Stem cell-mediated delivery of SPIO-loaded gold nanoparticles for the theranosis of liver injury and hepatocellular carcinoma

Potential Consequences of the Use of Adipose-Derived Stem Cells in the Treatment of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) ranks as the most prevalent of primary liver cancers and stands as the third leading cause of cancer-related deaths. Early-stage HCC can be effectively managed with available treatment modalities ranging from invasive techniques, such as liver resection and thermoablation, to systemic therapies primarily employing tyrosine kinase inhibitors. Unfortunately, these interventions take a significant toll on the body, either through physical trauma or the adverse effects of pharmacotherapy. Consequently, there is an understandable drive to develop novel HCC therapies. Adipose-derived stem cells (ADSCs) are a promising therapeutic tool. Their facile extraction process, coupled with the distinctive immunomodulatory capabilities of their secretome, make them an intriguing subject for investigation in both oncology and regenerative medicine. The factors they produce are both enzymes affecting the extracellular matrix (specifically, metalloproteinases and their inhibitors) as well as cytokines and growth factors affecting cell proliferation and invasiveness. So far, the interactions observed with various cancer cell types have not led to clear conclusions. The evidence shows both inhibitory and stimulatory effects on tumor growth. Notably, these effects appear to be dependent on the tumor type, prompting speculation regarding their potential inhibitory impact on HCC. This review briefly synthesizes findings from preclinical and clinical studies examining the effects of ADSCs on cancers, with a specific focus on HCC, and emphasizes the need for further research.

Stem cell therapy for hepatocellular carcinoma and end-stage liver disease

Hepatocellular carcinoma (HCC) is a major health problem worldwide, especially for patients who are suffering from end-stage liver disease (ESLD). The ESLD is considered a great challenge for clinicians due to the limited chance for liver transplantation, which is the only curative treatment for those patients. Stem cell-based therapy as a part of regenerative medicine represents a promising application for ESLD patients. Many clinical trials were performed to assess the utility of bone marrow-derived stem cells as a potential therapy for patients with liver diseases. The aim of the present study is to present and review the various types of stem cell-based therapy, including the mesenchymal stem cells (MSCs), BM-derived mononuclear cells (BM-MNCs), CD34 + hematopoietic stem cells (HSCs), induced pluripotent stem cells (iPSCs), and cancer stem cells.Though this type of therapy achieved promising results for the treatment of ESLD, however still there is a confounding data regarding its clinical application. A large body of evidence is highly required to evaluate the stem cell-based therapy after long-term follow-up, with respect to the incidence of toxicity, immunogenicity, and tumorigenesis that developed in many patients.

Advances of Nanotechnology in the Diagnosis and Treatment of Hepatocellular Carcinoma

Nanotechnology has emerged as a promising technology in the field of hepatocellular carcinoma (HCC), specifically in the implementation of diagnosis and treatment strategies. Nanotechnology-based approaches, such as nanoparticle-based contrast agents and nanoscale imaging techniques, have shown great potential for enhancing the sensitivity and specificity of HCC detection. These approaches provide high-resolution imaging and allow for the detection of molecular markers and alterations in cellular morphology associated with HCC. In terms of treatment, nanotechnology has revolutionized HCC therapy by enabling targeted drug delivery, enhancing therapeutic efficacy, and minimizing off-target effects. Nanoparticle-based drug carriers can be functionalized with ligands specific to HCC cells, allowing for selective accumulation of therapeutic agents at the tumor site. Furthermore, nanotechnology can facilitate combination therapy by co-encapsulating multiple drugs within a single nanoparticle, allowing for synergistic effects and overcoming drug resistance. This review aims to provide an overview of recent advances in nanotechnology-based approaches for the diagnosis and treatment of HCC. Further research is needed to optimize the design and functionality of nanoparticles, improve their biocompatibility and stability, and evaluate their long-term safety and efficacy. Nonetheless, the integration of nanotechnology in HCC management holds great promise and may lead to improved patient outcomes in the future.

Nanomedicine in cancer therapy

Cancer remains a highly lethal disease in the world. Currently, either conventional cancer therapies or modern immunotherapies are non-tumor-targeted therapeutic approaches that cannot accurately distinguish malignant cells from healthy ones, giving rise to multiple undesired side effects. Recent advances in nanotechnology, accompanied by our growing understanding of cancer biology and nano-bio interactions, have led to the development of a series of nanocarriers, which aim to improve the therapeutic efficacy while reducing off-target toxicity of the encapsulated anticancer agents through tumor tissue-, cell-, or organelle-specific targeting. However, the vast majority of nanocarriers do not possess hierarchical targeting capability, and their therapeutic indices are often compromised by either poor tumor accumulation, inefficient cellular internalization, or inaccurate subcellular localization. This Review outlines current and prospective strategies in the design of tumor tissue-, cell-, and organelle-targeted cancer nanomedicines, and highlights the latest progress in hierarchical targeting technologies that can dynamically integrate these three different stages of static tumor targeting to maximize therapeutic outcomes. Finally, we briefly discuss the current challenges and future opportunities for the clinical translation of cancer nanomedicines.

