Financial (dis)incentives to surgical management of head and neck cancer care

BACKGROUND

Patients with head and neck cancer (HNC) often require complex surgical reconstruction. This retrospective, cross-sectional study compares financial factors influencing HNC and breast cancer (BC) care to examine care disparities.

METHODS

Pricing data from 2012 to 2021 was abstracted from the CMS Physician Fee Schedule Look-Up Tool. Nonprofit and research support was quantified by searching the NIH, IRS, and GuideStar databases. New York State Department of Health data from 2015 to 2019 was analyzed to compare costs, charges, and payer mix.

RESULTS

HNC reconstructive procedures reimburse lower than comparable breast procedures (p < 0.05). Nonprofit and research support for HNC is disproportionately low relative to disease burden. Patients hospitalized for HNC surgical procedures generated higher costs and lower charges than patients with BC (p < 0.05).

CONCLUSION

Comparatively low procedure reimbursement, low nonprofit support, and high cost of care for patients with HNC relative to patients with BC may contribute to care disparities for patients with HNC.

Bioengineering Full-scale auricles using 3D-printed external scaffolds and decellularized cartilage xenograft

Reconstruction of the human auricle remains a formidable challenge for plastic surgeons. Autologous costal cartilage grafts and alloplastic implants are technically challenging, and aesthetic and/or tactile outcomes are frequently suboptimal. Using a small animal "bioreactor", we have bioengineered full-scale ears utilizing decellularized cartilage xenograft placed within a 3D-printed external auricular scaffold that mimics the size, shape, and biomechanical properties of the native human auricle. The full-scale polylactic acid ear scaffolds were 3D-printed based upon data acquired from 3D photogrammetry of an adult ear. Ovine costal cartilage was processed either through mincing (1 mm3) or zesting (< 0.5 mm3), and then fully decellularized and sterilized. At explantation, both the minced and zested neoears maintained the size and contour complexities of the scaffold topography with steady tissue ingrowth through 6 months in vivo. A mild inflammatory infiltrate at 3 months was replaced by homogenous fibrovascular tissue ingrowth enveloping individual cartilage pieces at 6 months. All ear constructs were pliable, and the elasticity was confirmed by biomechanical analysis. Longer-term studies of the neoears with faster degrading biomaterials will be warranted for future clinical application. STATEMENT OF SIGNIFICANCE: Accurate reconstruction of the human auricle has always been a formidable challenge to plastic surgeons. In this article, we have bioengineered full-scale ears utilizing decellularized cartilage xenograft placed within a 3D-printed external auricular scaffold that mimic the size, shape, and biomechanical properties of the native human auricle. Longer-term studies of the neoears with faster degrading biomaterials will be warranted for future clinical application.

Use of Banked Fibula for Improved Nasal Reconstruction Following Free Fibula Midface Reconstruction

OBJECTIVE

Anterior maxillary deficiency caused by trauma or oncologic resection presents a complex reconstructive challenge. The authors present a technique for 2-stage midface reconstruction utilizing a vascularized free fibula flap for maxillary reconstruction, followed by nasal reconstruction at a second stage utilizing a banked fibula graft.

METHODS

This case series utilizes a 2-stage technique for midface reconstruction. In the first stage, a fibula-free flap was used to reconstruct the maxilla with the excess banked in the abdomen. In the second stage, this bone graft was used to restore the nasal dorsum.

RESULTS

Two patients were included in this series. Patient 1 was a 28-year-old man who presented after a remote gunshot wound to his face, resulting in complete loss of his anterior maxilla and nasal support with midface collapse. Patient 2 was a 65-year-old man who presented with squamous cell carcinoma of the hard palate with extension into the maxilla and nasal septum. In both cases, the flaps healed without complication, providing midface restoration. Placement of the banked fibula graft in a second stage resulted in restoration of dorsal nasal projection.

CONCLUSION

The authors describe the use of "spare" fibula parts for nasal reconstruction after loss of the maxilla and cartilaginous septum. The use of the fibula bone as a graft to restore the nasal dorsum in a delayed manner allows for a better assessment of the esthetic needs after the massive swelling from the initial surgery has abated. Further, this approach eliminates the need for a second donor site for nasal reconstruction.

Breast adipose tissue-derived extracellular vesicles from obese women alter tumor cell metabolism

Breast adipose tissue is an important contributor to the obesity-breast cancer link. Extracellular vesicles (EVs) are nanosized particles containing selective cargo, such as miRNAs, that act locally or circulate to distant sites to modulate target cell functions. Here, we find that long-term education of breast cancer cells with EVs obtained from breast adipose tissue of women who are overweight or obese (O-EVs) results in increased proliferation. RNA-seq analysis of O-EV-educated cells demonstrates increased expression of genes involved in oxidative phosphorylation, such as ATP synthase and NADH: ubiquinone oxidoreductase. O-EVs increase respiratory complex protein expression, mitochondrial density, and mitochondrial respiration in tumor cells. The mitochondrial complex I inhibitor metformin reverses O-EV-induced cell proliferation. Several miRNAs-miR-155-5p, miR-10a-3p, and miR-30a-3p-which promote mitochondrial respiration and proliferation, are enriched in O-EVs relative to EVs from lean women. O-EV-induced proliferation and mitochondrial activity are associated with stimulation of the Akt/mTOR/P70S6K pathway, and are reversed upon silencing of P70S6K. This study reveals a new facet of the obesity-breast cancer link with human breast adipose tissue-derived EVs causing metabolic reprogramming of breast cancer cells.

Reducing Peri-implant Capsule Thickness in Submuscular Rodent Model of Breast Reconstruction With Delayed Radiotherapy

INTRODUCTION

Capsular contracture remains the most common complication following device-based breast reconstruction, occurring in up to 50% of women who also undergo adjuvant radiotherapy either before or after device-based reconstruction. While certain risk factors for capsular contracture have been identified, there remains no clinically effective method of prevention. The purpose of the present study is to determine the effect of coating the implant with the novel small molecule Met-Z2-Y12, with and without delayed, targeted radiotherapy, on capsule thickness and morphologic change around smooth silicone implants placed under the latissimus dorsi in a rodent model.

METHODS

Twenty-four female Sprague Dawley rats each had 2 mL smooth round silicone breast implants implanted bilaterally under the latissimus dorsi muscle. Twelve received uncoated implants and twelve received implants coated with Met-Z2-Y12. Half of the animals from each group received targeted radiotherapy (20 Gray) on postoperative day ten. At three and 6 months after implantation, the tissue surrounding the implants was harvested for analysis of capsular histology including capsule thickness. Additionally, microCT scans were qualitatively analyzed for morphologic change.

RESULTS

Capsules surrounding Met-Z2-Y12-coated implants were significantly thinner (P = 0.006). The greatest difference in capsule thickness was seen in the irradiated 6-month groups, where mean capsule thickness was 79.1 ± 27.3 μm for uncoated versus 50.9 ± 9.6 μm for Met-Z2-Y12-coated implants (P = 0.038). At the time of explant, there were no capsular morphologic differences between the groups either grossly or per microCT.

