Hydrogels in adipose tissue engineering-Potential application in post-mastectomy breast regeneration

Advanced Nanobiocomposite Hydrogels Incorporating Organofunctionalized LDH for Soft Tissue Engineering Applications

Nanocomposite hydrogels are gaining significant attention for biomedical applications in soft tissue engineering due to the increasing demand for highly flexible and durable soft polymer materials. This research paper focused on investigating and optimizing a procedure for the development of novel nanocomposite hydrogels based on poly(2-hydroxyethyl methacrylate)-co-(2-acrylamido-2-methylpropane sulfonic acid) (HEMA/AMPSA) copolymers. These hydrogels were synthesized through a grafting-through process, where the polymer network was formed using a modified clay crosslinker. The layered double hydroxide (LDH) clay modified with 3-(trimethoxysilyl)propyl methacrylate (ATPM) was synthesized using a novel recipe through a two-step procedure. The nanocomposite hydrogel compositions were optimized to achieve soft hydrogels with high flexibility. The developed materials were analyzed for their mechanical and morphological properties using tensile and compressive tests, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and micro-computed tomography (micro-CT). The swelling behavior, network density, and kinetic diffusion mechanism demonstrated the specific characteristics of the materials. The modified LDH-ATPM was further characterized using Thermogravimetry (TGA), FTIR-ATR and X-ray diffraction (XRD). Biological assessments on human adipose-derived stem cells (hASCs) were essential to evaluate the biocompatibility of the nanocomposite hydrogels and their potential for soft tissue applications.

Clinically Relevant and Precisely Printable Live Adipose Tissue-Based Bio-Ink for Volumetric Soft Tissue Reconstruction

Autologous fat is widely used in soft tissue reconstruction; however, significant volume reduction owing to necrosis and degradation of the transplanted adipose tissue (AT) remains a major challenge. To address this issue, a novel live AT micro-fragment-based bio-ink (ATmf bio-ink) compatible with precision 3D printing, is developed. Live AT micro-fragments of ≈280 µm in size are prepared using a custom tissue micronizer and they are incorporated into a fibrinogen/gelatin mixture to create the ATmf bio-ink. AT micro-fragments exhibit high viability and preserve the heterogeneous cell population and extracellular matrix of the native AT. The developed bio-ink enables precise micropatterning and provides an excellent adipo-inductive microenvironment. AT grafts produced by co-printing the bio-ink with polycaprolactone demonstrate a 500% improvement in volume retention and a 300% increase in blood vessel infiltration in vivo compared with conventional microfat grafts. In vivo engraftment of AT grafts is further enhanced by using a stem cell-laden ATmf bio-ink. Last, it is successfully demonstrated that the bio-ink is enabled for the creation of clinically relevant and patient-specific AT grafts for patients undergoing partial mastectomy. This novel ATmf bio-ink for volumetric soft tissue reconstruction offers a pioneering solution for addressing the limitations of existing clinical techniques.

Shape Memory Polyurethane Foams With Tunable Mechanical Properties and Radiation Tolerance for Breast Repair and Reconstruction

This study developed a shape memory polyurethane foam (SM-PUF) with tunable mechanical properties and exceptional radiation tolerance for potentially implanting tissue defects after mastectomy. The PUFs were synthesized via an in situ foaming strategy using water as a foaming agent, incorporating 4,4'-diphenylmethane diisocyanate (MDI) as the rigid segment and both polyoxytetramethylene glycol and polycaprolactone as the soft segment. The resultant PUFs possess an open-cell structure with a pore size of 30 ~ 800 μm, which achieves a compressive stress of 0.04 MPa under 70% compression strain and a tensile elongation of 667.9%. PUFs exhibit body temperature (37°C)-responsive softening and shape memory abilities, with recovery and fixation ratios reaching 88% and 98%, respectively. It was verified that PUFs can resist 40 Gy radiotherapy without changing their mechanical properties and biocompatibility. This study introduces an innovative approach to produce customizable foam for the reconstruction of implant prostheses for the breast.

