Tendon injuries are common and present a clinical challenge to orthopedic surgery mainly because these injuries often respond poorly to treatment and require prolonged rehabilitation. Therapeutic options used to repair ruptured tendons have consisted of suture, autografts, allografts, and synthetic prostheses. To date, none of these alternatives has provided a successful long-term solution, and often the restored tendons do not recover their complete strength and functionality. Unfortunately, our understanding of tendon biology lags far behind that of other musculoskeletal tissues, thus impeding the development of new treatment options for tendon conditions. Hence, in this review, after introducing the clinical significance of tendon diseases and the present understanding of tendon biology, we describe and critically assess the current strategies for enhancing tendon repair by biological means. These consist mainly of applying growth factors, stem cells, natural biomaterials and genes, alone or in combination, to the site of tendon damage. A deeper understanding of how tendon tissue and cells operate, combined with practical applications of modern molecular and cellular tools could provide the long awaited breakthrough in designing effective tendon-specific therapeutics and overall improvement of tendon disease management.
Tendon; Tendon repair; Growth Factors; Cell-based therapy; Mesenchymal stem cells; Embryonic stem cells; Tendon-derived cells; Natural biomaterials; Gene therapy
Tissue engineering in urology has shown considerable promise. However, there is still much to understand, particularly regarding the interactions between scaffolds and their host environment, how these interactions regulate regeneration and how they may be enhanced for optimal tissue repair. In this review, we discuss the concept of dynamic reciprocity as applied to tissue engineering, i.e. how bi-directional signaling between implanted scaffolds and host tissues such as the bladder drives the process of constructive remodeling to ensure successful graft integration and tissue repair. The impact of scaffold content and configuration, the contribution of endogenous and exogenous bioactive factors, the influence of the host immune response and the functional interaction with mechanical stimulation are all considered. In addition, the temporal relationships of host tissue ingrowth, bioactive factor mobilization, scaffold degradation and immune cell infiltration, as well as the reciprocal signaling between discrete cell types and scaffolds are discussed. Improved understanding of these aspects of tissue repair will identify opportunities for optimization of repair that could be exploited to enhance regenerative medicine strategies for urology in future studies.
constructive remodeling; acellular matrix; cell-seeded construct; host response
Despite the potential of stem cells in cell-based therapy, major limitations such as cell retention, ingrowth, and trans-differentiation after implantation remain. One technique for genetic modification of cells for tissue repair is the introduction of specific genes using molecular biology techniques, such as virus integration, to provide a gene that adds new functions to enhance cellular function, and to secrete trophic factors for recruiting resident cells to participate in tissue repair. Stem cells can be labelled to track cell survival, migration, and lineage. Increasing evidence demonstrates that cell therapy and gene therapy in combination remarkably improve myogenic differentiation of implanted mesenchymal stromal cells (MSCs), revascularization, and innervation in genitourinary tissues, especially to treat urinary incontinence, erectile dysfunction, lower urinary tract reconstruction, and renal failure. This review discusses the benefits, safety, side effects, and alternatives for using genetically modified MSCs in tissue regeneration in andro-urology.
Stem cells; cell therapy; gene therapy; urinary incontinence; skeletal muscle genesis; innervation; angiogenesis; erectile dysfunction; endothelial cells
Mesenchymal stem cells (MSC) are a unique cell population defined by their ability to indefinitely self-renew, differentiate into multiple cell lineages, and form clonal cell populations. It was originally thought that this ability for broad plasticity defined the therapeutic potential of MSCs. However, an expanding body of recent literature has brought growing awareness to the remarkable array of bioactive molecules produced by stem cells. This protein milieu or “secretome” comprises a diverse host of cytokines, chemokines, angiogenic factors, and growth factors. The autocrine/paracrine role of these molecules is being increasingly recognized as key to the regulation of many physiological processes including directing endogenous and progenitor cells to sites of injury as well as mediating apoptosis, scarring, and tissue revascularization. In fact, the immunomodulatory and paracrine role of these molecules may predominantly account for the therapeutic effects of MSCs given that many in vitro and in vivo studies have demonstrated limited stem cell engraftment at the site of injury. While the study of such a vast protein array remains challenging, technological advances in the field of proteomics have greatly facilitated our ability to analyze and characterize the stem cell secretome. Thus, stem cells can be considered as tunable pharmacological storehouses useful for combinatorial drug manufacture and delivery. As a cell-free option for regenerative medicine therapies, stem cell secretome has shown great potential in a variety of clinical applications including the restoration of function in cardiovascular, neurodegenerative, oncologic, and genitourinary pathologies.
