Recruitment of bone marrow-derived cells to the periodontal ligament via the stromal cell-derived factor-1/C-X-C chemokine receptor type 4 axis

BACKGROUND/OBJECTIVES

The periodontal ligament (PDL) is a non-mineralized connective tissue that exists between the alveolar bone and root surface cementum and plays important roles in tooth function. The PDL harbors a remarkable reserve of multipotent stem cells, which maintain various types of cells. However, the sources of these stem cells, other than their developmental origin, are not well understood.

MATERIAL AND METHODS

To elucidate the recruitment of bone marrow (BM)-derived stem cells in the PDL, green fluorescent protein (GFP)-expressing BM-derived cells were transplanted into the femoral BM of immunodeficient rats, and the distribution and expression of stem cell markers in the PDL were analyzed in vivo. To evaluate the functional significance of BM-derived cells to the PDL, tooth replantation was performed and the expression of stromal cell-derived factor (SDF)-1, a critical chemotactic signal for mesenchymal stem cell recruitment, was analyzed. To confirm the SDF-1-dependency of BM-derived cell migration to the PDL, PDL-conditioned medium (CM) was prepared, and BM-derived cell migration was analyzed using a transwell culture system.

RESULTS

Four weeks after cell transplantation, GFP-positive cells were detected in the PDL, and some of them were also positive for stem cell markers (i.e., CD29, SSEA4, and αSMA). Seven days after tooth replantation, the number of GFP- and SDF-1-positive cells significantly increased in PDL. Concurrently, the concentration of SDF-1 and the number of colony-forming units of fibroblasts in peripheral blood were increased. BM-derived cell migration increased in PDL-CM and was inhibited by an inhibitor of C-X-C chemokine receptor type 4 (CXCR4), an SDF-1 receptor.

CONCLUSION

These results indicate that stem cells and their progeny in PDL are not only derived from their developmental origin but are also supplied from the BM via the blood as the need arises. Moreover, this BM-derived cell recruitment appears to be regulated, at least partially, by the SDF-1/CXCR4 axis.

Topography Influences Adherent Cell Regulation of Osteoclastogenesis

The importance of osteoclast-mediated bone resorption in the process of osseointegration has not been widely considered. In this study, cell culture was used to investigate the hypothesis that the function of implant-adherent bone marrow stromal cells (BMSCs) in osteoclastogenesis is influenced by surface topography. BMSCs isolated from femur and tibia of Sprague-Dawley rats were seeded onto 3 types of titanium surfaces (smooth, micro, and nano) and a control surface (tissue culture plastic) with or without osteogenic supplements. After 3 to 14 d, conditioned medium (CM) was collected. Subsequently, rat bone marrow-derived macrophages (BMMs) were cultured in media supplemented with soluble receptor activator of NF-κB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) as well as BMSC CM from each of the 4 surfaces. Gene expression levels of soluble RANKL, osteoprotegerin, tumor necrosis factor α, and M-CSF in cultured BMSCs at different time points were measured by real-time polymerase chain reaction. The number of differentiated osteoclastic cells was determined after tartrate-resistant acid phosphatase staining. Analysis of variance and t test were used for statistical analysis. The expression of prominent osteoclast-promoting factors tumor necrosis factor α and M-CSF was increased by BMSCs cultured on both micro- and nanoscale titanium topographies (P < 0.01). BMSC CM contained a heat-labile factor that increased BMMs osteoclastogenesis. CM from both micro- and nanoscale surface-adherent BMSCs increased the osteoclast number (P < 0.01). Difference in surface topography altered BMSC phenotype and influenced BMM osteoclastogenesis. Local signaling by implant-adherent cells at the implant-bone interface may indirectly control osteoclastogenesis and bone accrual around endosseous implants.

Staff recruitment, development and global mobility

This paper considers issues that relate to staff recruitment, staff development and global mobility of dental academics. Published literature, which has a North American bias, is reviewed. Recommendations, which may be applicable world-wide, are made to address evident and pertinent areas of concern in terms of the availability of quality dental teaching staff in dental teaching institutions so as to sustain the global dental academic enterprise at appropriately high levels of achievement.