Recent advances of injectable in situ-forming hydrogels for preventing postoperative tumor recurrence

The unavoidable residual tumor tissue from surgery and the strong aggressiveness of tumor cells pose challenges to the postoperative treatment of tumor patients, accompanied by in situ tumor recurrence and decreased quality of life. Therefore, there is an urgent need to explore appropriate postoperative therapeutic strategies to remove residual tumor cells after surgery to inhibit tumor recurrence and metastasis after surgery. In recent years, with the rapid development of biomedical materials, the study of local delivery systems as postoperative delivery of therapeutic agents has gradually attracted the attention of researchers. Injectable in situ-forming hydrogel is a locally administered agent injected in situ as a solution that can be loaded with various therapeutic agents and rapidly gels to form a semi-solid gel at the treatment site. This type of hydrogel tightly fills the surgical site and covers irregular excision surfaces. In this paper, we review the recent advances in the application of injectable in situ-forming hydrogels in postoperative therapy, focusing on the matrix materials of this type of hydrogel and its application in the postoperative treatment of different types of tumors, as well as discussing the challenges and prospects of its clinical application.

Human breast tissue engineering in health and disease

The human mammary gland represents a highly organized and dynamic tissue, uniquely characterized by postnatal developmental cycles. During pregnancy and lactation, it undergoes extensive hormone-stimulated architectural remodeling, culminating in the formation of specialized structures for milk production to nourish offspring. Moreover, it carries significant health implications, due to the high prevalence of breast cancer. Therefore, gaining insight into the unique biology of the mammary gland can have implications for managing breast cancer and promoting the well-being of both women and infants. Tissue engineering techniques hold promise to narrow the translational gap between existing breast models and clinical outcomes. Here, we provide an overview of the current landscape of breast tissue engineering, outline key requirements, and the challenges to overcome for achieving more predictive human breast models. We propose methods to validate breast function and highlight preclinical applications for improved understanding and targeting of breast cancer. Beyond mammary gland physiology, representative human breast models can offer new insight into stem cell biology and developmental processes that could extend to other organs and clinical contexts.

Reconstructing Curves: A Bottom-Up Approach toward Adipose Tissue Regeneration with Recombinant Biomaterials

The potential of recombinant materials in the field of adipose tissue engineering (ATE) is investigated using a bottom-up tissue engineering (TE) approach. This study explores the synthesis of different photo-crosslinkable gelatin derivatives, including both natural and recombinant materials, with a particular emphasis on chain growth and step growth polymerization. Gelatin type B (Gel-B) and a recombinant collagen peptide (RCPhC1) are used as starting materials. The gel fraction and mass swelling properties of 2D hydrogel films are evaluated, revealing high gel fractions exceeding 94% and high mass swelling ratios >15. In vitro experiments with encapsulated adipose-derived stem cells (ASCs) indicate viable cells (>85%) throughout the experiment with the RCPhC1-based hydrogels showing a higher number of stretched ASCs. Triglyceride assays show the enhanced differentiation potential of RCPhC1 materials. Moreover, the secretome analysis reveal the production of adipose tissue-specific proteins including adiponectin, adipsin, lipocalin-2/NGAL, and PAL-1. RCPhC1-based materials exhibit higher levels of adiponectin and adipsin production, indicating successful differentiation into the adipogenic lineage. Overall, this study highlights the potential of recombinant materials for ATE applications, providing insights into their physico-chemical properties, mechanical strength, and cellular interactions.

Formulation Effects on the Mechano-Physical Properties of In Situ-Forming Resilient Hydrogels for Breast Tissue Regeneration

The need for a long-term solution for filling the defects created during partial mastectomies due to breast cancer diagnosis has not been met to date. All available defect-filling methods are non-permanent and necessitate repeat procedures. Here, we report on novel injectable porous hydrogel structures based on the natural polymers gelatin and alginate, which are designed to serve for breast reconstruction and regeneration following partial mastectomy. The effects of the formulation parameters on the mechanical and physical properties were thoroughly studied. The modulus in compression and tension were in the range of native breast tissue. Both increased with the increase in the crosslinker concentration and the polymer-air ratio. Resilience was very high, above 93% for most studied formulations, allowing the scaffold to be continuously deformed without changing its shape. The combination of high resilience and low elastic modulus is favored for adipose tissue regeneration. The physical properties of gelation time and water uptake are controllable and are affected mainly by the alginate and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) concentrations and less by the polymer-air ratio. In vitro cell viability tests were performed on mouse preadipocytes and indicated high biocompatibility. The minimally invasive nature of this approach, along with the excellent properties of the scaffold, will enable the filling of complex voids while simultaneously decreasing surgical costs and greatly improving patient well-being.

