Thioxanthone-Based Siloxane Photosensitizer for Cationic/Radical Photopolymerization and Photoinduced Sol-Gel Reactions.

In this investigation, a multifunctional visible-light TX-based photosensitizer containing a siloxane moiety (TXS) was designed with a good overall yield of 54%. The addition of a siloxane moiety enabled the incorporation of a TX photosensitizer into a siloxane network by photoinduced sol-gel chemistry, thus avoiding its release. Both liquid 1H and solid-state 29Si NMR measurements undeniably confirmed the formation of photoacids resulting from the photolysis of the TXS/electron acceptor molecule (Iodonium salt), which promoted the photoinduced hydrolysis/condensation of the trimethoxysilane groups of TXS, with a high degree of condensation of its inorganic network. Notably, the laser flash photolysis, fluorescence, and electron paramagnetic resonance spin-trapping (EPR ST) experiments demonstrated that TXS could react with Iod through an electron transfer reaction through its excited states, leading to the formation of radical initiating species. Interestingly, the TXS/Iod was demonstrated to be an efficient photoinitiating system for free-radical (FRP) and cationic (CP) polymerization under LEDs@385, 405, and 455 nm. In particular, whatever the epoxy monomer mixtures used, remarkable final epoxy conversions were achieved up to 100% under air. In this latter case, we demonstrated that both the photoinduced sol-gel process (hydrolysis of trimethoxysilane groups) and the cationic photopolymerization occurred simultaneously.

Influence of Placement of Lumbar Interbody Cage on Subsidence Risk: Biomechanical Study.

OBJECTIVE: Lumbar spinal fusion is a common surgical procedure that can be done with a variety of different instrumentation and techniques. Despite numerous research studies investigating subsidence risk factors, the impact of cage placement on subsidence is not fully elucidated. This study aims to determine whether placement of an expandable transforaminal lumbar interbody fusion cage at the center end plate or at the anterior apophyseal ring affects cage subsidence. METHODS: A transforaminal lumbar interbody fusion cage was placed centrally or peripherally between 2 synthetic vertebral models of L3 and L4. A compression plate attached to a 10 KN load cell was used to uniaxially compress the assembly. The ultimate force required for the assembly to fail and subsidence stiffness were analyzed. Computed tomography scans of each L3 and L4 were obtained, and maximum end plate subsidence was measured in the frontal plane. RESULTS: Anterior apophyseal cage placement resulted in higher stiffness of the vertebrae-cage assembly (Ks, 962.89 N/mm) and a higher subsidence stiffness (Kb,987.21 N/mm) compared with central placement (P < 0.05). Ultimate compressive load of the vertebrae-cage assembly did not increase. Moreover, the maximum subsidence depth did not significantly vary between placements. CONCLUSIONS: The subsidence stiffness increased with anterior apophyseal cage placement. Periphery end plate cortical bone architecture may play a role in resisting the impact of cage subsidence. To fully understand the effect of cage placement on cage subsidence, future studies should investigate its implications on native and diseased spine.

Effect of Amino-Functionalized Polyhedral Oligomeric Silsesquioxanes on Structure-Property Relationships of Thermostable Hybrid Cyanate Ester Resin Based Nanocomposites.

Nanocomposites of cyanate ester resin (CER) filled with three different reactive amino-functionalized polyhedral oligomeric silsesquioxane (POSS) were synthesized and characterized. The addition of a small quantity (0.1 wt.%) of amino-POSS chemically grafted to the CER network led to the increasing thermal stability of the CER matrix by 12-15 °C, depending on the type of amino-POSS. A significant increase of the glass transition temperature, Tg (DSC data), and the temperature of α relaxation, Tα (DMTA data), by 45-55 °C of the CER matrix with loading of nanofillers was evidenced. CER/POSS films exhibited a higher storage modulus than that of neat CER in the temperature range investigated. It was evidenced that CER/aminopropylisobutyl (APIB)-POSS, CER/N-phenylaminopropyl (NPAP)-POSS, and CER/aminoethyl aminopropylisobutyl (AEAPIB)-POSS nanocomposites induced a more homogenous α relaxation phenomenon with higher Tα values and an enhanced nanocomposite elastic behavior. The value of the storage modulus, E', at 25 °C increased from 2.72 GPa for the pure CER matrix to 2.99-3.24 GPa for the nanocomposites with amino-functionalized POSS nanoparticles. Furthermore, CER/amino-POSS nanocomposites possessed a higher specific surface area, gas permeability (CO2, He), and diffusion coefficients (CO2) values than those for neat CER, due to an increasing free volume of the nanocomposites studied that is very important for their gas transport properties. Permeability grew by about 2 (He) and 3.5-4 times (CO2), respectively, and the diffusion coefficient of CO2 increased approximately twice for CER/amino-POSS nanocomposites in comparison with the neat CER network. The efficiency of amino-functionalized POSS in improving the thermal and transport properties of the CER/amino-POSS nanocomposites increased in a raw of reactive POSS containing one primary (APIB-POSS) < eight secondary (NPAP-POSS) < one secondary and one primary (AEAPIB-POSS) amino groups. APIB-POSS had the least strongly pronounced effect, since it could form covalent bonds with the CER network only by a reaction of one -NH2 group, while AEAPIB-POSS displayed the most highly marked effect, since it could easily be incorporated into the CER network via a reaction of -NH2 and -NH- groups with -O-C≡N groups from CER.

