Lung delivery of MSCs expressing anti-cancer protein TRAIL visualised with 89Zr-oxine PET-CT

Improved tumour delivery of iron oxide nanoparticles for magnetic hyperthermia therapy of melanoma via ultrasound guidance and 111In SPECT quantification

Magnetic field hyperthermia relies on the intra-tumoural delivery of magnetic nanoparticles by interstitial injection, followed by their heating on exposure to a remotely-applied alternating magnetic field (AMF). This offers a potential sole or adjuvant route to treating drug-resistant tumours for which no alternatives are currently available. However, two challenges in nanoparticle delivery currently hinder the effective clinical translation of this technology: obtaining enough magnetic material within the tumour to enable sufficient heating; and doing this accurately to limit or avoid damage to surrounding healthy tissue. A further complication is the lack of established methods to non-invasively quantify nanoparticle biodistribution, which is necessary to evaluate the performance of improved delivery strategies. Here we employ 111In radiolabelling and single-photon emission computed tomography (SPECT) to non-invasively quantify distribution of a clinical grade iron-oxide-based nanoparticle in a mouse model of melanoma. We show that compared to manual injection, ultrasound guided delivery together with syringe-pump-controlled infusion improves both the nanoparticle concentration within the tumour, and the accuracy of delivery - reducing off-target peri-tumoural delivery. Following AMF heating, injected melanomas shrank significantly compared to non-injected controls, validating therapeutic efficacy. Systemic off-target delivery was quantified and extrapolated to predict off-target energy absorbance within safe limits for the main sites of background accumulation. With many nanoparticle-based therapies currently in development for cancer, this image-guided delivery strategy has wide potential impact beyond the field of magnetic hyperthermia. Future use in representative patient cohorts would also be enabled by the high clinical availability of both SPECT and ultrasound imaging.

CT-Visible Microspheres Enable Whole-Body In Vivo Tracking of Injectable Tissue Engineering Scaffolds

Targeted delivery and retention are essential requirements for implantable tissue-engineered products. Non-invasive imaging methods that can confirm location, retention, and biodistribution of transplanted cells attached to implanted tissue engineering scaffolds will be invaluable for the optimization and enhancement of regenerative therapies. To address this need, an injectable tissue engineering scaffold consisting of highly porous microspheres compatible with transplantation of cells is modified to contain the computed tomography (CT) contrast agent barium sulphate (BaSO4). The trackable microspheres show high x-ray absorption, with contrast permitting whole-body tracking. The microspheres are cellularized with GFP+ Luciferase+ mesenchymal stem cells and show in vitro biocompatibility. In vivo, cellularized BaSO4-loaded microspheres are delivered into the hindlimb of mice where they remain viable for 14 days. Co-registration of 3D-bioluminescent imaging and µCT reconstructions enable the assessment of scaffold material and cell co-localization. The trackable microspheres are also compatible with minimally-invasive delivery by ultrasound-guided transthoracic intramyocardial injections in rats. These findings suggest that BaSO4-loaded microspheres can be used as a novel tool for optimizing delivery techniques and tracking persistence and distribution of implanted scaffold materials. Additionally, the microspheres can be cellularized and have the potential to be developed into an injectable tissue-engineered combination product for cardiac regeneration.

Mesenchymal stromal cells and CAR-T cells in regenerative medicine: The homing procedure and their effective parameters

Mesenchymal stromal cells (MSCs) and chimeric antigen receptor (CAR)-T cells are two core elements in cell therapy procedures. MSCs have significant immunomodulatory effects that alleviate inflammation in the tissue regeneration process, while administration of specific chemokines and adhesive molecules would primarily facilitate CAR-T cell trafficking into solid tumors. Multiple parameters affect cell homing, including the recipient's age, the number of cell passages, proper cell culture, and the delivery method. In addition, several chemokines are involved in the tumor microenvironment, affecting the homing procedure. This review discusses parameters that improve the efficiency of cell homing and significant cell therapy challenges. Emerging comprehensive mechanistic strategies such as non-systemic and systemic homing that revealed a significant role in cell therapy remodeling were also reviewed. Finally, the primary implications for the development of combination therapies that incorporate both MSCs and CAR-T cells for cancer treatment were discussed.

Biodistribution of Mesenchymal Stromal Cells Labeled with [89Zr]Zr-Oxine in Local Radiation Injuries in Laboratory Animals

BACKGROUND

Tracking the migration pathways of living cells after their introduction into a patient's body is a topical issue in the field of cell therapy. Questions related to studying the possibility of long-term intravital biodistribution of mesenchymal stromal cells in the body currently remain open.

METHODS

Forty-nine laboratory animals were used in the study. Modeling of local radiation injuries was carried out, and the dynamics of the distribution of mesenchymal stromal cells labeled with [89Zr]Zr-oxine in the rat body were studied.

RESULTS

the obtained results of the labelled cell distribution allow us to assume that this procedure could be useful for visualization of local radiation injury using positron emission tomography. However, further research is needed to confirm this assumption.

CONCLUSIONS

intravenous injection leads to the initial accumulation of cells in the lungs and their subsequent redistribution to the liver, spleen, and kidneys. When locally injected into tissues, mesenchymal stromal cells are not distributed systemically in significant quantities.