Magnetic Nanostructures and Stem Cells for Regenerative Medicine, Application in Liver Diseases

The term "liver disease" refers to any hepatic condition that leads to tissue damage or altered hepatic function and can be induced by virus infections, autoimmunity, inherited genetic mutations, high consumption of alcohol or drugs, fat accumulation, and cancer. Some types of liver diseases are becoming more frequent worldwide. This can be related to increasing rates of obesity in developed countries, diet changes, higher alcohol intake, and even the coronavirus disease 2019 (COVID-19) pandemic was associated with increased liver disease-related deaths. Although the liver can regenerate, in cases of chronic damage or extensive fibrosis, the recovery of tissue mass is impossible, and a liver transplant is indicated. Because of reduced organ availability, it is necessary to search for alternative bioengineered solutions aiming for a cure or increased life expectancy while a transplant is not possible. Therefore, several groups were studying the possibility of stem cells transplantation as a therapeutic alternative since it is a promising strategy in regenerative medicine for treating various diseases. At the same time, nanotechnological advances can contribute to specifically targeting transplanted cells to injured sites using magnetic nanoparticles. In this review, we summarize multiple magnetic nanostructure-based strategies that are promising for treating liver diseases.

Advances in the Study of Bioactive Nanoparticles for the Treatment of HCC and Its Postoperative Residual Cancer

Primary hepatocellular carcinoma (HCC, hepatocellular carcinoma) is the third leading cause of tumor death in the world and the second leading cause in China. The high recurrence rate at 5 years after surgery also seriously affects the long-term survival of HCC patients. For reasons such as poor liver function, large tumors, or vascular invasion, only relatively limited palliative treatment is available. Therefore, effective diagnostic and therapeutic strategies are needed to improve the complex microenvironment and block the mechanism of tumor development in order to treat the tumor and prevent recurrence. A variety of bioactive nanoparticles have been shown to have therapeutic effects on hepatocellular carcinoma and have the advantages of improving drug solubility, reducing drug side effects, preventing degradation in the blood, increasing drug exposure time, and reducing drug resistance. The development of bioactive nanoparticles is expected to complete the current clinical therapeutic approach. In this review, we discuss the therapeutic advances of different nanoparticles for hepatocellular carcinoma and discuss their potential for postoperative applications with respect to possible mechanisms of hepatocellular carcinoma recurrence. We further discuss the limitations regarding the application of NPs and the safety of NPs.

Long-term and non-invasive in vivo tracking of DiD dye-labeled human hepatic progenitors in chronic liver disease models

BACKGROUND

Chronic liver diseases (CLD) are the major public health burden due to the continuous increasing rate of global morbidity and mortality. The inherent limitations of organ transplantation have led to the development of stem cell-based therapy as a supportive and promising therapeutic option. However, identifying the fate of transplanted cells in vivo represents a crucial obstacle.

AIM

To evaluate the potential applicability of DiD dye as a cell labeling agent for long-term, and non-invasive in vivo tracking of transplanted cells in the liver.

METHODS

Magnetically sorted, epithelial cell adhesion molecule positive (1 × 10⁶ cells/mL) fetal hepatic progenitor cells were labeled with DiD dye and transplanted into the livers of CLD-severe combined immunodeficiency (SCID) mice. Near-infrared (NIR) imaging was performed for in vivo tracking of the DiD-labeled transplanted cells along with colocalization of hepatic markers for up to 80 d. The existence of human cells within mouse livers was identified using Alu polymerase chain reaction and sequencing.

RESULTS

NIR fluorescence imaging of CLD-SCID mice showed a positive fluorescence signal of DiD at days 7, 15, 30, 45, 60, and 80 post-transplantation. Furthermore, positive staining of cytokeratin, c-Met, and albumin colocalizing with DiD fluorescence clearly demonstrated that the fluorescent signal of hepatic markers emerged from the DiD-labeled transplanted cells. Recovery of liver function was also observed with serum levels of glutamic-oxaloacetic transaminase, glutamate-pyruvate transaminase, and bilirubin. The detection of human-specific Alu sequence from the transplanted mouse livers provided evidence for the survival of transplanted cells at day 80.

CONCLUSION

DiD-labeling is promising for long-term and non-invasive in vivo cell tracking, and understanding the regenerative mechanisms incurred by the transplanted cells.

