contribution to disaster planning

Disaster planning in a University Hospital such as the American University of Beirut Medical Center (AUBMC), imparts on the blood bank an its staff certain responsabilities which are geared to meet the transfusion needs of mass casualties in a relatively short period of time. The aim of this communications is to share the lessons learned from a situation encountered at AUBMC in 1975 and 1976, and in June to september 1982 when unpredictable and protracted disaster conditions forced the hospital to remain funtioning even though its organizational system of blood procurement and collection had broken down