Constantinus Politis

Angiogenic Properties of Human Dental Pulp Stem Cells

Angiogenesis, the formation of capillaries from pre-existing blood vessels, is a key process in tissue engineering. If blood supply cannot be established rapidly, there is insufficient oxygen and nutrient transport and necrosis of the implanted tissue will occur. Recent studies indicate that the human dental pulp contains precursor cells, named dental pulp stem cells (hDPSC) that show self-renewal and multilineage differentiation capacity. Since these cells can be easily isolated, cultured and cryopreserved, they represent an attractive stem cell source for tissue engineering. Until now, only little is known about the angiogenic abilities and mechanisms of the hDPSC. In this study, the angiogenic profile of both cell lysates and conditioned medium of hDPSC was determined by means of an antibody array. Numerous pro-and anti-angiogenic factors such as vascular endothelial growth factor (VEGF), monocyte chemotactic protein-1 (MCP-1), plasminogen activator inhibitor-1 (PAI-1) and endostatin were found both at the mRNA and protein level. hDPSC had no influence on the proliferation of the human microvascular endothelial cells (HMEC-1), but were able to significantly induce HMEC-1 migration in vitro. Addition of the PI3K-inhibitor LY294002 and the MEK-inhibitor U0126 to the HMEC-1 inhibited this effect, suggesting that both Akt and ERK pathways are involved in hDPSC-mediated HMEC-1 migration. Antibodies against VEGF also abolished the chemotactic actions of hDPSC. Furthermore, in the chicken chorioallantoic membrane (CAM) assay, hDPSC were able to significantly induce blood vessel formation. In conclusion, hDPSC have the ability to induce angiogenesis, meaning that this stem cell population has a great clinical potential, not only for tissue engineering but also for the treatment of chronic wounds, stroke and myocardial infarctions.

Pro-angiogenic impact of dental stem cells in vitro and in vivo.

Within the field of dental tissue engineering, the establishment of adequate tissue vascularization is one of the most important burdens to overcome. As vascular access within the tooth is restricted by the apical foramen, it is of major importance to implement effective vascularization strategies in order to recreate viable components of teeth and periodontal tissues. However, while the current regenerative approaches focus on the use of dental stem cells (DSCs), little is known about these cells and their ability to promote angiogenesis. Therefore, the present study aimed to elucidate the paracrine angiogenic properties of postnatal DSCs, in particular dental pulp stem cells (DPSCs), stem cells from the apical papilla (SCAPs) and dental follicle precursor cells (FSCs). An antibody array, together with RT-PCR and ELISA, pointed out the differential expression of pro-angiogenic as well as anti-angiogenic factors by cultured DSCs and human gingival fibroblasts (HGF-1). Despite the secretion of proliferation-promoting factors, DSCs caused no notable increase in the proliferation of human microvascular endothelial cells (HMEC-1). With regard to other aspects of the angiogenic cascade, DPSCs, SCAPs and HGF-1 significantly promoted endothelial migration in a transwell migration assay. DPSCs also had a pronounced effect on endothelial tubulogenesis, as was shown by an in vitro Matrigel™ assay. In the last part of this study, a chorioallantoic membrane assay demonstrated a sustained pro-angiogenic impact of DPSCs and SCAPs in an in vivo setting. Collectively, these data indicate a predominant pro-angiogenic influence of DPSCs and SCAPS in vitro and in vivo in comparison to FSCs, suggesting that both stem cell populations could potentially promote the vascularization of regenerated dental tissues.

Anaesthesia of the inferior alveolar and lingual nerves following subcondylar fractures of the mandible

A retrospective chart review of 387 patients with condylar and subcondylar fractures revealed 2 cases of inferior alveolar nerve (IAN) and lingual nerve (LN) anaesthesia following the subcondylar fracture. Only 5 cases have been reported previously. The mechanism of action remains unknown but a review of the literature and an analysis of 120 dry human skulls supported the hypothesis that compression of the mandibular nerve at a high level, close to the foramen ovale, could cause anaesthesia. This complication is rare, because it requires compression at a particular angle. The antero-median angulation of the condyle must be close to the foramen ovale, and the fracture must be a unilaterally displaced fracture. The presence of an enlarged lateral pterygoid plate appeared to enhance the risk of compression. The IAN and LN anaesthesia could be resolved after open reduction of the fracture and IAN and LN anaesthesia constitute a strict indication for an early open fracture reduction.

BLOODLOSS AND TRANSFUSION NEED IN ORTHOGNATHIC SURGERY: REVIEW OF LITERATURE

1 OMFS-IMPATH Research Group, Department of Imaging and Pathology, Faculty of Medicine, Katholieke Universiteit Leuven, Leuven, Belgium and Department of Oral and Maxillofacial Surgery, University Hospitals Leuven, BE-3000 Leuven, Belgium Faculty of Medicine, Hasselt University, Diepenbeek, Belgium; Biomedical Research Institute, Laboratory of Morphology, Hasselt University, Campus Diepenbeek, BE-3590 Diepenbeek, Belgium

Implantaten en hun succes na bestraling

Patienten die bestraald werden in het hoofd-halsgebied, hebben vaak baat bij dentale implantaten. Implantaten die geplaatst worden in bestraalde kaken lopen echter een groter risico dat ze verloren gaan dan in niet-bestraalde kaken. Bot dat bestraald wordt, ondergaat veranderingen die in de kaken van invloed kunnen zijn op de osseo-integratie van implantaten. Naast deze veranderingen, kunnen andere factoren leiden tot meer implantaatverlies in bestraalde kaken. Enkele factoren die hierbij een rol zouden kunnen spelen zijn de bestralingsdosis en -zone, de tijd tussen bestraling en implantatie, de locatie waar de implantaten worden geplaatst en hyperbare zuurstoftherapie. In de literatuur bestaat echter over al deze factoren nog veel discussie, evenals over het succespercentage van implantaten in bestraalde kaken. Voor de algemeen practicus is het voornamelijk van belang deze patienten op de hoogte te brengen van de bestraling als compromitterende factor en de mogelijke risico’s die eraan verbonden zijn. Aanbevolen wordt de patient te verwijzen naar een gespecialiseerd medisch centrum, zoals de afdeling Mond- kaak- en aangezichtschirurgie van een ziekenhuis. Daar beschikt men over de nodige ervaring en kan men de mogelijkheid tot implantaatplaatsing en de risico’s die eraan verbonden kunnen zijn, het best beoordelen.