Diblock and Triblock Copolymers as Nanostructured Precursors to Functional Nanoporous Materials: From Design to Application.

Block copolymers have gained tremendous interest from the scientific community in the last two decades. These macromolecular architectures indeed constitute ideal nanostructured precursors for the generation of nanoporous materials meant for various high added value applications. The parallel emergence of controlled polymerization techniques has notably enabled to finely control their molecular features to confer them with unique structural and physicochemical properties, such as low dispersity values (D), well-defined volume fractions, and controlled functionality. The nanostructuration and ordering of diblock or triblock copolymers, which can be achieved through various experimental techniques, including channel die processing, solvent vapor or thermal annealing, nonsolvent-induced phase separation or concomitant self-assembly, and nonsolvent-induced phase separation, allows for the preparation of orientated microphase-separated copolymers whose morphology is dictated by three main factors, i.e., Flory-Huggins interaction parameter between constitutive blocks, volume fraction of the blocks, and polymerization degree. This review article provides an overview of the actual state of the art regarding the preparation of functional nanoporous materials from either diblock or triblock copolymers. It will also highlight the major applications of such peculiar materials.

Exosome-Laden Scaffolds for Treatment of Post-Traumatic Cartilage Injury and Osteoarthritis of the Knee: A Systematic Review.

Mesenchymal stem cell (MSC)-based exosomes have garnered attention as a viable therapeutic for post-traumatic cartilage injury and osteoarthritis of the knee; however, efforts for application have been limited due to issues with variable dosing and rapid clearance in vivo. Scaffolds laden with MSC-based exosomes have recently been investigated as a solution to these issues. Here, we review in vivo studies and highlight key strengths and potential clinical uses of exosome-scaffold therapeutics for treatment of post-traumatic cartilage injury and osteoarthritis. In vivo animal studies were gathered using keywords related to the topic, revealing 466 studies after removal of duplicate papers. Inclusion and exclusion criteria were applied for abstract screening and full-text review. Thirteen relevant studies were identified for analysis and extraction. Three predominant scaffold subtypes were identified: hydrogels, acellular extracellular matrices, and hyaluronic acid. Each scaffold-exosome design showcased unique properties with relation to gross findings, tissue histology, biomechanics, and gene expression. All designs demonstrated a reduction in inflammation and induction of tissue regeneration. The results of our review show that current exosome-scaffold therapeutics demonstrate the capability to halt and even reverse the course of post-traumatic cartilage injury and osteoarthritis. While this treatment modality shows incredible promise, future research should aim to characterize long-term biocompatibility and optimize scaffold designs for human treatment.

Synthesis of Thioureas, Thioamides, and Aza-Heterocycles via Dimethyl-Sulfoxide-Promoted Oxidative Condensation of Sulfur, Malonic Acids, and Amines.

Malonic acid and derivatives have been well-known to undergo monodecarboxylation under relatively mild conditions and have been exclusively used as a C2 synthon. We report herein their new application as a C1 synthon via double decarboxylation promoted by sulfur and dimethyl sulfoxide. In the presence of amines as nucleophiles, a wide range of thioureas and thioamides as well as N-heterocycles were obtained in good to excellent yields under mild heating conditions.

External Stenting (Exostenting) to Correct Vascular Torsion and Angulation.

