Wei Zhou

The performance of bone marrow mesenchymal stem cell--implant complexes prepared by cell sheet engineering techniques.

This study investigated the hypothesis that cell sheets composed of multilayered rabbit bone marrow derived mesenchymal stem cells (MSC) could be assembled with two kinds of implants (surface-modified titanium and zirconia) for the construction of a MSC-implant. The MSC sheets were harvested from culture flasks, wrapped around implants to construct the complexes, and then cultured in osteogenic medium. The layered cell sheets integrated well with implants and remained viable, with small mineralized nodules visible on the implant surfaces for up to four weeks after culture. Cells on the implants underwent classical in vitro osteogenic differentiation with an associated elevation of alkaline phosphatase activity and bone- and vascular-related protein expression. In vivo, two kinds of cell sheet-implant complexes were transplanted under the skin of SCID mice and cultured for eight weeks. For the MSC sheet titanium implant complex, histological examination revealed that new bone tissue that formed around implants followed a predominantly endochondral pathway, exhibiting histological markers of native bone; for the MSC sheet zirconia implant complex, however, intramembranous ossification appeared to occur on the surface of the zirconia implant, as observed with typical osteocytes embedded in dense matrix and accompanied by both microvessels and marrow cavities. These findings demonstrate that MSC-implants possessing osteogenic and vascularization abilities can be produced using cell sheet engineering techniques in conjunction with routine implant materials, which provide a novel technology to modify the implant surface.

Periapical Follicle Stem Cell: A Promising Candidate for Cementum/Periodontal Ligament Regeneration and Bio-Root Engineering

Mesenchymal stem cell (MSC)-mediated tissue regeneration offers opportunities to regenerate a bio-root and its associated periodontal tissues to restore tooth loss. Previously, we proved that the apical end of developing root was acting as a promising candidate cell source for root/periodontal tissue (R/PT) regeneration. In the present study, we investigated the properties of periapical follicle stem cells (PAFSCs) isolated from the apical end of developing root of human third molars at the root-developing stage and evaluated the potential application of these cells for cementum/periodontal ligament (PDL) regeneration and bio-root engineering. Putative PAFSCs were isolated and subcultured until 20th passage. Cell characteristics of PAFSCs at early or late passage were evaluated and compared with periodontal ligament stem cells (PDLSCs) via a series of histological, cellular, and molecular analyses. PAFSCs at early passage presented crucial stem cell properties and showed a higher proliferation rate than PDLSCs in vitro. Meanwhile, PAFSCs also showed the tissue-regenerative capacity to produce a typical cementum/PDL-like complex in vivo. During long-term passage, both cell populations changed in morphology and gradually lost their stem cell properties. The alkaline phosphatase (ALP) activity and expression of mineralization-related genes markedly declined as more passages were carried out, which might lead to the loss of tissue-regenerative capacity of these 2 groups of cells in vivo. Our findings suggest that developing tissue-derived PAFSCs are a distinctive cell population from PDLSCs and might be a promising candidate for bio-root engineering.

Development of mesenchymal stem cell-implant complexes by cultured cells sheet enhances osseointegration in type 2 diabetic rat model

This study investigated the hypothesis that a mesenchymal stem cells (MSC)-implant complex could be used in type 2 diabetic rats. Diabetes was modeled with type 2 diabetic rats induced by high fat diet with low dose streptozotocin (STZ) injected intraperitoneally. MSC sheets were harvested from culture flasks, wrapped around implants to construct the complexes, and then cultured in an osteogenic medium. The layered cell sheets integrated well with the implants and remained viable, with small mineralized nodules visible on the implant surfaces after culturing. The MSC-implant complexes were inserted into the right tibiae of the diabetic rats. Titanium implants served as controls. After four and eight weeks of healing, the tibiae were observed via MicroCT and harvested for histological examination. For the MSC-implant complexes, MicroCT analysis showed that bone volume ratio and trabecular thickness increased significantly (p<0.05), and trabecular separation decreased significantly (p<0.05) compared to the titanium implants in diabetic rats. Histological examination revealed a greater amount of new bone tissue forming around the MSC-implant complexes and a higher bone implant contact (BIC) rate than the titanium implants. These findings demonstrate that MSC-implant complexes possess osteogenic abilities and can be used in diabetic rats to improve the BIC rate. Thus, MSC-implant complexes provide a novel tissue engineering approach that promotes osseous healing and may potentially be useful in the treatment of diabetic patients.