Oxidized cellulose-filled double thermo/pH-sensitive hydrogel for local chemo-photothermal therapy in breast cancer

Lumpectomy plus radiation is a treatment option offering better survival than conventional mastectomy for patients with early-stage breast cancer. However, successive radioactive therapy remains tedious and unsafe with severe adverse reactions and secondary injury. Herein, a composite hydrogel with pH- and photothermal double-sensitive activity is developed via physical crosslinking. The composite hydrogel incorporated with tempo-oxidized cellulose nanofiber (TOCN), polyvinyl alcohol (PVA) and a polydopamine (PDA) coating for photothermal therapy (PTT) triggered in situ release of doxorubicin (DOX) drug was utilized to optimize postoperative strategies of malignant tumors inhibition. The incorporation of TOCN significantly affects the performance of composite hydrogels. The best-performing TOCN/PVA7 was selected for drug loading and polydopamine coating by rational design. In vitro studies have demonstrated that the composite hydrogel exhibited high NIR photothermal conversion efficiency, benign cytotoxicity to L929 cells, pH-dependent release profiles, and strong MCF-7 cell inhibitory effects. Then the TOCN/PVA7-PDA@DOX hydrogel is implanted into the tumor resection cavity for local in vivo chemo-photothermal synergistical therapy to ablate residue tumor tissues. Overall, this work suggests that such a chemo-photothermal hydrogel delivery system has great potential as a promising tool for the postsurgical management of breast cancer.

Strategies for Constructing Tissue-Engineered Fat for Soft Tissue Regeneration

BACKGROUND

Repairing soft tissue defects caused by inflammation, tumors, and trauma remains a major challenge for surgeons. Adipose tissue engineering (ATE) provides a promising way to solve this problem.

METHODS

This review summarizes the current ATE strategies for soft tissue reconstruction, and introduces potential construction methods for ATE.

RESULTS

Scaffold-based and scaffold-free strategies are the two main approaches in ATE. Although several of these methods have been effective clinically, both scaffold-based and scaffold-free strategies have limitations. The third strategy is a synergistic tissue engineering strategy and combines the advantages of scaffold-based and scaffold-free strategies.

CONCLUSION

Personalized construction, stable survival of reconstructed tissues and functional recovery of organs are future goals of building tissue-engineered fat for ATE.

Long term observation of de novo adipogenesis using novel bioabsorbable implants with larger size in a porcine model

Introduction

The regeneration of adipose tissue in patients after breast cancer surgery would be desirable without the use of growth factors or cells to avoid potential recurrence and metastasis. We reported that prolate spheroidal-shaped poly-L-lactic acid (PLLA) mesh implants of approximately 18-mm polar diameter and 7.5-mm greatest equatorial diameter containing collagen sponge (CS) would be replaced by regenerated adipose tissue after implantation, thereby suggesting an innovative method for breast reconstruction. Our study aimed to evaluate the adipose tissue regeneration ability of implant aggregates in a porcine model.

Methods

We prepared implant aggregates consisting of thirty PLLA mesh implants containing CS packed in a woven poly (glycolic acid) bag. The implant aggregates were inserted under the mammary glands in the porcine abdomen for a year. Single and double groups were classified by inserting either one or two implant aggregates on each side of the abdomen, respectively.

Results

In both groups, the volume of the implant aggregates decreased over time, and the formation of adipose tissue peaked between 6 and 9 months. Histologically, the formation of adipose tissue was confirmed in the area that was in contact with native adipose tissue.

Conclusions

Our implant aggregates could induce the autologous adipose tissue after long term implantation in vivo, without the use of any growth factor or cell treatment, presenting a potential novel method of breast reconstruction.

