Stem cell technology and bioceramics: from cell to gene engineering

Differentiation of bone marrow stromal cells into osteoblasts in a self-assembling peptide hydrogel: in vitro and in vivo studies

A prerequisite of tissue engineering approaches with regard to autograft is a suitable scaffold that can harbor cells and signals. Conventionally, such scaffolds have been prepared as 3D scaffolds prefabricated from synthetic or natural biomaterials. RAD16 has been introduced as a new biomaterial, where synthetic peptides self-assemble to form a hydrogel. In this study, RAD16 was examined in terms of osteogenic efficacy and feasibility of ectopic mineralization. Two hundred and seventy-one RAD16 was cocultured with 1 × 10(6) bone marrow cells from the femurs of 6-week-old Wistar male rats in alpha minimum essential medium supplemented with or without dexamethasone. Second, the same volume of the RAD16 construct hosting the cells with or without hydroxyapatite (HA) particles was treated in the dexamethasone medium as well, prepared in a Teflon tube, and implanted subcutaneously. Cell proliferation was prominent in the RAD16 coculture with dexamethasone at 1 week and significantly decreased by 2 weeks, whereas the other combinations remained or inclined, and their osteogenic differentiation was accelerated up to 2 weeks, as seen in increasing alkaline phosphatase (ALP) activity and mRNAs of ALP, OPN, and OCN. The RAD16 implant prepared with HA particles allowed more osteoblast-like cells and blood cells to grow inside, which was accompanied by elevating OPN gene expression and the stronger peak of VEGF gene expression at 2 weeks. Furthermore, more OPN mRNA signal was detected around the RAD16 containing HA particles by 4 weeks. On the other hand, the RAD16 alone represented lower expression of OPN gene. During the experiment, however, no ectopic mineralization was observed in both groups. Conclusively, it was suggested that the RAD16 showed feasibility of serving as a matrix for osteogenic differentiation of cocultured bone marrow cells in vitro and in vivo. Proceeding of exploration and modification of RAD16 are continuously required for cell-based tissue engineering.

Isolation and characterization of canine umbilical cord blood-derived mesenchymal stem cells

Human umbilical cord blood-derived mesenchymal stem cells (MSCs) are known to possess the potential for multiple differentiations abilities in vitro and in vivo. In canine system, studying stem cell therapy is important, but so far, stem cells from canine were not identified and characterized. In this study, we successfully isolated and characterized MSCs from the canine umbilical cord and its fetal blood. Canine MSCs (cMSCs) were grown in medium containing low glucose DMEM with 20% FBS. The cMSCs have stem cells expression patterns which are concerned with MSCs surface markers by fluorescence- activated cell sorter analysis. The cMSCs had multipotent abilities. In the neuronal differentiation study, the cMSCs expressed the neuronal markers glial fibrillary acidic protein (GFAP), neuronal class III beta tubulin (Tuj-1), neurofilament M (NF160) in the basal culture media. After neuronal differentiation, the cMSCs expressed the neuronal markers Nestin, GFAP, Tuj-1, microtubule-associated protein 2, NF160. In the osteogenic & chondrogenic differentiation studies, cMSCs were stained with alizarin red and toluidine blue staining, respectively. With osteogenic differentiation, the cMSCs presented osteoblastic differentiation genes by RT-PCR. This finding also suggests that cMSCs might have the ability to differentiate multipotentially. It was concluded that isolated MSCs from canine cord blood have multipotential differentiation abilities. Therefore, it is suggested that cMSCs may represent a be a good model system for stem cell biology and could be useful as a therapeutic modality for canine incurable or intractable diseases, including spinal cord injuries in future regenerative medicine studies.

Silk Fibroin Based Porous Materials

Silk from the Bombyx mori silkworm is a protein-based fiber. Bombyx mori silk fibroin (SF) is one of the most important candidates for biomedical porous material based on its superior machinability, biocompatibility, biodegradation, bioresorbability, and so on. In this paper, we have reviewed the key features of SF. Moreover we have focused on the morphous, technical processing, and biocompatibility of SF porous materials, followed by the application research. Finally, we provide a perspective the potential and problems of SF porous materials.

Restoration of cellular function of mesenchymal stem cells from a hypophosphatasia patient

Mesenchymal stem cells (MSCs) can differentiate into multiple cell lineages and are used for regenerative treatments for a variety of diseases. However, the patient's cells cannot be used to treat genetic diseases. Allogeneic cells can serve as an alternative but long-term survival is uncertain. Our experience of allo-transplantation to a patient with hypophosphatasia, which is caused by mutations of the tissue non-specific alkaline phosphatase (TNSALP) gene resulting in low serum alkaline phosphatase (ALP) activity and skeletal deformity, did not improve these clinical characteristics. Therefore, we sought to use autologous MSCs for the treatment of hypophosphatasia. MSCs derived from the patient's bone marrow had a similar profile when compared with well-reported MSCs. However, the MSCs had extremely low ALP activity and could not produce a mineralized bone matrix even under the osteogenic culture conditions. We therefore transduced a retroviral vector with TNSALP promoter-driven TNSALP gene in the MSCs. In the culture condition, the MSCs had about 7-fold higher ALP activity than did mock-transduced MSCs, and showed mineralization as well as bone-specific markers. Furthermore, the MSCs, but not mock-transduced MSCs, newly formed bone at the frequency of 50% in nude rats. Transplantation of the TNSALP-transduced autologous MSCs might become a new therapy for hypophosphatasia.

