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PubMed2004

[In vivo and in vitro bone regeneration from cord blood derived mesenchymal stem cells].

BACKGROUND: Mesenchymal stem cells with an osteoblastic differentiating potency are investigated in regard of probable tissue engineering for further clinical application. The following report describes the use of cord blood derived stem cells as an alternative to other stem cell populations for bone regenerating tissue engineering. METHODS: To demonstrate the multipotency of cord blood derived mesenchymal stem cells, unrestringated somatic stem cells (USSC) were isolated from cord blood and underwent an osteo-, chondro- and adipoblastic in vitro stimulation. To evaluate the osteoinductive potency of a porcine collagen I/III cell carrier USSC were incubated on this matrix. To investigate the in vivo effects of human USSC an athymic rat model was developed. These cells were transplanted into a femoral defect. RESULTS: Cord blood derived mesenchymal stem cells (USSC) have an in vitro multipotency and show adipo-, chondro- and osteogenic differentiation. The porcine collagen I/III carrier promoted an osteoblastic differentiation. USSC survived after xenotransplantation in an athymic rat and differentiated into osteoblasts filling the bony defect zone. CONCLUSION: Human USSC are a mesenchymal multipotent stem cell population that shows osteoblastic differentiation onto a collagen I/III carrier in vitro as well as in an athymic rat in vivo.

Adipocytes↗
PubMed2006

Effect of pulsed electromagnetic fields on maturation of regenerate bone in a rabbit limb lengthening model.

To study the effect of applying pulsed electromagnetic fields (PEMF) during the consolidation phase of limb lengthening, a mid-tibial osteotomy was performed in 18 adult New Zealand White rabbits and an external fixator was applied anteromedially. Animals were randomly assigned to treatment and control groups. After a 7-day latency period, the tibiae were distracted 0.5 mm every 12 h for 10 days. The treatment group received a 20-day course of PEMF for 60 min daily, coinciding with initiation of the consolidation phase. The control group received sham PEMF. Radiographs were performed weekly after distraction. Animals were euthanized 3 weeks after the end of distraction. Radiographic analysis revealed no significant difference in regenerate callus area between treatment and control tibiae immediately after distraction, at 1 week, 2 weeks, or 3 weeks after distraction ( p = 0.71, 0.22, 0.44, and 0.50, respectively). There was also no significant difference in percent callus mineralization ( p = 0.96, 0.69, 0.99, and 0.99, respectively). There was no significant difference between groups with respect to structural stiffness ( p = 0.80) or maximal torque to failure ( p = 0.62). However, there was a significant positive difference in mineral apposition rate between groups during the interval 1-2 weeks post-distraction ( p < 0.05). This difference was no longer evident by the interval 2-3 weeks post-distraction. While PEMF applied during the consolidation phase of limb lengthening did not appear to have a positive effect on bone regenerate, it increased osteoblastic activity in the cortical bone adjacent to the distraction site. Since the same PEMF signal was reported to be beneficial in the rabbit distraction osteogenesis when applied during distraction phase and consolidation phase, application of PEMF in the early phase may be more effective. Further work is necessary to determine optimal timing of the PEMF stimulation during distraction osteogenesis.

Animals↗
PubMed2003

Fabrication of polymer root form scaffolds to be utilized for alveolar bone regeneration.

Engineering dental tissues and organs is primarily motivated by a clinical need to restore these lost or diseased structures, in contrast to the use of harvested tissue. The present work focused on designing and characterizing scaffolds suitable for cultivation and implantation into the fresh extraction sockets of teeth, for the purpose of alveolar bone regeneration at a rate and quality higher than that of normal tissue healing for subsequent treatment with dental implants. Three-dimensional hollow root form scaffolds were prepared from poly-L-lactic acid/polyglycolic acid composites (50/50, 65/35, and 75/25 ratios), using the solvent casting compression molding particulate leaching technique. Two different salt particle sizes were used, 150-180 and 180-300 microm, to effect porogenesis. The scaffolds were characterized in vitro and in vivo. The highest percent porosity recorded was 75% with interconnectivity shown by scanning electron microscopy. The scaffolds demonstrated viscoelastic behavior and average strain in response to both static and dynamic forces that were suitable for them under bite-force magnitude anteriorly. The degradation of the root scaffolds depended on composite type, and on salt particle size. Tissue reaction favored samples made with large salt particle size.

Animals↗
PubMed2004

Statistical approaches in the analysis of gene expression data derived from bone regeneration specific cDNA microarrays.

Recent advances in molecular biology (e.g., cDNA microarray technology) enables the simultaneous monitoring of the expression level of thousands of genes. Due to the massive amount of complex data generated, sophisticated statistical approaches are necessary in order to properly address the experimental investigation. In this paper, we present statistical analysis of cDNA microarray data derived from bone regeneration experiments. Several interesting features from these data distinguish it from commonly used microarray experiment (i.e., separate hybridization of mRNA samples from reference and experimental tissues, selectively spotted cDNA sequences and 1060 systematically selected blank spots included in each array). Using this data set, we propose new methods for bioinformatic data normalization, as well as the modification and application of various other published methods in order to identify co-regulated gene expression patterns during the healing of a bone fracture. The proposed normalization methods perform effectively to eliminate the variations with a simple algorithm. Results from our cluster analysis revealed several clusters having distinct gene expression patterns during fracture healing. Our simulation study supports the reliability of the proposed methods.

