Agata Czajka-Jakubowska

The stimulation of adipose-derived stem cell differentiation and mineralization by ordered rod-like fluorapatite coatings

In this study, the effect of ordered rod-like FA coatings of metal discs on adipose-derived stem cell (ASC)s growth, differentiation and mineralization was studied in vitro; and their mineral inductive effects in vivo. After 3 and 7 days, the cell number on the metal surfaces was significantly higher than those on the ordered and disordered FA surfaces. However, after 4 weeks much greater amounts of mineral formation was induced on the two FA surfaces with and even without osteogenesis induction. The osteogenic profiles showed the up regulation of a set of pro-osteogenic transcripts and bone mineralization phenotypic markers when the ASCs were grown on FA surfaces compared to metal surfaces at 7 and 21 days. In addition to BMP and TGFβ signaling pathways, EGF and FGF pathways also appeared to be involved in ASC differentiation and mineralization. In vivo studies showed accelerated and enhanced mineralized tissue formation integrated within ordered FA coatings. After 5 weeks, over 80% of the ordered FA coating was integrated with a mineralized tissue layer covering the implants. Both the intrinsic properties of the FA crystals and the topography of the FA coating appeared to dominate the cell differentiation and mineralization process.

Adhesion and growth of dental pulp stem cells on enamel-like fluorapatite surfaces

UNLABELLED To study how apatite crystal alignment of an enamel-like substrate affects DPSC cellular adhesion and growth as a precursor to produce an in vitro enamel/dentin superstructure for future studies. The cells were subcultured in 10% FBS DMEM up to seven weeks on the two surfaces. Specimens were observed under SEM, counted, and analyzed using the human pathway-focused matrix and adhesion PCR array. After three days, the cell number on ordered FA surface was significantly higher than on the disordered surface. Of the 84 focused pathway genes, a total of 20 genes were either up or down regulated in the cells on ordered FA surface compared to the disordered surface. More interestingly, of the cell-matrix adhesion molecules, integrin alpha 7 and 8 (ITGA 7 and 8), integrin beta 3 and 4 (ITGB3 and 4), and the vitronectin receptor-integrin alpha V (ITGAV) and the key adhesion protein-fibronectin1 (FN1) were up-regulated. In SEM, both surfaces showed good biocompatibility and supported long term growth of DPSC cells but with functional cell-matrix interaction on the ordered FA surfaces. SIGNIFICANCE The enhanced cellular response of DPSC cell to the ordered FA crystal surface involves a set of delicately regulated matrix and adhesion molecules which could be manipulated by treating the cells with a dentin extract, to produce a dentin/enamel superstructure.

Fluorapatite-modified Scaffold on Dental Pulp Stem Cell Mineralization

In previous studies, fluorapatite (FA) crystal-coated surfaces have been shown to stimulate the differentiation and mineralization of human dental pulp stem cells (DPSCs) in two-dimensional cell culture. However, whether the FA surface can recapitulate these properties in three-dimensional culture is still unknown. This study examined the differences in behavior of human DPSCs cultured on electrospun polycaprolactone (PCL) NanoECM nanofibers with or without the FA crystals. Under near-physiologic conditions, the FA crystals were synthesized on the PCL nanofiber scaffolds. The FA crystals were evenly distributed on the scaffolds. DPSCs were cultured on the PCL+FA or the PCL scaffolds for up to 28 days. Scanning electron microscope images showed that DPSCs attached well to both scaffolds after the initial seeding. However, it appeared that more multicellular aggregates formed on the PCL+FA scaffolds. After 14 days, the cell proliferation on the PCL+FA was slower than that on the PCL-only scaffolds. Interestingly, even without any induction of mineralization, from day 7, the upregulation of several pro-osteogenic molecules (dmp1, dspp, runx2, ocn, spp1, col1a1) was detected in cells seeded on the PCL+FA scaffolds. A significant increase in alkaline phosphatase activity was also seen on FA-coated scaffolds compared with the PCL-only scaffolds at days 14 and 21. At the protein level, osteocalcin expression was induced only in the DPSCs on the PCL+FA surfaces at day 21 and then significantly enhanced at day 28. A similar pattern was observed in those specimens stained with Alizarin red and Von Kossa after 21 and 28 days. These data suggest that the incorporation of FA crystals within the three-dimensional PCL nanofiber scaffolds provided a favorable extracellular matrix microenvironment for the growth, differentiation, and mineralization of human DPSCs. This FA-modified PCL nanofiber scaffold shows promising potential for future bone, dental, and orthopedic regenerative applications.

VEGF promotes osteogenic differentiation of ASCs on ordered fluorapatite surfaces

Vascular endothelial growth factor (VEGF) has been reported to mediate both osteogenesis and angiogenesis in bone regeneration. We previously found an upregulation of VEGF in adipose-derived stem cells (ASCs) when obvious mineralization occurred on a novel fluorapatite (FA)-coated surfaces. This study investigated the effect of FA and VEGF on the growth, differentiation and mineralization of (ASC) grown on ordered FA surfaces. Cells grown on FA and treated with VEGF demonstrated osteogenic differentiation as measured with ALP staining, and obvious mineralization as measured by Alizarin red staining. A combined stimulating effect of FA and VEGF was seen using both indicators. VEGF signaling pathway perturbation using a specific VEGF receptor inhibitor showed the lowest levels of ALP and Alizarin red staining, which was partially rescued when the cells were grown on FA and/or treated with the addition of VEGF. The osteogenic differentiation of ASCs stimulated by these FA surfaces as well as VEGF has been shown to be mediated through, but probably not only, the VEGF signaling pathway. The enhancement of osteogenic differentiation and mineralization supports the potential use of therapeutic VEGF and FA coatings in bone regeneration.

