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

Adipose tissue stem cells in regenerative medicine

Adipose tissue-derived stem cells (ADSCs) are mesenchymal cells with the capacity for self-renewal and multipotential differentiation. This multipotentiality allows them to become adipocytes, chondrocytes, myocytes, osteoblasts and neurocytes among other cell lineages. Stem cells and, in particular, adipose tissue-derived cells, play a key role in reconstructive or tissue engineering medicine as they have already proven effective in developing new treatments. The purpose of this work is to review the applications of ADSCs in various areas of regenerative medicine, as well as some of the risks associated with treatment with ADSCs in neoplastic disease.

MAPK signaling has stage-dependent osteogenic effects on human adipose-derived stem cells in vitro

OVERVIEW

The use of pro-osteogenic growth factors, such as BMP2, in human adipose-derived stem cell (ASC) osteogenesis is well described. Because these growth factors work via signal transduction pathways, such as the mitogen-activated protein kinase (MAPK) cascade, a study of the relationship between MAPK signaling and ASC osteogenesis was conducted.

MATERIALS AND METHODS

ERK, JNK, and p38MAPK activation were measured in ASCs osteo-induced using either dexamethasone or vitamin D3 and correlated with mineralization. Activation and mineralization were also measured without dexamethasone or using the glucocorticoid, cortisone. The expression of the MAPK phosphatase, MKP1, and its relationship to mineralization was also assessed. The effect of decreasing MAPK activation on mineralization through the use of exogenous inhibitors was examined along with siRNA-knockdown and adenoviral overexpression of ERK1/2. Finally, the effect of ERK1/2 overexpression on ASCs induced on PLGA scaffolds was assessed.

RESULTS

ASC mineralization in dexamethasone or vitamin D3-induced ASCs correlated with both increased ERK1/2 and JNK1/2 activation. ASCs induced without dexamethasone also mineralized, with JNK1/2 signaling possibly mediating this event. No link between cortisone induction and MAPK signaling could be ascertained. ASCs treated with ERK, JNK, or p38MAPK inhibitors showed decreased osteogenic gene expression and diminished mineralization. Mineralization levels were also affected by viruses designed to inhibit or augment ERK1/2 expression and activity. Finally, ASC mineralization appeared to be a balance between the MAPK kinase activity and MKP1.

CONCLUSIONS

It is likely that MAPK signaling plays a significant role in ASC osteogenesis, affecting differentiation in kinase- and stage-specific manners.

Surface modification of PHBV nanofiber mats for rapid cell cultivation and harvesting

To maintain the original function of a specific tissue for therapeutic tissue engineering, an advanced cell culture surface for repeat cell proliferation is necessary. We designed a novel cell proliferation and rapid harvesting surface by combining nonwoven nanofiber mat and a thermo-responsive polymer. Nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) mats were fabricated by the electrospinning technique. A poly(N-isopropylacrylamide) (PNIPAM) thermo-responsive layer was grafted on the PHBV nanofiber mat by electron beam irradiation. The average diameter of the PNIPAM-grafted PHBV nanofibers was determined by SEM. ATR-FTIR and ESCA were used to confirm the grafting of PNIPAM onto the PHBV nanofiber surface. Water contact angles on the mats were measured in response to temperature changes. Human adipose-derived stem cells (ADSCs) were cultured on the PNIPAM-grafted PHBV nanofiber mat to investigate cell proliferation, harvesting, and functionality during repeat subculture. Detached ADSCs from each surface by low temperature treatment and trypsin-EDTA were compared by a fluorescence-activated cell sorter (FACS) using expression of stem cell membrane-specific markers such as CD-13 PE, CD-29 PE, and CD-90 FITC. The mass cultivation and intact harvesting of stem cells by low temperature treatment using a thermo-responsive PHBV nanofiber mat is a promising technique for use in regenerative medicine and stem cell therapy.

Inferior In Vivo Osteogenesis and Superior Angiogenesis of Human Adipose‐Derived Stem Cells Compared with Bone Marrow‐Derived Stem Cells Cultured in Xeno‐Free Conditions

The possibility of using adipose tissue-derived stromal cells (ATSC) as alternatives to bone marrow-derived stromal cells (BMSC) for bone repair has garnered interest due to the accessibility, high cell yield, and rapid in vitro expansion of ATSC. For clinical relevance, their bone forming potential in comparison to BMSC must be proven. Distinct differences between ATSC and BMSC have been observed in vitro and comparison of osteogenic potential in vivo is not clear to date. The aim of the current study was to compare the osteogenesis of human xenofree-expanded ATSC and BMSC in vitro and in an ectopic nude mouse model of bone formation. Human MSC were implanted with biphasic calcium phosphate biomaterials in subcutis pockets for 8 weeks. Implant groups were: BMSC, ATSC, BMSC and ATSC mixed together in different ratios, as well as MSC primed with either osteogenic supplements (250 μM ascorbic acid, 10 mM β-glycerolphosphate, and 10 nM dexamethasone) or 50 ng/ml recombinant bone morphogenetic protein 4 prior to implantation. In vitro results show osteogenic gene expression and differentiation potentials of ATSC. Despite this, ATSC failed to form ectopic bone in vivo, in stark contrast to BMSC, although osteogenic priming did impart minor osteogenesis to ATSC. Neovascularization was enhanced by ATSC compared with BMSC; however, less ATSC engrafted into the implant compared with BMSC. Therefore, in the content of bone regeneration, the advantages of ATSC over BMSC including enhanced angiogenesis, may be negated by their lack of osteogenesis and prerequisite for osteogenic differentiation prior to transplantation. Stem Cells Translational Medicine 2017;6:2160-2172.

* Calvarial Defects: Cell-Based Reconstructive Strategies in the Murine Model

Calvarial defects pose a continued clinical dilemma for reconstruction. Advancements within the fields of stem cell biology and tissue engineering have enabled researchers to develop reconstructive strategies using animal models. We review the utility of various animal models and focus on the mouse, which has aided investigators in understanding cranial development and calvarial bone healing. The murine model has also been used to study regenerative approaches to critical-sized calvarial defects, and we discuss the application of stem cells such as bone marrow-derived mesenchymal stromal cells, adipose-derived stromal cells, muscle-derived stem cells, and pluripotent stem cells to address deficient bone in this animal. Finally, we highlight strategies to manipulate stem cells using various growth factors and inhibitors and ultimately how these factors may prove crucial in future advancements within calvarial reconstruction using native skeletal stem cells.