Nanotechnology-Assisted Cell Tracking

The usefulness of nanoparticles (NPs) in the diagnostic and/or therapeutic sector is derived from their aptitude for navigating intra- and extracellular barriers successfully and to be spatiotemporally targeted. In this context, the optimization of NP delivery platforms is technologically related to the exploitation of the mechanisms involved in the NP-cell interaction. This review provides a detailed overview of the available technologies focusing on cell-NP interaction/detection by describing their applications in the fields of cancer and regenerative medicine. Specifically, a literature survey has been performed to analyze the key nanocarrier-impacting elements, such as NP typology and functionalization, the ability to tune cell interaction mechanisms under in vitro and in vivo conditions by framing, and at the same time, the imaging devices supporting NP delivery assessment, and consideration of their specificity and sensitivity. Although the large amount of literature information on the designs and applications of cell membrane-coated NPs has reached the extent at which it could be considered a mature branch of nanomedicine ready to be translated to the clinic, the technology applied to the biomimetic functionalization strategy of the design of NPs for directing cell labelling and intracellular retention appears less advanced. These approaches, if properly scaled up, will present diverse biomedical applications and make a positive impact on human health.

Targeted mesenchymal stem cell therapy equipped with a cell-tissue nanomatchmaker attenuates osteoarthritis progression

Mesenchymal stem cells (MSCs) are at the forefront of research for a wide range of diseases, including osteoarthritis (OA). Despite having attracted the attention of orthopedists, current MSC therapy techniques are limited by poor MSC implantation in tissue defects and lack of lateral tissue integration, which has restricted the efficacy of cell therapy to alleviate OA symptoms only. Here, we developed targeted MSC therapy for OA cartilage using a cell-tissue matchmaking nanoconstruct (C-TMN). C-TMN, as an MSC vehicle, consists of a central iron oxide nanoparticle armed with two types of antibodies, one directed at the MSC surface and the other against articular cartilage. We treated rat OA articular cartilage with intra-articular injections of C-TMN with and without exogenous MSCs. We observed substantial improvements in both symptomatic and radiographic OA caused by C-TMN, which was independent of exogenous MSCs. This new approach could predict a promising future for OA management.

Iron Oxide-Based Magneto-Optical Nanocomposites for In Vivo Biomedical Applications

Iron oxide nanoparticles (IONPs) have played a pivotal role in the development of nanomedicine owing to their versatile functions at the nanoscale, which facilitates targeted delivery, high contrast imaging, and on-demand therapy. Some biomedical inadequacies of IONPs on their own, such as the poor resolution of IONP-based Magnetic Resonance Imaging (MRI), can be overcome by co-incorporating optical probes onto them, which can be either molecule- or nanoparticulate-based. Optical probe incorporated IONPs, together with two prominent non-ionizing radiation sources (i.e., magnetic field and light), enable a myriad of biomedical applications from early detection to targeted treatment of various diseases. In this context, many research articles are in the public domain on magneto-optical nanoparticles; discussed in detail are fabrication strategies for their application in the biomedical field; however, lacking is a comprehensive review on real-life applications in vivo, their toxicity, and the prospect of bench-to-bedside clinical studies. Therefore, in this review, we focused on selecting such important nanocomposites where IONPs become the magnetic component, conjugated with various types of optical probes; we clearly classified them into class 1 to class 6 categories and present only in vivo studies. In addition, we briefly discuss the potential toxicity of such nanocomposites and their respective challenges for clinical translations.

The Use of Alternative Strategies for Enhanced Nanoparticle Delivery to Solid Tumors

Nanomaterial (NM) delivery to solid tumors has been the focus of intense research for over a decade. Classically, scientists have tried to improve NM delivery by employing passive or active targeting strategies, making use of the so-called enhanced permeability and retention (EPR) effect. This phenomenon is made possible due to the leaky tumor vasculature through which NMs can leave the bloodstream, traverse through the gaps in the endothelial lining of the vessels, and enter the tumor. Recent studies have shown that despite many efforts to employ the EPR effect, this process remains very poor. Furthermore, the role of the EPR effect has been called into question, where it has been suggested that NMs enter the tumor via active mechanisms and not through the endothelial gaps. In this review, we provide a short overview of the EPR and mechanisms to enhance it, after which we focus on alternative delivery strategies that do not solely rely on EPR in itself but can offer interesting pharmacological, physical, and biological solutions for enhanced delivery. We discuss the strengths and shortcomings of these different strategies and suggest combinatorial approaches as the ideal path forward.