Hard tissue-forming potential of stem/progenitor cells in human dental follicle and dental papilla

OBJECTIVE

The existence of stem/progenitor cells in dental tissue has been suggested but their characterization in the human tooth germ remains elusive. The purpose of this study was to investigate these cells in human dental follicles and dental papillae at the crown-forming stage and compare their potential for hard tissue formation.

DESIGN

We used dental follicle cells (DFCs) and dental papilla cells (DPCs) derived from dental follicles and dental papillae at the crown-forming stage and compared their proliferative capacity, cell surface antigens and ability to form hard tissue in vitro and in vivo.

RESULTS

Both DFCs and DPCs had extensive proliferation ability, expressed similar cell surface antigens and were capable of forming hard tissue in vivo as well as in vitro. However, there were two differences between DFCs and DPCs. First, DPCs had a significantly higher calcium accumulation than that in DFCs. Second, DFCs expressed a cementoblast marker, whereas DPCs expressed an odontoblast marker.

CONCLUSIONS

We propose that dental follicles and dental papillae at the crown-forming stage contain different types of stem/progenitor cells and may have hard tissue-forming ability in a possibly origin-specific lineage direction.

Mechanisms involved in the therapeutic properties of mesenchymal stem cells

Mesenchymal stem cells (MSCs) have been described as being able to give rise to several quite different mesenchymal cell phenotypes. However, the ability to differentiate is not the only characteristic that makes these cells attractive for therapeutic purposes. The secretion of a broad range of bioactive molecules by MSCs, such as growth factors, cytokines and chemokines, constitutes their most biologically significant role under injury conditions. Understanding this intricate secretory activity as well as the properties of MSCs in vivo is central to harnessing their clinical potential. Herein, we identify some of the molecules involved in the paracrine effects of MSCs with a perspective that these cells intrinsically belong to a perivascular niche in vivo, and discuss how this knowledge could be advantageously used in clinical applications.

Bone grafts cultured with bone marrow stromal cells for the repair of critical bone defects: an experimental study in mice

Tissue engineering of autologous bone combined with osteoprogenitor cells is a suitable strategy for filling large bone defects. The aim of this study was to evaluate the osteogenicity of a xenogenic bone graft cultured with allogenic bone marrow stromal cells (BMSC) in a mouse critical size craniotomy. Bovine trabecular bone grafts were made free of bone marrow cells or debris and were delipidated. BMSC were harvested from C57BL/6-Tg(ACTbEGFP)1Osb/J mice (GFP+ cells) and were cultured 14 days on bone grafts in control or osteogenic medium. Engineered grafts were implanted in calvarial defect in C57BL/6 mice. Four groups were studied: graft with BMSC differentiated in osteoblasts (G-Ob), graft with BMSC (G-BMSC), graft without cells (G) and no graft. Calvariae were studied 2 and 8 weeks after implantation by radiographic and histomorphometric analyses. G group: the bone ingrowth was limited to the edges of the defect. The center of the graft was filled by a fibrovascular connective tissue. G-BMSC or G-Ob groups: bone formation occurred early in the center of the defect and did not increase between 2 and 8 weeks; the newly formed woven bone was partially replaced by lamellar bone. The preoperative osteoblastic differentiation of BMSC did not allow faster and better bone regeneration. After 2 weeks, GFP+ cells were observed around the grafted bone but no GFP+ osteocyte was present in the newly formed bone. No GFP+ cell was noted after 8 weeks. However, pre-implantation culture of the biomaterial with allogenic BMSC greatly enhanced the bone regeneration.

Osteocalcin secretion as an early marker of in vitro osteogenic differentiation of rat mesenchymal stem cells

Osteocalcin (OC) is a bone-specific protein synthesized by osteoblasts that represents a good marker for osteogenic maturation. We examined whether in vitro osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (MSCs) could be simply assessed at earlier stages by monitoring OC secretion into the conditioned medium, rather than measuring OC deposition on the extracellular matrix (ECM), using a sandwich enzyme immunoassay system involving a specific anti-rat OC monoclonal antibody. During a 16-day culture, OC was secreted into the medium of MSCs from day 8 and increased substantially until day 16. In contrast, OC deposition on the ECM was low, even at day 13, when calcium deposition was at high levels. The histological expression pattern of OC messenger RNA provided in situ evidence that osteoblastic cells appeared at the early stages of 6 to 9 days and matured over time in vitro. Furthermore, the temporal expression of osteogenesis-specific genes, such as the transcriptional factors core-binding factor 1 and osterix, followed by increases in secretory OC proved the commitment of MSCs to osteoblastic differentiation. These results revealed that biomineralization followed secretion of OC, which may reflect early osteoblastic differentiation of cultured MSCs under osteoinductive conditions. We ascertained the osteogenic differentiation capacity of cultured MSCs in a non-destructive manner by monitoring OC secretion into the culture medium and proved that secretory OC could represent a reliable marker for predicting in vivo osteogenic potential in bone tissue engineering.

Growth and osteogenic differentiation of adipose stem cells on PLA/bioactive glass and PLA/beta-TCP scaffolds

The aim of this study was to compare the effects of novel three-dimensional composite scaffolds consisting of a bioactive phase (bioactive glass or beta-tricalcium phosphate [beta-TCP] 10 and 20 wt%) incorporated within a polylactic acid (PLA) matrix on viability, distribution, proliferation, and osteogenic differentiation of human adipose stem cells (ASCs). The viability and distribution of ASCs on the bioactive composite scaffolds was evaluated using Live/Dead fluorescence staining, environmental scanning electron microscopy, and scanning electron microscopy. There were no differences between the two concentrations of bioactive glass and beta-TCP in PLA scaffolds on proliferation and osteogenic differentiation of ASCs. After 2 weeks of culture, DNA content and alkaline phosphatase (ALP) activity of ASCs cultured on PLA/beta-TCP composite scaffolds were higher relative to other scaffold types. Interestingly, the cell number was significantly lower, but the relative ALP/DNA ratio of ASCs was significantly higher in PLA/bioactive glass scaffolds than in other three scaffold types. These results indicate that the PLA/beta-TCP composite scaffolds significantly enhance ASC proliferation and total ALP activity compared to other scaffold types. This supports the potential future use of PLA/beta-TCP composites as effective scaffolds for tissue engineering and as bone replacement materials.

