Adipose Tissue Engineering Research Articles

Adipose Tissue Engineering in Three-Dimensional Levitation Tissue Culture System Based on Magnetic Nanoparticles

White adipose tissue (WAT) is becoming widely used in regenerative medicine/cell therapy applications, and its physiological and pathological importance is increasingly appreciated. WAT is a complex organ composed of differentiated adipocytes, stromal mesenchymal progenitors known as adipose stromal cells (ASC), as well as endothelial vascular cells and infiltrating leukocytes. Two-dimensional (2D) culture that has been typically used for studying adipose cells does not adequately recapitulate WAT complexity. Improved methods for reconstruction of functional WAT ex vivo are instrumental for understanding of physiological interactions between the composing cell populations. Here, we used a three-dimensional (3D) levitation tissue culture system based on magnetic nanoparticle assembly to model WAT development and growth in organoids termed adipospheres. We show that 3T3-L1 preadipocytes remain viable in spheroids for a long period of time, while in 2D culture, they lose adherence and die after reaching confluence. Upon adipogenesis induction in 3T3-L1 adipospheres, cells efficiently formed large lipid droplets typical of white adipocytes in vivo, while only smaller lipid droplet formation is achievable in 2D. Adiposphere-based coculture of 3T3-L1 preadipocytes with murine endothelial bEND.3 cells led to a vascular-like network assembly concomitantly with lipogenesis in perivascular cells. Adipocyte-depleted stromal vascular fraction (SVF) of mouse WAT cultured in 3D underwent assembly into organoids with vascular-like structures containing luminal endothelial and perivascular stromal cell layers. Adipospheres made from primary WAT cells displayed robust proliferation and complex hierarchical organization reflected by a matricellular gradient incorporating ASC, endothelial cells, and leukocytes, while ASC quickly outgrew other cell types in adherent culture. Upon adipogenesis induction, adipospheres derived from the SVF displayed more efficient lipid droplet accumulation than 2D cultures. This indicates that 3D intercellular signaling better recapitulates WAT organogenesis. Combined, our studies show that adipospheres are appropriate for WAT modeling ex vivo and provide a new platform for functional screens to identify molecules bioactive toward individual adipose cell populations. This 3D methodology could be adopted for WAT transplantation applications and aid approaches to WAT-based cell therapy.

Simple and longstanding adipose tissue engineering in rabbits

Adipose tissue engineering for breast reconstruction can be performed for patients who have undergone breast surgery. We have previously confirmed adipogenesis in mice implanted with type I collagen sponge with controlled release of fibroblast growth factor 2 (FGF2) and human adipose tissue-derived stem cells. However, in order to use this approach to treat breast cancer patients, a large amount of adipose tissue is needed, and FGF2 is not readily available. Thus, we aimed to regenerate large amounts of adipose tissue without FGF2 for a long period. Under general anesthesia, cages made of polypropylene mesh were implanted into the rabbits' bilateral fat pads. Each cage was 10 mm in radius and 10 mm in height. Minced type I collagen sponge was injected as a scaffold into the cage. Regenerated tissue in the cage was examined with ultrasonography, and the cages were harvested 3, 6, and 12 months after the implantation. Ultrasonography revealed a gradually increasing homogeneous high-echo area in the cage. Histology of the specimen was assessed with hematoxylin and eosin staining. The percentages of regenerated adipose tissue area were 76.2 ± 13.0 and 92.8 ± 6.6 % at 6 and 12 months after the implantation, respectively. Our results showed de novo adipogenesis 12 months after the implantation of only type I collagen sponge inside the space. Ultrasonography is a noninvasive and useful method of assessing the growth of the tissue inside the cage. This simple method could be a promising clinical modality in breast reconstruction.