Delivery systems for enhancing oncolytic adenoviruses efficacy

Oncolytic adenovirus (OAds) has long been considered a promising biotherapeutic agent against various types of cancer owing to selectively replicate in and lyse cancer cells, while remaining dormant in healthy cells. In the last years, multiple (pre)clinical studies using genetic engineering technologies enhanced OAds anti-tumor effects in a broad range of cancers. However, poor targeting delivery, tropism toward healthy tissues, low-level expression of Ad receptors on tumor cells, and pre-existing neutralizing antibodies are major hurdles for systemic administration of OAds. Different vehicles have been developed for addressing these obstacles, such as stem cells, nanoparticles (NPs) and shielding polymers, extracellular vesicles (EVs), hydrogels, and microparticles (MPs). These carriers can enhance the therapeutic efficacy of OVs through enhancing transfection, circulatory longevity, cellular interactions, specific targeting, and immune responses against cancer. In this paper, we reviewed adenovirus structure and biology, different types of OAds, and the efficacy of different carriers in systemic administration of OAds.

A bionic shuttle carrying multi-modular particles and holding tumor-tropic features

The systemic delivery of composite nanoparticles remains an outstanding challenge in cancer nanomedicine, and the principal reason is a complex interplay of biological barriers. In this regard, adaptive cell transfer may represent an alternative solution to circumvent these barriers down to the tumor microenvironment. Here, tumor-tropic macrophages are proposed as a tool to draw and vehiculate modular nanoparticles integrating magnetic and plasmonic components. The end result is a bionic shuttle that exhibits a plasmonic band within the so-called therapeutic window arising from as much as 40 pg Au per cell, magnetization in the order of 150 pemu per cell, and more than 90% of the pristine viability and chemotactic activity of its biological component, until at least two days of preparation. Its synergistic combination of plasmonic, magnetic and tumor-tropic functions is assessed in vitro for applications as magnetic guidance or sorting, with a propulsion around 4 μm s^-1 for a magnetic gradient of 0.8 T m^-1, the optical hyperthermia of cancer, with stability of photothermal conversion to temperatures exceeding 50^∘C, and the photoacoustic imaging of cancer under realistic conditions. These results collectively suggest that a bionic design may be a promising roadmap to reconcile the efforts for multifunctionality and targeted delivery, which are both key goals in nanomedicine.

Stem Cell Therapy for Hepatocellular Carcinoma: Future Perspectives

Hepatocellular carcinoma (HCC) is one of the most common types of cancer and results in a high mortality rate worldwide. Unfortunately, most cases of HCC are diagnosed in an advanced stage, resulting in a poor prognosis and ineffective treatment. HCC is often resistant to both radiotherapy and chemotherapy, resulting in a high recurrence rate. Although the use of stem cells is evolving into a potentially effective approach for the treatment of cancer, few studies on stem cell therapy in HCC have been published. The administration of stem cells from bone marrow, adipose tissue, the amnion, and the umbilical cord to experimental animal models of HCC has not yielded consistent responses. However, it is possible to induce the apoptosis of cancer cells, repress angiogenesis, and cause tumor regression by administration of genetically modified stem cells. New alternative approaches to cancer therapy, such as the use of stem cell derivatives, exosomes or stem cell extracts, have been proposed. In this review, we highlight these experimental approaches for the use of stem cells as a vehicle for local drug delivery.

Stem cell-derived extracellular vesicles: role in oncogenic processes, bioengineering potential, and technical challenges

Extracellular vesicles (EVs) are cellular-derived versatile transporters with a specialized property for trafficking a variety of cargo, including metabolites, growth factors, cytokines, proteins, lipids, and nucleic acids, throughout the microenvironment. EVs can act in a paracrine manner to facilitate communication between cells as well as modulate immune, inflammatory, regenerative, and remodeling processes. Of particular interest is the emerging association between EVs and stem cells, given their ability to integrate complex inputs for facilitating cellular migration to the sites of tissue injury. Additionally, stem cell-derived EVs can also act in an autocrine manner to influence stem cell proliferation, mobilization, differentiation, and self-renewal. Hence, it has been postulated that stem cells and EVs may work synergistically in the process of tissue repair and that dysregulation of EVs may cause a loss of homeostasis in the microenvironment leading to disease. By harnessing the property of EVs for delivery of small molecules, stem cell-derived EVs possess significant potential as a platform for developing bioengineering approaches for next-generation cancer therapies and targeted drug delivery methods. Although one of the main challenges of clinical cancer treatment remains a lack of specificity for the delivery of effective treatment options, EVs can be modified via genetic, biochemical, or synthetic methods for enhanced targeting ability of chemotherapeutic agents in promoting tumor regression. Here, we summarize recent research on the bioengineering potential of EV-based cancer therapies. A comprehensive understanding of EV modification may provide a novel strategy for cancer therapy and for the utilization of EVs in the targeting of oncogenic processes. Furthermore, innovative and emerging new technologies are shifting the paradigm and playing pivotal roles by continually expanding novel methods and materials for synthetic processes involved in the bioengineering of EVs for enhanced precision therapeutics.