Scaffold design and manufacturing: from concept to clinic

Since Robert Langer and colleagues pioneered the concept of reconstructing tissue using cells transplanted on synthetic polymer matrices in the early 1990s, research in the field of tissue engineering and regenerative medicine has exploded. This is especially true in the development of new materials and structures that serve as scaffolds for tissue reconstruction. The basic tenet of the last two decades holds scaffolds as degradable materials providing temporary function while enhancing tissue regeneration through the delivery of biologics. Although a number of new scaffolding materials and structures have been developed in research laboratories, the application of such materials practice even has been extremely limited. This paper argues that better integration of all these factors is needed to bring scaffolds from "concept to clinic". It reviews current work in all these areas and suggests where future work and funding is needed.

Apatite-coated silk fibroin scaffolds to healing mandibular border defects in canines

Tissue engineering has become a new approach for repairing bony defects. Highly porous osteoconductive scaffolds perform the important role for the success of bone regeneration. By biomimetic strategy, apatite-coated porous biomaterial based on silk fibroin scaffolds (SS) might provide an enhanced osteogenic environment for bone-related outcomes. To assess the effects of apatite-coated silk fibroin (mSS) biomaterials for bone healing as a tissue engineered bony scaffold, we explored a tissue engineered bony graft using mSS seeded with osteogenically induced autologous bone marrow stromal cells (bMSCs) to repair inferior mandibular border defects in a canine model. The results were compared with those treated with bMSCs/SS constructs, mSS alone, SS alone, autologous mandibular grafts and untreated blank defects. According to radiographic and histological examination, new bone formation was observed from 4 weeks post-operation, and the defect site was completely repaired after 12 months for the bMSCs/mSS group. In the bMSCs/SS group, new bone formation was observed with more residual silk scaffold remaining at the center of the defect compared with the bMSCs/mSS group. The engineered bone with bMSCs/mSS achieved satisfactory bone mineral densities (BMD) at 12 months post-operation close to those of normal mandible (p>0.05). The quantities of newly formed bone area for the bMSCs/mSS group was higher than the bMSCs/SS group (p<0.01), but no significant differences were found when compared with the autograft group (p>0.05). In contrast, bony defects remained in the center with undegraded silk fibroin scaffold and fibrous connective tissue, and new bone only formed at the periphery in the groups treated with mSS or SS alone. The results suggested that apatite-coated silk fibroin scaffolds combined with bMSCs could be successfully used to repair mandibular critical size border defects and the premineralization of these porous silk fibroin protein scaffolds provided an increased osteoconductive environment for bMSCs to regenerate sufficient new bone tissue.

In vivo osteogenic capability of human mesenchymal cells cultured on hydroxyapatite and on beta-tricalcium phosphate

The aim of the current study was to examine in vitro osteogenic capability and in vivo bone formation of mesenchymal stromal cells (MSCs) on two kinds of calcium phosphate ceramics. MSCs derived from human bone marrow were seeded on either hydroxyapatite (HA) ceramic or beta-tricalcium phosphate (beta-TCP) ceramic and then cultured in a medium supplemented with a donor's serum, vitamin C, beta-glycerophosphate, and dexamethasone. The culture revealed the expression of alkaline phosphatase activity, indicating the osteogenic differentiation of the MSCs on the ceramics (fabrication of tissue-engineered construct). The constructs were then implanted subcutaneously into nude rats for 8 weeks. New bone formation was observed in both types of ceramics, and human-specific Alu sequence was detected by in situ hybridization analysis. Quantitative microcomputed tomography showed that the volume of the new bone in the HA ceramic was greater than that in the beta-TCP ceramic in six of seven cases. These results suggest that human MSCs cultured on ceramics could retain their osteogenic capability even after ectopic implantation and provide a rationale for the use of tissue-engineered constructs derived from a patient's MSCs and calcium phosphate ceramics in bone tissue regeneration.

Injectable Poly(ethylene glycol) Dimethacrylate-based Hydrogels with Hydroxyapatite

Injectable hydrogels are attractive materials for tissue engineering as they provide fast reaction rates, low heat release, and biocompatibility for cell proliferation and permanent interface with surrounding tissue. A series of injectable poly(ethylene glycol) dimethacrylate (PEGDMA) hydrogels with four different weight fractions of hydroxyapatite (HA) particles were prepared and thermal and mechanical properties evaluated. The cytocompatibility was assessed by examining the viability and morphology of human mesenchymal stem cells (hMSCs) seeded on the hydrogels. The in situ crosslink process displayed a vast decrease in the maximal temperature and an increase in the maximal temperature time. Cytocompatibility evaluation by MTT assay, scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) showed that the cells on the composite hydrogels possessed better viability and adherence than the hydrogels without HA. The results indicated that composite hydrogels have potential as injectable materials for tissue engineering application.