Fate and Efficacy of Engineered Allogeneic Stem Cells Targeting Cell Death and Proliferation Pathways in Primary and Brain Metastatic Lung Cancer

Primary and metastatic lung cancer is a leading cause of cancer-related death and novel therapies are urgently needed. Epidermal growth factor receptor (EGFR) and death receptor (DR) 4/5 are both highly expressed in primary and metastatic non-small cell lung cancer (NSCLC); however, targeting these receptors individually has demonstrated limited therapeutic benefit in patients. In this study, we created and characterized diagnostic and therapeutic stem cells (SC), expressing EGFR-targeted nanobody (EV) fused to the extracellular domain of death DR4/5 ligand (DRL) (EVDRL) that simultaneously targets EGFR and DR4/5, in primary and metastatic NSCLC tumor models. We show that EVDRL targets both cell surface receptors, and induces caspase-mediated apoptosis in a broad spectrum of NSCLC cell lines. Utilizing real-time dual imaging and correlative immunohistochemistry, we show that allogeneic SCs home to tumors and when engineered to express EVDRL, alleviate tumor burden and significantly increase survival in primary and brain metastatic NSCLC. This study reports mechanistic insights into simultaneous targeting of EGFR- and DR4/5 in lung tumors and presents a promising approach for translation into the clinical setting.

Theranostic chimeric antigen receptor (CAR)-T cells: Insight into recent trends and challenges in solid tumors

Cell therapy has reached significant milestones in various life-threatening diseases, including cancer. Cell therapy using fluorescent and radiolabeled chimeric antigen receptor (CAR)-T cell is a successful strategy for diagnosing or treating malignancies. Since cell therapy approaches have different results in cancers, the success of hematological cancers has yet to transfer to solid tumor therapy, leading to more casualties. Therefore, there are many areas for improvement in the cell therapy platform. Understanding the therapeutic barriers associated with solid cancers through cell tracking and molecular imaging may provide a platform for effectively delivering CAR-T cells into solid tumors. This review describes CAR-T cells' role in treating solid and non-solid tumors and recent advances. Furthermore, we discuss the main obstacles, mechanism of action, novel strategies and solutions to overcome the challenges from molecular imaging and cell tracking perspectives.

In Vivo Fate of CXCR2-Overexpressing Mesenchymal Stromal/Stem Cells in Pulmonary Diseases Monitored by Near-Infrared Region 2 Imaging

Lung-associated diseases pose a huge threat to human society. Mesenchymal stromal/stem cells (MSCs) hold great promise in the treatment of pulmonary diseases through cell transdifferentiation, paracrine factors, immune regulation, EV secretion, and drug loading. However, intravenous injection of MSCs often resulted in limited lesion tropism and apparent off-target accumulation. The IL-8-CXCR1/2 chemokine axis has been shown to be involved in progression of diseases including lung cancer and acute lung injury (ALI). Herein, we took advantage of this chemokine axis to enhance the homing of MSCs to cancerous and inflammation lesions. The in vivo distribution of MSCs was further monitored real-time by near-infrared region 2 (NIR-II) imaging owing to its outstanding performance in deep tissue imaging. Specifically, a new high-brightness D-A-D NIR-II dye, LJ-858, was synthesized and coprecipitated with a poly(d,l-lactic acid) polymer to form LJ-858 nanoparticles (NPs) with a relative quantum yield of 14.978%. LJ-858 NPs can efficiently label MSCs, and the NIR-II signal can be stable for 14 days without compromising the cell viability. Subcutaneous tracking of labeled MSCs showed no significant decline of NIR-II intensity within 24 h. The enhanced tropism of CXCR2-overexpressing MSCs to A549 tumor cells and the inflamed lung tissue was demonstrated through transwell models. The in vivo and ex vivo NIR-II imaging results further validated the significantly enhanced lesion retention of MSC^CXCR2 in the lung cancer and ALI models. Taken together, this work reported a robust strategy to enhance the pulmonary disease tropism by the IL-8-CXCR1/2 chemokine axis. In addition, in vivo distribution of MSCs was successfully visualized by NIR-II imaging, which provides more insights into optimizing protocols for MSC-based therapies in the future.

Implant Imaging: Perspectives of Nuclear Imaging in Implant, Biomaterial, and Stem Cell Research

Until now, very few efforts have been made to specifically trace, monitor, and visualize implantations, artificial organs, and bioengineered scaffolds for tissue engineering in vivo. While mainly X-Ray, CT, and MRI methods have been used for this purpose, the applications of more sensitive, quantitative, specific, radiotracer-based nuclear imaging techniques remain a challenge. As the need for biomaterials increases, so does the need for research tools to evaluate host responses. PET (positron emission tomography) and SPECT (single photon emission computer tomography) techniques are promising tools for the clinical translation of such regenerative medicine and tissue engineering efforts. These tracer-based methods offer unique and inevitable support, providing specific, quantitative, visual, non-invasive feedback on implanted biomaterials, devices, or transplanted cells. PET and SPECT can improve and accelerate these studies through biocompatibility, inertivity, and immune-response evaluations over long investigational periods at high sensitivities with low limits of detection. The wide range of radiopharmaceuticals, the newly developed specific bacteria, and the inflammation of specific or fibrosis-specific tracers as well as labeled individual nanomaterials can represent new, valuable tools for implant research. This review aims to summarize the opportunities of nuclear-imaging-supported implant research, including bone, fibrosis, bacteria, nanoparticle, and cell imaging, as well as the latest cutting-edge pretargeting methods.

