Fibroin scaffold repairs critical-size bone defects in vivo supported by human amniotic fluid and dental pulp stem cells

Bladder Smooth Muscle Cells Differentiation from Dental Pulp Stem Cells: Future Potential for Bladder Tissue Engineering

Dental pulp stem cells (DPSCs) are multipotent cells capable of differentiating into multiple cell lines, thus providing an alternative source of cell for tissue engineering. Smooth muscle cell (SMC) regeneration is a crucial step in tissue engineering of the urinary bladder. It is known that DPSCs have the potential to differentiate into a smooth muscle phenotype in vitro with differentiation agents. However, most of these studies are focused on the vascular SMCs. The optimal approaches to induce human DPSCs to differentiate into bladder SMCs are still under investigation. We demonstrate in this study the ability of human DPSCs to differentiate into bladder SMCs in a growth environment containing bladder SMCs-conditioned medium with the addition of the transforming growth factor beta 1 (TGF-β1). After 14 days of exposure to this medium, the gene and protein expression of SMC-specific marker (α-SMA, desmin, and calponin) increased over time. In particular, myosin was present in differentiated cells after 11 days of induction, which indicated that the cells differentiated into the mature SMCs. These data suggested that human DPSCs could be used as an alternative and less invasive source of stem cells for smooth muscle regeneration, a technology that has applications for bladder tissue engineering.

Mesenchymal Stem Cells Derived from Dental Pulp: A Review

The mesenchymal stem cells of dental pulp (DPSCs) were isolated and characterized for the first time more than a decade ago as highly clonogenic cells that were able to generate densely calcified colonies. Now, DPSCs are considered to have potential as stem cell source for orthopedic and oral maxillofacial reconstruction, and it has been suggested that they may have applications beyond the scope of the stomatognathic system. To date, most studies have shown that, regardless of their origin in third molars, incisors, or exfoliated deciduous teeth, DPSCs can generate mineralized tissue, an extracellular matrix and structures type dentin, periodontal ligament, and dental pulp, as well as other structures. Different groups worldwide have designed and evaluated new efficient protocols for the isolation, expansion, and maintenance of clinically safe human DPSCs in sufficient numbers for various therapeutics protocols and have discussed the most appropriate route of administration, the possible contraindications to their clinical use, and the parameters to be considered for monitoring their clinical efficacy and proper biological source. At present, DPSC-based therapy is promising but because most of the available evidence was obtained using nonhuman xenotransplants, it is not a mature technology.

Immune regulatory properties of CD117(pos) amniotic fluid stem cells vary according to gestational age

Amniotic Fluid Stem (AFS) cells are broadly multipotent fetal stem cells derived from the positive selection and ex vivo expansion of amniotic fluid CD117/c-kit(pos) cells. Considering the differentiation potential in vitro toward cell lineages belonging to the three germ layers, AFS cells have raised great interest as a new therapeutic tool, but their immune properties still need to be assessed. We analyzed the in vitro immunological properties of AFS cells from different gestational age in coculture with T, B, and natural killer (NK) cells. Nonactivated (resting) first trimester-AFS cells showed lower expression of HLA class-I molecules and NK-activating ligands than second and third trimester-AFS cells, whose features were associated with lower sensitivity to NK cell-mediated lysis. Nevertheless, inflammatory priming with interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α) enhanced resistance of all AFS cell types to NK cytotoxicity. AFS cells modulated lymphocyte proliferation in a different manner according to gestational age: first trimester-AFS cells significantly inhibited T and NK cell proliferation, while second and third trimester-AFS cells were less efficient. In addition, only inflammatory-primed second trimester-AFS cells could suppress B cell proliferation, which was not affected by the first and third trimester-AFS cells. Indolamine 2,3 dioxygenase pathway was significantly involved only in T cell suppression mediated by second and third trimester-AFS cells. Overall, this study shows a number of significant quantitative differences among AFS cells of different gestational age that have to be considered in view of their clinical application.

Osteogenic Potential of Dental Mesenchymal Stem Cells in Preclinical Studies: A Systematic Review Using Modified ARRIVE and CONSORT Guidelines

Background and Objective. Dental stem cell-based tissue engineered constructs are emerging as a promising alternative to autologous bone transfer for treating bone defects. The purpose of this review is to systematically assess the preclinical in vivo and in vitro studies which have evaluated the efficacy of dental stem cells on bone regeneration. Methods. A literature search was conducted in Ovid Medline, Embase, PubMed, and Web of Science up to October 2014. Implantation of dental stem cells in animal models for evaluating bone regeneration and/or in vitro studies demonstrating osteogenic potential of dental stem cells were included. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were used to ensure the quality of the search. Modified ARRIVE (Animal research: reporting in invivo experiments) and CONSORT (Consolidated reporting of trials) were used to critically analyze the selected studies. Results. From 1914 citations, 207 full-text articles were screened and 137 studies were included in this review. Because of the heterogeneity observed in the studies selected, meta-analysis was not possible. Conclusion. Both in vivo and in vitro studies indicate the potential use of dental stem cells in bone regeneration. However well-designed randomized animal trials are needed before moving into clinical trials.

