Vascularized Adipose Tissue Research Articles

Presence of vasculature results in faster insulin response in adipocytes in vascularized adipose tissue model_suppl

Besides being an energy store, adipose tissue is an endocrine organ closely associated with the vascular system. Human relevant in vitro models are needed to study adipose tissue and related diseases. Vasculature plays a central role in the development and inhibition of adipose tissue-related diseases. Here, an adipocyte culture was established from hASC (human adipose stromal cells), and a vascularized adipose tissue model was established from hASC and HUVEC (human umbilical cord vein endothelial cells) co-culture, utilizing the same differentiation procedure. Comparing these models allowed analysis of the effect of vascularization on adipocytes. Both models were characterized on gene (adipocyte and vasculature-related), protein (von Willebrand factor, collagen IV, CD140b and CD144, secretion of leptin, adiponectin and FABP4), and functional (triglyceride accumulation, glucose uptake, and lipolysis) levels. Additionally, the vascularized adipose tissue model was exposed to chemicals with known effects on adipogenesis and angiogenesis (rosiglitazone, chlorpyrifos, prochloraz, mancozeb, butylparaben, 15-deoxy- Δ12,14-prostaglandin J2, bisphenol A, bis-(2-ethylhexyl) phthalate, tributyltin chloride) to compare their effects to the literature. The in vitro vascularized adipose tissue model demonstrated the presence of functional adipocytes and an extensive vascular network, displaying relevant gene and protein markers. Insulin induced glucose uptake, inhibited lipolysis, and influenced vasculature-related genes. The presence of vasculature led to a faster lipolysis inhibition by insulin and modulated responses to chemicals. This novel, thoroughly characterized, vascularized adipose tissue model is a promising new tool for studying adipose tissue as well as the effects of chemicals on adipogenesis and angiogenesis in adipose tissue.

Silicon-Enhanced Adipogenesis and Angiogenesis for Vascularized Adipose Tissue Engineering.

The enhancement of adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and sufficient vascularization remain great challenges for the successful reconstruction of engineered adipose tissue. Here, the bioactive effects of silicon (Si) ions on adipogenic differentiation of human BMSCs (HBMSCs) and the stimulation of vascularization during adipose tissue regeneration are reported. The results show that Si ions can enhance adipogenic differentiation of HBMSCs through the stimulation of the expression of adipogenic differentiation switches such as peroxisome proliferator‐activated receptor γ and CCAAT/enhancer‐binding protein α. Furthermore, Si ions can enhance both angiogenesis and adipogenesis, and inhibit dedifferentiation of cocultured adipocytes by regulating the interactions between HBMSC‐derived adipocytes and human umbilical vein endothelial cells, in which the promotion of the expression of insulin‐like growth factor 1 and vascular endothelial growth factor plays vital roles. The in vivo studies further demonstrate that the designed composite hydrogel with the ability to release bioactive Si ions clearly stimulates neovascularization and adipose tissue regeneration. The study suggests that Si ions released from biomaterials are important chemical cues for adipogenic differentiation and biomaterials with the ability to release Si ions can be designed for adipose tissue engineering.

A cellulose-based material for vascularized adipose tissue engineering.

Artificial adipose tissue (AT) constructs are urgently needed to treat severe wounds, to replace removed tissue, or for the use as in vitro model to screen for potential drugs or study metabolic pathways. The clinical translation of products is mostly prevented by the absence of a vascular component that would allow a sustainable maintenance and an extension of the construct to a relevant size. With this study, we aimed to evaluate the suitability of a novel material based on bacterial cellulose (CBM) on the defined adipogenic differentiation of human adipose-derived stem cells (ASCs) and the maintenance of the received adipocytes (diffASCs) and human microvascular endothelial cells (mvECs) in mono- and coculture. A slight acceleration of adipogenic differentiation over regular tissue culture polystyrene (TCPS) was seen on CBM under defined conditions, whereas on the maintenance of the generated adipocytes, comparable effects were detected for both materials. CBM facilitated the formation of vascular-like structures in monoculture of mvECs, which was not observed on TCPS. By contrast, vascular-like structures were detected in CBM and TCPS in coculture by the presence of diffASCs. Concluding, CBM represents a promising material in vascularized AT engineering with the potential to speed up and simplify the in vitro setup of engineered products. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1431-1439, 2019.