Fate of intravenously administered umbilical cord mesenchymal stromal cells and interactions with the host's immune system

Mesenchymal stromal cells (MSCs) are multipotent cells showing promise in pre-clinical studies and currently used in many clinical trials. The regenerative potential of MSCs is mediated, at least in part, by direct and indirect immunomodulatory processes. However, the mechanism of action is not fully understood yet, and there are still concerns about possible undesired negative effects associated with the administration of living cells. In this study, we (i) compare the long-term fate and safety of umbilical cord (UC-)MSCs administered to immunocompetent and immunocompromised (severe combined immunodeficient (SCID) and non-obese diabetic (NOD)/SCID) animals, and (ii) investigate the immunological response of the host to the administered cells. Intravenous administration of firefly luciferase expressing UC-MSCs revealed that the cells get trapped in the lungs of both immunocompetent and immunocompromised animals, with > 95% of the cells disappearing within 72 h after administration. In 27% of the SCID and 45% of the NOD/SCID, a small fraction of the cells lived up to day 14 but in most cases they all disappeared earlier. One NOD/SCID mouse showed a weak signal up to day 31. Immunocompetent mice displayed elevated percentages of neutrophils in the lungs, the blood, and the spleen 2 h after the administration of the cells. The concentration of neutrophil chemoattractants (MCP1, CCL7, Gro-α and IP-10) were also increased in the plasma of the animals 2 h after the administration of the MSCs. Our results suggest that although the UC-MSCs are short-lived in mice, they still result in an immunological response that might contribute to a therapeutic effect.

Complementary early-phase magnetic particle imaging and late-phase positron emission tomography reporter imaging of mesenchymal stem cells in vivo

Stem cell-based therapies have demonstrated significant potential in clinical applications for many debilitating diseases. The ability to non-invasively and dynamically track the location and viability of stem cells post administration could provide important information on individual patient response and/or side effects. Multi-modal cell tracking provides complementary information that can offset the limitations of a single imaging modality to yield a more comprehensive picture of cell fate. In this study, mesenchymal stem cells (MSCs) were engineered to express human sodium iodide symporter (NIS), a clinically relevant positron emission tomography (PET) reporter gene, as well as labeled with superparamagnetic iron oxide nanoparticles (SPIOs) to allow for detection with magnetic particle imaging (MPI). MSCs were additionally engineered with a preclinical bioluminescence imaging (BLI) reporter gene for comparison of BLI cell viability data to both MPI and PET data over time. MSCs were implanted into the hind limbs of immunocompromised mice and imaging with MPI, BLI and PET was performed over a 30-day period. MPI showed sensitive detection that steadily declined over the 30-day period, while BLI showed initial decreases followed by later rapid increases in signal. The PET signal of MSCs was significantly higher than the background at later timepoints. Early-phase imaging (day 0-9 post MSC injections) showed correlation between MPI and BLI data (R² = 0.671), while PET and BLI showed strong correlation for late-phase (day 10-30 post MSC injections) imaging timepoints (R² = 0.9817). We report the first use of combined MPI and PET for cell tracking and show the complementary benefits of MPI for sensitive detection of MSCs early after implantation and PET for longer-term measurements of cell viability.

Positron Emission Tomography-Computed Tomography Imaging of Selective Lobar Delivery of Stem Cells in Ex Vivo Lung Model of Mechanical Ventilation

Introduction: The delivery of cell therapies may be an important frontier to treat different respiratory diseases in the near future. However, the cell size, delivery conditions, cell viability, and effect in the pulmonary function are critical factors. We performed a proof-of-concept experiment using ex vivo lungs and novel subglottic airway device that allows for selective lobar isolation and administration of drugs and biologics in liquid solution deep into the lung tissues, while simultaneously ventilating the rest of the lung lobes. Methods: We used radiolabeled cells and positron emission tomography-computed tomography (PET-CT) imaging to demonstrate the feasibility of high-yield cell delivery to a specifically targeted lobe. This study proposes an alternative delivery method of live cells labeled with radioactive isotope into the lung parenchyma and tracks the cell delivery using PET-CT imaging. The technique combines selective lobar isolation and lobar infusion to carry large particles distal to the trachea, subtending bronchial segments and reaching alveoli in targeted regions. Results: The solution with cells and carrier achieved a complete and homogeneous lobar distribution. An increase in tissue density was shown on the computed tomography (CT) scan, and the PET-CT imaging demonstrated retention of the activity at central, peripheral lung parenchyma, and pleural surface. The increase in CT density and metabolic activity of the isotope was restricted to the desired lobe only without leak to other lobes. Conclusion: The selective lobe delivery is targeted and imaging-guided by bronchoscopy and CT to a specific diseased lobe during mechanical ventilation. The feasibility of high-yield cell delivery demonstrated in this study will lead to the development of potential novel therapies that contribute to lung health.

Evaluation of different 89Zr-labeled synthons for direct labeling and tracking of white blood cells and stem cells in healthy athymic mice

Cell based therapies are evolving as an effective new approach to treat various diseases. To understand the safety, efficacy, and mechanism of action of cell-based therapies, it is imperative to follow their biodistribution noninvasively. Positron-emission-tomography (PET)-based non-invasive imaging of cell trafficking offers such a potential. Herein, we evaluated and compared three different ready-to-use direct cell radiolabeling synthons, [⁸⁹Zr]Zr-DFO-Bn-NCS, [⁸⁹Zr]Zr-Hy₃ADA⁵-NCS, and [⁸⁹Zr]Zr-Hy₃ADA⁵-SA for PET imaging-based trafficking of white blood cells (WBCs) and stem cells (SCs) up to 7 days in athymic nude mice. We compared the degree of ⁸⁹Zr complexation and percentage of cell radiolabeling efficiencies with each. All three synthons, [⁸⁹Zr]Zr-DFO-Bn-NCS, [⁸⁹Zr]Zr-Hy₃ADA⁵-NCS, and [⁸⁹Zr]Zr-Hy₃ADA⁵-SA, were successfully prepared, and used for radiolabeling of WBCs and SCs. The highest cell radiolabeling yield was found for [⁸⁹Zr]Zr-DFO-Bn-NCS, followed by [⁸⁹Zr]Zr-Hy₃ADA⁵-NCS, and [⁸⁹Zr]Zr-Hy₃ADA⁵-SA. In terms of biodistribution, WBCs radiolabeled with [⁸⁹Zr]Zr-DFO-Bn-NCS or [⁸⁹Zr]Zr-Hy₃ADA⁵-NCS, were primarily accumulated in liver and spleen, whereas SCs radiolabeled with [⁸⁹Zr]Zr-DFO-Bn-NCS or [⁸⁹Zr]Zr-Hy₃ADA⁵-NCS were found in lung, liver and spleen. A high bone uptake was observed for both WBCs and SCs radiolabeled with [⁸⁹Zr]Zr-Hy₃ADA⁵-SA, suggesting in-vivo instability of [⁸⁹Zr]Zr-Hy₃ADA⁵-SA synthon. This study offers an appropriate selection of ready-to-use radiolabeling synthons for noninvasive trafficking of WBCs, SCs and other cell-based therapies.

