Biology subjects

Pawelec, K.

Publications and source records attributed to Pawelec, K..

7 recordsLinked to original sources

bioRxiv2025

Distinct Roles of Surface Nanostructure and Polymer Degradation in Fibroblast Response to Device Design

Fibrotic encapsulation of implanted biomedical devices represents the highest cause of device failure across numerous fields, including orthopedics, breast implants and neural electrodes. While most research has focused on the immune system for driving the foreign body response to devices, fibroblasts are emerging as another key regulator of tissue response. In the present study, we evaluated the effects of porous device design on the activation of primary human dermal fibroblasts into myofibroblasts, a contractile cell that is a hallmark of fibrosis, over four weeks in culture. In particular two factors were studied 1) the introduction of nanoparticles, as they are increasingly being used for device functionalization, and 2) the polymer matrix, which dictates chemistry, mechanics and degradation. The addition of tantalum oxide (TaOx) nanoparticles (0-20wt%) had a minimal effect on fibroblasts, significantly down-regulating expression of alpha smooth muscle actin (SMA) (0.31 {+/-} 0.1), likely driven by the increase in nanoscale surface roughness. The polymer matrix of the device caused significant changes to myofibroblast activation, with the fast degrading polymer, poly(lactide co-glycolide) (PLGA) 50:50, significantly up-regulating multiple myofibroblast markers, including SMA (5.16 {+/-} 2.5), vinculin, integrin {beta}1, and integrin {beta}5, compared to non-degrading polycaprolactone (PCL). The effect was due to the release of degradation products, namely lactic acid, which affects cellular metabolism. Together this highlights that device design affects biological response immediately post-implantation in ways that impact the ultimate success or failure of biomedical devices.

bioengineering↗

bioRxiv2024

Material Composition and Implantation Site Affect in vivo Device Degradation Rate

Successful tissue engineering requires biomedical devices that initially stabilize wounds, then degrade as tissue is regenerated. However, the material degradation rates reported in literature are often conflicting. Incorporation of in situ monitoring functionality into implanted devices would allow real time assessment of degradation and potential failure. This necessitates introduction of contrast agent as most biomedical devices are composed of polymeric materials with no inherent contrast in medical imaging modalities. In the present study, computed tomography (CT)-visible radiopaque composites were created by adding 5-20wt% tantalum oxide (TaOx) nanoparticles into polymers with distinct degradation profiles: polycaprolactone (PCL), poly(lactide-co-glycolide) (PLGA) 85:15 and PLGA 50:50, representing slow, medium and fast degrading materials respectively. Radiopaque phantoms, mimicking porous tissue engineering devices, were implanted into mice intramuscularly or intraperitoneally, and monitored via CT over 20 weeks. Changes in phantom volume, including collapse and swelling, were visualized over time. Phantom degradation profile was determined by polymer matrix, regardless of nanoparticle addition and foreign body response was dictated by the implant site. In addition, degradation kinetics were significantly affected in mid-degrading materials, transitioning from linear degradation intramuscularly to exponential degradation intraperitoneally, due to differences in inflammatory responses and fluid flow. Nanoparticle excretion from degraded phantoms lagged behind polymer, and future studies will modulate nanoparticle clearance. Utilizing in situ monitoring, this study seeks to unify literature and facilitate better tissue engineering devices, by highlighting the relative effect of composition and implant site on important materials properties.

bioengineering↗

bioRxiv2024

Device Design and Diagnostic Imaging of Radiopaque 3D Printed Tissue Engineering Scaffolds

3D printed biomaterial implants are revolutionizing personalized medicine for tissue repair, especially in orthopedics. In this study, a radiopaque Bi2O3 doped polycaprolactone (PCL) composite is developed and implemented to enable the use of diagnostic X-ray technologies, especially photon counting X-ray computed tomography (PCCT), for comprehensive in vivo device monitoring. PCL filament with homogeneous Bi2O3 nanoparticle (NP) dispersion (0.8 to 11.7 wt%) are first fabricated. Tissue engineered scaffolds (TES) are then 3D printed with the composite filament, optimizing printing parameters for small feature size and severely overhung geometries. These composite TES are characterized via micro-computed tomography ({micro}CT), tensile testing, and a cytocompatibility study, with Bi2O3 mass fractions as low as 2 wt% providing excellent radiographic distinguishability, improved tensile properties, and equivalent cytocompatibility of neat PCL. The excellent radiographic distinguishability is validated in situ by imaging 4 and 7 wt% TES in a mouse model with {micro}CT, showing excellent agreement with in vitro measurements. Subsequently, CT image-derived swine menisci are 3D printed with composite filament and re-implanted in their corresponding swine legs ex vivo. Re-imaging the swine legs via clinical CT allows facile identification of device location and alignment. Finally, the emergent technology of PCCT unambiguously distinguishes implanted menisci in situ.

bioengineering↗

bioRxiv2024

Biomaterial Degradation Products affect Regenerating Glia Independently of Surface Properties

Devices to treat peripheral nerve injury (PNI) must balance many considerations to effectively guide regenerating nerves across a gap and achieve functional recovery. To enhance efficacy, design features like luminal fillers have been explored extensively. Material choice for PNI devices is also critical, as the determining factor of device mechanics, and degradation rate and has increasingly been found to directly impact biological response. This study investigated the ways in which synthetic polymer materials impact the differentiation state and myelination potential of Schwann cells, peripheral nerve glia. Microporous substrates of polycaprolactone (PCL), poly(lactide-co-glycolide) (PLGA) 85:15, or PLGA 50:50 were chosen, as materials already used in nerve repair devices, representing a wide range of mechanics and degradation profiles. Schwann cells co-cultured with dorsal root ganglion (DRG) neurons on the substrates expressed more mature myelination proteins (MPZ) on PLGA substrates compared to PCL. Changes to myelination and differentiation state of glia were reflected in adhesion proteins expressed by glia, including {beta}-dystroglycan and integrin 6, both laminin binding proteins. Importantly, degradation products of the polymers affected glial expression independently of direct attachment. Fast degrading PLGA 50:50 substrates released measurable amounts of degradation products (lactic acid) within the culture period, which may push Schwann cells towards glycolytic metabolism, decreasing expression of early transcription factors like sox10. This study shows the importance of understanding not only material effects on attachment, but also on cellular metabolism which drives myelination responses.