Synthesis and characterization of a silk fibroin/placenta matrix hydrogel for breast reconstruction

Reconstructive surgery is a complex and demanding interdisciplinary field. One of the major challenges is the production of sizeable, implantable, inexpensive bioprostheses such as breast implants. In this study, porous hybrid hydrogels were fabricated by a combinatorial method using decellularized human placenta (dHplacenta) and silk fibroin. Histology was used to confirm the acellularity of the dHplacenta. The physio-chemical properties of the hydrogels were evaluated using SEM, FTIR, and rheological assays. The synthesized hydrogels exhibited a uniform 3-D microstructure with an interconnected porous network, and the hybrid hydrogels with a 30/70 ratio had improved mechanical properties compared to the other hydrogels. Hybrid hydrogels were also cultured with adipose-derived mesenchymal stem cells (ADSCs). Liposuction was used to obtain adipose tissue from patients, which was then characterized using flow cytometry and karyotyping. The results showed that CD34 and CD31 were downregulated, whereas CD105 and CD90 were upregulated in ADSCs, indicating a phenotype resembling to that of mesenchymal stem cells from the human bone marrow. Moreover, after re-cellularized hydrogel, the live/dead assay and SEM analysis confirmed that most viability and cellular expansion on the hydrogels contained higher ratios of dHplacenta (30/70) than the other two groups. All these findings recapitulated that the 30/70 dHplacenta/silk fibroin hydrogel can perform as an excellent substrate for breast tissue engineering applications.

A review of bioengineering techniques applied to breast tissue: Mechanical properties, tissue engineering and finite element analysis

Female breast cancer was the most prevalent cancer worldwide in 2020, according to the Global Cancer Observatory. As a prophylactic measure or as a treatment, mastectomy and lumpectomy are often performed at women. Following these surgeries, women normally do a breast reconstruction to minimize the impact on their physical appearance and, hence, on their mental health, associated with self-image issues. Nowadays, breast reconstruction is based on autologous tissues or implants, which both have disadvantages, such as volume loss over time or capsular contracture, respectively. Tissue engineering and regenerative medicine can bring better solutions and overcome these current limitations. Even though more knowledge needs to be acquired, the combination of biomaterial scaffolds and autologous cells appears to be a promising approach for breast reconstruction. With the growth and improvement of additive manufacturing, three dimensional (3D) printing has been demonstrating a lot of potential to produce complex scaffolds with high resolution. Natural and synthetic materials have been studied in this context and seeded mainly with adipose derived stem cells (ADSCs) since they have a high capability of differentiation. The scaffold must mimic the environment of the extracellular matrix (ECM) of the native tissue, being a structural support for cells to adhere, proliferate and migrate. Hydrogels (e.g., gelatin, alginate, collagen, and fibrin) have been a biomaterial widely studied for this purpose since their matrix resembles the natural ECM of the native tissues. A powerful tool that can be used in parallel with experimental techniques is finite element (FE) modeling, which can aid the measurement of mechanical properties of either breast tissues or scaffolds. FE models may help in the simulation of the whole breast or scaffold under different conditions, predicting what might happen in real life. Therefore, this review gives an overall summary concerning the human breast, specifically its mechanical properties using experimental and FE analysis, and the tissue engineering approaches to regenerate this particular tissue, along with FE models.

The diversified hydrogels for biomedical applications and their imperative roles in tissue regeneration

Repair and regeneration of tissues after injury are complex pathophysiological processes. Microbial infection, malnutrition, and an ischemic and hypoxic microenvironment in the injured area can impede the typical healing cascade. Distinguished by biomimicry of the extracellular matrix, high aqueous content, and diverse functions, hydrogels have revolutionized clinical practices in tissue regeneration owing to their outstanding hydrophilicity, biocompatibility, and biodegradability. Various hydrogels such as smart hydrogels, nanocomposite hydrogels, and acellular matrix hydrogels are widely used for applications ranging from bench-scale to an industrial scale. In this review, some emerging hydrogels in the biomedical field are briefly discussed. The protective roles of hydrogels in wound dressings and their diverse biological effects on multiple tissues such as bone, cartilage, nerve, muscle, and adipose tissue are also discussed. The vehicle functions of hydrogels for chemicals and cell payloads are detailed. Additionally, this review emphasizes the particular characteristics of hydrogel products that promote tissue repair and reconstruction such as anti-infection, inflammation regulation, and angiogenesis.

The impact of adipokines on vascular networks in adipose tissue

Adipose tissue (AT) is a highly active and plastic endocrine organ. It secretes numerous soluble molecules known as adipokines, which act locally to AT control the remodel and homeostasis or exert pleiotropic functions in different peripheral organs. Aberrant production or loss of certain adipokines contributes to AT dysfunction associated with metabolic disorders, including obesity. The AT plasticity is strictly related to tissue vascularization. Angiogenesis supports the AT expansion, while regression of blood vessels is associated with AT hypoxia, which in turn mediates tissue inflammation, fibrosis and metabolic dysfunction. Several adipokines can regulate endothelial cell functions and are endowed with either pro- or anti-angiogenic properties. Here we address the role of adipokines in the regulation of angiogenesis. A better understanding of the link between adipokines and angiogenesis will open the way for novel therapeutic approaches to treat obesity and metabolic diseases.