Secretions; mesenchymal stem cells; tissue engineering; regenerative medicine; systemic therapy; mechanism of action
The phrase “bench to bedside” is commonly used to describe the translation of basic discoveries such as those on stem cells to the clinic for therapeutic use in human patients. However, there is a key intermediate step in between the bench and the bedside involving governmental regulatory oversight such as by the Food and Drug Administration (FDA) in the United States (US). Thus, it might be more accurate in most cases to describe the stem cell biological drug development process in this way: from bench to FDA to bedside. The intermediate development and regulatory stage for stem cell-based biological drugs is a multifactorial, continually evolving part of the process of developing a biological drug such as a stem cell-based regenerative medicine product. In some situations, stem cell-related products may not be classified as biological drugs in which case the FDA plays a relatively minor role. However, this middle stage is generally a major element of the process and is often colloquially referred to in an ominous way as “The Valley of Death”. This moniker seems appropriate because it is at this point and in particular in the work that ensues after Phase 1 clinical trials that most drug product development is terminated, often due to lack of funding, diseases being refractory to treatment, or regulatory issues. Not surprisingly, workarounds to deal with or entirely avoid this difficult stage of the process are evolving both inside and outside the domains of official regulatory authorities. In some cases these efforts involve the FDA invoking new mechanisms of accelerating the bench to beside process, but in other cases these new pathways bypass the FDA in part or entirely. Together these rapidly changing stem cell product development and regulatory pathways raise many scientific, ethical, and medical questions. These emerging trends and their potential consequences are reviewed here.
MicroRNAs (miRNAs) not only directly regulate NF-κB expression, but also up- or down-regulate NF-κB activity via upstream and downstream signaling pathways of NF-κB. In many cancer cells, miRNA expressions are altered accompanied with an elevation of NF-κB, which often plays a role in promoting cancer development and progression as well as hindering the effectiveness of chemo and radiation therapies. Thus NF-κB-targeting miRNAs have been identified and characterized as potential therapeutics for cancer treatment and sensitizers of chemo and radiotherapies. However, due to cross-targeting and instability of miRNAs, some limitations of using miRNA as cancer therapeutics still exist. In this review, the mechanisms for miRNA-mediated alteration of NF-κB expression and activation in different types of cancers will be discussed. The results of therapeutic use of NF-κB-targeting miRNA for cancer treatment will be examined. Some limitations, challenges and potential strategies in future development of miRNA as cancer therapeutics are also assessed.
miRNA; NF-κB; cancer; therapeutics
Despite enormous efforts, cancer remains one of the most lethal diseases in the world. With the advancement of high throughput technologies massive amounts of cancer data can be accessed and analyzed. Bioinformatics provides a platform to assist biologists in developing minimally invasive biomarkers to detect cancer, and in designing effective personalized therapies to treat cancer patients. Still, the early diagnosis, prognosis, and treatment of cancer are an open challenge for the research community. MicroRNAs (miRNAs) are small non-coding RNAs that serve to regulate gene expression. The discovery of deregulated miRNAs in cancer cells and tissues has led many to investigate the use of miRNAs as potential biomarkers for early detection, and as a therapeutic agent to treat cancer. Here we describe advancements in computational approaches to predict miRNAs and their targets, and discuss the role of bioinformatics in studying miRNAs in the context of human cancer.
microRNAs; miRNAs; therapy; bioinformatics; computational model; pancreatic cancer
Increasing evidence sustains that the establishment and maintenance of many, if not all, human cancers are due to cancer stem cells (CSCs), tumor cells with stem cell properties, such as the capacity to self-renew or generate progenitor and differentiated cells. CSCs seem to play a major role in tumor metastasis and drug resistance but, albeit the potential clinical importance, their regulation at the molecular level is not clear. Recent studies have highlighted several miRNAs to be differentially expressed in normal and cancer stem cells and established their role in targeting genes and pathways supporting cancer stemness properties. This review focuses on the last advances on the role of microRNAs in the regulation of stem cell properties and cancer stem cells in different tumors.
