Bone formation by human paediatric marrow stromal cells in a functional allogeneic immune system

Allogeneic stem-cell based regenerative medicine is a promising approach for bone defect repair. The use of chondrogenically differentiated human marrow stromal cells (MSCs) has been shown to lead to bone formation by endochondral ossification in immunodeficient pre-clinical models. However, an insight into the interactions between the allogeneic immune system and the human MSC-derived bone grafts has not been fully achieved yet. The choice of a potent source of MSCs isolated from pediatric donors with consistent differentiation and high proliferation abilities, as well as low immunogenicity, could increase the chance of success for bone allografts. In this study, we employed an immunodeficient animal model humanised with allogeneic immune cells to study the immune responses towards chondrogenically differentiated human pediatric MSCs (ch-pMSCs). We show that ch-differentiated pMSCs remained non-immunogenic to allogeneic CD4 and CD8 T cells in an in vitro co-culture model. After subcutaneous implantation in mice, ch-pMSC-derived grafts were able to initiate bone mineralisation in the presence of an allogeneic immune system for 3 weeks without the onset of immune responses. Re-exposing the splenocytes of the humanised animals to pMSCs did not trigger further T cell proliferation, suggesting an absence of secondary immune responses. Moreover, ch-pMSCs generated mature bone after 8 weeks of implantation that persisted for up to 6 more weeks in the presence of an allogeneic immune system. These data collectively show that human allogeneic chondrogenically differentiated pediatric MSCs might be a safe and potent option for bone defect repair in the tissue engineering and regenerative medicine setting.

Incorporating strontium enriched amorphous calcium phosphate granules in collagen/collagen-magnesium-hydroxyapatite osteochondral scaffolds improves subchondral bone repair

Osteochondral defect repair with a collagen/collagen-magnesium-hydroxyapatite (Col/Col-Mg-HAp) scaffold has demonstrated good clinical results. However, subchondral bone repair remained suboptimal, potentially leading to damage to the regenerated overlying neocartilage. This study aimed to improve the bone repair potential of this scaffold by incorporating newly developed strontium (Sr) ion enriched amorphous calcium phosphate (Sr-ACP) granules (100-150 μm). Sr concentration of Sr-ACP was determined with ICP-MS at 2.49 ± 0.04 wt%. Then 30 wt% ACP or Sr-ACP granules were integrated into the scaffold prototypes. The ACP or Sr-ACP granules were well embedded and distributed in the collagen matrix demonstrated by micro-CT and scanning electron microscopy/energy dispersive x-ray spectrometry. Good cytocompatibility of ACP/Sr-ACP granules and ACP/Sr-ACP enriched scaffolds was confirmed with in vitro cytotoxicity assays. An overall promising early tissue response and good biocompatibility of ACP and Sr-ACP enriched scaffolds were demonstrated in a subcutaneous mouse model. In a goat osteochondral defect model, significantly more bone was observed at 6 months with the treatment of Sr-ACP enriched scaffolds compared to scaffold-only, in particular in the weight-bearing femoral condyle subchondral bone defect. Overall, the incorporation of osteogenic Sr-ACP granules in Col/Col-Mg-HAp scaffolds showed to be a feasible and promising strategy to improve subchondral bone repair.

The interplay of collagen, macrophages, and microcalcification in atherosclerotic plaque cap rupture mechanics

The rupture of an atherosclerotic plaque cap overlying a lipid pool and/or necrotic core can lead to thrombotic cardiovascular events. In essence, the rupture of the plaque cap is a mechanical event, which occurs when the local stress exceeds the local tissue strength. However, due to inter- and intra-cap heterogeneity, the resulting ultimate cap strength varies, causing proper assessment of the plaque at risk of rupture to be lacking. Important players involved in tissue strength include the load-bearing collagenous matrix, macrophages, as major promoters of extracellular matrix degradation, and microcalcifications, deposits that can exacerbate local stress, increasing tissue propensity for rupture. This review summarizes the role of these components individually in tissue mechanics, along with the interplay between them. We argue that to be able to improve risk assessment, a better understanding of the effect of these individual components, as well as their reciprocal relationships on cap mechanics, is required. Finally, we discuss potential future steps, including a holistic multidisciplinary approach, multifactorial 3D in vitro model systems, and advancements in imaging techniques. The obtained knowledge will ultimately serve as input to help diagnose, prevent, and treat atherosclerotic cap rupture.

Addition of heparin binding sites strongly increases the bone forming capabilities of BMP9 in vivo

Bone Morphogenetic proteins (BMPs) like BMP2 and BMP7 have shown great potential in the treatment of severe bone defects. In recent in vitro studies, BMP9 revealed the highest osteogenic potential compared to other BMPs, possibly due to its unique signaling pathways that differs from other osteogenic BMPs. However, in vivo the bone forming capacity of BMP9-adsorbed scaffolds is not superior to BMP2 or BMP7. In silico analysis of the BMP9 protein sequence revealed that BMP9, in contrast to other osteogenic BMPs such as BMP2, completely lacks so-called heparin binding motifs that enable extracellular matrix (ECM) interactions which in general might be essential for the BMPs' osteogenic function. Therefore, we genetically engineered a new BMP9 variant by adding BMP2-derived heparin binding motifs to the N-terminal segment of BMP9's mature part. The resulting protein (BMP9 HB) showed higher heparin binding affinity than BMP2, similar osteogenic activity in vitro and comparable binding affinities to BMPR-II and ALK1 compared to BMP9. However, remarkable differences were observed when BMP9 HB was adsorbed to collagen scaffolds and implanted subcutaneously in the dorsum of rats, showing a consistent and significant increase in bone volume and density compared to BMP2 and BMP9. Even at 10-fold lower BMP9 HB doses bone tissue formation was observed. This innovative approach of significantly enhancing the osteogenic properties of BMP9 simply by addition of ECM binding motifs, could constitute a valuable replacement to the commonly used BMPs. The possibility to use lower protein doses demonstrates BMP9 HB's high translational potential.

Case Report: Resolution of high grade anal squamous intraepithelial lesion with antibiotics proposes a new role for syphilitic infection in potentiation of HPV-associated ASCC

Introduction

Human Papillomavirus (HPV) is the primary risk factor for the development of anal intraepithelial neoplasia (AIN) and is a leading risk factor for anogenital squamous cell carcinoma (ASCC). Despite common shared risk factors for both HPV and syphilis, co-infection is not well documented, and the role of syphilitic infection in HPV-associated AIN and ASCC potentiation is not defined.

Case description/methods

A 72-year-old single male presented with complaints of mild rectal pain and intermittent rectal bleeding. A flexible sigmoidoscopy was performed, and a firm 4.5cm x 3cm perianal mass was detected and superficially biopsied. Pathology findings demonstrated evidence of a high grade squamous intraepithelial lesion (HGSIL, AIN II/III/AIS) with viral cytopathic effect, consistent with HPV infection. Much of the biopsied lesion showed acanthotic squamous mucosa with intraepithelial neutrophils and abundant submucosal plasma cells, suggesting possible syphilitic involvement. Subsequent immunohistochemical staining for p16 as a surrogate marker for HPV was positive, as was an immunohistochemical stain for spirochetes, supportive of co-infection with Treponema pallidum pallidum (T. pallidum), the causative agent in venereal syphilis. The patient was referred to an infectious disease specialist for syphilitic infection and was treated with penicillin with surprisingly complete resolution of the lesion. EUAs were performed 2- and 3-months following treatment without lesion recurrence. However, one year following diagnosis, a flexible sigmoidoscopy revealed a 5 mm recurrent HPV-related low-grade AIN 1 lesion at the dentate line.