Injectable anti-cancer drug loaded silk-based hydrogel for the prevention of cancer recurrence and post-lumpectomy tissue regeneration aiding triple-negative breast cancer therapy

A single system capable of delivering anticancer drugs and growth factors by a minimally invasive approach is in demand for effective treatment of triple-negative breast cancer (TNBC) after lumpectomy. Here, we showcase one such holistic system for TNBC therapy and its assessment via 3D in vitro lumpectomy model, a first of its kind. Firstly, Bombyx mori silk fibroin (BMSF) and Antheraea assamensis silk fibroin (AASF) blended hydrogels were prepared and biophysically characterized. Secondly, a 3D in vitro lumpectomy model was developed using MDA-MB-231 cell line to assess the efficacy of localized delivery of doxorubicin (dox) using injectable hydrogel system in terminating remaining breast cancer after lumpectomy. Additionally, we have also evaluated the adipose tissue regeneration in the lumpectomy region by delivering dexamethasone (dex) using injectable hydrogels. Rheological studies showed that the BMSF/AASF blended hydrogels exhibit viscoelasticity and injectability conducive for minimally invasive application. The developed hydrogels by virtue of its slow and sustained release of dox exerted cytotoxicity towards MDA-MB-231 cells assessed through in vitro studies. Further, dex loaded hydrogel supported adipogenic differentiation of adipose tissue derived stem cells (ADSCs), while the secreted factors were found to aid in vascularization and macrophage polarization. This was confirmed through in vitro angiogenic tube formation assay and macrophage polarization study respectively. The corroborated results vouch for potential application of this injectable hydrogels for localized anticancer drug delivery and aiding in breast reconstruction, post lumpectomy.

Human fibroblasts facilitate the generation of iPSCs-derived mammary-like organoids

Background

Breast cancer is the most common malignancy in women worldwide, and its treatment largely depends on mastectomy. Patients after mastectomy suffer from crippled body image, self-esteem, and quality of life. Post-mastectomy breast reconstruction can improve patients’ psychosocial health. Although silicone and fat have been widely used for breast reconstruction, they have remarkable limitations. Our study aimed to establish an improved method for breast reconstruction from human-induced pluripotent stem cells (iPSCs).

Methods

We used a two-step procedure to induce mammary-like organoids (MLOs) from iPSCs and applied transcriptome sequencing to analyze the gene expression profiles during the development process from embryoid bodies (mEBs) to MLOs. Moreover, we evaluated the in vitro effect of fibroblasts cell line HFF (human foreskin fibroblasts) on the size and morphology of MLOs and explored the in vivo effect of HFF on regeneration rate of MLOs.

Results

MLOs had a similar gene expression profile and morphogenesis as the normal mammary glands. Furthermore, the addition of HFF increases the branching ratio and organoid diameters and facilitates the formation of multiple cell layers duct-like structures in MLOs in vitro. Finally, orthotopical transplantation of the MLOs to cleared mammary gland fad pad of NSG mice showed that HFF increases the formation of mammary gland-like structures.

Conclusions

Fibroblasts facilitate iPSC-derived MLOs to generate mammary gland-like structures in both in vitro and in vivo conditions. Our findings lay a foundation for breast reconstruction by using iPSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03023-7.

Preliminary report of de novo adipogenesis using novel bioabsorbable implants and image evaluation using a porcine model

Our bioabsorbable poly-l-lactic acid (PLLA) mesh implants containing collagen sponge are replaced with adipose tissue after implantation, and this is an innovative method for breast reconstruction. In this preliminary study, we investigated the formation of adipose tissue and evaluated the process via multimodal images in a porcine model using an implant aggregate to generate the larger adipose tissue. The implant aggregate consists of PLLA mesh implants containing collagen sponge and a poly-glycolic acid woven bag covering them. We inserted the implant aggregates under the porcine mammary glands. Magnetic resonance imaging (MRI), ultrasonography (USG), and 3-dimensional (3D) surface imaging and histological evaluations were performed to evaluate the formation of adipose tissue over time. The volume of the implant aggregate and the formed adipose tissue inside the implant aggregate could be evaluated over time via MRI. The space within the implant aggregate was not confirmed on USG due to the acoustic shadow of the PLLA threads. The change in volume was not confirmed precisely using 3D surface imaging. Histologically, the newly formed adipose tissue was confirmed on the skin side of the implant aggregate. This implant aggregate has the ability to regenerate adipose tissue, and MRI is an appropriate method for the evaluation of the volume of the implant aggregation and the formation of adipose tissue.