One of the most fascinating discoveries in molecular oncology has been that cancer represents a disease in which genetic alterations in protein-coding, but also in non-coding genes complement each other. MicroRNAs (miRNAs) are a type of non-coding RNA (ncRNA) transcripts that can regulate gene expression primarily by disrupting messenger RNA (mRNA) translation and/or stability, or alternatively by modulating the transcription of target mRNAs. For the last decade, miRNAs have shown to be pivotal characters of every single one of the cancer hallmarks. Profiling studies have proven the significance of identifying over-expressed miRNAs (oncomiRs) causative of the activation of oncogenic pathways that lead to malignancy. Due to their crucial role in cancer, it has become a challenge to develop efficient miRNA-inhibiting strategies such as antagomiRs, locked nucleic acids or antisense oligonucleotides. However, to this date, the accessible delivery agents and their pharmacokinetic/pharmacodynamic properties are not ideal. Thus there is an urgent, unmet need to develop miRNA-based inhibitory therapeutics. Herein we present a novel therapeutic strategy that is only at the tip of the iceberg: the use of small molecule inhibitors to target specific miRNAs (SMIRs). Furthermore we describe several high-throughput techniques to screen for SMIRs both in vitro and in silico. Finally we take you through the journey that has led to discovering the handful of SMIRs that have been validated to this date.
microRNAs; small molecules; targeted therapies; non-coding RNAs; cancer
Despite considerable progress being made in understanding pancreatic cancer (PC) pathogenesis, it still remains the 10th most often diagnosed malignancy in the world and 4th leading cause of cancer related deaths in the United States with a five year survival rate of only 6%. The aggressive nature, lack of early diagnostic and prognostic markers, late clinical presentation, and limited efficacy of existing treatment regimens makes PC a lethal cancer with high mortality and poor prognosis. Therefore, novel reliable biomarkers and molecular targets are urgently needed to combat this deadly disease. MicroRNAs (miRNAs) are short (19–24 nucleotides) non-coding RNA molecules implicated in the regulation of gene expression at post-transcriptional level and play significant roles in various physiological and pathological conditions. Aberrant expression of miRNAs has been reported in several cancers including PC and is implicated in PC pathogenesis and progression, suggesting their utility in diagnosis, prognosis and therapy. In this review, we summarize the role of several miRNAs that regulate various oncogenes (KRAS) and tumor suppressor genes (p53, p16, SMAD4 etc) involved in PC development, their prospective roles as diagnostic and prognostic markers and their therapeutic targets.
A growing number of failing clinical trials for cancer therapy is substantiating the need to upgrade the current practice in culturing tumor cells and modeling tumor angiogenesis in vitro. Many attempts have been made to engineer vasculature in vitro by utilizing hydrogels, but the application of these tools in simulating in vivo tumor angiogenesis is still very new. In this review, we explore current use of hydrogels and their design parameters to engineer vasculogenesis and angiogenesis and to evaluate the angiogenic capability of cancerous cells and tissues. When coupled with other technologies such as lithography and three-dimensional printing, one can even create an advanced microvessel model as microfluidic channels to more accurately capture the native angiogenesis process.
Angiogenesis; Hydrogel; Tumor modeling; Three-dimensional cell culture; ECM remodeling
Despite advances in medicine and biomedical sciences, cancer still remains a major health issue. Complex interactions between tumors and their microenvironment contribute to tumor initiation and progression and also contribute to the development of drug resistant tumor cell populations. The complexity and heterogeneity of tumors and their microenvironment make it challenging to both study and treat cancer. Traditional animal cancer models and in vitro cancer models are limited in their ability to recapitulate human structures and functions, thus hindering the identification of appropriate drug targets and therapeutic strategies. The development and application of microfluidic 3D cancer models has the potential to overcome some of the limitations inherent to traditional models. This review summarizes the progress in microfluidic 3D cancer models, their benefits, and their broad application to basic cancer biology, drug screening, and drug discovery.