Discussion

Resolution of the lesion by antibiotic treatment for syphilitic infection suggested that co-infection by T. pallidum may potentiate HPV-associated squamous cell carcinoma based on histological findings. Findings from this case, as well as a review of bacterial involvement and potentiation in various cancers, are reviewed here. Such findings offer new insight regarding the role of STI-associated bacteria and HPV co-infection in the establishment of AIN and may additionally propose new treatment modalities for ASCC.

A tissue-engineered model of the atherosclerotic plaque cap: Toward understanding the role of microcalcifications in plaque rupture

Rupture of the cap of an atherosclerotic plaque can lead to thrombotic cardiovascular events. It has been suggested, through computational models, that the presence of microcalcifications in the atherosclerotic cap can increase the risk of cap rupture. However, the experimental confirmation of this hypothesis is still lacking. In this study, we have developed a novel tissue-engineered model to mimic the atherosclerotic fibrous cap with microcalcifications and assess the impact of microcalcifications on cap mechanics. First, human carotid plaque caps were analyzed to determine the distribution, size, and density of microcalcifications in real cap tissue. Hydroxyapatite particles with features similar to real cap microcalcifications were used as microcalcification mimics. Injected clusters of hydroxyapatite particles were embedded in a fibrin gel seeded with human myofibroblasts which deposited a native-like collagenous matrix around the particles, during the 21-day culture period. Second harmonic multiphoton microscopy imaging revealed higher local collagen fiber dispersion in regions of hydroxyapatite clusters. Tissue-engineered caps with hydroxyapatite particles demonstrated lower stiffness and ultimate tensile stress than the control group samples under uniaxial tensile loading, suggesting increased rupture risk in atherosclerotic plaques with microcalcifications. This model supports previous computational findings regarding a detrimental role for microcalcifications in cap rupture risk and can further be deployed to elucidate tissue mechanics in pathologies with calcifying soft tissues.

A Case Report of Wire-localised Excision of Impalpable Recurrent Papillary Thyroid Carcinoma and Discussion of Wire-guided Excision in the Head and Neck Pathology

INTRODUCTION/BACKGROUND

Wire localisation techniques are used widely for precision surgery in many specialities. This convenient technique has not yet become mainstream in the field of head and neck surgery. With limited space and many vital structures coursing through the head and neck region, pathological nodes that are difficult to palpate can be a challenge for clinicians.

CASE PRESENTATION

A patient with a history of papillary thyroid cancer treated with surgery and radioactive iodine had a single pathological node detected on ultrasound surveillance. An isolated recurrence of papillary thyroid carcinoma was confirmed. An excisional biopsy was performed using ultrasound wire guidance to successfully remove the diseased node with minimal morbidity.

CONCLUSION

Wire-guided lymph node excision biopsy is a safe and effective method that can be applied to multiple pathologies. As of yet, it is not routine practice to employ this technique. Larger studies would increase the generalisability and safety profile of this technique in the head and neck region.

The response of human macrophages to 3D printed titanium antibacterial implants does not affect the osteogenic differentiation of hMSCs

Macrophage responses following the implantation of orthopaedic implants are essential for successful implant integration in the body, partly through intimate crosstalk with human marrow stromal cells (hMSCs) in the process of new bone formation. Additive manufacturing (AM) and plasma electrolytic oxidation (PEO) in the presence of silver nanoparticles (AgNPs) are promising techniques to achieve multifunctional titanium implants. Their osteoimmunomodulatory properties are, however, not yet fully investigated. Here, we studied the effects of implants with AgNPs on human macrophages and the crosstalk between hMSCs and human macrophages when co-cultured in vitro with biofunctionalised AM Ti6Al4V implants. A concentration of 0.3 g/L AgNPs in the PEO electrolyte was found to be optimal for both macrophage viability and inhibition of bacteria growth. These specimens also caused a decrease of the macrophage tissue repair related factor C-C Motif Chemokine Ligand 18 (CCL18). Nevertheless, co-cultured hMSCs could osteogenically differentiate without any adverse effects caused by the presence of macrophages that were previously exposed to the PEO (±AgNPs) surfaces. Further evaluation of these promising implants in a bony in vivo environment with and without infection is highly recommended to prove their potential for clinical use.

In Vitro Mineralisation of Tissue-Engineered Cartilage Reduces Endothelial Cell Migration, Proliferation and Tube Formation

Tissue engineering bone via endochondral ossification requires the generation of a cartilage template which undergoes vascularisation and remodelling. While this is a promising route for bone repair, achieving effective cartilage vascularisation remains a challenge. Here, we investigated how mineralisation of tissue-engineered cartilage affects its pro-angiogenic potential. To generate in vitro mineralised cartilage, human mesenchymal stromal cell (hMSC)-derived chondrogenic pellets were treated with β-glycerophosphate (BGP). After optimising this approach, we characterised the changes in matrix components and pro-angiogenic factors by gene expression analysis, histology and ELISA. Human umbilical vein endothelial cells (HUVECs) were exposed to pellet-derived conditioned media, and migration, proliferation and tube formation were assessed. We established a reliable strategy to induce in vitro cartilage mineralisation, whereby hMSC pellets are chondrogenically primed with TGF-β for 2 weeks and BGP is added from week 2 of culture. Cartilage mineralisation determines loss of glycosaminoglycans, reduced expression but not protein abundance of collagen II and X, and decreased VEGFA production. Finally, the conditioned medium from mineralised pellets showed a reduced ability to stimulate endothelial cell migration, proliferation and tube formation. The pro-angiogenic potential of transient cartilage is thus stage-dependent, and this aspect must be carefully considered in the design of bone tissue engineering strategies.

Effectiveness of BMP-2 and PDGF-BB Adsorption onto a Collagen/Collagen-Magnesium-Hydroxyapatite Scaffold in Weight-Bearing and Non-Weight-Bearing Osteochondral Defect Bone Repair: In Vitro, Ex Vivo and In Vivo Evaluation

Despite promising clinical results in osteochondral defect repair, a recently developed bi-layered collagen/collagen-magnesium-hydroxyapatite scaffold has demonstrated less optimal subchondral bone repair. This study aimed to improve the bone repair potential of this scaffold by adsorbing bone morphogenetic protein 2 (BMP-2) and/or platelet-derived growth factor-BB (PDGF-BB) onto said scaffold. The in vitro release kinetics of BMP-2/PDGF-BB demonstrated that PDGF-BB was burst released from the collagen-only layer, whereas BMP-2 was largely retained in both layers. Cell ingrowth was enhanced by BMP-2/PDFG-BB in a bovine osteochondral defect ex vivo model. In an in vivo semi-orthotopic athymic mouse model, adding BMP-2 or PDGF-BB increased tissue repair after four weeks. After eight weeks, most defects were filled with bone tissue. To further investigate the promising effect of BMP-2, a caprine bilateral stifle osteochondral defect model was used where defects were created in weight-bearing femoral condyle and non-weight-bearing trochlear groove locations. After six months, the adsorption of BMP-2 resulted in significantly less bone repair compared with scaffold-only in the femoral condyle defects and a trend to more bone repair in the trochlear groove. Overall, the adsorption of BMP-2 onto a Col/Col-Mg-HAp scaffold reduced bone formation in weight-bearing osteochondral defects, but not in non-weight-bearing osteochondral defects.

Outcomes from 7 years of a direct to audiology referral pathway

Background

The direct to audiology via ENT referral pathway was designed to enhance patient access to audiology services. The pathway is recommended in the Otolaryngology Head & Neck Surgery: a model of care for Ireland report, published in 2019.

Aims

This study aimed to review the outcomes of all patients that attended our institution over the last seven years.

Methods

A retrospective review of the direct to audiology referral service from March 2014 to December 2021 was conducted. Outcomes were defined by the pathway each patient took following attendance at the audiology clinic. Patients were either (i) discharged, (ii) referred for hearing aid(s) or (iii) identified as candidates for further diagnostic assessments, including a follow-up at the ENT outpatient clinic.