Dental stem cell sources and their potentials for bone tissue engineering

Tissue engineering arouses excitement in all medical fields that deal with bone healing. The ultimate aim of these approaches are to shorten the healing process, obtain highly differentiated functional tissues and eliminate the need for a second surgical site required for autogenous bone grafts. Mesenchymal stem cells have been increasingly used in the experiments which were conducted in these fields and the results are promising. Dental stem cells have come to the forefront both because of their relative ease of access and also their superior characteristics. This article investigates the importance of dental stem cells for bone tissue engineering and their regeneration potentials.

Role of hepatocyte growth factor in the immunomodulation potential of amniotic fluid stem cells

Human amniotic fluid stem cells (hAFSCs) may be useful for regenerative medicine because of their potential to differentiate into all three germ layers and to modulate immune response with different types of secretion molecules. This last issue has not been completely elucidated. The aim of this study was to investigate the secretome profile of the hAFSC, focusing on the role of hepatocyte growth factor (HGF) in immunoregulation through short and long cocultures with human peripheral blood mononuclear cells. We found that HGF produced by hAFSCs exerts a cytoprotective role, inducing an increase in caspase-dependent apoptosis in human immune cells. This study provides evidence supporting the hypothesis that amniotic fluid is an ideal source of stem cells for expansion and banking properties for therapeutic use. hAFSCs not only are less immunogenic but also can secrete immunoregulatory factors that may be useful in autoimmune diseases or allogenic implants.

SIGNIFICANCE

New information about the secretome pattern is reported in this paper. Human amniotic fluid stem cells (hAFSCs) possess immunomodulatory properties involving hepatocyte growth factor production. hAFSCs could be used in immunotherapies and might be able to avoid allogenic rejection.

Regeneration of rabbit calvarial defects using cells-implanted nano-hydroxyapatite coated silk scaffolds

Background

The aim of this study was to characterize the efficacy of nano-hydroxyapatite-coated silk fibroin constructs as a scaffold for bone tissue engineering and to determine the osteogenic effect of human dental pulp and periodontal ligament derived cells at an early stage of healing in rabbits. 3D silk fibroin constructs were developed and coated using nano-hydroxyapatite crystals. Dental pulp and periodontal ligament cells from extracted human third molars were cultured and seeded onto the silk scaffolds prior to in vivo implantation into 8 male New Zealand White rabbits. Four circular windows 8 mm in diameter were created in the calvarium of each animal. The defects were randomly allocated to the groups; (1) silk scaffold with dental pulp cells (DPSS), (2) silk scaffold with PDL cells (PDLSS), (3) normal saline-soaked silk scaffold (SS), and (4) empty control. The animals were sacrificed 2 (n = 4) or 4 weeks (n = 4) postoperatively. The characteristics of the silk scaffolds before and after cell seeding were analyzed using SEM. Samples were collected for histologic and histomorphometic analysis. ANOVA was used for statistical analysis.

Result

Histologic view of the experimental sites showed well-maintained structure of the silk scaffolds mostly unresorbed at 4 weeks. The SEM observations after cell-seeding revealed attachment of the cells onto silk fibroin with production of extracellular matrix. New bone formation was observed in the 4 week groups occurring from the periphery of the defects and the silk fibers were closely integrated with the new bone. There was no significant difference in the amount of bone formation between the SS group and the DPSS and PDLSS groups.

Conclusion

Within the limitations of this study, silk scaffold is a biocompatible material with potential expediency as an osteoconductive scaffold in bone tissue engineering. However, there was no evidence to suggest that the addition of hDPCs and hPDLCs to the current rabbit calvarial defect model can produce an early effect in augmenting osteogenesis.

Comparative investigation of human amniotic epithelial cells and mesenchymal stem cells for application in bone tissue engineering

Emerging evidence suggests amniotic epithelial cells (AECs) as a promising source of progenitor cells in regenerative medicine and bone tissue engineering. However, investigations comparing the regenerative properties of AECs with other sources of stem cells are particularly needed before the feasibility of AECs in bone tissue engineering can be determined. This study aimed to compare human amniotic epithelial cells (hAECs), human bone marrow mesenchymal stem cells (hBMSCs), and human amniotic fluid derived mesenchymal stem cells (hAFMSCs) in terms of their morphology, proliferation, immunophenotype profile, and osteogenic capacity in vitro and in vivo. Not only greatly distinguished by cell morphology and proliferation, hAECs, hAFMSCs, and hBMSCs exhibited remarkably different signature regarding immunophenotypical profile. Microarray analysis revealed a different expression profile of genes involved in ossification along the three cell sources, highlighting the impact of different anatomical origin and molecular response to osteogenic induction on the final tissue-forming potential. Furthermore, our data indicated a potential role of FOXC2 in early osteogenic commitment.