CONCLUSIONS

Met-Z2-Y12 coating of smooth silicone breast implants significantly reduces capsule thickness in a rodent model of submuscular breast reconstruction with delayed radiotherapy.

An Antifibrotic Breast Implant Surface Coating Significantly Reduces Periprosthetic Capsule Formation

BACKGROUND

The body responds to prosthetic materials with an inflammatory foreign body response and deposition of a fibrous capsule, which may be deleterious to the function of the device and cause significant discomfort for the patient. Capsular contracture (CC) is the most common complication of aesthetic and reconstructive breast surgery. The source of significant patient morbidity, it can result in pain, suboptimal aesthetic outcomes, implant failure, and increased costs. The underlying mechanism remains unknown. Treatment is limited to reoperation and capsule excision, but recurrence rates remain high. In this study, the authors altered the surface chemistry of silicone implants with a proprietary anti-inflammatory coating to reduce capsule formation.

METHODS

Silicone implants were coated with Met-Z2-Y12, a biocompatible, anti-inflammatory surface modification. Uncoated and Met-Z2-Y12-coated implants were implanted in C57BL/6 mice. After 21, 90, or 180 days, periprosthetic tissue was removed for histologic analysis.

RESULTS

The authors compared mean capsule thickness at three time points. At 21, 90, and 180 days, there was a statistically significant reduction in capsule thickness of Met-Z2-Y12-coated implants compared with uncoated implants ( P < 0.05).

CONCLUSIONS

Coating the surface of silicone implants with Met-Z2-Y12 significantly reduced acute and chronic capsule formation in a mouse model for implant-based breast augmentation and reconstruction. As capsule formation obligatorily precedes CC, these results suggest contracture itself may be significantly attenuated. Furthermore, as periprosthetic capsule formation is a complication without anatomical boundaries, this chemistry may have additional applications beyond breast implants, to a myriad of other implantable medical devices.

CLINICAL RELEVANCE STATEMENT

Coating of the silicone implant surface with Met-Z2-Y12 alters the periprosthetic capsule architecture and significantly reduces capsule thickness for at least 6 months postoperatively in a murine model. This is a promising step forward in the development of a therapy to prevent capsular contracture.

Long-Term Maintenance of Projection of Nipples Reconstructed Using Three-Dimensionally Printed Poly-4-Hydroxybutyrate Bioabsorbable Scaffolds

BACKGROUND

For patients who are unable to undergo nipple-sparing mastectomy, reconstruction of the nipple-areola complex has been shown to promote greater satisfaction in cosmetic outcome, body image, and sexual relationships. Although a variety of techniques have been developed to optimize the shape, size, and mechanical properties of the reconstructed nipple-areola complex, maintenance of sustained nipple projection over time remains a challenge for plastic surgeons.

METHODS

Three-dimensionally printed poly-4-hydroxybutyrate (P4HB) scaffolds were designed and fabricated filled with either mechanically minced or zested patient-derived costal cartilage, designed with an internal P4HB lattice (rebar) to provide interior structure to foster tissue ingrowth, or left unfilled. All scaffolds were wrapped within a C-V flap on the dorsa of a nude rat.

RESULTS

One year after implantation, neonipple projection and diameter were well preserved in all scaffolded groups compared with nonscaffolded neonipples ( P < 0.05). Histologic analysis showed significant vascularized connective tissue ingrowth at 12 months in both empty and rebar-scaffolded neonipples and fibrovascular cartilaginous tissue formation in mechanically processed costal cartilage-filled neonipples. The internal lattice promoted more rapid tissue infiltration and scaffold degradation and best mimicked the elastic modulus of the native human nipple after 1 year in vivo. No scaffolds extruded or caused any mechanical complications.

CONCLUSIONS

Three-dimensionally printed biodegradable P4HB scaffolds maintain diameter and projection while approximating the histologic appearance and mechanical properties of native human nipples after 1 year with a minimal complication profile. These long-term preclinical data suggest that P4HB scaffolds may be readily translated for clinical application.

CLINICAL RELEVANCE STATEMENT

The authors' unique, three-dimensionally printed P4HB scaffolds can be used to create custom nipple scaffolds that contour to any nipple shape and size, enabling the fabrication of tissue-engineered neonipples with significantly greater projection maintenance and closely approximating desired nipple biomechanical properties.

Successful reconstruction of full-thickness skin defects in a swine model using simultaneous split-thickness skin grafting and composite collagen microstructured dermal scaffolds

Reconstitution of normal skin anatomy after full-thickness skin loss may be accomplished using a combination of a dermal regeneration template (DRT) and a split thickness skin graft (STSG). However, because of the relatively low rate of cell infiltration and vascularisation of currently available DRTs, reconstruction is almost always performed in a two-step procedure over the course of several weeks, resulting in multiple dressing changes, prolonged immobilisation and increased chance of infection. To mitigate the potential complications of this prolonged process, the collagen-based dermal template DermiSphere™ was developed and tested in a single-step procedure wherein DermiSphere and STSG were implanted simultaneously. When evaluated in a porcine, full thickness, excisional wound model, DermiSphere successfully supported simultaneous split thickness skin graft take and induced functional neodermal tissue deposition. When compared to a market leading product Integra Bilayer Wound Matrix, which was used in a multistep procedure (STSG placed 14 days after product implantation according to the product IFU), DermiSphere induced a similar moderate and transient inflammatory response that produced similar neodermal tissue maturity, thickness and vascularity, despite being implanted in a single surgical procedure leading to wound closure 2 weeks earlier. These data suggest that DermiSphere may be implanted in a single-step procedure with an STSG, which would significantly shorten the time course required for the reconstruction of both dermal and epidermal components of skin after full thickness loss.

Sourcing and development of tissue for transplantation in reconstructive surgery: A narrative review

The wealth of allogeneic and xenogeneic tissue products available to plastic and reconstructive surgeons has allowed for the development of novel surgical solutions to challenging clinical problems, often obviating the need to inflict donor site morbidity. Allogeneic tissue used for reconstructive surgery enters the tissue industry through whole body donation or reproductive tissue donation and has been regulated by the FDA as human cells, tissues, and cellular and tissue-based products (HCT/Ps) since 1997. Tissue banks offering allogeneic tissue can also undergo voluntary regulation by the American Association of Tissue Banks (AATB). Tissue prepared for transplantation is sterilized and can be processed into soft tissue or bone allografts for use in surgical reconstruction, whereas non-transplant tissue is prepared for clinical training and drug, medical device, and translational research. Xenogeneic tissue, which is most often derived from porcine or bovine sources, is also commercially available and is subject to strict regulations for animal breeding and screening for infectious diseases. Although xenogeneic products have historically been decellularized for use as non-immunogenic tissue products, recent advances in gene editing have opened the door to xenograft organ transplants into human patients. Herein, we describe an overview of the modern sourcing, regulation, processing, and applications of tissue products relevant to the field of plastic and reconstructive surgery.