Results

During the time frame, 419 patients were triaged to the pathway. The average wait time was 13 days. The average age was 53 years (range 16–96 years, SD = 6.1). Approximately 34% (n = 143) of all patients referred were discharged back to the GP by the audiologist, but 66% (n = 276) presented with ‘red flags’ and needed further investigation in the ENT clinic, with 30% (n = 73) ultimately requiring imaging studies. Over half (n = 254, 61%) were referred for hearing aids.

Conclusion

The direct to audiology initiative has proven effective at reducing waiting times for ENT patients solely in need of audiological intervention. Approximately one-third of these referrals to the ENT service can be assessed comprehensively in the audiology clinic, thereby reducing the demand for ENT clinics, enhancing service provision and expediting onwards referral for amplification.

The Effect of the 2021 Irish Cyber-Attack on Otolaryngology Outpatient Non-attendance at a Model 4 Hospital in the Post-COVID Era

Aim

This study investigates the rate of non-attendance at ENT outpatient appointments in the post-COVID era and the effect of the 2021 Irish cyber-attack on non-attendance.

Methods

A retrospective review of the rates of non-attendance in a post-COVID pre-cyber-attack era wherein patients received an automated text message reminder about their appointment was compared to a post-cyber-attack era wherein the text message reminder system was disabled. In addition, these were compared with rates of non-attendance prior to when the reminder system was introduced. Three periods were compared, two weeks prior to the introduction of the text reminder system, two weeks pre-cyber-attack, and two weeks post-cyber-attack.

Results

Period 1 measured rates of non-attendance prior to the introduction of the text reminder system. Period 2 measured rates of non-attendance at outpatient appointments and consisted of nine clinic days, with two clinics per day. Period 3 similarly measured rates of non-attendance at outpatient appointments and consisted of 10 clinic days, with two clinics per day. The text reminder service was disabled during this collection period because of the cyber-attack. The average non-attendance rate was 16.99% for period 1, 13.00% for period 2, and 16.13% for period 3. A Fisher Exact Test was carried out on data with a p-value set at <0.05. Results reached statistical significance.

Conclusion

Our data shows non-attendance at ENT outpatient appointments increased without the text reminder system. Over two weeks after the attack, non-attendance increased by approximately 3%, which was statistically significant.

Site-Directed Immobilization of an Engineered Bone Morphogenetic Protein 2 (BMP2) Variant to Collagen-Based Microspheres Induces Bone Formation In Vivo

For the treatment of large bone defects, the commonly used technique of autologous bone grafting presents several drawbacks and limitations. With the discovery of the bone-inducing capabilities of bone morphogenetic protein 2 (BMP2), several delivery techniques were developed and translated to clinical applications. Implantation of scaffolds containing adsorbed BMP2 showed promising results. However, off-label use of this protein-scaffold combination caused severe complications due to an uncontrolled release of the growth factor, which has to be applied in supraphysiological doses in order to induce bone formation. Here, we propose an alternative strategy that focuses on the covalent immobilization of an engineered BMP2 variant to biocompatible scaffolds. The new BMP2 variant harbors an artificial amino acid with a specific functional group, allowing a site-directed covalent scaffold functionalization. The introduced artificial amino acid does not alter BMP2′s bioactivity in vitro. When applied in vivo, the covalently coupled BMP2 variant induces the formation of bone tissue characterized by a structurally different morphology compared to that induced by the same scaffold containing ab-/adsorbed wild-type BMP2. Our results clearly show that this innovative technique comprises translational potential for the development of novel osteoinductive materials, improving safety for patients and reducing costs.

Cartilage Oligomeric Matrix Protein-Derived Peptides Secreted by Cartilage Do Not Induce Responses Commonly Observed during Osteoarthritis

OBJECTIVE

To evaluate if 3 peptides derived from the cartilage oligomeric matrix protein (COMP), which wounded zones of cartilage secrete into synovial fluid, possess biological activity and might therefore be involved in the regulation of specific aspects of joint regeneration.

METHODS

The 3 peptides were produced by chemical synthesis and then tested in vitro for known functions of the COMP C-terminal domain from which they derive, and which are involved in osteoarthritis: transforming growth factor-β (TGF-β) signaling, vascular homeostasis, and inflammation. Results. None of the peptides affected the gene expression of COMP in osteochondral progenitor cells (P > 0.05). We observed no effects on the vascularization potential of endothelial cells (P > 0.05). In cultured synovium explants, no differences on the expression of catabolic enzymes or proinflammatory cytokines were found when peptides were added (P > 0.05).

DISCUSSION AND CONCLUSIONS

The 3 peptides tested do not regulate TGF-β signaling, angiogenesis and vascular tube formation, or synovial inflammation in vitro and therefore most likely do not play a major role in the disease process.

The Releasate of Avascular Cartilage Demonstrates Inherent Pro-Angiogenic Properties In Vitro and In Vivo

OBJECTIVE

Cartilage is avascular and numerous studies have identified the presence of single anti- and pro-angiogenic factors in cartilage. To better understand the maintenance hyaline cartilage, we assessed the angiogenic potential of complete cartilage releasate with functional assays in vitro and in vivo.

DESIGN

We evaluated the gene expression profile of angiogenesis-related factors in healthy adult human articular cartilage with a transcriptome-wide analysis generated by next-generation RNAseq. The effect on angiogenesis of the releasate of cartilage tissue was assessed with a chick chorioallantoic membrane (CAM) assay as well as human umbilical vein endothelial cell (HUVEC) migration and proliferation assays using conditioned media generated from tissue-engineered cartilage derived from human articular and nasal septum chondrocytes as well as explants from bovine articular cartilage and human nasal septum. Experiments were done with triplicate samples of cartilage from 3 different donors.

RESULTS

RNAseq data of 3 healthy human articular cartilage donors revealed that the majority of known angiogenesis-related factors expressed in healthy adult articular cartilage are pro-angiogenic. The releasate from generated cartilage as well as from tissue explants, demonstrated at least a 3.1-fold increase in HUVEC proliferation and migration indicating a pro-angiogenic effect of cartilage. Finally, the CAM assay demonstrated that cartilage explants can indeed attract vessels; however, their ingrowth was not observed.

CONCLUSION

Using multiple approaches, we show that cartilage releasate has an inherent pro-angiogenic capacity. It remains vessel free due to anti-invasive properties associated with the tissue itself.

A new semi-orthotopic bone defect model for cell and biomaterial testing in regenerative medicine

In recent decades, an increasing number of tissue engineered bone grafts have been developed. However, expensive and laborious screenings in vivo are necessary to assess the safety and efficacy of their formulations. Rodents are the first choice for initial in vivo screens but their size limits the dimensions and number of the bone grafts that can be tested in orthotopic locations. Here, we report the development of a refined murine subcutaneous model for semi-orthotopic bone formation that allows the testing of up to four grafts per mouse one order of magnitude greater in volume than currently possible in mice. Crucially, these defects are also "critical size" and unable to heal within the timeframe of the study without intervention. The model is based on four bovine bone implants, ring-shaped, where the bone healing potential of distinct grafts can be evaluated in vivo. In this study we demonstrate that promotion and prevention of ossification can be assessed in our model. For this, we used a semi-automatic algorithm for longitudinal micro-CT image registration followed by histological analyses. Taken together, our data supports that this model is suitable as a platform for the real-time screening of bone formation, and provides the possibility to study bone resorption, osseointegration and vascularisation.