Microfluidics; 3D in vitro system; Cancer; Tumor microenvironment; Biomimetics; High-throughput screening; Drug testing
Glioblastoma multiforme (GBM) is the most common and deadly brain tumor, with a mean survival time of only 21 months. Despite the dramatic improvements in our understanding of GBM fueled by recent revolutions in molecular and systems biology, treatment advances for GBM have progressed inadequately slowly, which is due in part to the wide cellular and molecular heterogeneity both across tumors and within a single tumor. Thus, there is increasing clinical interest in targeting cell-extrinsic factors as way of slowing or halting the progression of GBM. These cell-extrinsic factors, collectively termed the microenvironment, include the extracellular matrix, blood vessels, stromal cells that surround tumor cells, and all associated soluble and scaffold-bound signals. In this review, we will first describe the regulation of GBM tumors by these microenvironmental factors. Next, we will discuss the various in vitro approaches that have been exploited to recapitulate and model the GBM tumor microenvironment in vitro. We conclude by identifying future challenges and opportunities in this field, including the development of microenvironmental platforms amenable to high-throughput discovery and screening. We anticipate that these ongoing efforts will prove to be valuable both as enabling tools for accelerating our understanding of microenvironmental regulation in GBM and as foundations for next-generation molecular screening platforms that may serve as a conceptual bridge between traditional reductionist systems and animal or clinical studies.
Bone metastasis represents the leading cause of breast cancer related-deaths. However, the effect of skeleton-associated biomechanical signals on the initiation, progression, and therapy response of breast cancer bone metastasis is largely unknown. This review seeks to highlight possible functional connections between skeletal mechanical signals and breast cancer bone metastasis and their contribution to clinical outcome. It provides an introduction to the physical and biological signals underlying bone functional adaptation and discusses the modulatory roles of mechanical loading and breast cancer metastasis in this process. Following a definition of biophysical design criteria, in vitro and in vivo approaches from the fields of bone biomechanics and tissue engineering will be reviewed that may be suitable to investigate breast cancer bone metastasis as a function of varied mechano-signaling. Finally, an outlook of future opportunities and challenges associated with this newly emerging field will be provided.
New models for epithelial ovarian cancer initiation and metastasis are required to obtain a mechanistic understanding of the disease and to develop new therapeutics. Modeling ovarian cancer however is challenging as a result of the genetic heterogeneity of the malignancy, the diverse pathology, the limited availability of human tissue for research, the atypical mechanisms of metastasis, and because the origin is unclear. Insights into the origin of high-grade serous ovarian carcinomas and mechanisms of metastasis have resulted in the generation of novel three-dimensional (3D) culture models that better approximate the behavior of the tumor cells in vivo than prior two-dimensional models. The 3D models aim to recapitulate the tumor microenvironment, which has a critical role in the pathogenesis of ovarian cancer. Ultimately, findings using models that accurately reflect human ovarian cancer biology are likely to translate into improved clinical outcomes. In this review we discuss the design of new 3D culture models of ovarian cancer primarily using human cells, key studies in which these models have been applied, current limitations, and future applications.
Tumor microenvironment; 3D models; Metastasis; Ovarian cancer; Breast cancer; Melanoma; Fallopian tube
Many currently used antibiotics suffer from issues such as systemic toxicity, short half-life, and increased susceptibility to bacterial resistance. Although most antibiotic classes are administered systemically through oral or intravenous routes, a more efficient delivery system is needed. This review discusses the chemical conjugation of antibiotics to polymers, achieved by forming covalent bonds between antibiotics and a pre-existing polymer or by developing novel antibiotic-containing polymers. Through conjugating antibiotics to polymers, unique polymer properties can be taken advantage of. These polymeric antibiotics display controlled, sustained drug release and vary in antibiotic class type, synthetic method, polymer composition, bond lability, and antibacterial activity. The polymer synthesis, characterization, drug release, and antibacterial activities, if applicable, will be presented to offer a detailed overview of each system.
polymer conjugates; controlled release; sustained release; localized delivery antibiotics; biocompatible
Infectious diseases are the leading cause of death worldwide. Among them, tuberculosis (TB) remains a major threat to public health, exacerbated by the emergence of multiple drug-resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis (Mtb). MDR-Mtb strains are resistant to first-line anti-TB drugs such as isoniazid and rifampicin; whereas XDR-Mtb strains are resistant to additional drugs including at least to any fluoroquinolone and at least one of the second-line anti-TB injectable drugs such as kanamycin, capreomycin, or amikacin. Clinically, these strains have significantly impacted the management of TB in high-incidence developing countries, where systemic surveillance of TB drug resistance is lacking. For effective management of TB on-site, early detection of drug resistance is critical to initiate treatment, to reduce mortality, and to thwart drug-resistant TB transmission. In this review, we discuss the diagnostic challenges to detect drug-resistant TB at the point-of-care (POC). Moreover, we present the latest advances in nano/microscale technologies that can potentially detect TB drug resistance to improve on-site patient care.