Organ transplantation can be associated with vascular torsions and angulations of both recipient and donor vessels. Such kinks and/or torsions of vessels can compromise the vascular integrity, obstruct inflow and/or outflow, and result in loss of the organ and/or body parts. On many occasions, mild angulations and torsions can be successfully addressed by repositioning the organ. In cases where the abnormal findings persist, maneuvers such as placing a fat pad to create a smoother curve, or even opening the peritoneum (in the case of kidney transplants) to allow for a better positioning of the organ, are associated with successful outcomes. When such torsions/angulations persist despite these approaches, further innovative tactics are required. In the current report, we propose a technique that involves longitudinally opening of a synthetic graft that is rigid enough to maintain its shape, such as a ringed polytetrafluoroethylene graft, and placing it as an external stent around the angulated/torsioned vessel. This maneuver will correct the underlying vascular compromise without having to perform any further invasive interventions, such as reimplanting the organ or resecting part of the involved vessel. Although primarily illustrated for application by describing an instance in which exostenting was applied during kidney transplantation, our approach could be applied to any vessel under many circumstances where angulations/twists are encountered. In this report, we describe the use of an external stent, also called exostenting, to correct a severe torsion/angulation of the external iliac artery in a kidney transplant recipient where all other measures were unsuccessful.

Primary Ear Reconstruction Using Cadaveric Costal Cartilage.

OBJECTIVE: Allogeneic cadaveric costal cartilage is commonly used for grafts in nasal reconstruction surgery; however, limited information exists on its use in total ear reconstruction for microtia. In this case series, we describe the novel use of cadaveric cartilage for auricular framework construction in ear reconstruction and review preliminary histologic findings. METHODS: Patients requiring primary complete reconstruction of the auricle from August 2020 to December 2021 were eligible and underwent ear reconstruction using cadaveric costal cartilage. Patients were evaluated for surgical site infection, skin necrosis, cartilage resorption, and cartilage exposure during regular follow-up visits. Two cartilage samples were taken after 2 separate second-stage surgeries done 52 weeks after first-stage reconstruction. These samples were stained with hematoxylin and eosin as well as safranin-O and examined under light microscopy. RESULTS: A total of 12 ear reconstruction procedures using cadaveric costal cartilage were performed across 11 patients; 10 of 12 ears had type III microtia and 2 of 12 ears had type IV microtia. Patients ranged from 4 to 25 years old at the time of surgery, with an average age of 10.7 years. Follow-up time ranged from 1.6 to 25.4 months, with a mean follow-up time of 11.2 months. No patients experienced any visibly significant cartilage warping. Two patients experienced minor construct exposure, which were successfully salvaged. Two patients experienced surgical site infections, one lead to resorption requiring framework replacement. Preliminary histologic analysis of the 2 samples taken 1 year after implantation showed viable chondrocytes with no evidence of immunologic rejection or any local inflammation or host foreign body response. CONCLUSIONS: Cadaveric costal cartilage serves as a viable alternative to autologous cartilage and other alloplastic biomaterials for construction of auricular frameworks in primary microtia reconstruction. Resorption secondary to infection and construct exposure remain potential risks. Longer follow-up times and a larger sample size are needed for assessment of long-term efficacy.

Tendon Transection Healing Can Be Improved With Adipose-Derived Stem Cells Cultured With Growth Differentiation Factor 5 and Platelet-Derived Growth Factor.

BACKGROUND: As hand surgeons, tendon injuries and lacerations are a particularly difficult problem to treat, as poor healing potential and adhesions hamper optimal recovery. Adipose-derived stem cells (ADSCs) have been shown to aid in rat Achilles tendon healing after a puncture defect, and this model can be used to study tendon healing in the upper extremity. We hypothesized that ADSCs cultured with growth differentiation factor 5 (GDF5) and platelet-derived growth factor (PDGF) would improve tendon healing after a transection injury. METHODS: Rat Achilles tendons were transected and then left either unrepaired or repaired. Both groups were treated with a hydrogel alone, a hydrogel with ADSCs, or a hydrogel with ADSCs that were cultured with GDF5 and PDGF prior to implantation. Tissue harvested from the tendons was evaluated for gene expression of several genes known to play an important role in successful tendon healing. Histological examination of the tendon healing was also performed. RESULTS: In both repaired and unrepaired tendons, those treated with ADSCs cultured with GDF5/PDGF prior to implantation showed the best tendon fiber organization, the smallest gaps, and the most organized blood vessels. Treatment with GDF5/PDGF increased expression of the protenogenesis gene SOX9, promoted cell-to-cell connections, improved cellular proliferation, and enhanced tissue remodeling. CONCLUSIONS: Adipose-derived stem cells cultured with GDF5/PDGF prior to implantation can promote tendon repair by improving cellular proliferation, tenogenesis, and vascular infiltration. This effect results in a greater degree of organized tendon healing.