Covalently crosslinked chitosan-poly(ethylene glycol) hybrid hydrogels to deliver insulin for adipose-derived stem cells encapsulation

Biodegradable hydrogels carrying adipose-derived stem cells (ASCs) have been highlighted with promising potential regarding adipose tissue engineering. In this study, covalently crosslinked natural/synthetic hybrid hydrogels were prepared from methacrylated water soluble chitosan (N-succinyl-chitosan, SCS) and poly(ethylene glycol) (PEG) by photoinitiaing polymerization under the existence of Irgacure 2959 and the irradiation of UV light. The effect of the incorporated PEG on the in vitro morphologies, equilibrium swelling, weight loss and compressive modulus of SCS/PEG hybrid hydrogels in phosphate buffered saline (PBS) at 37 °C were studied. In order to evaluate the ability of hydrogels to effectively deliver the adipogenic factor, insulin was entrapped within hydrogels by copolymerizing methacrylated SCS/PEG. The insulin would be released from the hydrogels into the local microenvironment via the controlled weight ratio of SCS/PEG. Results demonstrated that the hybrid hydrogel with 10 wt% PEG showed a higher efficiency of insulin delivery compared to the control hydrogels. ASCs were seeded into the insulin-loaded SCS/PEG hydrogels in vitro to assess the biological performance and applicability of hydrogels as cell carriers. These characteristics provide potential opportunities for the hybrid SCS/PEG hydrogels as injectable scaffolds in soft tissue engineering applications. Open image in new window

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

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

Comparing Scaffold-Free and Fibrin-Based Adipose-Derived Stromal Cell Constructs for Adipose Tissue Engineering: An In Vitro and in Vivo Study

Success of adipose tissue engineering for soft tissue repair has been limited by insufficient adipogenic differentiation, an unfavorable host response, and insufficient vascularization. In this study, we examined how scaffold-free spheroid and fibrin-based environments impact these parameters in human adipose-derived stromal cell (ASC)-based adipose constructs. ASCs were differentiated in spheroids or fibrin-based constructs. After 7 days, conditioned medium was collected and spheroids/fibrin-based constructs were either harvested or implanted subcutaneously in athymic mice. Following 7 days of implantation, the number of blood vessels in fibrin-based constructs was significantly higher than in spheroids (93±45 vs. 23±11 vessels/mm(2)), and the inflammatory response to fibrin-based constructs was less severe. The reasons for these results were investigated further in vitro. We found that ASCs in fibrin-based constructs secreted significantly higher levels of the angiogenic factors VEGF and HGF and lower levels of the inflammatory cytokine IL-8. Furthermore, ASCs in fibrin-based constructs secreted significantly higher levels of leptin and showed a 2.5-fold upregulation of the adipogenic transcription factor PPARG and a fourfold to fivefold upregulation of the adipocyte-specific markers FABP4, perilipin, and leptin. These results indicate that fibrin-based ASC constructs are potentially more suitable for ASC-based adipose tissue reconstruction than scaffold-free spheroids.

Human Adipose-Derived Stem Cells Enhance the Angiogenic Potential of Endothelial Progenitor Cells, But Not of Human Umbilical Vein Endothelial Cells

One of the current challenges in the field of adipose tissue engineering is to promote sufficient vascularization to prevent cell death and to support adipose tissue formation. Thus, a novel strategy to enhance neovascularization of tissue-engineered adipose tissue might be the coimplantation of adipose-derived stem cells (ASCs) with endothelial progenitor cells (EPCs). However, no knowledge is given about the cellular interaction in vitro of human ASCs derived from subcutaneous fat tissue and EPCs derived from human peripheral blood. In this study, the first aim was to characterize ASCs and EPCs. Secondly, the two-dimensional Matrigel assay and the three-dimensional spheroid sprouting assay were applied for analyzing the ASC-EPC interaction in regard to formation of capillary-like structures by EPCs by ASC-conditioned medium (CM) or coculture of both cell types and compared to cocultures of ASCs and human umbilical vein endothelial cells (HUVECs). ASC-CM had no influence on the formation of capillary-like structures by EPCs. However, coculture with ASCs significantly enhanced the formation of capillary-like structures by EPCs; an effect that was not observed in cocultures of ASCs with HUVECs. Importantly, this increase in capillary-like structure formation by EPCs due to cell-cell contact was associated with significantly increased vascular endothelial growth factor (VEGF) secretion and VEGF-A mRNA expression, while inhibition of VEGF receptor tyrosine kinases completely abolished this effect. In conclusion, these data suggest that cellular communication occurs between ASCs and EPCs triggered by cell-cell contact or at least close proximity, which is partially mediated by secreted VEGF leading to the enhancement of angiogenic properties in EPCs, but not in HUVECs.