Tuberculosis; Drug resistance; Diagnostics; Nano/microscale technologies; Point-of Care
To maximize tumor excision and minimize collateral damage is the primary goal of cancer surgery. Emerging molecular imaging techniques have to “image-guided surgery” developing into “molecular imaging-guided surgery”, which is termed “targeted surgery” in this review. Consequently, the precision of surgery can be advanced from tissue-scale to molecule-scale, enabling “targeted surgery” to be a component of “targeted therapy”. Evidence from numerous experimental and clinical studies has demonstrated significant benefits of fluorescent imaging in targeted surgery with preoperative molecular diagnostic screening. Fluorescent imaging can help to improve intraoperative staging and enable more radical cytoreduction, detect obscure tumor lesions in special organs, highlight tumor margins, better map lymph node metastases, and identify important normal structures intraoperatively. Though limited tissue penetration of fluorescent imaging and tumor heterogeneity are two major hurdles for current targeted surgery, multimodality imaging and multiplex imaging may provide potential solutions to overcome these issues, respectively. Moreover, though many fluorescent imaging techniques and probes have been investigated, targeted surgery remains at a proof-of-principle stage. The impact of fluorescent imaging on cancer surgery will likely be realized through persistent interdisciplinary amalgamation of research in diverse fields.
Targeted therapy; Targeted surgery; Molecular imaging; Fluorescent imaging; Image-guided surgery; Multimodality imaging; Multiplex imaging; System molecular imaging
Targeted nanoparticle imaging agents provide many benefits and new opportunities to facilitate accurate diagnosis of cancer and significantly impact patient outcome. Due to the highly engineerable nature of nanotechnology, targeted nanoparticles exhibit significant advantages including increased contrast sensitivity, binding avidity and targeting specificity. Considering the various nanoparticle designs and their adjustable ability to target a specific site and generate detectable signals, nanoparticles can be optimally designed in terms of biophysical interactions (i.e., intravascular and interstitial transport) and biochemical interactions (i.e., targeting avidity towards cancer-related biomarkers) for site-specific detection of very distinct microenvironments. This review seeks to illustrate that the design of a nanoparticle dictates its in vivo journey and targeting of hard-to-reach cancer sites, facilitating early and accurate diagnosis and interrogation of the most aggressive forms of cancer. We will report various targeted nanoparticles for cancer imaging using X-ray computed tomography, ultrasound, magnetic resonance imaging, nuclear imaging and optical imaging. Finally, to realize the full potential of targeted nanotechnology for cancer imaging, we will describe the challenges and opportunities for the clinical translation and widespread adaptation of targeted nanoparticles imaging agents.
Targeted nanoparticles; cancer imaging; MRI; CT; ultrasound; PET; SPECT; optical imaging
Tremendous advances over the last several decades in positron emission tomography (PET) and single photon emission computed tomography (SPECT) allow for targeted imaging of molecular and cellular events in the living systems. Angiogenesis, a multistep process regulated by the network of different angiogenic factors, has attracted world-wide interests, due to its pivotal role in the formation and progression of different diseases including cancer, cardiovascular diseases (CVD), and inflammation. In this review article, we will summarize the recent progress in PET or SPECT imaging of a wide variety of vascular targets in three major angiogenesis-related diseases: cancer, cardiovascular diseases, and inflammation. Faster drug development and patient stratification for a specific therapy will become possible with the facilitation of PET or SPECT imaging and it will be critical for the maximum benefit of patients.