Effects of Premixing Betamethasone and Lidocaine on Chondrocyte Inflammation in an In Vitro Model.

BACKGROUND: It is common practice for hand surgeons to premix corticosteroids with a local anesthetic and store the mixture in pre-loaded syringes for rapid use during clinic. However, any possible loss of efficacy with this practice has never been studied. The purpose of this study, therefore, is to determine whether premixing betamethasone sodium phosphate/betamethasone acetate (BSP) and lidocaine (L) at different time intervals from injection has diminishing anti-inflammatory effects on chondrocytes in vitro. METHODS: Human articular chondrocytes were partitioned into six groups: two controls and four experimental conditions. The negative control had growth media only. The positive control had growth media and inflammatory cytokines (interleukin-1ß and oncostatin M). Experimental conditions were additionally treated with BSP alone or BSP mixed with lidocaine (BSP + L) at the time of treatment (0 hours), or at 4 or 24 hours prior. Relative expressions of inflammatory genes were measured. RESULTS: Relative to the positive control, chondrocytes in all experimental conditions decreased expression of TNF-α, MMP-3, and ADAMTS-4. Chondrocytes exposed to BSP only or BSP + L at 4 hours or 24 hours prior to treatment decreased expression of IL-8. Chondrocytes exposed to BSP only or BSP + L at 0 hours or 4 hours prior to treatment decreased expression of MMP-1. There were no significant differences in expression of IL-6 or MMP-13. CONCLUSIONS: Treatment with BSP + L prepared in pre-loaded syringes at varying time intervals up to 24 hours prior to injection does not significantly impact the ability of the mixture to reduce expression of certain key inflammatory mediators in vitro.

The Effects of Autologous Fat Transfer in an In Vitro Model of Basal Joint Osteoarthritis.

PURPOSE: Basal joint osteoarthritis (OA) is a highly prevalent and debilitating condition. Recent clinical evidence suggests that autologous fat transfer (AFT) may be a promising, minimally invasive treatment for this condition. However, the mechanism of action is not fully understood. It is theorized that AFT reduces inflammation in the joint, functions to regenerate cartilage, or acts as a mechanical buffer. The purpose of this study was to better understand the underlying mechanism of AFT using an in vitro model. We hypothesize that the addition of stromal vascular fraction (SVF) cells will cause a reduction in markers of inflammation. METHODS: Articular chondrocytes were expanded in culture. Liposuction samples were collected from human subjects and processed similarly to AFT protocols to isolate SVF rich in adipose-derived stem cells. A control group was treated with standard growth media, and a positive control group (OA group) was treated with inflammatory cytokines. To mimic AFT, experimental groups received inflammatory cytokines and either a low or high dose of SVF. Expression of relevant genes was measured, including interleukin (IL)-1ß, IL-1 receptor antagonist, and matrix metalloproteinases (MMP). RESULTS: Compared to the OA group, significant decreases in IL-1ß, MMP3, and MMP13 expression on treatment day 3 were found in the high-dose SVF group, while MMP13 expression was also significantly decreased in the low-dose SVF group on day 3. CONCLUSIONS: In this study, we found that SVF treatment reduced expression of IL-1ß, MMP3, and MMP13 in an in vitro model of OA. These results suggest that an anti-inflammatory mechanism may be responsible for the clinical effects seen with AFT in the treatment of basal joint OA. CLINICAL RELEVANCE: An anti-inflammatory mechanism may be responsible for the clinical benefits seen with AFT for basal joint arthritis.

An Ex Vivo Model of Posterior Tracheomalacia With Evaluation of Potential Treatment Modalities.