Transcriptional regulation involving the intronic heat shock element of the rat hsp27 gene

While sequencing the first intron of the rat heat shock protein 27 gene (hsp27), we identified a consensus heat shock regulatory element (HSE). This intronic HSE (i-HSE) is conserved among mammalian hsp27 genes. The aim of this study was to investigate possible effects of this intronic HSE (i-HSE) on transcription from the rat hsp27 promoter. Gel mobility shift assays indicated that the i-HSE bound heat shock transcription factor 1 (HSF1) in a manner equivalent to that of HSE present in hsp27 promoter (p-HSE). The effect of i-HSE on transcription from the hsp27 promoter was evaluated using reporter constructs transiently transfected in the osteosarcoma cell line ROS17/2.8. When inserted 5' to a 145 bp fragment of the hsp27 promoter not containing p-HSE, a 215 bp fragment of hsp27 intron 1 containing i-HSE enhanced CAT activity and conferred heat shock-inducible activity to the construct. This intronic fragment containing i-HSE also enhanced CAT activity in either normal or heat-shocked culture conditions when inserted 3' to the CAT open reading frame. However, in chimeric reporter constructs with a 273 bp hsp27 promoter containing p-HSE directly 5' to CAT reporter, and with a 215 bp fragment containing i-HSE inserted 3' to the CAT open reading frame, transcription from hsp27 promoter was reduced under normal and heat-stressed culture conditions. Mutation of the i-HSE reversed this effect. Further study is required to define the mechanism by which the i-HSE-containing region of the hsp27 promoter may mediate negative regulation of hsp27 transcription.

[Investigation of metal allergy to constituent elements of intraoral restoration materials]

Allergies caused by metals have been increasing. The number of patients visiting dentists with the chief complaint of metal allergy has also been increasing. From March 1994 to February 1997, 263 patients who complained of various symptoms visited our allergy clinic. Among them, 184 patients were suspected to have allergy caused by metals in dental restoration materials and were referred to the patch test. Among 165 patients', 128 were positives for metal allergy. Constituent elements of intraoral metals were analyzed in 107 of these 128 positive patients. The findings were as follows: 1. The most common five elements acting on the patients were Hg, Co, Ni, Cr, and Pd. 2. The most frequently used elements of dental restoration metal materials were Zn, Ag, Cu, Au, and Pd, and the alloy was Au-Ag-Pd alloy. 3. The highest tendency of coincidence between allergen and intraoral metals were observed among Co-Cr-Ni alloys and Pd, Ni, and Cr elements. 4. In case of palmoplantar pustulosis, allergen metals tended to be the same as intraoral metal elements.

Modification of the Abbé flap for reconstruction of the vermilion tubercle and Cupid's bow in cleft lip patients

PURPOSE

This article reports on the modification of the Abbé flap for correction of mild tightness of the corrected cleft lip deformity.

PATIENTS AND METHODS

Twelve patients with a moderately tight lip deformity, from 16 to 35 years old, underwent this procedure. Nine had a unilateral deformity and 3 a bilateral deformity. The flap, which was taken from the central portion of the lower lip vermilion, was designed to repair the vermilion tubercle and the Cupid's bow. A tiny portion of skin was included to facilitate closure of the donor site. It was inserted into the center of the upper lip and the pedicle was divided 1 week after operation.

RESULTS

Each patient showed a more natural contour of the vermilion tubercle and the Cupid's bow. The scarring of the donor site was inconspicuous.

CONCLUSIONS

Use of modified Abbé flap to reconstruct the contour of the vermilion tubercle and the Cupid's bow makes the upper lip look more natural.

