A clinical study of alveolar bone tissue engineering with cultured autogenous periosteal cells: coordinated activation of bone formation and resorption

The next generation of regenerative dentistry: From tooth development biology to periodontal tissue, dental pulp, and whole tooth reconstruction in the clinical setting

In modern dentistry, prosthetic approaches such as implants and dentures have been developed as symptomatic solutions for tooth loss. However, the complete regeneration of teeth and periodontal tissue, an ultimate aspiration of humanity, remains unachieved. Recent advancements in fundamental scientific technologies, including single-cell RNA sequencing and spatial transcriptomics, have significantly advanced our molecular understanding of tooth development, paving the way toward achieving this goal. This review summarizes the fundamental processes of tooth development in humans and mice, recent findings from basic research, and current clinical applications in dental regenerative medicine, including periodontal, alveolar bone, and dental pulp regeneration using cellular approaches. Building on accumulated scientific knowledge, the complete regeneration of teeth and periodontal tissues may be achievable in the near future. We discuss the potential of emerging approaches, such as organoids derived from pluripotent stem cells and xenotransplantation using genetically modified animals, to transform dental medicine. These innovative concepts and integrated technologies hold the promise of enabling the regeneration of fully functional teeth and periodontal tissues.

An Exploration of the Role of Osteoclast Lineage Cells in Bone Tissue Engineering

Bone defects because of age, trauma, and surgery, which are exacerbated by medication side effects and common diseases such as osteoporosis, diabetes, and rheumatoid arthritis, are a problem of epidemic scale. The present clinical standard for treating these defects includes autografts and allografts. Although both treatments can promote robust regenerative outcomes, they fail to strike a desirable balance of availability, side effect profile, consistent regenerative efficacy, and affordability. This difficulty has contributed to the rise of bone tissue engineering (BTE) as a potential avenue through which enhanced bone regeneration could be delivered. BTE is founded upon a paradigm of using biomaterials, bioactive factors, osteoblast lineage cells (ObLCs), and vascularization to cue deficient bone tissue into a state of regeneration. Despite promising preclinical results, BTE has had modest success in being translated into the clinical setting. One barrier has been the simplicity of its paradigm relative to the complexity of biological bone. Therefore, this paradigm must be critically examined and expanded to better account for this complexity. One potential avenue for this is a more detailed consideration of osteoclast lineage cells (OcLCs). Although these cells ostensibly oppose ObLCs and bone regeneration through their resorptive functions, a myriad of investigations have shed light on their potential to influence bone equilibrium in more complex ways through their interactions with both ObLCs and bone matrix. Most BTE research has not systematically evaluated their influence. Yet contrary to expectations associated with the paradigm, a selection of BTE investigations has demonstrated that this influence can enhance bone regeneration in certain contexts. In addition, much work has elucidated the role of many controllable scaffold parameters in both inhibiting and stimulating the activity of OcLCs in parallel to bone regeneration. Therefore, this review aims to detail and explore the implications of OcLCs in BTE and how they can be leveraged to improve upon the existing BTE paradigm.

Osteogenic mesenchymal stem cells/progenitors in the periodontium

Periodontitis is the major cause of tooth loss in adults and is mainly characterized by alveolar bone destruction. Elucidating the mesenchymal stem cell (MSC)/progenitor populations of alveolar bone formation will provide valuable insights into regenerative approaches to clinical practice, such as endogenous regeneration and stem-cell-based tissue engineering therapies. Classically, MSCs residing in the bone marrow, periosteum, periodontal ligament (PDL), and even the gingiva are considered to be osteogenic progenitors. Furthermore, the contributions of MSCs expressing specific markers, including Gli1, Axin2, PTHrP, LepR, and α-SMA, to alveolar bone formation have been studied using cell lineage tracing and gene knockout models. In this review, we describe the MSCs/progenitors of alveolar bone and the biological properties of different subpopulations of MSCs involved in alveolar bone development, remodeling, injury repair, and regeneration.

Stem Cells in the Periodontium-Anatomically Related Yet Physiologically Diverse

Periodontitis is a complex chronic disease discernible by the deterioration of periodontal tissue. The goal of periodontal therapy is to achieve complete tissue regeneration, and one of the most promising treatment options is to harness the regenerative potential of stem cells available within the periodontal complex. Periodontal ligament stem cells, gingival mesenchymal stem cells, oral periosteal stem cells, and dental follicle stem cells have structural similarities, but their immunological responses and features differ. The qualities of diverse periodontal stem cells, their immune-modulatory effects, and variances in their phenotypes and characteristics will be discussed in this review. Although there is evidence on each stem cell population in the periodontium, understanding the differences in markers expressed, the various research conducted so far on their regenerative potential, will help in understanding which stem cell population will be a better candidate for tissue engineering. The possibility of selecting the most amenable stem cell population for optimal periodontal regeneration and the development and current application of superior tissue engineering treatment options such as autologous transplantation, three-dimensional bioengineered scaffolds, dental stem cell-derived extracellular vesicles will be explored.

Potential of Oral Cavity Stem Cells for Bone Regeneration: A Scoping Review

Bone loss is a common problem that ranges from small defects to large defects after trauma, surgery, or congenital malformations. The oral cavity is a rich source of mesenchymal stromal cells (MSCs). Researchers have documented their isolation and studied their osteogenic potential. Therefore, the objective of this review was to analyze and compare the potential of MSCs from the oral cavity for use in bone regeneration.

METHODS

A scoping review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. The databases reviewed were PubMed, SCOPUS, Scientific Electronic Library Online (SciELO), and Web of Science. Studies using stem cells from the oral cavity to promote bone regeneration were included.

RESULTS

A total of 726 studies were found, of which 27 were selected. The MSCs used to repair bone defects were (I) dental pulp stem cells of permanent teeth, (II) stem cells derived from inflamed dental pulp, (III) stem cells from exfoliated deciduous teeth, (IV) periodontal ligament stem cells, (V) cultured autogenous periosteal cells, (VI) buccal fat pad-derived cells, and (VII) autologous bone-derived mesenchymal stem cells. Stem cells associate with scaffolds to facilitate insertion into the bone defect and to enhance bone regeneration. The biological risk and morbidity of the MSC-grafted site were minimal. Successful bone formation after MSC grafting has been shown for small defects with stem cells from the periodontal ligament and dental pulp as well as larger defects with stem cells from the periosteum, bone, and buccal fat pad.

CONCLUSIONS

Stem cells of maxillofacial origin are a promising alternative to treat small and large craniofacial bone defects; however, an additional scaffold complement is required for stem cell delivery.

Regenerative Potential of Granulation Tissue in Periodontitis: A Systematic Review and Meta-analysis

Methods

Electronic searches were conducted in five databases including CENTRAL, MEDLINE, EMBASE, Web of Science, and Dentistry & Oral Sciences Source using a combination of MeSH terms and keywords up to 21 June 2022. Human studies including patients aged over 18 years with all forms of periodontitis were included. Following the risk of bias assessment, both qualitative and quantitative analyses were performed.

Results

A total of twelve studies were included in qualitative analysis and six of them in quantitative analyses. The evidence suggested that cells derived from periodontitis granulation tissue have osteogenic, adipogenic, chondrogenic, neurogenic, and angiogenic differentiation abilities as well as immunoregulatory properties. In particular, CD44⁺, CD73⁺, CD90⁺, CD105⁺, and CD146⁺ cells were found widely in granulation tissue whilst the only meta-analysis confirmed that CD90⁺ cells were present in lower numbers within the granulation tissue when compared with healthy periodontal tissue (WMD = -23.43%, 95% CI -30.43 to -16.44, p < 0.00001).