OBJECTIVE: Posterior tracheomalacia (TM) is characterized by excessive intraluminal displacement of the tracheal membranous wall. Recently, novel surgical strategies for repair of posterior TM have been introduced. To our knowledge, these strategies have not been evaluated in a model of posterior TM. Thus, we sought to design an ex vivo mechanical model of posterior TM to evaluate potential repair interventions. METHODS: A model for posterior TM was created with partial thickness longitudinal incisions to the posterior aspect of ex vivo porcine trachea. Three groups of tracheas were tested: (1) control (unmanipulated), (2) posterior TM (injury), and (3) intervention (repair). Interventions included external splinting with 0.3 and 0.5 mm bioresorbable plates, posterior tracheopexy, and injection tracheoplasty with calcium hydroxylapatite. An airtight tracheal system was created to measure tracheal wall collapse with changes in negative pressure. A bronchoscope and pressure transducer were connected to either end. Cross-sectional area of the tracheal lumen was analyzed using ImageJ software (National Institutes of Health, Bethesda, MD). RESULTS: Average percent reduction in cross-sectional area of the tracheal lumen was compared using a two-tailed paired t-test. Significant differences were found between control and TM groups (p < 0.019). There was no significant difference between control and external splinting and posterior tracheopexy groups (p > 0.14). CONCLUSION: We describe an ex vivo model for posterior TM that replicates airway collapse. External splinting and tracheopexy interventions showed recovery of the injured tracheal segment. Injection tracheoplasty did not improve the TM. LEVEL OF EVIDENCE: N/A Laryngoscope, 133:2000-2006, 2023.

Regulatory and Ethical Aspects of Orthobiologic Therapies.

Orthobiologic therapies show significant promise to improve outcomes for patients with musculoskeletal pathology. There are considerable research efforts to develop strategies that seek to modulate the biological environment to promote tissue regeneration and healing and/or provide symptomatic relief. However, the regulatory pathways overseeing the clinical translation of these therapies are complex, with considerable worldwide variation. The introduction of novel biologic treatments into clinical practice raises several ethical dilemmas. In this review, we describe the process for seeking approval for biologic therapies in the United States, Europe, and Japan. We highlight a number of ethical issues raised by the clinical translation of these treatments, including the design of clinical trials, monitoring outcomes, biobanking, "off-label" use, engagement with the public, marketing of unproven therapies, and scientific integrity.

Metallic Nanoparticles Adsorbed at the Pore Surface of Polymers with Various Porous Morphologies: Toward Hybrid Materials Meant for Heterogeneous Supported Catalysis.

Hybrid materials consisting of metallic nanoparticles (NPs) adsorbed on porous polymeric supports have been the subject of intense research for many years. Such materials indeed gain from intrinsic properties, e.g., high specific surface area, catalytic properties, porous features, etc., of both components. Rational design of such materials is fundamental regarding the functionalization of the support surface and thus the interactions required for the metallic NPs to be strongly immobilized at the pore surface. Herein are presented some significant scientific contributions to this rapidly expanding research field. This contribution will notably focus on various examples of such hybrid systems prepared from porous polymers, whatever the morphology and size of the pores. Such porous polymeric supports can display pores with sizes ranging from a few nanometers to hundreds of microns while pore morphologies, such as spherical, tubular, etc., and/or open or closed, can be obtained. These systems have allowed some catalytic molecular reactions to be successfully undertaken, such as the reduction of nitroaromatic compounds or dyes, e.g., methylene blue and Eosin Y, boronic acid-based C-C homocoupling reactions, but also cascade reactions consisting of two catalytic reactions achieved in a row.

Effect of uniform capacitively coupled electric fields on matrix metabolism of osteoarthritic cartilage.