Chondrogenically Primed Human Mesenchymal Stem Cells Persist and Undergo Early Stages of Endochondral Ossification in an Immunocompetent Xenogeneic Model

Tissue engineering approaches using progenitor cells such as mesenchymal stromal cells (MSCs) represent a promising strategy to regenerate bone. Previous work has demonstrated the potential of chondrogenically primed human MSCs to recapitulate the process of endochondral ossification and form mature bone in vivo, using immunodeficient xenogeneic models. To further the translation of such MSC-based approaches, additional investigation is required to understand the impact of interactions between human MSC constructs and host immune cells upon the success of MSC-mediated bone formation. Although human MSCs are considered hypoimmunogenic, the potential of chondrogenically primed human MSCs to induce immunogenic responses in vivo, as well as the efficacy of MSC-mediated ectopic bone formation in the presence of fully competent immune system, requires further elucidation. Therefore, the aim of this study was to investigate the capacity of chondrogenically primed human MSC constructs to persist and undergo the process of endochondral ossification in an immune competent xenogeneic model. Chondrogenically differentiated human MSC pellets were subcutaneously implanted to wild-type BALB/c mice and retrieved at 2 and 12 weeks post-implantation. The percentages of CD4⁺ and CD8⁺ T cells, B cells, and classical/non-classical monocyte subsets were not altered in the peripheral blood of mice that received chondrogenic MSC constructs compared to sham-operated controls at 2 weeks post-surgery. However, MSC-implanted mice had significantly higher levels of serum total IgG compared to sham-operated mice at this timepoint. Flow cytometric analysis of retrieved MSC constructs identified the presence of T cells and macrophages at 2 and 12 weeks post-implantation, with low levels of immune cell infiltration to implanted MSC constructs detected by CD45 and CD3 immunohistochemical staining. Despite the presence of immune cells in the tissue, MSC constructs persisted in vivo and were not degraded/resorbed. Furthermore, constructs became mineralised, with longitudinal micro-computed tomography imaging revealing an increase in mineralised tissue volume from 4 weeks post-implantation until the experimental endpoint at 12 weeks. These findings indicate that chondrogenically differentiated human MSC pellets can persist and undergo early stages of endochondral ossification following subcutaneous implantation in an immunocompetent xenogeneic model. This scaffold-free model may be further extrapolated to provide mechanistic insight to osteoimmunological processes regulating bone regeneration and homeostasis.

Spatiotemporal distribution of thrombospondin-4 and -5 in cartilage during endochondral bone formation and repair

During skeletal development most bones are first formed as cartilage templates, which are gradually replaced by bone. If later in life those bones break, temporary cartilage structures emerge to bridge the fractured ends, guiding the regenerative process. This bone formation process, known as endochondral ossification (EO), has been widely studied for its potential to reveal factors that might be used to treat patients with large bone defects. The extracellular matrix of cartilage consists of different types of collagens, proteoglycans and a variety of non-collagenous proteins that organise the collagen fibers in complex networks. Thrombospondin-5, also known as cartilage oligomeric matrix protein (TSP-5/COMP) is abundant in cartilage, where it has been described to enhance collagen fibrillogenesis and to interact with a variety of growth factors, matrix proteins and cellular receptors. However, very little is known about the skeletal distribution of its homologue thrombospondin-4 (TSP-4). In our study, we compared the spatiotemporal expression of TSP-5 and TSP-4 during postnatal bone formation and fracture healing. Our results indicate that in both these settings, TSP-5 distributes across all layers of the transient cartilage, while the localisation of TSP-4 is restricted to the population of hypertrophic chondrocytes. Furthermore, in fractured bones we observed TSP-4 sparsely distributed in the periosteum, while TSP-5 was absent. Last, we analysed the chemoattractant effects of the two proteins on endothelial cells and bone marrow stem cells and hypothesised that, of the two thrombospondins, only TSP-4 might promote blood vessel invasion during ossification. We conclude that TSP-4 is a novel factor involved in bone formation. These findings reveal TSP-4 as an attractive candidate to be evaluated for bone tissue engineering purposes.

The environmental impact of personal protective equipment in a pre and post COVID era in the ENT clinic

Purpose

The use of single use plastic items and plastic wrapping has increased over the last number of decades. Outside of the medical field there has been a conscious drive to reduce single use plastic and reuse items to reduce the amount of waste we produce. We undertook this investigation to quantify our plastic waste production and generate ideas to reduce this volume.

Methodology

Data was collected from a University Hospital ENT outpatient department via real-time recording methods using standard data collection forms. We measured plastic unit usage pre and post COVID restrictions and compared this to our number of patient encounters. Projections of plastic usage were determined via a hypothetical resumption of patient services model.

Results

In total there were 440 patients included. In period one the mean units of plastic used per day was 65.1 (median 67; range 27–84). In the second period, the mean number of plastic units was 23.4 (median 22; range 1–7). Blue nitrile gloves and masks were the most commonly used single use items. The hypothetical projection model predicted a 147.6% increase in single use items following the introduction of COVID precautions.

Conclusion

We have a duty of care not only to our patients but future generations of patients and the environment which we share. Single use items and excessive plastic wrapping have benefits in terms of convenience and sterility, but these conveniences can be easily extended to reusable types to limit our volume of waste, reduce our waste management costs and protect our environment.

Endothelium-derived stromal cells contribute to hematopoietic bone marrow niche formation

Bone marrow stromal cells (BMSCs) play pivotal roles in tissue maintenance and regeneration. Their origins, however, remain incompletely understood. Here we identify rare LNGFR⁺ cells in human fetal and regenerative bone marrow that co-express endothelial and stromal markers. This endothelial subpopulation displays transcriptional reprogramming consistent with endothelial-to-mesenchymal transition (EndoMT) and can generate multipotent stromal cells that reconstitute the bone marrow (BM) niche upon transplantation. Single-cell transcriptomics and lineage tracing in mice confirm robust and sustained contributions of EndoMT to bone precursor and hematopoietic niche pools. Interleukin-33 (IL-33) is overexpressed in subsets of EndoMT cells and drives this conversion process through ST2 receptor signaling. These data reveal generation of tissue-forming BMSCs from mouse and human endothelial cells and may be instructive for approaches to human tissue regeneration.

NK/T-cell lymphoma of the nasal cavity: an unexpected diagnosis

Nasal-type Natural Killer/T-cell Lymphoma (NKTL) is a rare form of extranodal non-Hodgkin's lymphoma, typically arising in the nasopharynx and displaying an aggressive and ultimately fatal clinical course. The disease is linked to Epstein-Barr virus infection and is endemic to Asia and South America, but extremely few cases have been reported in Europe. We present two cases of nasal NKTL unexpectedly diagnosed in elderly patients, following very different presentations to our otolaryngology service. The first case is that of a 73-year-old Irish man with recurrent nasal vestibulitis despite antibiotic treatment. The second case involves a 79-year-old Irish woman presenting with a large mass on the hard palate, found to invade into the floor of the nose. NKTL can pose diagnostic challenges, as the initial clinical presentation can be non-specific and overlap with other nasal conditions, leading to a delay in diagnosis. Biopsy with histopathological and immunohistochemistry analysis is required to establish the definitive diagnosis. Treatment involves multidisciplinary input from radiotherapy and medical oncologists. Clinicians must be aware of this disease and have an index of suspicion when dealing with persistent or aggressive nasal conditions.

Bio-inspired polymeric iron-doped hydroxyapatite microspheres as a tunable carrier of rhBMP-2

Hybrid superparamagnetic microspheres with bone-like composition, previously developed by a bio-inspired assembling/mineralization process, are evaluated for their ability to uptake and deliver recombinant human bone morphogenetic protein-2 (rhBMP-2) in therapeutically-relevant doses along with prolonged release profiles. The comparison with hybrid non-magnetic and with non-mineralized microspheres highlights the role of nanocrystalline, nanosize mineral phases when they exhibit surface charged groups enabling the chemical linking with the growth factor and thus moderating the release kinetics. All the microspheres show excellent osteogenic ability with human mesenchymal stem cells whereas the hybrid mineralized ones show a slow and sustained release of rhBMP-2 along 14 days of soaking into cell culture medium with substantially bioactive effect, as reported by assay with C2C12 BRE-Luc cell line. It is also shown that the release extent can be modulated by the application of pulsed electromagnetic field, thus showing the potential of remote controlling the bioactivity of the new micro-devices which is promising for future application of hybrid biomimetic microspheres in precisely designed and personalized therapies.