Conclusions

This review provided further evidence that granulation tissue from patients with periodontitis can be a potential stem cell source for regenerative therapy.

Non-destructive, spectrophotometric analysis of the thickness of the cell-multilayered periosteal sheet

Background

Autologous tissue-engineered periosteal sheets, which have been clinically applied for periodontal regeneration, sinus lift, and alveolar ridge augmentation, are enriched with osteoblast precursor cells and the abundant deposition of collagen type I in the extracellular spaces. Their quality is inspected prior to clinical use; however, most criteria cannot be evaluated without sacrificing samples. To reduce such losses, we developed a non-destructive optical method that can quantitatively evaluate the thickness of the periosteal sheet.

Methods

Dispersed periosteal cells were inoculated into small pieces of collagen sponge (Terudermis®) and plated into 60-mm dishes for further explant culture using a conventional medium and a stem-cell culture medium. The thickness of periosteal sheets was evaluated using inverted microscopic, histological, labeling (CellVue®)-based imaging and spectrophotometric (Spectro-1®) methods.

Results

The three-dimensional growth of periosteal sheets did not necessarily correlate with two-dimensional growth. The periosteal sheet prepared with the stem-cell medium formed cell multilayers, a phenomenon that could be observed qualitatively by inverted microscopy. The spectrophotometric analysis enabled the quantitative evaluation of the thickness of the cell multilayer without sacrificing the samples processed for scheduled cell therapy.

Conclusions

The growth of periosteal sheets is influenced by several major factors, including the basic quality of the individual original periosteal tissue segments, the technical expertise of doctors and operators involved in tissue harvesting and processing, and culture conditions. This newly developed spectrophotometric analysis can quantify the thickness of cell-multilayered periosteal sheets for quality assurance in a non-destructive manner, thereby contributing to better bone augmentation prior to implant therapy.

HGF/MET in osteogenic differentiation of primary human palatal periosteum-derived mesenchymal stem cells

PURPOSE

This study aimed to determine expressions of hepatocyte growth factor (HGF) and MET proto-oncogene receptor tyrosine kinase (MET) in palatal periosteum (PP) and to examine the effect of HGF/MET on osteogenic differentiation of human palatal periosteum-derived mesenchymal stem cells (PD-MSCs).

METHODS

HGF/MET proteins in human palatal periosteum (n = 3) were localized using immunohistochemistry. PD-MSCs (n = 3) were cultured in serum-free Essential 8 (E8) medium or osteogenic medium with and without Capmatinib, a selective ATP-inhibitor of MET. HGF concentration in vitro was measured with ELISA. Relative gene expression was quantified from PD-MSCs by quantitative reverse transcription real-time polymerase chain reaction.

RESULTS

Immunohistochemistry detected co-localization of HGF and MET protein in PP. HGF protein levels were significantly higher (P < 0.05) in osteogenic media (day 21: 12.19 ± 8.36 ng/mL) than in E8 medium (day 21: 0.42 ± 0.72 ng/mL). MET inhibitor had a limited feedback effect on the expression profile of the osteogenic genes tested. Gene expression levels for all but three genes were comparable in serum-free and osteogenic media at all time points.

CONCLUSION

HGF/MET present in human PP and HGF is upregulated in vitro during osteogenesis; however the targeted pathways controlled by MET may not involve osteoblast maturation.

Osteoclastogenic Potential of Tissue-Engineered Periosteal Sheet: Effects of Culture Media on the Ability to Recruit Osteoclast Precursors

Cell culture media influence the characteristics of human osteogenic periosteal sheets. We have previously found that a stem cell medium facilitates growth and collagen matrix formation in vitro and osteogenesis in vivo. However, it has not yet been demonstrated which culture medium is superior for osteoclastogenesis, a prerequisite for reconstruction of normal bone metabolic basis. To address this question, we compared chemotaxis and osteoclastogenesis in tissue-engineered periosteal sheets (TPSs) prepared with two types of culture media. Periosteal tissues obtained from adult volunteers were expanded with the conventional Medium 199 or with the stem cell medium, MesenPRO. Hematopoietic enhanced-green-fluorescent-protein (EGFP)-nude mice were prepared by γ-irradiation of Balb/c nu/nu mice and subsequent transplantation of bone marrow cells from CAG-EGFP C57BL/6 mice. TPSs were implanted subcutaneously into the chimeric mice and retrieved after intervals for immunohistopathological examination. EGFP+ cells were similarly recruited to the implantation site in both the TPSs prepared, whereas the distribution of CD11b+ cells was significantly lower in the TPS prepared with the stem cell medium. Instead, osteoclastogenesis was higher in the TPS prepared with the stem cell medium than in the one prepared with the conventional medium. These findings suggest that the stem cell medium is preferable for the preparation of more functional TPSs.

Aging-Affected MSC Functions and Severity of Periodontal Tissue Destruction in a Ligature-Induced Mouse Periodontitis Model

Mesenchymal stem cells (MSCs) are known to play important roles in the repair of lost or damaged tissues and immunotolerance. On the other hand, aging is known to impair MSC function. However, little is currently known about how aged MSCs affect the host response to the local inflammatory condition and tissue deterioration in periodontitis, which is a progressive destructive disease of the periodontal tissue potentially leading to multiple tooth loss. In this study, we examined the relationship between aging-induced impairment of MSC function and the severity of periodontal tissue destruction associated with the decrease in host immunomodulatory response using a ligature-induced periodontitis model in young and aged mice. The results of micro computerized tomography (micro-CT) and histological analysis revealed a more severe bone loss associated with increased osteoclast activity in aged (50-week-old) mice compared to young (5-week-old) mice. Immunostaining analysis revealed that, in aged mice, the accumulation of inflammatory T and B cells was higher, whereas the percentage of platelet-derived growth factor receptor α (PDGFRα)⁺ MSCs, which are known to modulate the apoptosis of T cells, was significantly lower than in young mice. In vitro analysis of MSC function showed that the expression of surface antigen markers for MSCs (Sca-1, CD90, CD146), colony formation, migration, and osteogenic differentiation of aged MSCs were significantly declined compared to those of young MSCs. Moreover, a significantly higher proportion of aged MSCs were positive for the senescence-associated β galactosidase activity. Importantly, aged MSCs presented a decreased expression of FAS-L, which was associated with a lower immunomodulatory property of aged MSCs to induce T cell apoptosis in co-cultures compared with young MSCs. In summary, this is the first study showing that aging-induced impairment of MSC function, including immunomodulatory response, is potentially correlated with progressive periodontal tissue deterioration.

The Platelet Concentrates Therapy: From the Biased Past to the Anticipated Future

The ultimate goal of research on platelet concentrates (PCs) is to develop a more predictable PC therapy. Because platelet-rich plasma (PRP), a representative PC, was identified as a possible therapeutic agent for bone augmentation in the field of oral surgery, PRP and its derivative, platelet-rich fibrin (PRF), have been increasingly applied in a regenerative medicine. However, a rise in the rate of recurrence (e.g., in tendon and ligament injuries) and adverse (or nonsignificant) clinical outcomes associated with PC therapy have raised fundamental questions regarding the validity of the therapy. Thus, rigorous evidence obtained from large, high-quality randomized controlled trials must be presented to the concerned regulatory authorities of individual countries or regions. For the approval of the regulatory authorities, clinicians and research investigators should understand the real nature of PCs and PC therapy (i.e., adjuvant therapy), standardize protocols of preparation (e.g., choice of centrifuges and tubes) and clinical application (e.g., evaluation of recipient conditions), design bias-minimized randomized clinical trials, and recognize superfluous brand competitions that delay sound progress. In this review, we retrospect the recent past of PC research, reconfirm our ultimate goals, and discuss what will need to be done in future.

