Repair of cranial bone defects with adipose derived stem cells and coral scaffold in a canine model

Immunoexpression of PPAR-? and Osteocalcin Proteins for Bone Repair of Critical-Size Defects Treated with Fragmented Autogenous Abdominal Adipose Tissue Graft

Immunoexpression of PPAR-γ and osteocalcin proteins was evaluated for bone repair of critical-size defects (CSDs), created in rat calvaria (n=42) and treated with fragmented abdominal autogenous adipose tissue graft. Three groups (n=14) were formed: C (control - blood clot), AB (autogenous bone) and AT (fragmented adipose tissue). The groups were divided into subgroups (n=7) for euthanasia at 30 and 90 days. Histological and immunohistochemical analyses were performed. Data were subjected to descriptive statistics (mode). A complete bone closure was observed in Group AB 90 days after surgery. In Group C, repair was achieved by the formation of collagen fiber bundles oriented parallel to the wound surface at both post-surgery periods. In Group AT the type of healing was characterized by dense connective tissue containing collagen fiber bundles arranged amidst the remaining adipose tissue, with rare heterotopic bone formation associated with fibrosis and different types of tissue necrosis. Immunostaining of PPAR-γ was not observed in any specimen from Groups C and AB. In Group AT, the immunostaining of PPAR-γ was more evident 30 days after surgery. Immunostaining of osteocalcin was present in all groups and at both postoperative periods. The fragmented autogenous abdominal adipose tissue graft did not favor the repair of critical-size bone defects created surgically in rat calvaria as evidenced by the positive immunostaining of PPAR-γ protein and the negative immunostaining of osteocalcin in the osteoblast-like cells and bone matrix.

Basic science and clinical application of stem cells in veterinary medicine

Stem cells play an important role in veterinary medicine in different ways. Currently several stem cell therapies for animal patients are being developed and some, like the treatment of equine tendinopathies with mesenchymal stem cells (MSCs), have already successfully entered the market. Moreover, animal models are widely used to study the properties and potential of stem cells for possible future applications in human medicine. Therefore, in the young and emerging field of stem cell research, human and veterinary medicine are intrinsically tied to one another. Many of the pioneering innovations in the field of stem cell research are achieved by cooperating teams of human and veterinary medical scientists.Embryonic stem (ES) cell research, for instance, is mainly performed in animals. Key feature of ES cells is their potential to contribute to any tissue type of the body (Reed and Johnson, J Cell Physiol 215:329-336, 2008). ES cells are capable of self-renewal and thus have the inherent potential for exceptionally prolonged culture (up to 1-2 years). So far, ES cells have been recovered and maintained from non-human primate, mouse (Fortier, Vet Surg 34:415-423, 2005) and horse blastocysts (Guest and Allen, Stem Cells Dev 16:789-796, 2007). In addition, bovine ES cells have been grown in primary culture and there are several reports of ES cells derived from mink, rat, rabbit, chicken and pigs (Fortier, Vet Surg 34:415-423, 2005). However, clinical applications of ES cells are not possible yet, due to their in vivo teratogenic degeneration. The potential to form a teratoma consisting of tissues from all three germ lines even serves as a definitive in vivo test for ES cells.Stem cells obtained from any postnatal organism are defined as adult stem cells. Adult haematopoietic and MSCs, which can easily be recovered from extra embryonic or adult tissues, possess a more limited plasticity than their embryonic counterparts (Reed and Johnson, J Cell Physiol 215:329-336, 2008). It is believed that these stem cells serve as cell source to maintain tissue and organ mass during normal cell turnover in adult individuals. Therefore, the focus of attention in veterinary science is currently drawn to adult stem cells and their potential in regenerative medicine. Also experience gained from the treatment of animal patients provides valuable information for human medicine and serves as precursor to future stem cell use in human medicine.Compared to human medicine, haematopoietic stem cells only play a minor role in veterinary medicine because medical conditions requiring myeloablative chemotherapy followed by haematopoietic stem cell induced recovery of the immune system are relatively rare and usually not being treated for monetary as well as animal welfare reasons.In contrast, regenerative medicine utilising MSCs for the treatment of acute injuries as well as chronic disorders is gradually turning into clinical routine. Therefore, MSCs from either extra embryonic or adult tissues are in the focus of attention in veterinary medicine and research. Hence the purpose of this chapter is to offer an overview on basic science and clinical application of MSCs in veterinary medicine.

Adipose-derived stromal cells for osteoarticular repair: trophic function versus stem cell activity

The identification of multipotent adipose-derived stromal cells (ASC) has raised hope that tissue regeneration approaches established with bone-marrow-derived stromal cells (BMSC) can be reproduced with a cell-type that is far more accessible in large quantities. Recent detailed comparisons, however, revealed subtle functional differences between ASC and BMSC, stressing the concept of a common mesenchymal progenitor existing in a perivascular niche across all tissues. Focussing on bone and cartilage repair, this review summarises recent in vitro and in vivo studies aiming towards tissue regeneration with ASC. Advantages of good accessibility, high yield and superior growth properties are counterbalanced by an inferiority of ASC to form ectopic bone and stimulate long-bone healing along with their less pronounced osteogenic and angiogenic gene expression signature. Hence, particular emphasis is placed on establishing whether stem cell activity of ASC is so far proven and relevant for successful osteochondral regeneration, or whether trophic activity may largely determine therapeutic outcome.

Choosing the right type of serum for different applications of human adipose tissue-derived stem cells: influence on proliferation and differentiation abilities

BACKGROUND AIMS

Adipose tissue-derived stem cells (ADSCs) are thought to have great potential in regenerative medicine. A xenoprotein-free culture and handling system is desirable. To date, there is only little and contradictory information about the influence of the different types of human serum on ADSC proliferation and differentiation.

METHODS

First, ADSCs were cultured in media containing regular human serum (HS plus) or fetal calf serum (FCS plus) with supplementation of growth factors for three passages. During passage 4, ADSC proliferative activity and adipogenic, osteogenic and chondrogenic differentiation ability was quantified. Second, ADSCs were cultured with three different human sera (regular human serum [HS], human serum from platelet-poor plasma [SPPP] or human serum from platelet-rich plasma [SPRP]) without supplementation of platelet-derived growth factor and assessed accordingly. The growth factor content of the different types of human sera was determined by means of multiplex protein assay and enzyme-linked immunosorbent assay.

RESULTS

The different sera did not affect ADSC doubling time significantly (P < 0.05). Specific glycerol-3-phosphat-dehydrogenase activity was significantly lower in cultures with SPRP (P < 0.01) compared with the other media compositions. Extracellular calcium deposition was significantly higher in cells differentiated in cultures with HS or SPPP compared with those with SPRP, HS plus or FCS (P < 0.01). Glycosaminoglycan content and collagen 2 were highest in cells cultured with SPRP (P < 0.001).

CONCLUSIONS

Culturing ADSCs in human serum appears to be a reasonable and efficient alternative compared with FCS. With respect to the outcome of a sighted clinical application, it appears to be feasible to handle the cells in a serum suitable for the intended later use.

