Novel maxillary reconstruction with ectopic bone formation by GMP adipose stem cells

Adipose stem cells for bone tissue repair

Adipose-derived stem/stromal cells (ASCs), together with adipocytes, vascular endothelial cells, and vascular smooth muscle cells, are contained in fat tissue. ASCs, like the human bone marrow stromal/stem cells (BMSCs), can differentiate into several lineages (adipose cells, fibroblast, chondrocytes, osteoblasts, neuronal cells, endothelial cells, myocytes, and cardiomyocytes). They have also been shown to be immunoprivileged, and genetically stable in long-term cultures. Nevertheless, unlike the BMSCs, ASCs can be easily harvested in large amounts with minimal invasive procedures. The combination of these properties suggests that these cells may be a useful tool in tissue engineering and regenerative medicine.

Off-label use of adipose-derived stem cells

Background

Adipose-derived stem cells (ASCs) have a broad range of clinical applications. The ease of cell harvest and high yield with minimal donor-site morbidity makes adipose tissue an ideal source of stem cells. Further, the multi-lineage potential of these cells present significant opportunities within the field of tissue engineering, with studies successfully demonstrating their ability to produce a range of tissue types.

Materials and methods

Literature review of publications on the use of ASCs, in the context of current European and US regulations.

Results

According to European and US regulations, many clinical trials reported in literature to date could be considered off-label.

Conclusion

In Europe, clinical trials involving cultured ASCs and/or the use of collagenase, which causes changes in the structural and functional properties of stem cells, and/or ASCs application in non-homologous tissue, should be considered off-label. ASCs should be non-cultured, isolated mechanically, and used only in the subcutaneous tissue.

•

Adipose-derived stem cells hold enormous potential in different fields of regenerative medicine and stem cell therapy.

•

According to European and US regulations, many clinical trials reported in literature could be considered off-label.

•

In Europe, ASCs should be non-cultured, isolated mechanically, and used only in the subcutaneous tissue.

Adipose Tissue as a Strategic Source of Mesenchymal Stem Cells in Bone Regeneration: A Topical Review on the Most Promising Craniomaxillofacial Applications

Bone regeneration in craniomaxillofacial surgery represents an issue that involves both surgical and aesthetic aspects. The most recent studies on bone tissue engineering involving adipose-derived stromal/stem cells (ASCs) have clearly demonstrated that such cells can play a crucial role in the treatment of craniomaxillofacial defects, given their strong commitment towards the osteogenic phenotype. A deeper knowledge of the molecular mechanisms underlying ASCs is crucial for a correct understanding of the potentialities of ASCs-based therapies in the most complex maxillofacial applications. In this topical review, we analyzed the molecular mechanisms of ASCs related to their support toward angiogenesis and osteogenesis, during bone regeneration. Moreover, we analyzed both case reports and clinical trials reporting the most promising clinical applications of ASCs in the treatment of craniomaxillofacial defects. Our study aimed to report the main molecular and clinical features shown by ASCs, used as a therapeutic support in bone engineering, as compared to the use of conventional autologous and allogeneic bone grafts.

Improvement of adipose tissue-derived cells by low-energy extracorporeal shock wave therapy

BACKGROUND

Cell-based therapies with autologous adipose tissue-derived cells have shown great potential in several clinical studies in the last decades. The majority of these studies have been using the stromal vascular fraction (SVF), a heterogeneous mixture of fibroblasts, lymphocytes, monocytes/macrophages, endothelial cells, endothelial progenitor cells, pericytes and adipose-derived stromal/stem cells (ASC) among others. Although possible clinical applications of autologous adipose tissue-derived cells are manifold, they are limited by insufficient uniformity in cell identity and regenerative potency.

METHODS

In our experimental set-up, low-energy extracorporeal shock wave therapy (ESWT) was performed on freshly obtained human adipose tissue and isolated adipose tissue SVF cells aiming to equalize and enhance stem cell properties and functionality.

RESULTS

After ESWT on adipose tissue we could achieve higher cellular adenosine triphosphate (ATP) levels compared with ESWT on the isolated SVF as well as the control. ESWT on adipose tissue resulted in a significantly higher expression of single mesenchymal and vascular marker compared with untreated control. Analysis of SVF protein secretome revealed a significant enhancement in insulin-like growth factor (IGF)-1 and placental growth factor (PLGF) after ESWT on adipose tissue.

DISCUSSION

Summarizing we could show that ESWT on adipose tissue enhanced the cellular ATP content and modified the expression of single mesenchymal and vascular marker, and thus potentially provides a more regenerative cell population. Because the effectiveness of autologous cell therapy is dependent on the therapeutic potency of the patient's cells, this technology might raise the number of patients eligible for autologous cell transplantation.

[Research progress of adipose-derived stem cells in skin wound healing]

Objective

To review the research progress of adipose-derived stem cells (ADSCs) in skin wound healing.

Methods

The recent experiments and clinical studies on the role of ADSCs in skin wound healing were extensively retrieved and analyzed. Additionally, possible mechanisms and novel application strategies were proposed.

Results

As confirmed by in vitro and in vivo experiments and clinical studies, ADSCs promote skin wound healing mainly by two mechanisms: differentiation to target cells that participate in skin wound healing and cytokines paracrine to promote proliferation and migration of various cell lines that are mandatory to promote skin wound healing. Moreover, scaffold materials and cell sheet technology may further add to the potency of ADSCs in promoting skin wound healing.

Conclusion

Remarkable progress has been made in the application of ADSCs in skin wound healing. Further studies are needed to explore the application methods of ADSCs.

A Novel Method of Human Adipose-Derived Stem Cell Isolation with Resultant Increased Cell Yield

BACKGROUND

The authors have developed a novel protocol for isolating adipose-derived stem cells from human lipoaspirate. In this study, they compare their new method to a previously published standard protocol.