Bone engineering by cell sheet technology to repair mandibular defects

Effectiveness of bone engineering by cell sheet technology to repair canine mandibular injuries was investigated. Cell sheets were produced from canine stem cells cultured by density gradient centrifugation and osteoblast induction. A scaffold surface of polylactic-co-glycolic acid (PLGA) copolymer was wrapped with cell sheets. Mandibular injuries were created in 12 healthy dogs followed by implantation of PLGA with (experimental group; n, 6) and without (control group; n, 6) cell sheets. The progression of the implants was examined at 3, 9, and 12 weeks postoperative. At postoperative 12 weeks, the graft mostly replaced the new bone in the experimental group, compact similar to normal bone was formed at lingual position and the broken end of the bone was normally healed. The bone mass in the control group was 2.5, which was significantly lower than the 4.5 in the experimental group. The optical density of the new bone in the experimental group was significantly higher than that in the control group. The experimental group had more haversian canal and red bone marrow and contained a larger number of lamellar bone than the control group. Overall, satisfactory bone engineering containing lamellar bone can be established by cell sheet technology, which is an ideal method to repair mandibular injuries.

Ultrastructural characteristics of ovine bone marrow-derived mesenchymal stromal cells cultured with a silicon stabilized tricalcium phosphate bioceramic

Bioceramics are being used in experimental bone engineering application in association with bone marrow derived mesenchymal stem cells (BM-MSCs) as a new therapeutic tool, but their effects on the ultrastructure of BM-MSCs are yet unknown. In this study we report the morphological features of ovine (o)BM-MSCs cultured with Skelite, a resorbable bioceramic based on silicon stabilized tricalcium phosphate (SiTCP), able to promote the repair of induced bone defect in sheep model. oBM-MSCs were isolated from the iliac crest, cultured until they reached near-confluence and incubated with SiTCP. After 48 hr the monolayers were highly damaged and only few cells adhered to the plastic. Thus, SiTCP was removed, and after washing the cells were cultured until they became confluent. Then, they were trypsinizated and processed for transmission electron microscopy (TEM) and RT-PCR analysis. RT-PCR displayed that oBM-MSCs express typical surface marker for MSCs. TEM revealed the presence of electron-lucent cells and electron-dense cells, both expressing the CD90 surface antigen. The prominent feature of electron-lucent cells was the concentration of cytoplasmic organelles around the nucleus as well as large surface blebs containing glycogen or profiles of endoplasmic reticulum. The dark cells had a multilocular appearance by the presence of peripheral vacuoles. Some dark cells contained endocytic vesicles, lysosomes, and glycogen aggregates. oBM-MSCs showed different types of specialized interconnections. The comparison with ultrastructural features of untreated oBM-MSCs suggests the light and dark cells are two distinct cell types which were differently affected by SiTCP bioceramic. Skelite cultured ovine BM-MSCs display electron-dense and electron-lucent cells which are differently affected by this bioceramic. This suggests that they could play a different role in bioceramic based therapy.

Adipose-derived stem cell therapies for bone regeneration

INTRODUCTION

Cell-based therapies exploit the heterogeneous and self-sufficient biological environment of stem cells to restore, maintain and improve tissue functions. Adipose-derived stem cells (ASCs) are, to this aim, promising cell types thanks to advantageous isolation procedures, growth kinetics, plasticity and trophic properties. Specifically, bone regeneration represents a suitable, though often challenging, target setting to test and apply ASC-based therapeutic strategies. Areas covered: ASCs are extremely plastic and secrete bioactive peptides that mediate paracrine functions, mediating their trophic actions in vivo. Numerous preclinical studies demonstrated that ASCs improve bone healing. Clinical trials are ongoing to validate the clinical feasibility of these approaches. This review is intended to define the state-of-the-art on ASCs, encompassing the biological features that make them suitable for bone regenerative strategies, and to provide an update on existing preclinical and clinical applications. Expert opinion: ASCs offer numerous advantages over other stem cells in terms of feasibility of clinical translation. Data obtained from in vivo experimentation are encouraging, and clinical trials are ongoing. More robust validations are thus expected to be achieved during the next few years, and will likely pave the way to optimized patient-tailored treatments for bone regeneration.

Effects of miR-146a on the osteogenesis of adipose-derived mesenchymal stem cells and bone regeneration

Increasing evidence has indicated that bone morphogenetic protein 2 (BMP2) coordinates with microRNAs (miRNAs) to form intracellular networks regulating mesenchymal stem cells (MSCs) osteogenesis. This study aimed to identify specific miRNAs in rat adipose-derived mesenchymal stem cells (ADSCs) during BMP2-induced osteogenesis, we selected the most significantly down-regulated miRNA, miR-146a, to systematically investigate its role in regulating osteogenesis and bone regeneration. Overexpressing miR-146a notably repressed ADSC osteogenesis, whereas knocking down miR-146a greatly promoted this process. Drosophila mothers against decapentaplegic protein 4 (SMAD4), an important co-activator in the BMP signaling pathway, was miR-146a’s direct target and miR-146a exerted its repressive effect on SMAD4 through interacting with 3′-untranslated region (3′-UTR) of SMAD4 mRNA. Furthermore, knocking down SMAD4 attenuated the ability of miR-146a inhibitor to promote ADSC osteogenesis. Next, transduced ADSCs were incorporated with poly(sebacoyl diglyceride) (PSeD) porous scaffolds for repairing critical-sized cranial defect, the treatment of miR-146a inhibitor greatly enhanced ADSC-mediated bone regeneration with higher expression levels of SMAD4, Runt-related transcription factor 2 (Runx2) and Osterix in newly formed bone. In summary, our study showed that miR-146a negatively regulates the osteogenesis and bone regeneration from ADSCs both in vitro and in vivo.

In vitro osteogenic induction of bone marrow mesenchymal stem cells with a decellularized matrix derived from human adipose stem cells and in vivo implantation for bone regeneration

Tissue engineering technology that adopts mesenchymal stem cells combined with scaffolds presents a promising strategy for tissue regeneration.

Development of demineralized bone matrix-based implantable and biomimetic microcarrier for stem cell expansion and single-step tissue-engineered bone graft construction

Tissue engineered bone grafts (TEBG) using mesenchymal stem cells (MSCs) demonstrate great potential for bone defect treatment.

Is there a role of coral bone substitutes in bone repair?

Xenogeneic bone graft materials are an alternative to autologous bone grafting. Among such implants, coralline-derived bone grafts substitutes have a long track record as safe, biocompatible and osteoconductive graft materials. In this review, we present the available literature surrounding their use with special focus on the commercially available graft materials. Corals thanks to their chemical and structural characteristics similar to those of the human cancellous bone have shown great potential but clinical data presented to date is ambiguous with both positive and negative outcomes reported. Correct formulation and design of the graft to ensure adequate osteo-activity and resorption appear intrinsic to a successful outcome.