Bioceramic-collagen scaffolds loaded with human adipose-tissue derived stem cells for bone tissue engineering

The combination of bioceramics and stem cells has attracted the interest of research community for bone tissue engineering applications. In the present study, a combination of Bio-Oss(®) and type 1 collagen gel as scaffold were loaded with human adipose-tissue derived mesenchymal stem cells (AT-MSCs) after isolation and characterization, and the capacity of them for bone regeneration was investigated in rat critical size defects using digital mammography, multi-slice spiral computed tomography imaging and histological analysis. 8 weeks after implantation, no mortality or sign of inflammation was observed in the site of defect. According to the results of imaging analysis, a higher level of bone regeneration was observed in the rats receiving Bio-Oss(®)-Gel compared to untreated group. In addition, MSC-seeded Bio-Oss-Gel induced the highest bone reconstruction among all groups. Histological staining confirmed these findings and impressive osseointegration was observed in MSC-seeded Bio-Oss-Gel compared with Bio-Oss-Gel. On the whole, it was demonstrated that combination of AT-MSCs, Bio-Oss and Gel synergistically enhanced bone regeneration and reconstruction and also could serve as an appropriate structure to bone regenerative medicine and tissue engineering application.

Biocomposite cryogels as tissue-engineered biomaterials for regeneration of critical-sized cranial bone defects

Analysis of the in vivo regeneration capability of any tissue-engineered biomaterial is necessary once it shows potential characteristics during in vitro studies. Thus, we applied polyvinyl alcohol-tetraethylorthosilicate-alginate-calcium oxide (PTAC) biocomposite cryogel on critical-sized cranial bone defects in wistar rats for examining the comparative bone regeneration of cryogel-treated and nontreated defects over a period of 4 weeks. An in-depth analysis was performed from macroscopic level till the gene level. Bone regeneration in cryogel-treated defects was clearly evident from the results, whereas the nontreated group did not show any defect healing except at few peripheral areas. At the macroscopic level, micro-computed tomography analysis revealed new bone formation. This was further confirmed at the cellular level, wherein, new bone formation was demonstrated by hematoxylin and eosin staining. Osteoblastic differentiation was further validated by immunohistological staining of runt-related transcription factor-2 (Runx-2) protein and via calcium-phosphate crystal formation after 2 weeks through scanning electron microscopy and energy dispersive X-ray spectroscopy. Finally, at the gene level, real-time PCR analysis confirmed the mRNA expression of osteoblastic markers, that is, runx-2, collagen type I (Col I), alkaline phosphatase (ALP), and osteocalcin (OCN). Therefore, the results of in vivo cranial defect model studies suggest that PTAC biocomposite cryogels can show suitable potential for human bone regeneration.

Adipose-derived mesenchymal cells for bone regereneration: state of the art

Adipose tissue represents a hot topic in regenerative medicine because of the tissue source abundance, the relatively easy retrieval, and the inherent biological properties of mesenchymal stem cells residing in its stroma. Adipose-derived mesenchymal stem cells (ASCs) are indeed multipotent somatic stem cells exhibiting growth kinetics and plasticity, proved to induce efficient tissue regeneration in several biomedical applications. A defined consensus for their isolation, classification, and characterization has been very recently achieved. In particular, bone tissue reconstruction and regeneration based on ASCs has emerged as a promising approach to restore structure and function of bone compromised by injury or disease. ASCs have been used in combination with osteoinductive biomaterial and/or osteogenic molecules, in either static or dynamic culture systems, to improve bone regeneration in several animal models. To date, few clinical trials on ASC-based bone reconstruction have been concluded and proved effective. The aim of this review is to dissect the state of the art on ASC use in bone regenerative applications in the attempt to provide a comprehensive coverage of the topics, from the basic laboratory to recent clinical applications.

Micro-CT and PET analysis of bone regeneration induced by biodegradable scaffolds as carriers for dental pulp stem cells in a rat model of calvarial "critical size" defect: Preliminary data

Bone regeneration strategies in dentistry utilize biodegradable scaffolds seeded with stem cells able to induce bone formation. However, data on regeneration capacity of these tissue engineering constructs are still deficient. In this study micro-Computed tomography (micro-CT) and positron emission tomography (PET) analyses were used to investigate bone regeneration induced by two scaffolds [Granular deproteinized bovine bone (GDPB) and Beta-tricalcium phosphate (β-TCP)] used alone or in combination with dental pulp stem cells (DPSC) in a tissue engineered construct implanted in a rat critical calvarial defect. Bone mineral density (BMD) and standard uptake value (SUV) of tracer incorporation were measured after 2, 4, 8, and 12 weeks post-implant. The results showed that: (1) GDPB implants were mostly well positioned, as compared to ß-TCP; (2) GDPB induced higher BMD and SUV values within the cranial defect as compared to ß-TCP, either alone or in combination with stem cells; (3) addition of DPSC to the grafts did not significantly induce an increase in BMD and SUV values as compared to the scaffolds grafted alone, although a small tendency to increase was observed. Thus our study demonstrates that GDPB, when used to fill critical calvarial defects, induces a greater percentage of bone formation as compared to ß-TCP. Moreover, this study shows that addition of DPSC to pre-wetted scaffolds has the potential to ameliorate bone regeneration process, although the set of optimal conditions requires further investigation.

The graft of autologous adipose-derived stem cells in the corneal stromal after mechanic damage

This study was designed to explore the feasibility of using autologous rabbit adipose derived stem cells (rASCs) as seed cells and polylactic-co-glycolic acid (PLGA) as a scaffold for repairing corneal stromal defects. rASCs isolated from rabbit nape adipose tissue were expanded and seeded on a PLGA scaffold to fabricate cell-scaffold constructs. After 1 week of cultivation in vitro, the cell-scaffold complexes were transplanted into corneal stromal defects in rabbits. In vivo, the autologous rASCs-PLGA constructed corneal stroma gradually became transparent without corneal neovascularization after 12 weeks. Hematoxylin and eosin staining and transmission electron microscopy examination revealed that their histological structure and collagen fibril distribution at 24 weeks after implantation were similar to native counterparts. As to the defect treated with PLGA alone, the stromal defects remained. And scar tissue was observed in the untreated-group. The implanted autologous ASCs survived up to 24 weeks post-transplantation and differentiated into functional keratocytes, as assessed by the expression of aldehyde-3-dehydrogenase1A1 (ALDH1A1) and cornea-specific proteoglycan keratocan. Our results revealed that autologous rASCs could be one of the cell sources for corneal stromal restoration in diseased corneas or for tissue engineering of a corneal equivalent.