Bone Marrow Mesenchymal Stromal Cells (BMMSCs) Augment Osteointegration of Dental Implants in Type 1 Diabetic Rabbits: An X-Ray Micro-Computed Tomographic Evaluation

Background and objectives: The study aimed to investigate the effect of bone marrow mesenchymal stromal cells (BMMSCs) on implant-bone osseointegration in type I diabetic New Zealand rabbits. Materials and methods: BMMSCs harvested from healthy rabbits were processed and validated for purity and osteocyte differentiability. Mandibular incisors of diabetic and control rabbits were carefully extracted, and the sockets were plugged with collagen sponges. Platelet-rich plasma (PRP) containing osteoinductive BMMSCs, and plain PRP were injected into the collagen sponge of the right and left sockets respectively. Dental implants of 2.6 mm diameter and 10 mm length were inserted into the collagen sponge of both sockets. All the animals were sacrificed six weeks post surgery to evaluate an early stage of osseointegration; the mandibles scanned by X-ray microcomputed tomography (μCT) and subjected to 3D analysis. The μCT parameters of the right implant were paired against that of the left side of each animal and analyzed by paired T-test. Results: The preclinical evaluation of the viability and osteocyte differentiation of the BMMSCs were consistent between both the donor samples. The osseointegration of dental implants with stem cell therapy (BMMSCs + PRP + collagen) in normal and diabetic rabbits was significantly higher than that of implants with adjunctive PRP + collagen only (p < 0.05). Conclusion: Stem Cell therapy with osteoinductive BMMSCs and PRP can offer a novel approach to enhance the osseointegration of dental implants in uncontrolled diabetic patients.

Deciduous Dental Pulp Stem Cells for Maxillary Alveolar Reconstruction in Cleft Lip and Palate Patients

Background

To reduce morbidity to cleft patients, new approaches have been developed and here, we report for the first time the use of deciduous dental pulp stem cells (DDPSC) associated with a hydroxyapatite-collagen sponge (Bio-Oss Collagen® 250 mg, Geistlich) for closing alveolar defects during secondary dental eruption, further comparing these results to historical controls.

Methods

Six patients, aged 8 to 12, were selected. Autologous DDPSC were isolated from each patient, then associated with the biomaterial and this bone tissue engineered set was used to fill the alveolar defect. Computed tomography was performed to assess both preoperative and 6- and 12-month postoperative outcomes. Overall morbidity was recorded. Historical controls consisted of sixteen patients previously selected and randomly assigned to group one (rhBMP-2) or group two (iliac crest bone graft).

Results

DDPSC could be isolated and characterized as mesenchymal stem cells. Progressive alveolar bone union has occurred in all patients. Similarly to group two 75.4%, SD ± 4.0, p > 0.999, but statistically different from group one (59.6%, SD ± 9.9, p > 0.999, but statistically different from group one (59.6%, SD ± 9.9.

Conclusion

For this selected group of patients, DDPSC therapy resulted in satisfactory bone healing with excellent feasibility and safety, which adds significantly to the prospect of stem cell use in clinical settings. Clinical Question/Level of Evidence. Therapeutic, II. This trial is registered with https://clinicaltrials.gov/ct2/show/NCT01932164?term=NCT01932164&rank=1.

Cell-Based Therapies for Alveolar Bone and Periodontal Regeneration: Concise Review

Current regenerative strategies for alveolar bone and periodontal tissues are effective and well adopted. These are mainly based on the use of a combination of synthetic/natural scaffolds and bioactive agents, obviating the incorporation of cells. However, there are some inherent limitations associated with traditional techniques, and we hypothesized that the use of cell-based therapies as part of comprehensive regenerative protocols may help overcome these hurdles to enhance clinical outcomes. We conducted a systematic review of human controlled clinical trials investigating the clinical and/or histological effect of the use of cell-based therapies for alveolar bone and periodontal regeneration and explored the translational potential of the different cell-based strategies identified in the included trials. A total of 16 studies (11 randomized controlled trials, 5 controlled clinical trials) were included for data synthesis and qualitative analysis with meta-analyses performed when appropriate. The results suggest a clinical benefit from the use of cell therapy. Improved outcomes were shown for alveolar ridge preservation, lateral ridge augmentation, and periodontal regeneration. However, there was insufficient evidence to identify best-performing treatment modalities amongst the different cell-based techniques. In light of the clinical and histological outcomes, we identify extraction socket and challenging lateral and vertical bone defects requiring bone block grafts as strong candidates for the adjuvant application of mesenchymal stem cells. Given the complexity, invasiveness, and costs associated with techniques that include "substantial manipulation" of tissues and cells, their additional clinical benefit when compared with "minimal manipulation" must be elucidated in future trials. Stem Cells Translational Medicine 2019;8:1286&1295.

Bone, Periodontal and Dental Pulp Regeneration in Dentistry: A Systematic Scoping Review

The aim of presented systematic scoping review was to investigate the actual and future clinical possibilities of regenerative therapies and their ability to regenerate bone, periodontal and pulp with histological confirmation of the nature of formed tissue. Electronic search was conducted using a combination between Keywords and MeSH terms in PubMed, Scopus, ISI-Web of Science and Cochrane library databases up to January 2016. Two reviewers conducted independently the papers judgment. Screened studies were read following the predetermined inclusion criteria. The included studies were evaluated in accordance with Arksey and O'Malley's modified framework. From 1349 papers, 168 completed inclusion criteria. Several characterized and uncharacterized cells used in Cell Therapy have provided bone regeneration, demonstrating bone gain in quantity and quality, even as accelerators for bone and periodontal regeneration. Synthetic and natural scaffolds presented good cell maintenance, however polyglycolid-polylactid presented faster resorption and consequently poor bone gain. The Growth Factor-Mediated Therapy was able to regenerate bone and all features of a periodontal tissue in bone defects. Teeth submitted to Revascularization presented an increase of length and width of root canal. However, formed tissues not seem able to deposit dentin, characterizing a repaired tissue. Both PRP and PRF presented benefits when applied in regenerative therapies as natural scaffolds. Therefore, most studies that applied regenerative therapies have provided promising results being possible to regenerate bone and periodontal tissue with histological confirmation. However, pulp regeneration was not reported. These results should be interpreted with caution due to the short follow-up periods.

Platelet-Rich Fibrin Extract: A Promising Fetal Bovine Serum Alternative in Explant Cultures of Human Periosteal Sheets for Regenerative Therapy

In 2004, we developed autologous periosteal sheets for the treatment of periodontal bone defects. This regenerative therapy has successfully regenerated periodontal bone and augmented alveolar ridge for implant placement. However, the necessity for 6-week culture is a limitation. Here, we examined the applicability of a human platelet-rich fibrin extract (PRFext) as an alternative to fetal bovine serum (FBS) for the explant culture of periosteal sheets in a novel culture medium (MSC-PCM) originally developed for maintaining mesenchymal stem cells. Small periosteum tissue segments were expanded in MSC-PCM + 2% PRFext for 4 weeks, and the resulting periosteal sheets were compared with those prepared by the conventional method using Medium199 + 10% FBS for their growth rate, cell multilayer formation, alkaline phosphatase (ALP) activity, and surface antigen expression (CD73, CD90, and CD105). Periosteal sheets grew faster in the novel culture medium than in the conventional medium. However, assessment of cell shape and ALP activity revealed that the periosteal cells growing in the novel medium were relatively immature. These findings suggest that the novel culture medium featuring PRFext offers advantages by shortening the culture period and excluding possible risks associated with xeno-factors without negatively altering the activity of periosteal sheets.