Immunomodulation of surface biofunctionalized 3D printed porous titanium implants

Additive manufacturing (AM) techniques have provided many opportunities for the rational design of porous metallic biomaterials with complex and precisely controlled topologies that give rise to unprecedented combinations of mechanical, physical, and biological properties. These favorable properties can be enhanced by surface biofunctionalization to enable full tissue regeneration and minimize the risk of implant-associated infections (IAIs). There is, however, an increasing need to investigate the immune responses triggered by surface biofunctionalized AM porous metals. Here, we studied the immunomodulatory effects of AM porous titanium (Ti-6Al-4V) printed using selective laser melting, and of two additional groups consisting of AM implants surface biofunctionalized using plasma electrolytic oxidation (PEO) with/without silver nanoparticles. The responses of human primary macrophages and human mesenchymal stromal cells (hMSCs) were studied in terms of cell viability, cell morphology and biomarkers of macrophage polarization. Non-treated AM porous titanium triggered a strong pro-inflammatory response in macrophages, albeit combined with signs of anti-inflammatory effects. The PEO treatment of AM porous titanium implants showed a higher potential to induce polarization towards a pro-repair macrophage phenotype. We detected no cytotoxicity against hMSCs in any of the groups. However, the incorporation of silver nanoparticles resulted in strong cytotoxicity against attached macrophages. The results of this study indicate the potential immunomodulatory effects of the AM porous titanium enhanced with PEO treatment, and point towards caution and further research when using silver nanoparticles for preventing IAIs.

Angiogenic Potential of Tissue Engineered Cartilage From Human Mesenchymal Stem Cells Is Modulated by Indian Hedgehog and Serpin E1

With rising demand for cartilage tissue repair and replacement, the differentiation of mesenchymal stem cells (BMSCs) into cartilage tissue forming cells provides a promising solution. Often, the BMSC-derived cartilage does not remain stable and continues maturing to bone through the process of endochondral ossification in vivo. Similar to the growth plate, invasion of blood vessels is an early hallmark of endochondral ossification and a necessary step for completion of ossification. This invasion originates from preexisting vessels that expand via angiogenesis, induced by secreted factors produced by the cartilage graft. In this study, we aimed to identify factors secreted by chondrogenically differentiated bone marrow-derived human BMSCs to modulate angiogenesis. The secretome of chondrogenic pellets at day 21 of the differentiation program was collected and tested for angiogenic capacity using in vitro endothelial migration and proliferation assays as well as the chick chorioallantoic membrane (CAM) assay. Taken together, these assays confirmed the pro-angiogenic potential of the secretome. Putative secreted angiogenic factors present in this medium were identified by comparative global transcriptome analysis between murine growth plate cartilage, human chondrogenic BMSC pellets and human neonatal articular cartilage. We then verified by PCR eight candidate angiogenesis modulating factors secreted by differentiated BMSCs. Among those, Serpin E1 and Indian Hedgehog (IHH) had a higher level of expression in BMSC-derived cartilage compared to articular chondrocyte derived cartilage. To understand the role of these factors in the pro-angiogenic secretome, we used neutralizing antibodies to functionally block them in the conditioned medium. Here, we observed a 1.4-fold increase of endothelial cell proliferation when blocking IHH and 1.5-fold by Serpin E1 blocking compared to unblocked control conditioned medium. Furthermore, endothelial migration was increased 1.9-fold by Serpin E1 blocking and 2.7-fold by IHH blocking. This suggests that the pro-angiogenic potential of chondrogenically differentiated BMSC secretome could be further augmented through inhibition of specific factors such as IHH and Serpin E1 identified as anti-angiogenic factors.

Allogeneic Chondrogenic Mesenchymal Stromal Cells Alter Helper T Cell Subsets in CD4+ Memory T Cells

Implantation of chondrogenically differentiated mesenchymal stromal cells (MSCs) leads to bone formation in vivo through the process of endochondral ossification. The use of allogeneic MSCs for this purpose may be a promising new approach to replace the current gold standard of bone regeneration. However, the success of using allogeneic cells depends on the interaction between the implanted cells and the host's endogenous immune cells. Th17 T cells and other CD4 helper T cell subtypes have been shown to negatively impact chondrogenesis, however, it is unclear how the interaction between these cells affects bone regeneration mediated by these cells. The aim of the current work was to assess the effect of chondrogenic MSC pellets on Th1, Th2, Th17, and regulatory T cells in vitro. Human MSCs were nonchondrogenic (-TGFβ3) and chondrogenically (+TGFβ3) differentiated for 7 or 21 days. Memory T cells (sorted from the CD4 population of peripheral blood mononuclear cells [PBMCs]), as well as total PBMCs were cocultured with allogeneic nonchondrogenic and chondrogenic MSC pellets for 3 days. Seven-day differentiated allogeneic nonchondrogenic and chondrogenic MSC pellets that were cocultured with memory T cells resulted in a significant increase in Th2 and a decrease in Th1 T cells. Furthermore, the co-culture of 21-day differentiated nonchondrogenic and chondrogenic MSC pellets with memory T cells resulted in a significant increase in Th2 and Th17 T cells, as well as a decrease in Th1 and regulatory T cells. Interleukin (IL)-6 was identified as a predominant cytokine involved in this interaction between allogeneic chondrogenically differentiated MSC pellets and memory CD4 T cells, with high levels of IL-6 being secreted in the supernatants of this cocultured condition. The findings of this study highlight the potential of chondrogenically differentiated MSC pellets to alter the ratio of Th1 and Th2 as well as Th17 and regulatory T cell subsets. Additional analysis investigating bone formation by chondrogenically differentiated MSCs in an allogeneic setting may identify a novel role of these T cell subsets in bone regeneration processes mediated by chondrogenically differentiated MSCs. Impact statement Allogeneic mesenchymal stromal cells (MSCs) have the potential to be an off-the-shelf treatment for bone repair. However, the lack of knowledge of the immune cells involved in this process has hampered the progression to the clinic. The current study has shown that allogeneic chondrogenic MSCs have the potential to skew the ratio of specific helper CD4 T cell subsets in vitro. This has now provided insight for future in vivo experiments to investigate the role of these T cell subsets in the early stages of bone regeneration mediated by allogeneic chondrogenic MSCs.

Cell-surface markers identify tissue resident multipotential stem/stromal cell subsets in synovial intimal and sub-intimal compartments with distinct chondrogenic properties

OBJECTIVE

Synovium contains multipotent progenitor/stromal cells (MPCs) with potential to participate in cartilage repair. Understanding the identity of these MPCs will allow their therapeutic potential to be fully exploited. Hence this study aimed to identify primary synovial MPCs and characterize them in the context of cartilage regeneration.

METHODS

Primary MPC/MPC-subset specific markers in synovium were identified by FACS analysis of uncultured cells. MPC-subsets from human synovium obtained from patients undergoing total knee arthroplasty were FACS sorted, cultured, immunophenotyped and chondrogenically differentiated. The anatomical localization of MPCs in synovium was examined using immunohistochemistry. Finally, the presence of these MPC subsets in healthy synovium obtained from human organ donors was examined.