Adipogenic differentiation of scaffold-bound human adipose tissue-derived stem cells (hASC) for soft tissue engineering

Adipose tissue engineering, instead of tissue substitution, often uses autologous adipose tissue-derived stem cells (hASC). These cells are known to improve graft integration and to support neovascularization of scaffolds when seeded onto biomaterials. In this study we thought to engineer adipose tissue using scaffold-bound hASC, since they can be differentiated into the adipocyte cell lineage and used for soft tissue regeneration. We show here by microscopy and gene expression of the peroxysome proliferator-activated receptor gene (PPARγ2) that hASC growing on polypropylene fibrous scaffolds as well as on three-dimensional nonwoven scaffolds can be turned into adipose tissue within 19 days. Freshly isolated hASC displayed a higher differentiation potential than hASC cultured for eight passages. In addition, we proved a modified alginate microcapsule to directly induce adipogenic differentiation of incorporated hASC. The results may help to improve long-term success of adipose tissue regeneration, especially for large-scale soft tissue defects, and support the development of cell–scaffold combinations which can be shaped individually and directly induce the adipogenic differentiation of incorporated hASC at the site of implantation.

The nitric oxide system - cure for shortcomings in adipose tissue engineering?

Adipose tissue engineering aims to grow fat tissue for soft tissue reconstruction after tumour resection or trauma. However, insufficient progenitor cell differentiation and poor vascularization compromise the generation of clinically applicable adipose tissue. The desired process of neo-adipogenesis seems to be difficult to mimic, even though it takes place in all of us, inevitably and rapidly, as soon as we start consuming high-caloric diets. It has previously been proposed that inflammation and its key regulator, nitric oxide (NO), may play a relevant part in neo-adipogenesis. We here discuss how a controlled activation of the nitric oxide system on various levels may represent a cure for several current shortcomings in adipose tissue engineering.

Reconstruction of epidural fat with engineered adipose tissue from adipose derived stem cells and PLGA in the rabbit dorsal laminectomy model

Epidural fibrosis resulted from epidural fat destruction following laminectomy operation is regarded as a main cause of failed back surgery syndrome, which represents one of the most common complications in spine surgery. Up to now, the effectiveness of currently available treatments to prevent such a syndrome is quite limited. In the present study, we aimed to restore epidural fat using adipose tissue engineered from adipose derived stem cells (ASCs) in a rabbit dorsal laminectomy model. ASCs isolated from subcutaneous fat were first expanded to passage 3, seeded on porous poly(lactic-co-glycolic acid, PLGA) scaffold and then adipogenically induced for 7 days in vitro to form cell–scaffold complex. Laminectomy sites were created at T13–L1 level in each animal. The laminectomy defect was implanted either with cell–scaffold complex or PLGA scaffold alone. Non-treated defect was also included as a control. The animals were subjected to MRI evaluation at 1, 12 and 24 weeks post-surgery, and sacrificed at 24 weeks for gross and histological observation. It was demonstrated by MRI evaluation that scar tissue of coarse and high density was formed within laminectomy site in PLGA alone and non-treated groups as early as 12 weeks. However, the defect implanted with engineered adipose had formed a continuous linear adipose tissue regenerated along the spinal cord at 24 weeks. Histologically, a distinct area of adipose tissue just overlaying the dura mater could be identified in cell–scaffold complex treated group at 24 weeks post-operation. Regeneration of epidural fat was further confirmed by positive Oil Red O staining. As to the defect treated with PLGA alone or left untreated, either fine or dense scar tissue adhering to the dura mater was observed. Moreover, we could track the implanted ASCs labeled by magnetic nanoparticles within epidural area for as long as four weeks by MRI detection. Thus, adipose tissue engineered from ASCs exhibited great potential in restoration of epidural fat to prevent formation of epidural fibrosis.