Stem Cells in Dentistry: Types of Intra- and Extraoral Tissue-Derived Stem Cells and Clinical Applications

Stem cells are undifferentiated cells, capable of renewing themselves, with the capacity to produce different cell types to regenerate missing tissues and treat diseases. Oral facial tissues have been identified as a source and therapeutic target for stem cells with clinical interest in dentistry. This narrative review report targets on the several extraoral- and intraoral-derived stem cells that can be applied in dentistry. In addition, stem cell origins are suggested in what concerns their ability to differentiate as well as their particular distinguishing quality of convenience and immunomodulatory for regenerative dentistry. The development of bioengineered teeth to replace the patient's missing teeth was also possible because of stem cell technologies. This review will also focus our attention on the clinical application of stem cells in dentistry. In recent years, a variety of articles reported the advantages of stem cell-based procedures in regenerative treatments. The regeneration of lost oral tissue is the target of stem cell research. Owing to the fact that bone imperfections that ensue after tooth loss can result in further bone loss which limit the success of dental implants and prosthodontic therapies, the rehabilitation of alveolar ridge height is prosthodontists' principal interest. The development of bioengineered teeth to replace the patient's missing teeth was also possible because of stem cell technologies. In addition, a “dental stem cell banking” is available for regenerative treatments in the future. The main features of stem cells in the future of dentistry should be understood by clinicians.

Comprehensive Quality Control of the Regenerative Therapy Using Platelet Concentrates: The Current Situation and Prospects in Japan

Platelet concentrates (PCs), represented by platelet-rich plasma (PRP), have been widely applied in the fields of regenerative and aesthetic therapies. PCs' mechanisms of action, however, are too complicated, and it is not easy to present the whole picture; besides, clinical outcomes are hardly reproducible in many cases. Therefore, several medically advanced countries seemingly intend to regulate PC therapies weakly or strictly because of the increasing popularity. Japan established laws and regulations for PC therapy in the "Act on the Safety of Regenerative Medicine" along with the "Pharmaceuticals, Medical Devices and Other Therapeutic Products Act" in 2014, which, to our knowledge, represent the strictest regulatory framework for production and therapeutic use of PCs in the world. According to these laws and regulations, PCs produced for topical use should be prepared as cell-based medicinal products, essentially as should stem cells, in accordance with their registered ("licensed" under actual conditions) standard operating procedures. Nonetheless, criteria for their quality are not standardized. In this review, we discuss the quality of PC preparations by focusing on the basic concept and regulatory framework of regenerative medicine in Japan. Within the new framework, PC therapy is regulated by a specific notification and registration system, as is stem cell therapy. In comparison with the latter, however, risk factors that hamper successful PC therapy are much fewer. Via appropriate evaluation of patients' conditions and whole-blood samples by simple and sensitive but not yet fully standardized assays, it is theoretically possible that PC quality will be controlled nearly completely. In addition to or instead of standardization of preparation protocols, standardization of preoperative examination of individual PC preparations is an urgent task for improving and guaranteeing the safety and efficacy of PC therapy.

The applications of regenerative medicine in sinus lift procedures: A systematic review

BACKGROUND

Findings in regenerative medicine applied to the sinus lift procedures.

PURPOSE

Evaluate the effectiveness of regenerative medicine in sinus lift.

MATERIALS AND METHODS

An extensive search for manuscripts were performed by using different combinations of keywords and MeSH terms (Pub-med; Embase; Scopus; Web of Science Core Collection; Medline; Current Contents Connect; Derwent Innovations Index; Scielo Citation Index; Cochrane library). The full text selected articles are written in English, Portuguese, Spanish, Italian, German, or French, and published until 28 of November 2016. Inclusion criteria were: implant osteointegration, radiographic, histologic, and/or histomorphometric analysis, clinical studies in humans using of regenerative medicine. This systematic review was performed by selecting only randomized controlled clinical trials and controlled clinical trials.

RESULTS

Eighteen published studies (11 CT and 7 RCT) were considered eligible for inclusion in the present systematic review. These studies demonstrated considerable variation of biomaterial and cell technics used, study design, sinus lift technic, outcomes, follow-up, and results.

CONCLUSION

Only few studies have demonstrated potential of regenerative medicine in sinus lift; further randomized clinical trials are needed to achieve more accurate results.

Adult Stem Cells of Orofacial Origin: Current Knowledge and Limitation and Future Trend in Regenerative Medicine

Stem cell research is one of the most rapidly expanding field of medicine which provides significant opportunities for therapeutic and regenerative applications. Different types of stem cells have been isolated investigating their accessibility, control of the differentiation pathway and additional immunomodulatory properties. Bulk of the literature focus has been on the study and potential applications of adult stem cells (ASC) because of their low immunogenicity and reduced ethical considerations. This review paper summarizes the basic available literature on different types of ASC with special focus on stem cells from dental and orofacial origin. ASC have been isolated from different sources, however, isolation of ASC from orofacial tissues has provided a novel promising alternative. These cells offer a great potential in the future of therapeutic and regenerative medicine because of their remarkable availability at low cost while allowing minimally invasive isolation procedures. Furthermore, their immunomodulatory and anti-inflammatory potential is of particular interest. However, there are conflicting reports in the literature regarding their particular biology and full clinical potentials. Sound knowledge and higher control over proliferation and differentiation mechanisms are prerequisites for clinical applications of these cells. Therefore, further standardized basic and translational studies are required to increase the reproducibility and reduce the controversies of studies, which in turn facilitate comparison of related literature and enhance further development in the field.

Synergistic effects of the combined use of human-cultured periosteal sheets and platelet-rich fibrin on bone regeneration: An animal study

A human-cultured alveolar bone-derived periosteal (hCP) sheet is an osteogenic grafting material used clinically in periodontal regenerative therapy, while platelet-rich fibrin (PRF), a platelet concentrate with fibrin clot, is considered to augment the wound healing process. Therefore, whether the combined use of hCP-PRF complex could facilitate bone regeneration synergistically was evaluated in animal models. Human periosteal segments (1 × 1 mm) were cultured initially on plastic dishes and formed an hCP sheet. The hCP sheet was implanted with freshly prepared human PRF into subcutaneous tissue (hCP: n = 4, hCP + PRF: n = 4) and 4 mm diameter calvarial bone defect models (hCP: n = 4, hCP + PRF: n = 4, control [defect-only]: n = 4) that prepared in nude mice. At 4 weeks postimplantation, new bone formation was evaluated by using μCT. Cell growth and neovascularization were evaluated by histochemical and immunohistological methods. In the subcutaneous tissue, mineral deposit formation, collagen deposition, and number of vessels were higher in the hCP + PRF group than in the hCP alone group. In the calvarial defect models, new bone formation was significantly higher in the hCP + PRF group than in the hCP alone group and defect-only control group. The numbers of vessels and PCNA-positive cells in calvarial defects were also increased in the hCP + PRF group more than in the hCP alone group. Platelet-rich fibrin preparations support the proliferation and the growth of periosteal cells to form well-combined active biological materials. Platelet-rich fibrin also stimulates the local angiogenesis in the implantation site. Therefore, the combined use of hCP and PRF could be clinically applicable in bone regeneration therapy.