Laminated electrospun nHA/PHB-composite scaffolds mimicking bone extracellular matrix for bone tissue engineering

Electrospinning is an effective means to generate nano- to micro-scale polymer fibers resembling native extracellular matrix for tissue engineering. However, a major problem of electrospun materials is that limited pore size and porosity may prevent adequate cellular infiltration and tissue ingrowth. In this study, we first prepared thin layers of hydroxyapatite nanoparticle (nHA)/poly-hydroxybutyrate (PHB) via electrospinning. We then laminated the nHA/PHB thin layers to obtain a scaffold for cell seeding and bone tissue engineering. The results demonstrated that the laminated scaffold possessed optimized cell-loading capacity. Bone marrow mesenchymal stem cells (MSCs) exhibited better adherence, proliferation and osteogenic phenotypes on nHA/PHB scaffolds than on PHB scaffolds. Thereafter, we seeded MSCs onto nHA/PHB scaffolds to fabricate bone grafts. Histological observation showed osteoid tissue formation throughout the scaffold, with most of the scaffold absorbed in the specimens 2months after implantation, and blood vessels ingrowth into the graft could be observed in the graft. We concluded that electrospun and laminated nanoscaled biocomposite scaffolds hold great therapeutic potential for bone regeneration.

Porous 3D implants of degradable poly-3-hydroxybutyrate used to enhance regeneration of rat cranial defect

The study describes preparation and testing of porous 3D implants of natural degradable polymer of 3-hydroxybutyric acid P(3HB) for regeneration of bone tissue defects. The ability of the P(3HB) implants to favor attachment and facilitate proliferation and directed differentiation of mesenchymal stem cells (MSCs) was studied in the culture of MSCs isolated from bone marrow and adipose tissue. Tissue-engineered hybrid systems (grafts) constructed using P(3HB) and P(3HB) in combination with osteoblasts were used in experiments on laboratory animals (n = 48) with bone defect model. The defect model (5 mm in diameter) was created in the rat parietal bone, and filling of the defect by the new bone tissue was monitored in the groups of animals with P(3HB) implants, with commercial material, and without implants (negative control). Computed tomography (CT) and histologic examination showed that after 120 days, in the group with the osteoblast-seeded P(3HB) implants, the defect was completely closed; in the group with the cell-free P(3HB) implants, the remaining defect was no more than 10% of the initial one (0.5 mm); in both the negative and positive controls, the size of the defect was about 1.0-1.2 mm. These results suggest that P(3HB) has good potential as osteoplastic material for reconstructive osteogenesis. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 566-577, 2017.

A Selective Cell Population from Dermis Strengthens Bone Regeneration

Finding appropriate seed cells for bone tissue engineering remains a significant challenge. Considering that skin is the largest organ, we hypothesized that human bone morphogenetic protein receptor type IB (BmprIB)+ dermal cells could have enhanced osteogenic capacity in the healing of critical-sized calvarial defects in an immunodeficient mouse model. In this study, immunohistochemical staining revealed that BmprIB was expressed throughout reticular dermal cells; the positive expression rate of BmprIB was 3.5% ± 0.4% in freshly separated dermal cells, by flow cytometry. Furthermore, in vitro osteogenic capacity of BmprIB+ cells was confirmed by osteogenic-related staining and marker gene expression compared with unsorted dermal cells. In vivo osteogenic capacity was demonstrated by implantation of human BmprIB+ cell/coral constructs in the treatment of 4-mm diameter calvarial defects in an immunodeficient mouse model compared with implantation of unsorted cell/coral constructs and coral scaffold alone. These results indicate that the selective cell population BmprIB from human dermis is a promising osteogenic progenitor cell that can be a large-quantity and high-quality cell source for bone tissue engineering and regeneration. Stem Cells Translational Medicine 2017;6:306-315.

Administration of adipose-derived stem cells enhances vascularity, induces collagen deposition, and dermal adipogenesis in burn wounds

Current treatment options for severe burn wounds are often insufficient in reconstructing skin and soft tissue defects. Adipose-derived stem cells (ASCs), a readily available source of multipotent stem cells, represent a promising therapy for the treatment of full-thickness burn wounds. Full-thickness burn wounds were created on the paraspinal region of athymic mice. A one-time, sub-eschar injection of 6.8×10(6) ASCs in PBS or PBS alone was administered at 24-h postoperatively. Time to healing was quantified using Image J analysis. At days 4, 7, 14, and 21, mice were sacrificed and tissues were excised for molecular and histological analysis. ASCs were able to survive in burn wounds as determined by the presence of PKH labeling and human PPARγ expression within the wounds. CD-31 staining demonstrated increased vascularity in ASC-treated wounds at POD 4 (p<0.05). Molecular studies showed enhanced adipogenesis, as well as type III and type I collagen deposition in the ASC treated group (p<0.05). An increase in the mRNA expression ratio of type III to type I collagen was also observed following ASC treatment (p<0.05). By enhancing vascularity, collagen deposition, and adipogenesis, ASCs show promise as an adjunctive therapy for the current treatment of full thickness burn wounds.

Inhibition of Osteoclast Differentiation and Bone Resorption by Bisphosphonate-conjugated Gold Nanoparticles

In recent years, gold nanoparticles (GNPs) have been reported to affect the regeneration of bone tissue. The goal of this study was to improve bone tissue regeneration by using targeted GNPs. We fabricated a functionalized GNPs conjugated with alendronate (ALD), of the bisphosphonate group. Subsequently, the ALD, GNPs, and ALD conjugated GNPs (GNPs-ALD) were analyzed by ultraviolet-visible absorbance (UV-vis) spectrophotometer, Attenuated total reflectance Fourier transform infrared spectrometer (ATR-FTIR), and thermo gravimetric analysis (TGA). The prepared GNPs-ALD were used to investigate their inhibitory effects on the receptor activator of nuclear factor- κb ligand (RANKL)-induced osteoclastogenesis in bone marrow-derived macrophages (BMMs). Additionally, the GNPs-ALD were applied to ovariectomy (OVX)-induced osteoporotic mice and the experiments were evaluated. ALD was found to be successfully conjugated to the GNPs surface, and it displayed significant adhesion onto the bone surface. The in-vitro study indicated that the GNPs, ALD and GNPs-ALD suppressed osteoclast formation in a dose-dependent manner. Furthermore, in the OVX mouse model, the mice treated GNPs-ALD had higher bone density as compared to other OVX mice groups. The results from these tests indicated that GNPs-ALD can be useful agents for preventing and treating osteoporosis.