Obesity promotes breast epithelium DNA damage in women carrying a germline mutation in BRCA1 or BRCA2

Obesity, defined as a body mass index (BMI) ≥ 30, is an established risk factor for breast cancer among women in the general population after menopause. Whether elevated BMI is a risk factor for women with a germline mutation in BRCA1 or BRCA2 is less clear because of inconsistent findings from epidemiological studies and a lack of mechanistic studies in this population. Here, we show that DNA damage in normal breast epithelia of women carrying a BRCA mutation is positively correlated with BMI and with biomarkers of metabolic dysfunction. In addition, RNA sequencing showed obesity-associated alterations to the breast adipose microenvironment of BRCA mutation carriers, including activation of estrogen biosynthesis, which affected neighboring breast epithelial cells. In breast tissue explants cultured from women carrying a BRCA mutation, we found that blockade of estrogen biosynthesis or estrogen receptor activity decreased DNA damage. Additional obesity-associated factors, including leptin and insulin, increased DNA damage in human BRCA heterozygous epithelial cells, and inhibiting the signaling of these factors with a leptin-neutralizing antibody or PI3K inhibitor, respectively, decreased DNA damage. Furthermore, we show that increased adiposity was associated with mammary gland DNA damage and increased penetrance of mammary tumors in Brca1+/- mice. Overall, our results provide mechanistic evidence in support of a link between elevated BMI and breast cancer development in BRCA mutation carriers. This suggests that maintaining a lower body weight or pharmacologically targeting estrogen or metabolic dysfunction may reduce the risk of breast cancer in this population.

Breast adipose tissue-derived extracellular vesicles from women with obesity stimulate mitochondrial-induced dysregulated tumor cell metabolism

Breast adipose tissue is an important contributor to the obesity-breast cancer link. Dysregulated cell metabolism is now an accepted hallmark of cancer. Extracellular vesicles (EVs) are nanosized particles containing selective cargo, such as miRNAs, that act locally or circulate to distant sites to modulate target cell functions. Here, we found that long-term education of breast cancer cells (MCF7, T47D) with EVs from breast adipose tissue of women who are overweight or obese (O-EVs) leads to sustained increased proliferative potential. RNA-Seq of O-EV-educated cells demonstrates increased expression of genes, such as ATP synthase and NADH: ubiquinone oxidoreductase, involved in oxidative phosphorylation. O-EVs increase respiratory complex protein expression, mitochondrial density, and mitochondrial respiration in tumor cells. Mitochondrial complex I inhibitor, metformin, reverses O-EV-induced cell proliferation. Several miRNAs, miR-155-5p, miR-10a-3p, and miR-30a-3p, which promote mitochondrial respiration and proliferation, are enriched in O-EVs relative to EVs from lean women. O-EV-induced proliferation and mitochondrial activity are associated with stimulation of the Akt/mTOR/P70S6K pathway, and are reversed upon silencing of P70S6K. This study reveals a new facet of the obesity-breast cancer link with human breast adipose tissue-derived EVs causing the metabolic reprogramming of ER+ breast cancer cells.

Accelerated vascularization of a novel collagen hydrogel dermal template

Full thickness skin loss is a debilitating problem, most commonly reconstructed using split thickness skin grafts (STSG), which do not reconstitute normal skin thickness and often result in suboptimal functional and esthetic outcomes that diminish a patient's quality of life. To address the minimal dermis present in most STSG, engineered dermal templates were developed that can induce tissue ingrowth and the formation of neodermal tissue. However, clinically available dermal templates have many shortcomings including a relatively slow rate and degree of neovascularization (∼2-4 weeks), resulting in multiple dressing changes, prolonged immobilization, and susceptibility to infection. Presented herein is a novel composite hydrogel scaffold that optimizes a unique scaffold microarchitecture with native hydrogel properties and mechanical cues ideal for promoting neovascularization, tissue regeneration, and wound healing. In vitro analysis demonstrated the unique combination of improved mechanical attributes with native hydrogel properties that promotes cell invasion and remodeling within the scaffold. In a novel 2-stage rat model of full thickness skin loss that closely mimics clinical practice, the composite hydrogel induced rapid cell infiltration and neovascularization, creating a healthy neodermis after only 1 week onto which a skin graft could be placed. The scaffold also elicited a gradual and favorable immune response, resulting in more efficient integration into the host. We have developed a dermal scaffold that utilizes simple but unique collagen hydrogel architectural cues that rapidly induces the formation of stable, functional neodermal tissue, which holds tremendous promise for the treatment of full thickness skin loss.

Perfuse and Reuse: A Low-Cost Three-Dimensional-Printed Perfusion Bioreactor for Tissue Engineering

This article describes fabrication of a customizable bioreactor, which comprises a perfusion system and coverslip-based tissue culture chamber that allow centimeter-scale vascularized or otherwise canalized tissue constructs to be maintained in weeks long static and/or perfusion culture at an exceptionally low cost, with intermittent live imaging and media sampling capabilities. The perfusion system includes a reusable polydimethylsiloxane (PDMS) lid generated from a three-dimensional (3D)-printed poly-lactic acid (PLA) mold and several lengths of perfusion tubing. The coverslip tissue culture chamber includes PDMS components built with 3D-printed PLA molds, as well as 3D-printed PLA frames and glass coverslips that house perfusable hydrogel constructs. As proof of concept, we fabricated a vascularized hydrogel construct, which was subjected to static and perfusion tissue culture, as well as flow studies using fluorescent beads and widefield fluorescent microscopy. This system can be readily reproduced, promoting the advancement of tissue engineering and regenerative medicine research.

Improving Fat Transplantation Survival and Vascularization with Adenovirus E4+ Endothelial Cell-Assisted Lipotransfer

Autologous fat transplantation is plagued by an unpredictable and often significant degree of graft loss. AdE4+ endothelial cells (ECs) are human endothelial cells that have been transduced with the E4ORF1 region of human adenovirus type 5, resulting in long-term preservation of EC proliferation and angiogenic capability without immortalization. We hypothesized that AdE4+ EC-enriched fat grafts would demonstrate improved volume retention secondary to enhanced angiogenesis. Three experimental groups were prepared by admixing 400 µL of patient lipoaspirate with 100 µL of AdE4+ EC suspensions (high AdE4+ EC concentration-enriched [5 × 106/mL], low AdE4+ EC concentration-enriched [1.25 × 106/mL], or PBS) and injected subcutaneously into the bilateral dorsa of nude mice. Fat transplants were explanted at 90 and 180 days for volumetric and histologic analyses. After both 90 and 180 days, AdE4+ EC-enriched fat grafts showed greater mean volume preservation compared to control grafts (p < 0.05). Regions of focal necrosis were only noticed in low AdE4+ EC concentration-enriched and control groups after 180 days. Histologic analysis demonstrated the presence of healthy adipocytes in all AdE4+ EC-enriched fat grafts in which both human and host ECs were evident after 90 and 180 days. AdE4+ EC enrichment improved fat graft volume preservation and vascularization in this murine xenograft model. Though further study is warranted, AdE4+ ECs demonstrated to be promising as a potential off-the-shelf adjunct for improving the volume, quality, and consistency of fat engraftment.