Bioprinting for vascular and vascularized tissue biofabrication

Bioprinting is a promising technology to fabricate design-specific tissue constructs due to its ability to create complex, heterocellular structures with anatomical precision. Bioprinting enables the deposition of various biologics including growth factors, cells, genes, neo-tissues and extra-cellular matrix-like hydrogels. Benefits of bioprinting have started to make a mark in the fields of tissue engineering, regenerative medicine and pharmaceutics. Specifically, in the field of tissue engineering, the creation of vascularized tissue constructs has remained a principal challenge till date. However, given the myriad advantages over other biofabrication methods, it becomes organic to expect that bioprinting can provide a viable solution for the vascularization problem, and facilitate the clinical translation of tissue engineered constructs. This article provides a comprehensive account of bioprinting of vascular and vascularized tissue constructs. The review is structured as introducing the scope of bioprinting in tissue engineering applications, key vascular anatomical features and then a thorough coverage of 3D bioprinting using extrusion-, droplet- and laser-based bioprinting for fabrication of vascular tissue constructs. The review then provides the reader with the use of bioprinting for obtaining thick vascularized tissues using sacrificial bioink materials. Current challenges are discussed, a comparative evaluation of different bioprinting modalities is presented and future prospects are provided to the reader.

STATEMENT OF SIGNIFICANCE

Biofabrication of living tissues and organs at the clinically-relevant volumes vitally depends on the integration of vascular network. Despite the great progress in traditional biofabrication approaches, building perfusable hierarchical vascular network is a major challenge. Bioprinting is an emerging technology to fabricate design-specific tissue constructs due to its ability to create complex, heterocellular structures with anatomical precision, which holds a great promise in fabrication of vascular or vascularized tissues for transplantation use. Although a great progress has recently been made on building perfusable tissues and branched vascular network, a comprehensive review on the state-of-the-art in vascular and vascularized tissue bioprinting has not reported so far. This contribution is thus significant because it discusses the use of three major bioprinting modalities in vascular tissue biofabrication for the first time in the literature and compares their strengths and limitations in details. Moreover, the use of scaffold-based and scaffold-free bioprinting is expounded within the domain of vascular tissue fabrication.

Platelet-rich fibrin prepared from stored whole-blood samples

Background

In regenerative therapy, self-clotted platelet concentrates, such as platelet-rich fibrin (PRF), are generally prepared on-site and are immediately used for treatment. If blood samples or prepared clots can be preserved for several days, their clinical applicability will expand. Here, we prepared PRF from stored whole-blood samples and examined their characteristics.

Methods

Blood samples were collected from non-smoking, healthy male donors (aged 27–67 years, N = 6), and PRF clots were prepared immediately or after storage for 1–2 days. Fibrin fiber was examined by scanning electron microscopy. Bioactivity was evaluated by means of a bioassay system involving human periosteal cells, whereas PDGF-BB concentrations were determined by an enzyme-linked immunosorbent assay.

Results

Addition of optimal amounts of a 10% CaCl₂ solution restored the coagulative ability of whole-blood samples that contained an anticoagulant (acid citrate dextrose) and were stored for up to 2 days at ambient temperature. In PRF clots prepared from the stored whole-blood samples, the thickness and cross-links of fibrin fibers were almost identical to those of freshly prepared PRF clots. PDGF-BB concentrations in the PRF extract were significantly lower in stored whole-blood samples than in fresh samples; however, both extracts had similar stimulatory effects on periosteal-cell proliferation.

Conclusions

Quality of PRF clots prepared from stored whole-blood samples is not reduced significantly and can be ensured for use in regenerative therapy. Therefore, the proposed method enables a more flexible treatment schedule and choice of a more suitable platelet concentrate immediately before treatment, not after blood collection.

Non-invasive, quantitative assessment of the morphology of γ-irradiated human mesenchymal stem cells and periosteal cells using digital holographic microscopy

PURPOSE

To assure the quality of cells to be used in cell therapy, we examined the applicability of digital holographic microscopy (DHM) for non-invasive, quantitative assessment of changes in cell morphology.

MATERIALS AND METHODS

Mesenchymal stem cells derived from adipose tissue (MSC-AT) and bone marrow (MSC-BM), in addition to human alveolar periosteal cells (PC) as a reference, were γ-ray irradiated (1 and 4 Gy), and their morphological changes were quantified without fixation using holographic microscopy. After detachment and fixation with ethanol, cell number and surface antigen expression were determined using an automated cell counter kit and flow-cytometry, respectively.

RESULTS

Among various indexes, only indexes related to cell size were significantly changed after γ-irradiation. Both BMC-AT and BMC-BM were enlarged and more sensitive to a low dose of γ-irradiation than PC. In contrast to PC, proteins related to DNA damage repair (γ-H2AX, p21^waf1, p53 and Rb) were not substantially upregulated or sustained for a week in either MSC-AT or MSC-BM.

CONCLUSION

Instead of DNA damage markers, we suggest that cell morphological parameters (e.g. cell volume) that are monitored by DHM could be a useful and more stable marker of MSC quality.

"Over-inlay" block graft and differential morphometry: a novel block graft model to study bone regeneration and host-to-graft interfaces in rats

PURPOSE

The aim of this study was to present new a model that allows the study of the bone healing process, with an emphasis on the biological behavior of different graft-to-host interfaces. A standardized "over-inlay" surgical technique combined with a differential histomorphometric analysis is presented in order to optimize the use of critical-size calvarial defects in pre-clinical testing.

METHODS

Critical-size defects were created into the parietal bone of 8 male Wistar rats. Deproteinized bovine bone (DBBM) blocks were inserted into the defects, so that part of the block was included within the calvarial thickness and part exceeded the calvarial height (an "over-inlay" graft). All animals were sacrificed at 1 or 3 months. Histomorphometric and immunohistochemical evaluation was carried out within distinct regions of interest (ROIs): the areas adjacent to the native bone (BA), the periosteal area (PA) and the central area (CA).

RESULTS

The animals healed without complications. Differential morphometry allowed the examination of the tissue composition within distinct regions: the BA presented consistent amounts of new bone formation (NB), which increased over time (24.53%±1.26% at 1 month; 37.73%±0.39% at 3 months), thus suggesting that this area makes a substantial contribution toward NB. The PA was mainly composed of fibrous tissue (71.16%±8.06% and 78.30%±2.67%, respectively), while the CA showed high amounts of DBBM at both time points (78.30%±2.67% and 74.68%±1.07%, respectively), demonstrating a slow remodeling process. Blood vessels revealed a progressive migration from the interface with native bone toward the central area of the graft. Osterix-positive cells observed at 1 month within the PA suggested that the periosteum was a source of osteoprogenitor elements. Alkaline phosphatase data on matrix deposition confirmed this observation.

CONCLUSIONS

The present model allowed for a standardized investigation of distinct graft-to-host interfaces both at vertically augmented and inlay-augmented sites, thus possibly limiting the number of animals required for pre-clinical investigations.