Midterm clinical and tomodensitometric evaluation of cortical bone repair using bone substitute and allogenic membrane protection in the areas of cortical bone harvesting in the parietal cranium in preimplant reconstructive surgery

The authors present their clinical and computed tomographic findings in a series of 13 cases of monocortical bone harvesting, in the setting of preimplant reconstructive surgery, with the harvest sites filled with granular bovine bone substitute, which had an additional coverage using a collagen membrane. These patients were compared with a control group of 6 patients who had not received any cranial bone reconstruction during the initial harvesting. Clinical and computed tomographic evaluations of the repaired parietal cortical bone harvest sites were performed to study the contour of the cortical bone harvest sites in relation to the surrounding soft tissue. Among the 13, there were no clinical cases of infection or allergic reaction. Midterm results of the parietal cortical bone reconstruction using granular bone substitute with overlying protective biodegradable membrane show that this method of reconstruction of the cranium after cranial bone harvesting resulted in significantly improved clinical outcomes.

Repair of an articular cartilage defect using adipose-derived stem cells loaded on a polyelectrolyte complex scaffold based on poly(l-glutamic acid) and chitosan

As a synthetic polypeptide water-soluble poly(l-glutamic acid) (PLGA) was designed to fabricate scaffolds for cartilage tissue engineering. Chitosan (CHI) has been employed as a physical cross-linking component in the construction of scaffolds. PLGA/CHI scaffolds act as sponges with a swelling ratio of 760±45% (mass%), showing promising biocompatibility and biodegradation. Autologous adipose-derived stem cells (ASCs) were expanded and seeded on PLGA/CHI scaffolds, ASC/scaffold constructs were then subjected to chondrogenic induction in vitro for 2weeks. The results showed that PLGA/CHI scaffolds could effectively support ASC adherence, proliferation and chondrogenic differentiation. The ASCs/scaffold constructs were then transplanted to repair full thickness articular cartilage defects (4mm in diameter, to the depth of subchondral bone) created in rabbit femur trochlea. Histological observations found that articular defects were covered with newly formed cartilage 6weeks post-implantation. After 12weeks the regenerated cartilage had integrated well with the surrounding native cartilage and subchondral bone. Toluidine blue and immunohistochemical staining confirmed similar accumulation of glycosaminoglycans and type II collagen in engineered cartilage as in native cartilage 12weeks post-implantation. The result was further supported by quantitative analysis of extracellular matrix deposition. The compressive modulus of the engineered cartilage increased significantly from 30% of that of normal cartilage at 6weeks to 83% at 12weeks. Cyto-nanoindentation also showed analogous biomechanical behavior of the engineered cartilage to that of native cartilage. The results of the present study thus demonstrate the potentiality of PLGA/CHI scaffolds in cartilage tissue engineering.

Osteogenesis of Adipose-Derived Stem Cells

Current treatment options for skeletal repair, including immobilization, rigid fixation, alloplastic materials and bone grafts, have significant limitations. Bone tissue engineering offers a promising method for the repair of bone deficieny caused by fractures, bone loss and tumors. The use of adipose derived stem cells (ASCs) has received attention because of the self-renewal ability, high proliferative capacity and potential of osteogenic differentiation in vitro and in vivo studies of bone regeneration. Although cell therapies using ASCs are widely promising in various clinical fields, no large human clinical trials exist for bone tissue engineering. The aim of this review is to introduce how they are harvested, examine the characterization of ASCs, to review the mechanisms of osteogenic differentiation, to analyze the effect of mechanical and chemical stimuli on ASC osteodifferentiation, to summarize the current knowledge about usage of ASC in vivo studies and clinical trials, and finally to conclude with a general summary of the field and comments on its future direction.

The role of miR-31-modified adipose tissue-derived stem cells in repairing rat critical-sized calvarial defects

With the increasing application of microRNAs (miRNAs) in the treatment and monitoring of different diseases, miRNAs have become an important tool in biological and medical research. Recent studies have proven that miRNAs are involved in the osteogenic differentiation of stem cells. However, few studies have reported the use of miRNA-modified adult stem cells to repair critical-sized defects (CSDs) using tissue engineering technology. It is known that miR-31 is a pleiotropically acting miRNA that inhibits cancer metastasis and targets special AT-rich sequence-binding protein 2 (Satb2) in fibroblasts. However, it is not clear whether the function of miR-31 is to enhance adipose tissue-derived stem cell (ASC) osteogenesis, along with its association with Satb2, during osteogenic differentiation and bone regeneration. In this study, we systematically evaluated the function of miR-31 in enhancing ASC osteogenesis and the therapeutic potential of miR-31-modified ASCs in a rat CSD model with β-tricalcium phosphate (β-TCP) scaffolds. ASCs were treated with lentivirus (Lenti)-miR-31, Lenti-as-miR-31 (antisense) or Lenti-NC (negative control). These genetically modified ASCs were then combined with β-TCP scaffolds to repair CSDs in rats. The results showed that in cultured ASCs in vitro, Lenti-as-miR-31 significantly enhanced osteogenic mRNA and protein expression when compared with the Lenti-NC group. Moreover, we firstly found that a Runt-related transcription factor 2 (Runx2), Satb2 and miR-31 regulatory loop triggered by bone morphogenetic protein-2 (BMP-2) plays an important role in ASCs' osteogenic differentiation and bone regeneration. More importantly, we found that miR-31-knockdown ASCs dramatically improved the repair of CSDs, including increased bone volume, increased bone mineral density (BMD) and decreased scaffold residue in vivo. These data confirm the essential role of miR-31-modified ASCs in osteogenesis in vitro and in vivo.

Synergistic effect between bioactive glass foam and a perfusion bioreactor on osteogenic differentiation of human adipose stem cells

Tissue engineering is a multidisciplinary science that combines a structural scaffold and cells to form a construct able to promote regeneration of injured tissue. Bioactive glass foam produced by sol-gel is an osteoinductive material with a network of interconnected macropores necessary for cell colonization. The use of human adipose-derived stem cell (hASC) presents advantages as the potential for a large number of cells, rapid expansion in vitro and the capability of differentiating into osteoblasts. The use of a bioreactor in three-dimensional cell culture enables greater efficiency for cell nutrition and application of mechanical forces, important modulators of bone physiology. The hASC seeded in a bioactive glass scaffold and cultured in osteogenic Leibovitz L-15 medium in a bioreactor with a flow rate of 0.1 mL min(-1) demonstrated a significant increase in cell proliferation and viability and alkaline phosphatase (ALP) activity peak after 14 days. The immunofluorescence assay revealed an expression of osteopontin, osteocalcin and type I collagen from 7 to 21 days after culture. The cells changed from a spindle shape to a cuboidal morphology characteristic of osteoblasts. The polymerase chain reaction assay confirmed that osteopontin, osteocalcin, and ALP genes were expressed. These results indicate that hASCs differentiated into an osteogenic phenotype when cultured in bioactive glass scaffold, osteogenic Leibovitz L-15 medium and a perfusion bioreactor. Therefore, these results highlight the synergism between a bioactive glass scaffold and the effect of perfusion on cells and indicate the differentiation into an osteogenic phenotype.