BACKGROUND: Osteoarthritis (OA) is a common and debilitating condition characterized by degeneration of hyaline cartilage. Currently, there is no treatment for OA that directly targets degradation of cartilage matrix. Capacitively coupled electric fields (CCEFs) represent a noninvasive and cost-effective treatment modality that can potentially restore articular cartilage homeostasis. Previous studies showed that stimulation of articular cartilage with CCEFs resulted in upregulation of anabolic factors and downregulation of catabolic factors. These studies didn't explain the derivation of the CCEFs or verify their uniformity and field strength, so it's possible that cartilage wasn't exposed to uniform field strength. The present study aims to employ CCEFs with verified uniform field strength in two in-vitro models of OA to investigate its potential to preserve cartilage matrix and validate the results of the aforementioned studies. METHODS: Rabbit hyaline chondrocytes and full-thickness bovine articular cartilage explants were cultured in the absence or presence of CCEF and in the absence or presence of Interleukin1-B (IL-1B). Quantitative polymerase chain reaction (QPCR) was performed on chondrocytes to measure gene expression of ADAM-TS4, MMP3, MMP9, IL-6, TIMP1, and TIMP2. QPCR was performed on explants to measure gene expression of MMP3, Aggrecan, Collagen-2, and TIMP1. Aggrecan concentration in explants was measured with histology. Statistical analysis was performed using one-way analysis of variance and Tukey-Kramer multiple comparison test. RESULTS: The treatment of chondrocytes with IL-1B resulted in upregulated expression of ADAM-TS4, MMP3, MMP9, and IL-6, while simultaneous administration of IL-1B and CCEF led to a relative decrease in ADAM-TS4, MMP3, MMP9, and IL-6 expression and a relative increase in TIMP1 and TIMP2 expression. Application of IL-1B and CCEF to the explants resulted in decreased expression of MMP3 and increased expression of Aggrecan, Collagen-2, and TIMP1 when compared to application of IL-1B alone. CONCLUSION: The data indicate that application of a CCEF with verified uniformity may result in upregulation of cartilage anabolic factors even in the presence of IL-1B while attenuating IL-1B induced upregulation of catabolic factors in both monolayer culture and whole tissue. These results demonstrate the potential of CCEFs to suppress the progression of OA and regenerate articular cartilage matrix.

Optimization of the Synthesis of Natural Polymeric Nanoparticles of Inulin Loaded with Quercetin: Characterization and Cytotoxicity Effect.

Quercetin is a bioactive component that is capable of having therapeutic potential in the prevention of different noncommunicable chronic diseases (NCDs). However, it presents instability in the gastrointestinal tract in addition to low bioavailability. One way to overcome the limitations of quercetin lies in using nanotechnology for the development of nanoparticles, based on biopolymers, that are capable of being ingestible. Inulin, a fructan-type polysaccharide, acts as a delivery system for the release of quercetin in a target cell, guaranteeing the stability of the molecule. Inulin-coated quercetin nanoparticles were synthesized by the spray dryer method, and four variables were evaluated, namely inulin concentration (5-10% w/v), feed temperature (40-60 °C), inlet temperature (100-200 °C) and outlet temperature (60-100 °C). The optimal conditions were obtained at 10% w/v inulin concentration, with 45 °C feed temperature, 120 °C inlet temperature and 60 °C outlet temperature, and the nanoparticle size was 289.75 ± 16.3 nm in water. Fluorescence microscopy indicated quercetin loading in the inulin nanoparticles, with an encapsulation efficiency of approximately 73.33 ± 7.86%. Inulin-coated quercetin nanoparticles presented effects of inhibition in Caco-2 and HepG2 cells, but not in HDFa cells. The experimental data showed the potential of inulin nanoparticles as transport materials for unstable molecules, in oral administration systems, for the encapsulation, protection and release of quercetin.

A two-stage in vivo approach for implanting a 3D printed tissue-engineered tracheal replacement graft: A proof of concept.

OBJECTIVES: To optimize a 3D printed tissue-engineered tracheal construct using a combined in vitro and a two-stage in vivo technique. METHODS: A 3D-CAD (Computer-aided Design) template was created; rabbit chondrocytes were harvested and cultured. A Makerbot Replicator™ 2x was used to print a polycaprolactone (PCL) scaffold which was then combined with a bio-ink and the previously harvested chondrocytes. In vitro: Cell viability was performed by live/dead assay using Calcein A/Ethidium. Gene expression was performed using quantitative real-time PCR for the following genes: Collagen Type I and type II, Sox-9, and Aggrecan. In vivo: Surgical implantation occurred in two stages: 1) Index procedure: construct was implanted within a pocket in the strap muscles for 21 days and, 2) Final surgery: construct with vascularized pedicle was rotated into a segmental tracheal defect for 3 or 6 weeks. Following euthanasia, the construct and native trachea were explanted and evaluated. RESULTS: In vitro: After 14 days in culture the constructs showed >80% viable cells. Collagen type II and sox-9 were overexpressed in the construct from day 2 and by day 14 all genes were overexpressed when compared to chondrocytes in monolayer. IN VIVO: By day 21 (immediately before the rotation), cartilage formation could be seen surrounding all the constructs. Mature cartilage was observed in the grafts after 6 or 9 weeks in vivo. CONCLUSION: This two-stage approach for implanting a 3D printed tissue-engineered tracheal replacement construct has been optimized to yield a high-quality, printable segment with cellular growth and viability both in vitro and in vivo.