METHODS

Human adipose-derived stem cell isolation was performed using two methods to compare cell yield, cell viability, cell proliferation, and regenerative potential. The new and conventional isolation methods differ in two key areas: the collagenase digestion buffer constituents and the use of an orbital shaker. The osteogenic and adipogenic potential of adipose-derived stem cells isolated using both protocols was assessed in vitro, and gene expression analysis was performed. To assess the ability of the isolated cells to generate bone in vivo, the authors created critical-size calvarial defects in mice, which were treated with adipose-derived stem cells loaded onto hydroxyapatite-coated poly(lactic-co-glycolic acid) scaffolds. To test the ability of the isolated cells to enhance adipogenesis, the cells were added to lipoaspirate and placed beneath the scalp of immunocompromised mice. Fat graft volume retention was subsequently assessed by serial computed tomographic volumetric scanning.

RESULTS

The new method resulted in a 10-fold increased yield of adipose-derived stem cells compared with the conventional method. Cells harvested using the new method demonstrated significantly increased cell viability and proliferation in vitro (p < 0.05). New method cells also demonstrated significantly enhanced osteogenic and adipogenic differentiation capacity in vitro (p < 0.05) in comparison with the conventional method cells. Both cell groups demonstrated equivalent osteogenic and adipogenic regenerative potential in mice.

CONCLUSIONS

The authors have developed a protocol that maximizes the yield of adipose-derived stem cells derived from lipoaspirate. The new method cells have increased osteogenic and adipogenic potential in vitro and are not inferior to conventional method cells in terms of their ability to generate bone and fat in vivo.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Cranioplasty with Adipose-Derived Stem Cells, Beta-Tricalcium Phosphate Granules and Supporting Mesh: Six-Year Clinical Follow-Up Results

Several alternative techniques exist to reconstruct skull defects. The complication rate of the cranioplasty procedure is high and the search for optimal materials and techniques continues. To report long-term results of patients who have received a cranioplasty using autologous adipose-derived stem cells (ASCs) seeded on beta-tricalcium phosphate (betaTCP) granules. Between 10/2008 and 3/2010, five cranioplasties were performed (four females, one male; average age 62.0 years) using ASCs, betaTCP granules and titanium or resorbable meshes. The average defect size was 8.1 × 6.7 cm² . Patients were followed both clinically and radiologically. The initial results were promising, with no serious complications. Nevertheless, in the long-term follow-up, three of the five patients were re-operated due to graft related problems. Two patients showed marked resorption of the graft, which led to revision surgery. One patient developed a late infection (7.3 years post-operative) that required revision surgery and removal of the graft. One patient had a successfully ossified graft, but was re-operated due to recurrence of the meningioma 2.2 years post-operatively. One patient had an uneventful clinical follow-up, and the cosmetic result is satisfactory, even though skull x-rays show hypodensity in the borders of the graft. Albeit no serious adverse events occurred, the 6-year follow-up results of the five cases are unsatisfactory. The clinical results are not superior to results achieved by conventional cranial repair methods. The use of stem cells in combination with betaTCP granules and supporting meshes in cranial defect reconstruction need to be studied further before continuing with clinical trials. Stem Cells Translational Medicine 2017;6:1576-1582.

Cytokine, Chemokine, and Growth Factor Profile Characterization of Undifferentiated and Osteoinduced Human Adipose-Derived Stem Cells

Bone is the second most manipulated tissue after blood. Adipose-derived stem cells (ASCs) may become a convenient source of MSC for bone regenerative protocols. Surprisingly, little is known about the most significant biomolecules these cells produce and release after being osteoinduced. Therefore, the present study aimed at dosing 13 candidates chosen among the most representative cytokines, chemokines, and growth factors within the conditioned media of osteodifferentiated and undifferentiated ASCs. Two acknowledged osteoblastic cell models, that is, MG-63 and SaOs-2 cells, were compared. Notably, IL-6, IL-8, MCP-1, and VEGF were highly produced and detectable in ASCs. In addition, while IL-6 and IL-8 seemed to be significantly induced by the osteogenic medium, no such effect was seen for MCP-1 and VEGF. Overall SaOS-2 had a poor expression profile, which may be consistent with the more differentiated phenotype of SaOs-2 compared to ASCs and MG-63. Instead, in maintaining medium, MG-63 displayed a very rich production of IL-12, MCP-1, IP-10, and VEGF, which were significantly reduced in osteogenic conditions, with the only exception of MCP-1. The high expression of MCP-1 and VEGF, even after the osteogenic commitment, may support the usage of ASCs in bone regenerative protocols by recruiting both osteoblasts and osteoclasts of the host.

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.

Can stem cells enhance bone formation in the human edentulous alveolar ridge? A systematic review and meta-analysis

Several non-biological materials are currently being used to increase the alveolar bone volume to support dental implants. Recently, stem cell therapy has emerged as a promising biological substitute or adjuvant to enhance bone healing. In order to determine if stem cell therapy has enough clinical evidence to bone ridge augmentation in humans, a systematic review and meta-analysis were conducted. Two independent investigators searched the Entrez PubMed, SCOPUS and Web of Science databases for eligible randomized clinical trials that describe stem cell therapies for alveolar bone formation. The included studies were evaluated for risk of bias. A random-effects meta-analysis model was used to evaluate the percentage of bone formation in the selected studies. Heterogeneity was evaluated using the Cochrane Chi ² and I ². Nine eligible trials were included. These studies presented an overall unclear risk of bias. A comparison between the lower heterogeneity studies and the long term observational outcomes showed a slight tendency to enhance bone formation. High heterogeneity between the included studies was observed. The lack of outcome standardization made a wide-ranging comparison difficult. The application of stem cells in oral surgery and implantology appears to be promising although more standardized study designs, increased samples and long-term observations are needed to strength the clinical evidence that stem cell therapy is effective for alveolar bone formation.