Photothermal hydrogel platform for prevention of post-surgical tumor recurrence and improving breast reconstruction

Background

As one of the leading threats for health among women worldwide, breast cancer has high morbidity and mortality. Surgical resection is the major clinical intervention for primary breast tumor, nevertheless high local recurrence risk and breast tissue defect remain two main clinical dilemmas, seriously affecting survival and quality of life of patients.

Experimental

We developed a thermoresponsive and injectable hybrid hydrogel platform (IR820/Mgel) by integration of co-loaded porous microspheres (MPs) and IR820 for preventing postoperative recurrence of breast cancer via photothermal therapy and promoting subsequent breast reconstruction.

Results

Our results suggested that IR820/Mgel could quickly heated to more than 50.0 ℃ under NIR irradiation, enabling killing effect on 4T1 cells in vitro and prevention effect on post-surgical tumor recurrence in vivo. In addition, the hydrogel platform was promising for its minimal invasion and capability of filling irregularly shaped defects after surgery, and the encapsulated MPs could help to increase the strength of gel to realize a long-term in situ function in vivo, and promoted the attachment and anchorage property of normal breast cells and adipose stem cells.

Conclusions

This photothermal hydrogel platform provides a practice paradigm for preventing locally recurrence of breast cancer and a potential option for reconstruction of breast defects.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01041-w.

Cellulose Nanofiber-Based Hydrogels Embedding 5-FU Promote Pyroptosis Activation in Breast Cancer Cells and Support Human Adipose-Derived Stem Cell Proliferation, Opening New Perspectives for Breast Tissue Engineering

The structure and biocompatibility analysis of a hydrogel based on cellulose nanofibers (CNFs) combined with alginate/pectin (A.CNF or P.CNF) and enriched with 1% or 5% 5-FU revealed more favorable properties for the cellular component when pectin was dispersed within CNFs. 5-Fluorouracil (5-FU) is an antimetabolite fluoropyrimidine used as antineoplastic drug for the treatment of multiple solid tumors. 5-FU activity leads to caspase-1 activation, secretion and maturation of interleukins (IL)-1, IL-18 and reactive oxygen species (ROS) generation. Furthermore, the effects of embedding 5-FU in P.CNF were explored in order to suppress breast tumor cell growth and induce inflammasome complex activation together with extra- and intracellular ROS generation. Exposure of tumor cells to P.CNF/5-FU resulted in a strong cytotoxic effect, an increased level of caspase-1 released in the culture media and ROS production—the latter directly proportional to the concentration of anti-tumor agent embedded in the scaffolds. Simultaneously, 5-FU determined the increase of p53 and caspase-1 expressions, both at gene and protein levels. In conclusion, P.CNF/5-FU scaffolds proved to be efficient against breast tumor cells growth due to pyroptosis induction. Furthermore, biocompatibility and the potential to support human adipose-derived stem cell growth were demonstrated, suggesting that these 3D systems could be used in soft tissue reconstruction post-mastectomy.

[Preliminary exploration on the application of hydrogel from acellular porcine adipose tissue to assist lipofilling]

OBJECTIVE

To investigate the effect of hydrogel from acellular porcine adipose tissue (HAPA) on the survival of transplanted adipose tissue.

METHODS

For in vitro study, adipose tissue and HAPA-adipose tissue complex were cultured in normoxia and hypoxia atmospheres for 24 and 72 hours. TUNEL and Perilipin immunofluorescence staining were performed to observe the effect of HAPA on apoptosis and survival of adipocities. For in vivo study, 42 healthy male nude mice (4-6 weeks old) weighing 15-18 g were randomly divided into adipose group (group A), 10%HAPA group (group B), 20%HAPA group (group C), 30%HAPA group (group D), 40%HAPA group (group E), and 50%HAPA group (group F) according to different HAPA/adipose tissue volume ratio ( n=7). For each group, 1 mL adipose tissue or HAPA-adipose tissue complex was injected subcutaneously into the dorsum of the nude mice. At 4 weeks after transplantation, 7 nude mice in each group were sacrificed and grafts were harvested, gross observation, volume measurement, ultrasound examination, and histologic staining (HE staining, CD31 and Perilipin immunofluorescence stainings) were applied.