Cells and cell derivatives as drug carriers for targeted delivery

For over a century, researchers have focused on how to optimize drug delivery. Systemic administration means that the drug becomes dilute and has the potential to diffuse to all tissues, which is only until the immune system steps in and rapidly clears it from blood circulation. Drug carriers are the solution for amplifying the intended effect and diminishing side effects. With drug carriers, tissue-specific drug delivery and controlled drug release is possible. Thus far, both synthetic and non-synthetic carriers exist. However, due to the numerous limitations of synthetic carriers, science has begun to concentrate on using live cells and cell-derivatives as drug carriers. The most problematic shortcomings of synthetic carriers are their limited biocompatibility and biodegradability. Most synthetic carriers are cytotoxic or induce immune responses. Moreover, synthetic carriers typically depend on passive diffusion and risk phagocytosis, further reducing their impact. On the other hand, live-cell carriers and their derivatives usually have a targeting mechanism and drug release is controlled, increasing the efficiency with which a drug accumulates and acts on a tissue. Still, both types of carriers face similar problems, including achieving high loading capacity, maintaining drug quality, efficiently accumulating in the target tissue, and minimizing side effects. This review aims to elucidate the advantages and disadvantages of each popular cell or cell-derived carrier and to spotlight novel solutions.

Recent Findings on Nanotechnology-based Therapeutic Strategies Against Hepatocellular Carcinoma

Background:

Nanotechnology-based therapies are emerging as a promising new anticancer approach. Early clinical studies suggest that nanoparticle-based therapeutics can show enhanced efficacy while reducing side effects minimal, owing to targeted delivery and active intracellular uptake.

Methods:

To overcome the problems of gene and drug delivery, nanotechnology based delivery system gained interest in the last two decades. Encouraging results from Nano formulation based drug delivery systems revealed that these emerging restoratives can efficiently lead to more effective, targeted, selective and efficacious delivery of chemotherapeutic agents to the affected target cells.

Results:

Nanotechnology not only inhibits targeted gene products in patients with cancer, but also taught us valuable lessons regarding appropriate dosages and route of administrations. Besides, nanotechnology based therapeutics holds remarkable potential as an effective drug delivery system. We critically highlight the recent findings on nanotechnology mediated therapeutics strategies to combat hepatocellular carcinoma and discuss how nanotechnology platform can have enhanced anticancer effects compared with the parent therapeutic agents they contain.

Conclusion:

In this review, we discussed the key challenges, recent findings and future perspective in the development of effective nanotechnology-based cancer therapeutics. The emphasis here is focused on nanotechnology-based therapies that are likely to affect clinical investigations and their implications for advancing the treatment of patients with hepatocellular carcinoma.

Efficacy Evaluation and Tracking of Bone Marrow Stromal Stem Cells in a Rat Model of Renal Ischemia-Reperfusion Injury

Objectives

The aim of this study was to evaluate the effects of bone marrow stromal stem cells (BMSCs) on renal ischemia-reperfusion injury (RIRI) and dynamically monitor engrafted BMSCs in vivo for the early prediction of their therapeutic effects in a rat model.

Methods

A rat model of RIRI was prepared by clamping the left renal artery for 45 min. One week after renal artery clamping, 2 × 10⁶ superparamagnetic iron oxide- (SPIO-) labeled BMSCs were injected into the renal artery. Next, MR imaging of the kidneys was performed on days 1, 7, 14, and 21 after cell transplantation. On day 21, after transplantation, serum creatinine (Scr) and urea nitrogen (BUN) levels were assessed, and HE staining and TUNEL assay were also performed.

Results

The body weight growth rates in the SPIO-BMSC group were significantly higher than those in the PBS group (P < 0.05), and the Scr and BUN levels were also significantly lower than those in the PBS group (P < 0.05). HE staining showed that the degree of degeneration and vacuole-like changes in the renal tubular epithelial cells in the SPIO-BMSC group was significantly better than that observed in the PBS group. The TUNEL assay showed that the number of apoptotic renal tubular epithelial cells in the SPIO-BMSC group was significantly lower than that in the PBS group. The T2 value of the renal lesion was the highest on day 1 after cell transplantation, and it gradually decreased with time in both the PBS and SPIO-BMSC groups but was always the lowest in the SPIO-BMSC group.

Conclusion

SPIO-labeled BMSC transplantation can significantly promote the recovery of RIRI and noninvasive dynamic monitoring of engrafted cells and can also be performed simultaneously with MRI in vivo for the early prediction of therapeutic effects.