RESULTS

A combination of CD45, CD31, CD73 and CD90 can isolate two distinct MPC-subsets in synovium. These MPC-subsets, freshly isolated from synovium, did not express CD45 or CD31, but expressed CD73. Additionally, a sub-population of CD73⁺ cells also expressed CD90. CD45^-CD31^-CD73⁺CD90^- cells were significantly more chondrogenic than CD45^-CD31^-CD73⁺CD90⁺ cells in the presence of TGFβ1. Interestingly, reduced chondrogenic ability of CD73⁺CD90⁺ cells could be reversed by the addition of BMP2, showing discrete chondrogenic factor requirements by distinct cell-subsets. In addition, these MPCs had distinct anatomical localization; CD73 was expressed both in intimal and sub-intimal region while CD90 was enriched in the sub-intimal region. We further demonstrated that these subsets are also present in healthy synovium.

CONCLUSIONS

We provide indications that primary MPCs in synovial intima and sub-intima are phenotypically and functionally distinct with different chondrogenic properties.

Allogeneic chondrogenically differentiated human bone marrow stromal cells do not induce dendritic cell maturation

Bone marrow stromal cell (BMSC)‐mediated endochondral bone formation may be a promising alternative to the current gold standards of autologous bone transplantation, in the development of novel methods for bone repair. Implantation of chondrogenically differentiated BMSCs leads to bone formation in vivo via endochondral ossification. The success of this bone formation in an allogeneic system depends upon the interaction between the implanted constructs and the host immune system. The current study investigated the effect of chondrogenically differentiated human bone marrow stromal cell (hBMSC) pellets on the maturation and function of dendritic cells (DCs) by directly coculturing bone forming chondrogenic hBMSC pellets and immature or lipopolysaccharide (LPS)‐matured DCs in vitro. Allogeneic chondrogenic hBMSC pellets did not affect the expression of CD80, CD86, or HLADR on immature or LPS‐matured DCs following 24, 48, or 72 hr of coculture. Furthermore, they did not induce or inhibit antigen uptake or migration of the DCs over time. IL‐6 was secreted by allogeneic chondrogenic hBMSC pellets in response to LPS‐matured DCs. Overall, this study has demonstrated that maturation of immature DCs was not influenced by allogeneic chondrogenic hBMSC pellets. This suggests that allogeneic chondrogenic hBMSC pellets do not stimulate immunogenic responses from DCs in vitro and are not expected to indirectly activate T cells via DCs. For this reason, allogeneic chondrogenic bone marrow stromal cell pellets are promising candidates for future tissue engineering strategies utilising allogeneic cells for bone repair.

Collagen type X is essential for successful mesenchymal stem cell-mediated cartilage formation and subsequent endochondral ossification

in tissue engineering, endochondral ossification (EO) is often replicated by chondrogenically differentiating mesenchymal stromal cells (MSCs) in vitro and achieving bone formation through in vivo implantation. The resulting marrow-containing bone constructs are promising as a treatment for bone defects. However, limited bone formation capacity has prevented them from reaching their full potential. This is further complicated since it is not fully understood how this bone formation is achieved. Acellular grafts derived from chondrogenically differentiated MSCs can initiate bone formation; however, which component within these decellularised matrices contribute to bone formation has yet to be determined. Collagen type X (COLX), a hypertrophy-associated collagen found within these constructs, is involved in matrix organisation, calcium binding and matrix vesicle compartmentalisation. However, the importance of COLX during tissue-engineered chondrogenesis and subsequent bone formation is unknown. The present study investigated the importance of COLX by shRNA-mediated gene silencing in primary MSCs. A significant knock-down of COLX disrupted the production of extracellular matrix key components and the secretion profile of chondrogenically differentiated MSCs. Following in vivo implantation, disrupted bone formation in knock-down constructs was observed. The importance of COLX was confirmed during both chondrogenic differentiation and subsequent EO in this tissue engineered setting.

Pediatric Mesenchymal Stem Cells Exhibit Immunomodulatory Properties Toward Allogeneic T and B Cells Under Inflammatory Conditions

Mesenchymal stem cells from pediatric patients (pMSCs) are an attractive cell source in regenerative medicine, due to their higher proliferation rates and better differentiation abilities compared to adult MSCs (aMSCs). We have previously characterized the immunomodulatory abilities of pMSCs on T cells under co-culture. It has also been reported that aMSCs can inhibit B cell proliferation and maturation under inflammatory conditions. In this study, we therefore aimed to clarify the immunomodulatory effect of pMSCs toward T and B cells in an inflammatory microenvironment. Bone marrow derived pMSCs were primed to simulate inflammatory conditions by exposure with 50 ng/mL of IFN-γ for 3 days. To analyze the interaction between pMSCs and T cells, CD3/CD28 stimulated peripheral blood mononuclear cells (PBMCs) were co-cultured with primed or unprimed pMSCs. To investigate B cell responses, quiescent B cells obtained from spleens by CD43 negative selection were stimulated with anti-IgM, anti-CD40, IL-2, and co-cultured with either IFN-γ primed or unprimed pMSC. pMSC phenotype, B and T cell proliferation, and B cell functionality were analyzed. Gene expression of indoleamine 2,3-dioxygenease (IDO), as well as the expression of HLA-ABC, HLA-DR and the co-stimulatory molecules CD80 and CD86 was upregulated on pMSCs upon IFN-γ priming. IFN-γ did not alter the immunomodulatory abilities of pMSCs upon CD4⁺ nor CD8⁺ stimulated T cells compared to unprimed pMSCs. IFN-γ primed pMSCs but not unprimed pMSCs strongly inhibited naïve (CD19⁺CD27⁻), memory (CD19⁺CD27⁺), and total B cell proliferation. Antibody-producing plasmablast (CD19⁺CD27^highCD38^high) formation and IgG production were also significantly inhibited by IFN-γ primed pMSCs compared to unprimed pMSCs. Collectively, these results show that pMSCs have immunomodulatory effects upon the adaptive immune response which can be potentiated by inflammatory stimuli. This knowledge is useful in regenerative medicine and allogeneic transplantation applications toward tailoring pMSCs function to best modulate the immune response for a successful implant engraftment and avoidance of a strong immune reaction.

Understanding tissue-engineered endochondral ossification; towards improved bone formation

Endochondral ossification (EO) is the process by which the long bones of the body form and has proven to be a promising method in tissue engineering for achieving cell-mediated bone formation. The present review centred on state-of-the-art research pertaining to mesenchymal stem cells (MSCs)-mediated endochondral bone formation, focusing on the role of donor cells, extracellular matrix and host immune cells during tissue-engineered bone formation. Possible research avenues to improve graft outcome and bone output were highlighted, as well as emerging research that, when applied to tissue-engineered bone grafts, offers new promise for improving the likelihood of such grafts transition from bench to bedside.

Calcifications in atherosclerotic plaques and impact on plaque biomechanics

The catastrophic mechanical rupture of an atherosclerotic plaque is the underlying cause of the majority of cardiovascular events. The infestation of vascular calcification in the plaques creates a mechanically complex tissue composite. Local stress concentrations and plaque tissue strength properties are the governing parameters required to predict plaque ruptures. Advanced imaging techniques have permitted insight into fundamental mechanisms driving the initiating inflammatory-driven vascular calcification of the diseased intima at the (sub-) micron scale and up to the macroscale. Clinical studies have potentiated the biomechanical relevance of calcification through the derivation of links between local plaque rupture and specific macrocalcification geometrical features. The clinical implications of the data presented in this review indicate that the combination of imaging, experimental testing, and computational modelling efforts are crucial to predict the rupture risk for atherosclerotic plaques. Specialised experimental tests and modelling efforts have further enhanced the knowledge base for calcified plaque tissue mechanical properties. However, capturing the temporal instability and rupture causality in the plaque fibrous caps remains elusive. Is it necessary to move our experimental efforts down in scale towards the fundamental (sub-) micron scales in order to interpret the true mechanical behaviour of calcified plaque tissue interactions that is presented on a macroscale in the clinic and to further optimally assess calcified plaques in the context of biomechanical modelling.