Tissue engineering of bone

Despite well-established bone-grafting techniques, large bone defects still represent a challenge for orthopaedic and reconstructive surgeons. Efforts have therefore been made to develop osteoconductive, osteoinductive and osteogenic bone-replacement systems. According to its original definition, tissue engineering is an 'interdisciplinary field that applies the principles of engineering and the life sciences toward the development of biological substitutes that restore, maintain, or improve tissue function'. It is based on the understanding of tissue formation and regeneration, and aims to grow new functional tissues rather than to build new spare parts. This review focuses on the principles of tissue engineering applied to the creation of bioartificial bone tissue. Important aspects, such as osteogenic cells, matrix materials, inter- and intra-cellular communication, growth factors, gene therapy and current concepts of bone tissue engineering are reviewed. First clinical applications are discussed. An outlook provides insight into the possible future perspectives of bone tissue engineering.

Effect of human umbilical cord blood-derived mesenchymal stem cells in a cirrhotic rat model

BACKGROUND/AIM

Cirrhosis is a long-term consequence of chronic hepatic injury and no effective therapy is currently available for this disease. Recent reports have shown that the mesenchymal stem cells (MSCs) have the capacity to differentiate into hepatocytes, and umbilical cord blood is a rich source of MSCs. Hence, we investigated the effect of infusing of human umbilical cord blood-derived MSCs (HMSCs) in carbon tetrachloride (CCl4)-induced cirrhosis in a rat model.

METHODS

The effect of HMSCs on cirrhosis was evaluated using haematoxylin and eosin and Masson's trichrome staining. To evaluate cirrhosis-related factors, we measured protein and mRNA expression of transforming growth factor beta1 (TGF-beta1), collagen type I and alpha-smooth muscle actin (alpha-SMA).

RESULTS

Histological findings showed that liver fibrosis in rats was alleviated by HMSCs infusion. Interestingly, CM-DiI-labelled HMSCs expressed the hepatocyte-specific markers, human albumin and alpha-fetoprotein. Infusion of HMSCs significantly inhibited TGF-beta1, collagen type I and alpha-SMA expressions in CCl4-induced cirrhotic rats.

CONCLUSION

Our results showed that HMSCs infusion could improve liver fibrosis in rats with CCl4-induced cirrhosis, raising the possibility for clinical use of HMSCs in the treatment of cirrhosis.

Stem cell property of postmigratory cranial neural crest cells and their utility in alveolar bone regeneration and tooth development

The vertebrate neural crest is a multipotent cell population that gives rise to a variety of different cell types. We have discovered that postmigratory cranial neural crest cells (CNCCs) maintain mesenchymal stem cell characteristics and show potential utility for the regeneration of craniofacial structures. We are able to induce the osteogenic differentiation of postmigratory CNCCs, and this differentiation is regulated by bone morphogenetic protein (BMP) and transforming growth factor-beta signaling pathways. After transplantation into a host animal, postmigratory CNCCs form bone matrix. CNCC-formed bones are distinct from bones regenerated by bone marrow mesenchymal stem cells. In addition, CNCCs support tooth germ survival via BMP signaling in our CNCC-tooth germ cotransplantation system. Thus, we conclude that postmigratory CNCCs preserve stem cell features, contribute to craniofacial bone formation, and play a fundamental role in supporting tooth organ development. These findings reveal a novel function for postmigratory CNCCs in organ development, and demonstrate the utility of these CNCCs in regenerating craniofacial structures.

The effect of implantation on scaffoldless three-dimensional engineered bone constructs

Our laboratory has previously developed scaffoldless engineered bone constructs (EBC). Bone marrow stromal cells (BMSC) were harvested from rat femur and cultured in medium that induced osteogenic differentiation. After reaching confluence, the monolayer of cells contracted around two constraint points forming a cylinder. EBCs were placed in small diameter (0.5905 x 0.0625 in.) or large diameter (0.5905 x 0.125 in.) silicone tubing and implanted intramuscularly in the hind limb of a rat. Bone mineral content (BMC) of the EBC was analyzed before implantation and at 1 and 2 mo following implantation and compared to that of native femur bone at different stages of development. Negligible BMC was observed in E-20 femur or EBCs prior to implantation. One-month implantation in both small and large tubing increased BMC in the EBC. BMC of EBC from large tubing was greater than in 14 d rat neonatal femurs, but was 2% and 3% of BMC content in adult bone after 1 and 2 mo of implantation, respectively. Alizarine Red and osteopontin staining of the EBCs before and after implantation confirmed increased bone mineralization in the implanted EBCs. Implanted EBCs also had extensive vascularization. Our data suggest that BMSC can be successfully used for the generation of scaffoldless EBC, and this model can be potentially used for the generation of autologous bone transplants in humans.

Mandibular repair in rats with premineralized silk scaffolds and BMP-2-modified bMSCs

Premineralized silk fibroin protein scaffolds (mSS) were prepared to combine the osteoconductive properties of biological apatite with aqueous-derived silk scaffold (SS) as a composite scaffold for bone regeneration. The aim of present study was to evaluate the effect of premineralized silk scaffolds combined with bone morphogenetic protein-2 (BMP-2) modified bone marrow stromal cells (bMSCs) to repair mandibular bony defects in a rat model. bMSCs were expanded and transduced with adenovirus AdBMP-2, AdLacZ gene in vitro. These genetically modified bMSCs were then combined with premineralized silk scaffolds to form tissue-engineered bone. Mandibular repairs with AdBMP-2 transduced bMSCs/mSS constructs were compared with those treated with AdLacZ-transduced bMSCs/mSS constructs, native (nontransduced) bMSCs/mSS constructs and mSS alone. Eight weeks after post-operation, the mandibles were explanted and evaluated by radiographic observation, micro-CT, histological analysis and immunohistochemistry. The presence of BMP-2 gene enhanced tissue-engineered bone in terms of the most new bone formed and the highest local bone mineral densities (BMD) found. These results demonstrated that premineralized silk scaffold could serve as a potential substrate for bMSCs to construct tissue-engineered bone for mandibular bony defects. BMP-2 gene therapy and tissue engineering techniques could be used in mandibular repair and bone regeneration.