Challenges of bone tissue engineering in orthopaedic patients

Bone defects may impede normal biomechanics and the structural stability of bone as an organ. In many cases, the correction of bone defects requires extensive surgical intervention involving the use of bone-grafting techniques and other procedures in which healing is slow, there is a high risk of infection and considerable pain is provoked - with no guarantee of complete correction of the defect. Therefore, the search for surgical alternatives continues to present a major challenge in orthopaedic traumatology. The reamer-irrigator-aspirator (RIA) system, which was devised to avoid the problems that can arise with autograft harvesting from the iliac crest, consists of collecting the product of the femoral canal after reaming. The RIA technique improves osteogenic differentiation of mesenchymal stem cells, compared to bone marrow aspiration or cancellous bone harvesting from the iliac crest using a spoon. Another approach, the Masquelet technique, consists of reconstructing a long bone defect by means of an induced membrane grown onto an acrylic cement rod inserted to fill the defect; in a second surgical step, once the membrane is constituted, the cement rod is removed and cancellous autograft is used to fill the defect. Both in RIA and in the Masquelet technique, osteosynthesis is usually needed. Bone transportation by compression-distraction lengthening principles is commonly implemented for the treatment of large bone loss. However, complications are frequently encountered with these techniques. Among new techniques that have been proposed to address the problem of large bone loss, the application of stem cells in conjunction with tissue engineering techniques is very promising, as is the creation of personalised medicine (or precision medicine), in which molecular profiling technologies are used to tailor the therapeutic strategy, to ensure the right method is applied for the right person at the right time, after determining the predisposition to disease among the general population. All of the above techniques for addressing bone defects are discussed in this paper.

Orthopedic tissue regeneration: cells, scaffolds, and small molecules

Orthopedic tissue regeneration would benefit the aging population or patients with degenerative bone and cartilage diseases, especially osteoporosis and osteoarthritis. Despite progress in surgical and pharmacological interventions, new regenerative approaches are needed to meet the challenge of creating bone and articular cartilage tissues that are not only structurally sound but also functional, primarily to maintain mechanical integrity in their high load-bearing environments. In this review, we discuss new advances made in exploiting the three classes of materials in bone and cartilage regenerative medicine--cells, biomaterial-based scaffolds, and small molecules--and their successes and challenges reported in the clinic. In particular, the focus will be on the development of tissue-engineered bone and cartilage ex vivo by combining stem cells with biomaterials, providing appropriate structural, compositional, and mechanical cues to restore damaged tissue function. In addition, using small molecules to locally promote regeneration will be discussed, with potential approaches that combine bone and cartilage targeted therapeutics for the orthopedic-related disease, especially osteoporosis and osteoarthritis.

Injectable adipose tissue combined with stem cells for soft-tissue augmentation: A pilot study for dental applications

Background/purpose

Bone resorption and soft-tissue defects are the typical physiologic responses after tooth extraction. Various dental ridge augmentation techniques have been applied and lack of the soft tissue is the major factor causing the failure. We propose that the adipose-derived stem cell can be useful in soft-tissue augmentation in dental applications. The objective of this study was to optimize the operation procedures for the isolation of adipose stem cells and tissues. Accelerated clinical protocols for effective transplantation of adipose tissue with high amount of adipose stem cells shall be developed.

Materials and methods

Operation parameters were designed and optimized for the extraction of adipose tissue-derived stromal vascular cells. The optimized accelerated procedure was washing the lipoaspirate samples one time. Collagenase was then added and samples were incubated in a water bath for 30 minutes at 37°C and centrifuged at 1200g for 3 minutes. A mouse animal model was applied to evaluate the soft-tissue-filling effects using the optimized procedure.

Results

The animal model tests demonstrated the filling and regeneration of the soft tissues with significant angiogenesis.

Conclusion

This pilot study demonstrated the feasibility of soft-tissue augmentation applications.

Localization of human adipose-derived stem cells and their effect in repair of diabetic foot ulcers in rats

Background

Diabetic foot ulcer (DFU) is an intractable diabetic complication. Patients suffering from diabetes mellitus (DM) frequently present with infected DFUs. In this study, a wound healing model on diabetic rat foot was established to mimic the pathophysiology of clinical patients who suffer from DFUs. Our study aimed to explore the localization of human adipose-derived stem cells (hADSCs) and the role of these cells in the repair of foot ulcerated tissue in diabetic rats, and thus to estimate the possibilities of adipose-derived stem cells for diabetic wound therapy.

Method

Sprague–Dawley rats were used to establish diabetic models by streptozotocin injection. A full-thickness foot dorsal skin wound was created by a 5 mm skin biopsy punch and a Westcott scissor. These rats were randomly divided into two groups: the hADSC-treated group and the phosphate-buffered saline (PBS) control group. The hADSC or PBS treatment was delivered through the left femoral vein of rats. We evaluated the localization of hADSCs with fluorescence immunohistochemistry and the ulcer area and ulcerative histology were detected dynamically.

Result

The hADSCs had a positive effect on the full-thickness foot dorsal skin wound in diabetic rats with a significantly reduced ulcer area at day 15. More granulation tissue formation, angiogenesis, cellular proliferation, and higher levels of growth factors expression were also detected in wound beds.

Conclusions

Our data suggest that hADSC transplantation has the potential to promote foot wound healing in diabetic rats, and transplantation of exogenous stem cells may be suitable for clinical application in the treatment of DFU.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0412-2) contains supplementary material, which is available to authorized users.

Bone Graft Prefabrication Following the In Vivo Bioreactor Principle

Large bone defect treatment represents a great challenge due to the difficulty of functional and esthetic reconstruction. Tissue-engineered bone grafts created by in vitro manipulation of bioscaffolds, seed cells, and growth factors have been considered potential treatments for bone defect reconstruction. However, a significant gap remains between experimental successes and clinical translation. An emerging strategy for bridging this gap is using the in vivo bioreactor principle and flap prefabrication techniques. This principle focuses on using the body as a bioreactor to cultivate the traditional triad (bioscaffolds, seed cells, and growth factors) and leveraging the body's self-regenerative capacity to regenerate new tissue. Additionally, flap prefabrication techniques allow the regenerated bone grafts to be transferred as prefabricated bone flaps for bone defect reconstruction. Such a strategy has been used successfully for reconstructing critical-sized bone defects in animal models and humans. Here, we highlight this concept and provide some perspective on how to translate current knowledge into clinical practice.

•

The in vivo bioreactor principle and flap prefabrication technique is a promising strategy for bone defect reconstruction.

•

The in vivo bioreactor principle focuses on using the body’s self-regenerative capacity to regenerate new tissue.

•

This strategy has been successfully used to reconstruct critical-sized bone defects in humans.