RESULTS

Hypoxia showed a tendency of promoting adipose tissue necrosis and apoptosis, while HAPA exhibited an obvious effect of inhibiting cell apoptosis in vitro study ( P<0.05). For in vivo study, grafts of all groups had intact fibrocapsule. No obvious signs of infection and necrosis were observed at 4 weeks. Volume shrinkage was observed in all groups, however, the groups A-D had significantly higher volume retention rate than groups E and F ( P<0.05). Ultrasound examination showed that there were no significant difference in the number and volume of liquify area of the grafts in each group ( P>0.05). With the increase of HAPA's volume ratio, HE staining proved an improved fat integrity while a gradually decreased vacuoles and fibrosis. CD31 immunohistochemical staining showed that the number of neo-vascularisation in groups E and F were significantly higher than those in groups A-D ( P<0.05). Perilipin immunofluorescence staining showed that with the increase of HAPA volume ratio, the number of living adipocytes increased gradually, and more new adipocytes could be seen in the field of vision.

CONCLUSION

As the volume ratio of HAPA gradually increased, the survival of transplanted adipose tissue also increased, but the volume retention rate decreased gradually. 30%HAPA was considered the relative optimal volume ratio for its superior adipose tissue survival and volume retation rate.

De novo adipogenesis using a bioabsorbable implant without additional cells or growth factors

Adipose tissue regeneration in breast cancer patients without additional growth factors or adipose-tissue-derived stromal cells is desirable because of the possibility of recurrence and metastasis. We report that a poly-L-lactic acid (PLLA) mesh implant containing a collagen sponge (CS) maintained the internal space in vivo for up to 12 months and substituted for adipose tissue. We developed a PLLA capsule that maintained the internal space longer than that of PLLA mesh and compared adipose tissue formation at 12 and 24 months after implantation between the PLLA mesh with CS implant and the PLLA capsule implant with or without CS in a rabbit model. After 12 months, all implants maintained the internal space, and the adipose tissue that formed in all implant groups was larger than that in the control group. At 24 months, PLLA mesh maintained the internal space just as well as that at 12 months, while the PLLA capsule collapsed and accumulated a large number of macrophages. The formed adipose tissue in the PLLA mesh group was maintained up to 24 months; however, those in two PLLA capsule groups decreased and showed no difference from the control group. In conclusion, the internal space of the PLLA mesh implant with CS was substituted for adipose tissue at 12 months and sustained the formed adipose tissue after 24 months. The PLLA mesh implant containing CS is a desirable bioabsorbable implant that can be replaced by autologous adipose tissue after implantation in vivo without using any growth factors or cells.

Bioprinting predifferentiated adipose-derived mesenchymal stem cell spheroids with methacrylated gelatin ink for adipose tissue engineering

The increasing number of mastectomies results in a greater demand for breast reconstruction characterized by simplicity and a low complication profile. Reconstructive surgeons are investigating tissue engineering (TE) strategies to overcome the current surgical drawbacks. 3D bioprinting is the rising technique for the fabrication of large tissue constructs which provides a potential solution for unmet clinical needs in breast reconstruction building on decades of experience in autologous fat grafting, adipose-derived mesenchymal stem cell (ASC) biology and TE. A scaffold was bioprinted using encapsulated ASC spheroids in methacrylated gelatin ink (GelMA). Uniform ASC spheroids with an ideal geometry and diameter for bioprinting were formed, using a high-throughput non-adhesive agarose microwell system. ASC spheroids in adipogenic differentiation medium (ADM) were evaluated through live/dead staining, histology (HE, Oil Red O), TEM and RT-qPCR. Viable spheroids were obtained for up to 14 days post-printing and showed multilocular microvacuoles and successful differentiation toward mature adipocytes shown by gene expression analysis. Moreover, spheroids were able to assemble at random in GelMA, creating a macrotissue. Combining the advantage of microtissues to self-assemble and the controlled organization by bioprinting technologies, these ASC spheroids can be useful as building blocks for the engineering of soft tissue implants.