New bone formation by allogeneic mesenchymal stem cell transplantation in a patient with perinatal hypophosphatasia

Mesenchymal stem cells (MSCs) can show osteogenic differentiation capability when implanted in vivo, as well as cultured in vitro; therefore we attempted to use allogeneic MSCs for an 8-month-old patient with hypophosphatasia. MSCs were obtained by culture expansion of fresh marrow from the patient's father. Some of the MSCs were further cultured under osteogenic conditions on a culture dish or porous hydroxyapatite ceramics, resulting in cultured osteoblasts and osteogenic constructs, respectively. The MSCs and osteoblasts were injected into the patient, and the constructs were implanted locally. After traditional bone marrow transplantation, the MSCs, osteoblasts, and osteogenic constructs were used for treatment and to improve the patient's respiratory condition and skeletal abnormality. The condition worsened again, and an MSC booster shot was administered. At the same time, the construct was retrieved. The respiratory condition improved, and the retrieved construct showed de novo bone derived from both donor and patient cells. We demonstrated the importance of allogeneic MSC transplantation for hypophosphatasia and the constructs as an alternative to bone fragments that provided further osteogenic capability in the patient.

Erythropoietin augments the efficacy of therapeutic angiogenesis induced by allogenic bone marrow stromal cells in a rat model of limb ischemia

Transplantation of adult marrow stromal cells (MSCs) has been developed as a new method of treating severe ischemia diseases by therapeutic angiogenesis. Erythropoietin (EPO) is capable of inducing angiogenesis and inhibiting MSCs apoptosis. The effect of EPO on the therapeutic potency of MSCs transplantation in a rat model of limb ischemia was investigated in the current study. The results indicate that the combined treatment with MSC transplantation and EPO infusion is superior to MSC transplantation alone in the treatment of limb ischemia. MSCs transplantation and EPO infusion could enhance the angiogenic effect of each other to achieve a better therapeutic effect. This combination therapy may become a more effective approach for ischemia diseases of the limbs.

Cell therapy for bone regeneration--bench to bedside

The concept of bone tissue engineering, which began in the early 1980s, has seen tremendous growth in the numbers of research studies. One of the key areas of research has been in the field of mesenchymal stem cells, where the challenge is to produce the perfect tissue-engineered bone construct. This practical review summarizes basic and applied state-of-the-art research in the area of mesenchymal stem cells, and highlights the important translational research that has already been initiated. The topics that will be covered include the sources of stem cells in use, scaffolds, gene therapy, clinical applications in nonunions, tumors, osteonecrosis, revision arthroplasties, and spine fusion. Although significant challenges remain, there exists an exceptional opportunity to translate basic research in mesenchymal stem cell technologies into viable clinical treatments for bone regeneration.

Effect of dynamic 3-D culture on proliferation, distribution, and osteogenic differentiation of human mesenchymal stem cells

Ex vivo engineering of autologous bone tissue as an alternative to bone grafting is a major clinical need. In the present study, we evaluated the effect of 3-D dynamic spinner flask culture on the proliferation, distribution, and differentiation of human mesenchymal stem cells (MSCs). Immortalized human MSCs were cultured on porous 75:25 PLGA scaffolds for up to 3 weeks. Dynamically cultured cell/scaffold constructs demonstrated a 20% increase in DNA content (21 days), enhanced ALP specific activity (7 days and 21 days), a more than tenfold higher Ca2+ content (21 days), and significantly increased transcript levels of early osteogenesis markers (e.g., COL1A1, BMP2, RUNX-2) as compared with static culture. Despite the formation of a dense superficial cell layer, markedly increased cell ingrowth was observed by fluorescence microscopy on day 21. Furthermore, increased extracellular matrix deposition was visualized by scanning electron microscopy after 1 and 3 weeks of dynamic culture. The observed increased ingrowth and osteogenic differentiation of 3-D dynamically cultured human MSCs can be explained by generation of fluid shear stress and enhanced mass transport to the interior of the scaffold mimicking the native microenvironment of bone cells. This study provides evidence for the effectiveness of dynamic culture of human MSCs during the initial phase of ex vivo osteogenesis.

Biomaterial effects in articular cartilage tissue engineering using polyglycolic acid, a novel marine origin biomaterial, IGF-I, and TGF-beta 1

Bovine articular chondrocytes were seeded on either polyglycolic acid (PGA) non-woven mesh scaffolds or a biomatrix from the species Porites lutea (POR). These constructs were cultured for 6 weeks in the presence of insulin-like growth factor (IGF)-I (10 ng/ml or 100 ng/ml) or transforming growth factor (TGF)-beta 1 (5 ng/ml or 30 ng/ml) to determine the in-vitro articular cartilage regeneration capacity of each. Histology, deoxyribonucleic acid content, collagen I and II (immunohistochemistry and enzyme-linked immunosorbent assay), and glycosaminoglycan (GAG) contents were measured at 0 weeks, 2 weeks, and 6 weeks to assess the characteristics of chondrogenesis. Both scaffolds supported the maintenance of the chondrocytic phenotype, as evidenced by the predominance of collagen II and the presence of rounded chondrocytes embedded in lacunae. Regardless of growth factor treatment, cells cultured on PGA scaffolds produced more collagen type II than those cultured on POR. Conversely, by 6 weeks, cells cultured on POR scaffolds produced more GAG than those cultured on PGA scaffolds, again regardless of the growth factor used. Across the two groups, 100 ng/ml of IGF-I had the greatest overall effect in GAG content. This work indicates that PGA and the POR scaffolds are both effective growth matrices for articular cartilage, with each scaffold exhibiting different yet desirable profiles of articular cartilage growth.