Follistatin Effects in Migration, Vascularization, and Osteogenesis in vitro and Bone Repair in vivo

The use of biomaterials and signaling molecules to induce bone formation is a promising approach in the field of bone tissue engineering. Follistatin (FST) is a glycoprotein able to bind irreversibly to activin A, a protein that has been reported to inhibit bone formation. We investigated the effect of FST in critical processes for bone repair, such as cell recruitment, osteogenesis and vascularization, and ultimately its use for bone tissue engineering. In vitro, FST promoted mesenchymal stem cell (MSC) and endothelial cell (EC) migration as well as essential steps in the formation and expansion of the vasculature such as EC tube-formation and sprouting. FST did not enhance osteogenic differentiation of MSCs, but increased committed osteoblast mineralization. In vivo, FST was loaded in an in situ gelling formulation made by alginate and recombinant collagen-based peptide microspheres and implanted in a rat calvarial defect model. Two FST variants (FST288 and FST315) with major differences in their affinity to cell-surface proteoglycans, which may influence their effect upon in vivo bone repair, were tested. In vitro, most of the loaded FST315 was released over 4 weeks, contrary to FST288, which was mostly retained in the biomaterial. However, none of the FST variants improved in vivo bone healing compared to control. These results demonstrate that FST enhances crucial processes needed for bone repair. Further studies need to investigate the optimal FST carrier for bone regeneration.

Novel In Situ Gelling Hydrogels Loaded with Recombinant Collagen Peptide Microspheres as a Slow-Release System Induce Ectopic Bone Formation

New solutions for large bone defect repair are needed. Here, in situ gelling slow release systems for bone induction are assessed. Collagen-I based Recombinant Peptide (RCP) microspheres (MSs) are produced and used as a carrier for bone morphogenetic protein 2 (BMP-2). The RCP-MSs are dispersed in three hydrogels: high mannuronate (SLM) alginate, high guluronate (SLG) alginate, and thermoresponsive hyaluronan derivative (HApN). HApN+RCP-MS forms a gel structure at 32 ºC or above, while SLM+RCP-MS and SLG+RCP-MS respond to shear stress displaying thixotropic behavior. Alginate formulations show sustained release of BMP-2, while there is minimal release from HApN. These formulations are injected subcutaneously in rats. SLM+RCP-MS and SLG+RCP-MS loaded with BMP-2 induce ectopic bone formation as revealed by X-ray tomography and histology, whereas HApN+RCP-MS do not. Vascularization occurs within all the formulations studied and is significantly higher in SLG+MS and HApN+RCP-MS than in SLM+RCP-MS. Inflammation (based on macrophage subset staining) decreases over time in both alginate groups, but increases in the HApN+RCP-MS condition. It is shown that a balance between inflammatory cell infiltration, BMP-2 release, and vascularization, achieved in the SLG+RCP-MS alginate condition, is optimal for the induction of de novo bone formation.

Epidermal growth factor receptor (EGFR) density may not be the only determinant for the efficacy of EGFR-targeted photoimmunotherapy in human head and neck cancer cell lines

OBJECTIVE

The aim of this study was to investigate the effects of targeted photoimmunotherapy (PIT) in vitro on cell lines with various expression levels of epidermal growth factor receptor (EGFR) using an anti-EGFR targeted conjugate composed of Cetuximab and IR700DX, phthalocyanine dye.

MATERIALS AND METHODS

Relative EGFR density and cell binding assay was conducted in three human head & neck cancer cell lines (scc-U2, scc-U8, and OSC19) and one reference cell line A431. After incubation with the conjugate for 1 or 24 hours, cellular uptake and localization were investigated by confocal laser scanning microscopy and quantified by image analysis. Cell survival was determined using the MTS assay and alamarBlue assay after PIT with a 690 nm laser to a dose of 7 J.cm^-2 (at 5 mW.cm^-2 ). The mode of cell death was examined with flow cytometry using apoptosis/necrosis staining by Annexin V/propidium iodide, together with immunoblots of anti-apoptotic Bcl-2 family proteins Bcl-2 and Bcl-xL.

RESULTS

A431 cells had the highest EGFR density followed by OSC19, and then scc-U2 and scc-U8. The conjugates were localized both on the surface and in the cytosol of the cells after 1- and 24-hour incubation. After 24-hour incubation the granular pattern was more pronounced and in a similar pattern of a lysosomal probe, suggesting that the uptake of conjugates by cells was via receptor-mediated endocytosis. The results obtained from the quantitative imaging analysis correlate with the level of EGFR expression. Targeted PIT killed scc-U8 and A431 cells efficiently; while scc-U2 and OSC19 were less sensitive to this treatment, despite having similar EGFR density, uptake and localization pattern. Scc-U2 cells showed less apoptotic cell dealth than in A431 after 24-hour targeted PIT. Immunoblots showed significantly higher expression of anti-apoptotic Bcl-2 and Bcl-xL proteins in scc-U2 cell lines compared to scc-U8.

CONCLUSION

Our study suggests that the effectiveness of EGFR targeted PIT is not only dependent upon EGFR density. Intrinsic biological properties of tumor cell lines also play a role in determining the efficacy of targeted PIT. We have shown that in scc-U2 cells this difference may be caused by differences in the apoptopic pathway. Lasers Surg. Med. 50:513-522, 2018. © 2018 Wiley Periodicals, Inc.

Isolating Pediatric Mesenchymal Stem Cells with Enhanced Expansion and Differentiation Capabilities

Mesenchymal stem cells/marrow stromal cells (MSCs) are attractive for applications ranging from research and development to use in clinical therapeutics. However, the most commonly studied MSCs, adult bone marrow MSCs (A-MSCs), are limited by significant donor variation resulting in inconsistent expansion rates and multilineage differentiation capabilities. We have recently obtained permission to isolate pediatric MSCs (P-MSCs) from surplus iliac crest bone chips. Here, we developed a simple and easily replicable isolation protocol yielding P-MSCs, which adhere to MSC defining guidelines. After confirming immunophenotypic marker expression, we compared expansion rates, senescence, morphology, and trilineage differentiation of P-MSCs to A-MSCs for multiple donors. We found P-MSCs have faster in vitro replication, consistently show significantly lower senescence, and are capable of more reproducible multilineage differentiation than A-MSCs. We, therefore, believe P-MSCs are a promising candidate for use in research applications and potentially as part of an allogeneic therapeutic treatment.

Injectable BMP-2 delivery system based on collagen-derived microspheres and alginate induced bone formation in a time- and dose-dependent manner

The aim of the current study was to reduce the clinically used supra-physiological dose of bone morphogenetic protein-2 (BMP-2) (usually 1.5 mg/mL), which carries the risk of adverse events, by using a more effective release system. A slow release system, based on an injectable hydrogel composed of BMP-2-loaded recombinant collagen-based microspheres and alginate, was previously developed. Time- and dose-dependent subcutaneous ectopic bone formation within this system and bone regeneration capacity in a calvarial defect model were investigated. BMP-2 doses of 10 µg, 3 µg and 1 µg per implant (50 µg/mL, 15 µg/mL and 5 µg/mL, respectively) successfully induced ectopic bone formation subcutaneously in rats in a time- and dose-dependent manner, as shown by micro-computed tomography (µCT) and histology. In addition, the spatio-temporal control of BMP-2 retention was shown for 4 weeks in vivo by imaging of fluorescently-labelled BMP-2. In the subcritical calvarial defect model, µCT revealed a higher bone volume for the 2 µg of BMP-2 per implant condition (50 µg/mL) as compared to the lower dose used (0.2 µg per implant, 5 µg/mL). Complete defect bridging was obtained with 50 µg/mL BMP-2 after 8 weeks. The BMP-2 concentration of 5 µg/mL was not sufficient to heal a calvarial defect faster than the empty defect or biomaterial control without BMP-2. Overall, this injectable BMP-2 delivery system showed promising results with 50 µg/mL BMP-2 in both the ectopic and calvarial rat defect models, underling the potential of this composite hydrogel for bone regeneration therapies.

