Mesenchymal stem cells (MSCs) are currently being widely investigated both in the lab and in clinical trials for multiple disease states. The differentiation, trophic, and immunomodulatory ...characteristics of MSCs contribute to their therapeutic effects. Another often overlooked factor related to efficacy is the degree of engraftment. When reported, engraftment is generally low and transient in nature. MSC delivery methods should be tailored to the lesion being treated, which may be local or systemic, and customized to the mechanism of action of the MSCs, which can also be local or systemic. Engraftment efficiency is enhanced by using intra-arterial delivery instead of intravenous delivery, thus avoiding the “first-pass” accumulation of MSCs in the lung. Several methodologies to target MSCs to specific organs are being developed. These cell targeting methodologies focus on the modification of cell surface molecules through chemical, genetic, and coating techniques to promote selective adherence to particular organs or tissues. Future improvements in targeting and delivery methodologies to improve engraftment are expected to improve therapeutic results, extend the duration of efficacy, and reduce the effective (MSC) therapeutic dose.
Gelatin methacrylate (GelMA) and hyaluronic acid methacrylate (HAMA) are frequently used biomaterials for 3D bioprinting, with individual well-established material characteristics.
To identify an ...ideal combination of GelMA and HAMA for chondrogenesis, a novel, primary human chondrocyte COL2A1-Gaussia luciferase reporter system (HuCol2gLuc) was developed. With this non-destructive, high-throughput temporal assay, Gaussia luciferase is secreted from the cells and used as a proxy for measuring type II collagen production. GelMA:HAMA ratios were screened using the reporter system before proceeding to 3D bioprinting. This method is efficient, saving on time and materials, resulting in a streamlined process of biomaterial optimization. The screen revealed that the addition of HAMA to GelMA improved chondrogenesis over GelMA (15%) alone. Storage moduli were measured using dynamic mechanical analysis of the same GelMA:HAMA ratios and established an initial threshold for chondrogenesis of ∼30kPa. To determine if biomaterial storage moduli impact cell mobility, human primary chondrocytes transduced with green fluorescent protein (GFP) were 3D bioprinted in either 1:1 or 2:1 ratios with storage moduli of 32kPa and 57.9kPa, respectively. We found that reduced cell mobility, in the stiffer biomaterial, had higher type II collagen expression, than the softer material with more cell mobility. Finally, after 3D bioprinting with HuCol2gLuc cells we successfully identified an optimal combination (2:1) of GelMA:HAMA and photo-crosslinking time (38s) for chondrogenesis.
One challenge of 3D bioprinting is identifying ideal biomaterials that stimulate articular cartilage development. To identify an optimal combination of gelatin methacrylate and hyaluronic acid methacrylate for chondrogenesis we developed a primary human chondrocyte type II collagen Gaussia luciferase reporter cell (HuCol2gLuc). This non-destructive, high-throughput assay uses a secreted Gaussia luciferase as a proxy for temporal type II collagen production. This reporter system streamlines the biomaterial optimization process before 3D bioprinting. We also used it to determine the level of stiffness required for chondrogenesis. And for the first time, we quantified chondrocyte mobility in a 3D bioprinted construct. Together these results indicate that a biomaterial with a higher storage modulus and less cell mobility, improves chondrogenesis.
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Current tissue engineering methods are insufficient for total joint resurfacing, and chondrocytes undergo de-differentiation when expanded on tissue culture plastic. De-differentiated chondrocytes ...show poor re-differentiation in culture, giving reduced glycosaminoglycan (GAG) and collagen matrix accumulation. To address this, porcine synoviocyte-derived extracellular matrix and low (5%) oxygen tension were assessed for their ability to enhance human articular chondrocyte expansion and maintain re-differentiation potential.
Porcine synoviocyte matrices were devitalized using 3 non-detergent methods. These devitalized synoviocyte matrices were compared against tissue culture plastic for their ability to support human chondrocyte expansion. Expansion was further compared at both low (5%), and atmospheric (20%) oxygen tension on all surfaces. Expanded cells then underwent chondrogenic re-differentiation in aggregate culture at both low and atmospheric oxygen tension. Aggregates were assessed for their GAG and collagen content both biochemically and histologically.
