Petros D. Damoulis

Osteogenic Differentiation of Human Mesenchymal Bone Marrow Cells in Silk Scaffolds Is Regulated by Nitric Oxide

Abstract:  Bone marrow‐derived mesenchymal stem cells (BMSC) are a powerful tool for tissue engineering and can be used in the regeneration of bone and other tissues. Nitric oxide (NO) produced by the endothelial NO synthase (eNOS) plays an important role in bone development and healing. We hypothesized that NO plays a role in osteogenic differentiation of BMSC cultured in three‐dimensional silk scaffolds. eNOS protein was measured by Western Analysis and its activity was assessed by measuring nitrite in culture supernatants. Mineralization was evaluated through calcium deposition and the expression of genes associated with osteogenic differentiation (collagen I, RUNX2, and osteocalcin) was quantified using real‐time RT‐PCR. eNOS was consistently expressed with minor fluctuations, but NO production significantly increased at later time points (weeks 4 and 5). Addition of a competitive NOS inhibitor (L‐NAME) resulted in a modest decrease in calcium deposition, which became statistically significant in week 5. This was preceded by a dramatic decrease in RUNX2 and osteocalcin expression in week 4. These results support our hypothesis and implicate NO as an important player in bone tissue engineering.

Expression of MMP-13 (collagenase-3) in long-term cultures of human dental pulp cells

UNLABELLED Matrix metalloproteinase-13 (MMP-13 or collagenase-3) is a member of the family of matrix metalloproteinases (MMPs) produced in high amounts by cells with mineralising potential. Human dental pulp has been shown to express high levels of MMP-13 RNA. OBJECTIVE Since human dental pulp derived cells (HDPC) are known to possess osteoprogenitor properties, we investigated the pattern of expression of MMP-13 in long-term cultures of those cells under conditions that support mineralisation in vitro. DESIGN Impacted teeth or teeth extracted for orthodontic purposes were used to obtain dental pulp explants and HDPC were cultured for approximately 5 weeks. Pro- and active MMP-13 levels were determined in the cell culture supernatants by means of enzyme-linked immunosorbent assay (ELISA). Cell growth was evaluated through DNA content and osteogenic differentiation was assessed by alkaline phosphatase (ALP) activity and Alizarin Red staining. RESULTS Mineralising cultures of HDPC produced significantly higher levels of pro-MMP-13 compared to control cultures. Both pro- and active MMP-13 levels displayed a characteristic peak that was found to coincide with the peak in alkaline phosphatase activity and the onset of mineralisation. Once mineralisation was firmly established, MMP-13 expression was significantly reduced. CONCLUSIONS Evidence from this study suggests a role for MMP-13 in the transition of human dental pulp cells to a mature mineralising phenotype and points to MMP-13 as a possible marker in HDPC differentiation.

Desquamative gingivitis as a manifestation of chronic mucocutaneous disease.

Desquamative gingivitis (DG) is a clinical descriptive term indicating “peeling gums”. DG is usually the result of a disease process that causes separation of the epithelium from the underlying connective tissue in the oral masticatory mucosa. DG may be a manifestation of several mucocutaneous diseases, most commonly cicatricial pemphigoid, pemphigus vulgaris and lichen planus. Correct diagnosis of the underlying disease in DG patients requires careful clinical observation, detailed examination of medical history, biopsy and histopathological examination of the lesions as well as more specialized tests such as direct and indirect immunofluorescence. Treatment of DG consists of treating the underlying disease and often requires the use of immunosuppressive agents, such as corticosteroids. Elimination of local gingival irritants, such as dental plaque and calculus, can significantly improve the treatment outcome.

Severe Periodontitis in a Patient With Hyperoxaluria and Oxalosis: A Case Report and Review of the Literature

BACKGROUND Hyperoxaluria is a metabolic disease with excessive urinary oxalate excretion that can be primary or secondary. Hyperoxaluria can result in chronic renal disease and renal failure. Calcium oxalate crystals can be deposited in oral tissues, and the disease can be associated with severe periodontitis and tooth loss. METHODS The periodontal condition of a 38-year-old patient with a diagnosis of hyperoxaluria and end-stage renal disease is presented. The patients periodontal status was monitored over a period of several weeks, and extracted teeth were submitted for histopathologic evaluation. RESULTS The patient was diagnosed with generalized severe periodontitis and external root resorption. Initial periodontal treatment consisting of oral-hygiene instructions and scaling and root planing was performed. However, despite an initial decrease of soft tissue inflammation, the patients periodontal condition deteriorated, and eventually, all teeth had to be extracted. The deposition of calcium oxalate crystals in the periodontal tissues was confirmed histologically. CONCLUSIONS Long-standing hyperoxaluria can be associated with severe periodontitis and external root resorption resulting in tooth loss. The pathogenetic mechanisms of hard tissue destruction are still unclear.

Desquamative Gingivitis als Manifestation einer chronischen mukokutanen Erkrankung

Schlüsselwörter • bullöse Erkrankungen • desquamative Gingivitis • Lichen planus • Pemphigus vulgaris • vernarbendes Pemphigoid Zusammenfassung Die desquamative Gingivitis (DG) ist weniger eine Diagnose als ein klinischbeschreibender Begriff, der auf ein „sich schälendes Zahnfleisch“ (peeling gum) hinweist. In der Regel ist sie das Resultat eines pathologischen Prozesses in der mastikatorischen Schleimhaut, verursacht durch die Ablösung des Epithels von seinem darunterliegenden Bindegewebe. Mehrere unterschiedliche Schleimhauterkrankungen können sich unter dem klinischen Bild einer DG manifestieren. Zu den häufigsten Auslösern gehören das benigne vernarbende Schleimhautpemphigoid, der Pemphigus vulgaris und der Lichen planus. Eine zuverlässige Diagnose der zugrundeliegenden Erkrankung erfordert neben der sorgfältigen klinischen Beobachtung und einer detaillierten Kenntnis der medizinischen Vorgeschichte, eine Biopsie der Läsionen und deren histopathologische Untersuchung, wobei direkte und indirekte Immunfluoreszenztests helfen, die Diagnose zu sichern. Die Therapie der DG besteht in der Behandlung der Grunderkrankung und erfordert in der Regel den Einsatz von immunsupprimierenden Wirkstoffen wie z. B. Corticosteroide. Zahnhygienische Maßnahmen wie die Entfernung von Zahnbelag und Zahnstein können den Behandlungserfolg signifikant verbessern. Desquamative Gingivitis als Manifestation einer chronischen mukokutanen Erkrankung