Stem cell regenerative potential for plastic and reconstructive surgery

Stem cells represent heterogeneous population of undifferentiated cells with unique characteristics of long term self renewal and plasticity. Moreover, they are capable of active migration to diseased tissues, secretion of different bioactive molecules, and they have immunosuppressive potential as well. They occur in all tissues through life and are involved in process of embryogenesis and regeneration. During last decades stem cells attracted significant attention in each field of medicine, including plastic and reconstructive surgery. The main goal of the present review article is to present and discuss the potential of stem cells and to provide information about their safe utilization in chronic wounds and fistulae healing, scar management, breast reconstruction, as well as in bone, tendon and peripheral nerve regeneration.

Composition of elastin like polypeptide-collagen composite scaffold influences in vitro osteogenic activity of human adipose derived stem cells

OBJECTIVE

Collagen-based scaffolds for guided bone regeneration (GBR) are continuously improved to overcome the mechanical weaknesses of collagen. We have previously demonstrated superior mechanical characteristics of the elastin-like polypeptide (ELP) reinforced collagen composites. The objectives of this research were to evaluate the efficacy of ELP-collagen composites to culture human adipose-derived stem cells (hASCs) and allow them to undergo osteogenic differentiation. We hypothesized that hASCs would show a superior osteogenic differentiation in stiffer ELP-collagen composites compared to the neat collagen hydrogels.

METHODS

Composite specimens were made by varying ELP (0-18mg/mL) and collagen (2-6mg/mL) in a 3:1 ratio. Tensile strength, elastic modulus, and toughness were determined by uniaxial tensile testing. hASCs cultured within the composites were characterized by biochemical assays to measure cell viability, protein content, and osteogenic differentiation (alkaline phosphatase activity, osteocalcin, and Alizarin red staining). Scanning electron microscopy and energy dispersive spectroscopy were used for morphological characterization of composites.

RESULTS

All composites were suitable for hASCs culture with viable cells over the 22-day culture period. The ELP-collagen composite with 18mg/mL of ELP and 6mg/mL of collagen had greater tensile strength and elastic modulus combined with higher osteogenic activity in terms of differentiation and subsequent mineralization over a period of 3 weeks compared to other compositions. The extra-cellular matrix deposits composed of calcium and phosphorous were specifically seen in the 18:6mg/mL ELP-collagen composite.

SIGNIFICANCE

The success of the 18:6mg/mL ELP-collagen composite to achieve long-term, 3-dimensional culture and osteogenic differentiation indicates its potential as a GBR scaffold.

Bone Regeneration Using the Freshly Isolated Autologous Stromal Vascular Fraction of Adipose Tissue in Combination With Calcium Phosphate Ceramics

: In patients undergoing maxillary sinus floor elevation (MSFE) for dental implant placement, bone substitutes are currently evaluated as alternatives for autologous bone. However, bone substitutes have only osteoconductive properties and lack osteoinductive potential. Therefore, this phase I study evaluated the potential additive effect on bone regeneration by the addition of freshly isolated, autologous but heterologous stromal vascular fraction (SVF), which is highly enriched with adipose stromal/stem cells when compared with native adipose tissue. From 10 patients, SVF was procured using automatic processing, seeded on either β-tricalcium phosphate (n = 5) or biphasic calcium phosphate carriers (n = 5), and used for MSFE in a one-step surgical procedure. Primary objectives were feasibility and safety. The secondary objective was efficacy, evaluated by using biopsies of the augmented area taken 6 months postoperatively, concomitant with dental implant placement. Biopsies were assessed for bone, graft, and osteoid volumes. No adverse effects were reported during the procedure or follow-up (≥3 years). Bone and osteoid percentages were higher in study biopsies (SVF supplemented) than in control biopsies (ceramic only on contralateral side), in particular in β-tricalcium phosphate-treated patients. Paired analysis on the six bilaterally treated patients revealed markedly higher bone and osteoid volumes using microcomputed tomography or histomorphometric evaluations, demonstrating an additive effect of SVF supplementation, independent of the bone substitute. This study demonstrated for the first time the feasibility, safety, and potential efficacy of SVF seeded on bone substitutes for MSFE, providing the first step toward a novel treatment concept that might offer broad potential for SVF-based regenerative medicine applications.

SIGNIFICANCE

This is the first-in-human study using freshly isolated, autologous adipose stem cell preparations (the stromal vascular fraction [SVF] of adipose tissue) applied in a one-step surgical procedure with calcium phosphate ceramics (CaP) to increase maxillary bone height for dental implantations. All 10 patients received CaP plus SVF on one side, whereas bilaterally treated patients (6 of 10) received CaP only on the opposite side. This allowed intrapatient evaluation of the potential added value of SVF supplementation, assessed in biopsies obtained after 6 months. Feasibility, safety, and potential efficacy of SVF for bone regeneration were demonstrated, showing high potential for this novel concept.

Fabrication and development of artificial osteochondral constructs based on cancellous bone/hydrogel hybrid scaffold

Using tissue engineering techniques, an artificial osteochondral construct was successfully fabricated to treat large osteochondral defects. In this study, porcine cancellous bones and chitosan/gelatin hydrogel scaffolds were used as substitutes to mimic bone and cartilage, respectively. The porosity and distribution of pore size in porcine bone was measured and the degradation ratio and swelling ratio for chitosan/gelatin hydrogel scaffolds was also determined in vitro. Surface morphology was analyzed with the scanning electron microscope (SEM). The physicochemical properties and the composition were tested by using an infrared instrument. A double layer composite scaffold was constructed via seeding adipose-derived stem cells (ADSCs) induced to chondrocytes and osteoblasts, followed by inoculation in cancellous bones and hydrogel scaffolds. Cell proliferation was assessed through Dead/Live staining and cellular activity was analyzed with IpWin5 software. Cell growth, adhesion and formation of extracellular matrix in composite scaffolds blank cancellous bones or hydrogel scaffolds were also analyzed. SEM analysis revealed a super porous internal structure of cancellous bone scaffolds and pore size was measured at an average of 410 ± 59 μm while porosity was recorded at 70.6 ± 1.7 %. In the hydrogel scaffold, the average pore size was measured at 117 ± 21 μm and the porosity and swelling rate were recorded at 83.4 ± 0.8 % and 362.0 ± 2.4 %, respectively. Furthermore, the remaining hydrogel weighed 80.76 ± 1.6 % of the original dry weight after hydration in PBS for 6 weeks. In summary, the cancellous bone and hydrogel composite scaffold is a promising biomaterial which shows an essential physical performance and strength with excellent osteochondral tissue interaction in situ. ADSCs are a suitable cell source for osteochondral composite reconstruction. Moreover, the bi-layered scaffold significantly enhanced cell proliferation compared to the cells seeded on either single scaffold. Therefore, a bi-layered composite scaffold is an appropriate candidate for fabrication of osteochondral tissue.