Regenerative and Transplantation Medicine: Cellular Therapy Using Adipose Tissue-Derived Mesenchymal Stromal Cells for Type 1 Diabetes Mellitus

Type 1 diabetes mellitus (T1DM) is caused by the autoimmune targeting of pancreatic β-cells, and, in the advanced stage, severe hypoinsulinemia due to islet destruction. In patients with T1DM, continuous exogenous insulin therapy cannot be avoided. However, an insufficient dose of insulin easily induces extreme hyperglycemia or diabetic ketoacidosis, and intensive insulin therapy may cause hypoglycemic symptoms including hypoglycemic shock. While these insulin therapies are efficacious in most patients, some additional therapies are warranted to support the control of blood glucose levels and reduce the risk of hypoglycemia in patients who respond poorly despite receiving appropriate treatment. There has been a recent gain in the popularity of cellular therapies using mesenchymal stromal cells (MSCs) in various clinical fields, owing to their multipotentiality, capacity for self-renewal, and regenerative and immunomodulatory potential. In particular, adipose tissue-derived MSCs (ADMSCs) have become a focus in the clinical setting due to the abundance and easy isolation of these cells. In this review, we outline the possible therapeutic benefits of ADMSC for the treatment of T1DM.

Coatings on mammalian cells: interfacing cells with their environment

The research community is intent on harnessing increasingly complex biological building blocks. At present, cells represent a highly functional component for integration into higher order systems. In this review, we discuss the current application space for cellular coating technologies and emphasize the relationship between the target application and coating design. We also discuss how the cell and the coating interact in common analytical techniques, and where caution must be exercised in the interpretation of results. Finally, we look ahead at emerging application areas that are ideal for innovation in cellular coatings. In all, cellular coatings leverage the machinery unique to specific cell types, and the opportunities derived from these hybrid assemblies have yet to be fully realized.

Bioengineered cellular and cell membrane-derived vehicles for actively targeted drug delivery: So near and yet so far

Cellular carriers for drug delivery are attractive alternatives to synthetic nanoparticles owing to their innate homing/targeting abilities. Here, we review molecular interactions involved in the homing of Mesenchymal stem cells (MSCs) and other cell types to understand the process of designing and engineering highly efficient, actively targeting cellular vehicles. In addition, we comprehensively discuss various genetic and non-genetic strategies and propose futuristic approaches of engineering MSC homing using micro/nanotechnology and high throughput small molecule screening. Most of the targeting abilities of a cell come from its plasma membrane, thus, efforts to harness cell membranes as drug delivery vehicles are gaining importance and are highlighted here. We also recognize and report the lack of detailed characterization of cell membranes in terms of safety, structural integrity, targeting functionality, and drug transport. Finally, we provide insights on future development of bioengineered cellular and cell membrane-derived vesicles for successful clinical translation.

Magnetic resonance and photoacoustic imaging of brain tumor mediated by mesenchymal stem cell labeled with multifunctional nanoparticle introduced via carotid artery injection

OBJECTIVE

To evaluate the feasibility of visualizing bone marrow-derived human mesenchymal stem cells (MSCs) labeled with a gold-coated magnetic resonance (MR)-active multifunctional nanoparticle and injected via the carotid artery for assessing the extent of MSC homing in glioma-bearing mice.

MATERIALS AND METHODS

Nanoparticles containing superparamagnetic iron oxide coated with gold (SPIO@Au) with a diameter of ∼82 nm and maximum absorbance in the near infrared region were synthesized. Bone marrow-derived MSCs conjugated with green fluorescent protein (GFP) were successfully labeled with SPIO@Au at 4 μg ml^-1 and injected via the internal carotid artery in six mice bearing orthotopic U87 tumors. Unlabeled MSCs were used as a control. The ability of SPIO@Au-loaded MSCs to be imaged using MR and photoacoustic (PA) imaging at t = 0 h, 2 h, 24 h, and 72 h was assessed using a 7 T Bruker Biospec experimental MR scanner and a Vevo LAZR PA imaging system with a 5 ns laser as the excitation source. Histological analysis of the brain tissue was performed 72 h after MSC injection using GFP fluorescence, Prussian blue staining, and hematoxylin-and-eosin staining.

RESULTS

MSCs labeled with SPIO@Au at 4 μg ml^-1 did not exhibit cell death or any adverse effects on differentiation or migration. The PA signal in tumors injected with SPIO@Au-loaded MSCs was clearly more enhanced post-injection, as compared with the tumors injected with unlabeled MSCs at t = 72 h. Using the same mice, T2-weighted MR imaging results taken before injection and at t = 2 h, 24 h, and 72 h were consistent with the PA imaging results, showing significant hypointensity of the tumor in the presence of SPIO@Au-loaded MSCs. Histological analysis also showed co-localization of GFP fluorescence and iron, thereby confirming that SPIO@Au-labeled MSCs continue to carry their nanoparticle payloads even at 72 h after injection.

