Julia D. Ransohoff

Short-Term Immunosuppression Promotes Engraftment of Embryonic and Induced Pluripotent Stem Cells

Embryonic stem cells (ESCs) are an attractive source for tissue regeneration and repair therapies because they can be differentiated into virtually any cell type in the adult body. However, for this approach to succeed, the transplanted ESCs must survive long enough to generate a therapeutic benefit. A major obstacle facing the engraftment of ESCs is transplant rejection by the immune system. Here we show that blocking leukocyte costimulatory molecules permits ESC engraftment. We demonstrate the success of this immunosuppressive therapy for mouse ESCs, human ESCs, mouse induced pluripotent stem cells (iPSCs), human induced pluripotent stem cells, and more differentiated ESC/(iPSCs) derivatives. Additionally, we provide evidence describing the mechanism by which inhibition of costimulatory molecules suppresses T cell activation. This report describes a short-term immunosuppressive approach capable of inducing engraftment of transplanted ESCs and iPSCs, providing a significant improvement in our mechanistic understanding of the critical role costimulatory molecules play in leukocyte activation.

Immunogenicity of Pluripotent Stem Cells and Their Derivatives

The ability of pluripotent stem cells to self-renew and differentiate into all somatic cell types brings great prospects to regenerative medicine and human health. However, before clinical applications, much translational research is necessary to ensure that their therapeutic progenies are functional and nontumorigenic, that they are stable and do not dedifferentiate, and that they do not elicit immune responses that could threaten their survival in vivo. For this, an in-depth understanding of their biology, genetic, and epigenetic make-up and of their antigenic repertoire is critical for predicting their immunogenicity and for developing strategies needed to assure successful long-term engraftment. Recently, the expectation that reprogrammed somatic cells would provide an autologous cell therapy for personalized medicine has been questioned. Induced pluripotent stem cells display several genetic and epigenetic abnormalities that could promote tumorigenicity and immunogenicity in vivo. Understanding the persistence and effects of these abnormalities in induced pluripotent stem cell derivatives is critical to allow clinicians to predict graft fate after transplantation, and to take requisite measures to prevent immune rejection. With clinical trials of pluripotent stem cell therapy on the horizon, the importance of understanding immunologic barriers and devising safe, effective strategies to bypass them is further underscored. This approach to overcome immunologic barriers to stem cell therapy can take advantage of the validated knowledge acquired from decades of hematopoietic stem cell transplantation.

In Vivo Functional and Transcriptional Profiling of Bone Marrow Stem Cells After Transplantation Into Ischemic Myocardium

Objective— Clinical trials of bone marrow–derived stem cell therapy for the heart have yielded variable results. The basic mechanism(s) that underlies their potential efficacy remains unknown. In the present study, we evaluated the survival kinetics, transcriptional response, and functional outcome of intramyocardial bone marrow mononuclear cell (BMMC) transplantation for cardiac repair in a murine myocardial infarction model. Methods and Results— We used bioluminescence imaging and high-throughput transcriptional profiling to evaluate the in vivo survival kinetics and gene expression changes of transplanted BMMCs after their engraftment into ischemic myocardium. Our results demonstrate short-lived survival of cells following transplant, with less than 1% of cells surviving by 6 weeks posttransplantation. Moreover, transcriptomic analysis of BMMCs revealed nonspecific upregulation of various cell regulatory genes, with a marked downregulation of cell differentiation and maturation pathways. BMMC therapy caused limited improvement of heart function as assessed by echocardiography, invasive hemodynamics, and positron emission tomography. Histological evaluation of cell fate further confirmed findings of the in vivo cell tracking and transcriptomic analysis. Conclusion— Collectively, these data suggest that BMMC therapy, in its present iteration, may be less efficacious than once thought. Additional refinement of existing cell delivery protocols should be considered to induce better therapeutic efficacy.

Costimulation-adhesion blockade is superior to cyclosporine A and prednisone immunosuppressive therapy for preventing rejection of differentiated human embryonic stem cells following transplantation.

Rationale: Human embryonic stem cell (hESC) derivatives are attractive candidates for therapeutic use. The engraftment and survival of hESC derivatives as xenografts or allografts require effective immunosuppression to prevent immune cell infiltration and graft destruction. Objective: To test the hypothesis that a short‐course, dual‐agent regimen of two costimulation‐adhesion blockade agents can induce better engraftment of hESC derivatives compared to current immunosuppressive agents. Methods and Results: We transduced hESCs with a double fusion reporter gene construct expressing firefly luciferase (Fluc) and enhanced green fluorescent protein, and differentiated these cells to endothelial cells (hESC‐ECs). Reporter gene expression enabled longitudinal assessment of cell engraftment by bioluminescence imaging. Costimulation‐adhesion therapy resulted in superior hESC‐EC and mouse EC engraftment compared to cyclosporine therapy in a hind limb model. Costimulation‐adhesion therapy also promoted robust hESC‐EC and hESC‐derived cardiomyocyte survival in an ischemic myocardial injury model. Improved hESC‐EC engraftment had a cardioprotective effect after myocardial injury, as assessed by magnetic resonance imaging. Mechanistically, costimulation‐adhesion therapy is associated with systemic and intragraft upregulation of T‐cell immunoglobulin and mucin domain 3 (TIM3) and a reduced proinflammatory cytokine profile. Conclusions: Costimulation‐adhesion therapy is a superior alternative to current clinical immunosuppressive strategies for preventing the post‐transplant rejection of hESC derivatives. By extending the window for cellular engraftment, costimulation‐adhesion therapy enhances functional preservation following ischemic injury. This regimen may function through a TIM3‐dependent mechanism. Stem Cells 2013;31:2354–2363