Off-the-Shelf Nipple Engineering: Neonipple Formation via Implantation of Scaffolded Decellularized Ovine Xenograft

BACKGROUND

Nipple reconstruction is widely regarded as the final step in postmastectomy breast reconstruction. While grafts, local flaps, or combination approaches have been used in nipple reconstruction, none has been able to achieve reliable long-term projection preservation. In response, we have sought to bioengineer neonipples in situ via the implantation of processed, decellularized cartilage xenografts placed within 3-dimensional-printed polylactic acid (PLA) scaffolds.

MATERIALS AND METHODS

External nipple scaffolds were designed in-house and 3-dimensional-printed with PLA filament. Decellularized ovine xenograft infill was prepared and processed by mincing or zesting. All nipple scaffolds were placed subcutaneously on the dorsa of Sprague-Dawley rats and explanted after 1, 3, and 6 months for analysis.

RESULTS

Explanted nipple scaffolds demonstrated gross maintenance of scaffold shape, diameter, and projection with accompanying increases in tissue volume. Histologic analyses revealed preservation of native cartilage architecture after 6 months without evidence of degradation. Analysis of formed tissue within the scaffolds revealed a progressive invasion of fibrovascular tissue with identifiable vascular channels and adipose tissue after 6 months in vivo. Confined compression testing revealed equilibrium moduli of both minced and zested samples that were within the expected range of previously reported human nipple tissue, while these data revealed no differences in the mechanical properties of the neotissue between time points or processing techniques.

CONCLUSIONS

These preliminary data support potential use of decellularized allograft to foster healthy tissue ingrowth within a PLA scaffold, thereby offering a novel solution to current limitations in nipple reconstruction.

Production of a Low-Cost, Off-the-Shelf, Decellularized Cartilage Xenograft for Tissue Regeneration

BACKGROUND

Reconstruction of cartilaginous deformities is a well-established surgical challenge with high levels of unpredictability and complication. Because of the morbidity associated with autologous cartilage grafting, combined with its limited supply and the significant expense of commercially decellularized allografts, increasing efforts have sought to produce an acellular, nonimmunogenic cartilage xenograft. We have developed and validated a novel protocol for high throughput decellularization of ovine costal cartilage with immediate translational potential for preclinical investigation of novel strategies for cartilaginous reconstruction.

METHODS

Floating ribs were isolated from freshly slaughtered rack of lamb and after cleaning, the ribs were either minced into 2-mm cubes or zested into 1-mm flakes. Tissue was then decellularized via a protocol consisting of 4 freeze/thaw cycles, digestion with trypsin, incubation in hyperosmolar and hypoosmolar salt solutions, with incubation in 1% Tween following both the hyperosmolar and hypoosmolar steps, a 48-hour incubation in nucleases, DNA elution via EDTA, and 2 terminal sterilization steps. Protocol success was evaluated via histologic analysis with hematoxylin and eosin, DAPI, and safranin-O staining, as well as DNA quantification.

RESULTS

Histologic analysis of the decellularized tissue revealed a significant reduction in nuclei as evidenced by hematoxylin and eosin and DAPI staining (P < 0.01). Safranin-O staining demonstrated a depletion of glycosaminoglycan content in the decellularized cartilage but with preservation of tissue architecture. Unprocessed lamb cartilage contained 421 ± 60 ng DNA/mg of lyophilized tissue, whereas decellularized zested and minced costal cartilage contained 27 ± 2 ng DNA/mg lyophilized tissue (P < 0.0001) and 24 ± 2.3 ng DNA/mg lyophilized tissue (p < 0.0001), respectively, well below the threshold of 50 ng accepted as evidence of suitable decellularization. In comparison, commercial allograft cartilage contained 17 ± 5 ng DNA/mg of lyophilized tissue.

CONCLUSIONS

We have developed a novel protocol for the decellularization of xenogeneic cartilage graft. This structurally stable, low immunogenicity decellularized cartilage can be produced at low cost in large quantities for use in preclinical investigation.

3D-printed poly-4-hydroxybutyrate bioabsorbable scaffolds for nipple reconstruction

Nearly all autologous tissue techniques and engineered tissue substitutes utilized for nipple reconstruction are hindered by scar contracture and loss of projection of the reconstructed nipple. The use of unprocessed costal cartilage (CC) as an internal support for the reconstructed nipple has not been widely adopted because of the excessively firm resultant construct. Herein we use a 3D-printed Poly-4-Hydroxybutyrate (P4HB) bioabsorbable scaffold filled with mechanically processed patient-derived CC to foster ingrowth of tissue in vivo to protect the regenerated tissue from contractile forces as it matures. After 6 months in vivo, newly formed spongy fibrovascular cartilaginous tissue was noted in processed CC filled 3D-printed scaffolds, which maintained significantly greater projection than reconstructions without scaffolds. Interestingly, 3D-printed P4HB scaffolds designed with an internal 3D lattice of P4HB filaments (without CC) displayed the fastest material absorption and vascularized adipose-fibrous tissue as demonstrated by SEM and histological analysis, respectively. Using 3D-printed P4HB scaffolds filled with either processed CC, a 3D P4HB lattice or no fills, we have engineered neo-nipples that maintain projection over time, while approximating the biomechanical properties of the native human nipple. We believe that this innovative 3D-printed P4HB nipple reconstruction scaffold will be readily translatable to the clinic. STATEMENT OF SIGNIFICANCE: Nearly all autologous tissue techniques and engineered tissue substitutes utilized for nipple reconstruction are hindered by scar contracture and substantial loss of projection of the reconstructed nipple, leading to significant patient dissatisfaction. Using 3D-printed P4HB scaffolds filled with either processed costal cartilage or 3D P4HB lattices, we have engineered neo-nipples that resist the forces induced by scar contracture, resulting in maintenance of neo-nipple projection over time and biomechanically approximating human nipples after 6 months in vivo implantation. This novel 3D-printed bioabsorbable P4HB scaffold will be readily translatable to the clinic to reconstruct nipples with patient-specific dimensions and long-lasting projection.

Abstract P2-06-03: Obesity is associated with DNA damage in the breast epithelium of BRCA1 and BRCA2 mutation carriers: A role for estrogens & strategies for prevention