Comparison of covalently and physically cross-linked collagen hydrogels on mediating vascular network formation for engineering adipose tissue

Timely tissue vascularization and integration of engineered tissues into a patient plays an important role in the successful translation of engineered tissues into clinically relevant therapies. To decrease the time needed to vascularize an engineered adipose tissue, suitable local microenvironments provided by hydrogels to support cell-based functional vascular network formation have been investigated. Using the same biomolecule in solution, two types of hydrogels can be obtained: a “physical hydrogel” which is thermal-induced self-assemble fibril initiation and growth, due to amino and carboxyl telopeptides on collagen chains, and a “chemical hydrogel” which results from the covalently cross-linking of the side chains induced by one step enzyme mediation in aqueous solution. In this paper, we compare the capability of engineering vascular network and large-sized vascularized adipose tissue in vivo in different types of collagen hydrogels, physical and chemical crosslinking. The relationships between vascular network formation and hydrogel properties for the two types of hydrogels are discussed. Finally, we successfully engineered a vascularized adipose tissue construct (∼877.6 adipocytes/mm2; 94% area of a construct) in the absence of exogenous cytokines in chemical covalently crosslinking cell-laden hydrogel. These results show manipulating the polymerized methods of a hydrogel could not only modulate vascular network formation, but also regenerate adipose tissue in vivo.

Development of Versatile Human In Vitro Vascularized Adipose Tissue Model with Serum-Free Angiogenesis and Natural Adipogenesis Induction.

Many adipose tissue-related diseases, such as obesity and type 2 diabetes, are worldwide epidemics. For studying these diseases, relevant human cell models are needed. In this study, we developed a vascularized adipose tissue model where human adipose stromal cells and human umbilical cord vein endothelial cells were cocultured with natural adipogenic and defined serum-free angiogenic media for 14days. Several different protocols were compared to each other. The protocols varied in cell numbers and plating sequences. Lipid accumulation was studied with AdipoRed reagent, relative cell number with WST-1 reagent, gene expression of glut4, leptin, aP2, adiponectin, PPARγ and PPARγ2 with RT-qPCR. Secretion of adiponectin, leptin and aP2 was analysed with ELISA. The immunostained vascular network was imaged with Cell-IQ and area quantified using ImageJ. In this study, both angiogenesis and adipogenesis were successfully induced. Protocols produced strong lipid accumulation, good vascular network formation and induced adipocyte-specific protein secretion and expression of studied adipocyte genes. Results showed that cell numbers and cell plating sequences are important factors when aiming at invitro standardized tissue model. Presence of mature vasculature appeared leads to faster the maturation of adipocytes judged by the lipid accumulation and gene expression results. The developed vascularized adipose tissue model is simple to use, easily modifiable to suit various applications and as such, a promising new tool for adipose tissue research when, for example, studying the effect of different cell types on adipose tissue function or for mechanistic studies.

Completely defined co-culture of adipogenic differentiated ASCs and microvascular endothelial cells

Vascularized adipose tissue models are highly demanded as alternative to existing animal models to elucidate the mechanisms of widespread diseases, screen for new drugs or asses corresponding safety levels. Standardly used animal-derived sera therein, are associated to ethical concerns, the risk of contaminations and many uncertainties in their composition and impact on cells. Therefore their use should be completely omitted. In this study we developed a serum-free, defined co-culture medium and implemented it to set up an adipocyte-endothelial cell (EC) co-culture model. Human adipose-derived stem cells were differentiated under defined conditions (diffASCs) and, like human microvascular ECs (mvECs), cultured in a developed defined co-culture medium in mono-, indirect or direct co-culture for 14 days. The developed defined co-culture medium was superior to compared mono-culture media and facilitated the functional maintenance and maturation of diffASCs including perilipin A expression, lipid accumulation and glycerol and leptin release. The medium equally allowed mvEC maintenance, confirmed by the expression of CD31 and vWF and acLDL uptake. Thereby mvECs showed a strong dependency on EC-specific factors. Additionally the development of vascular structures by mvECs was facilitated when directly co-cultured with diffASCs. The completely defined co-culture system allows for the serum-free setup of adipocyte/EC co-cultures and thereby represents a valuable and ethically acceptable tool for the setup of vascularized adipose tissue models.