CONCLUSIONS

Our results demonstrated the feasibility of tracking carotid artery-injected SPIO@Au-labeled MSCs in vivo via MR and PA imaging.

Molecular Imaging of Stem Cell Transplantation for Liver Diseases: Monitoring, Clinical Translation, and Theranostics

Stem cell transplantation has been investigated to rescue experimental liver failure and is promising to offer an alternative therapy to liver transplantation for liver diseases treatment. Several clinical studies in this field have been carried out, but the therapeutic benefit of this treatment is still controversial. A major obstacle to developing stem cell therapies in clinic is being able to visualize the cells in vivo. Imaging modalities allow optimization of delivery, detecting cell survival and functionality by in vivo monitoring these transplanted graft cells. Moreover, theranostic imaging is a brand new field that utilizes nanometer-scale materials to glean diagnostic insight for simultaneous treatment, which is very promising to improve stem cell-based therapy for treatment of liver diseases. The aim of this review was to summarize the various imaging tools that have been explored with advanced molecular imaging probes. We also outline some recent progress of preclinical and clinical studies of liver stem cells transplantation. Finally, we discuss theranostic imaging for stem cells transplantation for liver dysfunction and future opportunities afforded by theranostic imaging.

Noninvasive in-vivo tracing and imaging of transplanted stem cells for liver regeneration

Terminal liver disease is a major cause of death globally. The only ultimate therapeutic approach is orthotopic liver transplant. Because of the innate defects of organ transplantation, stem cell-based therapy has emerged as an effective alternative, based on the capacity of stem cells for multilineage differentiation and their homing to injured sites. However, the disease etiology, cell type, timing of cellular graft, therapeutic dose, delivery route, and choice of endpoints have varied between studies, leading to different, even divergent, results. In-vivo cell imaging could therefore help us better understand the fate and behaviors of stem cells to optimize cell-based therapy for liver regeneration. The primary imaging techniques in preclinical or clinical studies have consisted of optical imaging, magnetic resonance imaging, radionuclide imaging, reporter gene imaging, and Y chromosome-based fluorescence in-situ hybridization imaging. More attention has been focused on developing new or modified imaging methods for longitudinal and high-efficiency tracing. Herein, we provide a descriptive overview of imaging modalities and discuss recent advances in the field of molecular imaging of intrahepatic stem cell grafts.

Stimuli-Responsive Gold Nanoparticles for Cancer Diagnosis and Therapy

An emerging concept is that cancers strongly depend on both internal and external signals for growth and invasion. In this review, we will discuss pathological and physical changes in the tumor microenvironment and how these changes can be exploited to design gold nanoparticles for cancer diagnosis and therapy. These intrinsic changes include extracellular and intracellular pH, extracellular matrix enzymes, and glutathione concentration. External stimuli include the application of laser, ultrasound and X-ray. The biology behind these changes and the chemistry behind the responding mechanisms to these changes are reviewed. Examples of recent in vitro and in vivo studies are also presented, and the clinical implications of these findings are discussed.

Stimuli-Responsive Gold Nanoparticles for Cancer Diagnosis and Therapy

An emerging concept is that cancers strongly depend on both internal and external signals for growth and invasion. In this review, we will discuss pathological and physical changes in the tumor microenvironment and how these changes can be exploited to design gold nanoparticles for cancer diagnosis and therapy. These intrinsic changes include extracellular and intracellular pH, extracellular matrix enzymes, and glutathione concentration. External stimuli include the application of laser, ultrasound and X-ray. The biology behind these changes and the chemistry behind the responding mechanisms to these changes are reviewed. Examples of recent in vitro and in vivo studies are also presented, and the clinical implications of these findings are discussed.

Extrinsic and Intrinsic Mechanisms by Which Mesenchymal Stem Cells Suppress the Immune System

Mesenchymal stem cells (MSCs) are a group of fibroblast-like multipotent mesenchymal stromal cells that have the ability to differentiate into osteoblasts, adipocytes, and chondrocytes. Recent studies have demonstrated that MSCs possess a unique ability to exert suppressive and regulatory effects on both adaptive and innate immunity in an autologous and allogeneic manner. A vital step in stem cell transplantation is overcoming the potential graft-versus-host disease, which is a limiting factor to transplantation success. Given that MSCs attain powerful differentiation capabilities and also present immunosuppressive properties, which enable them to survive host immune rejection, MSCs are of great interest. Due to their ability to differentiate into different cell types and to suppress and modulate the immune system, MSCs are being developed for treating a plethora of diseases, including immune disorders. Moreover, in recent years, MSCs have been genetically engineered to treat and sometimes even cure some diseases, and the use of MSCs for cell therapy presents new perspectives for overcoming tissue rejection. In this review, we discuss the potential extrinsic and intrinsic mechanisms that underlie MSCs' unique ability to modulate inflammation, and both innate and adaptive immunity.