Background: Elevated bodyweight is a risk factor for breast cancer development in women who carry a mutation in the DNA repair enzymes BRCA1 and BRCA2. However, the mechanistic basis for this association is unknown. Breast adipose tissue undergoes significant changes in the setting of weight gain and obesity, including elevation in aromatase expression which leads to the increased biosynthesis of estrogens. Given that estrogens and estrogen metabolites have known pro-proliferative and genotoxic effects, we hypothesized that in BRCA1/2 mutation carriers, obesity may be positively associated with breast epithelial cell DNA damage, thereby increasing the risk of tumorigenesis. Furthermore, we examined the impact of inhibiting estrogen signaling or production on breast epithelium DNA damage in BRCA1/2 mutation carriers. Methods: Tissue microarrays were generated from non-cancerous breast tissue derived from 72 women carrying a mutation in BRCA1 or BRCA2 with known body mass index (BMI, kg/m2). Breast epithelium DNA damage was quantified by immunofluorescence (IF) staining of the DNA damage marker γH2AX. RNA-Seq was performed on breast organoids to assess differences in gene expression in relation to BMI. Associations between DNA damage and biomarkers of estrogen biosynthesis and bioavailability, including aromatase expression in the breast and circulating steroid hormone binding globulin (SHBG), were also evaluated. To explore the effect of blocking estrogen signaling or production on DNA damage, non-tumorous breast tissue explants from BRCA1/2 mutation carriers were cultured with fulvestrant, an estrogen receptor degrader, or metformin, an anti-diabetic drug that also reduces aromatase expression in the breast. Breast epithelial cell DNA damage was measured in control vs treated explants by γH2AX IF staining after 24 hours of treatment. Results: BMI was positively correlated with DNA damage in the breast epithelium of BRCA1/2 mutation carriers. Upstream analysis of gene expression in organoids derived from women with a BMI ≥ 30 compared to &lt;25, revealed activation of estrogen signaling. Further supporting a contribution of locally-derived and circulating estrogens to obesity-related DNA damage, breast aromatase expression was found to be positively correlated with DNA damage while circulating SHBG levels showed a negative correlation. Targeting estrogen signaling with fulvestrant significantly reduced breast epithelium DNA damage in breast explants from women carrying a mutation in either BRCA1 or BRCA2. Interestingly, metformin, also caused a significant reduction in DNA damage in breast explants. Conclusion: These data provide mechanistic evidence for the link between obesity and breast cancer in BRCA1 and BRCA2 mutation carriers through identification of a positive association between BMI and breast epithelial cell DNA damage. Importantly, these studies demonstrate that fulvestrant and metformin, drugs already approved for clinical use, decrease breast epithelial cell DNA damage. Further studies are warranted to determine whether targeting estrogens or use of metformin may be effective risk reduction strategies in BRCA1/2 mutation carriers with excess bodyweight who are at high risk for breast cancer development and currently have limited options for prevention beyond surgical intervention. Support: NIH R01CA215797, NIH F31CA236306, Anne Moore Breast Cancer Research Fund

Citation Format: Priya Bhardwaj, Neil M. Iyengar, Sofya Oshchepkova, Phoebe Piloco, Rohan Bareja, Olivier Elemento, Dilip D. Giri, Michael Pollak, Monica Morrow, Jason A. Spector, Kristy A. Brown. Obesity is associated with DNA damage in the breast epithelium of BRCA1 and BRCA2 mutation carriers: A role for estrogens & strategies for prevention [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-06-03.

Abstract P5-05-02: Extracellular vesicles from obese human breast adipose tissue promote breast cancer cell proliferation by increasing mitochondrial mass and stimulating mitochondrial respiration

Background: Obesity is associated with increased breast cancer incidence and progression. Breast adipose tissue produces a number of factors hypothesized to contribute to this observation, including estrogens, adipokines, inflammatory mediators, and free fatty acids. Adipose tissue also releases extracellular vesicles (EVs) that can act locally or circulate to distant sites. EVs are nano-sized particles that are characterized by their lipid bilayer and contain nucleic acids, proteins, lipids and other molecules that can affect target cells. Recently, EVs derived from adipose tissue have received increasing attention and numerous studies have been conducted to explore the relationship between adipose tissue-derived EVs and different types of cancers, including breast cancer. Here, we provide novel insights into the sustained effects of EVs, collected from fresh breast adipose tissue, via effects on mitochondrial mass and respiration in estrogen receptor (ER)-positive breast cancer cells. Methods: EVs were collected from fresh breast adipose tissue from reduction mammoplasties. Long-term education was performed by treating MCF7 and T47D breast cancer cell lines with 3 doses of EVs over the course of 7 days. xCelligence was used to quantify cell proliferation. RNA Seq was performed on one of the educated MCF7 pairs. Mitochondrial respiration was evaluated using the Seahorse XF instrument. MitoTracker Green fluorescent staining and transmission electron microscopy (TEM) were used to assess mitochondrial density and morphology. Western blotting was used to identify pathways that may be involved in the effects of adipose tissue derived EVs on breast cancer cells. Results: EVs derived from adipose tissue of overweight/obese individuals (O-EVs) stimulate proliferation of MCF7 breast cancer cells compared with that from lean individuals (L-EVs). Compared with controls, O-EVs also induce proliferation of T47D breast cancer cells. RNA-Seq data reveal that genes involved in oxidative phosphorylation (OXPHOS) are significantly upregulated in O-EV-treated MCF7 cells compared to control. Compared with control cells, basal mitochondrial respiration of O-EV-treated MCF7 cells is significantly higher than control. Metformin, which inhibits mitochondrial complex I and ATP synthase, inhibits the O-EV-stimulated proliferation of MCF7 cells, while having no effect on the proliferation of control cells. Both MitoTracker Green fluorescent staining and TEM demonstrate increased mitochondrial mass/number. Western blotting reveals that O-EVs significantly increase phosphorylation of Akt, which is the major upstream regulator of mTOR signaling, and phosphorylation of P70 S6 kinase and 4EBP1, which are two main downstream effectors of mTOR signaling, affecting both protein synthesis and mitochondrial respiration. Conclusions: Breast adipose tissue EVs from overweight and obese women stimulate the proliferation of ER+ breast cancer cells by increasing mitochondrial mass and stimulating mitochondrial respiration, providing a novel mechanistic link between obesity and breast cancer. Our studies also suggest that metformin or mTOR-targeting drugs, may prove useful to break obesity-breast cancer link. Support: NIH R01CA215797, Anne Moore Breast Cancer Research Fund

Citation Format: Shuchen Liu, Alberto Benito-Martin, Phoebe Piloco, Catherine Liu, Paul Paik, Jason A Spector, Fanny A Pelissier Vatter, David Lyden, David M Otterburn, Leslie Cohen, Olivier Elemento, Rohan Bareja, Leona Cohen-Gould, Samuel Calto, Kristy A Brown. Extracellular vesicles from obese human breast adipose tissue promote breast cancer cell proliferation by increasing mitochondrial mass and stimulating mitochondrial respiration [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-05-02.

Three-Dimensional-Printed External Scaffolds Mitigate Loss of Volume and Topography in Engineered Elastic Cartilage Constructs

OBJECTIVE

A major obstacle in the clinical translation of engineered auricular scaffolds is the significant contraction and loss of topography that occur during maturation of the soft collagen-chondrocyte matrix into elastic cartilage. We hypothesized that 3-dimensional-printed, biocompatible scaffolds would "protect" maturing hydrogel constructs from contraction and loss of topography.

DESIGN

External disc-shaped and "ridged" scaffolds were designed and 3D-printed using polylactic acid (PLA). Acellular type I collagen constructs were cultured in vitro for up to 3 months. Collagen constructs seeded with bovine auricular chondrocytes (BAuCs) were prepared in 3 groups and implanted subcutaneously in vivo for 3 months: preformed discs with ("Scaffolded/S") or without ("Naked/N") an external scaffold and discs that were formed within an external scaffold via injection molding ("Injection Molded/SInj").