Rotating three-dimensional dynamic culture of adult human bone marrow-derived cells for tissue engineering of hyaline cartilage

The method of constructing cartilage tissue from bone marrow-derived cells in vitro is considered a valuable technique for hyaline cartilage regenerative medicine. Using a rotating wall vessel (RWV) bioreactor developed in a NASA space experiment, we attempted to efficiently construct hyaline cartilage tissue from human bone marrow-derived cells without using a scaffold. Bone marrow aspirates were obtained from the iliac crest of nine patients during orthopedic operation. After their proliferation in monolayer culture, the adherent cells were cultured in the RWV bioreactor with chondrogenic medium for 2 weeks. Cells from the same source were cultured in pellet culture as controls. Histological and immunohistological evaluations (collagen type I and II) and quantification of glycosaminoglycan were performed on formed tissues and compared. The engineered constructs obtained using the RWV bioreactor showed strong features of hyaline cartilage in terms of their morphology as determined by histological and immunohistological evaluations. The glycosaminoglycan contents per microg DNA of the tissues were 10.01 +/- 3.49 microg/microg DNA in the case of the RWV bioreactor and 6.27 +/- 3.41 microg/microg DNA in the case of the pellet culture, and their difference was significant. The RWV bioreactor could provide an excellent environment for three-dimensional cartilage tissue architecture that can promote the chondrogenic differentiation of adult human bone marrow-derived cells.

Biomaterial technology for tissue engineering applications

Tissue engineering is a newly emerging biomedical technology and methodology to assist and accelerate the regeneration and repairing of defective and damaged tissues based on the natural healing potentials of patients themselves. For the new therapeutic strategy, it is indispensable to provide cells with a local environment that enhances and regulates their proliferation and differentiation for cell-based tissue regeneration. Biomaterial technology plays an important role in the creation of this cell environment. For example, the biomaterial scaffolds and the drug delivery system (DDS) of biosignalling molecules have been investigated to enhance the proliferation and differentiation of cell potential for tissue regeneration. In addition, the scaffold and DDS technologies contribute to develop the basic research of stem cell biology and medicine as well as obtain a large number of cells with a high quality for cell transplantation therapy. A technology to genetically engineer cells for their functional manipulation is also useful for cell research and therapy. Several examples of tissue engineering applications with the cell scaffold and DDS of growth factors and genes are introduced to emphasize the significance of biomaterial technology in new therapeutic and research fields.

Quantifying the 3D macrostructure of tissue scaffolds

The need to shift from tissue replacement to tissue regeneration has led to the development of tissue engineering and in situ tissue regeneration. Both of these strategies often employ the use of scaffolds--templates that allow cells to attach and then guide the new tissue growth. There are many design criteria for an ideal scaffold. These criteria vary depending on the tissue type and location in the body. In any application of a scaffold it is vital to be able to characterise the scaffold before it goes into in vitro testing. In vitro testing allows the cell response to be investigated before its in vivo performance is assessed. A full characterisation of events in vitro and in vivo, in three dimensions (3D), is necessary if a scaffold's performance and effectiveness is to be fully quantified. This paper focuses on porous scaffolds for bone regeneration, suggests appropriate design criteria for a bone regenerating scaffold and then reviews techniques for obtaining the vitally important quantification of its pore structure. The techniques discussed will include newly developed methods of quantifying X-ray microtomography (microCT) images in 3D and for predicting the scaffolds mechanical properties and the likely paths of fluid flow (and hence potential cell migration). The complications in investigating scaffold performance in vitro are then discussed. Finally, the use of microCT for imaging scaffolds for in vivo tests is reviewed.

Ectopic osteogenesis and hematopoiesis after implantantion of bone marrow cells seeded on HAP/PLLA scaffold

Bone tissue reconstruction and reparation is a big challenge in medicine. Biocomposite materials based on hidroxyapatite are widely used in reparation of bone defects. Adult bone marrow-derived stem cells may be considered in two categories: hematopoietic stem cells (HSC) from the bone marrow and mesenchymal stem cells from the bone marrow stroma (BMSC). HSC and BMSC do not only coexist in one organ, but functionally cooperate. BMSC have a critical role in the formation of hematopoietic microenvironment (HME). The aim of this study was to investigate the interactions between bone marrow cells and biocomposites based on HAp/PLLA (hidroxyapatite/poly-L-lactide) after subcutaneous implantation in Balb/c mice. In that purpose, bone marrow cells of Balb/c mice were seeded in HAp/PLLA tubes (15 mm?1,5 mm). The HAp/PLLA tubes with BMC was subcutaneously implanted with a needle into the intrascapsular region of the mouse. Implants were extracted after 2, 6 and 12 weeks. In implants after 2 and 6 weeks we found angiogenesis, collagenogenesis and new bone. Ectopic hematopoiesis was seen in implants after 12 weeks from implantation. As a good scaffold in the role of supporting osteogenesis and hematopoiesis, biocomposites HAp/PLLA can be good bone substitute materials in the bone reparation process. These results showed that the HAp/PLLA scaffold owned biological properties comparable to natural bone.