Native extracellular matrix/fibroin hydrogels for adipose tissue engineering with enhanced vascularization

Adipose tissue engineering is a promising field for regeneration of soft tissue defects. However, vascularization is needed since nutrients and oxygen cannot reach cells in thick implants by diffusion. Obtaining a biocompatible scaffold with good mechanical properties is another problem. In this study, we aimed to develop thick and vascularized adipose tissue constructs supporting cell viability and adipose tissue regeneration. Hydrogels were prepared by mixing rat decellularized adipose tissue (DAT) and silk fibroin (Fib) at different v/v ratios (3:1, 1:1 and 1:3) and vortexing. Gelation times decreased with increasing fibroin ratio Among hydrogel groups 1:3—DAT:Fib ratio group showed similar mechanical properties with adipose tissue. Both pre-adipocytes and pre-endothelial cells, pre-differentiated from adipose derived stem cells (ASCs), were encapsulated in hydrogels at a 1: 3 ratio. In vitro analyses showed that hydrogels with 1:3 (v/v) DAT:Fib ratio supported better cell viability. Pre-adipocytes had lipid vesicles, and pre-endothelial cells formed tubular structures inside hydrogels only after 3 days in vitro. When endothelial and adipogenic pre-differentiated ASCs (for 7 days before encapsulation) were encapsulated together into 1:3—DAT:Fib hydrogels both cell types continued to differentiate into the committed cell lineage. Vascularization process in the hydrogels implanted with adipogenic and endothelial pre-differentiated ASCs took place between the first and second week after implantation which was faster than observed in the empty hydrogels. ASCs pre-differentiated towards adipogenic lineage inside hydrogels had begun to accumulate lipid vesicles after 1 week of subcutaneous implantation Based on these results, we suggest that 1:3—DAT:Fib hydrogels with enhanced vascularization hold promise for adipose tissue engineering.

Functional Human Beige Adipocytes From Induced Pluripotent Stem Cells.

Activation of thermogenic beige adipocytes has recently emerged as a promising therapeutic target in obesity and diabetes. Relevant human models for beige adipocyte differentiation are essential to implement such therapeutic strategies. We report a straightforward and efficient protocol to generate functional human beige adipocytes from human induced pluripotent stem cells (hiPSCs). Without overexpression of exogenous adipogenic genes, our method recapitulates an adipogenic developmental pathway through successive mesodermal and adipogenic progenitor stages. hiPSC-derived adipocytes are insulin sensitive and display beige-specific markers and functional properties, including upregulation of thermogenic genes, increased mitochondrial content, and increased oxygen consumption upon activation with cAMP analogs. Engraftment of hiPSC-derived adipocytes in mice produces well-organized and vascularized adipose tissue, capable of β-adrenergic–responsive glucose uptake. Our model of human beige adipocyte development provides a new and scalable tool for disease modeling and therapeutic screening.

EGF and hydrocortisone as critical factors for the co-culture of adipogenic differentiated ASCs and endothelial cells

In vitro composed vascularized adipose tissue is and will continue to be in great demand e.g. for the treatment of extensive high-graded burns or the replacement of tissue after tumor removal. Up to date, the lack of adequate culture conditions, mainly a culture medium, decelerates further achievements. In our study, we evaluated the influence of epidermal growth factor (EGF) and hydrocortisone (HC), often supplemented in endothelial cell (EC) specific media, on the co-culture of adipogenic differentiated adipose-derived stem cells (ASCs) and microvascular endothelial cells (mvECs). In ASCs, EGF and HC are thought to inhibit adipogenic differentiation and have lipolytic activities. Our results showed that in indirect co-culture for 14 days, adipogenic differentiated ASCs further incorporated lipids and partly gained an univacuolar morphology when kept in media with low levels of EGF and HC. In media with high EGF and HC levels, cells did not incorporate further lipids, on the contrary, cells without lipid droplets appeared. Glycerol release, to measure lipolysis, also increased with elevated amounts of EGF and HC in the culture medium. Adipogenic differentiated ASCs were able to release leptin in all setups. MvECs were functional and expressed the cell specific markers, CD31 and von Willebrand factor (vWF), independent of the EGF and HC content as long as further EC specific factors were present. Taken together, our study demonstrates that adipogenic differentiated ASCs can be successfully co-cultured with mvECs in a culture medium containing low or no amounts of EGF and HC, as long as further endothelial cell and adipocyte specific factors are available.