RESULTS

The presence of an external scaffold or use of injection molding methodology did not affect the acellular construct volume or base area loss. In vivo, the presence of an external scaffold significantly improved preservation of volume and base area at 3 months compared to the naked group (P < 0.05). Construct contraction was mitigated even further in the injection molded group, and topography of the ridged constructs was maintained with greater fidelity (P < 0.05). Histology verified the development of mature auricular cartilage in the constructs within external scaffolds after 3 months.

CONCLUSION

Custom-designed, 3D-printed, biocompatible external scaffolds significantly mitigate BAuC-seeded construct contraction and maintain complex topography. Further refinement and scaling of this approach in conjunction with construct fabrication utilizing injection molding may aid in the development of full-scale auricular scaffolds.

Plastic and reconstructive surgeons' views of a single payer health care system: Implications for patients and practice

BACKGROUND

Rising health care costs and the high number of uninsured Americans has led to the increasing popularity of a single payer alternative. While opinions of physicians at large have been studied, we present the first data examining the views of United States (U.S.) board-certified plastic surgeons on a single payer health care system and its implications for patients and practice.

METHODS

A total of 3,431 US plastic and reconstructive surgeons were sent a 25-item Qualtrics survey and responses collected from September 1 to November 1, 2019. Independent variables included surgeon sociodemographic characteristics. The association between these and a preference for a single payer was evaluated using the logistic regression.

RESULTS

There was a 11% response rate (n = 383). The majority of respondents were in private practice (64.5%). Forty-four percent believed that it is the government's responsibility to ensure care is provided for all; 34% were willing to give up income in exchange for reduced paperwork and administrative burden. Sixty-three percent would not work the same number of hours under single payer. Private practice plastic surgeons were significantly less likely to favor single payer (95% CI: 0.19 and 0.76). Among academic plastic surgeons, 24% would consider leaving if single payer were enacted and 60% would decrease the reconstructive portion of their practice.

CONCLUSIONS

Most U.S. plastic and reconstructive surgeons do not support a single payer health care system. Its enactment could have sweeping implications for plastic surgeons nationwide, among the most significant being a shift from academic to private practice with a potential reduction in patient access to complex reconstructive procedures.

Facial Masculinization from Procedures to Payment: A Review

As the demand for gender-affirming procedures continues to increase, patients and providers have a greater imperative to understand the current state of facial masculinization. Facial reconstruction for transgender women has been shown to treat gender dysphoria effectively and reduce rates of discrimination and victimization. Although facial masculinization surgery for transgender men is less common, there are multiple surgical and nonsurgical options to supplement the effect of hormone therapy on facial appearance, including but not limited to: receding the hair line, flattening the forehead, expanding the supraorbital ridge, increasing the dorsal nasal projection, squaring the jaw, and augmenting the chin. This review aims to summarize these techniques for providers who wish to inform transgender male patients about their options and discuss them in the context of patient satisfaction and availability of insurance coverage.

Nipple Engineering: Maintaining Nipple Geometry with Externally Scaffolded Processed Autologous Costal Cartilage

INTRODUCTION

Nipple reconstruction is the essential last step of breast reconstruction after total mastectomy, resulting in improved general and aesthetic satisfaction. However, most techniques are limited by secondary scar contracture and loss of neo-nipple projection leading to patient dissatisfaction. Approximately, 16,000 patients undergo autologous flap breast reconstruction annually, during which the excised costal cartilage (CC) is discarded. We propose utilizing processed CC placed within biocompatible 3D-printed external scaffolds to generate tissue cylinders that mimic the shape, size and biomechanical properties of native human nipple tissue while mitigating contracture and projection loss.

METHODS

External scaffolds were designed and then 3D-printed using polylactic acid (PLA). Patient-derived CC was processed by mincing or zesting, then packed into the scaffolds, implanted into nude rats and explanted after 3 months for volumetric, histologic and biomechanical analyses. Similar analyses were performed on native human nipple tissue and unprocessed CC.

RESULTS

After 3 months in vivo, gross analysis demonstrated significantly greater preservation of contour, projection and volume of the scaffolded nipples. Mechanical analysis demonstrated that processing of the cartilage resulted in implant equilibrium modulus values closer to that of the human nipple. Histologic analysis showed the presence of healthy and viable cartilage after 3 months in vivo, invested with fibrovascular tissue.

CONCLUSIONS

Autologous CC can be processed intraoperatively and placed within biocompatible external scaffolds to mimic the shape and biomechanical properties of the native human nipple. This allows for custom design and fabrication of individualized engineered autologous implants tailored to patient desire, without the loss of projection seen with traditional approaches.

Facilitated self-assembly of a prevascularized dermal/epidermal collagen scaffold

Introduction: Resurfacing complex full thickness wounds requires free tissue transfer which creates donor site morbidity. We describe a method to fabricate a skin flap equivalent with a hierarchical microvascular network. Materials & methods: We fabricated a flap of skin-like tissue containing a hierarchical vascular network by sacrificing Pluronic^® F127 macrofibers and interwoven microfibers within collagen encapsulating human pericytes and fibroblasts. Channels were seeded with smooth muscle and endothelial cells. Constructs were topically seeded with keratinocytes. Results: After 28 days in culture, multiphoton microscopy revealed a hierarchical interconnected network of macro- and micro-vessels; larger vessels (>100 μm) were lined with a monolayer endothelial neointima and a subendothelial smooth muscle neomedia. Neoangiogenic sprouts formed in the collagen protodermis and pericytes self-assembled around both fabricated vessels and neoangiogenic sprouts. Conclusion: We fabricated a prevascularized scaffold containing a hierarchical 3D network of interconnected macro- and microchannels within a collagen protodermis subjacent to an overlying protoepidermis with the potential for recipient microvascular anastomosis.

Obesity-associated Adipose Stromal Cells Promote Breast Cancer Invasion Through Direct Cell Contact and ECM Remodeling

Obesity increases the risk and worsens the prognosis for breast cancer due, in part, to altered adipose stromal cell (ASC) behavior. Whether ASCs from obese individuals increase migration of breast cancer cells relative to their lean counterparts, however, remains unclear. To test this connection, multicellular spheroids composed of MCF10A-derived tumor cell lines of varying malignant potential and lean or obese ASCs were embedded into collagen scaffolds mimicking the elastic moduli of interstitial breast adipose tissue. Confocal image analysis suggests that tumor cells alone migrate insignificantly under these conditions. However, direct cell-cell contact with either lean or obese ASCs enables them to migrate collectively, whereby obese ASCs activate tumor cell migration more effectively than their lean counterparts. Time-resolved optical coherence tomography (OCT) imaging suggests that obese ASCs facilitate tumor cell migration by mediating contraction of local collagen fibers. Matrix metalloproteinase (MMP)-dependent proteolytic activity significantly contributes to ASC-mediated tumor cell invasion and collagen deformation. However, ASC contractility is also important, as co-inhibition of both MMPs and contractility is necessary to completely abrogate ASC-mediated tumor cell migration. These findings imply that obesity-mediated changes of ASC phenotype may impact tumor cell migration and invasion with potential implications for breast cancer malignancy in obese patients.