The use of platelet-rich fibrin combined with periodontal ligament and jaw bone mesenchymal stem cell sheets for periodontal tissue engineering

Periodontal regeneration involves the restoration of at least three unique tissues: cementum, periodontal ligament tissue (PDL) and alveolar bone tissue. Here, we first isolated human PDL stem cells (PDLSCs) and jaw bone mesenchymal stem cells (JBMSCs). These cells were then induced to form cell sheets using an ascorbic acid-rich approach, and the cell sheet properties, including morphology, thickness and gene expression profile, were compared. Platelet-rich fibrin (PRF) derived from human venous blood was then fabricated into bioabsorbable fibrin scaffolds containing various growth factors. Finally, the in vivo potential of a cell-material construct based on PDLSC sheets, PRF scaffolds and JBMSC sheets to form periodontal tissue was assessed in a nude mouse model. In this model, PDLSC sheet/PRF/JBMSC sheet composites were placed in a simulated periodontal space comprising human treated dentin matrix (TDM) and hydroxyapatite (HA)/tricalcium phosphate (TCP) frameworks. Eight weeks after implantation, the PDLSC sheets tended to develop into PDL-like tissues, while the JBMSC sheets tended to produce predominantly bone-like tissues. In addition, the PDLSC sheet/PRF/JBMSC sheet composites generated periodontal tissue-like structures containing PDL- and bone-like tissues. Further improvements in this cell transplantation design may have the potential to provide an effective approach for future periodontal tissue regeneration.

Prolonged Survival of Transplanted Osteoblastic Cells Does Not Directly Accelerate the Healing of Calvarial Bone Defects

Considering the increased interest in cell-based bone regeneration, it is necessary to reveal the fate of transplanted cells and their substantive roles in bone regeneration. The aim of this study was to analyze the fate of transplanted cells and the effect of osteogenic cell transplantation on calvarial bone defect healing. An anti-apoptotic protein, heat shock protein (HSP) 27, was overexpressed in osteoblasts. Then, the treated osteoblasts were transplanted to calvarial bone defect and their fate was analyzed to evaluate the significance of transplanted cell survival. Transient overexpression of Hsp27 rescued MC3T3-E1 osteoblastic cells from H2 O2 -induced apoptosis without affecting osteoblastic differentiation in culture. Transplantation of Hsp27-overexpressing cells, encapsulated in collagen gel, showed higher proliferative activity, and fewer apoptotic cells in comparison with control cells. After 4-week of transplantation, both control cell- and Hsp27 overexpressed cell-transplanted groups showed significantly higher new bone formation in comparison with cell-free gel-transplantation group. Interestingly, the prolonged survival of transplanted osteoblastic cells by Hsp27 did not provide additional effect on bone healing. The transplanted cells in collagen gel survived for up to 4-week but did not differentiate into bone-forming osteoblasts. In conclusion, cell-containing collagen gel accelerated calvarial bone defect healing in comparison with cell-free collagen gel. However, prolonged survival of transplanted cells by Hsp27 overexpression did not provide additional effect. These results strongly indicate that cell transplantation-based bone regeneration cannot be explained only by the increment of osteogenic cells. Further studies are needed to elucidate the practical roles of transplanted cells that will potentiate successful bone regeneration. J. Cell. Physiol. 231: 1974-1982, 2016. © 2016 Wiley Periodicals, Inc.

In vitro immunological and biological evaluations of the angiogenic potential of platelet-rich fibrin preparations: a standardized comparison with PRP preparations

Background

Platelet-rich fibrin (PRF), a platelet-rich plasma (PRP) derivative mainly composed of fibrin networks, has been increasingly demonstrated to be effective in wound healing in clinical and pre-clinical animal studies. However, there has still been a concern that major growth factors may significantly be loss from PRF during its preparation through the slow clotting process. To address this concern, we compared the angiogenic potential of PRF and PRP by standardization of procedures based on volume ratios.

Methods

PRP, PRF, and platelet-poor plasma (PPP) were prepared from the peripheral blood of healthy donors. PRF preparations were squeezed or homogenized to produce exudate (PRFexu) or extract (PRFext), respectively. Concentrations of the angiogenic factors and their bioactivities were determined using ELISA kits, a scratch assay using endothelial cells and a chicken chorioallantoic membrane (CAM) assay.

Results

In PRP and PRF preparations, both VEGF and PDGF-BB were significantly more concentrated than PPP. In the scratch assay, PRFexu and PRFext were the most effective for wound closure. In the CAM assay, PRF membranes were the most effective for neovascularization.

Conclusions

It is suggested that PRF preparations efficiently preserve the angiogenic factors and function not only as a scaffolding material but as a reservoir of angiogenic factors in wound healing.

Treatment outcomes of implants performed after regenerative treatment of absorbed alveolar bone due to the severe periodontal disease and endoscopic surgery for maxillary sinus lift without bone grafts

OBJECTIVE

We have developed a regenerative medicine therapy for the alveolar bone and endoscopic surgery for maxillary sinus lift without bone grafts, in patients experiencing severe periodontal disease with significant absorption of the maxillary alveolar bone, in which more than 10 mm of bone thickness in the maxillary bone was attained, with satisfactory results. The objective of this study was to examine the treatment outcomes of implants that were performed after these therapies.

PARTICIPANTS AND METHODS

The participants were 36 patients with severe periodontal disease, who cannot be cured with any other treatments except the extirpation of all teeth. The 36 patients are all patients who underwent regenerative treatment of the alveolar bone through tooth replantation and transplantation of the iliac cancellous bone (the bone marrow) as well as endoscopic surgery for maxillary sinus lift from May 2003 to July 2007 in our clinic. A total of 120 implants were placed in these patients when the replanted teeth fell out because of root resorption, and the success rate was examined.

RESULTS

The success rates of the implants were 16 of 33 (48%) in the group when surveyed less than 2 years after the surgery and 84 of 87 (96.5%) in the group when surveyed more than 2 years after the surgery. A statistically significant difference was found between the 2 groups (Chi-squared test, P < 0.001).

CONCLUSIONS AND CONSIDERATIONS

It was believed that it takes approximately 2 years for the bones in the maxillary sinus floor, augmented through endoscopic surgery for maxillary sinus lift, to attain the thickness and hardness required for implant placement. Therefore, although the implant treatment should be performed later than 2 years after surgery, chewing is possible during this period, with the replanted teeth that were used for regenerative treatment of the alveolar bone. It is believed that this is an extremely effective treatment method to improve the patients' quality of life.

High-Resolution Three-Dimensional Computed Tomography Analysis of the Clinical Efficacy of Cultured Autogenous Periosteal Cells in Sinus Lift Bone Grafting

Background and Purpose

Sinus lift (SL) using cultured autogenous periosteal cells (CAPCs) combined with autogenous bone and platelet‐rich plasma (PRP) was performed to evaluate the effect of cell administration on bone regeneration, by using high‐resolution three‐dimensional computed tomography (CT).

Materials and Methods

SL with autogenous bone and PRP plus CAPC [CAPC(+)SL] was performed in 23 patients. A piece of periosteum taken from the mandible was cultured in M199 medium with 10% fetal bovine serum (FBS) for 6 weeks. As control, 16 patients received SL with autogenous bone and PRP [CAPC(−)SL]. Three‐dimensional CT imaging was performed before and 4 months and 1 year after SL, and stratification was performed based on CT numbers (HUs) corresponding to soft tissue and cancellous or cortical bone.

Results

The augmented bone in CAPC(+)SL revealed an increase in HUs corresponding to cancellous bone as well as a decrease in HUs corresponding to grafted cortical bone. In addition, HUs corresponding to cancellous bone in the graft bed were increased in CAPC(+)SL but were decreased in CAPC(−)SL. Insertion torque during implant placement was significantly higher in CAPC(+)SL.

Conclusion

By promoting bone anabolic activity both in augmented bone and graft bed, CAPCs are expected to aid primary fixation and osseointegration of implants in clinical applications.