bioengineering↗

bioRxiv2024

Computed Tomography of Polymeric Biomedical Implants from Bench to Bedside

Implanted biomedical devices require porosity to encourage tissue regeneration. However, characterizing porosity, which affects many functional device properties, is non-trivial. Computed tomography (CT) is a quick, versatile, and non-destructive way to gain 3D structural information. While optimization of CT for polymeric devices has been investigated at the bench on high-resolution micro-CT (CT) scanners, pre-clinical and clinical systems cannot be tuned the same way, given an overriding objective to minimize ionizing radiation exposure to living tissues. Therefore, in this study we tested feasibility of obtaining structural information in pre-clinical systems and CT under physiological conditions. The size of resolved features in porous structures is highly dependent on the resolution (voxel size) of the scan. Lower resolution underestimated porosity and overestimated pore size. With the homogeneous introduction of radiopaque nanoparticle contrast agent into both biopolymers and synthetic polymers, devices could be imaged in the hydrated state, even at high-resolution. Biopolymers had significant structural changes at the micro-scale post-hydration, including a mean increase of 130% in pore wall thickness that could potentially impact biological response. Through optimizing devices for medical imaging, CT has the potential to be a facile way to monitor devices from initial design stages through to clinical translation.

bioengineering↗

bioRxiv2023

In vivo Biomedical Imaging of Immune Tolerant, Radiopaque Nanoparticle-Embedded Polymeric Device Degradation

Biomedical implants remain an important clinical tool for restoring patient mobility and quality of life after trauma. While polymers are often used for devices, their degradation profile remains difficult to determine post-implantation. CT monitoring could be a powerful tool for in situ monitoring of devices, but polymers require the introduction of radiopaque contrast agents, like nanoparticles, to be distinguishable from native tissue. As device function is mediated by the immune system, use of radiopaque nanoparticles for serial monitoring therefore requires a minimal impact on inflammatory response. Radiopaque polymer composites were produced by incorporating 0-20wt% TaOx nanoparticles into synthetic polymers: polycaprolactone (PCL) and poly(lactide-co-glycolide) (PLGA). In vitro inflammatory response to TaOx was determined by monitoring mouse bone marrow derived macrophages on composite films. Nanoparticle addition stimulated only a slight inflammatory reaction, namely increased TNF secretion, mediated by changes to the polymer matrix properties. When devices (PLGA 50:50 + 20wt% TaOx) were implanted subcutaneously in a mouse model of chronic inflammation, no changes to device degradation were noted although macrophage number was increased over 12 weeks. Serial CT monitoring of devices post-implantation provided a detailed timeline of device structural collapse, with no burst release of the nanoparticles from the implant. Changes to the device were not significantly altered with monitoring, nor was the immune system ablated when checked via blood cell count and histology. Thus, polymer devices incorporating radiopaque TaOx NPs can be used for in situ CT monitoring, and can be readily combined with multiple medical imaging techniques, for a truly dynamic view biomaterials interaction with tissues throughout regeneration, paving the way for a more structured approach to biomedical device design.

bioengineering↗

bioRxiv2021

Prevention of Drug-Induced Lung Fibrosis via Inhibition of the MRTF/SRF Transcription Pathway

Drug-induced lung fibrosis is a debilitating disease, linked to high morbidity and mortality. A number of drugs can cause fibrosis, many of which are used to treat cancer, including chemotherapy agents and immune checkpoint inhibitors. The MRTF/SRF transcription pathway has been proposed as a potential therapeutic target, as it is critical for myofibroblast differentiation, a hallmark of fibrosis. In human lung fibroblasts, the MRTF/SRF pathway inhibitor, CCG-257081, effectively decreased mRNA levels of downstream genes: smooth muscle actin and connective tissue growth factor, with IC50s of 4 and 15 M, respectively. The ability of CCG-257081 to prevent inflammation and fibrosis, measured via pulmonary collagen content and histopathology, was tested in a murine model of chemotherapy-induced lung fibrosis. Animals were given intraperitoneal bleomycin for four weeks, and concurrently dosed with CCG-257081 (0, 10, 30, and 100 mg/kg PO), a clinical anti-fibrotic (nintedanib), or clinical standard of care (prednisolone). Mice treated with 100 mg/kg CCG-257081 gained weight vs. vehicle-treated control mice, while those receiving nintedanib and prednisolone lost significant weight. Hydroxyproline content and histological findings in tissue of animals on 100 mg/kg CCG-257081 were not significantly different from naive tissue, indicating successful prevention. Measures of tissue fibrosis were comparable between CCG-257081 and nintedanib, but only the MRTF/SRF inhibitor decreased plasminogen activator inhibitor-1 (PAI-1), a marker linked to fibrosis, in bronchoalveolar lavage fluid. Prednisolone led to marked increases in lung fibrosis. This study demonstrates the potential use of MRTF/SRF inhibitors to prevent drug-induced lung fibrosis in a clinically relevant model of drug-induced disease.

pharmacology and toxicology↗