Maxillary sinuses and midface in patients with cleidocranial dysostosis

The cleidocranial dysplasia is general skeletal disorder with an autosomal dominant inheritance. It is manifested by many craniofacial abnormalities, of which the maxillary hypoplasia is the most evident. The aim of the study was to use CBCT to evaluate the volume of the maxillary sinuses and the dimensions of maxillae in patients with CCD and compare them with healthy individuals. Files of four children with cleidocranial dysplasia were investigated. Volume of every maxillary sinus as well as two dimensional measurements of distances between particular points of interest located on surface of maxilla were calculated from reconstructed CBCT examination. Data were compared with a control group. Statistical analysis was performed. Linear and volumetric data obtained using CBCT was collected and compared with a control group. All affected children had both maxillary sinus volume and maxillary dimensions smaller than control values. The maxillary sinuses were underdeveloped up to half of normal values. The largest differences were recorded in vertical linear dimensions of the maxillae. Horizontal dimensions were also lower. There are morphological modifications of bone tissue which accompany CCD. It seems that these changes occur on the midfacial region and to a greater extent concern the maxillary sinus volume.

Enamel crystals of mice susceptible or resistant to dental fluorosis: an AFM study

Objective This study aimed to assess the overall apatite crystals profile in the enamel matrix of mice susceptible (A/J strain) or resistant (129P3/J strain) to dental fluorosis through analyses by atomic force microscopy (AFM). Material and Methods Samples from the enamel matrix in the early stages of secretion and maturation were obtained from the incisors of mice from both strains. All detectable traces of matrix protein were removed from the samples by a sequential extraction procedure. The purified crystals (n=13 per strain) were analyzed qualitatively in the AFM. Surface roughness profile (Ra) was measured. Results The mean (±SD) Ra of the crystals of A/J strain (0.58±0.15 nm) was lower than the one found for the 129P3/J strain (0.66±0.21 nm) but the difference did not reach statistical significance (t=1.187, p=0.247). Crystals of the 129P3/J strain (70.42±6.79 nm) were found to be significantly narrower (t=4.013, p=0.0013) than the same parameter measured for the A/J strain (90.42±15.86 nm). Conclusion Enamel crystals of the 129P3/J strain are narrower, which is indicative of slower crystal growth and could interfere in the occurrence of dental fluorosis.

The Association between Maxillary Sinus Dimensions and Midface Parameters during Human Postnatal Growth

Objective The aim of the study based on CT images was to assess the age-related changes in maxillary sinus diameters in relation to diameters of the facial skeleton. Materials and Methods The retrospective analysis of CT images of the head of 170 patients aged 0–18 years (85 females and 85 males) was performed. Specific orientation points (zy, zm, pr, ns, n, and P) were identified in every patient and the following distances were measured: zy-zy, maximum facial width; zm-zm, midfacial width; n-pr, upper facial height; ns-pr, alveolar facial height; and ns-P, distance not indicated in craniometry. Results The maxillary sinuses of every patient were bilaterally measured in three planes. Three diameters were obtained: maximum transverse (horizontal) diameter called MSW, maximum vertical diameter called MSH, and maximum anteroposterior diameter (length) called MSL. In females, the correlation of MSW, MSH, and MSL and zy-zy, as well as n-pr distances, is very strong. Moreover, the significant correlation was found between all measurements of maxillary sinus and ns-pr as well as ns-P distances in females. The correlation between MSL and all measurements of midface as well as MSH and MSW and all measurements except ns-P is stronger in females than in males. In males, all measurements of maxillary sinus correlate with ns-P distance very strongly. Conclusions The statistical analysis (correlation and determination coefficient) showed that all measurements of maxillary sinuses correlate with midface dimensions.

Future Possibilities for Managing Dental Enamel Defects: Recent and Current Research Approaches

The cause of an enamel defect can be genetic, systemic, local, and/or induced. The repair of these defects spans the fields from gene therapy to invasive or noninvasive conventional restorative therapies. No matter how disfiguring some of the genetic and systemic conditions are, it is unlikely that the modern techniques of genetic and tissue engineering will be used in the near future to repair or prevent these enamel defects. Clinicians will have to rely on more conventional invasive, minimally invasive, and noninvasive techniques to treat this problem. This chapter describes some new and novel techniques which are in use and/or development for the repair of enamel defects. They include: growing enamel crystals on dental substrates, penetration of carious lesions with self-assembling molecules which encourage mineral formation, infiltrating carious lesions with resins, a paint on “enamel” using a self-etch resin, and an “enamel” crystal containing flexible laminate – a tooth “Band-Aid.”

Future Directions for the Treatment of Dentin Hypersensitivity

There are over 30 different treatments for sensitive dentin on the market today which suggests that not one of them gives the immediate and lasting relief from this condition desired by the patient. In this chapter we describe several, emerging, novel experimental technologies that may, in the future, offer such relief. These technologies include: a synthetic “glue” resembling the adhesive that adheres mollusks to rocks in the ocean; a self-etch resin filled with fluorhydroxyapatite (FA) crystrals; and a flexible laminate of Eudragit filled with the FA srystals. Finally the incorporation of dendrimers (artificial proteins) functionalized with anti-inflammatories and anti-microbials to control inflammation beneath sensitive dentin and, overtime, help the pulp repair.