Strategy for constructing vascularized adipose units in poly(l-glutamic acid) hydrogel porous scaffold through inducing in-situ formation of ASCs spheroids.

Vascularization is of great importance to adipose tissue regeneration. Adipose derived stem cell (ASC) spheroids possessed not only the high efficiency of vascularization, but also the improved differentiation ability. Several research works have illustrated the advantage of ASC spheroids in vascularization. However, in adipose regeneration, ASC spheroid was rarely used. Even so, it is reasonable to believe that ASC spheroids hold a great promise in vascularized adipose tissue engineering. Thus in the present study, we introduced a method to create lots of ASC spheroids that acted as lots of individual adipogenesis and angiogenesis units inside of a porous hydrogel scaffold. Then, the scaffold carrying ASC spheroids was implanted subcutaneously in nude mice to preliminarily evaluate the adipose tissue generation and blood vessel formation.

Influence of epidermal growth factor (EGF) and hydrocortisone on the co-culture of mature adipocytes and endothelial cells for vascularized adipose tissue engineering.

The composition of vascularized adipose tissue is still an ongoing challenge as no culture medium is available to supply adipocytes and endothelial cells appropriately. Endothelial cell medium is typically supplemented with epidermal growth factor (EGF) as well as hydrocortisone (HC). The effect of EGF on adipocytes is discussed controversially. Some studies say it inhibits adipocyte differentiation while others reported of improved adipocyte lipogenesis. HC is known to have lipolytic activities, which might result in mature adipocyte dedifferentiation. In this study, we evaluated the influence of EGF and HC on the co-culture of endothelial cells and mature adipocytes regarding their cell morphology and functionality. We showed in mono-culture that high levels of HC promoted dedifferentiation and proliferation of mature adipocytes, whereas EGF seemed to have no negative influence. Endothelial cells kept their typical cobblestone morphology and showed a proliferation rate comparable to the control independent of EGF and HC concentration. In co-culture, HC promoted dedifferentiation of mature adipocytes, which was shown by a higher glycerol release. EGF had no negative impact on adipocyte morphology. No negative impact on endothelial cell morphology and functionality could be seen with reduced EGF and HC supplementation in co-culture with mature adipocytes. Taken together, our results demonstrate that reduced levels of HC are needed for co-culturing mature adipocytes and endothelial cells. In co-culture, EGF had no influence on mature adipocytes. Therefore, for the composition of vascularized adipose tissue constructs, the media with low levels of HC and high or low levels of EGF can be used.

Induction of adipose-derived stem cells on injectable nanofibrous spongy microspheres for vascularized adipose tissue regeneration in vivo