Fragmented adipose tissue graft for bone healing: histological and histometric study in rabbits' calvaria

Objective The adipose tissue represents an important reservoir of stem cells. There are few studies in the literature with which to histologically evaluate whether or not the adipose tissue graft is really a safe option to achieve bone repair. This study histologically analyzed the effect of fragmented autogenous adipose tissue grafts on bone healing in surgically created, critical-size defects (CSD) in a rabbit’s calvaria. Study design Forty-two New Zealand rabbits were used in this study. CSD that were 15 mm in diameter were created in the calvarium of each animal. The defects were randomly divided into two groups: in Group C (control), the defect was filled only by a blood clot and, in Group FAT (i.e., fragmented adipose tissue), the defect was filled with fragmented autogenous adipose tissue grafts. The groups were divided into subgroups (n = 7) for euthanasia at 7, 15, and 40 days after the procedure had been conducted. Histologic and histometric analyses were performed. Data were statistically analysed with ANOVA and Tukey’s tests (p < 0.05). Results The amount of bone formation did not show statistically significant differences seven days after the operation, which indicates that the groups had similar amounts of mineral deposition in the earlier period of the repair. Conversely, a significant of amount of bone matrix deposition was identified in the FAT group at 15 and 40 days following the operation, both on the border and in the body of the defect. Such an outcome was not found in the control group. Conclusion In this study, an autologous adipose tissue graft may be considered as likely biomaterial for bone regeneration, since it positively affected the amount of bone formation in surgically created CSD in the rabbits’ calvaria 40 days after the procedure had been performed. Further investigations with a longer time evaluation are warranted to determine the effectiveness of autologous adipose tissue graft in the bone healing.

Key words:Adipose tissue, bone regeneration, rabbits, critical defects.

Translating stem cell therapies: the role of companion animals in regenerative medicine

Veterinarians and veterinary medicine have been integral to the development of stem cell therapies. The contributions of large animal experimental models to the development and refinement of modern hematopoietic stem cell transplantation were noted nearly five decades ago. More recent advances in adult stem cell/regenerative cell therapies continue to expand knowledge of the basic biology and clinical applications of stem cells. A relatively liberal legal and ethical regulation of stem cell research in veterinary medicine has facilitated the development and in some instances clinical translation of a variety of cell-based therapies involving hematopoietic stem cells and mesenchymal stem cells, as well as other adult regenerative cells and recently embryonic stem cells and induced pluripotent stem cells. In fact, many of the pioneering developments in these fields of stem cell research have been achieved through collaborations of veterinary and human scientists. This review aims to provide an overview of the contribution of large animal veterinary models in advancing stem cell therapies for both human and clinical veterinary applications. Moreover, in the context of the "One Health Initiative," the role veterinary patients may play in the future evolution of stem cell therapies for both human and animal patients will be explored.

Low-level laser therapy promotes the osteogenic potential of adipose-derived mesenchymal stem cells seeded on an acellular dermal matrix

This study investigates the feasibility of using an adipose-derived mesenchymal stem cell (ASC)-seeded acellular dermal matrix (ADM) along with low-level laser therapy (LLLT) to repair bone defect in athymic nude mice. Critical-sized calvarial defects were treated either with ADM, ADM/LLLT, ADM/ASCs, or ADM/ASCs/LLLT. In micro-computed tomography scans, the ADM/ASCs and the ADM/ASCs/LLLT groups showed remarkable bone formation after 14 days. Additionally, bone regeneration in the ADM/ASCs/LLLT group was obvious at 28 days, but in the ADM/ASCs group at 56 days. Bone mineral density and bone tissue volume in the ADM/ASCs/LLLT group significantly increased after 7 days, but in the ADM/ASCs group after 14 days. Histological analysis revealed that the defects were repaired in the ADM/ASCs and the ADM/ASCs/LLLT group, while the defects in the ADM and the ADM/LLLT groups exhibited few bone islands at 28 and 56 days. The successful seeding of ASCs onto ADM was confirmed, and LLLT enhanced the proliferation and the survival of ASCs at 14 days. Our results indicate that ASC-seeded grafts promote bone regeneration, and the application of LLLT on ASC-seeded ADM results in rapid bone formation. The implantation of an ASC-seeded ADM combined with LLLT may be used effectively for bone regeneration.

Critical size bone defect reconstruction by an autologous 3D osteogenic-like tissue derived from differentiated adipose MSCs

For critical size bone defects and bone non-unions, bone tissue engineering using osteoblastic differentiated adipose mesenchymal stem cells (AMSCs) is limited by the need for a biomaterial to support cell transplantation. An osteoblastic three-dimensional autologous graft made of AMSCs (3D AMSC) was developed to solve this issue. This autograft was obtained by supplementing the osteoblastic differentiation medium with demineralized bone matrix. Two surgical models were developed to assess the potential of this 3D osteogenic AMSC autograft. A four-level spinal fusion using polyetheretherketone cages was designed in six pigs to assess the early phase of ossification (8-12 weeks postimplantation). In each pig, four groups were compared: cancellous bone autograft, freeze-dried irradiated cancellous pig bone, 3D AMSC, and an empty cage. A critical size femoral defect (n = 4, bone non-union confirmed 6 months postoperatively) was used to assess the 3D AMSCs' ability to achieve bone fusion. Pigs were followed by CT scan and explanted specimens were analyzed for bone tissue remodeling by micro-CT scan, micro-radiography, and histology/histomorphometry. In the spine fusion model, bone formation with the 3D AMSC was demonstrated by a significant increase in bone content. In the critical-size femoral defect model, the 3D AMSC achieved new bone formation and fusion in a poorly vascularized fibrotic environment. This custom-made 3D osteogenic AMSC autograft is a therapeutic solution for bone non-unions and for critical-size defects.

Adipogenic and osteogenic differentiation of Lin(-)CD271(+)Sca-1(+) adipose-derived stem cells

Adipose-derived stem cells (ASCs) have been defined as cells that undergo sustained in vitro growth and have multilineage differentiation potential. However, the identity and purification of ASCs has proved elusive due to the lack of specific markers and poor understanding of their physiological roles. Here, we prospectively isolated and identified a restricted homogeneous subpopulation of ASCs (Lin(-)CD271(+)Sca-1(+)) from mouse adipose tissues on the basis of cell-surface markers. Individual ASCs generated colony-forming unit-fibroblast at a high frequency and could differentiate into adipocytes, osteoblasts, and chondrocytes in vitro. Expansion of ASCs in a large quantity was feasible in medium supplemented with fibroblast growth factor-2 and leukemia inhibitory factor, without loss of adipogenic and osteogenic differentiation capacity. Moreover, we found that the transplanted ASCs can differentiate into adipocytes in adipogenic microenvironment in vivo and osteoblasts in osteogenic microenvironment in vivo. Thus we proved that Lin, CD271, and Sca-1 could be used as the specific markers to purify ASCs from adipose tissue. The method we established to identify ASCs as defined in vivo entities will help develop ASCs transplantation as a new therapeutic strategy for bone regeneration and adipose tissue regeneration in clinic.