Quantitative single-cell motility analysis of platelet-rich plasma-treated endothelial cells in vitro

Platelet-rich plasma (PRP) has been widely applied in regenerative therapy due to its high concentration of growth factors. Previous in vitro and in vivo studies have provided evidence supporting the angiogenic activity of PRP. To more directly demonstrate how PRP acts on endothelial cells, we examined the PRP-induced changes in the motility of human umbilical vein endothelial cells by examining the involvement of VEGF. Time-lapse quantitative imaging demonstrated that in the initial phase (∼2 h) of treatment, PRP substantially stimulated cell migration in a wound-healing assay. However, this effect of PRP was not sustained at significant levels beyond the initial phase. The average net distance of cell migration at 10 h was 0.45 ± 0.16 mm and 0.82 ± 0.23 mm in control and PRP-stimulated cells, respectively. This effect was also demonstrated with recombinant human VEGF and was significantly attenuated by a neutralizing anti-VEGF antibody. Immunofluorescent examination of paxillin and actin fibers demonstrated that PRP concomitantly up-regulated focal adhesion and cytoskeletal formation. Western blotting analysis of phosphorylated VEGFR2 demonstrated that PRP mainly stimulated the phosphorylation of immature VEGFR2 in a dose- and time-dependent manner, an action that was completely blocked by the neutralizing antibody. Taken together, these data suggest that PRP acts directly on endothelial cells via the activation of VEGFR2 to transiently up-regulate their motility. Thus, the possibility that PRP desensitizes target endothelial cells for a relatively long period of time after short-term activation should be considered when the controlled release system of PRP components is designed.

Cell-based bone regeneration for alveolar ridge augmentation--cell source, endogenous cell recruitment and immunomodulatory function

Alveolar ridge plays a pivotal role in supporting dental prosthesis particularly in edentulous and semi-dentulous patients. However the alveolar ridge undergoes atrophic change after tooth loss. The vertical and horizontal volume of the alveolar ridge restricts the design of dental prosthesis; thus, maintaining sufficient alveolar ridge volume is vital for successful oral rehabilitation. Recent progress in regenerative approaches has conferred marked benefits in prosthetic dentistry, enabling regeneration of the atrophic alveolar ridge. In order to achieve successful alveolar ridge augmentation, sufficient numbers of osteogenic cells are necessary; therefore, autologous osteoprogenitor cells are isolated, expanded in vitro, and transplanted to the specific anatomical site where the bone is required. Recent studies have gradually elucidated that transplanted osteoprogenitor cells are not only a source of bone forming osteoblasts, they appear to play multiple roles, such as recruitment of endogenous osteoprogenitor cells and immunomodulatory function, at the forefront of bone regeneration. This review focuses on the current consensus of cell-based bone augmentation therapies with emphasis on cell sources, transplanted cell survival, endogenous stem cell recruitment and immunomodulatory function of transplanted osteoprogenitor cells. Furthermore, if we were able to control the mobilization of endogenous osteoprogenitor cells, large-scale surgery may no longer be necessary. Such treatment strategy may open a new era of safer and more effective alveolar ridge augmentation treatment options.

Maxillary Sinus Augmentation Combining Bio-Oss with the Bone Marrow Aspirate Concentrate: A Histomorphometric Study in Humans

Purpose. To investigate the regenerative results obtained with the association of bone marrow aspirate concentrate using the Bone Marrow Aspirate Concentrate (BMAC) method to a xenogeneic bone graft (Bio-Oss) in sinus floor elevation. Materials and Methods. Using a randomized controlled study design in eight consecutive patients (age of 55.4 ± 9.2 years), 16 sinus floor lift procedures were performed with Bio-Oss alone (control group, CG, n = 8) or combined with bone marrow aspirate concentrate obtained via the BMAC method (test group, TG, n = 8). Six months after the grafting procedures, bone biopsies were harvested during implant placement and were analyzed by histomorphometry. Results. Histomorphometric analysis revealed a significantly higher amount (p < 0.05) of vital mineralized tissue in TG when compared to the CG (55.15 ± 20.91% and 27.30 ± 5.55%, resp.). For nonvital mineralized tissue, TG presented a statistically higher level of Bio-Oss resorption (p < 0.05) when compared with the CG (6.32 ± 12.03% and 22.79 ± 9.60%, resp.). Both groups (TG and CG) showed no significantly different levels (p > 0.05) of nonmineralized tissue (38.53 ± 13.08% and 49.90 ± 7.64%, resp.). Conclusion. The use of bone marrow concentrate obtained by BMAC method increased bone formation in sinus lift procedures.

Real-time quantitative polymerase chain reaction and flow cytometric analyses of cell adhesion molecules expressed in human cell-multilayered periosteal sheets in vitro

BACKGROUND AIMS

Cultured human periosteal sheets more effectively function as an osteogenic grafting material at implantation sites than do dispersed periosteal cells. Because adherent cell growth and differentiation are regulated by cell-cell and cell-extracellular matrix contacts, we hypothesized that this advantage is a result of the unique cell adhesion pattern formed by their multiple cell layers and abundant extracellular matrix. To test this hypothesis, we prepared three distinct forms of periosteal cell cultures: three-dimensional cell-multilayered periosteal sheets, two-dimensional dispersed cell cultures, and three-dimensional hybrid mock-ups of cells dispersed onto collagen sponges.

METHODS

Periosteal cells were obtained from human alveolar bone. Cell adhesion and extracellular matrix molecules were quantitatively determined at the messenger RNA and protein levels by means of real-time quantitative polymerase chain reaction and flow cytometry, respectively.

RESULTS

Real-time quantitative polymerase chain reaction analysis demonstrated that regardless of culture media α1 integrin, vascular cell adhesion molecule-1, fibronectin and collagen type 1 were substantially upregulated, whereas CD44 was strongly downregulated in periosteal sheets compared with dispersed cell monolayers. With increased thickness, stem cell medium upregulated several integrins (β1, α1 and α4), CD146, vascular cell adhesion molecule-1, fibronectin and collagen type 1 in the periosteal sheets. Flow cytometric analysis revealed that the active configuration of β1 integrin was substantially downregulated in the stem cell medium-expanded cell cultures. The cell adhesion pattern found in the mock-up cultures was almost identical to that of genuine periosteal sheets.

CONCLUSIONS

Integrin α1β1 and CD44 function as the main cell adhesion molecule in highly cell-multilayered periosteal sheets and dispersed cells, respectively. This difference may account for the more potent osteogenic activity shown by the thicker periosteal sheets.

Bio-modulators in platelet-rich plasma: a comparison of the amounts in products from healthy donors and patients produced with three different techniques

BACKGROUND

Platelet-rich plasma consists of platelets concentrated in a small volume of plasma and constitutes a reservoir of bio-modulators potentially useful in tissue repair. The amounts of bio-modulators detectable in platelet-rich plasma prepared with various commercial or "in house" methods have been reported, but virtually all the analyses described have been performed on platelet-rich plasma derived from healthy donors. Since leucocyte contamination is technically unavoidable, we investigated whether platelet-rich plasma prepared from patients could contain different amounts of bio-modulators because of a possible activated status of the leucocytes.

MATERIALS AND METHODS

We evaluated platelet-rich plasma prepared with three different techniques (the commercial Vivostat and Biomet recover GPS II systems and an "in house" method) starting from whole blood from healthy donors and patients. Specifically, we compared the levels of sHLA-I, sFasL, platelet-derived growth factor, transforming growth factors-beta and vascular endothelial growth factor in the platelet-rich plasma releasates according to the method of preparation and to the immune system activation status of the subjects.

RESULTS

With the exception of sHLA-I levels, no differences were found in the surrogate indices of lymphocyte activation between healthy donors and patients. No significant differences were found in sHLA-I, sFasL, platelet-derived growth factor, transforming growth factors-beta and vascular endothelial growth factor levels detectable in platelet-rich plasma produced with the three different methods in either healthy donors or patients.