Event Abstract Back to Event Induction of adipose-derived stem cells on injectable nanofibrous spongy microspheres for vascularized adipose tissue regeneration in vivo Yasmine Doleyres1, Xiaobing Jin2 and Peter X. Ma1, 2, 3, 4 1 University of Michigan, Macromolecular Science and Engineering Program, United States 2 University of Michigan, Department of Biologic and Materials Sciences, United States 3 University of Michigan, Department of Biomedical Engineering, United States 4 University of Michigan, Department of Materials Science and Engineering, United States Soft tissue defects in the craniofacial region or the breast region often occur due to congenital defects, traumatic injury, or cancer occurring in the underlying tissue[1]. Correcting these defects in the case of facial reconstruction can be done by transplanting adipose (fat) tissue from another area of the body into the facial region or in the case of reconstruction following breast cancer can be done through autologous tissue transplantation, if available, or using silicone or saline-filled implants. The problem with these options is that between 20-90% of transplanted fat tissue often resorbs within a couple months after being transplanted due to lack of vascularization and implants often fail because of capsular constriction and become infected, leading to multiple surgeries in both cases[1]-[8]. The most ideal option would be to regenerate one’s own adipose tissue just as it is naturally produced by the body. Lasting tissue regeneration options for in vivo adipose tissue have yet to be developed, and this is the goal of this project. Novel nanofibrous spongy (porous) microspheres (NF-SMS) have been developed and appear to be a suitable scaffolding or cell-carrying material for the differentiation and growth of adipose-derived stem cells (ASCs). These microspheres made of poly-L-lactic acid (PLLA) have a nanofibrous architecture that well-mimics the cells’ natural extracellular matrix and also allows for cells to pack the interior of the microspheres[9]. A high number of cells are able to pack into the interior of the microspheres and the high cell attachment on the microspheres is critical for adipose tissue regeneration as high cell-cell contact is necessary for tissue growth. Adipogenesis of the isolated ASCs is induced for 3-4 days in growth medium containing Dexamethasone, Indomethacin, and 3-isobuytl-1-methylxanthine (IBMX)[10],[11]. The cells are then combined with the microspheres for a few hours and subsequently injected subcutaneously in a nude mouse model for testing. Early in vitro experiments comparing the growth and differentiation of the cells on the NF-SMS against enclosed nanofibrous hollow microspheres as a control show increased cell attachment and integration on the NF-SMS. The cells on the NF-SMS also showed greater Nile Red lipid staining and overall positive results in vitro. Current in vivo experiments are being done and are incorporating poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded with insulin for sustained released of insulin from these particles during the early period of growth (1-2 weeks). Insulin appears to be very critical in the adipogenesis pathway and should be crucial in helping to produce substantial tissue in vivo[12]-[14]. These PLGA nanoparticles are injected along with the microsphere-cell complexes. Having a patient regenerate adipose tissue from their own pre-adipocyte cells will be advantageous because it eliminates the need for something foreign in the body and multiple invasive surgeries. Ensuring that the adipose tissue produced does not resorb as is the case in previous research attempts would be done by functionalizing the microsphere scaffolds with an angiogenic factor, which is the next goal of this project.

Possible role of mechanical force in regulating regeneration of the vascularized fat flap inside a tissue engineering chamber

In plastic and reconstructive surgery, adipose tissue is widely used as effective filler for tissue defects. Strategies for treating soft tissue deficiency, which include free adipose tissue grafts, use of hyaluronic acid, collagen injections, and implantation of synthetic materials, have several clinical limitations. With the aim of overcoming these limitations, researchers have recently utilized tissue engineering chambers to produce large volumes of engineered vascularized fat tissue. However, the process of growing fat tissue in a chamber is still relatively limited, and can result in unpredictable or dissatisfactory final tissue volumes. Therefore, detailed understanding of the process is both necessary and urgent.Many studies have shown that mechanical force can change the function of cells via mechanotransduction. Here, we hypothesized that, besides the inflammatory response, one of the key factors to control the regeneration of vascularized fat flap inside a tissue engineering chamber might be the balance of mechanical forces. To test our hypothesis, we intend to change the balance of forces by means of measures in order to make the equilibrium point in favor of the direction of regeneration. If those measures proved to be feasible, they could be applied in clinical practice to engineer vascularized adipose tissue of predictable size and shape, which would in turn help in the advancement of tissue engineering.

Understanding the effects of mature adipocytes and endothelial cells on fatty acid metabolism and vascular tone in physiological fatty tissue for vascularized adipose tissue engineering.

Engineering of large vascularized adipose tissue constructs is still a challenge for the treatment of extensive high-graded burns or the replacement of tissue after tumor removal. Communication between mature adipocytes and endothelial cells is important for homeostasis and the maintenance of adipose tissue mass but, to date, is mainly neglected in tissue engineering strategies. Thus, new co-culture strategies are needed to integrate adipocytes and endothelial cells successfully into a functional construct. This review focuses on the cross-talk of mature adipocytes and endothelial cells and considers their influence on fatty acid metabolism and vascular tone. In addition, the properties and challenges with regard to these two cell types for vascularized tissue engineering are highlighted.

Reconstruction of maxillary defect with musculo-adipose rectus free flap.