Three-dimensional growth of breast cancer cells potentiates the anti-tumor effects of unacylated ghrelin and AZP-531

Breast cancer is the most common type of cancer in women and notwithstanding important therapeutic advances, remains the second leading cause of cancer-related death. Despite extensive research relating to the hormone ghrelin, responsible for the stimulation of growth hormone release and appetite, little is known of the effects of its unacylated form, especially in cancer. The present study aimed to characterize effects of unacylated ghrelin on breast cancer cells, define its mechanism of action, and explore the therapeutic potential of unacylated ghrelin or analog AZP-531. We report potent anti-tumor effects of unacylated ghrelin, dependent on cells being cultured in 3D in a biologically-relevant extracellular matrix. The mechanism of unacylated ghrelin-mediated growth inhibition involves activation of Gαi and suppression of MAPK signaling. AZP-531 also suppresses the growth of breast cancer cells in vitro and in xenografts, and may be a novel approach for the safe and effective treatment of breast cancer.

A reference single-cell transcriptomic atlas of human skeletal muscle tissue reveals bifurcated muscle stem cell populations

Single-cell RNA-sequencing (scRNA-seq) facilitates the unbiased reconstruction of multicellular tissue systems in health and disease. Here, we present a curated scRNA-seq dataset of human muscle samples from 10 adult donors with diverse anatomical locations. We integrated ~ 22,000 single-cell transcriptomes using Scanorama to account for technical and biological variation and resolved 16 distinct populations of muscle-resident cells using unsupervised clustering of the data compendium. These cell populations included muscle stem/progenitor cells (MuSCs), which bifurcated into discrete "quiescent" and "early-activated" MuSC subpopulations. Differential expression analysis identified transcriptional profiles altered in the activated MuSCs including genes associated with aging, obesity, diabetes, and impaired muscle regeneration, as well as long non-coding RNAs previously undescribed in human myogenic cells. Further, we modeled ligand-receptor cell-communication interactions and observed enrichment of the TWEAK-FN14 pathway in activated MuSCs, a characteristic signature of muscle wasting diseases. In contrast, the quiescent MuSCs have enhanced expression of the EGFR receptor, a recognized human MuSC marker. This work provides a new benchmark reference resource to examine human muscle tissue heterogeneity and identify potential targets in MuSC diversity and dysregulation in disease contexts.

Poly-4-hydroxybutyrate (Phasix™) mesh onlay in complex abdominal wall repair

BACKGROUND

Poly-4-hydroxybutyric acid (P4HB, Phasix™) is a biosynthetic polymer that degrades by hydrolysis that can be woven into a mesh for use in soft tissue reinforcement. Herein, we describe our initial experience performing complex abdominal wall repair (CAWR) utilizing component separation and P4HB mesh as onlay reinforcement.

METHODS

All patients undergoing CAWR between June 2014 and May 2017 were followed prospectively for postoperative outcomes. Only those patients who underwent components separation with primary repair of the fascial edges followed by onlay of P4HB mesh were included in this study.

RESULTS

105 patients (52 male, 53 female; mean age 59.2 years, range 22-84) met inclusion criteria. Mean BMI was 29.1 (range 16-48); 52% patients had prior attempted hernia repair, most with multiple medical comorbidities (71% of patients with ASA 3 or greater). 30% of cases were not clean at the time of repair (CDC class 2 or greater). Median follow-up was 36 months (range 9-63). Eighteen patients (17%) developed a hernia recurrence ranging from 2 to 36 months postoperatively. Five (5%) patients developed a localized superficial infection treated with antibiotics, three (2.8%) required re-operation for non-healing wounds, and six (6%) patients developed seroma.

CONCLUSIONS

These data demonstrate a relatively low rate of hernia recurrence, seroma, and other common complications of CAWR in a highly morbid patient population. Importantly, the rate of mesh infection was low and no patients required complete mesh removal, even when placed into a contaminated or infected surgical field.

The surface stress of biomedical silicones is a stimulant of cellular response

Silicones are commonly used for lubrication of syringes, encapsulation of medical devices, and fabrication of surgical implants. While silicones are generally viewed as relatively inert to the cellular milieu, they can mediate a variety of inflammatory responses and other deleterious effects, but the mechanisms underlying the bioactivity of silicones remain unresolved. Here, we report that silicone liquids and gels have high surface stresses that can strongly resist deformation at cellular length scales. Biomedical silicones, including syringe lubricants and fillings from FDA-approved breast implants, readily adsorb matrix proteins and activate canonical rigidity sensing pathways through their surface stresses. In 3D culture models, liquid silicone droplets support robust cellular adhesion and the formation of multinucleated monocyte-derived cell masses that recapitulate phenotypic aspects of granuloma formation in the foreign body response. Together, our findings implicate surface stress as a cellular stimulant that should be considered in application of silicones for biomedical purposes.

Sternal Reconstruction Using Customized 3D-Printed Titanium Implants

In this report, we describe the use of custom-designed 3D-printed titanium implants to reconstruct the anterior chest wall, including the sternum and adjacent ribs, in two patients. These cases are the first to be reported in the United States, and they are among a handful performed around the world.

Biofabrication of thick vascularized neo-pedicle flaps for reconstructive surgery

Wound chronicity due to intrinsic and extrinsic factors perturbs adequate lesion closure and reestablishment of the protective skin barrier. Immediate and proper care of chronic wounds is necessary for a swift recovery and a reduction of patient vulnerability to infection. Advanced therapies supplemented with standard wound care procedures have been clinically implemented to restore aberrant tissue; however, these treatments are ineffective if local vasculature is too compromised to support minimally-invasive strategies. Autologous "flaps", which are tissues equipped with their own hierarchical vascular supply, can be harvested from one region of the patient and transplanted to the wound where it is reperfused upon microsurgical anastomosis to appropriate recipient vessels. Despite the success of autologous flap transfer, these procedures are extremely invasive, incur obligatory donor-site morbidity, and require sufficient donor-tissue availability, microsurgical expertise, and specialized equipment. 3D-bioprinting modalities, such as extrusion-based bioprinting, can be used to address the clinical constraints of autologous flap transfer, primarily addressing donor-site morbidity and tissue availability. This advancement in regenerative medicine allows the biofabrication of heterogeneous tissue structures with high shape fidelity and spatial resolution to generate biomimetic constructs with the anatomically-precise geometries of native tissue to ensure tissue-specific function. Yet, meaningful progress toward this clinical application has been limited by the lack of vascularization required to meet the nutrient and oxygen demands of clinically relevant tissue volumes. Thus, various criteria for the fabrication of functional tissues with hierarchical, patent vasculature must be considered when implementing 3D-bioprinting technologies for deep, chronic wounds.

Microstructured hydrogel scaffolds containing differential density interfaces promote rapid cellular invasion and vascularization

INTRODUCTION

Insufficient vascularization of currently available clinical biomaterials has limited their application to optimal wound beds. We designed a hydrogel scaffold with a unique internal microstructure of differential collagen densities to induce cellular invasion and neovascularization.

METHODS

Microsphere scaffolds (MSS) were fabricated by encasing 1% (w/v) type 1 collagen microspheres 50-150 μm in diameter in 0.3% collagen bulk. 1% and 0.3% monophase collagen scaffolds and Integra® disks served as controls. Mechanical characterization as well as in vitro and in vivo invasion assays were performed. Cell number and depth of invasion were analyzed using Imaris™. Cell identity was assessed immunohistochemically.