Cotransplantation of Adipose-Derived Mesenchymal Stromal Cells and Endothelial Cells in a Modular Construct Drives Vascularization in SCID/bg Mice

A modular approach to adipose tissue engineering was explored by embedding adipose-derived mesenchymal stromal cells (adMSC) in sub-mm-sized collagen rods or "modules" and coating with human microvascular endothelial cells (HMEC). After subcutaneous injection into a SCID/Bg mouse, HMEC on modules containing embedded adMSC appeared to detach from the modules to form vessels as early as day 3, as confirmed by the human EC-specific UEA-1 lectin stain, and these vessels persisted for up to 90 days. Vessel numbers decreased over 14 days, but vessel size increased suggesting a maturing of the vasculature. Vessel perfusion with the host was confirmed at 21 days by microCT. HMEC on modules without embedded adMSC remained attached to the module surface at day 3 and UEA-1 staining disappeared over 14 days suggesting cell death. It appeared that cotransplantation with adMSC had an anti-apoptotic and proangiogenic effect on HMEC. The early revascularization strategy may be successful in supporting adMSC viability and differentiation, as a preliminary study suggests progressive fat accumulation in the HMEC+adMSC implants: ∼60% of the implant area stained positive for Oil Red O by day 90. adMSC-embedded modules without HMEC surface coating did not show similar levels of Oil Red O staining. All implant volumes decreased over the time course of the experiment, yet HMEC+adMSC module implants were larger than adMSC-only implants at day 90. Collagen gel is mechanically weak and contracts in vivo making it unsuitable as a biomaterial for adipose tissue engineering where volume maintenance is critical. When combined with an appropriate biomaterial, the modular approach to adipose tissue engineering may represent a successful strategy to engineer soft tissue substitutes of clinical relevance.

Layer-shaped alginate hydrogels enhance the biological performance of human adipose-derived stem cells.

BackgroundThe reconstruction of adipose tissue defects is often challenged by the complications that may occur following plastic and reconstructive surgery, including donor-site morbidity, implant migration and foreign body reaction. To overcome these problems, adipose tissue engineering (ATE) using stem cell-based regeneration strategies has been widely explored in the last years. Mounting evidence has shown that adipose-derived stem cells (ADSCs) represent a promising cell source for ATE. In the context of a small number of reports concerning adipose tissue regeneration using three-dimensional (3-D) systems, the present study was designed to evaluate the biological performance of a novel alginate matrix that incorporates human ADSCs (hADSCs).ResultsCulture-expanded cells isolated from the stromal vascular fraction (SVF), corresponding to the third passage which showed the expression of mesenchymal stem cell (MSC) markers, were used in the 3-D culture systems. The latter represented a calcium alginate hydrogel, obtained by the diffusion of calcium gluconate (CGH matrix), and shaped as discoid-thin layer. For comparative purposes, a similar hADSC-laden alginate hydrogel cross-linked with calcium chloride was considered as reference hydrogel (RH matrix). Both hydrogels showed a porous structure under scanning electron microscopy (SEM) and the hADSCs embedded displayed normal spherical morphologies, some of them showing signs of mitosis. More than 85% of the entrapped cells survived throughout the incubation period of 7 days. The percentage of viable cells was significantly higher within CGH matrix at 2 days post-seeding, and approximately similar within both hydrogels after 7 days of culture. Moreover, both alginate-based hydrogels stimulated cell proliferation. The number of hADSC within hydrogels has increased during the incubation period of 7 days and was higher in the case of CGH matrix. Cells grown under adipogenic conditions for 21 days showed that both analyzed 3-D culture systems support adipogenic differentiation in terms of neutral lipid accumulation and perillipin expression. Furthermore, the cells encapsulated in CGH matrix displayed a more differentiated phenotype.ConclusionsThe results of this study suggest that both CGH and RH matrices successfully support the survival and adipogenesis of hADSC. An enhancement of biological performance was detected in the case of CGH matrix, suggesting its promising application in ATE.