Bone regeneration in critical-size calvarial defects using human dental pulp cells in an extracellular matrix-based scaffold

The rat calvarial defect is an established model to evaluate craniofacial bone regeneration using cell-scaffold biocomplexes. Dental pulp harbors stem cells with significant osteogenic properties. Extracellular matrix (ECM)-like scaffolds simulate the environment that cells observe in vivo. In the present study, we evaluated the osteogenic effect of a biocomplex of human dental pulp cells and a hyaluronic-based hydrogel scaffold in calvarial defects of immunocompetent rats. Dental pulp cells at the 2nd passage were characterized by flow cytometry, osteodifferentiated ex vivo for 4 days and the whole population was encapsulated in the synthetic ECM matrix. Cell vitality was verified 24 h upon encapsulation. 5 mm calvarial defects were created in 30 male rats and filled with the biocomplex, the scaffold alone, or left untreated. Histological evaluation at 8 weeks showed incomplete bone regeneration in all groups. The scaffold was not fully degraded and entrapped cells were detected in it. Histomorphometry showed statistically significant superior new bone formation in the biocomplex-treated group, compared to the two other groups. The present study provides evidence that the whole population of human dental pulp cells can advance bone healing when transplanted in immunocompetent animals and highlights the importance of proper scaffold degradation in cell-driven bioengineering treatments.

Perinatal stem cells: A promising cell resource for tissue engineering of craniofacial bone

In facing the mounting clinical challenge and suboptimal techniques of craniofacial bone defects resulting from various conditions, such as congenital malformations, osteomyelitis, trauma and tumor resection, the ongoing research of regenerative medicine using stem cells and concurrent advancement in biotechnology have shifted the focus from surgical reconstruction to a novel stem cell-based tissue engineering strategy for customized and functional craniofacial bone regeneration. Given the unique ontogenetical and cell biological properties of perinatal stem cells, emerging evidence has suggested these extraembryonic tissue-derived stem cells to be a promising cell source for extensive use in regenerative medicine and tissue engineering. In this review, we summarize the current achievements and obstacles in stem cell-based craniofacial bone regeneration and subsequently we address the characteristics of various types of perinatal stem cells and their novel application in tissue engineering of craniofacial bone. We propose the promising feasibility and scope of perinatal stem cell-based craniofacial bone tissue engineering for future clinical application.

In vivo stem cell transplantation using reduced cell numbers

Dental pulp stem cell (DPSC) characterization is essential for regeneration of a dentin/pulp like complex in vivo. This is especially important for identifying the potential of DPSCs to function as stem cells. Previously reported DPSC transplantation methods have used with huge numbers of cells, along with hydroxyapatite/tricalcium phosphate (HA/TCP), gelatin and fibrin, and collagen scaffolds. This protocol describe a transplantation protocol that uses fewer cells and a temperature-responsive cell culture dish.

Biomimetic approaches to complex craniofacial defects

The primary goals of craniofacial reconstruction include the restoration of the form, function, and facial esthetics, and in the case of pediatric patients, respect for craniofacial growth. The surgeon, however, faces several challenges when attempting a reconstructive cranioplasty. For that reason, craniofacial defect repair often requires sophisticated treatment strategies and multidisciplinary input. In the ideal situation, autologous tissue similar in structure and function to that which is missing can be utilized for repair. In the context of the craniofacial skeleton, autologous cranial bone, or secondarily rib, iliac crest, or scapular bone, is most favorable. Often, this option is limited by the finite supply of available bone. Therefore, alternative strategies to repair craniofacial defects are necessary. In the field of regenerative medicine, tissue engineering has emerged as a promising concept, and several methods of bone engineering are currently under investigation. A growth factor-based approach utilizing bone morphogenetic proteins (BMPs) has demonstrated stimulatory effects on cranial bone and defect repair. When combined with cell-based and matrix-based models, regenerative goals can be optimized. This manuscript intends to review recent investigations of tissue engineering models used for the repair of craniofacial defects with a focus on the role of BMPs, scaffold materials, and novel cell lines. When sufficient autologous bone is not available, safe and effective strategies to engineer bone would allow the surgeon to meet the reconstructive goals of the craniofacial skeleton.