Prodigious therapeutic effects of combining mesenchymal stem cells with magnetic nanoparticles

Mesenchymal stem cells (MSCs) have gained wide-ranging reputation in the medical research community due to their promising regenerative abilities. MSCs can be isolated from various resources mostly bone marrow, Adipose tissues and Umbilical cord. Huge advances have been achieved in comprehending the possible mechanisms underlying the therapeutic functions of MSCs. Despite the proven role of MSCs in repairing and healing of many disease modalities, many hurdles hinder the transferring of these cells in the clinical settings. Among the most reported problems encountering MSCs therapy in vivo are loss of tracking signal post-transplantation, insufficient migration, homing and engraftment post-infusion, and undesirable differentiation at the site of injury. Magnetic nanoparticles (MNPs) have been used widely for various biomedical applications. MNPs have a metallic core stabilized by an outer coating material and their magnetic properties can be modulated by an external magnetic field. These magnetic properties of MNPs were found to enhance the quality of diagnostic imaging procedures and can be used to create a carrying system for targeted delivery of therapeutic substances mainly drug, genes and stem cells. Several studies highlighted the advantageous outcomes of combining MSCs with MNPs in potentiating their tracking, monitoring, homing, engraftment and differentiation. In this review, we will discuss the role of MNPs in promoting the therapeutic profile of MSCs which may improve the success rate of MSCs transplantation and solve many challenges that delay their clinical applicability.

Biodistribution of 89Zr-oxine-labeled human bone marrow-derived mesenchymal stem cells by micro-PET/computed tomography imaging in Sprague-Dawley rats

PURPOSE

To develop a method for labeling human bone marrow mesenchymal stem cells (hMSCs) with 89Zr-oxine to characterize the biodistribution characteristics of hMSCs in normal Sprague-Dawley (SD) rats in real-time by micro-PET-computed tomography (micro-PET/CT) imaging.

METHODS

89Zr-oxine complex was synthesized from 89Zr-oxalate and 8-hydroxyquinoline (oxine). After hMSCs were labeled with the 89Zr-oxine complex, the radioactivity retention, viability, proliferation, apoptosis, differentiation, morphology, and phenotype of labeled cells were assessed. The biodistribution of 89Zr-oxine-labeled hMSCs in SD rats was tracked in real-time by micro-PET/CT imaging.

RESULTS

The cell labeling efficiency was 52.6 ± 0.01%, and 89Zr-oxine was stably retained in cells (66.7 ± 0.9% retention on 7 days after labeling). Compared with the unlabeled hMSCs, 89Zr-oxine labeling did not affect the biological characteristics of cells. Following intravenous administration in SD rats, labeled hMSCs mainly accumulated in the liver (7.35 ± 1.41% ID/g 10 days after labeling, n = 6) and spleen (8.48 ± 1.20% ID/g 10 days after labeling, n = 6), whereas intravenously injected 89Zr-oxalate mainly accumulated in the bone (4.47 ± 0.35% ID/g 10 days after labeling, n = 3).

CONCLUSION

89Zr-oxine labeling and micro-PET/CT imaging provide a useful and non-invasive method of assessing the biodistribution of cell therapy products in SD rats. The platform provides a foundation for us to further understand the mechanism of action and migration dynamics of cell therapy products.

Unveiling the improved targeting migration of mesenchymal stem cells with CXC chemokine receptor 3-modification using intravital NIR-II photoacoustic imaging

Background

Therapy with genetically modified mesenchymal stem cells (MSCs) has clinical translation promise. Optimizing the targeting migratory ability of MSCs relies on accurate imaging of the distribution and extravasation kinetics of MSCs, and the corresponding imaging results could be used to predict therapeutic outcomes and guide the optimization of the treatment program. Among the different imaging modalities, second near-infrared (NIR-II) optical-resolution photoacoustic microscopy (OR-PAM) has merits, including a fine resolution, a deep penetration, a high sensitivity, and a large signal-to-background ratio. It would be an ideal candidate for precise monitoring of MSCs, although it has not been tested for this purpose so far.

Results

Penetrating peptide-decorated conjugated polymer nanoparticles (TAT-CPNPs) with strong NIR-II absorbance were used to label chemokine-receptor genetically modified MSCs, which were subsequently evaluated under intravital NIR-II OR-PAM regarding their targeting migratory ability. Based on the upregulation of chemokine (C-X-C motif) ligand 10 in the inflamed ears of contact hypersensitivity mice, MSCs with overexpression of corresponding receptor, chemokine (C-X-C motif) receptor 3 (Cxcr3) were successfully generated (MSC^Cxcr3). TAT-CPNPs labeling enabled NIR-II photoacoustic imaging to discern MSC^Cxcr3 covered by 1.2 cm of chicken breast tissue. Longitudinal OR-PAM imaging revealed enhanced inflammation-targeting migration of MSC^Cxcr3 over time attributed to Cxcr3 gene modification, which was further validated by histological analysis.