Electrical impedance spectroscopy - a potential method for the study and monitoring of a bone critical-size defect healing process treated with bone tissue engineering and regenerative medicine approaches

The development of strategies of bone tissue engineering and regenerative medicine has been drawing considerable attention to treat bone critical-size defects (CSDs). Notably, new strategies and/or treatment approaches always require appropriate tools to track the healing process so as to evaluate their success. In this paper, we present the development of a novel approach for the non-invasive, yet real-time, monitoring and assessment of bone CSDs treated with biomaterials and biomedical approaches. For this, we employed the technique of electrical impedance spectroscopy (EIS) to quantitatively monitor and assess the changes in electrical impedance, and thus the regeneration process. In our in vitro tests, we examined the biochemical changes of the fracture area and investigated the influence of collagen and hydroxyapatite on the changes in electrical impedance by EIS, thus inferring the changes in bone regeneration and structure. Based on this success, we further demonstrated, in real time, the process of regeneration of the traumatic area in an in vivo rabbit model. Our electrical-impedance data of the experiment groups, i.e., the ones treated with natural coral and bone morphogenetic protein-2 (BMP-2), revealed that each group has its unique impedance graph characteristics, which are directly associated with the degree of regeneration. For comparison, we also employed radiography, gross anatomy, and histological analyses in examination. Our results illustrate that EIS holds considerable potential as a non-invasive tool for monitoring, in real time, the healing of bone CSDs by allowing for quantitatively characterizing the changes of both hydroxyapatite and collagen.

Electrospun silk fibroin/poly(lactide-co-ε-caprolactone) nanofibrous scaffolds for bone regeneration

Background

Tissue engineering has become a promising therapeutic approach for bone regeneration. Nanofibrous scaffolds have attracted great interest mainly due to their structural similarity to natural extracellular matrix (ECM). Poly(lactide-co-ε-caprolactone) (PLCL) has been successfully used in bone regeneration, but PLCL polymers are inert and lack natural cell recognition sites, and the surface of PLCL scaffold is hydrophobic. Silk fibroin (SF) is a kind of natural polymer with inherent bioactivity, and supports mesenchymal stem cell attachment, osteogenesis, and ECM deposition. Therefore, we fabricated hybrid nanofibrous scaffolds by adding different weight ratios of SF to PLCL in order to find a scaffold with improved properties for bone regeneration.

Methods

Hybrid nanofibrous scaffolds were fabricated by blending different weight ratios of SF with PLCL. Human adipose-derived stem cells (hADSCs) were seeded on SF/PLCL nanofibrous scaffolds of various ratios for a systematic evaluation of cell adhesion, proliferation, cytotoxicity, and osteogenic differentiation; the efficacy of the composite of hADSCs and scaffolds in repairing critical-sized calvarial defects in rats was investigated.

Results

The SF/PLCL (50/50) scaffold exhibited favorable tensile strength, surface roughness, and hydrophilicity, which facilitated cell adhesion and proliferation. Moreover, the SF/PLCL (50/50) scaffold promoted the osteogenic differentiation of hADSCs by elevating the expression levels of osteogenic marker genes such as BSP, Ocn, Col1A1, and OPN and enhanced ECM mineralization. In vivo assays showed that SF/PLCL (50/50) scaffold improved the repair of the critical-sized calvarial defect in rats, resulting in increased bone volume, higher trabecular number, enhanced bone mineral density, and increased new bone areas, compared with the pure PLCL scaffold.

Conclusion

The SF/PLCL (50/50) nanofibrous scaffold facilitated hADSC proliferation and osteogenic differentiation in vitro and further promoted new bone formation in vivo, suggesting that the SF/PLCL (50/50) nanofibrous scaffold holds great potential in bone tissue regeneration.

The use of SHP-2 gene transduced bone marrow mesenchymal stem cells to promote osteogenic differentiation and bone defect repair in rat

Bone tissue engineering is a promising approach for bone regeneration, in which growth factors play an important role. The tyrosine phosphatase Src-homology region 2-containing protein tyrosine phosphatase 2 (SHP2), encoded by the PTPN11 gene, is essential for the differentiation, proliferation and metabolism of osteoblasts. However, SHP-2 has never been systematically studied for its effect in osteogenesis. We predicted that overexpression of SHP-2 could promote bone marrow-derived mesenchymal stem cell (BMSC)osteogenic differentiation and SHP-2 transduced BMSCs could enhance new bone formation, determined using the following study groups: (1) BMSCs transduced with SHP-2 and induced with osteoblast-inducing liquid (BMSCs/SHP-2/OL); (2) BMSCs transduced with SHP-2 (BMSCs/-SHP-2); (3) BMSCs induced with osteoblast-inducing liquid (BMSCs/OL) and (4) pure BMSCs. Cells were assessed for osteogenic differentiation by quantitative real-time polymerase chain reaction analysis, western blot analysis, alkaline phosphatase activity and alizarin red S staining. For in vivo assessment, cells were combined with beta-tricalcium phosphate scaffolds and transplanted into rat calvarial defects for 8 weeks. Following euthanasia, skull samples were explanted for osteogenic evaluation, including micro-computed tomography measurement, histology and immunohistochemistry staining. SHP-2 and upregulation of its gene promoted BMSC osteogenic differentiation and therefore represents a potential new therapeutic approach to bone repair. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1871-1881, 2016.

MicroRNAs and Bone Regeneration

Bone has multiple functions, both morphologically and physiologically, and it frequently features in the pathological condition, including fracture and osteoporosis. For bone regeneration therapy, the regulation of osteoblast differentiation is important. MicroRNA (miRNA)s are short noncoding RNA which regulate gene expression at the post-transcriptional level. MiRNAs play an important role not only in a variety of other cellular processes including differentiation, proliferation, and apoptosis but also in the pathogenesis of human diseases. Recently, miRNAs have been known to participate in osteoblast differentiation by regulating several signaling pathways including transcription factors. New insight into the mechanism during osteogenes is affected by miRNAs has been gained. Moreover, therapeutic trials for bone diseases including osteoporosis, fracture and bone defects targeting miRNAs have been examined in animal models. MiRNA therapy will enable development of a bone regeneration therapy.