Effects of composite films of silk fibroin and graphene oxide on the proliferation, cell viability and mesenchymal phenotype of periodontal ligament stem cells

In regenerative dentistry, stem cell-based therapy often requires a scaffold to deliver cells and/or growth factors to the injured site. Graphene oxide (GO) and silk fibroin (SF) are promising biomaterials for tissue engineering as they are both non toxic and promote cell proliferation. On the other hand, periodontal ligament stem cells (PDLSCs) are mesenchymal stem cells readily accessible with a promising use in cell therapy. The purpose of this study was to investigate the effects of composite films of GO, SF and GO combined with fibroin in the mesenchymal phenotype, viability, adhesion and proliferation rate of PDLSCs. PDLSCs obtained from healthy extracted teeth were cultured on GO, SF or combination of GO and SF films up to 10 days. Adhesion level of PDSCs on the different biomaterials were evaluated after 12 h of culture, whereas proliferation rate of cells was assessed using the MTT assay. Level of apoptosis was determined using Annexin-V and 7-AAD and mesenchymal markers expression of PDLSCs were analyzed by flow cytometry. At day 7 of culture, MTT experiments showed a high rate of proliferation of PDLSCs growing on GO films compared to the other tested biomaterials, although it was slightly lower than in plastic (control). However PDLSCs growing in fibroin or GO plus fibroin films showed a discrete proliferation. Importantly, at day 10 of culture it was observed a significant increase in PDLSCs proliferation rate in GO films compared to plastic (P < 0.05), as well as in GO plus fibroin compared to fibroin alone (P < 0.001). Flow cytometry analysis showed that culture of PDLSCs in fibroin, GO or GO plus fibroin films did not significantly alter the level of expression of the mesenchymal markers CD73, CD90 or CD105 up to 168 h, being the cell viability in GO even better than obtained in plastic. Our findings suggest that the combination of human dental stem cells/fibroin/GO based-bioengineered constructs have strong potential for their therapeutic use in regenerative dentistry.

Critical-size bone defect repair using amniotic fluid stem cell/collagen constructs: effect of oral ferutinin treatment in rats

AIMS

This study aims to evaluate the bone regeneration in a rat calvarias critical size bone defect treated with a construct consisting of collagen type I and human amniotic fluid stem cells (AFSCs) after oral administration of phytoestrogen ferutinin.

MAIN METHODS

In 12 week old male rats (n=10), we performed two symmetric full-thickness cranial defects on each parietal region, and a scaffold was implanted into each cranial defect. The rats were divided into four groups: 1) collagen scaffold, 2) collagen scaffold+ferutinin at a dose of 2mg/kg/5 mL, 3) collagen scaffold + AFSCs, and 4) collagen scaffold + AFSCs + ferutinin. The rats were sacrificed after 4 weeks, and the calvariae were removed, fixed, embedded in paraffin and cut into 7 μm thick sections. Histomorphometric measures, immunohistochemical and immunofluorescence analyses were performed on the paraffin sections.

KEY FINDINGS

The histomorphometric analysis on H&E stained sections showed a significant increase in the regenerated area of the 4th group compared with the other groups. Immunohistochemistry performed with a human anti-mitochondrial antibody showed the presence of AFSCs 4 weeks after the transplant. Immunofluorescence analysis revealed the presence of osteocalcin and estrogen receptors (ERα and GPR30) in all groups, with a greater expression of all markers in samples where the scaffold was treated with AFSCs and the rats were orally administered ferutinin.

SIGNIFICANCE

Our results demonstrated that the oral administration of ferutinin is able to improve the bone regeneration of critical-size bone defects in vivo that is obtained with collagen-AFSCs constructs.

The Fas/Fas ligand apoptosis pathway underlies immunomodulatory properties of human biliary tree stem/progenitor cells

BACKGROUND & AIMS

Human biliary tree stem/progenitor cells (hBTSCs) are multipotent epithelial stem cells, easily obtained from the biliary tree, with the potential for regenerative medicine in liver, biliary tree, and pancreas diseases. Recent reports indicate that human mesenchymal stem cells are able to modulate the T cell immune response. However, no information exists on the capabilities of hBTSCs to control the allogeneic response. The aims of this study were to evaluate FasL expression in hBTSCs, to study the in vitro interaction between hBTSCs and human lymphocytes, and the role of Fas/FasL modulation in inducing T cell apoptosis in hBTSCs/T cell co-cultures.

METHODS

Fas and FasL expression were evaluated in situ and in vitro by immunofluorescence and western blotting. Co-cultures of hBTSCs with human leukocytes were used to analyze the influence of hBTSCs on lymphocytes activation and apoptosis.