Mechanoresponsive musculoskeletal tissue differentiation of adipose-derived stem cells

Musculoskeletal tissues are constantly under mechanical strains within their microenvironment. Yet, little is understood about the effect of in vivo mechanical milieu strains on cell development and function. Thus, this review article outlines the in vivo mechanical environment of bone, muscle, cartilage, tendon, and ligaments, and tabulates the mechanical strain and stress in these tissues during physiological condition, vigorous, and moderate activities. This review article further discusses the principles of mechanical loading platforms to create physiologically relevant mechanical milieu in vitro for musculoskeletal tissue regeneration. A special emphasis is placed on adipose-derived stem cells (ADSCs) as an emerging valuable tool for regenerative musculoskeletal tissue engineering, as they are easily isolated, expanded, and able to differentiate into any musculoskeletal tissue. Finally, it highlights the current state-of-the art in ADSCs-guided musculoskeletal tissue regeneration under mechanical loading.

Ultrastructural study of mouse adipose-derived stromal cells induced towards osteogenic direction

We investigated the ultrastructural characteristics of mouse adipose-derived stem/stromal cells (ASCs) induced towards osteogenic lineage. ASCs were isolated from adipose tissue of FVB-Cg-Tg(GFPU)5Nagy/J mice and expanded in monolayer culture. Flow cytometry, histochemical staining, and electron microscopy techniques were used to characterize the ASCs with respect to their ability for osteogenic differentiation capacity. Immunophenotypically, ASCs were characterized by high expression of the CD44 and CD90 markers, while the relative content of cells expressing CD45, CD34 and CD117 markers was <2%. In assays of differentiation, the positive response to osteogenic differentiation factors was observed and characterized by deposition of calcium in the extracellular matrix and alkaline phosphatase production. Electron microscopy analysis revealed that undifferentiated ASCs had a rough endoplasmic reticulum with dilated cisterns and elongated mitochondria. At the end of the osteogenic differentiation, the ASCs transformed from their original fibroblast-like appearance to having a polygonal osteoblast-like morphology. Ultrastructurally, these cells were characterized by large euchromatic nucleus and numerous cytoplasm containing elongated mitochondria, a very prominent rough endoplasmic reticulum, Golgi apparatus and intermediate filament bundles. Extracellular matrix vesicles of variable size similar to the calcification nodules were observed among collagen fibrils. Our data provide the ultrastructural basis for further studies on the cellular mechanisms involved in osteogenic differentiation of mouse adipose-derived stem/stromal cells. Microsc. Res. Tech. 79:557-564, 2016. © 2016 Wiley Periodicals, Inc.

Bone repair with skeletal stem cells: rationale, progress to date and clinical application

Bone marrow (BM) contains stem cells for both hematopoietic and nonhematopoietic lineages. Hematopoietic stem cells enable hematopoiesis to occur in a controlled manner in order to accurately compensate for the loss of short- as well as long-lived mature blood cells. The physiological role of nonhematopoietic BM stem cells, often referred to as multipotential stromal cells or skeletal stem cells (SSCs), is less understood. According to an authoritative current opinion, the main function of SSCs is to give rise to cartilage, bone, marrow fat and hematopoiesis-supportive stroma, in a specific sequence during embryonic and postnatal development. This review outlines recent advances in the understanding of origins and homeostatic functions of SSCs in vivo and highlights current and future SSC-based treatments for skeletal and joint disorders.

Bone healing in rabbit calvarial critical-sized defects filled with stem cells and growth factors combined with granular or solid scaffolds

PURPOSE

In pediatric neurosurgery, decompressive craniectomy and correction of congenital cranial anomalies can result in major cranial defects. Corrective cranioplasty for the repair of these critical-sized defects is not only a cosmetic issue. The limited availability of suitable autogenous bone and the morbidity of donor site harvesting have driven the search for new approaches with biodegradable and bioactive materials. This study aimed to assess the healing of rabbit calvarial critical-sized defects filled with osteogenic material, either with bioactive glass scaffolds or tricalcium phosphate granules in various combinations with adipose stem cells or bone marrow stem cells, BMP-2, BMP-7, or VEGF to enhance osteogenesis.

METHODS

Eighty-two bicortical full thickness critical-sized calvarial defects were operated. Five defects were left empty as negative control defects. The remaining 77 defects were filled with solid bioactive glass scaffolds or tricalcium phosphate granules seeded with adipose or bone marrow derived stem cells in combination with BMP-2, BMP-7, or VEGF. The defects were allowed to heal for 6 weeks before histologic and micro-CT analyses.

RESULTS

Micro-CT examination at the 6-week post-operative time point revealed that defects filled with stem cell-seeded tricalcium phosphate granules resulted in new bone formation of 6.0 %, whereas defects with bioactive glass scaffolds with stem cells showed new bone formation of 0.5 to 1.7 %, depending on the growth factor used.

CONCLUSIONS

This study suggests that tricalcium phosphate granules combined with stem cells have osteogenic potential superior to solid bioactive glass scaffolds with stem cells and growth factors.

Stem cells for reutilization in bone regeneration

Bone is one of the most transplanted tissues. While most bone defects heal spontaneously, critical size defects caused by major trauma/malignant tumor and osteonecrosis of femoral head in young adults pose a great challenge in treatment. While the golden standard in treating bone defects is autologous bone grafting, available bone for grafting is quite limited in an individual. To solve the dilemma, stem cell therapy has been tried as a new modality of treatment in lesions not amenable to autologous bone grafting. While successful results were reported from individual studies, the stem cell therapy is still not an established treatment modality for bone regeneration and needs further assessment. Our focus herein is to introduce stem cell sources that have been investigated so far and review the current status of stem cell reutilization for bone regeneration as well as suggesting future perspectives.