The rectus myocutaneous free flap (RMFF) is used for medium to large maxillectomy defects. However, in patients with central obesity the inset could be difficult due to the bulk from excessive layer of adipose tissue. We describe a modification of the RMFF for patients with excessive central obesity with a flap consisting of adipose tissue with minimal rectus muscle; the musculo-adipose rectus free flap (MARF). Five cases of MARF reconstruction were performed between 2003 and 2013, with patients' body mass indexes ranging from 29.0 to 41.2 kg/m2 . All patients had sinonasal tumor, of which three were adenoid cystic carcinoma, one squamous cell carcinoma, and one melanoma. Four patients had Codeiro IIIb defects and one had Codeiro II defect. Using the MARF technique, the maxillectomy defect was obliterated with vascularized adipose tissue overlying the rectus muscle and was trimmed to fit the maxillectomy defect. The adipose tissue was allowed to granulate and mucosalize. The volume of adipose tissue harvested was between 120 and 160 mL. All flaps survived with no requirement for re-exploration. Complete oro-nasal separation was achieved in all patients. The time to commencement of oral intake ranges from 5 to 15 days. One patient developed seroma and one developed wound breakdown on the donor site. The length of stay at the hospital ranges from 9 to 22 days. On follow-up ranging 7.5-32.8 months, two patients died from their malignancies. The other three patients were able to tolerate oral soft diet. The MARF may be considered as an alternative to myocutaneous rectus free flap particularly for the reconstruction of maxillary defects in patients with central obesity. © 2015 Wiley Periodicals, Inc. Microsurgery 37:137-141, 2017.

Engineering vascularized adipose tissue using the stromal-vascular fraction and fibrin hydrogels.

The development of vascularized and functional adipose tissue substitutes is required to improve soft tissue augmentation. In this study, vascularized adipose tissue constructs were generated using uncultured cells from the stromal-vascular fraction (SVF) of adipose tissue as an alternative cell source to adipose-derived stem cells. SVF cell behavior and tissue formation were compared in a stable fibrin formulation developed by our group and a commercial fibrin sealant (TissuCol; Baxter) upon direct subcutaneous implantation in a nude mouse model. Further, the effect of in vitro adipogenic induction on SVF cell development was investigated by implanting stable fibrin constructs after 1 week of precultivation (adipogenic vs. noninduced control). Constructs were thoroughly analyzed before implantation regarding adipogenic differentiation status, cell viability, and distribution as well as the presence of endothelial cells. Before implantation, in vitro precultivation strongly promoted adipogenesis (under adipogenic conditions) and the formation of CD31(+) prevascular structures by SVF cells (under nonadipogenic conditions). Tissue development in vivo was determined after 4 weeks by histology (hematoxylin and eosin, human vimentin) and quantified histomorphometrically. In stable fibrin gels, adipogenic precultivation was superior to noninduced conditions, resulting in mature adipocytes and the formation of distinct vascular structures of human origin in vivo. Strong neovascularization by the implanted cells predominated in noninduced constructs. Without pretreatment, the SVF in stable fibrin gels displayed only a weak differentiation capability. In contrast, TissuCol gels strongly supported the formation of coherent and well-vascularized adipose tissue of human origin, displaying large unilocular adipocytes. The developed native-like tissue architecture was highlighted by a whole mount staining technique. Taken together, SVF cells from human adipose tissue were shown to successfully lead to adipose tissue formation in fibrin hydrogels in vivo. The results render the SVF a promising cell source for subsequent studies both in vitro and in vivo with the aim of engineering clinically applicable soft tissue substitutes.

Pedicled Adipose Tissue for Treatment of Chronic Digital Osteomyelitis

To describe a surgical technique (pedicled vascularized tissue transfer) for treating chronic digital osteomyelitis. Adipose tissue was obtained at the level of the proximal phalanx based on anterograde or retrograde flow. After bone debridement, we inserted the vascularized adipose tissue into the dead space. Eight patients were treated with this procedure from 2009 to 2012. One patient had chronic osteomyelitis in the thumb, 4 in the index finger, 2 in the middle finger, and 1 in the ring finger. Foci of chronic osteomyelitis were located at the distal phalanx in 2 patients, at the distal to middle phalanx across the distal interphalangeal joint in 4, at the middle phalanx in 1, and at the proximal phalanx in 1. Mean duration of follow-up was 41 months. We assessed the efficacy of the technique by clinical symptoms and imaging. We used retrograde pedicled adipose tissue transfer in 7 patients and anterograde pedicled adipose tissue transfer in 1. The pedicled adipose tissue was successfully transferred from the digit tip to its base. The postoperative courses were uneventful; no additional treatments were required. Postoperative physical data and follow-up images showed no evidence of chronic osteomyelitis. No functional loss was caused by procuring vascularized adipose tissue from the digits. Pedicled vascularized tissue transfer based on the digital artery was a reliable and reproducible technique. We recommend it as a treatment option for chronic digital osteomyelitis. Therapeutic IV.