RESULTS

hBTSCs expressed HLA antigens and FasL in situ and in vitro. Western blot data demonstrated that hBTSCs constitutively expressed high levels of FasL that increased after co-culture with T cells. Confocal microscopy demonstrated that FasL expression was restricted to EpCAM(+)/LGR5(+) cells. FACS analysis of T cells co-cultured with hBTSCs indicated that hBTSCs were able to induce apoptosis in activated CD4(+) and CD8(+) T cell populations. Moreover, the Fas receptor appears to be more expressed in T cells co-cultured with hBTSCs than in resting T cells.

CONCLUSIONS

Our data suggest that hBTSCs could modulate the T cell response through the production of FasL, which influences the lymphocyte Fas/FasL pathway by inducing "premature" apoptosis in CD4(+) and CD8(+) T cells.

Can SHED or DPSCs be used to repair/regenerate non-dental tissues? A systematic review of in vivo studies

Dental pulp has been identified as a novel and promising stem cell source. The following systematic review presents and summarises in vivo studies that have used stem cells from the dental pulp of permanent and deciduous teeth to repair or regenerate non-dental tissues. An electronic customised search was performed using 4 different databases (Entrez PubMed, Cab Abstracts, Scopus and Web of Science). Only full-text research manuscripts published in English between the years of 2000 and 2012 were included. The manuscripts were retrieved based on the following keywords and/or abbreviations: [Stem Cells from Human Exfoliated Deciduous teeth (SHED)] AND/OR [Dental Pulp Stem Cells (DPSC)] AND [tissue regeneration] AND [tissue repair]. Only manuscripts involving in vivo applications of SHED or DPSC for the repair and/or regeneration of non-dental tissues were included. The search strategy produced 2309 papers, from which 14 were eligible according to the predetermined inclusion and exclusion criteria. Although human tissue was the source of cells in half of the studies included in our review, all of the studies involved transplantation into animals of other species, such as pigs, rats and mice. Most of the manuscripts reported the successful use of DPSCs or SHED for non-dental tissue repair or regeneration. While these cell populations represent promising alternative sources of stem cells for tissue engineering and cell-based regenerative medicine therapies, it is not yet possible to guarantee the appropriate clinical management of this technique.

Isolation and processing of silk proteins for biomedical applications

Silk proteins of silkworms are chiefly composed of core fibroin protein and glycoprotein sericin that glues fibroin. Unique mechanical properties, cyto-compatibility and controllable biodegradability facilitate the use of fibroin in biomedical applications. Sericin serves as additive in cosmetic and food industries, as mitotic factor in cell culture media, anti-cancerous drug, anticoagulant and as biocompatible coating. For all these uses; aqueous solutions of silk proteins are preferred. Therefore, an accurate understanding of extraction procedure of silk proteins from their sources is critical. A number of protocols exist, amongst which it is required to settle a precise and easy one with desired yield and least down-stream processing. Here, we report extraction of proteins employing methods mentioned in literature using cocoons of mulberry and nonmulberry silks. This study reveals sodium carbonate salt-boiling system is the most efficient sericin extraction procedure for all silk variants. Lithium bromide is observed as the effective fibroin dissolution system for mulberry silk cocoons; whereas heterogeneous species-dependent result is obtained in case of nonmulberry species. We further show the effect of common post processing on nanoscale morphology of mulberry silk fibroin films. This knowledge eases the adoption and fabrication of silk biomaterials in devices and therapeutic delivery systems.

Chitosan-based scaffolds for bone tissue engineering

Bone defects requiring grafts to promote healing are frequently occurring and costly problems in health care. Chitosan, a biodegradable, naturally occurring polymer, has drawn considerable attention in recent years as scaffolding material in tissue engineering and regenerative medicine. Chitosan is especially attractive as a bone scaffold material because it supports the attachment and proliferation of osteoblast cells as well as formation of mineralized bone matrix. In this review, we discuss the fundamentals of bone tissue engineering and the unique properties of chitosan as a scaffolding material to treat bone defects for hard tissue regeneration. We present the common methods for fabrication and characterization of chitosan scaffolds, and discuss the influence of material preparation and addition of polymeric or ceramic components or biomolecules on chitosan scaffold properties such as mechanical strength, structural integrity, and functional bone regeneration. Finally, we highlight recent advances in development of chitosan-based scaffolds with enhanced bone regeneration capability.