Adipose-Derived Stem Cells in Tissue Regeneration: A Review

In 2001, researchers at the University of California, Los Angeles, described the isolation of a new population of adult stem cells from liposuctioned adipose tissue. These stem cells, now known as adipose-derived stem cells or ADSCs, have gone on to become one of the most popular adult stem cells populations in the fields of stem cell research and regenerative medicine. As of today, thousands of research and clinical articles have been published using ASCs, describing their possible pluripotency in vitro, their uses in regenerative animal models, and their application to the clinic. This paper outlines the progress made in the ASC field since their initial description in 2001, describing their mesodermal, ectodermal, and endodermal potentials both in vitro and in vivo, their use in mediating inflammation and vascularization during tissue regeneration, and their potential for reprogramming into induced pluripotent cells.

Enhanced mechanical strength and biocompatibility of electrospun polycaprolactone-gelatin scaffold with surface deposited nano-hydroxyapatite

In this study for the first time, we compared physico-chemical and biological properties of polycaprolactone-gelatin-hydroxyapatite scaffolds of two types: one in which the nano-hydroxyapatite (n-HA) was deposited on the surface of electrospun polycaprolactone-gelatin (PCG) fibers via alternate soaking process (PCG-HAAS) and other in which hydroxyapatite (HA) powders were blended in electrospinning solution of PCG (PCG-HAB). The microstructure of fibers was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which showed n-HA particles on the surface of the PCG-HAAS scaffold and embedded HA particles in the interior of the PCG-HAB fibers. PCG-HAAS fibers exhibited the better Young's moduli and tensile strength as compared to PCG-HAB fibers. Biological properties such as cell proliferation, cell attachment and alkaline phosphatase activity (ALP) were determined by growing human osteosarcoma cells (MG-63) over the scaffolds. Cell proliferation and confocal results clearly indicated that the presence of hydroxyapatite on the surface of the PCG-HAAS scaffold promoted better cellular adhesion and proliferation as compared to PCG-HAB scaffold. ALP activity was also observed better in alternate soaked PCG scaffold as compared to PCG-HAB scaffold. Mechanical strength and biological properties clearly demonstrate that surface deposited HA scaffold prepared by alternate soaking method may find application in bone tissue engineering.

Bone regeneration in a canine cranial model using allogeneic adipose derived stem cells and coral scaffold

Adipose tissue derived stem cells (ASCs) based therapies for the repair and regeneration of various tissues have been widely investigated recently because of their multilineage potential and self-renewal capability. Our previous study demonstrated that autologous ASCs loaded onto natural coral scaffolds could repair cranial critical-sized defects (CSDs) in a canine model. The objective of this study was to determine whether the use of allogeneic ASCs could heal the same defect without the use of immunosuppressive therapy. The pedigree mismatch, mixed lymphocyte reaction assays (MLRs) and allogeneic skin graft experiments were performed to confirm unrelated ASC donors and recipients. A total of 12 adult Beagle dogs were enrolled in this study and divided into two groups. Bilateral cranial CSDs were created in each animal. The right-side defect was treated with allogeneic ASCs delivered onto a coral scaffold, and the left defect was either filled with an autologous ASC/coral composite (Group 1, n = 5) or with one coral scaffold alone (Group 2, n = 5). The systematic immune response and bone healing were evaluated postoperatively. The results showed that allogeneic ASC transplantation did not induce a systemic immune response by the hosts, and allogeneic ASCs could repair the cranial CSDs in an analogous way to that of the autologous cells. Moreover, both the green fluorescently labeled allogeneic and autologous ASCs were detected within the lacunae of newly formed bone in the defect site at 24 weeks, illustrating that the grafted ASCs contributed directly to bone regeneration in vivo. Thus, we concluded that allogeneic ASCs have the capacity to regenerate bone within craniofacial defects, providing an alternative source of seed cells for bone tissue engineering.

Osteogenic differentiation and osteochondral tissue engineering using human adipose-derived stem cells

Osteogenesis and the production of composite osteochondral tissues were investigated using human adult adipose-derived stem cells and polyglycolic acid (PGA) mesh scaffolds under dynamic culture conditions. For osteogenesis, cells were expanded with or without osteoinduction factors and cultured in control or osteogenic medium for 2 weeks. Osteogenic medium enhanced osteopontin and osteocalcin gene expression when applied after but not during cell expansion. Osteogenesis was induced and mineralized deposits were present in tissues produced using PGA culture in osteogenic medium. For development of osteochondral constructs, scaffolds seeded with stem cells were precultured in either chondrogenic or osteogenic medium, sutured together, and cultured in dual-chamber stirred bioreactors containing chondrogenic and osteogenic media in separate compartments. After 2 weeks, total collagen synthesis was 2.1-fold greater in the chondroinduced sections of the composite tissues compared with the osteoinduced sections; differentiation markers for cartilage and bone were produced in both sections of the constructs. The results from the dual-chamber bioreactor highlight the challenges associated with achieving simultaneous chondrogenic and osteogenic differentiation in tissue engineering applications using a single stem-cell source.

Isolation of canine mesenchymal stem cells from amniotic fluid and differentiation into hepatocyte-like cells

Recent findings have demonstrated that amniotic fluid cells are an interesting and potential source of mesenchymal stem cells (MSCs). In this study, we isolated MSCs from canine amniotic fluid and then characterized their multilineage differentiation ability. Canine amniotic fluid stem (cAFS) cells at passage 5 had a fibroblast-like morphology instead of forming colonies and were positive for pluripotent stem cell markers such as OCT4, NANOG, and SOX2. Flow cytometry analysis showed the expression of MSC surface markers CD44, CD29, and CD90 on the cAFS cells. In addition, these cells were cultured under conditions favorable for adipogenic, chondrogenic, and osteogenic induction. The results of this experiment confirmed the mesenchymal nature of cAFS cells and their multipotent potential. Interestingly, although the cells exhibited a fibroblast-like morphology after hepatogenic induction, reverse transcription-polymerase chain reaction revealed that the expression of several hepatic genes, such as albumin, tyrosine aminotransferase, and alpha-1 antiproteinase, increased following maturation and differentiation. These findings indicated that cAFS cells have functional properties similar to those of hepatocytes. Taken together, the results of our study demonstrated that cAFS cells with mesenchymal characteristics can be successfully isolated from canine amniotic fluid and possess functional properties characteristic of hepatocytes. The findings of our work suggest that cAFS cells have the potential to be a resource for cell-based therapies in a canine model of hepatic disease.

Development of a bone reconstruction technique using a solid free-form fabrication (SFF)-based drug releasing scaffold and adipose-derived stem cells

For tissue regeneration, three essential components of scaffolds, signals (biomolecules), and cells are required. Moreover, because bony defects are three-dimensional in many clinical circumstances, an exact 3D scaffold is important. Therefore, we proposed an effective reconstruction tool for cranial defects using human adipose-derived stem cells (hADSCs) and a 3D functional scaffold fabricated by solid free-form fabrication (SFF) technology that secretes biomolecules. We fabricated poly(propylene fumarate)-based 3D scaffolds with embedded microsphere-deliverable bone morphogenetic protein-2 (BMP-2) by microstereolithography. BMP-2-loaded SFF scaffolds with/without hADSCs (SFF/BMP/hADSCs scaffolds and SFF/BMP scaffolds, respectively) and BMP-2-unloaded SFF scaffolds (SFF scaffolds) were then implanted in rat crania, and in vivo bone formation was observed. Analyses of bone formation areas using micro-computed tomography (micro-CT) showed the superiority of SFF/BMP/hADSCs scaffolds. Hematoxylin and eosin stain, Masson's trichrome stain, and collagen type-I stain supported the results of the micro-CT scan. And human leukocyte antigen-ABC showed that seeded, differentiated hADSCs were well grown and changed to the bone tissue at the inside of the scaffold. Results showed that our combination of a functional 3D scaffold and hADSCs may be a useful tool for improving the reconstruction quality of severe bony defects in which thick bone is required.