Human chondrocytes expanded twice as fast on devitalized synoviocyte matrix vs. tissue culture plastic, and cells retained their re-differentiation capacity for twice the number of population doublings. There was no significant difference in growth rate between low and atmospheric oxygen tension. There was significantly less collagen type I, collagen type II, aggrecan and more MMP13 expression in cells expanded on synoviocyte matrix vs. tissue culture plastic. There were also significant effects due to oxygen tension on gene expression, wherein there was greater collagen type I, collagen type II, SOX9 and less MMP13 expression on tissue culture plastic compared to synoviocyte matrix. There was a significant increase in GAG, but not collagen, accumulation in chondrocyte aggregates re-differentiated at low oxygen tension over that achieved in atmospheric oxygen conditions.
Synoviocyte-derived matrix supports enhanced expansion of human chondrocytes such that the chondrocytes are maintained in a state from which they can re-differentiate into a cartilage phenotype after significantly more population doublings. Also, low oxygen tension supports GAG, but not collagen, accumulation. These findings are a step towards the production of a more functional, tissue engineered cartilage.
Objectives
To describe outcomes following percutaneous coronary intervention (PCI) in patients who would usually have undergone coronary artery bypass grafting (CABG).
Background
In the United ...Kingdom, cardiac surgery for coronary artery disease (CAD) was dramatically reduced during the first wave of the COVID‐19 pandemic. Many patients with “surgical disease” instead underwent PCI.
Methods
Between 1 March 2020 and 31 July 2020, 215 patients with recognized “surgical” CAD who underwent PCI were enrolled in the prospective UK‐ReVasc Registry (ReVR). 30‐day major cardiovascular event outcomes were collected. Findings in ReVR patients were directly compared to reference PCI and isolated CABG pre‐COVID‐19 data from British Cardiovascular Intervention Society (BCIS) and National Cardiac Audit Programme (NCAP) databases.
Results
ReVR patients had higher incidence of diabetes (34.4% vs 26.4%, P = .008), multi‐vessel disease with left main stem disease (51.4% vs 3.0%, P < .001) and left anterior descending artery involvement (94.8% vs 67.2%, P < .001) compared to BCIS data. SYNTAX Score in ReVR was high (mean 28.0). Increased use of transradial access (93.3% vs 88.6%, P = .03), intracoronary imaging (43.6% vs 14.4%, P < .001) and calcium modification (23.6% vs 3.5%, P < .001) was observed. No difference in in‐hospital mortality was demonstrated compared to PCI and CABG data (ReVR 1.4% vs BCIS 0.7%, P = .19; vs NCAP 1.0%, P = .48). Inpatient stay was half compared to CABG (3.0 vs 6.0 days). Low‐event rates in ReVR were maintained to 30‐day follow‐up.
Conclusions
PCI undertaken using contemporary techniques produces excellent short‐term results in patients who would be otherwise CABG candidates. Longer‐term follow‐up is essential to determine whether these outcomes are maintained over time.
The aim of this study was to develop a novel biodegradable magnesium (Mg) alloy for bone implant applications. We used scandium (Sc; 2 wt %) and strontium (Sr; 2 wt %) as alloying elements due to ...their high biocompatibility, antibacterial efficacy, osteogenesis, and protective effects against corrosion. In the present work, we also examined the effect of a heat treatment process on the properties of the Mg‐Sc‐Sr alloy. Alloys were manufactured using a metal casting process followed by heat treatment. The microstructure, corrosion, mechanical properties, antibacterial activity, and osteogenic activity of the alloy were assessed in vitro. The results showed that the incorporation of Sc and Sr elements controlled the corrosion, reduced the hydrogen generation, and enhanced mechanical properties. Furthermore, alloying with Sc and Sr demonstrated a significantly enhanced antibacterial activity and decreased biofilm formation compared to control Mg. Also, culturing Mg‐Sc‐Sr alloy with human bone marrow‐derived mesenchymal stromal cells showed a high degree of biocompatibility (>90% live cells) and a significant increase in osteoblastic differentiation in vitro shown by Alizarin red staining and alkaline phosphatase activity. Based on these results, the Mg‐Sc‐Sr alloy heat‐treated at 400°C displayed optimal mechanical properties, corrosion rate, antibacterial efficacy, and osteoinductivity. These characteristics make the Mg‐Sc‐Sr alloy a promising candidate for biodegradable orthopedic implants in the fixation of bone fractures such as bone plate‐screws or intramedullary nails.