Chemically Defined and Xeno-Free Cryopreservation of Human Adipose-Derived Stem Cells

The stromal compartment of adipose tissue harbors multipotent cells known as adipose-derived stem cells (ASCs). These cells can differentiate into various lineages including osteogenic, chrondrogenic, adipogenic, and neurogenic; this cellular fraction may be easily obtained in large quantities through a clinically safe liposuction procedure. Therefore, ASCs offer exceptional opportunities for tissue engineering and regenerative medicine. However, current practices involving ASCs typically use fetal bovine serum (FBS)-based cryopreservation solutions that are associated with risks of immunological reactions and of transmitting infectious diseases and prions. To realize clinical applications of ASCs, serum- and xeno-free defined cryopreservation methods are needed. To this end, an animal product-free chemically defined cryopreservation medium was formulated by adding two antioxidants (reduced glutathione and ascorbic acid 2-phosphate), two polymers (PVA and ficoll), two permeating cryoprotectants (ethylene glycol and dimethylsulfoxide), a disaccharide (trehalose), and a calcium chelator (EGTA) to HEPES-buffered DMEM/F12. To limit the number of experimental groups, the concentration of trehalose, both polymers, and EGTA was fixed while the presence of the permeating CPAs and antioxidants was varied. ASCs suspended either in different versions of the defined medium or in the conventional undefined cryopreservation medium (10% dimethylsulfoxide+10% DMEM/F12+80% serum) were cooled to -70°C at 1°C/min before being plunged into liquid nitrogen. Samples were thawed either in air or in a water bath at 37°C. The presence of antioxidants along with 3.5% concentration of each penetrating cryoprotectant improved the freezing outcome to the level of the undefined cryopreservation medium, but the plating efficiency was still lower than that of unfrozen controls. Subsequently, increasing the concentration of both permeating cryoprotectants to 5% further improved the plating efficiency to the level of unfrozen controls. Moreover, ASCs cryopreserved in this defined medium retained their multipotency and chromosomal normality. These results are of significance for tissue engineering and clinical applications of stem cells.

Repair of critical size defects using bioactive glass seeded with adipose-derived mesenchymal stem cells

Bioactive glass has been demonstrated as a biocompatible bone substitute. However bone healing process can be prolonged due to late resorption of the material. Adipose derived stem cells (ASC) have osteogenic differentiation potential and hence can be a cell source for bone regeneration. The aim of this study was to test whether combination of bioactive glass with ASCs would enhance bone regeneration. Following creation of critical sized defects on the calvaria of 32 Wistar rats, the animals were randomly divided into four groups: Group C (control): Defects were left untreated; Group G: Defects were covered with autologous bone graft; Group BG: Defects were filled with bioactive glass; Group BG/ASC: Defects were filled with bioactive glass seeded with ASCs. The defect size was significantly greater in Group C compared to all other groups. Bone density was significantly lower in Group C compared to Group G and Group BG/ASC. Bone regeneration score of Group C was significantly lower than other groups. Group BG/ASC demonstrated lamellar bone and havers canal formation. The results of this study demonstrated that bioactive glass implanted with ASC is a biocompatible construct stimulating radiologically and histologically evident bone regeneration similar to autologous bone grafting. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1002-1008, 2017.

Addition of Adipose-Derived Stem Cells to Mesenchymal Stem Cell Sheets Improves Bone Formation at an Ectopic Site

To determine the effect of adipose-derived stem cells (ADSCs) added to bone marrow-derived mesenchymal stem cell (MSC) sheets on bone formation at an ectopic site. We isolated MSCs and ADSCs from the same rabbits. We then prepared MSC sheets for implantation with or without ADSCs subcutaneously in the backs of severe combined immunodeficiency (SCID) mice. We assessed bone formation at eight weeks after implantation by micro-computed tomography and histological analysis. In osteogenic medium, MSCs grew to form multilayer sheets containing many calcium nodules. MSC sheets without ADSCs formed bone-like tissue; although neo-bone and cartilage-like tissues were sparse and unevenly distributed by eight weeks after implantation. In comparison, MSC sheets with ADSCs promoted better bone regeneration as evidenced by the greater density of bone, increased mineral deposition, obvious formation of blood vessels, large number of interconnected ossified trabeculae and woven bone structures, and greater bone volume/total volume within the composite constructs. Our results indicate that although sheets of only MSCs have the potential to form tissue engineered bone at an ectopic site, the addition of ADSCs can significantly increase the osteogenic potential of MSC sheets. Thus, the combination of MSC sheets with ADSCs may be regarded as a promising therapeutic strategy to stimulate bone regeneration.

Obesity inhibits the osteogenic differentiation of human adipose-derived stem cells

Background

Craniomaxillofacial defects secondary to trauma, tumor resection, or congenital malformations are frequent unmet challenges, due to suboptimal alloplastic options and limited autologous tissues such as bone. Significant advances have been made in the application of adipose-derived stem/stromal cells (ASCs) in the pre-clinical and clinical settings as a cell source for tissue engineering approaches. To fully realize the translational potential of ASCs, the identification of optimal donors for ASCs will ensure the successful implementation of these cells for tissue engineering approaches. In the current study, the impact of obesity on the osteogenic differentiation of ASCs was investigated.

Methods

ASCs isolated from lean donors (body mass index <25; lnASCs) and obese donors (body mass index >30; obASCs) were induced with osteogenic differentiation medium as monolayers in an estrogen-depleted culture system and on three-dimensional scaffolds. Critical size calvarial defects were generated in male nude mice and treated with scaffolds implanted with lnASCs or obASCs.

Results

lnASCs demonstrated enhanced osteogenic differentiation in monolayer culture system, on three-dimensional scaffolds, and for the treatment of calvarial defects, whereas obASCs were unable to induce similar levels of osteogenic differentiation in vitro and in vivo. Gene expression analysis of lnASCs and obASCs during osteogenic differentiation demonstrated higher levels of osteogenic genes in lnASCs compared to obASCs.

Conclusion

Collectively, these results indicate that obesity reduces the osteogenic differentiation capacity of ASCs such that they may have a limited suitability as a cell source for tissue engineering.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0776-1) contains supplementary material, which is available to authorized users.

Mesenchymal Stem Cells for Osteochondral Tissue Engineering

Mesenchymal stem cells (MSC) are of major interest in regenerative medicine, as they are easily harvested from a variety of sources (including bone marrow and fat aspirates) and they are able to form a range of mesenchymal tissues, in vitro and in vivo. We focus here on the use of MSCs for engineering of cartilage, bone, and complex osteochondral tissue constructs, using protocols that replicate some aspects of natural mesodermal development. For engineering of human bone, we discuss some of the current advances, and highlight the use of perfusion bioreactors for supporting anatomically exact human bone grafts. For engineering of human cartilage, we discuss the limitations of current approaches, and highlight engineering of stratified, mechanically functional human cartilage interfaced with bone by mesenchymal condensation of MSCs. Taken together, current advances enable engineering of physiologically relevant bone, cartilage and osteochondral composites, and physiologically relevant studies of osteochondral development and disease.