Angiogenesis; positron emission tomography (PET); single-photon emission computed tomography (SPECT); cancer; cardiovascular disease; inflammation
RNA interference (RNAi) has been thought of as the general answer to many unmet medical needs. After the first success stories, it soon became obvious that short interfering RNA (siRNA) is not suitable for systemic administration due to its poor pharmacokinetics. Therefore local administration routes have been adopted for more successful in vivo RNAi. This paper reviews nucleic acid modifications, nanocarrier chemistry, animal models used in successful pulmonary siRNA delivery, as well as clinical translation approaches. We summarize what has been published recently and conclude with the potential problems that may still hamper the efficient clinical application of RNAi in the lung.
siRNA; pulmonary delivery; nanocarrier; polymer; lung cancer; asthma
Small interfering RNAs (siRNA) have recently emerged as a new class of therapeutics with a great potential to revolutionize the treatment of cancer and other diseases. A specifically designed siRNA binds and induces post-transcriptional silencing of target genes (mRNA). Clinical applications of siRNA-based therapeutics have been limited by their rapid degradation, poor cellular uptake, and rapid renal clearance following systemic administration. A variety of synthetic and natural nanoparticles composed of lipids, polymers, and metals have been developed for siRNA delivery, with different efficacy and safety profiles. Liposomal nanoparticles have proven effective in delivering siRNA into tumor tissues by improving stability and bioavailability. While providing high transfection efficiency and a capacity to form complexes with negatively charged siRNA, cationic lipids/liposomes are highly toxic. Negatively charged liposomes, on the other hand, are rapidly cleared from circulation. To overcome these problems we developed highly safe and effective neutral lipid-based nanoliposomes that provide robust gene silencing in tumors following systemic (intravenous) administration. This delivery system demonstrated remarkable antitumor efficacy in various orthotopic human cancer models in animals. Here, we briefly overview this and other lipid-based approaches with preclinical applications in different tumor models for cancer therapy and potential applications as siRNA-nanotherapeutics in human cancers.
siRNA; liposomes; nanovectors; delivery; cancer; gene silencing; targeted therapies
Increasing numbers of paediatric patients with congenital heart defects are surviving to adulthood, albeit with continuing clinical needs. Hence, there is still scope for revolutionary new strategies to correct vascular anatomical defects. Adult patients are also surviving longer with the adverse consequences of ischemic vascular disease, especially after acute coronary syndromes brought on by plaque erosion and rupture. Vascular tissue engineering and therapeutic angiogenesis provide new hope for these patients. Both approaches have shown promise in laboratory studies, but have not yet been able to deliver clear evidence of clinical success. More research into biomaterials, molecular medicine and cell and molecular therapies is necessary. This review article focuses on the new opportunities offered by targeting microRNAs for the improved production and greater empowerment of vascular cells for use in vascular tissue engineering or for increasing blood perfusion of ischemic tissues by amplifying the resident microvascular network.
Schematic of application of miRs in vascular tissue engineering. Cells from patient could be collected, expanded and be subjected to miR modulation strategies to generate cells of desired specification. Pluripotent stem cells can be modulated to inhibit self-renewal and promote differentiation toward a desired progenitor cell. Also miR modulation of the progenitor cells may permit maintenance of the cells in a progenitor state or differentiation toward specific progeny thereby facilitating a modular cell therapy strategy. The modified cells can be loaded onto scaffolds for implantation or can be used to generate intact tissues and organs in vitro before implantation in the patient. MiR modification strategies can also be used directly in ischemic tissues to regulate angiogenesis. Extracellular vesicles (EVs) carrying the ‘desired’ cargo of miR can be isolated from stem or progenitor cells for direct injection into ischemic tissue.
BM, bone marrow; CAD, coronary artery disease; CHD, congenital heart disease; CLI, critical limb ischemia; EC, endothelial cell; EPCs, endothelial progenitor cells; ECM, extracellular matrix; ESC, embryonic stem cell; GF, growth factor; IHD, ischemic heart disease; miR, microRNA; MI, myocardial infarction; MNC, mononuclear cell; NP, nanoparticle; PAC, proangiogenic circulating cell; PAD, peripheral arterial disease; MMP, matrix metalloproteinase; VSMC, vascular smooth muscle cell; TE, tissue engineering; VTE, vascular tissue engineering; MicroRNAs; Vascular tissue engineering; Therapeutic angiogenesis; Congenital/acquired heart disease; Aneurysms; Ischemic disease