Short (15 minutes) bone morphogenetic protein-2 treatment stimulates osteogenic differentiation of human adipose stem cells seeded on calcium phosphate scaffolds in vitro

A one-step concept for bone regeneration has been postulated in which human adipose stem cells (hASCs) are harvested, triggered to differentiate, seeded on carriers, and implanted in the same operative procedure. Toward this goal it was investigated whether short (minutes) incubation with bone morphogenetic protein-2 (BMP-2) suffices to trigger osteogenic differentiation of hASCs seeded on calcium phosphate carriers. hASCs were treated with or without BMP-2 (10 ng/mL) for 15 min, and seeded on β-tricalcium phosphate granules (β-TCP; sized <0.7 mm or >0.7 mm) or biphasic calcium phosphate (BCP; 60%/40% or 20%/80% hydroxyapatite/β-TCP). Attachment was determined after 10-30 min. Proliferation (DNA content) and osteogenic differentiation (alkaline phosphatase activity, gene expression) were analyzed up to 3 weeks of culture. hASC attachment to the different scaffolds was similar, and unaffected by BMP-2. It stimulated gene expression of the osteogenic markers core binding factor alpha 1, collagen-1, osteonectin, and osteocalcin in hASCs seeded on BCP and β-TCP. Downregulation of osteopontin expression by BMP-2 was seen in BCP-seeded cells only. BMP-2 treatment inhibited expression of the adipogenic marker peroxisome proliferator-activated receptor gamma. In conclusion, 15 min BMP-2 preincubation of hASCs seeded on BCP/β-TCP scaffolds had a long-lasting stimulating effect on osteogenic differentiation in vitro. These results strongly support a one-step clinical concept for bone regeneration.

Adipose tissue engineering with human adipose tissue-derived adult stem cells and a novel porous scaffold

We investigated the effect of a novel porous scaffold composed with water-soluble poly(L-glutamic acid) (PLGA) and chitosan (CS) on the attachment, proliferation, and adipogenic differentiation of human adipose tissue-derived adult stem cells (ADSCs) in vitro and in vivo. Scanning electron microscope and fluorescent Dil labeling were used to reveal the attachment and growth of ADSCs on scaffolds; cell proliferation was detected by DNA assay. The adipogenic differentiation potential of ADSCs on the scaffolds was assayed by Oil-red O staining and further confirmed by reverse transcriptase polymerase chain reaction (RT-PCR) for adipogenic gene markers (peroxisome proliferator-activated receptor γ2, lipoprotein lipase, fatty acid-binding protein, adiponectin). Cell-seeded constructs exposed to adipogenic medium for 2 weeks in vitro were implanted in severe combined immunodeficient (SCID) mice for 6 weeks. It was shown that ADSCs attached and spread well on scaffolds with good proliferation behaviors and abundance of extracellular matrix deposition. Oil-red O staining and RT-PCR showed adipogenic differentiation potential of ADSCs on scaffolds. Newly formed adipose-like tissue was confirmed in vivo in SCID mice by Oil-red O staining. PLGA/CS porous scaffolds exhibit good compatibility to ADSCs and can be promising biomaterials for adipose tissue engineering.

An abundant perivascular source of stem cells for bone tissue engineering

Adipose tissue is an ideal mesenchymal stem cell (MSC) source, as it is dispensable and accessible with minimal morbidity. However, the stromal vascular fraction (SVF) of adipose tissue is a heterogeneous cell population, which has disadvantages for tissue regeneration. In the present study, we prospectively purified human perivascular stem cells (PSCs) from n = 60 samples of human lipoaspirate and documented their frequency, viability, and variation with patient demographics. PSCs are a fluorescence-activated cell sorting-sorted population composed of pericytes (CD45-, CD146+, CD34-) and adventitial cells (CD45-, CD146-, CD34+), each of which we have previously reported to have properties of MSCs. Here, we found that PSCs make up, on average, 43.2% of SVF from human lipoaspirate (19.5% pericytes and 23.8% adventitial cells). These numbers were minimally changed by age, gender, or body mass index of the patient or by length of refrigerated storage time between liposuction and processing. In a previous publication, we observed that human PSCs (hPSCs) formed significantly more bone in vivo in comparison with unsorted human SVF (hSVF) in an intramuscular implantation model. We now extend this finding to a bone injury model, observing that purified hPSCs led to significantly greater healing of mouse critical-size calvarial defects than hSVF (60.9% healing as opposed to 15.4% healing at 2 weeks postoperative by microcomputed tomography analysis). These studies suggest that adipose-derived hPSCs are a new cell source for future efforts in skeletal regenerative medicine. Moreover, hPSCs are a stem cell-based therapeutic that is readily approvable by the U.S. Food and Drug Administration, with potentially increased safety, purity, identity, potency, and efficacy.

Platelet-rich plasma favors proliferation of canine adipose-derived mesenchymal stem cells in methacrylate-endcapped caprolactone porous scaffold niches

Osteoarticular pathologies very often require an implementation therapy to favor regeneration processes of bone, cartilage and/or tendons. Clinical approaches performed on osteoarticular complications in dogs constitute an ideal model for human clinical translational applications. The adipose-derived mesenchymal stem cells (ASCs) have already been used to accelerate and facilitate the regenerative process. ASCs can be maintained in vitro and they can be differentiated to osteocytes or chondrocytes offering a good tool for cell replacement therapies in human and veterinary medicine. Although ACSs can be easily obtained from adipose tissue, the amplification process is usually performed by a time consuming process of successive passages. In this work, we use canine ASCs obtained by using a Bioreactor device under GMP cell culture conditions that produces a minimum of 30 million cells within 2 weeks. This method provides a rapid and aseptic method for production of sufficient stem cells with potential further use in clinical applications. We show that plasma rich in growth factors (PRGF) treatment positively contributes to viability and proliferation of canine ASCs into caprolactone 2-(methacryloyloxy) ethyl ester (CLMA) scaffolds. This biomaterial does not need additional modifications for cASCs attachment and proliferation. Here we propose a framework based on a combination of approaches that may contribute to increase the therapeutical capability of stem cells by the use of PRGF and compatible biomaterials for bone and connective tissue regeneration.