Conclusions

TAT-CPNPs-assisted NIR-II PA imaging is promising for monitoring distribution and extravasation kinetics of MSCs, which would greatly facilitate optimizing MSC-based therapy.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01513-7.

Direct Cell Radiolabeling for in Vivo Cell Tracking with PET and SPECT Imaging

The arrival of cell-based therapies is a revolution in medicine. However, its safe clinical application in a rational manner depends on reliable, clinically applicable methods for determining the fate and trafficking of therapeutic cells in vivo using medical imaging techniques─known as in vivo cell tracking. Radionuclide imaging using single photon emission computed tomography (SPECT) or positron emission tomography (PET) has several advantages over other imaging modalities for cell tracking because of its high sensitivity (requiring low amounts of probe per cell for imaging) and whole-body quantitative imaging capability using clinically available scanners. For cell tracking with radionuclides, ex vivo direct cell radiolabeling, that is, radiolabeling cells before their administration, is the simplest and most robust method, allowing labeling of any cell type without the need for genetic modification. This Review covers the development and application of direct cell radiolabeling probes utilizing a variety of chemical approaches: organic and inorganic/coordination (radio)chemistry, nanomaterials, and biochemistry. We describe the key early developments and the most recent advances in the field, identifying advantages and disadvantages of the different approaches and informing future development and choice of methods for clinical and preclinical application.

Whole-Body Imaging to Assess Cell-Based Immunotherapy: Preclinical Studies with an Update on Clinical Translation

In the past decades, immunotherapies against cancers made impressive progress. Immunotherapy includes a broad range of interventions that can be separated into two major groups: cell-based immunotherapies, such as adoptive T cell therapies and stem cell therapies, and immunomodulatory molecular therapies such as checkpoint inhibitors and cytokine therapies. Genetic engineering techniques that transduce T cells with a cancer-antigen-specific T cell receptor or chimeric antigen receptor have expanded to other cell types, and further modulation of the cells to enhance cancer targeting properties has been explored. Because cell-based immunotherapies rely on cells migrating to target organs or tissues, there is a growing interest in imaging technologies that non-invasively monitor transferred cells in vivo. Here, we review whole-body imaging methods to assess cell-based immunotherapy using a variety of examples. Following a review of preclinically used cell tracking technologies, we consider the status of their clinical translation.

Exosomes derived from stem cells of human deciduous exfoliated teeth inhibit angiogenesis in vivo and in vitro via the transfer of miR-100-5p and miR-1246

Background

Anti-angiogenic therapy has been shown to be a promising strategy for anti-tumor treatment. Increasing evidence indicates that tumor angiogenesis is affected by exosomes that are secreted by mesenchymal stem cells (MSCs), but whether exosomes derived from MSCs suppress or promote angiogenesis remain paradoxical. The purpose of this study focused on understanding the potential role of exosomes derived from stem cells of human deciduous exfoliated teeth (SHED-Exos) in regulating angiogenesis and the underlying molecular mechanism.

Methods

Exosomes were isolated from supernatants of SHED cells using an exosome purification kit and were characterized by transmission electron microscopy, nanoparticle tracking analysis and western blot analysis. Cell Counting Kit-8, flow cytometric assays, western blots, wound healing and transwell migration assays were performed to characterize the roles of SHED-Exos on cell proliferation, apoptosis and migration of human umbilical vein endothelial cells (HUVECs). The anti-angiogenic activity of SHED-Exos was assessed via a tube formation assay of endothelial cells and angiogenesis-related factors were analyzed by western blotting. In vivo, we used the chick chorioallantoic membrane (CAM) assay and an oral squamous cell carcinoma (OSCC) xenograft transplantation model with nude mice that received multi-point injections at three-day intervals to evaluate the effects on angiogenesis. Furthermore, the sequencing of microRNAs (miRNAs) in SHED-Exos was performed to investigate the underlying anti-angiogenic mechanism.

Results

The results showed that SHED-Exos inhibit cell proliferation and migration and induce apoptosis in HUVECs. SHED-Exos suppress the tube-like structure formation of HUVECs in vitro. SHED-Exos downregulate several angiogenesis-related factors, including VEGFA, MMP-9 and ANGPT1. In vivo, the chick CAM assay verified that treatment with SHED-Exos inhibits micro-vascular formation, and importantly, significantly reduces the micro-vascular formation of tumors generated from xenografted OSCC cells, which was associated with the inhibition of tumor growth in vivo. Mechanistically, our data suggested that SHED-Exos are enriched with miR-100-5p and miR-1246 and are transferred to endothelial cells, which results in decreased tube formation via the down-regulation of VEGFA expression.

Conclusions

These results demonstrate that SHED-Exos inhibit angiogenesis in vitro and in vivo, which suggests that SHED-Exos could potentially serve as a novel and effective therapeutic approach for anti-angiogenic treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02764-9.