Correlative microscopic investigation of the interface between titanium alloy and the osteoblast-osteoblast matrix using mineralizing cultures of primary fetal bovine mandibular osteoblasts

In this study, the primary culture of bovine mandibular osteoblast cells in a microculture assay has been used to further investigate the interaction of mineralizing osteoblast cultures with implant surfaces by using correlative microscopic techniques. Rapid differentiation and mineralization of osteoblast cultures grown on titanium alloy surfaces was observed. The successful short-term culture of mineralizing mandibular osteoblasts on titanium alloy surfaces occurred without the formation of a tenacious adhesive interface between the alloplastic material and the multilayered cell culture.

Correction of the cleft nasal deformity with an L-shaped iliac bone graft

We describe our technique for correcting a cleft lip nasal deformity using L-shaped iliac bone grafts to achieve additional structural support and the desired nasal projection and profile. Augmenting the nasal bridge creates the illusion of a narrower nose. Further, the columellar portion of the L-shaped graft provides stabilization, eliminating the "see-saw" effect of the bridge graft on the fulcrum of the bony bridge, which can lead to a depressed tip and loss of the root indentation. Clinical and radiographic observation has revealed that this method of correction has consistently produced satisfactory results.

Differential estrogenic regulation of small M(r) heat shock protein expression in osteoblasts

Polymerase chain reaction amplification and sequencing of heat shock protein (HSP) 27-related transcripts present in cDNAs generated from heat-shocked osteoblast RNA revealed the expression of three related open reading frames that encode proteins of 208, 197, or 175 amino acids. Their expression as recombinant proteins in Escherichia coli demonstrated that they encode 27,000, 25,000, or 22,000 M(r) proteins. Northern blot analysis of heat shock protein 27-related transcript expression revealed that, while HSP 27 expression (850-nucleotide transcript) was induced by heat shock alone, the expression of a smaller transcript was facilitated by estrogen treatment prior to heat shock. This corresponded with the co-induction of 18,000 and 22,000 M(r) proteins by estrogen-pretreated, heat-shocked osteoblasts as revealed by fluorography. The identification of these multiple small M(r) heat shock-induced proteins demonstrated that the stress response of mammalian cells is composed of multiple, related proteins whose expression is differentially regulated. The importance of estrogen-regulation of the small M(r) heat shock protein component of the stress response may be of particular significance to osteoblast physiology.

Isolation and characterization of a rat HSP 27 gene

A gene encoding the rat heat shock protein 27 protein was isolated and characterized. The gene is composed of three exons and two introns. The proximal 5' untranslated region of this gene contains consensus heat shock elements, multiple SP1 sites, and basal regulatory elements including a CCAAT box and a TATA box. Comparison of this heat shock gene with the murine heat shock protein 25 and human heat shock protein 27 genes revealed the conserved presence of a putative heat shock element in the first intron of these mammalian small M(r) heat shock protein genes. While preliminary expression studies indicate the promoter directs heat shock induced expression of heat shock protein 27, the functional significance of the intronic heat shock element to the expression of this gene remains to be determined.

[Histological investigation of improvement of mandibular atrophy for application of hydroxyapatite dental implant]

The purpose of this study was to investigate the possibility of applying the hydroxyapatite dental implant to the atrophic mandible after alveolar ridge augmentation using hydroxyapatite granules. The lower P3, P4 and M1 of 3 mongrel dogs were extracted. At 30 weeks, alveolar ridge augmentation was performed with porous hydroxyapatite granules. Sixteen weeks later, hydroxyapatite dental implants were applied to the area. And 4 weeks later, the specimens were taken out and fixed by 10% formalin alcohol. They were embedded in polyester resin and prepared into undecalcified sections. And the sections were stained with toluidine blue to observe the surrounding tissue of the dental implants histologically under light microscopy.

RESULTS

1) Bone formation was seen in most part of the intergranular spaces. However, in the buccal area, there were some spaces in which bone formation was entirely not observed. 2) At 4 weeks after implantation, almost all of the surface of the hydroxyapatite dental implants was attached to the surrounding osseous tissues. But in some parts of the implant surface, especially the buccal, fibrous connective tissue was seen. 3) These results provide a basis for the technique of hydroxyapatite dental implantation with porous hydroxyapatite granules in the atrophic mandibles after alveolar ridge augmentation.