Advances in Adipose-Derived Stem Cells Isolation, Characterization, and Application in Regenerative Tissue Engineering

Obesity is a complex, multifactorial disease that has been extensively researched in recent times. Obesity is characterized by excess deposition of adipose tissue in response to surplus energy. Despite the negative connotations of adipose tissue (AT), it serves as a critical endocrine organ. Adipose tissue is a source of several adipokines and cytokines which have been deemed important for both normal metabolic function and disease formation. The discoveries of metabolically active brown AT in adult humans and adipose tissue derived stem cells (ADSC) have been key findings in the past decade with potential therapeutic implications. ADSCs represent an enticing pool of multipotent adult stem cells because of their noncontroversial nature, relative abundance, ease of isolation, and expandability. A decade and a half since the discovery of ADSCs, the scientific community is still working to uncover their therapeutic potential in a wide range of diseases. In this review, we provide an overview of the recent developments in the field of ADSCs and examine their potential use in transplantation and cell-based therapies for the regeneration of diseased organs and systems. We also hope to provide perspective on how to best utilize this readily available, powerful pool of stem cells in the future.

Serially Transplanted Nonpericytic CD146(-) Adipose Stromal/Stem Cells in Silk Bioscaffolds Regenerate Adipose Tissue In Vivo

Progenitors derived from the stromal vascular fraction (SVF) of white adipose tissue (WAT) possess the ability to form clonal populations and differentiate along multiple lineage pathways. However, the literature continues to vacillate between defining adipocyte progenitors as "stromal" or "stem" cells. Recent studies have demonstrated that a nonpericytic subpopulation of adipose stromal cells, which possess the phenotype, CD45(-) /CD31(-) /CD146(-) /CD34(+) , are mesenchymal, and suggest this may be an endogenous progenitor subpopulation within adipose tissue. We hypothesized that an adipose progenitor could be sorted based on the expression of CD146, CD34, and/or CD29 and when implanted in vivo these cells can persist, proliferate, and regenerate a functional fat pad over serial transplants. SVF cells and culture expanded adipose stromal/stem cells (ASC) ubiquitously expressing the green fluorescent protein transgene (GFP-Tg) were fractionated by flow cytometry. Both freshly isolated SVF and culture expanded ASC were seeded in three-dimensional silk scaffolds, implanted subcutaneously in wild-type hosts, and serially transplanted. Six-week WAT constructs were removed and evaluated for the presence of GFP-Tg adipocytes and stem cells. Flow cytometry, quantitative polymerase chain reaction, and confocal microscopy demonstrated GFP-Tg cell persistence, proliferation, and expansion, respectively. Glycerol secretion and glucose uptake assays revealed GFP-Tg adipose was metabolically functional. Constructs seeded with GFP-Tg SVF cells or GFP-Tg ASC exhibited higher SVF yields from digested tissue, and higher construct weights, compared to nonseeded controls. Constructs derived from CD146(-) CD34(+) -enriched GFP-Tg ASC populations exhibited higher hemoglobin saturation, and higher frequency of GFP-Tg cells than unsorted or CD29(+) GFP-Tg ASC counterparts. These data demonstrated successful serial transplantation of nonpericytic adipose-derived progenitors that can reconstitute adipose tissue as a solid organ. These findings have the potential to provide new insights regarding the stem cell identity of adipose progenitor cells.

Stem Cells for Bone Regeneration: From Cell-Based Therapies to Decellularised Engineered Extracellular Matrices

Currently, autologous bone grafting represents the clinical gold standard in orthopaedic surgery. In certain cases, however, alternative techniques are required. The clinical utility of stem and stromal cells has been demonstrated for the repair and regeneration of craniomaxillofacial and long bone defects although clinical adoption of bone tissue engineering protocols has been very limited. Initial tissue engineering studies focused on the bone marrow as a source of cells for bone regeneration, and while a number of promising results continue to emerge, limitations to this technique have prompted the exploration of alternative cell sources, including adipose and muscle tissue. In this review paper we discuss the advantages and disadvantages of cell sources with a focus on adipose tissue and the bone marrow. Additionally, we highlight the relatively recent paradigm of developmental engineering, which promotes the recapitulation of naturally occurring developmental processes to allow the implant to optimally respond to endogenous cues. Finally we examine efforts to apply lessons from studies into different cell sources and developmental approaches to stimulate bone growth by use of decellularised hypertrophic cartilage templates.

Advances in Adipose-Derived Stem Cells Isolation, Characterization, and Application in Regenerative Tissue Engineering

Obesity is a complex, multifactorial disease that has been extensively researched in recent times. Obesity is characterized by excess deposition of adipose tissue in response to surplus energy. Despite the negative connotations of adipose tissue (AT), it serves as a critical endocrine organ. Adipose tissue is a source of several adipokines and cytokines which have been deemed important for both normal metabolic function and disease formation. The discoveries of metabolically active brown AT in adult humans and adipose tissue derived stem cells (ADSC) have been key findings in the past decade with potential therapeutic implications. ADSCs represent an enticing pool of multipotent adult stem cells because of their noncontroversial nature, relative abundance, ease of isolation, and expandability. A decade and a half since the discovery of ADSCs, the scientific community is still working to uncover their therapeutic potential in a wide range of diseases. In this review, we provide an overview of the recent developments in the field of ADSCs and examine their potential use in transplantation and cell-based therapies for the regeneration of diseased organs and systems. We also hope to provide perspective on how to best utilize this readily available, powerful pool of stem cells in the future.

Intradermal injection of human adipose-derived stem cells accelerates skin wound healing in nude mice

Background

The use of stem cells from adipose tissue or adipose-derived stem cells (ASCs) in regenerative medicine could be an interesting alternative to bone marrow stem cells because they are easily accessible and available in large quantities. The aim of this study was to evaluate the potential effect of ASCs on the healing of 12 mm diameter-excisional wounds (around 110 mm²) in nude mice.