Mesenchymal Stem Cell-Based COVID-19 Therapy: Bioengineering Perspectives

The novel pathogenic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19). Mesenchymal stem cells (MSCs) are currently utilized in clinics for pulmonary inflammatory diseases, including acute respiratory distress syndrome and acute lung injury. Given that MSCs offer a promising treatment against COVID-19, they are being used against COVID-19 in more than 70 clinical trials with promising findings. Genetically engineered MSCs offer promising therapeutic options in pulmonary diseases. However, their potential has not been explored yet. In this review, we provide perspectives on the functionally modified MSCs that can be developed and harnessed for COVID-19 therapy. Options to manage the SARS-CoV-2 infection and its variants using various bioengineering tools to increase the therapeutic efficacy of MSCs are highlighted.

Optimisation of the Synthesis and Cell Labelling Conditions for [89Zr]Zr-oxine and [89Zr]Zr-DFO-NCS: a Direct In Vitro Comparison in Cell Types with Distinct Therapeutic Applications

BACKGROUND

There is a need to better characterise cell-based therapies in preclinical models to help facilitate their translation to humans. Long-term high-resolution tracking of the cells in vivo is often impossible due to unreliable methods. Radiolabelling of cells has the advantage of being able to reveal cellular kinetics in vivo over time. This study aimed to optimise the synthesis of the radiotracers [89Zr]Zr-oxine (8-hydroxyquinoline) and [89Zr]Zr-DFO-NCS (p-SCN-Bn-Deferoxamine) and to perform a direct comparison of the cell labelling efficiency using these radiotracers.

PROCEDURES

Several parameters, such as buffers, pH, labelling time and temperature, were investigated to optimise the synthesis of [89Zr]Zr-oxine and [89Zr]Zr-DFO-NCS in order to reach a radiochemical conversion (RCC) of >95 % without purification. Radio-instant thin-layer chromatography (iTLC) and radio high-performance liquid chromatography (radio-HPLC) were used to determine the RCC. Cells were labelled with [89Zr]Zr-oxine or [89Zr]Zr-DFO-NCS. The cellular retention of 89Zr and the labelling impact was determined by analysing the cellular functions, such as viability, proliferation, phagocytotic ability and phenotypic immunostaining.

RESULTS

The optimised synthesis of [89Zr]Zr-oxine and [89Zr]Zr-DFO-NCS resulted in straightforward protocols not requiring additional purification. [89Zr]Zr-oxine and [89Zr]Zr-DFO-NCS were synthesised with an average RCC of 98.4 % (n = 16) and 98.0 % (n = 13), respectively. Cell labelling efficiencies were 63.9 % (n = 35) and 70.2 % (n = 30), respectively. 89Zr labelling neither significantly affected the cell viability (cell viability loss was in the range of 1-8 % compared to its corresponding non-labelled cells, P value > 0.05) nor the cells' proliferation rate. The phenotype of human decidual stromal cells (hDSC) and phagocytic function of rat bone-marrow-derived macrophages (rMac) was somewhat affected by radiolabelling.

CONCLUSIONS

Our study demonstrates that [89Zr]Zr-oxine and [89Zr]Zr-DFO-NCS are equally effective in cell labelling. However, [89Zr]Zr-oxine was superior to [89Zr]Zr-DFO-NCS with regard to long-term stability, cellular retention, minimal variation between cell types and cell labelling efficiency.

In Vivo PET Imaging of Monocytes Labeled with [89Zr]Zr-PLGA-NH2 Nanoparticles in Tumor and Staphylococcus aureus Infection Models

The exponential growth of research on cell-based therapy is in major need of reliable and sensitive tracking of a small number of therapeutic cells to improve our understanding of the in vivo cell-targeting properties. ¹¹¹In-labeled poly(lactic-co-glycolic acid) with a primary amine endcap nanoparticles ([¹¹¹In]In-PLGA-NH₂ NPs) were previously used for cell labeling and in vivo tracking, using SPECT/CT imaging. However, to detect a low number of cells, a higher sensitivity of PET is preferred. Therefore, we developed ⁸⁹Zr-labeled NPs for ex vivo cell labeling and in vivo cell tracking, using PET/MRI. We intrinsically and efficiently labeled PLGA-NH₂ NPs with [⁸⁹Zr]ZrCl₄. In vitro, [⁸⁹Zr]Zr-PLGA-NH₂ NPs retained the radionuclide over a period of 2 weeks in PBS and human serum. THP-1 (human monocyte cell line) cells could be labeled with the NPs and retained the radionuclide over a period of 2 days, with no negative effect on cell viability (specific activity 279 ± 10 kBq/10⁶ cells). PET/MRI imaging could detect low numbers of [⁸⁹Zr]Zr-THP-1 cells (10,000 and 100,000 cells) injected subcutaneously in Matrigel. Last, in vivo tracking of the [⁸⁹Zr]Zr-THP-1 cells upon intravenous injection showed specific accumulation in local intramuscular Staphylococcus aureus infection and infiltration into MDA-MB-231 tumors. In conclusion, we showed that [⁸⁹Zr]Zr-PLGA-NH₂ NPs can be used for immune-cell labeling and subsequent in vivo tracking of a small number of cells in different disease models.

In Vivo Cell Tracking Using PET: Opportunities and Challenges for Clinical Translation in Oncology

Cell therapy is a rapidly evolving field involving a wide spectrum of therapeutic cells for personalised medicine in cancer. In vivo imaging and tracking of cells can provide useful information for improving the accuracy, efficacy, and safety of cell therapies. This review focuses on radiopharmaceuticals for the non-invasive detection and tracking of therapeutic cells using positron emission tomography (PET). A range of approaches for imaging therapeutic cells is discussed: Direct ex vivo labelling of cells, in vivo indirect labelling of cells by utilising gene reporters, and detection of specific antigens expressed on the target cells using antibody-based radiopharmaceuticals (immuno-PET). This review examines the evaluation of PET imaging methods for therapeutic cell tracking in preclinical cancer models, their role in the translation into patients, first-in-human studies, as well as the translational challenges involved and how they can be overcome.