TWIST1 silencing enhances in vitro and in vivo osteogenic differentiation of human adipose-derived stem cells by triggering activation of BMP-ERK/FGF signaling and TAZ upregulation

Mesenchymal stem cells (MSCs) show promise for cellular therapy and regenerative medicine. Human adipose tissue-derived stem cells (hASCs) represent an attractive source of seed cells in bone regeneration. How to effectively improve osteogenic differentiation of hASCs in the bone tissue engineering has become a very important question with profound translational implications. Numerous regulatory pathways dominate osteogenic differentiation of hASCs involving transcriptional factors and signaling molecules. However, how these factors combine with each other to regulate hASCs osteogenic differentiation still remains to be illustrated. The highly conserved developmental proteins TWIST play key roles for transcriptional regulation in mesenchymal cell lineages. This study investigates TWIST1 function in hASCs osteogenesis. Our results show that TWIST1 shRNA silencing increased the osteogenic potential of hASCs in vitro and their skeletal regenerative ability when applied in vivo. We demonstrate that the increased osteogenic capacity observed with TWIST1 knockdown in hASCs is mediated through endogenous activation of BMP and ERK/FGF signaling leading, in turn, to upregulation of TAZ, a transcriptional modulator of MSCs differentiation along the osteoblast lineage. Inhibition either of BMP or ERK/FGF signaling suppressed TAZ upregulation and the enhanced osteogenesis in shTWIST1 hASCs. Cosilencing of both TWIST1 and TAZ abrogated the effect elicited by TWIST1 knockdown thus, identifying TAZ as a downstream mediator through which TWIST1 knockdown enhanced osteogenic differentiation in hASCs. Our functional study contributes to a better knowledge of molecular mechanisms governing the osteogenic ability of hASCs, and highlights TWIST1 as a potential target to facilitate in vivo bone healing.

Milestones Contributing to the Evolution of Craniofacial Surgery

Craniofacial surgery (CFS) has a rich history of collaboration with a wide variety of surgical and nonsurgical specialties. This has resulted in a large volume of publications across this spectrum of subspecialties cataloging the advancements across the field. The authors aim to analyze the characteristics of the most cited articles in CFS. A literature search was performed using the Thomson/Reuters Web of Knowledge database to identify the top 50 most cited articles in CFS. The articles were analyzed for journal distribution, total citations, year of publication, citations per year, number of authors, type of article, institution, departmental affiliation, national affiliation, and top contributors. The articles were extracted from an assortment of 21 journals. The number of citations per article ranged from 115 to 1092 (average of 185). Forty-eight percent of articles were published in the 1990s, and 22% in the 2000s. The average number of years since publication until the present time was 21.34 (range 6-45 y). The most cited article (1092 citations and 52 citations/y) was an article by McCarthy et al on human mandible lengthening via gradual distraction. Departmental distribution indicated that the majority were attributable to departments of Plastic and Reconstructive Surgery for 21 articles (42%). Twenty articles were categorized under cranial defect/bone substitutes, 12 under craniosynostosis, 7 under surgical modeling, 6 under distraction osteogenesis, and the remaining 5 under other. These articles qualitatively represent important milestones in CFS. This study affirms the potential value of "number of citations" as a meaningful metric when assessing the importance of an article within CFS.

Modulation of keratin in adhesion, proliferation, adipogenic, and osteogenic differentiation of porcine adipose-derived stem cells

Recently, keratin attracts tremendous interest because of its intrinsic ability to interact with different cells. It has the potential to serve as a controllable extracellular matrix protein that can be used to demonstrate cell mechanism and cell-matrix interaction. However, there have been relatively few studies on the effects of keratin on stem cells. In the present work, we study the effects of human keratin on porcine adipose-derived stem cells (pASCs) and a series of selective cell lines: 3T3 fibroblasts, Madin-Darby canine kidney (MDCK) cells, and MG63 osteoblasts. Relative to un-treated culture plate, our results showed that keratin coating substrates promote cell adhesion and proliferation to above cell lines. Keratin also improved pASCs adhesion, proliferation, and enhanced cell viability. Evaluation of genetic markers showed that adipogenic and osteogenic differentiations of pASCs can be successfully induced, thus demonstrating that keratin did not influence the stemness of pASCs. Furthermore, keratin improved adipogenic differentiations of pASCs in terms of up-regulations in lipoprotein lipase, peroxisome proliferator-activated receptor gamma, and CCAAT-enhancer-binding protein alpha. The osteogenic markers type I collagen, runt-related transcription factor 2, and vitamin D receptor were also upregulated when pASCs cultured on keratin substrates. Therefore, keratin can serve as a biological derived material for surface modification and scaffold fabrication for biomedical purpose. The combination of keratin with stem cells may be a potential candidate for tissue repair in the field of regenerative medicine. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 180-192, 2017.

Some Physical, Chemical, and Biological Parameters of Samples of Scleractinium Coral Aquaculture Skeleton Used for Reconstruction/Engineering of the Bone Tissue

Physical and chemical (phase and chemical composition, dynamics of resorption, and strength properties), and biological (cytological compatibility and scaffold properties of the surface) properties of samples of scleractinium coral skeletons from aquacultures of three types and corresponding samples of natural coral skeletons (Pocillopora verrucosa, Acropora formosa, and Acropora nobilis) were studied. Samples of scleractinium coral aquaculture skeleton of A. nobilis, A. formosa, and P. verrucosa met the requirements (all study parameters) to materials for osteoplasty and 3D-scaffolds for engineering of bone tissue.

Comprehensive Review of Adipose Stem Cells and Their Implication in Distraction Osteogenesis and Bone Regeneration

Bone is one of the most dynamic tissues in the human body that can heal following injury without leaving a scar. However, in instances of extensive bone loss, this intrinsic capacity of bone to heal may not be sufficient and external intervention becomes necessary. Several techniques are available to address this problem, including autogenous bone grafts and allografts. However, all these techniques have their own limitations. An alternative method is the technique of distraction osteogenesis, where gradual and controlled distraction of two bony segments after osteotomy leads to induction of new bone formation. Although distraction osteogenesis usually gives satisfactory results, its major limitation is the prolonged duration of time required before the external fixator is removed, which may lead to numerous complications. Numerous methods to accelerate bone formation in the context of distraction osteogenesis have been reported. A viable alternative to autogenous bone grafts for a source of osteogenic cells is mesenchymal stem cells from bone marrow. However, there are certain problems with bone marrow aspirate. Hence, scientists have investigated other sources for mesenchymal stem cells, specifically adipose tissue, which has been shown to be an excellent source of mesenchymal stem cells. In this paper, the potential use of adipose stem cells to stimulate bone formation is discussed.