The potential of adipose-derived stem cells in craniofacial repair and regeneration

The recent identification of a mesenchymal stem cell population in adipose tissue has led to an abundance of research focused on the regenerative properties of these cells. As such, adipose-derived stem cells (ASCs) and potential therapies in craniofacial regeneration have been widely studied. This review will discuss the identification and potential of ASCs, and specifically, preclinical and clinical studies using ASCs in craniofacial repair. Studies involving ASCs in the repair of defects caused by craniosynostosis and Treacher Collins syndrome will be discussed. A comprehensive review of the literature will be presented, focusing on fat grafting and biomaterials-based approaches that include ASCs for craniofacial regeneration.

Effect of acellular dermal matrix as a delivery carrier of adipose-derived mesenchymal stem cells on bone regeneration

The purpose of this study is to evaluate the effect of acellular dermal matrix (ADM) as a delivery carrier of adipose-derived mesenchymal stem cells (ASCs) on bone regeneration in athymic murine calvarial bone defect. Paired-critical size defects in nude rat skull were made. The right-side defects received ASCs/ADM or only ADM, whereas the left-side defect was not treated. In 3D images, new bone formation in the ASCs/ADM group was apparent at 4 wk, but in the ADM group at 8 wk. At 4 and 8 wk, bone mineral density and tissue volume in rats that received ASCs/ADM were significantly greater than rats that received ADM and control groups. Histological examination revealed that the defect was repaired by bone in the ASCs/ADM group, whereas only minimal bone island with fibrous connection was observed in the control group. In histomorphometric analysis, the total healing score in the ASCs/ADM group at 4 wk was significantly higher than the ADM and negative control group, whereas the score of 8 wk was similar between the ASCs/ADM and ADM group. ASCs/ADM implants promote new bone formation more rapidly than ADM only or no treatment. ADM seeded with ASCs may be potentially useful as a future biomaterial option in bone implants.

Adipose-derived stem cells combined with a demineralized cancellous bone substrate for bone regeneration

Mesenchymal stem cells (MSCs) isolated from cadaveric adipose tissue can be obtained in large quantities, and have been reported in the literature to be capable of inducing bone formation in vivo and ex vivo.( 1-6 ) The hypothesis tested whether a demineralized cancellous bone matrix (DCBM) can provide an effective substrate for selection and retention of stem cells derived from the stromal vascular fraction (SVF) of adipose. Human cadaveric adipose tissue was recovered from a donor and digested. The resulting SVF-containing MSCs were seeded onto the demineralized bone allografts, after which the nonadherent cells were washed off. The MSCs were characterized using a flow cytometer and tri-lineage differentiation (osteogenesis, chondrogenesis, and adipogenesis) in vitro. The stem cell-seeded allografts were also characterized for cell number, adherence to the DCBM, osteogenic activity (alkaline phosphatase and Alizarin Red staining), and bone morphorgenic protein (BMP) quantity. Flow cytometry identified a mean total of 7.2% MSCs in SVF and 87.2% MSCs after culture. The stem cells showed the capability of differentiating into bone, cartilage, and fat. On the 21 stem cell-seeded bone allografts, there were consistent, attached, viable cells (100,744±22,762 cells/cube). An assessment of donor age, gender, and body mass index revealed no significant differences in cell numbers. Enzyme-linked immunosorbent assay revealed the presence of BMP-2 and BMP-7. In conclusion, this bone graft contains three key elements for bone regeneration: adhered osteogenic stem cells, 3D osteoconductive bone scaffold, and osteoinductive BMP signal. It therefore has the potential to be effective for bone regeneration.

Perivascular stem cells: a prospectively purified mesenchymal stem cell population for bone tissue engineering

Adipose tissue is an ideal source of mesenchymal stem cells for bone tissue engineering: it is largely dispensable and readily accessible with minimal morbidity. However, the stromal vascular fraction (SVF) of adipose tissue is a heterogeneous cell population, which leads to unreliable bone formation. In the present study, we prospectively purified human perivascular stem cells (PSCs) from adipose tissue and compared their bone-forming capacity with that of traditionally derived SVF. PSCs are a population (sorted by fluorescence-activated cell sorting) of pericytes (CD146+CD34-CD45-) and adventitial cells (CD146-CD34+CD45-), each of which we have previously reported to have properties of mesenchymal stem cells. Here, we found that PSCs underwent osteogenic differentiation in vitro and formed bone after intramuscular implantation without the need for predifferentiation. We next sought to optimize PSCs for in vivo bone formation, adopting a demineralized bone matrix for osteoinduction and tricalcium phosphate particle formulation for protein release. Patient-matched, purified PSCs formed significantly more bone in comparison with traditionally derived SVF by all parameters. Recombinant bone morphogenetic protein 2 increased in vivo bone formation but with a massive adipogenic response. In contrast, recombinant Nel-like molecule 1 (NELL-1; a novel osteoinductive growth factor) selectively enhanced bone formation. These studies suggest that adipose-derived human PSCs are a new cell source for future efforts in skeletal regenerative medicine. Moreover, PSCs are a stem cell-based therapeutic that is readily approvable by the U.S. Food and Drug Administration, with potentially increased safety, purity, identity, potency, and efficacy. Finally, NELL-1 is a candidate growth factor able to induce human PSC osteogenesis.

The role of mesenchymal stem cells in veterinary therapeutics - a review

Adult mammalian tissue contains a population of cells known as mesenchymal stem cells (MSC), that possess the capability to secrete regenerative cytokines and to differentiate into specialised cell types. When transplanted to a site of injury MSC embed in damaged tissue and repair and regenerate the tissue by secreting cytokines. The immuno-privileged and immuno-regulatory capabilities of MSC enhance their therapeutic potential not only in autologous but also allogeneic recipients. Studies have demonstrated the beneficial effects of MSC in the treatment of a variety of clinical conditions including osteoarthritis, tendon injuries, and atopic dermatitis in domestic animals. Studies using animal models have shown promising results following MSC or MSC secretion therapy for induced injury in musculoskeletal and nervous systems and some organ diseases. This review describes the stem cell types relevant to regenerative medicine and the procedures used for isolation, identification, expansion, enrichment and differentiation of these cells. We also review the use of MSC in animal models of disease as well as diseases in the clinical veterinary setting.

Adipose-derived stem cells accelerate neovascularization in ischaemic diabetic skin flap via expression of hypoxia-inducible factor-1α

Skin flaps are frequently performed for diabetic patients in spite of countless detrimental effects of diabetes on flap survival, most of which may result from a defective response of the tissues to low oxygen tension. In this study, the authors explored the feasibility of applying human adipose-derived stem cells (ASCs) to increase the viability of random-patterned skin flaps in streptozotocin-induced diabetic mice. ASCs were isolated from the fresh human lipoaspirates and expanded ex vivo for three passages. After the elevation of caudally based random-patterned skin flaps (3 cm long and 1 cm wide), ASCs suspensions were then injected into the flap (group A). Media containing no ASCs were similarly injected as a control (group B), although nothing was injected into the flap base of mice in control group C. Flap assessments were carried out at post-operative day 7 for evaluation of flap viability. The flap survival rate of group A was significantly higher than those of groups B and C, whereas no difference was observed between groups B and C. Histological examination also demonstrated a statistically significant increase in capillary density in group A over both groups B and C. Furthermore, it was found that ASCs not only augmented the expression of vascular endothelial growth factor and hypoxia-inducible factor-1α (HIF-1α) in flap tissues from dermis of diabetes mice, but also promoted their expression in dermal fibroblasts from diabetic mice. Thus, ASCs could enhance the survival of random-patterned skin flaps in streptozotocin-induced diabetic mice via elevated expression of HIF-1α.

