Oliver Driemel

Somatic stem cells for regenerative dentistry

Complex human tissues harbour stem cells and/or precursor cells, which are responsible for tissue development or repair. Recently, dental tissues such as periodontal ligament (PDL), dental papilla or dental follicle have been identified as easily accessible sources of undifferentiated cells. The dental stem cell biology might provide meaningful insights into the development of dental tissues and cellular differentiation processes. Dental stem cells could also be feasible tools for dental tissue engineering. Constructing complex structures like a periodontium, which provides the functional connection between a tooth or an implant and the surrounding jaw, could effectively improve modern dentistry. Dental precursor cells are attractive for novel approaches to treat diseases like periodontitis, dental caries or to improve dental pulp healing and the regeneration of craniofacial bone and teeth. These cells are easily accessible and, in contrast to bone-marrow-derived mesenchymal stem cells, are more closely related to dental tissues. This review gives a short overview of stem cells of dental origin.

Overexpression of EGFR and absence of C-KIT expression correlate with poor prognosis in salivary gland carcinomas

Aims:  To evaluate the prognostic impact of expression of receptor tyrosine kinases epidermal growth factor receptor (EGFR), HER2, and C‐KIT in relation to established clinicopathological parameters in salivary gland carcinomas.

Comparison of human dental follicle cells (DFCs) and stem cells from human exfoliated deciduous teeth (SHED) after neural differentiation in vitro

Dental stem cells from human exfoliated deciduous teeth (SHED) and dental follicle cells (DFCs) are neural crest-derived stem cells from human dental tissues. Interestingly, SHED and DFCs can successfully differentiate into neuron-like cells. We hypothesized that SHED and DFCs have the same neural cell differentiation potentials. To evaluate neural cell differentiation, we cultivated SHED and DFCs in four different serum-replacement media (SRMs) and analyzed cell morphology, cell proliferation, and gene expression patterns before and after differentiation. In a standard cell culture medium, SHED and DFCs have not only similar cell morphologies, but they also have similar gene expression patterns for known stem cell markers. However, only SHED expressed the neural stem cell marker Pax6. After cultivation in SRMs, cell proliferations of DFCs and SHED were reduced and the cell morphology was spindle-like with long processes. However, differentiated DFCs and SHED had different neural cell marker expression patterns. For example, gene expression of the late neural cell marker microtubule-associated protein 2 was upregulated in DFCs and downregulated in SHED in SRM with the B27 supplement. In contrast, SHED formed neurosphere-like cell clusters in SRM with the B27 supplement, epidermal growth factor, and fibroblast growth factor-2. Moreover, SHED differentially expressed the glial cell marker glial fibrillary acidic protein, which in contrast was weakly or not expressed in DFCs. In conclusion, SHED and DFCs have different neural differentiation potentials under the same cell culture conditions.

A two-step strategy for neuronal differentiation in vitro of human dental follicle cells

Human dental follicle cells (DFCs) derived from wisdom teeth are precursor cells for cementoblasts. In this study, we recognized that naïve DFCs express constitutively the early neural cell marker beta-III-tubulin. Interestingly, DFCs formed beta-III-tubulin-positive neurosphere-like cell clusters (NLCCs) on low-attachment cell culture dishes in serum-replacement medium (SRM). For a detailed examination of the neural differentiation potential, DFCs were cultivated in different compositions of SRM containing supplements such as N2, B27, G5 and the neural stem cell supplement. Moreover, these cell culture media were combined with different cell culture substrates such as gelatin, laminin, poly-L-ornithine or poly-L-lysine. After cultivation in SRM, DFCs differentiated into cells with small cell bodies and long cellular extrusions. The expression of nestin, beta-III-tubulin, neuron-specific enolase (NSE) and neurofilament was up-regulated in SRM supplemented with G5, a cell culture supplement for glial cells, and the neural stem cell supplement. DFCs formed NLCCs and demonstrated an increased gene expression of neural cell markers beta-III-tubulin, NSE, nestin and for small neuron markers such as neuropeptides galanin (GAL) and tachykinin (TAC1) after cultivation on poly-L-lysine. For a further neural differentiation NLCC-derived cells were sub-cultivated on laminin and poly-L-ornithine cell culture substrate. After 2 weeks of differentiation, DFCs exposed neural-like cell morphology with small neurite-like cell extrusions. These cells differentially express neurofilament and NSE, but only low levels of beta-III-tubulin and nestin. In conclusion, we demonstrated the differentiation of human DFCs into neuron-like cells after a two-step strategy for neuronal differentiation.