Methods

Thirty nude mice underwent surgery to create one 12-mm excisional wound per mouse (spontaneous healing, n = 6; Cytocare® 532, n = 12; ASCs, n = 12). The Galiano wound model was chosen to avoid shrinkage and thus slow the spontaneous healing (SH) of mouse skin, making it closer to the physiology of human skin healing. Transparent dressings were used to enable daily healing time measurements to be taken. Immunohistochemistry, histological and blood perfusion analysis were carried out on the healed skin.

Results

The in vivo results showed the effectiveness of using ASCs on reducing the time needed for complete healing to 21.2 days for SH, 17.4 days for vehicle alone (Cytocare® 532) and 14.6 days with the addition of ASCs (p < 0.001). Moreover, cutaneous perfusion of the healed wound was significantly improved in ASC-treated mice compared to SH group, as shown by laser Doppler flowmetry and the quantitation of blood vessels using immunohistochemistry of αsmooth muscle actin.

Conclusions

The tolerance and efficacy of cryopreserved ASCs to accelerate the complete closure of the wound by increasing the maturation of the skin and its blood perfusion, shows their therapeutic benefit in the wound healing context.

Three dimensional de novo micro bone marrow and its versatile application in drug screening and regenerative medicine

The finding that bone marrow hosts several types of multipotent stem cell has prompted extensive research aimed at regenerating organs and building models to elucidate the mechanisms of diseases. Conventional research depends on the use of two-dimensional (2D) bone marrow systems, which imposes several obstacles. The development of 3D bone marrow systems with appropriate molecules and materials however, is now showing promising results. In this review, we discuss the advantages of 3D bone marrow systems over 2D systems and then point out various factors that can enhance the 3D systems. The intensive research on 3D bone marrow systems has revealed multiple important clinical applications including disease modeling, drug screening, regenerative medicine, etc. We also discuss some possible future directions in the 3D bone marrow research field.

From bench to bedside: use of human adipose-derived stem cells

Since the discovery of adipose-derived stem cells (ASC) in human adipose tissue nearly 15 years ago, significant advances have been made in progressing this promising cell therapy tool from the laboratory bench to bedside usage. Standardization of nomenclature around the different cell types used is finally being adopted, which facilitates comparison of results between research groups. In vitro studies have assessed the ability of ASC to undergo mesenchymal differentiation as well as differentiation along alternate lineages (transdifferentiation). Recently, focus has shifted to the immune modulatory and paracrine effects of transplanted ASC, with growing interest in the ASC secretome as a source of clinical effect. Bedside use of ASC is advancing alongside basic research. An increasing number of safety-focused Phase I and Phase IIb trials have been published without identifying any significant risks or adverse events in the short term. Phase III trials to assess efficacy are currently underway. In many countries, regulatory frameworks are being developed to monitor their use and assure their safety. As many trials rely on ASC injected at a distant site from the area of clinical need, strategies to improve the homing and efficacy of transplanted cells are also being explored. This review highlights each of these aspects of the bench-to-bedside use of ASC and summarizes their clinical utility across a variety of medical specialties.

Stem Cell Therapy: Current Applications and Potential for Urology

Stem cell therapy holds the potential to revolutionize the treatment of a number of chronic conditions. Stem cells ability to home in on injured sites of the body, stimulate angiogenesis, tissue regeneration, immunomodulation, anti-inflammatory, and anti-fibrotic factors have attracted their use in the treatment of many conditions. Urology has registered one of the highest experimental successes using stem cell therapy. However, the rate of clinical applications is comparatively lower. This review takes a look at our efforts so far and what needs to be done in order to maximize the clinical benefit we can derive from stem cells.

Isolation and differentiation potential of human mesenchymal stem cells from adipose tissue harvested by water jet-assisted liposuction

BACKGROUND

In recent years the therapeutic application of extracted adipose tissue for autologous fat grafting and the application of adipose tissue-derived mesenchymal stem cells (adMSC) isolated thereof has progressed. Water-jet assisted liposuction (WAL) is 1 procedure for harvesting adipose tissue and provides a favorable aesthetic outcome combined with high tissue protection. Tissue aspirated by WAL has been successfully applied in grafting procedures.

OBJECTIVES

The aims of this study were to confirm the tissue viability and to understand the abundance and mesenchymal differentiation capacity of stem cells within the tissue.

METHODS

We analyzed tissue integrity of WAL tissue particles via fluorescence microscopy. The adMSC content was determined by isolating the cells from the tissue. The mesenchymal differentiation capacity was confirmed with cytochemical staining methods.

RESULTS

The stromal vascular fraction of WAL tissue showed high viability and contained an average of 2.6 × 105 CD34-positive cells per milliliter of tissue. Thus WAL tissue contains a high number of stem cells. Furthermore adMSC isolated from WAL tissue showed typical mesenchymal differentiation potential.

CONCLUSIONS

WAL of adipose tissue is well suited for autologous fat grafting because it retains tissue viability. Furthermore it is a valid source for the subsequent isolation of adMSC with multipotent differentiation potential.

LEVEL OF EVIDENCE

3 Therapeutic.

Bone Morphogenetic Protein-2 Induces Donor-Dependent Osteogenic and Adipogenic Differentiation in Human Adipose Stem Cells

Bone morphogenetic protein-2 (BMP-2) is a growth factor used to stimulate bone regeneration in clinical applications. However, there are contradicting reports on the functionality of BMP-2 in human adipose stem cells (hASCs), which are frequently used in tissue engineering. In this study, we analyzed the effects of BMP-2 on SMAD1/5 signaling, proliferation, and differentiation in hASCs. Our results indicated that BMP-2 induced dose-dependent (25-100 ng/ml) activation of SMAD signaling. Furthermore, the cell proliferation analysis revealed that BMP-2 (100 ng/ml) consistently decreased the proliferation in all the cell lines studied. However, the analysis of the differentiation potential revealed that BMP-2 (100 ng/ml) exhibited a donor-dependent dual role, inducing both osteogenic and adipogenic differentiation in hASCs. The quantitative alkaline phosphatase (qALP) activity and mineralization levels were clearly enhanced in particular donor cell lines by BMP-2 stimulus. On the contrary, in other cell lines, qALP and mineralization levels were diminished and the lipid formation was enhanced. The current study also suggests that hASCs have accelerated biochemical responsiveness to BMP-2 stimulus in human serum-supplemented culture medium compared with fetal bovine serum. The production origin of the BMP-2 growth factor is also important for its response: BMP-2 produced in mammalian cells enhanced signaling and differentiation responses compared with BMP-2 produced in Escherichia coli. These results explain the existing contradiction in the reported BMP-2 studies and indicate the variability in the functional end mechanism of BMP-2-stimulated hASCs.