Adenosylmethionine Decarboxylase↗
PubMedDate not supplied

Counting of platelet derived growth factor and transforming growth factor-beta in platelet-rich-plasma used in jaw bone regeneration.

AIM: Growth factors (GFs) as platelet derived growth factor (PDGF) and transforming growth factor (TGF-beta), found in platelet beta-granules also present in platelet-rich-plasma (PRP), accelerate bone revascularization and regeneration and for this reason they have been employed successfully in dental and maxillofacial surgery. Platelet concentrate is commonly used for this purpose as long as platelet release reaction and the consequent GFs loss are avoided. To reduce this phenomenon we set up an easy and fast procedure for preparing a satisfying clotted PRP by adding CaCl2 only (no exogenous thrombin). METHODS: ELISA essay has been used to measure PDGF and TGF-beta in plasma, platelets and serum and platelet GMP-140, with the cytofluorometric technique in order to quantify the degranulation entity. RESULTS: In the 13 examined patients receiving clotted PRP to enhance bone regeneration in post-extractive alveolar sockets, PRP showed no sign of platelet activation (degranulation) and short recalcification times (8-12 min). The autologous clotted PRPs specimen have been evaluated in laboratory in terms of GFs percent: 76% of initial GFs content could be recovered in clotted PRP. This result confirms the absence of platelet degranulation in our procedure. CONCLUSIONS: Significant clinical results in alveolar bone regeneration are reached only with a high percentage of GFs inserted in bone matrix, avoiding early platelet degranulation.

Adult↗
PubMed2004

[Guided bone regeneration beneath titanium foils].

The aim of this study was to examine the clinical and histological bony healing process beneath titanium foils used for guided tissue regeneration as well as of the Frios Algipore graft which was applied with autologous bone. 66 sinus floor elevations were carried out and examined over a period of three years and eight months. A success rate of 64% was recorded with foil incorporation. Complications occurred in form of primary and secondary disturbances in the healing process caused by exposure of the foil. 12 of the 66 foils had to be removed early. In all but one case, the augmented bone material was macroscopically well integrated despite the loss of the foil. Primary stability of the inserted dental implants into the ossified augmented site after operations of the sinus maxillaris was reached in all cases with absence of post-operative complications, and in 94% when there was postoperative exposure of the membrane. Histologically, a thin layer of connective tissue poor in cells but rich in collagen fibers appeared underneath the titanium foil. This was followed by newly-formed bony tissue transforming into osseous lamella parallel to the membrane underneath the new periost. In 65 out of 66 cases a sufficient amount of stable bone was built up locally suggesting good bio-compatibility and barrier function. Further, the foil also provided mechanical rest and supporting function for the space underneath. However, the occurrence of healing complications in 36% of the cases showed a need to improve on the titanium foils.

Bone Regeneration↗
PubMed1993

Expanded polytetrafluoroethylene membranes and connective tissue grafts support bone regeneration for closing mandibular Class II furcations.

Twenty-four mandibular buccal Class II furcation lesions in 12 subjects were treated with reconstructive periodontal therapy including citric acid root treatment and replaced flap surgery. Twelve (12) of the lesions received expanded polytetrafluoroethylene (ePTFE) membranes to cover the furcation entrance (ePTFE group) whereas the remaining 12 lesions received a connective tissue graft over the furcation (CTG group). Clinical assessments, including probing depth, probing attachment level, location of gingival margin, direct bone probing, and defect volume, were taken at baseline and at 12 months reentry. In the ePTFE group 30% of the defect volume filled with bone; 36% of the defects exhibited complete bone closure. In the CTG group 19% of the defect volume filled with bone and 18% of these defects exhibited complete bone closure. There were no meaningful clinical differences between treatment groups except in horizontal probing depth change (P < or = 0.05). This study suggests that connective tissue grafts and ePTFE membranes have comparable potential in supporting bone regeneration in mandibular Class II furcation lesions. Further clinical trials with larger numbers of patients and a longer evaluation period are needed to fully compare these procedures.

Adult↗
PubMed1977

A stimulator of stem cell proliferation in regenerating bone marrow.

A factor, capable of stimulating resting haemopoietic stem cells into DNA-synthesis has been extracted from regenerating bone marrow. It has a molecular weight in the range of 30.000-50.000 daltons and is not detectable in normal bone marrow. Used in combination with a stem cell proliferation inhibitor, previously described, it will restimulate proliferation in stem cells initially stopped by the inhibitor. Conversely, stimulation produced by this factor can be reversed by the addition of inhibitor. It is concluded that stem cell proliferation is controlled by an appropriate balance of endogenously produced stimulatory and inhibitory factors.

Animals↗
PubMed1999

Bone regeneration in the edentulous ridge expansion technique: histologic and ultrastructural study of 20 clinical cases.

The edentulous ridge expansion (ERE) technique is a partial-thickness flap procedure for implant surgery that was developed in 1986. The ERE technique permits the use of osseointegrated implants at sites whose minimal orofacial dimensions are insufficient for traditional implant surgery. The present work is a histologic and ultrastructural study of hard tissue repair modalities at edentulous sites that were treated with the ERE technique in 20 humans. Biopsies were obtained from the tissue regenerating within the surgically created bone gap between the mobile buccal and nonmobile lingual or palatal bone-periosteum plates ("bone flaps") on days 40, 90, 120, 150, and 480 (day 0 = day of implant insertion). The results suggest that osteoblasts differentiate from preexisting mesenchymal cells located on the original fissure walls, with consequent deposition of new bone in the surgically created intrabony defect.

Adult↗