Staale Petter Lyngstadaas

Emdogain--periodontal regeneration based on biomimicry.

Abstract Biomimicry has been introduced as a term for innovations inspired by nature [1]. Such innovations may appear in almost every part of modern society. This review on the effects of enamel matrix proteins on the formation of cementum and the development of emdogain for regeneration of periodontal tissues lost due to periodontitis shows an example of biomimicry in dentistry. Findings from clinical and laboratory investigations are summarized and the biological basis for enamel matrix-induced periodontal regeneration is discussed.

Analysing the optimal value for titanium implant roughness in bone attachment using a tensile test

This study aims at studying the effect of surface roughness on bone attachment of coin-shaped titanium implants. All implants in this study were blasted with TiO(2) particles of 180-220 microm, and then divided into three groups. One group had no further surface treatment whereas the other two groups were subsequently etched with hot hydrochloric acid (0.01M or 1M). The surface topography of the implant specimens was examined by SEM and by a confocal laser scanner for a numeric evaluation of S(a), S(t) and S(dr). The ranging implants in the three groups differed significantly in surface structure. The implants with modified surfaces were then placed into the tibias of 12 rabbits (n=16). After 8 weeks healing, the attachment of bone to implants were examined using a standardised tensile test analysis. The implants that were only blasted (positive control) showed significantly better functional attachment (p<0.001) than the acid etched. Implant surfaces etched with 1M HCl solution had the lowest retention in bone. There was a negative correlation between the increasing roughness and mechanical retention in bone of the implants in this study. The results support observations from earlier studies that suggested an optimal surface roughness for bone attachment, identified by in situ tensile tests and expressed as the arithmetic mean deviation (S(a)), to be in the range between 3.62 and 3.90 microm and that a further attachment depended on mechanical interlocking between bone and implant.

Cellular uptake of amelogenin, and its localization to CD63, and Lamp1-positive vesicles.

Abstract.Proteins of the developing enamel matrix include amelogenin, ameloblastin and enamelin. Of these three proteins amelogenin predominates. Protein-protein interactions are likely to occur at the ameloblast Tomes’ processes between membrane-bound proteins and secreted enamel matrix proteins. Such protein-protein interactions could be associated with cell signaling or endocytosis. CD63 and Lamp1 are ubiquitously expressed, are lysosomal integral membrane proteins, and localize to the plasma membrane. CD63 and Lamp1 interact with amelogenin in vitro. In this study our objective was to study the molecular events of intercellular trafficking of an exogenous source of amelogenin, and related this movement to the spatiotemporal expression of CD63 and Lamp1 using various cell lineages. Exogenously added amelogenin moves rapidly into the cell into established Lamp1-positive vesicles that subsequently localize to the perinuclear region. These data indicate a possible mechanism by which amelogenin, or degraded amelogenin peptides, are removed from the extracellular matrix during enamel formation and maturation.

Enamel Matrix Derivative Promotes Reparative Processes in the Dental Pulp

During odontogenesis, amelogenins from the preameloblasts are translocated to differentiating odontoblasts in the dental papilla, suggesting that amelogenins may be associated with odontoblast changes during development. In the present study, we have explored the effects of enamel matrix derivative (EMD) on the healing of a pulpal wound. Coronal pulp tissue of permanent maxillary premolars of miniature swine were exposed through buccal class V cavities. The exposed pulp was capped with EMD. The contralateral teeth served as controls and were capped with a calcium hydroxide paste (Dycal®). The cavities were sealed with glass-ionomer cement. After 2 and 4 weeks, the histology of the teeth was analyzed. In the EMD-treated teeth, large amounts of newly formed dentin-like hard tissue with associated formative cells outlined the pulpal wound separating the cavity area from the remaining pulp tissue. Inflammatory cells were present in the wound area but not subjacent to the newly formed hard tissue. Morphometric analysis showed that the amount of hard tissue formed in EMD-treated teeth was more than twice that of the calcium-hydroxide-treated control teeth (p < 0.001), suggesting that EMD is capable of promoting reparative processes in the wounded pulp more strongly than is calcium hydroxide.

In vivo performance of absorbable collagen sponges with rosuvastatin in critical-size cortical bone defects.