A novel strategy for creating a large amount of engineered fat tissue with an axial vascular pedicle and a prefabricated scaffold

In plastic and reconstructive surgery, there is a tremendous clinical need for adequate implants are needed to restore soft-tissue defects resulting from tumor resection, traumatic injury, or congenital anomalies. Restoring the aesthetic function of the soft tissue is as important as restoring the natural tissue function. To address aesthetic issues, injection of hyaluronic acid and collagen and use of artificially synthesized biomaterials and autologous fat tissue grafts is extensive in the clinic, still faces limitations. Achieving minimal morbidity while compensating contour irregularities remains a major challenge because the available reconstruction methods and unsatisfactory biomaterials. Adipose tissue engineering holds great promise for reconstruction, but so far, there was no reports of large-volume engineered adipose tissue. Construction of a large volume of vascularized engineered fat tissue may overcome clinical challenges because vascularization is essential for the survival of engineered fat tissue and its integration with the host tissue. An arteriovenous bundle model for soft tissue has been used in prefabricating a large volume fat tissue with axial vascularization in vivo. Therefore, we hypothesized that combining adipose tissue-derived stem cells (ASCs), and prefabricated vascularized collagen scaffolds, with perforated chamber and arteriovenous bundle, could generate a large volume of engineered fat tissue with an axial vascular pedicle in vivo. Like vascularized autologous tissue, the new constructs could be transferred to the defective site by local transference or microsurgical techniques. The novel strategy could provide a large volume of engineered fat tissue suitable for clinical application and new therapeutic strategies for reconstructing defects if the hypothesis proved to be practical.

Experimental study on adipose tissue engineering with human adipose-derived stem cells and adipose tissue extracellular matrix scaffold

Objective To explore the possibility of building tissue-engineered adipose tissue with human adipose-derived stem cells (ADSCs) and adipose tissue extracellular matrix (ECM) scaffold,and provide experimental basis for clinical application of tissue-engineered adipose tissue for the repair of soft tissue defects.Methods ADSCs were isolated from adipose tissue by liposuction with the method of enzymatic digestion.The cells were induced for three-line differentiation and marked with DiI.Human ECM was extracted from adipose tissue obtained by liposuction.The ECM was freeze-dried,sterilized and crushed to powders.The surface characteristics of ECM were observed under the electron microscopy in vitro.The ADSCs were adhered to ECM powers,and the feasibility of ECM powers as scaffold was explorted.Human ADSCs in a density of 2 × 109/L were collected,and mixed them with ECM powers.They were transplanted subcutaneously into nude mice,and the opposite side of the same mice transplanted with scaffold only served as control group.There were 6 mice in total,and each side was transplanted by 0.5 ml.At 8th week post-transplantation,the mice were sacrificed and the implanted tissue were taken to record the wet weight,The hematoxylin and eosin (HE) sections and red oil O staining were detected.Two-sample test of SPSS 13.0 was used for statistical comparison between wet-determination.Results The ADSCs and human ECM powder were obtained successfully from adipose tissue.The ADSCs could differentiate into adipose cells,bone cells and chondrocytes.Scanning election microscopy (SEM) images showed that the powers had porous structure to which ADSCs could adhere easily,with the adhesion rate being (89.87 ±2.59)％.Eight weeks after transplantation,both experimental and control groups formed new tissues.There were significant differences between two groups ( P ＜ 0.05 ) in the wet weight.HE and red oil O staining confirmed that the experimental group could form mature adipose tissue.Conclusion ADSCs and human ECM scaffold could form tissue-engineered adipose tissuein vivo.It can be used as an ideal method to construct tissue-engineered adipose tissue. Key words: Adipose-derived stem cells; Extracellular matrix; Scaffold; Tissue engineering