A new biphasic osteoinductive calcium composite material with a negative Zeta potential for bone augmentation

The aim of the present study was to analyze the osteogenic potential of a biphasic calcium composite material (BCC) with a negative surface charge for maxillary sinus floor augmentation. In a 61 year old patient, the BCC material was used in a bilateral sinus floor augmentation procedure. Six months postoperative, a bone sample was taken from the augmented regions before two titanium implants were inserted at each side. We analyzed bone neoformation by histology, bone density by computed tomography, and measured the activity of voltage-activated calcium currents of osteoblasts and surface charge effects. Control orthopantomograms were carried out five months after implant insertion. The BCC was biocompatible and replaced by new mineralized bone after being resorbed completely. The material demonstrated a negative surface charge (negative Zeta potential) which was found to be favorable for bone regeneration and osseointegration of dental implants.

Gene expression profiles of dental follicle cells before and after osteogenic differentiation in vitro

Recently, osteogenic precursor cells were isolated from human dental follicles, which differentiate into cementoblast- or osteoblast-like cells under in vitro conditions after the induction with dexamethasone or insulin. However, mechanisms for osteogenic differentiation are not understood in detail. In a previous study, real-time RT-PCR results demonstrated molecular mechanisms in dental follicle cells (DFCs) during osteogenic differentiation that are different from those in bone-marrow-derived mesenchymal stem cells. We analysed gene expression profiles in DFCs before and after osteogenic differentiation with the Affymetrix GeneChip® Human Gene 1.0 ST Array. Transcripts of 98 genes were up-regulated after differentiation. These genes could be clustered into subcategories such as cell differentiation, cell morphogenesis, and skeletal development. Osteoblast-specific transcription factors like osterix and runx2 were constitutively expressed in differentiated DFCs. In contrast, the transcription factor ZBTB16, which promotes the osteoblastic differentiation of mesenchymal stem cells as an up-stream regulator of runx2, was differentially expressed after differentiation. Transcription factors NR4A3, KLF9 and TSC22D3, involved in the regulation of cellular development, were up-regulated as well. In conclusion, we present the first transcriptome of human DFCs before and after osteogenic differentiation. This study sheds new light on the complex mechanism of osteogenic differentiation in DFCs.

Maxillary Sinus Anatomy: A Cadaveric Study With Clinical Implications

This study measured maxillary sinus volume, evaluated the location of the semilunar hiatus in correlation to the nasal floor, and the incidence, location, and height of antral septa and discusses their clinical implications. Maxillary sinus volume was quantified in 65 cadavers (130 sinuses) by water application through the semilunar hiatus and measuring the used amount. The location of the semilunar hiatus was identified as distance from the nasal floor. The septa were counted, evaluated, and the size measured from the antral floor. The medium maxillary sinus volume was 12.5 mL (range, 5–22 mL). The medium location of the semilunar hiatus was 25.6 mm above the nasal floor (range, 18–35 mm). Thirty‐five septa were counted in 130 maxillary sinuses. This equals an incidence of 27%. The medium height of the septa was 5.4 mm (2.5–11 mm). The main location of the septa was the region of the first molar (29%), the second molar (23%), and the second premolar (23%). The height, location, and number of septa as well as the height of the semilunar hiatus and volume of the maxillary sinus have to be taken into consideration to correctly plan the procedure and amount of grafting material in maxillary sinus floor elevation operations. Anat Rec, 292:352–354, 2009.