Spatio-temporal biodistribution of 89Zr-oxine labeled huLym-1-A-BB3z-CAR T-cells by PET imaging in a preclinical tumor model

Quantitative in vivo monitoring of cell biodistribution offers assessment of treatment efficacy in real-time and can provide guidance for further optimization of chimeric antigen receptor (CAR) modified cell therapy. We evaluated the utility of a non-invasive, serial ⁸⁹Zr-oxine PET imaging to assess optimal dosing for huLym-1-A-BB3z-CAR T-cell directed to Lym-1-positive Raji lymphoma xenograft in NOD Scid-IL2Rgamma^null (NSG) mice. In vitro experiments showed no detrimental effects in cell health and function following ⁸⁹Zr-oxine labeling. In vivo experiments employed simultaneous PET/MRI of Raji-bearing NSG mice on day 0 (3 h), 1, 2, and 5 after intravenous administration of low (1.87 ± 0.04 × 10⁶ cells), middle (7.14 ± 0.45 × 10⁶ cells), or high (16.83 ± 0.41 × 10⁶ cells) cell dose. Biodistribution (%ID/g) in regions of interests defined over T1-weighted MRI, such as blood, bone, brain, liver, lungs, spleen, and tumor, were analyzed from PET images. Escalating doses of CAR T-cells resulted in dose-dependent %ID/g biodistributions in all regions. Middle and High dose groups showed significantly higher tumor %ID/g compared to Low dose group on day 2. Tumor-to-blood ratios showed the enhanced extravascular tumor uptake by day 2 in the Low dose group, while the Middle dose showed significant tumor accumulation starting on day 1 up to day 5. From these data obtained over time, it is apparent that intravenously administered CAR T-cells become trapped in the lung for 3–5 h and then migrate to the liver and spleen for up to 2–3 days. This surprising biodistribution data may be responsible for the inactivation of these cells before targeting solid tumors. Ex vivo biodistributions confirmed in vivo PET-derived biodistributions. According to these studies, we conclude that in vivo serial PET imaging with ⁸⁹Zr-oxine labeled CAR T-cells provides real-time monitoring of biodistributions crucial for interpreting efficacy and guiding treatment in patient care.

Mesenchymal Stem/Stromal Cell-Based Delivery: A Rapidly Evolving Strategy for Cancer Therapy

Mesenchymal stem/stromal cell (MSC)-based therapy has become an attractive and advanced scientific research area in the context of cancer therapy. This interest is closely linked to the MSC-marked tropism for tumors, suggesting them as a rational and effective vehicle for drug delivery for both hematological and solid malignancies. Nonetheless, the therapeutic application of the MSCs in human tumors is still controversial because of the induction of several signaling pathways largely contributing to tumor progression and metastasis. In spite of some evidence supporting that MSCs may sustain cancer pathogenesis, increasing proofs have indicated the suppressive influences of MSCs on tumor cells. During the last years, a myriad of preclinical and some clinical studies have been carried out or are ongoing to address the safety and efficacy of the MSC-based delivery of therapeutic agents in diverse types of malignancies. A large number of studies have focused on the MSC application as delivery vehicles for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), chemotherapeutic drug such as gemcitabine (GCB), paclitaxel (PTX), and doxorubicin (DOX), prodrugs such as 5-fluorocytosine (5-FC) and ganciclovir (GCV), and immune cell-activating cytokines along with oncolytic virus. In the current review, we evaluate the latest findings rendering the potential of MSCs to be employed as potent gene/drug delivery vehicle for inducing tumor regression with a special focus on the in vivo reports performed during the last two decades.

Nanoparticles for Stem Cell Tracking and the Potential Treatment of Cardiovascular Diseases

Stem cell-based therapies have been shown potential in regenerative medicine. In these cells, mesenchymal stem cells (MSCs) have the ability of self-renewal and being differentiated into different types of cells, such as cardiovascular cells. Moreover, MSCs have low immunogenicity and immunomodulatory properties, and can protect the myocardium, which are ideal qualities for cardiovascular repair. Transplanting mesenchymal stem cells has demonstrated improved outcomes for treating cardiovascular diseases in preclinical trials. However, there still are some challenges, such as their low rate of migration to the ischemic myocardium, low tissue retention, and low survival rate after the transplantation. To solve these problems, an ideal method should be developed to precisely and quantitatively monitor the viability of the transplanted cells in vivo for providing the guidance of clinical translation. Cell imaging is an ideal method, but requires a suitable contrast agent to label and track the cells. This article reviews the uses of nanoparticles as contrast agents for tracking MSCs and the challenges of clinical use of MSCs in the potential treatment of cardiovascular diseases.

Biodistribution of Mesenchymal Stromal Cells after Administration in Animal Models and Humans: A Systematic Review

Mesenchymal Stromal Cells (MSCs) are of great interest in cellular therapy. Different routes of administration of MSCs have been described both in pre-clinical and clinical reports. Knowledge about the fate of the administered cells is critical for developing MSC-based therapies. The aim of this review is to describe how MSCs are distributed after injection, using different administration routes in animal models and humans. A literature search was performed in order to consider how MSCs distribute after intravenous, intraarterial, intramuscular, intraarticular and intralesional injection into both animal models and humans. Studies addressing the biodistribution of MSCs in “in vivo” animal models and humans were included. After the search, 109 articles were included in the review. Intravenous administration of MSCs is widely used; it leads to an initial accumulation of cells in the lungs with later redistribution to the liver, spleen and kidneys. Intraarterial infusion bypasses the lungs, so MSCs distribute widely throughout the rest of the body. Intramuscular, intraarticular and intradermal administration lack systemic biodistribution. Injection into various specific organs is also described. Biodistribution of MSCs in animal models and humans appears to be similar and depends on the route of administration. More studies with standardized protocols of MSC administration could be useful in order to make results homogeneous and more comparable.