Stem cells from fetal membranes and amniotic fluid: markers for cell isolation and therapy

Stem cell therapy is in constant need of new cell sources to conceive regenerative medicine approaches for diseases that are still without therapy. Scientists drew the attention toward amniotic membrane and amniotic fluid stem cells, since these sources possess many advantages: first of all as cells can be extracted from discarded foetal material it is inexpensive, secondly abundant stem cells can be obtained and finally, these stem cell sources are free from ethical considerations. Many studies have demonstrated the differentiation potential in vitro and in vivo toward mesenchymal and non-mesenchymal cell types; in addition the immune-modulatory properties make these cells a good candidate for allo- and xenotransplantation. This review offers an overview on markers characterisation and on the latest findings in pre-clinical or clinical setting of the stem cell populations isolated from these sources.

Osteochondral tissue engineering in vivo: a comparative study using layered silk fibroin scaffolds from mulberry and nonmulberry silkworms

The ability to treat osteochondral defects is a major clinical need. Existing polymer systems cannot address the simultaneous requirements of regenerating bone and cartilage tissues together. The challenge still lies on how to improve the integration of newly formed tissue with the surrounding tissues and the cartilage-bone interface. This study investigated the potential use of different silk fibroin scaffolds: mulberry (Bombyx mori) and non-mulberry (Antheraea mylitta) for osteochondral regeneration in vitro and in vivo. After 4 to 8 weeks of in vitro culture in chondro- or osteo-inductive media, non-mulberry constructs pre-seeded with human bone marrow stromal cells exhibited prominent areas of the neo tissue containing chondrocyte-like cells, whereas mulberry constructs pre-seeded with human bone marrow stromal cells formed bone-like nodules. In vivo investigation demonstrated neo-osteochondral tissue formed on cell-free multi-layer silk scaffolds absorbed with transforming growth factor beta 3 or recombinant human bone morphogenetic protein-2. Good bio-integration was observed between native and neo-tissue within the osteochondrol defect in patellar grooves of Wistar rats. The in vivo neo-matrix formed comprised of a mixture of collagen and glycosaminoglycans except in mulberry silk without growth factors, where a predominantly collagenous matrix was observed. Immunohistochemical assay showed stronger staining of type I and type II collagen in the constructs of mulberry and non-mulberry scaffolds with growth factors. The study opens up a new avenue of using inter-species silk fibroin blended or multi-layered scaffolds of a combination of mulberry and non-mulberry origin for the regeneration of osteochondral defects.

Dental pulp stem cells for in vivo bone regeneration: a systematic review of literature

OBJECTIVE

This review of literature was aimed to assess in vivo experiments which have evaluated the efficacy of dental pulp stem cells (DPSCs) for bone regeneration.

DESIGN

An electronic search of English-language papers was conducted on PubMed database. Studies that assessed the use of DPSCs in bone regeneration in vivo were included and experiments evaluating regeneration of hard tissues other than bone were excluded. The retrieved articles were thoroughly reviewed according to the source of stem cell, cell carrier, the in vivo experimental model, defect type, method of evaluating bone regeneration, and the obtained results. Further assessment of the results was conducted by classifying the studies based on the defect type.

RESULTS

Seventeen papers formed the basis of this systematic review. Sixteen out of 17 experiments were performed on animal models with mouse and rat being the most frequently used animal models. Seven out of 17 animal studies, contained subcutaneous pockets on back of the animal for stem cell implantation. In only one study hard tissue formation was not observed. Other types of defects used in the retrieved studies, included cranial defects and mandibular bone defects, in all of which bone formation was reported.

CONCLUSION

When applied in actual bone defects, DPSCs were capable of regenerating bone. Nevertheless, a precise conclusion regarding the efficiency of DPSCs for bone regeneration is yet to be made, considering the limited number of the in vivo experiments and the heterogeneity within their methods.

In vitro differentiation into insulin-producing β-cells of stem cells isolated from human amniotic fluid and dental pulp

AIM

To investigate the ability of human amniotic fluid stem cells and human dental pulp stem cells to differentiate into insulin-producing cells.

METHODS

Human amniotic fluid stem cells and human dental pulp stem cells were induced to differentiate into pancreatic β-cells by a multistep protocol. Islet-like structures were assessed in differentiated human amniotic fluid stem cells and human dental pulp stem cells after 21 days of culture by dithizone staining. Pancreatic and duodenal homebox-1, insulin and Glut-2 expression were detected by immunofluorescence and confocal microscopy. Insulin secreted from differentiated cells was tested with SELDI-TOF MS and by enzyme-linked immunosorbent assay.

RESULTS

Human amniotic fluid stem cells and human dental pulp stem cells, after 7 days of differentiation started to form islet-like structures that became evident after 14 days of induction. SELDI-TOF MS analysis, revealed the presence of insulin in the media of differentiated cells at day 14, further confirmed by enzyme-linked immunosorbent assay after 7, 14 and 21 days. Both stem cell types expressed, after differentiation, pancreatic and duodenal homebox-1, insulin and Glut-2 and were positively stained by dithizone. Either the cytosol to nucleus translocation of pancreatic and duodenal homebox-1, either the expression of insulin, are regulated by glucose concentration changes. Day 21 islet-like structures derived from both human amniotic fluid stem cells and human dental pulp stem cell release insulin in a glucose-dependent manner.