Laminin-5 immunocytochemistry: a new tool for identifying dysplastic cells in oral brush biopsies

Background:  The brush biopsy technique is not only a seminal technique but also a critically discussed method for detection of oral pre‐cancerous stages and manifest carcinomas. The γ2 chain of laminin‐5 and its proteolytic fragments comprise an invasion factor for many carcinomas.

Proteomic analysis of osteogenic differentiation of dental follicle precursor cells.

Recently, there has been an increased interest in unravelling the molecular mechanisms and cellular pathways controlling the differentiation and proliferation of human stem cell lines. Proteome analysis has proven to be an effective approach to comprehensive analysis of the regulatory network of differentiation. In the present study we applied 2‐DE combined with capillary‐LC‐MS/MS analysis to profile differentially regulated proteins upon differentiation of dental follicle precursor cells (DFPCs). Out of 115 differentially regulated proteins, glutamine synthetase, lysosomal proteinase cathepsin B proteins, plastin 3 T‐isoform, beta‐actin, superoxide dismutases, and transgelin were found to be highly up‐regulated, whereas cofilin‐1, pro‐alpha 1 collagen, destrin, prolyl 4‐hydrolase and dihydrolipoamide dehydrogenase were found to be highly down‐regulated. The group of up‐regulated proteins is associated with actin‐bundling and defence against oxidative cellular stress, whereas down‐regulated proteins were associated with collagen biosynthesis. Bioinformatic analyses of the entire data set confirmed these findings that represent significant steps towards the understanding of DFPC differentiation. The bioinformatic analyses suggest that proteins associated with cell cycle progression and protein metabolism were down‐regulated and proteins involved in catabolism, cell motility and biological quality were up‐regulated. These results display the general physiological state of DFPCs before and after osteogenic differentiation. We also identified regulatory proteins, such as the transcription factors TP53 and Sp‐1, associated with the differentiation process. Further studies will investigate the impact of identified regulatory proteins for cell proliferation and osteogenic differentiation in DFPCs.

Survey of congenitally missing teeth in orthodontic patients in Eastern Bavaria.

This retrospective study examined the occurrence of congenitally missing permanent teeth and the need for dental treatment in the Regensburg University Medical Centre of Eastern Bavaria. Using a dental administration software tool, a total of 1442 patients who presented for orthodontic treatment between 1994 and 2006 were identified. After exclusion of 89 patients with incomplete records, 1353 subjects (635 males and 718 females) remained for analysis. Of these, 1130 had no missing permanent teeth, 52 had cleft lips, 110 had one to two teeth missing, 34 had three to five missing teeth, and 27 had greater than or equal to six missing teeth. The analyses focused on the type and number of missing teeth and on differences in the severity of dental agenesis according to gender and to referrals from various geographic regions around Regensburg. The data were statistically analysed using two-tailed tests. The following teeth were most frequently missing: tooth 35 (5.9 per cent), 45 (5.1 per cent), 22 (4.0 per cent), 12 (3.6 per cent), 15 (3.1 per cent), and 25 (3.0 per cent). No statistically significant difference in gender was found for one to two missing permanent teeth (low degree), hypo- or oligodontia (severe degree), or cleft lip. The odds ratio (OR) of presenting with hypo- or oligodontia compared with no missing teeth was higher among subjects originating from geographic regions outside Regensburg than from those from Regensburg, and it was statistically significantly higher for patients from Passau {OR = 3.53 [95% confidence interval (CI) = 1.18-10.52]} and Landshut [OR = 3.65 (95% CI = 1.22-10.99)]. The high prevalence and severe degree of dental agenesis of permanent teeth found in these groups of patients likely reflects distinct referral patterns for patients originating from geographic regions outside Regensburg. These data reinforce the need for a specialized dental treatment centre with the capacity to adequately serve a large rural area in Eastern Bavaria.