Controlled Payload Release by Magnetic Field Triggered Neural Stem Cell Destruction for Malignant Glioma Treatment

Stem cells have recently garnered attention as drug and particle carriers to sites of tumors, due to their natural ability to track to the site of interest. Specifically, neural stem cells (NSCs) have demonstrated to be a promising candidate for delivering therapeutics to malignant glioma, a primary brain tumor that is not curable by current treatments, and inevitably fatal. In this article, we demonstrate that NSCs are able to internalize 2 μm magnetic discs (SD), without affecting the health of the cells. The SD can then be remotely triggered in an applied 1 T rotating magnetic field to deliver a payload. Furthermore, we use this NSC-SD delivery system to deliver the SD themselves as a therapeutic agent to mechanically destroy glioma cells. NSCs were incubated with the SD overnight before treatment with a 1T rotating magnetic field to trigger the SD release. The potential timed release effects of the magnetic particles were tested with migration assays, confocal microscopy and immunohistochemistry for apoptosis. After the magnetic field triggered SD release, glioma cells were added and allowed to internalize the particles. Once internalized, another dose of the magnetic field treatment was administered to trigger mechanically induced apoptotic cell death of the glioma cells by the rotating SD. We are able to determine that NSC-SD and magnetic field treatment can achieve over 50% glioma cell death when loaded at 50 SD/cell, making this a promising therapeutic for the treatment of glioma.

Development of individualized anti-metastasis strategies by engineering nanomedicines

Metastasis is deadly and also tough to treat as it is much more complicated than the primary tumour. Anti-metastasis approaches available so far are far from being optimal. A variety of nanomedicine formulae provide a plethora of opportunities for developing new strategies and means for tackling metastasis. It should be noted that individualized anti-metastatic nanomedicines are different from common anti-cancer nanomedicines as they specifically target different populations of malignant cells. This review briefly introduces the features of the metastatic cascade, and proposes a series of nanomedicine-based anti-metastasis strategies aiming to block each metastatic step. Moreover, we also concisely introduce the advantages of several promising nanoparticle platforms and their potential for constructing state-of-the-art individualized anti-metastatic nanomedicines.

Design strategies and applications of circulating cell-mediated drug delivery systems

Drug delivery systems, particularly nanomaterial-based drug delivery systems, possess a tremendous amount of potential to improve diagnostic and therapeutic effects of drugs. Controlled drug delivery targeted to a specific disease is designed to significantly improve the pharmaceutical effects of drugs and reduce their side effects. Unfortunately, only a few targeted drug delivery systems can achieve high targeting efficiency after intravenous injection, even with the development of numerous surface markers and targeting modalities. Thus, alternative drug and nanomedicine targeting approaches are desired. Circulating cells, such as erythrocytes, leukocytes, and stem cells, present innate disease sensing and homing properties. Hence, using living cells as drug delivery carriers has gained increasing interest in recent years. This review highlights the recent advances in the design of cell-mediated drug delivery systems and targeting mechanisms. The approaches of drug encapsulation/conjugation to cell-carriers, cell-mediated targeting mechanisms, and the methods of controlled drug release are elaborated here. Cell-based "live" targeting and delivery could be used to facilitate a more specific, robust, and smart payload distribution for the next-generation drug delivery systems.

Stromal cells and stem cells in clinical bone regeneration

Stem-cell-mediated bone repair has been used in clinical trials for the regeneration of large craniomaxillofacial defects, to slow the process of bone degeneration in patients with osteonecrosis of the femoral head and for prophylactic treatment of distal tibial fractures. Successful regenerative outcomes in these investigations have provided a solid foundation for wider use of stromal cells in skeletal repair therapy. However, employing stromal cells to facilitate or enhance bone repair is far from being adopted into clinical practice. Scientific, technical, practical and regulatory obstacles prevent the widespread therapeutic use of stromal cells. Ironically, one of the major challenges lies in the limited understanding of the mechanisms via which transplanted cells mediate regeneration. Animal models have been used to provide insight, but these models largely fail to reproduce the nuances of human diseases and bone defects. Consequently, the development of targeted approaches to optimize cell-mediated outcomes is difficult. In this Review, we highlight the successes and challenges reported in several clinical trials that involved the use of bone-marrow-derived mesenchymal or adipose-tissue-derived stromal cells. We identify several obstacles blocking the mainstream use of stromal cells to enhance skeletal repair and highlight technological innovations or areas in which novel techniques might be particularly fruitful in continuing to advance the field of skeletal regenerative medicine.