Rosuvastatin (RSV) is a synthetic statin with favourable pharmacologic properties, but its local effect in bone has yet to be investigated. The aim of this study was to evaluate the potential of absorbable collagen sponge (ACS) as a carrier for RSV to enhance bone formation in critical-size cortical bone defects adjacent to titanium implants. ACS, treated with different concentrations of RSV (R1 = 8.7 + or - 1.8 microg; R2 = 52.0 + or - 4.4 microg; R3 = 259.1 + or - 8.8 microg) or phosphate-buffered saline alone, were placed into the bone marrow through a defect made in the proximal tibial cortical bone of New Zealand White rabbits. One empty defect (SHAM) served as an internal control in each animal. After a healing time of 4 weeks, a concentration-dependent increase of alkaline phosphatase activity in ACS treated with RSV was detected in the bone fluid after removing the implants. In addition, a significant concentration-dependent increase in BMP-2 mRNA levels was found in the cortical bone tissue adjacent to the RSV-treated ACS. The cortical architecture of bone defects analysed by micro-computed tomography showed a trend towards higher bone volume in the ACS+R1 group compared with SHAM, which was accompanied by an increase in the bone mineral density. Evaluation of histological sections showed new bone formation in ACS treated with RSV but not in untreated ACS. These results indicate that RSV, when administered locally in bone, may have a potential effect in stimulating bone formation.

Ameloblastin promotes bone growth by enhancing proliferation of progenitor cells and by stimulating immunoregulators

In this study, we examined the role of the enamel matrix protein, ameloblastin, in bone growth and remodelling, and attempted to identify some of the molecular mechanisms involved in these processes. The effects of recombinant ameloblastin (rAmbn) were tested in vivo in rats, and in vitro in primary human mesenchymal stem cells, osteoblasts, chondrocytes, and osteoclasts. We used a microarray technique to identify genes that were regulated in human osteoblasts and verified our findings using multiplex protein analysis and real-time RT-PCR. Recombinant ameloblastin was found to stimulate bone healing in vivo, and to enhance the proliferation of mesenchymal stem cells and osteoblasts, as well as the differentiation of osteoclast precursor cells in vitro. The most profound effect was on the regulation of genes related to immune responses as well as on the expression of cytokines and markers of bone cell differentiation, indicating that ameloblastin has an effect on mesenchymal cell differentiation. A receptor has not yet been identified, but we found rAmbn to induce, directly and indirectly, signal transducer and activator of transcription (STAT) 1 and 2 and downstream factors in the interferon pathway.

Chemokines as markers of local inflammation and angiogenesis in patients with chronic subdural hematoma: a prospective study

ObjectiveThe goal of this study was to investigate the chemokines CCL2, CXCL8, CXCL9 and CXCL10 as markers of the inflammatory responses in chronic subdural hematoma (CSDH).MethodsSamples of peripheral venous blood and CSDH fluid (obtained during surgery) in 76 adult patients were prospectively analyzed. Chemokine values were assessed by a Multiplex antibody bead kit.ResultsWe found significantly higher levels of chemokines CCL2, CXCL8, CXCL9 and CXCL10 in hematoma fluid compared with serum.ConclusionsChemokines are elevated in the hematoma cavity of patients with CSDH. It is likely that these signaling modulators play an important role in promoting local inflammation. Furthermore, biological activity of CCL2 and CXCL8 may promote neovascularization within the outer CSDH membrane, and a compensatory angiostatic activity of CXCL9 and CXCL10 may contribute to repairing this disorder. This phenomenon was restricted to the hematoma site, and the systemic chemokine levels might not reflect local immune responses.

Porous titanium granules promote bone healing and growth in rabbit tibia peri-implant osseous defects