Secreted factors from adipose tissue increase adipogenic differentiation of mesenchymal stem cells

Adipose tissue engineering is one of the hottest topics in the field of regenerative medicine. Fat tissue has been considered as an abundant and accessible source of adult stem cells by tissue engineers, since it gives rise to adipose stem cells. However, recent reports have pointed out that adipose tissue, as a secretory and endocrine organ, might secrete cytokines that regulate body functions such as metabolism, infammation and more. In this study, we aim to investigate the adipogenic-inducing factors secreted by fat tissue. Conditioned medium were collected by culturing fat tissue fragments in plastic flasks. Mesenchymal stem cells (MSCs) cultured in conditioned medium (CM) to test the adipogenic-inducing factors. Oil red O staining, reverse transcription/polymerase chain reaction and immunocytofluorescent staining were performed to examine the differentiation of MSCs in CM. MSCs cultured in CM of adipose tissue spontaneously differentiated into adipocytes. Furthermore, supplementation of insulin or dexamethasone to CM accelerated the process of lipid accumulation of differentiated MSCs. Results from this study demonstrated that fat tissues secrete small molecules, which induce adipogenic differentiation of MSCs. Our study provides clues for improving adipose tissue engineering by using fragmented adipose tissue as sources of fat-inducing factors.

Alginate and alginate/gelatin microspheres for human adipose-derived stem cell encapsulation and differentiation

Human adipose-derived stem cells (hADSC) encapsulated in alginate and alginate/gelatin microspheres with adjustable properties were fabricated via an improved microsphere generating device. The mechanism of the device, porous property, swelling behavior of the microspheres and hADSC proliferation as well as adipogenic differentiation were studied extensively. Microspheres with high-ratio evenly distributed adipocytes could be obtained by utilizing the proper matrix material and manufacturing parameters. The adipocyte/hADSC microspheres were a sound in vitro mimicking of a natural fat lobule and therefore a good candidate for adipose tissue engineering and regenerative medicine.

Adipose tissue engineering using adipose-derived stem cells enclosed within an injectable carboxymethylcellulose-based hydrogel

In situ gelation of an aqueous solution of carboxymethylcellulose derivative bearing phenolic hydroxyl groups (CMC-Ph) that contained suspended adipose-derived stem cells (ASCs) was studied in vitro and in vivo for evaluating feasibility in adipose tissue-engineering strategies. The rat ASCs that were enclosed in the CMC-Ph gels through a horseradish peroxidase-catalysed reaction showed 92.8% viability, good proliferation and adipogenic differentiation in vitro. Ten weeks after the subcutaneous injection of ASCs-suspending CMC-Ph for in situ gelation, clearly visible new vascularized adipose tissue formed at the injection site. The number of blood vessels and the area occupied by adipose tissues were five and eight times larger, respectively, than those found in the implanted acellular gel. The adipogenesis and neovascularization were further enhanced by incorporation of fibroblast growth factor into the CMC-Ph gel containing ASCs.

Regenerative Therapieansätze im Bereich der Mammachirurgie

Besides the established techniques of pediculed and free tissue transplantations for breast reconstruction, adipose tissue engineering and structural fat grafting are being applied as options for regenerative therapy. While the initial euphoria about the foreseeable realisation of cell-matrix entities of sufficient size, functionality and long-term volume stability for use in humans has diminished somewhat, fat grafting as experienced a renaissance in recent years. One of the decisive factors for the engraftment of the tissue graft generated though tissue engineering is the formation of an adequate vascular network. Improvements of the matrix, which ideally should mimic natural tissue, such as the use of adipose-derived stem cells (ASCs) that can contribute both to adipogenesis and neoangiogenesis represent promising new approaches. In autologous fat grafting, the mixing of adipocytes and cells of the stromal-vascular fraction (SVF) in order to generate the principle of an inductive microenvironment has already been applied successfully in clinical routine. On the basis of the experimental data that demonstrate an interaction of the adipocytes, ASCs and other progenitor cells with breast cancer cells and the insufficient clinical data regarding oncological safety, this procedure should only be used critically. A concluding evaluation will only be possible after long-term clinical studies have provided good results.