RESULTS

In vitro, MSS exhibited significantly greater average depth of cellular invasion than Integra® and monophase collagen controls. MSS also demonstrated significantly higher cell counts than controls. In vivo, MSS revealed significantly more cellular invasion spanning the entire scaffold depth at 14 days than Integra®. CD31+ expressing luminal structures suggestive of neovasculature were seen within MSS at 7 days and were more prevalent after 14 days. Multiphoton microscopy of MSS demonstrated erythrocytes within luminal structures after 14 days.

CONCLUSION

By harnessing simple architectural cues to induce cellular migration, MSS holds great potential for clinical translation as the next generation dermal replacement product.

STATEMENT OF SIGNIFICANCE

Large skin wounds require tissue engineered dermal substitutes in order to promote healing. Currently available dermal replacement products do not always adequately incorporate into the body, especially in complex wounds, due to poor neovascularization. In this paper, we present a hydrogel with an innovative microarchitecture that is composed of dense type I collagen microspheres suspended in a less-dense collagen bulk. We show that cell invasion into the scaffold is driven solely by mechanical cues inherent within this differential density interface, and that this induces robust vascular cell invasion both in vitro and in a rodent model. Our hydrogel performs favorably compared to the current clinical gold standard, Integra®. We believe this hydrogel scaffold may be the first of the next generation of dermal replacement products.

Tissue engineering the human auricle by auricular chondrocyte-mesenchymal stem cell co-implantation

Children suffering from microtia have few options for auricular reconstruction. Tissue engineering approaches attempt to replicate the complex anatomy and structure of the ear with autologous cartilage but have been limited by access to clinically accessible cell sources. Here we present a full-scale, patient-based human ear generated by implantation of human auricular chondrocytes and human mesenchymal stem cells in a 1:1 ratio. Additional disc construct surrogates were generated with 1:0, 1:1, and 0:1 combinations of auricular chondrocytes and mesenchymal stem cells. After 3 months in vivo, monocellular auricular chondrocyte discs and 1:1 disc and ear constructs displayed bundled collagen fibers in a perichondrial layer, rich proteoglycan deposition, and elastin fiber network formation similar to native human auricular cartilage, with the protein composition and mechanical stiffness of native tissue. Full ear constructs with a 1:1 cell combination maintained gross ear structure and developed a cartilaginous appearance following implantation. These studies demonstrate the successful engineering of a patient-specific human auricle using exclusively human cell sources without extensive in vitro tissue culture prior to implantation, a critical step towards the clinical application of tissue engineering for auricular reconstruction.

Transient phase behavior of an elastomeric biomaterial applied to abdominal laparotomy closure

Secure closure of the fascial layers after entry into the peritoneal cavity is crucial to prevent incisional hernia, yet appropriate purchase of the tissue can be challenging due to the proximity of the underlying protuberant bowel which may become punctured by the surgical needle or strangulated by the suture itself. Devices currently employed to provide visceral protection during abdominal closure, such as the metal malleable retractor and Glassman Visceral Retainer, are unable to provide complete protection as they must be removed prior to complete closure. A puncture resistant, biocompatible, and degradable matrix that can be left in place without need for removal would facilitate rapid and safe abdominal closure. We describe a novel elastomer (CC-DHA) that undergoes a rapid but controlled solid-to-liquid phase transition through the application of a destabilized carbonate cross-linked network. The elastomer is comprised of a polycarbonate cross-linked network of dihydroxyacetone, glycerol ethoxylate, and tri(ethylene glycol). The ketone functionality of the dihydroxyacetone facilitates hydrolytic cleavage of the carbonate linkages resulting in a rapidly degrading barrier that can be left in situ to facilitate abdominal fascial closure. Using a murine laparotomy model we demonstrated rapid dissolution and metabolism of the elastomer without evidence of toxicity or intraabdominal scarring. Furthermore, needle puncture and mechanical properties demonstrated the material to be both compliant and sufficiently puncture resistant. These unique characteristics make the biomaterial extraordinarily useful as a physical barrier to prevent inadvertent bowel injury during fascial closure, with the potential for wider application across a variety of medical and surgical applications.

STATEMENT OF SIGNIFICANCE

Fascial closure after abdominal surgery requires delicate maneuvers to prevent incisional hernia while minimizing risk for inadvertent bowel injury. We describe a novel biocompatible and biodegradable polycarbonate elastomer (CC-DHA) comprised of dihydroxyacetone, glycerol ethoxylate, and tri(ethylene glycol), for use as a rapidly degrading protective visceral barrier to aid in abdominal closure. Rapid polymer dissolution and metabolism was demonstrated using a murine laparotomy model without evidence of toxicity or intraabdominal scarring. Furthermore, mechanical studies showed the material to be sufficiently puncture resistant and compliant. Overall, this new biomaterial is extraordinary useful as a physical barrier to prevent inadvertent bowel injury during fascial closure, with the potential for wider application across a variety of medical and surgical applications.

Optimizing cell sourcing for clinical translation of tissue engineered ears

Background . Currently, the major impediment to clinical translation of our previously described platform for the fabrication of high fidelity, patient-specific tissue engineered ears is the development of a clinically optimal cell sourcing strategy. A limited autologous auricular chondrocyte (AuC) supply in conjunction with rapid chondrocyte de-differentiation during in vitro expansion currently makes clinical translation more challenging. Mesenchymal stem cells (MSCs) offer significant promise due to their inherent chondrogenic potential, and large availability through minimally invasive procedures. Herein, we demonstrate the promise of AuC/MSC co-culture to fabricate elastic cartilage using 50% fewer AuC than standard approaches.

METHODS

Bovine auricular chondrocytes (bAuC) and bovine MSC (bMSC) were encapsulated within 10 mg ml^-1 type I collagen hydrogels in ratios of bAuC:bMSC 100:0, 50:50, and 0:100 at a density of 25 million cells ml^-1 hydrogel. One mm thick collagen sheet gels were fabricated, and thereafter, 8 mm diameter discs were extracted using a biopsy punch. Discs were implanted subcutaneously in the dorsa of nude mice (NU/NU) and harvested after 1 and 3 months.

RESULTS

Gross analysis of explanted discs revealed bAuC:bMSC co-culture discs maintained their size and shape, and exhibited native auricular cartilage-like elasticity after 1 and 3 months of implantation. Co-culture discs developed into auricular cartilage, with viable chondrocytes within lacunae, copious proteoglycan and elastic fiber deposition, and a distinct perichondrial layer. Biochemical analysis confirmed that co-culture discs deposited critical cartilage molecular components more readily than did both bAuC and bMSC discs after 1 and 3 months, and proteoglycan content significantly increased between 1 and 3 months.

CONCLUSION

We have successfully demonstrated an innovative cell sourcing strategy that facilitates our efforts to achieve clinical translation of our high fidelity, patient-specific ears for auricular reconstruction utilizing only half of the requisite auricular chondrocytes to fabricate mature elastic cartilage.