DISCUSSION

On the whole our findings indicate that the overall content of bio-modulators in autologous platelet-rich plasma is not influenced by T-lymphocyte activation status, at least in patients with uncomplicated femoral fractures. The amounts of sFasL and sHLA-I detected in all the platelet-rich plasma releasates studied were very small, far below the amounts detectable in all clinically available blood derivatives and absolutely insufficient to induce sHLA-I and/or sFasL mediated immunomodulation.

Current concepts: tissue engineering and regenerative medicine applications in the ankle joint

Tissue engineering and regenerative medicine (TERM) has caused a revolution in present and future trends of medicine and surgery. In different tissues, advanced TERM approaches bring new therapeutic possibilities in general population as well as in young patients and high-level athletes, improving restoration of biological functions and rehabilitation. The mainstream components required to obtain a functional regeneration of tissues may include biodegradable scaffolds, drugs or growth factors and different cell types (either autologous or heterologous) that can be cultured in bioreactor systems (in vitro) prior to implantation into the patient. Particularly in the ankle, which is subject to many different injuries (e.g. acute, chronic, traumatic and degenerative), there is still no definitive and feasible answer to ‘conventional’ methods. This review aims to provide current concepts of TERM applications to ankle injuries under preclinical and/or clinical research applied to skin, tendon, bone and cartilage problems. A particular attention has been given to biomaterial design and scaffold processing with potential use in osteochondral ankle lesions.

Oxidative actions of hydrogen peroxide in human gingival and oral periosteal fibroblasts: responses to glutathione and nicotine, relevant to healing in a redox environment

Background

This study aims to validate pro-oxidant actions of nicotine (N), using hydrogen peroxide (H₂O₂) and the antioxidant glutathione (G) in an in vitro model of human gingival fibroblasts (HGF) and human oral periosteal fibroblasts (HPF); radiolabelled androgens are used as biomarkers of redox status. Oxidative stress is an important mediator of inflammatory repair. The androgen metabolite 5α-dihydrotestosterone (DHT) is an effective biomarker of oxidative stress and healing.

Methods

6 Cell-lines of HGF and HPF established in confluent monolayer culture were incubated in Eagle's MEM using 14C-testosterone and 14C-4-androstendione as substrate; in conjunction with effective concentrations of N, G and H₂O₂ established at N250, G3 μg/ml and 3%H₂O₂ w/w, 0.5 μl/ml. Combinations of H₂O₂G and H₂O₂GN were used in order to compare the oxidative effects of N/H₂O₂ and their responses to glutathione. At 24 h, the medium was solvent extracted, evaporated to dryness and subjected to TLC in a benzene/acetone solvent system 4:1 v/v for the separation of metabolites. The separated metabolites were quantified using a radioisotope scanner.

Results

The mean trends of 6 cell-lines for both substrates and each cell type demonstrated that the yield of the main metabolite DHT was significantly reduced by N and H₂O₂ alone (2-fold, n=6; p<0.01). The inhibition caused by H₂O₂ was overcome by the antioxidant glutathione in the combination H₂O₂G, to values similar to those of controls (n=6; p<0.01). It is relevant that when N was added to this neutralized combination, the decrease in yields of DHT triggered by N were comparable to those induced by H₂O₂; and retaining the positive effect of G.

Conclusion

Oxidative stress mediated by H₂O₂ was overcome by glutathione and recurred when nicotine was added, suggestive of a pro- oxidant role for nicotine. Androgen biomarkers are a sensitive index of oxidative stress which affects wound healing.

•

DHT is an effective redox marker in HGF and oral periosteal fibroblasts in vitro.

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Both nicotine and H₂O₂ reduced yields of DHT, indicative of induced oxidative stress.

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Nicotine has oxidative effects that are comparable to those of H₂O₂ mediated by AR.

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Effects of nicotine and H₂O₂ were reduced by glutathione in HGF and HPF cultures.

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Redox status is relevant to androgen receptor-mediated inflammatory wound healing.

Application of stem-cell media to explant culture of human periosteum: An optimal approach for preparing osteogenic cell material

As part of our clinical tests on bone regeneration using cultured periosteal sheets, here, we prepared cultured periosteal sheets in two types of stem-cell culture media, STK1 and STK3. Human periosteum was expanded either in 1% human serum–supplemented STK1 for 28 days, in 1% human serum–supplemented STK1 for 14 days followed by 1% human serum–supplemented STK3 for 14 days (1% human serum–supplemented STK1+3), or in 10% fetal bovine serum–supplemented Medium 199 for 28 days (control). Cultured periosteal sheet diameter and DNA content were significantly higher, and the multilayer structure was prominent in 1% human serum–supplemented STK1 and 1% human serum–supplemented STK1+3. The messenger RNA of osteoblastic markers was significantly upregulated in 1% human serum–supplemented STK1+3. Osteopontin-immunopositive staining and mineralization were evident across a wide area of the cultured periosteal sheet in 1% human serum–supplemented STK1+3. Subcutaneous implantation in nude mice following expansion in 1% human serum–supplemented STK1+3 produced the highest cultured periosteal sheet osteogenic activity. Expansion in 1% human serum–supplemented STK1+3 successfully induced cultured periosteal sheet growth while retaining osteogenic potential, and subsequent osteoblastic induction promoted the production of homogeneous cell material.

Clinical applications of cell-based approaches in alveolar bone augmentation: a systematic review

BACKGROUND

Cell-based approaches, utilizing adult mesenchymal stem cells (MSCs), are reported to overcome the limitations of conventional bone augmentation procedures.

PURPOSE

The study aims to systematically review the available evidence on the characteristics and clinical effectiveness of cell-based ridge augmentation, socket preservation, and sinus-floor augmentation, compared to current evidence-based methods in human adult patients.

MATERIALS AND METHODS

MEDLINE, EMBASE, and CENTRAL databases were searched for related literature. Both observational and experimental studies reporting outcomes of "tissue engineered" or "cell-based" augmentation in ≥5 adult patients alone, or in comparison with non-cell-based (conventional) augmentation methods, were eligible for inclusion. Primary outcome was histomorphometric analysis of new bone formation. Effectiveness of cell-based augmentation was evaluated based on outcomes of controlled studies.

RESULTS

Twenty-seven eligible studies were identified. Of these, 15 included a control group (8 randomized controlled trials [RCTs]), and were judged to be at a moderate-to-high risk of bias. Most studies reported the combined use of cultured autologous MSCs with an osteoconductive bone substitute (BS) scaffold. Iliac bone marrow and mandibular periosteum were frequently reported sources of MSCs. In vitro culture of MSCs took between 12 days and 1.5 months. A range of autogenous, allogeneic, xenogeneic, and alloplastic scaffolds was identified. Bovine bone mineral scaffold was frequently reported with favorable outcomes, while polylactic-polyglycolic acid copolymer (PLGA) scaffold resulted in graft failure in three studies. The combination of MSCs and BS resulted in outcomes similar to autogenous bone (AB) and BS. Three RCTs and one controlled trial reported significantly greater bone formation in cell-based than conventionally grafted sites after 3 to 8 months.

CONCLUSIONS

Based on limited controlled evidence at a moderate-to-high risk of bias, cell-based approaches are comparable, if not superior, to current evidence-based bone grafting methods, with a significant advantage of avoiding AB harvesting. Future clinical trials should additionally evaluate patient-based outcomes and the time-/cost-effectiveness of these approaches.