Sustained release of insulin-like growth factor-1 from poly(lactide-co-glycolide) microspheres improves osseointegration of dental implants in type 2 diabetic rats

Dental implantation is an effective and predictable treatment modality for replacing missing teeth and repairing maxillofacial defects. However, implants in patients with type 2 diabetes mellitus are likely to have a high failure rate and poor initial osseointegration. In the current study, we established an effective drug delivery system designed to improve osseointegration of dental implants in an animal model of type 2 diabetes. Twenty type 2 diabetic rats were divided into two groups: a group receiving recombinant rat Insulin-like Growth Factor 1 (rrIGF-1) Microsphere Therapy (MST) (10 rats) and a control group (10 rats). The rrIGF-1 was encapsulated into poly(lactide-co-glycolide) (PLGA) microspheres to produce a sustained-release effect around titanium (Ti) dental implants in the rrIGF-1 MST group. Scanning electron microscopy, confocal laser scanning microscopy, and cumulative-release studies were conducted to verify the release effect of the microspheres as well as rrIGF-1 bioactivity. Five rats from each group were sacrificed at weeks 4 and 8 post surgery, and a histological analysis was performed on the rats from both groups. Compared to the control group, rats that received rrIGF-1 by PLGA microsphere treatment were observed to have a higher bone-implant contact percentage around the Ti implants at week 4 or week 8 post surgery (P<0.05). This result clearly indicates that sustained release of rrIGF-1 through encapsulation by PLGA microspheres positively affects osseointegration of dental implants in type 2 diabetic rats.

Endodontic treatment of teeth induces retrograde peri-implantitis

OBJECTIVES Some cases of retrograde peri-implantitis arise from adjacent natural teeth that have peri-radicular infection. The present study was designed to investigate the incidence of retrograde peri-implantitis from adjacent teeth with endodontic treatment. MATERIALS AND METHODS One hundred and twenty-eight patients of ages ranging from of 24-61 years were recruited for this study. A total of 128 ITI SLA implants with adjacent teeth that had received endodontic treatment at least 1 week before were placed in 128 patients. The date of endodontic therapy and the pulp status of the adjacent tooth before endodontic therapy were recorded. The distance between the implant and the adjacent tooth was determined using a radiograph. The stability of all implants was tested by OSSTELL and recorded at implant placement, after 4 and 12 weeks. RESULTS The incidence of retrograde peri-implantitis was 7.8%. The duration from endodontic-treated adjacent teeth to implant placement was 12.15+/-10.1 weeks, and the distance between the implant and the adjacent teeth was 2.99+/-1.4 mm. Distance and time were found to be related to retrograde peri-implantitis (P<0.05). The stability of implants with retrograde peri-implantitis was less than that of the normal implants, but the difference was not significant (P>0.05). CONCLUSIONS The incidence of retrograde peri-implantitis may reduce by increasing the distance between the implant and adjacent tooth, and/or the duration from endodontically treated adjacent tooth-to-implant placement. Although preliminary, these data might orient the practitioner to avoid retrograde peri-implantitis.

Effects of local delivery of bFGF from PLGA microspheres on osseointegration around implants in diabetic rats.

OBJECTIVE Diabetes mellitus may impair bone healing after dental implant placement. The objective of this study was to evaluate the effects of the local delivery of basic fibroblast growth factor (bFGF) from poly(lactide-co-glycolide) (PLGA) microspheres on osseointegration around titanium implants in diabetic rats. STUDY DESIGN The bFGF-PLGA microspheres were prepared by the W/O/W double-emulsion solvent evaporation method. A total of 20 rats were used to create diabetic animal models by giving them a high-fat and high-sugar diet and a low-dose streptozotocin intraperitoneal injection. Titanium implants were planted into the tibias of the diabetic rats and into 10 normal rats. Microspheres were loaded on the surfaces of the implants in the bFGF intervention group before they were placed into the rats. After 4 or 8 weeks, the tibias containing the implants were removed and embedded with resin. Uncalcified tissue slices were prepared to compare osseointegration. RESULTS At 4 weeks, the bone-implant contact rate in the diabetic control group was less than that in the control group and the bFGF intervention group (P < .05). At 8 weeks, the results among the 3 groups were similar to those at 4 weeks. CONCLUSIONS The local delivery of bFGF from PLGA microspheres into areas around titanium implants may improve osseointegration in diabetic rats.

