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.

Thromboembolectomy for acute lower limb ischemia: Contemporary outcomes of two surgical methods from a single tertiary center.

OBJECTIVES: The current treatment of acute lower limb ischemia (ALLI) includes open surgical and percutaneous pharmaco-mechanical thromboembolectomy (TE). We hereby report our results with open surgical TE over a 10-year period and compare our outcomes using routine fluoroscopic assisted TE (FATE) with blind and selective on demand fluoroscopic-assisted TE (BSTE). METHODS: This is a retrospective analysis of all patients who underwent open surgical TE for acute lower limb ischemia at a single tertiary center between 2008 and 2018. Patients were divided into a group who underwent BSTE and another who underwent routine FATE. Data on presentation, medical history, surgery performed, and short-term outcomes were retrieved from medical record. Comparison between baseline characteristics and outcomes of both groups were made using t-test and chi-square analysis. RESULTS: Over 10 years, 108 patients underwent surgical TE. Thirty-day mortality rate and 30-day major lower extremity amputation rate in the cohort were 12.0% and 6.5%, respectively. On subgroup analysis, 53 patients were treated by BSTE and 55 patients by FATE. There was no significant difference in 30-day mortality rate (11.3% vs 12.7%, p-value = .82) and 30-day major amputation rate (9.4% vs 3.6%, p-value = .454) between the two groups. Local anesthesia was more frequently performed in patients undergoing FATE (58.2% vs 24.5%, p-value < .001). More than one arteriotomy was more frequently required in patients undergoing BSTE (2.6% vs 45.5%, p-value < .001). Patients with infrapopliteal involvement undergoing FATE required less further interventions such as patch angioplasty (2.6% vs 36.4%, p-value < .001) and bypass (2.6% vs 22.7%, p-value = .01). CONCLUSION: ALLI remains a disease of high morbidity and mortality. Open surgical TE offers an effective approach to treat ALLI. The addition of fluoroscopy to the conduction of TE could be associated with valuable benefits, especially in patients with infra-popliteal involvement. Randomized controlled trials are needed to objectively assess the therapeutic potential of FATE.

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.

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.

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.

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.