[18F]FDG-labelled stem cell PET imaging in different route of administrations and multiple animal species

Stem cell therapy holds great promise for tissue regeneration and cancer treatment, although its efficacy is still inconclusive and requires further understanding and optimization of the procedures. Non-invasive cell tracking can provide an important opportunity to monitor in vivo cell distribution in living subjects. Here, using a combination of positron emission tomography (PET) and in vitro 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) direct cell labelling, the feasibility of engrafted stem cell monitoring was tested in multiple animal species. Human mesenchymal stem cells (MSCs) were incubated with phosphate-buffered saline containing [18F]FDG for in vitro cell radiolabelling. The pre-labelled MSCs were administrated via peripheral vein in a mouse (n = 1), rats (n = 4), rabbits (n = 4) and non-human primates (n = 3), via carotid artery in rats (n = 4) and non-human primates (n = 3), and via intra-myocardial injection in rats (n = 5). PET imaging was started 10 min after cell administration using a dedicated small animal PET system for a mouse and rats. A clinical PET system was used for the imaging of rabbits and non-human primates. After MSC administration via peripheral vein, PET imaging revealed intense radiotracer signal from the lung in all tested animal species including mouse, rat, rabbit, and non-human primate, suggesting administrated MSCs were trapped in the lung tissue. Furthermore, the distribution of the PET signal significantly differed based on the route of cell administration. Administration via carotid artery showed the highest activity in the head, and intra-myocardial injection increased signal from the heart. In vitro [18F]FDG MSC pre-labelling for PET imaging is feasible and allows non-invasive visualization of initial cell distribution after different routes of cell administration in multiple animal models. Those results highlight the potential use of that imaging approach for the understanding and optimization of stem cell therapy in translational research.

Mesenchymal stem/stromal cell-based therapy: mechanism, systemic safety and biodistribution for precision clinical applications

Mesenchymal stem/stromal cells (MSCs) are a promising resource for cell-based therapy because of their high immunomodulation ability, tropism towards inflamed and injured tissues, and their easy access and isolation. Currently, there are more than 1200 registered MSC clinical trials globally. However, a lack of standardized methods to characterize cell safety, efficacy, and biodistribution dramatically hinders the progress of MSC utility in clinical practice. In this review, we summarize the current state of MSC-based cell therapy, focusing on the systemic safety and biodistribution of MSCs. MSC-associated risks of tumor initiation and promotion and the underlying mechanisms of these risks are discussed. In addition, MSC biodistribution methodology and the pharmacokinetics and pharmacodynamics of cell therapies are addressed. Better understanding of the systemic safety and biodistribution of MSCs will facilitate future clinical applications of precision medicine using stem cells.

A kit formulation for the preparation of [89Zr]Zr(oxinate)4 for PET cell tracking: White blood cell labelling and comparison with [111In]In(oxinate)3

BACKGROUND

Advances in immunology and cell-based therapies are creating a need to track individual cell types, such as immune cells (neutrophils, eosinophils, chimeric antigen receptor (CAR) T cells, etc.) and stem cells. As the fate of administered cells remains largely unknown, nuclear imaging could determine the migration and survival of cells in patients. [89Zr]Zr(oxinate)4, or [89Zr]Zr-oxine, is a radiotracer for positron emission tomography (PET) that has been evaluated in preclinical models of cell tracking and could improve on [111In]In-oxine, the current gold standard radiotracer for cell tracking by scintigraphy and single-photon emission computed tomography (SPECT), because of the better sensitivity, spatial resolution and quantification of PET. However, a clinically usable formulation of [89Zr]Zr-oxine is lacking. This study demonstrates a 1-step procedure for preparing [89Zr]Zr-oxine and evaluates it against [111In]In-oxine in white blood cell (WBC) labelling.

METHODS

Commercial [89Zr]Zr-oxalate was added to a formulation containing oxine, a buffering agent, a base and a surfactant or organic solvent. WBC isolated from 10 human volunteers were radiolabelled with [89Zr]Zr-oxine following a clinical radiolabelling protocol. Labelling efficiency, cell viability, chemotaxis and DNA damage were evaluated in vitro, in an intra-individual comparison against [111In]In-oxine.

RESULTS

An optimised formulation of [89Zr]Zr-oxine containing oxine, polysorbate 80 and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) was developed. This enabled 1-step radiolabelling of oxine with commercial [89Zr]Zr-oxalate (0.1-25 MBq) in 5 min and radiotracer stability for 1 week. WBC labelling efficiency was 48.7 ± 6.3%, compared to 89.1 ± 9.5% (P < 0.0001, n = 10) for [111In]In-oxine. Intracellular retention of 89Zr and cell viability after radiolabelling were comparable to 111In. There were no significant differences in leukocyte chemotaxis or DNA damage between [89Zr]Zr-oxine or [111In]In-oxine. CONCLUSIONS, ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE: Our results demonstrate that [89Zr]Zr-oxine is a suitable PET alternative to [111In]In-oxine for WBC imaging. Our formulation allows rapid, stable, high-yield, single-step preparation of [89Zr]Zr-oxine from commercially available 89Zr. This will facilitate the clinical translation of cell tracking using [89Zr]Zr-oxine.