CONCLUSION

The present study demonstrates the ability of human amniotic fluid stem cells and human dental pulp stem cell to differentiate into insulin-producing cells, offering a non-pancreatic, low-invasive source of cells for islet regeneration.

Human amniotic fluid-derived and dental pulp-derived stem cells seeded into collagen scaffold repair critical-size bone defects promoting vascularization

Introduction

The main aim of this study is to evaluate potential human stem cells, such as dental pulp stem cells and amniotic fluid stem cells, combined with collagen scaffold to reconstruct critical-size cranial bone defects in an animal model.

Methods

We performed two symmetric full-thickness cranial defects on each parietal region of rats and we replenished them with collagen scaffolds with or without stem cells already seeded into and addressed towards osteogenic lineage in vitro. After 4 and 8 weeks, cranial tissue samples were taken for histological and immunofluorescence analysis.

Results

We observed a new bone formation in all of the samples but the most relevant differences in defect correction were shown by stem cell–collagen samples 4 weeks after implant, suggesting a faster regeneration ability of the combined constructs. The presence of human cells in the newly formed bone was confirmed by confocal analysis with an antibody directed to a human mitochondrial protein. Furthermore, human cells were found to be an essential part of new vessel formation in the scaffold.

Conclusion

These data confirmed the strong potential of bioengineered constructs of stem cell–collagen scaffold for correcting large cranial defects in an animal model and highlighting the role of stem cells in neovascularization during skeletal defect reconstruction.

Engineering bone tissue using human dental pulp stem cells and an osteogenic collagen-hydroxyapatite-poly (L-lactide-co-ε-caprolactone) scaffold

The aim of this study was to design a new natural/synthetic bioactive bone scaffold for potential use in bone replacement applications. We developed a tri-component osteogenic composite scaffold made of collagen (Coll), hydroxyapatite (HA) and poly(l-lactide-co-ε-caprolactone) (PLCL). This Coll/HA/PLCL composite scaffold was combined with human osteoblast-like cells obtained by differentiation of dental pulp stem cells (DPSCs) to engineer bone tissue in vitro. Results show that the 3D Coll/HA/PLCL composite scaffold was highly porous, thereby enabling osteoblast-like cell adhesion and growth. Cultured in the Coll/HA/PLCL scaffold, the osteoblast-like cells expressed different osteogenic genes, produced alkaline phosphatase and formed nodules more than did PLCL alone. Micro-CT analyses revealed a significant (30%) increase of tissue mineralisation on the surface as well as inside of the Coll/HA/PLCL scaffold, thus confirming its effectiveness as a bone regeneration platform.

Ferutinin promotes proliferation and osteoblastic differentiation in human amniotic fluid and dental pulp stem cells

AIMS

The phytoestrogen Ferutinin plays an important role in prevention of osteoporosis caused by ovariectomy-induced estrogen deficiency in rats, but there is no evidence of its effect on osteoblastic differentiation in vitro. In this study we investigated the effect of Ferutinin on proliferation and osteoblastic differentiation of two different human stem cells populations, one derived from the amniotic fluid (AFSCs) and the other from the dental pulp (DPSCs).

MAIN METHODS

AFSCs and DPSCs were cultured in a differentiation medium for 14 or 21days with or without the addition of Ferutinin at a concentration ranging from 10(-11) to 10(-4)M. 17β-Estradiol was used as a positive drug at 10(-8)M. Cell proliferation and expression of specific osteoblast phenotype markers were analyzed.

KEY FINDINGS

MTT assay revealed that Ferutinin, at concentrations of 10(-8) and 10(-9)M, enhanced proliferation of both AFSCs and DPSCs after 72h of exposure. Moreover, in both stem cell populations, Ferutinin treatment induced greater expression of the osteoblast phenotype markers osteocalcin (OCN), osteopontin (OPN), collagen I, RUNX-2 and osterix (OSX), increased calcium deposition and osteocalcin secretion in the culture medium compared to controls. These effects were more pronounced after 14days of culture in both populations.

SIGNIFICANCE

The enhancing capabilities on proliferation and osteoblastic differentiation displayed by the phytoestrogen Ferutinin make this compound an interesting candidate to promote bone formation in vivo.