OBJECTIVES The aim of this study was to investigate the osteoconductive properties and biological performance of porous titanium granules used in osseous defects adjacent to titanium implants. MATERIAL AND METHODS In this animal experimental study, calibrated defects were prepared in the tibias of 24 New Zealand rabbits. The defects were randomized into two tests and one control group. The test defects were grafted with either metallic or oxidized porous titanium granules (PTG or WPTG, respectively), whereas control defects were left empty (sham). The defects were closed with a submerged coin shaped titanium implant. Defects were left for healing for 4 weeks. After healing, the implants were removed and the new bone tissue formed onto the implant surface was analyzed for run x 2, osteocalcin, collagen-I, tartrate-resistant acid phosphatase, H(+)-ATPase, tumor necrosis factor-alpha, interleukin (IL)-6 and IL-10 gene expression using reverse transcriptase polymerase chain reaction. Wound fluid from the healed defects was analyzed for lactate dehydrogenase and alkaline phosphatase activity. Finally osteoconductivity was analyzed by micro-computed tomography and histology. RESULTS Significantly more new bone formed in PTG and WPTG grafted defects compared with sham. The new bone grew both through the porosities of the granules and onto the implant surfaces. The WPTG group showed significantly less expression of key inflammation markers, but with no significant difference in a marker for necrosis. The WPTG also showed a significant increase in collagen-I mRNA expression compared with PTG. CONCLUSION The results suggest that PTG and WPTG are both osteoconductive materials that can be used to promote bone formation in osseous defects adjacent to titanium implants without hampering implant osseointegration.

Ameloblastin Fusion Protein Enhances Pulpal Healing and Dentin Formation in Porcine Teeth

Ameloblastin (Ambn, also named “amelin” or “sheathlin”) is a protein participating in enamel formation and mesenchymal-ectodermal interaction during early dentin formation in developing teeth. Experiments have demonstrated an association between Ambn expression and healing of acute pulp wounds. The purpose of this study was to investigate if local application of recombinant fusion Ambn (rAmbn) could influence reparative dentin formation in pulpotomized teeth. In this randomized, double-blinded study, pulpotomy was performed in 28 lower central incisors in 17 adult miniature pigs. Following the surgical procedure, the exposed pulp tissue was covered either with rAmbn or with calcium hydroxide. After 2, 4, or 8 weeks, the teeth were extracted and examined by histomorphometry and immunohistochemistry using antibodies against porcine ameloblastin, collagen type I, and dentin sialoprotein (DSP). In rAmbn-treated teeth, a substantial amount of newly formed reparative dentin was observed at the application site, completely bridging the pulpal wound. Dentin formation was also observed in calcium hydroxide-treated teeth; however, the amount of reparative dentin was significantly smaller (P < 0.001) than after rAmbn treatment. Immunohistochemistry confirmed that the new hard tissue formed was similar to dentin. This is the first time a direct link between ameloblastin and dentin formation has been made in vivo. The results suggest potential for rAmbn as a biologically active pulp-dressing agent for enhanced pulpal wound healing and reparative dentin formation after pulpotomy procedures.

Effect of enamel matrix derivative and of proline-rich synthetic peptides on the differentiation of human mesenchymal stem cells toward the osteogenic lineage.

With the aim of discovering new molecules for induction of bone formation and biomineralization, combination of bioinformatics and simulation methods were used to design the structure of artificial peptides based on proline-rich domains of enamel matrix proteins. In this study, the effect of such peptides on the differentiation toward the osteogenic lineage of human umbilical cord mesenchymal stem cells (hUCMSCs) was evaluated with or without osteogenic supplements (hydrocortisone, β-glycerol phosphate, and ascorbic acid) and compared to the effect of the commercially available enamel matrix derivative (EMD). It was hypothesized that the differentiation toward the osteogenic lineage of hUCMSCs would be promoted by the treatment with the synthetic peptides when combined with differentiation media, or it could even be directed exclusively by the synthetic peptides. Osteoinductivity was assessed by cell proliferation, bone morphogenetic protein-2 secretion, and gene expression of osteogenic markers after 1, 3, and 14 days of treatment. All peptides were safe with the dosages used, showing lower cell toxicity. P2, P4, and P6 reduced cell proliferation with growing media by 10%-15%. Higher expression of early osteoblast markers was found after 3 days of treatment with EMD in combination with osteogenic supplements, while after 14 days of treatment, cells treated by the different synthetic peptides in combination with osteogenic supplements showed higher osteocalcin mRNA levels. We can conclude that osteogenic differentiation of hUCMSCs is promoted by short-term EMD treatment in combination with osteogenic supplements and by long-term treatment by the synthetic peptides in combination with osteogenic supplements, showing similar results for all the peptide variants analyzed in this study.