Interconnected porous hydroxyapatite ceramics for bone tissue engineering

Several porous calcium hydroxyapatite (HA) ceramics have been used clinically as bone substitutes, but most of them possessed few interpore connections, resulting in pathological fracture probably due to poor bone formation within the substitute. We recently developed a fully interconnected porous HA ceramic (IP-CHA) by adopting the 'foam-gel' technique. The IP-CHA had a three-dimensional structure with spherical pores of uniform size (average 150 microm, porosity 75%), which were interconnected by window-like holes (average diameter 40 microm), and also demonstrated adequate compression strength (10-12 MPa). In animal experiments, the IP-CHA showed superior osteoconduction, with the majority of pores filled with newly formed bone. The interconnected porous structure facilitates bone tissue engineering by allowing the introduction of mesenchymal cells, osteotropic agents such as bone morphogenetic protein or vasculature into the pores. Clinically, we have applied the IP-CHA to treat various bony defects in orthopaedic surgery, and radiographic examinations demonstrated that grafted IP-CHA gained radiopacity more quickly than the synthetic HA in clinical use previously. We review the accumulated data on bone tissue engineering using the novel scaffold and on clinical application in the orthopaedic field.

A comparison between bone reconstruction following the use of mesenchymal stem cells and total bone marrow in association with calcium phosphate scaffold in irradiated bone

The purpose of this study was to compare bone reconstruction using either mesenchymal stem cells (MSCs) or total bone marrow (TBM) in association with biphasic calcium phosphate (BCP) granules after irradiation in a rat model. Three weeks after an external irradiation of the hind limbs of rats, four bone defects were created per animal. The defects were filled with either BCP alone, or with a mixture of BCP and TBM, or with a mixture of BCP and MSCs (adipose-derived or bone marrow-derived MSCs). Three weeks after implantations, new-bone formation was assessed. Histological examination showed osteoconductive and osteointegrative properties of BCP in irradiated tissue. The BCP-TBM mixture significantly improved bone ingrowth (p<0.05). The BCP-MSCs mixtures did not provide new-bone formation over and above that induced by BCP alone. This gives grounds for suspecting that there is a link between this result and the cellular and vascular weakness observed in irradiated bone. The BCP-TBM mixture may have induced an increased vascularization of irradiated bone. This could be due to the presence of all components in TBM that were lacking in the BCP-MSCs mixtures. BCP associated with TBM appears to be the most efficient material for bone substitution in irradiated areas.

Isolation of osteoprogenitors from murine bone marrow by selection of CD11b negative cells

Selection of cells having the most osteogenic potential is a strategy used in bone tissue engineering. Preclinical studies using murine bone marrow cells must consider the large amount of hematopoietic cells in the adherent fraction. The aim of this study was to enrich a murine bone marrow cell population with osteoprogenitors by using a simple and reliable method. Bone marrow from C57Bl/6 mice was extracted and cells which adhered onto plastic were expanded in primary culture for 14 days. Immunolabeling of the CD11b surface antigen was performed and the CD11b(-) cell fraction was isolated by FACS. Sorted and unsorted populations were analyzed for gene expression of osteoblast differentiation, alkaline phosphatase (AlkP) activity and matrix mineralization capacities. Selection of CD11b(-) cells increased the number of AlkP(+) cells from the plastic adherent fraction from 6.3% +/- 0.8 to 56% +/- 3.3 with a sevenfold increase in AlkP activity. mRNA analysis revealed a significant increase in the CD11b(-) fraction for Osterix (41-fold), RANKL (17-fold), M-CSF (8-fold) and Runx-2 (8-fold). An osteogenic population was obtained with improved capacities to produce a mineralized extracellular matrix in vitro, independently of the presence of glucocorticoids in the culture medium.

Porosity and pore size of beta-tricalcium phosphate scaffold can influence protein production and osteogenic differentiation of human mesenchymal stem cells: an in vitro and in vivo study

The interaction of stem cells and ceramics in bone regeneration is still poorly understood. The aim of this study was to examine the influence of the porosity (25%, 65% and 75%) of beta-tricalcium phosphate (TCP) ceramics on osteogenic differentiation of mesenchymal stem cells (MSC) in vitro and in vivo. For the in vitro portion of the study, TCP scaffolds loaded with MSC were kept in osteogenic induction medium for 21 days. For the in vivo portion of the study, scaffolds loaded with undifferentiated MSC were implanted subcutaneously into SCID mice for 8 weeks and compared with similarly implanted controls that were not loaded with MSC. Measurements of total protein as well as specific alkaline phosphatase (ALP) activity were taken as indicators of growth/matrix production and osteogenic differentiation. An increase in the total protein concentration was noted from day 1 to day 21 on the in vitro TCP 65% and TCP 75% scaffolds (p<0.05) with no such increase noted in the TCP 25% specimens. However, the specific alkaline phosphatase activity increased from day 1 to day 21 in all three in vitro specimens (p<0.02) and reached similar levels in each specimen by day 21. In vivo, ALP activity of cell-loaded TCP 65% ceramics was higher when compared with both the TCP 25% and TCP 75% specimens (p<0.046), and higher in the TCP 75% than TCP 25% specimens (p=0.008). Histology revealed mineralization by human cells in the pores of the TCP ceramic scaffolds with a trend toward greater calcification in TCP 65% and 75%. In summary, a higher porosity of TCP scaffolds does not necessarily mean a higher ALP activity in vivo. The distribution and size of the pores, as well as the surface structure, might play an important role for osteogenic differentiation in vivo.