SIGNIFICANCE

This study examined how bone morphogenetic protein-2 (BMP-2) modulates the SMAD signaling mechanism and the proliferation and differentiation outcome of human adipose stem cells (hASCs) derived from several donors. The results indicate that BMP-2 triggers molecular SMAD signaling mechanisms in hASCs and regulates differentiation processes in human serum-culture conditions. Importantly, BMP-2 has dual activity, inducing osteogenic and adipogenic differentiation, subject to hASC donor line studied. These findings explain contradictory previous results and highlight the importance of further studies to understand how signaling pathways guide mesenchymal stem cell functions at the molecular level.

Adipose-derived stem cells: selecting for translational success

We have witnessed a rapid expansion of in vitro characterization and differentiation of adipose-derived stem cells, with increasing translation to both in vivo models and a breadth of clinical specialties. However, an appreciation of the truly heterogeneous nature of this unique stem cell group has identified a need to more accurately delineate subpopulations by any of a host of methods, to include functional properties or surface marker expression. Cells selected for improved proliferative, differentiative, angiogenic or ischemia-resistant properties are but a few attributes that could prove beneficial for targeted treatments or therapies. Optimizing cell culture conditions to permit re-introduction to patients is critical for clinical translation.

The Value of SPECT/CT in Monitoring Prefabricated Tissue-Engineered Bone and Orthotopic rhBMP-2 Implants for Mandibular Reconstruction

Bone tissue engineering shows good prospects for mandibular reconstruction. In recent studies, prefabricated tissue-engineered bone (PTEB) by recombinant human bone morphogenetic proteins (rhBMPs) applied in vivo has found to be an effective alternative for autologous bone grafts. However, the optimal time to transfer PTEB for mandibular reconstruction is still not elucidated. Thus, here in an animal experiment of rhesus monkey, the suitable transferring time for PTEB to reconstruct mandibular defects was evaluated by ^99mTc-MDP SPECT/CT, and its value in monitoring orthotopic rhBMP-2 implants for mandibular reconstruction was also evaluated. The result of SPECT/CT showed higher ^99mTc-MDP uptake, indicating osteoinductivity, in rhBMP-2 incorporated demineralized freeze-dried bone allograft (DFDBA) and coralline hydroxyapatite (CHA) implants than those without BMP stimulation. ^99mTc-MDP uptake of rhBMP-2 implant peaked at 8 weeks following implantation while CT showed the density of these implants increased after 13 weeks’ prefabrication. Histology confirmed that mandibular defects were repaired successfully with PTEB or orthotopically rhBMP-2 incorporated CHA implants, in accordance with SPECT/CT findings. Collectively, data shows ^99mTc-MDP SPECT/CT is a sensitive and noninvasive tool to monitor osteoinductivity and bone regeneration of PTEB and orthotopic implants. The PTEB achieved peak osteoinductivity and bone density at 8 to 13 weeks following ectopic implantation, which would serve as a recommendable time frame for its transfer to mandibular reconstruction.

Axially vascularised mandibular constructs: Is it time for a clinical trial?

Applying regenerative therapies in the field of cranio-maxillofacial reconstruction has now become a daily practice. However, regeneration of challenging or irradiated bone defects following head and neck cancer is still far beyond clinical application. As the key factor for sound regeneration is the development of an adequate vascular supply for the construct, the current modalities using extrinsic vascularization are incapable of regenerating such complex defects. Our group has recently introduced the intrinsic axial vascularization technique to regenerate mandibular defects using the arteriovenous loop (AVL). The technique has shown promising results in terms of efficient vascularization and bone regeneration at the preclinical level. In this article, we have conducted a narrative literature review about using the AVL to vascularize tissue-engineering constructs at the preclinical level. We have also conducted a systematic literature review about applying the technique of axial vascularization in the field of craniofacial regeneration. The versatility of the technique and the possible challenges are discussed, and a suggested protocol for the first clinical trial applying the AVL technique for mandibular reconstruction is also presented.

Chick embryo xenograft model reveals a novel perineural niche for human adipose-derived stromal cells

Human adipose-derived stromal cells (hADSC) are a heterogeneous cell population that contains adult multipotent stem cells. Although it is well established that hADSC have skeletal potential in vivo in adult organisms, in vitro assays suggest further differentiation capacity, such as into glia. Thus, we propose that grafting hADSC into the embryo can provide them with a much more instructive microenvironment, allowing the human cells to adopt diverse fates or niches. Here, hADSC spheroids were grafted into either the presumptive presomitic mesoderm or the first branchial arch (BA1) regions of chick embryos. Cells were identified without previous manipulations via human-specific Alu probes, which allows efficient long-term tracing of heterogeneous primary cultures. When grafted into the trunk, in contrast to previous studies, hADSC were not found in chondrogenic or osteogenic territories up to E8. Surprisingly, 82.5% of the hADSC were associated with HNK1+ tissues, such as peripheral nerves. Human skin fibroblasts showed a smaller tropism for nerves. In line with other studies, hADSC also adopted perivascular locations. When grafted into the presumptive BA1, 74.6% of the cells were in the outflow tract, the final goal of cardiac neural crest cells, and were also associated with peripheral nerves. This is the first study showing that hADSC could adopt a perineural niche in vivo and were able to recognize cues for neural crest cell migration of the host. Therefore, we propose that xenografts of human cells into chick embryos can reveal novel behaviors of heterogeneous cell populations, such as response to migration cues.