Biomechanical properties of the ex vivo porcine trachea: A benchmark for three-dimensional bioprinted airway replacements.

PURPOSE: Combining tissue engineering and three-dimensional (3D) printing may allow for the introduction of a living functional tracheal replacement graft. However, defining the biomechanical properties of the native trachea is a key prerequisite to clinical translation. To achieve this, we set out to define the rotation, axial stretch capacity, and positive intraluminal pressure capabilities for ex vivo porcine tracheas. STUDY DESIGN: Animal study. MATERIALS AND METHODS: Six full-length ex vivo porcine tracheas were bisected into 5.5 cm segments. Maximal positive intraluminal pressure was measured by sealing segment ends with custom designed 3D printed caps through which a pressure transducer was introduced. Axial stretch capacity and rotation were evaluated by stretching and rotating the segments along their axis between two clamps, respectively. RESULTS: Six segments were tested for axial lengthening and the average post-stretch length percentage was 148.92% (range 136.81-163.48%, 95% CI 153-143%). The mean amount of length gain achieved per cartilaginous ring was 7.82% (range 4.71-10.95%, 95% CI 6.3-9.35%). Four tracheal segments were tested for maximal positive intraluminal pressure, which was over 400 mmHg. Degree of rotation testing found that the tracheal segments easily transformed 180° in anterior-posterior bending, lateral bending, and axial rotational twisting. CONCLUSIONS: We define several biomechanical properties of the ex vivo porcine trachea by reporting the rotation, axial stretch capacity, and positive intraluminal pressure capabilities. We hope that this will aid future work in the clinical translation of 3D bioprinted airway replacement grafts and ensure their compatibility with native tracheal properties.

Evaluation of the histological and biomechanical properties of poly-4-hydroxybutyrate scaffold for pelvic organ prolapse, compared with polypropylene mesh in a rabbit model.

INTRODUCTION AND HYPOTHESIS: Poly-4-hydroxybutyrate (P4HB) is a biopolymer produced by Escherichia coli K12 bacteria. P4HB is fully resorbed in vivo by 18-24 months post-implantation. The aim of this study is to evaluate P4HB in the rabbit abdomen and vagina to determine that the biomechanical and histological properties are similar to the standard polypropylene mesh. Our hypothesis is that the histological and biomechanical properties of a fully absorbable graft will be similar to a lightweight polypropylene (PP) mesh when implanted in rabbit vagina and abdomen. METHODS: Sixteen (n = 16) female New Zealand White (retired breeder) rabbits were equally divided between two time points (3 and 9 months). A total of 17 rabbits were used owing to one death secondary to suspected cardiomyopathy. P4HB scaffold and PP mesh were subcutaneously and peri-vaginally implanted into the rabbit abdomen and vagina respectively. All rabbits had both posterior and anterior vaginal implants, and half of the rabbits had four abdominal implants in addition to the vaginal implants. The abdominal implants were 4.5 cm long × 1.5 cm wide whereas the vaginal implants were 1.5 cm long × 0.5 cm wide. At 3 and 9 months, gross necropsy was performed and samples were obtained, sectioned, stained and evaluated via histological analysis. Specimens were assessed for host inflammatory response, neovascularization, elastin content, and collagen deposition/maturation. Specimens were also biomechanically evaluated via uniaxial tensile test to determine the stiffness, ultimate tensile strength and load at ultimate tensile strength of the device/tissue composite. RESULTS: No abdominal mesh exposures were noted. A comparable number of asymptomatic partial vaginal exposures were observed at 3 months (P4HB: n = 3; PP: n = 2) and 9 months (P4HB: n = 3; PP: n = 2) respectively. Histological analysis of specimens showed comparable results in the P4HB and PP groups at 3 and 9 months post-implantation. Although no acute inflammation was seen, chronic inflammation was demonstrated in all specimens. Elastic fibers were present in the 3-month vaginal PP and P4HB specimens, but were not seen again. There was an increase in type I/III collagen noted over time. Biomechanical evaluation of the vaginal mesh tissue complex showed ultimate tensile strength was not significantly different between P4HB and PP groups at 3 (P = 0.625) and 9 months (P = 0.250) respectively. CONCLUSIONS: P4HB scaffold may represent a fully absorbable alternative to permanent mesh for pelvic organ prolapse (POP) repair.