Engineering 3D degradable, pliable scaffolds toward adipose tissue regeneration; optimized printability, simulations and surface modification

We present a solution to regenerate adipose tissue using degradable, soft, pliable 3D-printed scaffolds made of a medical-grade copolymer coated with polydopamine. The problem today is that while printing, the medical grade copolyesters degrade and the scaffolds become very stiff and brittle, being not optimal for adipose tissue defects. Herein, we have used high molar mass poly(L-lactide-co-trimethylene carbonate) (PLATMC) to engineer scaffolds using a direct extrusion-based 3D printer, the 3D Bioplotter®. Our approach was first focused on how the printing influences the polymer and scaffold's mechanical properties, then on exploring different printing designs and, in the end, on assessing surface functionalization. Finite element analysis revealed that scaffold's mechanical properties vary according to the gradual degradation of the polymer as a consequence of the molar mass decrease during printing. Considering this, we defined optimal printing parameters to minimize material's degradation and printed scaffolds with different designs. We subsequently functionalized one scaffold design with polydopamine coating and conducted in vitro cell studies. Results showed that polydopamine augmented stem cell proliferation and adipogenic differentiation owing to increased surface hydrophilicity. Thus, the present research show that the medical grade PLATMC based scaffolds are a potential candidate towards the development of implantable, resorbable, medical devices for adipose tissue regeneration.

Tissue engineering and regenerative medicine strategies for the female breast

The complexity of mammary tissue and the variety of cells involved make tissue regeneration an ambitious goal. This review, supported by both detailed macro and micro anatomy, illustrates the potential of regenerative medicine in terms of mammary gland reconstruction to restore breast physiology and morphology, damaged by mastectomy. Despite the widespread use of conventional therapies, many critical issues have been solved using the potential of stem cells resident in adipose tissue, leading to commercial products. in vitro research has reported that adipose stem cells are the principal cellular source for reconstructing adipose tissue, ductal epithelium, and nipple structures. In addition to simple cell injection, construct made by cells seeded on a suitable biodegradable scaffold is a viable alternative from a long‐term perspective. Preclinical studies on mice and clinical studies, most of which have reached Phase II, are essential in the commercialization of cellular therapy products. Recent studies have revealed that the enrichment of fat grafting with stromal vascular fraction cells is a viable alternative to breast reconstruction. Although in the future, organ‐on‐a‐chip can be envisioned, for the moment researchers are still focusing on therapies that are a long way from regenerating the whole organ, but which nevertheless prevent complications, such as relapse and loss in terms of morphology.

Cosmetic reconstruction in breast cancer patients: Opportunities for nanocomposite materials

The most common malignancy in women, breast cancer remains a major medical challenge that affects the life of thousands of patients every year. With recognized benefits to body image and self-esteem, the use of synthetic mammary implants for elective cosmetic augmentation and post-mastectomy reconstruction continues to increase. Higher breast implant use leads to an increased occurrence of implant-related complications associated with implant leakage and rupture, capsular contracture, necrosis and infections, which include delayed healing, pain, poor aesthetic outcomes and the need for revision surgeries. Along with the health status of the implant recipient and the skill of the surgeon, the properties of the implant determine the likelihood of implant-related complications and, in doing so, specific patient outcomes. This paper will review the challenges associated with the use of silicone, saline and "gummy bear" implants in view of their application in patients recovering from breast cancer-related mastectomy, and investigate the opportunities presented by advanced functional nanomaterials in meeting these challenges and potentially opening new dimensions for breast reconstruction. STATEMENT OF SIGNIFICANCE: Breast cancer is a significant cause of morbidity and mortality in women worldwide, which is difficult to prevent or predict, and its treatment carries long-term physiological and psychological consequences. Post-mastectomy breast reconstruction addresses the cosmetic aspect of cancer treatment. Yet, drawbacks of current implants contribute to the development of implant-associated complications, which may lead to prolonged patient care, pain and loss of function. Nanomaterials can help resolve the intrinsic biomechanical mismatch between implant and tissues, enhance mechanical properties of soft implantable materials, and provide an alternative avenue for controlled drug delivery. Here, we explore advances in the use of functionalized nanomaterials to enhance the properties of breast implants, with representative examples that highlight the utility of nanomaterials in addressing key challenges associated with breast reconstruction.