Stem cell therapy for bone repair: a systematic review and meta-analysis of preclinical studies with large animal models

AIM

Injury to bone is a significant clinical challenge, due to its limited regenerative capacity. The current methods of repairing bone defect are surgical, highly invasive and not always successful. A systematic review and meta-analysis of preclinical studies involving large animals with bone defects were conducted to determine the treatment outcomes with stem cell therapies.

METHODS

A random effects meta-analysis of the available studies was conducted to assess the treatment outcomes including the rate of new bone formation and new bone mineral density (BMD). Stratified analyses were also conducted by separating studies based on each characteristic independently.

RESULTS

Pooled analysis of 20 preclinical studies showed a significant beneficial effect of stem cell therapy in increasing new bone formation (17.79%, 95% confidence interval [CI], 10.54, 25.03; P < 0.001) and BMD (276.94 mg cm(-2) , 95% CI, 62.71, 491.17; P < 0.001) for disease amelioration. Regarding new bone formation, a statistical improvement was similarly detected from randomized controlled trial groups (17.06%, 95% CI, 8.87, 25.24; P < 0.001) and cohort groups (17.43%, 95% CI, 10.79, 24.07; P < 0.001). Exploratory stratified analysis yielded significant predictors of new bone formation including cell number (<10(7) vs. ≥10(7) ; P = 0.048) and the route of cell delivery (combining with matrix scaffold showed more effect than direct cell injection, P = 0.041). The effect of stem cell therapy diminished after 12 weeks.

CONCLUSION

The study results suggest that stem cell therapy improves new bone formation and BMD in bone defect models. Future trials should focus on the transplantation of ≥10(7) stem cells, especially using slow release biodegradable scaffolds or repetitive cell injections.

Subcutaneous Construction of Engineered Adipose Tissue with Fat Lobule-Like Structure Using Injectable Poly-Benzyl-L-Glutamate Microspheres Loaded with Adipose-Derived Stem Cells

Porous microcarriers were fabricated from synthesized poly(γ-benzyl-L-glutamate) (PBLG) polymer to engineer adipose tissue with lobule-like structure via the injectable approach. The adipogenic differentiation of human adipose-derived stem cells (hASCs) seeded on porous PBLG microcarriers was determined by adipogenic gene expression and glycerol-3-phosphate dehydrogenase enzyme activity. In vitro adipogenic cultivation was performed for 7 days, and induced hASC/PBLG complex (Adi-ASC/PBLG group) was subcutaneously injected into nude mice. Injections of PBLG microcarriers alone (PBLG group) and non-induced hASC/PBLG complex (ASC/PBLG group) served as controls. Newly formed tissues were harvested after 4 and 8 weeks. Generation of subcutaneous adipose tissue with typical lobule-like structure separated by fibrous septa was observed upon injection of adipogenic-induced hASC/microsphere complex. Adipogenesis significantly increased in the Adi-ASC/PBLG group compared with the control groups. The angiogenesis in the engineered adipose tissue was comparable to that in normal tissue as determined by capillary density and luminal diameter. Cell tracking assay demonstrated that labeled hASCs remained detectable in the neo-generated tissues 8 weeks post-injection using green fluorescence protein-labeled hASCs. These results indicate that adipose tissue with typical lobule-like structure could be engineered using injectable porous PBLG microspheres loaded with adipogenic-induced hASCs.

A comparative morphometric analysis of biodegradable scaffolds as carriers for dental pulp and periosteal stem cells in a model of bone regeneration

Bone regeneration and bone fixation strategies in dentistry utilize scaffolds containing regenerating-competent cells as a replacement of the missing bone portions and gradually replaced by autologous tissues. Mesenchymal stem cells represent an ideal cell population for scaffold-based tissue engineering. Among them, dental pulp stem cells (DPSCs) and periosteal stem cells (PeSCs) have the potential to differentiate into a variety of cell types including osteocytes, suggesting that they can be used with this purpose. However, data on bone regeneration properties of these types of cells in scaffold-based tissue engineering are yet insufficient.In this study, we evaluated temporal dynamic bone regeneration (measured as a percentage of bone volume on the total area of the defect) induced by DPSCs or PeSCs when seeded with different scaffolds to fill critical calvarial defects in SCID Beige nude mice. Two commercially available scaffolds (granular deproteinized bovine bone with 10% porcine collagen and granular β;-tricalcium phosphate) and one not yet introduced on the market (a sponge of agarose and nanohydroxyapatite) were used. The results showed that tissue-engineered constructs did not significantly improve bone-induced regeneration process when compared with the effect of scaffolds alone. In addition, the data also showed that the regeneration induced by β;-tricalcium phosphate alone was higher after 8 weeks than that of scaffold seeded with the 2 stem cell lines. Altogether these findings suggest that further studies are needed to evaluate the potential of DPSCs and PeSCs in tissue construct and identify the appropriate conditions to generate bone tissue in critical-size defects.

MiRNA inhibition in tissue engineering and regenerative medicine

MicroRNAs (miRNAs) are noncoding RNAs that provide an endogenous negative feedback mechanism for translation of messenger RNA (mRNA) into protein. Single miRNAs can regulate hundreds of mRNAs, enabling miRNAs to orchestrate robust biological responses by simultaneously impacting multiple gene networks. MiRNAs can act as master regulators of normal and pathological tissue development, homeostasis, and repair, which has motivated expanding efforts toward the development of technologies for therapeutically modulating miRNA activity for regenerative medicine and tissue engineering applications. This review highlights the tools currently available for miRNA inhibition and their recent therapeutic applications for improving tissue repair.