Injectable in situ forming glucose‐responsive dextran‐based hydrogels to deliver adipogenic factor for adipose tissue engineering

AbstractAn injectable and glucose‐responsive hydrogel derived from dextran derivatives and lectin concanavalin A (ConA) was synthesized to deliver adipogenic factor for adipose tissue engineering. The gelation is attributed to the Schiff‐base reaction cross‐linking between aldehydic and aminated dextran. To enhance adipogenesis, the adipogenic factor of insulin was incorporated in the ConA immobilized hydrogels. The gelation time, compressive modulus, morphologies, weight loss, and swelling properties of the hydrogels were investigated. The ConA triggered a competitive displacement of dextran by glucose from the lectin receptor sites, and results in increasing swelling of the gel network. The swelling ratio (SR) of ConA immobilized hydrogel showed glucose dependent properties and linearly increased from 19.8 to 31.3 at 37°C in PBS at glucose concentrations between 0 and 1.0% (w/v). The in vitro release experiments showed that the insulin would be released from this dextran hydrogel into the local microenvironment in response to glucose, thus highlighting the potential of such a injectable and biodegradable hydrogel to be used as part of implantable scaffold to delivery adipogenic factor for adipose tissue engineering. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Injectable biomaterials for adipose tissue engineering

Adipose tissue engineering has recently gained significant attention from materials scientists as a result of the exponential growth of soft tissue filler procedures being performed within the clinic. While several injectable materials are currently being marketed for filling subcutaneous voids, they often face limited longevity due to rapid resorption. Their inability to encourage natural adipose formation or ingrowth necessitates repeated injections for a prolonged effect and thus classifies them as temporary fillers. As a result, a significant need for injectable materials that not only act as fillers but also promote in vivo adipogenesis is beginning to be realized. This paper will discuss the advantages and disadvantages of commercially available soft tissue fillers. It will then summarize the current state of research using injectable synthetic materials, biopolymers and extracellular matrix-derived materials for adipose tissue engineering. Furthermore, the successful attributes observed across each of these materials will be outlined along with a discussion of the current difficulties and future directions for adipose tissue engineering.

The performance of decellularized adipose tissue microcarriers as an inductive substrate for human adipose-derived stem cells

With the aim of developing a clinically-translatable cell expansion and delivery vehicle for adipose tissue engineering, the adipogenic differentiation of human adipose-derived stem cells (ASCs) was investigated on microcarriers fabricated from human decellularized adipose tissue (DAT). ASCs seeded on the DAT microcarriers and cultured in adipogenic differentiation medium within a low-shear spinner culture system demonstrated high levels of adipogenic differentiation, as measured by the expression of adipogenic genes, glycerol-3-phosphate dehydrogenase (GPDH) enzyme activity, and intracellular lipid accumulation. In contrast, gelatin microcarrier controls did not demonstrate significant adipogenesis, emphasizing the role of the native matrix in mediating ASC differentiation. Interestingly, ASCs cultured on the DAT microcarriers in proliferation medium expressed elevated levels of the adipogenic markers, suggesting that the DAT provided an adipo-inductive substrate for the human ASCs. In vivo testing of the DAT and gelatin microcarriers in a subcutaneous Wistar rat model confirmed injectability and demonstrated stable volume retention over 28 days. Under histological analysis, the DAT microcarriers demonstrated no evidence of immunogenicity or cytotoxicity, with the DAT supporting cellular infiltration and tissue remodeling. Pre-seeding the DAT microcarriers with allogenic rat ASCs enhanced cellularity and angiogenesis within the implant region.