Augmented healing of critical-size calvarial defects by baculovirus-engineered MSCs that persistently express growth factors

Repair of large calvarial bony defects remains clinically challenging because successful spontaneous calvarial re-ossification rarely occurs. Although bone marrow-derived mesenchymal stem cells (BMSCs) genetically engineered with baculovirus (BV) for transient expression of osteogenic/angiogenic factors hold promise for bone engineering, we hypothesized that calvarial bone healing necessitates prolonged growth factor expression. Therefore, we employed a hybrid BV vector system whereby one BV expressed FLP while the other harbored the BMP2 (or VEGF) cassette flanked by Frt sequences. Transduction of rabbit BMSCs with the FLP/Frt-based BV vector led to FLP-mediated episome formation, which not only extended the BMP2/VEGF expression beyond 28 days but augmented the BMSCs osteogenesis. After allotransplantation into rabbits, X-ray, PET/CT, μCT and histological analyses demonstrated that the sustained BMP2/VEGF expression remarkably ameliorated the angiogenesis and regeneration of critical-size (8 mm) calvarial defects, when compared with the group implanted with BMSCs transiently expressing BMP2/VEGF. The prolonged expression by BMSCs accelerated the bone remodeling and regenerated the bone through the natural intramembranous pathway, filling ≈83% of the area and ≈63% of the volume in 12 weeks. These data implicated the potential of the hybrid BV vector to engineer BMSCs for sustained BMP2/VEGF expression and the repair of critical-size calvarial defects.

Adipose-Derived Stem Cells Enhance Bone Regeneration in Vascular Necrosis of the Femoral Head in the Rabbit

Osteonecrosis of the femoral head was induced in rabbits by intramuscular injection of methylprednisolone and vascular occlusion of the capital femoral epiphysis by electrocoagulation. Eight weeks later the animals received no treatment (group A), core decompression by drilling a hole (diameter 1.2 mm) from the outer cortex 2.5 cm distal to the proximal end of the greater trochanter (group B), or injection of 107 autologous adipose-derived stem cells (ADSCs) directly into the femoral head (group C). Eight weeks later, microcomputed tomography scans indicated that bone and trabecular volume and density were significantly higher in group C than in other groups. Histology indicated more new bone formation in group C than in other groups. Group C showed strong osteocalcin immunoreactivity in subchondral bone osteoblasts in the necrotic femoral head, whereas few osteocalcin-positive cells were found among osteoblasts in other groups. Thus, autologous ADSC transplantation improved osteogenesis and the microstructure of vascular deprivation-induced osteonecrotic tissue.

Cryopreservation of tissue-engineered epithelial sheets in trehalose

Tissue-engineered epidermal membranes are useful for clinical wound healing. To facilitate these products in the clinic, optimized storage methods need to be developed. We studied the efficiency of extracellular trehalose at various concentrations for cryopreserving human tissue-engineered epidermal membranes compared with that of dimethyl-sulfoxide (DMSO) used by most organ banks for cryopreserving skin grafts and artificial skin substitutes. Keratinocyte (KC) viability, proliferation and marker expression following cryopreservation in trehalose were examined with similar results to those using DMSO. Trehalose concentration (0.4m) was optimized according to the described cellular activities following cryopreservation. Artificial epidermal substitutes were then cryopreserved in trehalose at the optimized concentration. Cell viability, growth factor secretion and wound healing properties of cryopreserved artificial epidermal substitutes using nude mice were examined and compared with those of DMSO cryopreservation. Cryopreservation with trehalose enhanced human KC viability in suspension and artificial skin substitutes. In addition, trehalose cryopreservation provided fast recovery of EGF and TGF-β1 secretion by KCs after thawing. When transplanted into nude mice, trehalose-cryopreserved artificial skin repaired skin defects in a similar manner to that of a non-cryopreserved control. Moreover, trehalose-cryopreserved artificial skin resulted in engraftment and wound closure that was significantly enhanced compared with that of DMSO-cryopreserved epidermal membranes. The results indicate that the use of trehalose improves cryopreservation of tissue-engineered epithelial sheets.

The enhanced performance of bone allografts using osteogenic-differentiated adipose-derived mesenchymal stem cells

Adipose tissue was only recently considered as a potential source of mesenchymal stem cells (MSCs) for bone tissue engineering. To improve the osteogenicity of acellular bone allografts, adipose MSCs (AMSCs) and bone marrow MSCs (BM-MSCs) at nondifferentiated and osteogenic-differentiated stages were investigated in vitro and in vivo. In vitro experiments demonstrated a superiority of AMSCs for proliferation (6.1±2.3 days vs. 9.0±1.9 days between each passage for BM-MSCs, respectively, P<0.001). A significantly higher T-cell depletion (revealed by mixed lymphocyte reaction, [MLR]) was found for AMSCs (vs. BM-MSCs) at both non- and differentiated stages. Although nondifferentiated AMSCs secreted a higher amount of vascular endothelial growth factor [VEGF] in vitro (between 24 and 72 h of incubation at 0.1-21% O(2)) than BM-MSCs (P<0.001), the osteogenic differentiation induced a significantly higher VEGF release by BM-MSCs at each condition (P<0.001). After implantation in the paraspinal muscles of nude rats, a significantly higher angiogenesis (histomorphometry for vessel development (P<0.005) and VEGF expression (P<0.001)) and osteogenesis (as revealed by osteocalcin expression (P<0.001) and micro-CT imagery for newly formed bone tissue (P<0.05)) were found for osteogenic-differentiated AMSCs in comparison to BM-MSCs after 30 days of implantation. Osteogenic-differentiated AMSCs are the best candidate to improve the angio-/osteogenicity of decellularized bone allografts.

Bioreactors for bone tissue engineering

Bone tissue engineering is a promising solution for patients with bone defects that require reconstruction. This regenerative therapy consists in culturing osteogenic cells on a biodegradable substrate to obtain a bio-hybrid construct that will stimulate bone healing after implantation. This multidisciplinary technology nevertheless requires further development before it can become routine clinical practice. One challenge is to achieve three-dimensional seeding and osteogenic commitment of mesenchymal stem cells on biomaterials under sterile and reproducible conditions. For this purpose, different dynamic culture systems have been developed. This paper reviews recent advances in the field of bioreactors for bone tissue engineering. The purpose of such systems is to improve nutrient delivery to the cells and generate shear stress that may promote cell differentiation into osteoblastic phenotypes. A brief overview of the value of computational fluid dynamics for understanding the cell environment is also provided. Finally, some proposals are made regarding the use of bioreactors as safe and controllable devices that will help commit cells and biomaterials for the regeneration of bone tissue.