Abstract Cell surface coating is a methodology wherein specific molecules are transiently anchored onto cell membrane to modulate cell behavior. Cell surface coating was tested as a method to deliver ...mesenchymal stem cells (MSCs) to endothelial cells via binding to intercellular cell adhesion molecule-1 (ICAM-1). MSCs coated with palmitated protein G (PPG) followed by antibodies to ICAM-1 (AbICAM-1 ), and incubated on ICAM-I coated coverslips showed a 40-fold increase in cell binding over PPG-only controls. AbICAM-1 –coated MSCs incubated with human vascular endothelial cells (HUVECs), with and without exposure to TNFα (to upregulate ICAM-1 expression), showed 2.6-fold increased binding to control HUVECs over PPG-only controls, and a 16-fold increase in binding to TNFα-treated HUVECs. Pretreatment of HUVECs with ICAM-1 antibody promoted the attachment of PPG-only MSCs while reducing the attachment of AbICAM-1 –MSCs by approximately 50%. In flow chamber studies on TNFα-stimulated HUVECs, PPG-only, and MSC-only lost 80–90% of their initial binding at 4 dyne/cm2 , while AbICAM-1 –MSCs maintained 100% binding at 4 dyne/cm2 and 40% binding at 25 dyne/cm2 . These results demonstrate that cell surface coating promotes the attachment of MSCs to endothelial cells, and provides a methodology for the delivery of stem cells to sites of inflammation.
Two recently completed phase 3 trials (003 and 004) showed fidaxomicin to be noninferior to vancomycin for curing Clostridium difficile infection (CDI) and superior for reducing CDI recurrences. In ...both studies, adults with active CDI were randomized to receive blinded fidaxomicin 200 mg twice daily or vancomycin 125 mg 4 times a day for 10 days. Post hoc exploratory intent-to-treat (ITT) time-to-event analyses were undertaken on the combined study 003 and 004 data, using fixed-effects meta-analysis and Cox regression models. ITT analysis of the combined 003/004 data for 1164 patients showed that fidaxomicin reduced persistent diarrhea, recurrence, or death by 40% (95% confidence interval CI, 26%—51%; P < .0001) compared with vancomycin through day 40. A 37% (95% CI, 2%—60%; P = .037) reduction in persistent diarrhea or death was evident through day 12 (heterogeneity P = .50 vs 13—40 days), driven by 7 (1.2%) fidaxomicin versus 17 (2.9%) vancomycin deaths at <12 days. Low albumin level, low eosinophil count, and CDI treatment preenrollment were risk factors for persistent diarrhea or death at 12 days, and CDI in the previous 3 months was a risk factor for recurrence (all P < .01). Fidaxomicin has the potential to substantially improve outcomes from CDI.
It has been hypothesized that mesenchymal stem cells (MSCs) home to sites of injury. Nevertheless, efficient delivery of MSCs to target organs and description of their ultimate fate remain major ...challenges. We provide evidence that intra-arterially (IA) injected MSCs selectively engraft from the circulation as perivascular cells in the bone marrow (BM) after a localized radiation injury. Luciferase-expressing MSCs, derived from a conditionally immortalized clone (BMC-9) representing a pure population of cells, were arterially delivered into mice irradiated in one leg. Cell distribution was measured by bioluminescent imaging and final destination assessed by luciferase immunolocalization. IA injections resulted in engraftment only in the irradiated leg where cells localize and proliferate abluminal to the BM vasculature, a phenomenon not replicated with intravenous injections or with IA injections of kidney cells harvested from the same donor used for MSCs. Furthermore, MSCs harvested from the engrafted marrow and serially transplanted retain the ability to selectively engraft at sites of injury. This study demonstrates that MSCs can serially engraft at sites of injury from the circulation, that they reside in the perivascular space, and that arterial delivery is more efficient than venous delivery for cell engraftment.
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