The functions and unique features of long intergenic non-coding RNA

Long intergenic non-coding RNA (lincRNA) genes have diverse features that distinguish them from mRNA-encoding genes and exercise functions such as remodelling chromatin and genome architecture, RNA stabilization and transcription regulation, including enhancer-associated activity. Some genes currently annotated as encoding lincRNAs include small open reading frames (smORFs) and encode functional peptides and thus may be more properly classified as coding RNAs. lincRNAs may broadly serve to fine-tune the expression of neighbouring genes with remarkable tissue specificity through a diversity of mechanisms, highlighting our rapidly evolving understanding of the non-coding genome.

Tracking gene and cell fate for therapeutic gain

The preclinical intersection of molecular imaging and gene- and cell-based therapies will enable more informed and effective clinical translation. We discuss how imaging can monitor cell and gene fate and function in vivo and overcome barriers associated with these therapies.

CALML5 is a ZNF750- and TINCR-induced protein that binds stratifin to regulate epidermal differentiation

Outward migration of epidermal progenitors occurs with induction of hundreds of differentiation genes, but the identities of all regulators required for this process are unknown. We used laser capture microdissection followed by RNA sequencing to identify calmodulin-like 5 (CALML5) as the most enriched gene in differentiating outer epidermis. CALML5 mRNA was up-regulated by the ZNF750 transcription factor and then stabilized by the long noncoding RNA TINCR. CALML5 knockout impaired differentiation, abolished keratohyalin granules, and disrupted epidermal barrier function. Mass spectrometry identified SFN (stratifin/14-3-3σ) as a CALML5-binding protein. CALML5 interacts with SFN in suprabasal epidermis, cocontrols 13% of late differentiation genes, and modulates interaction of SFN to some of its binding partners. A ZNF750-TINCR-CALML5-SFN network is thus essential for epidermal differentiation.

Imaging stem cell therapy for the treatment of peripheral arterial disease.

Arteriosclerotic cardiovascular diseases are among the leading causes of morbidity and mortality worldwide. Therapeutic angiogenesis aims to treat ischemic myocardial and peripheral tissues by delivery of recombinant proteins, genes, or cells to promote neoangiogenesis. Concerns regarding the safety, side effects, and efficacy of protein and gene transfer studies have led to the development of cell-based therapies as alternative approaches to induce vascular regeneration and to improve function of damaged tissue. Cell-based therapies may be improved by the application of imaging technologies that allow investigators to track the location, engraftment, and survival of the administered cell population. The past decade of investigations has produced promising clinical data regarding cell therapy, but design of trials and evaluation of treatments stand to be improved by emerging insight from imaging studies. Here, we provide an overview of pre-clinical and clinical experience using cell-based therapies to promote vascular regeneration in the treatment of peripheral arterial disease. We also review four major imaging modalities and underscore the importance of in vivo analysis of cell fate for a full understanding of functional outcomes.

Health Cards by Google: dermatologist review of inclusivity and utility of the medical search application

One in twenty Google web searches are related to medical conditions1 indicating the prominent role of the internet as a resource for medical information. Indeed, 72% of internet users report searching online for medical conditions; 77% began with Google, Bing, or Yahoo.2 While 53% additionally sought physician consultation, 46% did not.3 Responding to its place in the medical community, in 2015 Google partnered with academic, government, and business-based ventures to develop “health cards” for searched disorders, and, in summer 2016, debuted a “related conditions” generator, suggesting diagnoses related to input disorders or symptoms. This article is protected by copyright. All rights reserved.

Assessment of Accuracy of Patient-Initiated Differential Diagnosis Generation by Google Reverse Image Searching.

Assessment of Accuracy of Patient-Initiated Differential Diagnosis Generation by Google Reverse Image Searching Google users are increasingly web searching medical concerns; these search results hold the potential to influence outreach to clinicians by offering reassurance or generating concern. Accurate web information is therefore critical. For nondermatologic concerns, these web queries are via text cues. For dermatologic concerns, however, patients often lack the linguistic descriptors to accurately inform and narrow their searches. Google Reverse Image Search permits users to upload an image and search for similar images and content. We soon anticipate greater user adoption of Google Reverse Image Search to aid in self-identification of skin lesions, as well as a role for this technology to serve as adjunct to clinical dermatologic expertise, given that patients inevitably do web search their concerns before, during, and after clinical dermatologic consultation. While potentially informative, the results of such searches may generate concern and missed diagnoses may have severe implications. We thus queried Google’s ability to accurately identify similar images with matched diagnoses.