Influence of Immunogenicity of Allogeneic Bone Marrow Mesenchymal Stem Cells on Bone Tissue Engineering

Allogeneic bone marrow mesenchymal stem cell (allo-BMSC)-based tissue-engineered bone (TEB) has great potential for bone defect repair. However, the immunogenicities and biological roles of allo-BMSCs are still controversial. In this study, we established an animal model of critical-sized mandibular defect in beagle dogs and compared the repairing effects of allo-BMSC-based TEB with autogenic BMSC (auto-BMSC)-based TEB without the administration of immunosuppressants. During the first 2 weeks postimplantation, a transient immune response in the allo-BMSC group was detected with an increase in proinflammation cytokines TNF-α, IFN-γ, and IL-2, a declination of anti-inflammation cytokine IL-10, and an increase in percentages of CD4(+) and CD8(+) T-cell subsets in peripheral blood. Nevertheless, there was no significant difference in bone union achievement, bone mineral density, and biomechanical properties between the two groups at 12 and 24 weeks postimplantation. Further subcutaneous implantation of allo-BMSCs/scaffold also exhibited the similar transient immune responses in the first 2 weeks postimplantation but followed by a decreased bone formation at 4 and 8 weeks postimplantation. These findings indicate that allo-BMSCs can induce a transient immunoreaction, which may temporally delay the osteogenesis of allo-BMSC/scaffold complex in early stage of in vivo implantation, whereas the long-term engineered bone formation was not affected.

Allogeneic adipose-derived stem cells regenerate bone in a critical-sized ulna segmental defect

Adipose-derived stem cells (ASCs) with multilineage potential can be induced into osteoblasts, adipocytes and chondrocytes. ASCs as seed cell are widely used in the field of tissue engineering, but most studies either use autologous cells as the source or an immunodeficient animal as the host. In our present study, we explored the feasibility of applying allogeneic ASCs and demineralized bone matrix (DBM) scaffolds for repairing tubular bone defects without using immunosuppressive therapy. Allogeneic ASCs were expanded and seeded on DBM scaffolds and induced to differentiate along the osteogenic lineage. Eight Sprague-Dawley (SD) rats were used in this study and bilateral critical-sized defects (8 mm) of the ulna were created and divided into two groups: with ASC-DBM constructs or DBM alone. The systemic immune response and the extent of bone healing were evaluated post-operatively. Twenty-four weeks after implantation, digital radiography (DR) testing showed that new bones had formed in the experimental group. By contrast, no bone tissue formation was observed in the control group. This study demonstrated that allogeneic ASCs could promote bone regeneration and repair tubular bone defects combined with DBM by histologically typical bone without systemic immune response.

Layer-by-layer paper-stacking nanofibrous membranes to deliver adipose-derived stem cells for bone regeneration

Bone tissue engineering through seeding of stem cells in three-dimensional scaffolds has greatly improved bone regeneration technology, which historically has been a constant challenge. In this study, we researched the use of adipose-derived stem cell (ADSC)-laden layer-by-layer paper-stacking polycaprolactone/gelatin electrospinning nanofibrous membranes for bone regeneration. Using this novel paper-stacking method makes oxygen distribution, nutrition, and waste transportation work more efficiently. ADSCs can also secrete multiple growth factors required for osteogenesis. After the characterization of ADSC surface markers CD29, CD90, and CD49d using flow cytometry, we seeded ADSCs on the membranes and found cells differentiated, with significant expression of the osteogenic-related proteins osteopontin, osteocalcin, and osteoprotegerin. During 4 weeks in vitro, the ADSCs cultured on the paper-stacking membranes in the osteogenic medium exhibited the highest osteogenic-related gene expressions. In vivo, the paper-stacking scaffolds were implanted into the rat calvarial defects (5 mm diameter, one defect per parietal bone) for 12 weeks. Investigating with microcomputer tomography, the ADSC-laden paper-stacking membranes showed the most significant bone reconstruction, and from a morphological perspective, this group occupied 90% of the surface area of the defect, produced the highest bone regeneration volume, and showed the highest bone mineral density of 823.06 mg/cm(3). From hematoxylin and eosin and Masson staining, the new bone tissue was most evident in the ADSC-laden scaffold group. Using quantitative polymerase chain reaction analysis from collected tissues, we found that the ADSC-laden paper-stacking membrane group presented the highest osteogenic-related gene expressions of osteocalcin, osteopontin, osteoprotegerin, bone sialoprotein, runt-related transcription factor 2, and osterix (two to three times higher than the control group, and 1.5 times higher than the paper-stacking membrane group in all the genes). It is proposed that ADSC-laden layer-by-layer paper-stacking scaffolds could be used as a way of promoting bone defect treatment.

Stem cell technology for bone regeneration: current status and potential applications

Continued improvements in the understanding and application of mesenchymal stem cells (MSC) have revolutionized tissue engineering. This is particularly true within the field of skeletal regenerative medicine. However, much remains unknown regarding the native origins of MSC, the relative advantages of different MSC populations for bone regeneration, and even the biologic safety of such unpurified, grossly characterized cells. This review will first summarize the initial discovery of MSC, as well as the current and future applications of MSC in bone tissue engineering. Next, the relative advantages and disadvantages of MSC isolated from distinct tissue origins are debated, including the MSC from adipose, bone marrow, and dental pulp, among others. The perivascular origin of MSC is next discussed. Finally, we briefly comment on pluripotent stem cell populations and their possible application in bone tissue engineering. While continually expanding, the field of MSC-based bone tissue engineering and regeneration shows potential to become a clinical reality in the not-so-distant future.

The canine epiphyseal-derived mesenchymal stem cells are comparable to bone marrow derived-mesenchymal stem cells

Mesenchymal stem cells (MSCs) hold great potential in cell therapy and have attracted increasing interests in a wide range of biomedical sciences. However, the scarcity of MSCs and the prolonged isolation procedure limited the clinical application. To address these 2 issues, we developed a method to isolate MSCs from bone biopsy tissues of euthanized canine body donors. Compared to the traditional method to isolate MSCs from aspirated bone marrow (BMSCs), the isolation procedure for MSCs from harvested epiphyseal cancellous bone (EMSCs) was less time-consuming. The isolated EMSCs had similar plastic-adherence, tri-lineage differentiation and consistent surface marker profiles compared to BMSCs. We harvested BMSCs and EMSCs from 24 euthanized cases from clinics and 42 euthanized donors from a local shelter. The successful rate for EMSC isolation is significantly higher compared to BMSC isolation, while the other properties of the isolated MSCs including the clonogenicity, proliferative potentials and molecular phenotypes were not discernibly different between the MSCs established by the two methods. In conclusion, we demonstrated a new procedure to harvest MSCs by bone biopsy at the epiphyseal region. This method is less time consuming and more reliable, and the resulting MSCs are comparable to those harvested by bone marrow aspiration. The combination of the two methods can greatly improve the efficiency to harvest MSCs.