Is the osseointegration of immediately and delayed loaded implants the same?—comparison of the implant stability during a 3-month healing period in a prospective study

OBJECTIVES The objectives of the present study were (1) to compare the stability of delayed loaded (DL) and immediately loaded (IL) ITI SLA implants during the first 3 months of the healing period using resonance frequency analysis (RFA) and (2) to determine the factors that affect implant stability during the healing period. MATERIALS AND METHODS To compare implant stability, RFA was performed on two groups of patients (12 patients received 25 IL implants and 47 patients received 79 DL implants) with a total 104 ITI SLA implants. Implant stability was measured directly by RFA at implant placement and consecutively once a week for 12 weeks. Statistical analyses were carried out to study implant stability differences between IL and DL groups. RESULTS One of the 25 implants in the IL group failed, and no implant was lost in the DL group. Implant stability between the IL and DL groups showed a statistically significant difference (P<0.05). The mean implant stability quotient of all measured implants from implant insertion to 12 weeks was 72.88 +/- 5.39 for the DL and 75.86 +/- 3.60 for the IL types. The lowest stability was at 4 weeks for DL implants (mean: 71.58 +/- 5.11) and 2 weeks for IL implants (mean: 71.33 +/- 2.97). In both groups, bone types I and II showed higher implant stability than bone type III (P<0.05). CONCLUSIONS The findings of this study indicate that differences in osseointegration between IL and DL implants may be predicted according to differential implant stability.

Advanced biomaterials and their potential applications in the treatment of periodontal disease

Abstract Periodontal disease is considered as a widespread infectious disease and the most common cause of tooth loss in adults. Attempts for developing periodontal disease treatment strategies, including drug delivery and regeneration approaches, provide a useful experimental model for the evaluation of future periodontal therapies. Recently, emerging advanced biomaterials including hydrogels, films, micro/nanofibers and particles, hold great potential to be utilized as cell/drug carriers for local drug delivery and biomimetic scaffolds for future regeneration therapies. In this review, first, we describe the pathogenesis of periodontal disease, including plaque formation, immune response and inflammatory reactions caused by bacteria. Second, periodontal therapy and an overview of current biomaterials in periodontal regenerative medicine have been discussed. Third, the roles of state-of-the-art biomaterials, including hydrogels, films, micro/nanofibers and micro/nanoparticles, developed for periodontal disease treatment and periodontal tissue regeneration, and their fabrication methods, have been presented. Finally, biological properties, including biocompatibility, biodegradability and immunogenicity of the biomaterials, together with their current applications strategies are given. Conclusive remarks and future perspectives for such advanced biomaterials are discussed.

Cell Sheets of Co-cultured Endothelial Progenitor Cells and Mesenchymal Stromal Cells Promote Osseointegration in Irradiated Rat Bone

Irradiated bone has a greater risk of implant failure than nonirradiated bone. The purpose of this study was to investigate the influence of cell sheets composed of co-cultured bone marrow mesenchymal stromal cells (BMSCs) and endothelial progenitor cells (EPCs) on implant osseointegration in irradiated bone. Cell sheets (EPCs, BMSCs or co-cultured EPCs and BMSCs) were wrapped around titanium implants to make cell sheet-implant complexes. The co-cultured group showed the highest osteogenic differentiation potential in vitro, as indicated by the extracellular matrix mineralization and the expression of osteogenesis related genes at both mRNA and protein levels. The co-cultured cells promoted ectopic bone formation as indicated by micro-computed tomography (Micro-CT) and histological analysis. In the irradiated tibias of rats, implants of the co-cultured group showed enhanced osseointegration by Micro-CT evaluation and histological observation. Co-cultured EPCs and BMSCs also up-regulated the expression of osteogenesis related genes in bone fragments in close contact with implants. In conclusion, cell sheets of co-cultured EPCs and BMSCs could promote osseous healing around implants and are potentially useful to improve osseointegration process for patients after radiotherapy.

Increased fibroblast functionality on CNN2-loaded titania nanotubes

Infection and epithelial downgrowth are major problems associated with maxillofacial percutaneous implants. These complications are mainly due to the improper closure of the implant–skin interface. Therefore, designing a percutaneous implant that better promotes the formation of a stable soft tissue biologic seal around percutaneous sites is highly desirable. Additionally, the fibroblast has been proven to play an important role in the formation of biologic seals. In this study, titania nanotubes were filled with 11.2 kDa C-terminal CCN2 (connective tissue growth factor) fragment, which could exert full CCN2 activity to increase the biological functionality of fibroblasts. This drug delivery system was fabricated on a titanium implant surface. CCN2 was loaded into anodized titania nanotubes using a simplified lyophilization method and the loading efficiency was approximately 80%. Then, the release kinetics of CCN2 from these nanotubes was investigated. Furthermore, the influence of CCN2-loaded titania nanotubes on fibroblast functionality was examined. The results revealed increased fibroblast adhesion at 0.25, 0.5, 1, 2, 4, and 24 hours, increased fibroblast viability over the course of 5 days, as well as enhanced actin cytoskeleton organization on CCN2-loaded titania nanotubes surfaces compared to uncoated, unmodified counterparts. Therefore, the results from this in vitro study demonstrate that CCN2-loaded titania nanotubes have the ability to increase fibroblast functionality and should be further studied as a method of promoting the formation of a stable soft tissue biologic seal around percutaneous sites.