NELL-1, HMGB1, and CCN2 Enhance Migration and Vasculogenesis, But Not Osteogenic Differentiation Compared to BMP2

Currently, autografts still represent the gold standard treatment for the repair of large bone defects. However, these are associated with donor-site morbidity and increased pain, cost, and recovery time. The ideal therapy would use biomaterials combined with bone growth factors to induce and instruct bone defect repair without the need to harvest patient tissue. In this line, bone morphogenetic proteins (BMPs) have been the most extensively used agents for clinical bone repair, but at supraphysiological doses that are not without risk. Because of the need to eliminate the risks of BMP2 use in vivo, we assessed the ability of three putative osteogenic factors, nel-like molecule type 1 (NELL-1), high mobility group box 1 (HMGB1), and CCN2, to enhance the essential processes for bone defect repair in vitro and compared them to BMP2. Although it has been reported that NELL-1, HMGB1, and CCN2 play a role in bone formation, less is known about the contribution of these proteins to the different events involved, such as cell migration, osteogenesis, and vasculogenesis. In this study, we investigated the effects of different doses of NELL-1, HMGB, CCN2, and BMP2 on these three processes as a model for the recruitment and differentiation of resident cells in the in vivo bone defect repair situation, using cells of human origin. Our data demonstrated that NELL-1, HMGB1, and CCN2 significantly induced mesenchymal stem cell migration (from 1.58-fold increase compared to control), but BMP2 did not. Interestingly, only BMP2 increased osteogenesis in marrow stromal cells, whereas it inhibited osteogenesis in preosteoblasts. Moreover, the four proteins studied promoted significantly endothelial cell migration, reaching a maximum of 2.4-fold increase compared to control, and induced formation of tube-like structures. NELL-1, HMGB1, and CCN2 had these effects at relatively low doses compared to BMP2. This work indicates that NELL-1, HMGB1, and CCN2 might enhance bone defect healing via the recruitment of endogenous cells and induction of vascularization and act via different processes than BMP2.

The antiviral effects of RSV fusion inhibitor, MDT-637, on clinical isolates, vs its achievable concentrations in the human respiratory tract and comparison to ribavirin

Background

Respiratory syncytial virus (RSV) viral load and disease severity associate, and the timing of viral load and disease run in parallel. An antiviral must be broadly effective against the natural spectrum of RSV genotypes and must attain concentrations capable of inhibiting viral replication within the human respiratory tract.

Objectives

We evaluated a novel RSV fusion inhibitor, MDT‐637, and compared it with ribavirin for therapeutic effect in vitro to identify relative therapeutic doses achievable in humans.

Method

MDT‐637 and ribavirin were co‐incubated with RSV in HEp‐2 cells. Quantitative PCR assessed viral concentrations; 50% inhibitory concentrations (IC₅₀) were compared to achievable human MDT‐637 and ribavirin peak and trough concentrations.

Results and conclusions

The IC₅₀ for MDT‐637 and ribavirin (against RSV‐A Long) was 1.42 and 16 973 ng/mL, respectively. The ratio of achievable peak respiratory secretion concentration to IC₅₀ was 6041‐fold for MDT‐637 and 25‐fold for aerosolized ribavirin. The ratio of trough concentration to IC₅₀ was 1481‐fold for MDT‐637 and 3.29‐fold for aerosolized ribavirin. Maximal peak and trough levels of oral or intravenous ribavirin were significantly lower than their IC₅₀s. We also measured MDT‐637 IC₅₀s in 3 lab strains and 4 clinical strains. The IC₅₀s ranged from 0.36 to 3.4 ng/mL. Achievable human MDT‐637 concentrations in respiratory secretions exceed the IC₅₀s by factors from hundreds to thousands of times greater than does ribavirin. Furthermore, MDT‐637 has broad in vitro antiviral activity on clinical strains of different RSV genotypes and clades. Together, these data imply that MDT‐637 may produce a superior clinical effect compared to ribavirin on natural RSV infections.

Activin and Nodal Are Not Suitable Alternatives to TGFβ for Chondrogenic Differentiation of Mesenchymal Stem Cells

Objective Previously, we demonstrated the importance of transforming growth factor-β (TGFβ)-activated SMAD2/3 signaling in chondrogenesis of bone marrow-derived mesenchymal stem cells (BMSCs). However, TGFβ also signals via the SMAD1/5/9 pathway, which is known to induce terminal differentiation of BMSCs. In this study, we investigated whether other SMAD2/3-activating ligands, Activin and Nodal, can induce chondrogenic differentiation of BMSCs without inducing terminal differentiation. Design Activation of SMAD2/3 signaling and chondrogenesis were evaluated in human BMSCs ( N = 3 donors) stimulated with TGFβ, Activin, or Nodal. SMAD2/3 activation was assessed by determining phosphorylated-SMAD2 (pSMAD2) protein levels and SMAD2/3-target gene expression of SERPINE1. Chondrogenesis was determined by ACAN and COL2A1 transcript analysis and histological examination of proteoglycans and collagen type II. Results Both Activin and TGFβ enhanced pSMAD2 and SERPINE1 expression compared to the control condition without growth factors, demonstrating activated SMAD2/3 signaling. pSMAD2 and SERPINE1 had a higher level of expression following stimulation with TGFβ than with Activin, while Nodal did not activate SMAD2/3 signaling. Of the 3 ligands tested, only TGFβ induced chondrogenic differentiation as shown by strongly increased transcript levels of ACAN and COL2A1 and positive histological staining of proteoglycans and collagen type II. Conclusions Even with concentrations up to 25 times higher than that of TGFβ, Activin and Nodal do not induce chondrogenic differentiation of BMSCs; thus, neither of the 2 ligands is an interesting alternative candidate for TGFβ to induce chondrogenesis without terminal differentiation. To obtain stable cartilage formation by BMSCs, future studies should decipher how TGFβ-induced terminal differentiation can be prevented.

Mesenchymal stem cell-mediated endochondral ossification utilising micropellets and brief chondrogenic priming

With limited autologous and donor bone graft availability, there is an increasing need for alternative graft substitutes. We have previously shown that chondrogenically priming mesenchymal stem cell (MSC) pellets for 28 d in vitro will reproducibly result in endochondral bone formation after in vivo implantation. However, pellet priming time for clinical applications is quite extensive. A micropellet (μpellet)-fibrin construct was developed and coupled, with a shorter priming period, determined by an in vitro time course experiment. In vitro data showed expression of chondrogenic genes and matrix production after 7 d of chondrogenic priming, indicating that briefer priming could possibly be used to induce bone formation in vivo. 7 and 28 d primed pellet, pellet-fibrin and μpellet-fibrin constructs were cultured for in vitro analysis and implanted subcutaneously for 8 weeks into nude mice. μpellet-fibrin constructs, cultured in vitro for 7 or 28 d, produced comparable bone to standard pellets in vivo. MSC-mediated bone formation was achieved following only 7 d of in vitro priming. Bone formation in vivo appeared to be influenced by overall matrix production pre-implantation. Given this short priming time and the injectable nature of the μpellet-fibrin constructs, this approach might be further developed as an injectable bone substitute, leading to a minimally-invasive treatment option, which would allow for tailored filling of bone defects.