The optimization of a scaffold for cartilage regeneration

Natural polymers offer various advantages in cartilage tissue engineering applications, thanks to their intrinsic bioactivity and adaptability, which can be exploited for the optimization of scaffold properties. In particular, silk fibroin has multifunctional features driven by the self-assembly of molecular subunits in appropriate environmental conditions. For these reasons, it was used in combination with hyaluronic acid to produce porous sponges for cartilage regeneration. The added amount of hyaluronic acid and the cross-linking with genipin modulated scaffold properties in a synergistic way, showing a strong inter-correlation among macroscopic and microscopic characteristics. Interestingly, hyaluronic acid affected silk fibroin conformation and induced a physical separation between the two material components in absence of genipin. Instead, this was prevented by the cross-linking reaction, resulting in a more interspersed network of protein and polysaccharide molecules partially resembling the structure of cartilage extracellular matrix. In addition, the systematic evaluation of sponge properties and how they can be modulated will represent a significant starting point for the interpretation of the complex outcomes driven by the scaffold in vitro and in vivo.

Human serum promotes osteogenic differentiation of human dental pulp stem cells in vitro and in vivo

Human dental pulp is a promising alternative source of stem cells for cell-based tissue engineering in regenerative medicine, for the easily recruitment with low invasivity for the patient and for the self-renewal and differentiation potential of cells. So far, in vitro culture of mesenchymal stem cells is usually based on supplementing culture and differentiation media with foetal calf serum (FCS). FCS is known to contain a great quantity of growth factors, and thus to promote cell attachment on plastic surface as well as expansion and differentiation. Nevertheless, FCS as an animal origin supplement may represent a potential means for disease transmission besides leading to a xenogenic immune response. Therefore, a significant interest is focused on investigating alternative supplements, in order to obtain a sufficient cell number for clinical application, avoiding the inconvenients of FCS use. In our study we have demonstrated that human serum (HS) is a suitable alternative to FCS, indeed its addition to culture medium induces a high hDPSCs proliferation rate and improves the in vitro osteogenic differentiation. Furthermore, hDPSCs-collagen constructs, pre-differentiated with HS-medium in vitro for 10 days, when implanted in immunocompromised rats, are able to restore critical size parietal bone defects. Therefore these data indicate that HS is a valid substitute for FCS to culture and differentiate in vitro hDPSCs in order to obtain a successful bone regeneration in vivo.

Clinical use of bone marrow, bone marrow concentrate, and expanded bone marrow mesenchymal stem cells in cartilage disease

Mesenchymal stem cells (MSCs) from bone marrow (BM) are widely used for bone and less for cartilage tissue regeneration due to their self-renewal and differentiating properties into osteogenic or chondrogenic lineages. This review considers the last decade of clinical trials involving a two-step procedure, by expanding in vitro MSCs from BM, or the so called "one-step" procedure, using BM in toto or BM concentrate, for the regeneration of cartilage and osteochondral tissue defects. The following conclusions were drawn: (1) Cartilage defects that can be repaired by the two-step technique are about twice the size as those where the one-step method is used; (2) the two-step procedure is especially used for the treatment of osteoarthritic lesions, whereas the one-step procedure is used for osteochondral defects; (3) the number of transplanted cells ranges between 3.8×10(6) and 11.2×10(6) cells/mL, and the period of cell culture expansion of implanted MSCs varies widely with regard to the two-step procedure; (4) hyaluronic or collagenic scaffolds are used in all the clinical studies analyzed for both techniques; (5) the follow-up of the two-step procedure is longer than that of the one-step method, despite having a lower number of patients; and, finally, (6) the mean age of the patients (about 39 years old) is similar in both procedures. Clinical results underline the safety and good and encouraging outcomes for the use of MSCs in clinics. Although more standardized procedures are required, the length of follow-up and the number of patients observed should be augmented, and the design of trials should be implemented to achieve evidence-based results.

CD117(+) amniotic fluid stem cells: state of the art and future perspectives

Broadly multipotent stem cells can be isolated from amniotic fluid by selection for the expression of the membrane stem cell factor receptor c-Kit, a common marker for multipotential stem cells. They have clonogenic capability and can be directed into a wide range of cell types representing the three primary embryonic lineages. Amniotic fluid stem cells maintained for over 250 population doublings retained long telomeres and a normal karyotype. Clonal human lines verified by retroviral marking were induced to differentiate into cell types representing each embryonic germ layer, including cells of adipogenic, osteogenic, myogenic, endothelial, neuronal and hepatic lineages. AFS cells could be differentiate toward cardiomyogenic lineages, when co-cultured with neonatal cardiomyocytes, and have the potential to generate myogenic and hematopoietic lineages both in vitro and in vivo. Very recently first trimester AFS cells could be reprogrammed without any genetic manipulation opening new possibilities in the field of fetal/neonatal therapy and disease modeling. In this review we are aiming to summarize the knowledge on amniotic fluid stem cells and highlight the most promising results.