Bone marrow-derived mesenchymal cells can rescue osteogenic capacity of devitalized autologous bone

In clinical cases, many orthopaedists have been troubled with bone fragility, such as fractures after devitalization therapy for bone tumour, pathological fractures and metastatic tumours. The aim of this study was to determine whether loss of osteogenic capacity of devitalized autologous bones can be rescued using cultured bone marrow-derived mesenchymal cells. A devitalized bone model was produced from rat femur by irradiation and three groups were prepared: intact bone, irradiated bone and irradiated bone combined with cultured mesenchymal cells. Each bone was transplanted subcutaneously into a syngeneic rat. At 2 or 4 weeks after transplantation, biochemical analyses [alkaline phosphatase (ALP) activity and osteocalcin mRNA expression] and histological measurement were performed. Moreover, we verified the origin of newly formed bone, using the sex-determining region Y (sry) gene as a marker to distinguish between donor and recipient. In both intact bone and irradiated bone with mesenchymal cells, ALP activity and osteocalcin mRNA expression were detected and living osteoblasts together with newly formed bone were clearly seen histologically. Furthermore, analysis of the origin of de novo formed bone indicated that newly formed bone in irradiated bone with mesenchymal cells was derived from cultured bone marrow-derived mesenchymal cells. These results proved that the osteogenic capacity of devitalized autologous bone can be rescued using tissue-engineering techniques. This procedure should contribute to various clinical treatments, such as local metastatic tumours, pathological fracture after devitalization therapy and reconstruction after wide-margin tumour resection. The benefits would be applicable to all types of devitalized bone.

Human mesenchymal stem cells as a stable source of VEGF-producing cells

Vascular endothelial growth factor (VEGF) is a positive regulator and plays a crucial role in angiogenesis. We demonstrate that VEGF was highly expressed in cultures of human bone marrow-derived mesenchymal stem cells (hMSCs) and the high expression level was maintained during prolonged culture periods (checked up to passage 10). We also confirmed that in vivo hMSCs engrafted into immunodeficient mice could survive and secreted human VEGF. These findings suggest that implantation of hMSCs is a practical means as a source of VEGF production and might be effective in neoangiogenesis.

Osteogenic matrix sheet-cell transplantation using osteoblastic cell sheet resulted in bone formation without scaffold at an ectopic site

We previously reported that in vivo bone formation could be observed in composites of porous hydroxyapatite (HA) scaffolds and cultured mesenchymal stem cells (MSCs). In the present study, we developed a new method for transplantation of cultured MSCs without the necessity of using a scaffold to form bone tissue. MSCs were culture-expanded and lifted as cell sheet structures. These cell sheets, designated osteogenic matrix sheets, showed positive alkaline phosphatase (ALP) staining, high ALP activities and high osteocalcin (OC) contents, indicating their osteogenic potential. We transplanted these sheets into subcutaneous sites in rats to assess whether they possessed in vivo bone-forming capability. The transplanted sheets showed mineralized matrix together with osteocytes and an active osteoblast lining, indicating new bone formation, at 6 weeks after transplantation. HA scaffolds were also wrapped with the sheets to make HA/sheet composites and implanted into subcutaneous sites in rats. Histological sections of the composites revealed bone formation in the HA pores at 4 weeks after implantation. Our present results indicate that MSCs can be cultured as sheet structures, and the resulting sheets themselves or HA-sheet composites represent osteogenic implants that can be used for hard tissue reconstruction.

Growth of a bonelike apatite on chitosan microparticles after a calcium silicate treatment

Bioactive chitosan microparticles can be prepared successfully by treating them with a calcium silicate solution and then subsequently soaking them in simulated body fluid (SBF). Such a combination enables the development of bioactive microparticles that can be used for several applications in the medical field, including injectable biomaterial systems and tissue engineering carrier systems. Chitosan microparticles, 0.6microm in average size, were soaked either for 12h in fresh calcium silicate solution (condition I) or for 1h in calcium silicate solution that had been aged for 24h before use (condition II). Afterwards, they were dried in air at 60 degrees C for 24h. The samples were then soaked in SBF for 1, 3 and 7 days. After the condition I calcium silicate treatment and the subsequent soaking in SBF, the microparticles formed a dense apatite layer after only 7 days of immersion, which is believed to be due to the formation of silanol (Si-OH) groups effective for apatite formation. For condition II, the microparticles successfully formed an apatite layer on their surfaces in SBF within only 1 day of immersion.

Osteogenic potential of cryopreserved human bone marrow-derived mesenchymal stem cells cultured with autologous serum

Secondary bone grafting in the alveolar cleft is one of the most important therapeutic modalities for patients with cleft lip and palate. However, in children, harvesting a sufficient amount of bone is difficult, and repeated operations are often required because deformation of the alveolar cleft may occur because of the grafted bone absorption and bone growth, which imposes a heavy burden on the patients. The burden may be reduced if the banking of human bone marrow-derived mesenchymal stem cells (MSCs) could be made possible, that is, if cryopreserved autologous MSCs, those that have been harvested from the patient's own bone marrow, could be cultured and expanded with the patient's own serum and can be thawed and cultivated for grafting at a later date. In the current study, a hybrid-type bone substitute was prepared by thawing and cultivating MSCs that have been cryopreserved for more than 3 months. The hybrid-type bone substitute was implanted subcutaneously in nude mice. At 6 and 9 weeks after grafting, the bone graft was removed, and the osteogenic potential of the cells cultured with autologous serum, as determined by alkaline phosphatase activity and alizarin red S staining, was compared with those cultured with fetal bovine serum. There was no significant difference in the osteogenic potential between MSCs cultured with autologous serum and those cultured with fetal bovine serum. The results suggest the possibility of artificial bone grafting using MSCs cultured with autologous serum and the banking of the cells.