Cell‐synthesized extracellular matrix particles for tissue engineering and aesthetic applications (87.2)

With age, or after injury, subcutaneous adipose and conjunctive tissue loss can cause poor aesthetic appearance. Current injectable tissue fillers trigger foreign body responses that eventually lead to their degradation or encapsulation. The ideal dermal filler would provide initial structural support but also trigger a regenerative process and lead to the creation of a new permanent tissue. The goal of this project is to develop a new class of fillers that provides long‐term results by triggering the regeneration of a stable, living and vascularized adipose tissue.Using the Tissue Engineering by Self‐Assembly (TESA) approach, sheets of ECM produced by normal human fibroblasts in vitro were dehydrated and reduced to a particulate form that could be injected subcutaneously in nude mice. The ECM particles caused minimal inflammation or encapsulations. Most notably, vascularization and adipogenesis were observed at the injection site, neither of which was noted when using two popular dermal fillers (Juvederm® or Radiesse®). Progression of adipogenesis around the ECM particles was noted throughout the duration of the study (3 months). In separate studies, particles were cast in vitro to produce finely channelized structures that could be seeded with endothelial cells. This approach offers a viable strategy for the production pre‐vascularized bulk tissue to address secretory organ tissue engineering.Conclusion: Fibroblast‐synthesized particles combine “off‐the‐shelf” availability and a persistent ECM that provides mechanical support while triggering the development of a vascularized adipose tissue. Clinical studies are underway to compare this new regenerative dermal filler with the standard of care.

Injectable cell/hydrogel microspheres induce the formation of fat lobule-like microtissues and vascularized adipose tissue regeneration

In this paper, we demonstrated that collagen/alginate microspheres could be generated by a non-contact microfabrication device and serve as excellent cell embedding and delivery devices as they were porous, injectable and able to provide growth- and differentiation-supporting matrix for human adipose-derived stem cells (hASCs). The microsphere matrix demonstrated highly porous structure and mechanical stability for as long as 90 days. hASCs demonstrated high viability after microsphere formation as well as higher proliferation and more mature adipocytes induction compared to two-dimensional culture. After four weeks culture in adipogenic differentiation medium, adipocytes/collagen/alginate microspheres highly mimicking natural fat lobules were obtained and injected subcutaneously into the head of node mice. The in vivo study demonstrated vascularized adipose tissue formation in four weeks. The regenerated vasculature among the transplantation showed functional anastomosis with host vasculature, suggesting that these cell/hydrogel microspheres present injectable adipocytes delivery devices capable of generating vascularized adipose tissue in vivo and thus suitable for cell transplantation and tissue regeneration.

Vascularized Bone Marrow Allotransplantation and Low-Dose Cyclosporine Prolong the Survival of Adipose Tissue Allografts

Composite tissue allotransplantation holds promise in reconstructive surgery, but its application is limited by the need for long-term immunosuppression. The objective of this study was to investigate the feasibility of low-dose cyclosporine and vascularized bone allotransplantation in prolonging the survival of vascularized adipose tissue allograft. In the adipose tissue allograft model, adipose tissue allografts based on superficial epigastric vessels from Lewis-Brown-Norway rats were allotransplanted into Lewis rats. In the adipose tissue and bone marrow allograft model, combined vascularized bone marrow and adipose tissues were allografted from Brown Norway rats into Lewis rats. The graft survival, the onset and progression of rejection, and the effects of cyclosporine at different dosages and treatment durations were recorded. A rejection grading system was created based on gross observation and was correlated with histologic examinations. Even at a low dose of 2 mg/kg/day, cyclosporine continued to provide effective allograft protection. Tolerance was not observed in either model. Adipose tissue survival after discontinuation of cyclosporine was independent of treatment duration. The inclusion of vascularized bone to the adipose tissue allograft provided an additional protective effect. This effect was synergistic with concomitant use of immunosuppressant. Adipose tissue allotransplantation is a potential reconstructive option that requires only minimal use of immunosuppressants. Its survival can be further prolonged with simultaneous bone marrow allotransplantation.