Lauren S. Sherman

Immunological properties of mesenchymal stem cells and clinical implications

The rapid evolution of experimental data has acknowledged the critical relevance of immune biology in stem cell research. It appears that efficient transfer of stem cells to patients requires robust analyses of the immune properties as well as the responses of the stem cells to immune mediators. This review discusses the biology of adult human mesenchymal stem cells (MSCs) in the context of immunology. MSCs are pluripotent, self-renewing cells with the potential for tissue regeneration, for example the repair of bone, cartilage, tendon, ligament, skeletal muscle, and cardiac muscle. MSCs have also been shown to transdifferentiate into cells of ectodermal origin, such as neurons. MSCs are located in perfused areas of adult bone marrow, whereas hematopoietic stem cells are located in poorly perfused areas of the same organ. MSCs show bimodal, i.e. anti-inflammatory and immune-enhancing, immune responses. MSCs also regulate immune responses such as the regulation of antibody production by B cells, alterations in T cell subtypes, and immune tolerance of allogeneic transplants. MSCs also have the potential for gene delivery. This review explores the diverse clinical potential for MSCs and discusses the limitations and advantages of their immunomodulatory properties.

Stem cell delivery of therapies for brain disorders.

The blood brain barrier (BBB) poses a problem to deliver drugs for brain malignancies and neurodegenerative disorders. Stem cells such as neural stem cells (NSCs) and mesenchymal stem cells (MSCs) can be used to delivery drugs or RNA to the brain. This use of methods to bypass the hurdles of delivering drugs across the BBB is particularly important for diseases with poor prognosis such as glioblastoma multiforme (GBM). Stem cell treatment to deliver drugs to neural tumors is currently in clinical trial. This method, albeit in the early phase, could be an advantage because stem cells can cross the BBB into the brain. MSCs are particularly interesting because to date, the experimental and clinical evidence showed ‘no alarm signal’ with regards to safety. Additionally, MSCs do not form tumors as other more primitive stem cells such as embryonic stem cells. More importantly, MSCs showed pathotropism by migrating to sites of tissue insult. Due to the ability of MSCs to be transplanted across allogeneic barrier, drug-engineered MSCs can be available as off-the-shelf cells for rapid transplantation. This review discusses the advantages and disadvantages of stem cells to deliver prodrugs, genes and RNA to treat neural disorders.

Mesenchymal stromal/stem cells in drug therapy: New perspective.

Mesenchymal stromal/stem cells (MSC) have emerged as a class of cells suitable for cellular delivery of nanoparticles, drugs and micro-RNA cargo for targeted treatments such as tumor and other protective mechanisms. The special properties of MSC underscore the current use for various clinical applications. Examples of applications include but are not limited to regenerative medicine, immune disorders and anti-cancer therapies. In recent years, there has been intense research in modifying MSC to achieve targeted and efficient clinical outcomes. This review discusses effects of MSC in an inflammatory microenvironment and then explains how these properties could be important to the overall application of MSC in cell therapy. The article also advises caution in the application of these cells because of their role in tumorigenesis. The review stresses the use of MSC as vehicles for drug delivery and discusses the accompanying challenges, based on the influence of the microenvironment on MSC.

Feline bone marrow-derived mesenchymal stromal cells (MSCs) show similar phenotype and functions with regards to neuronal differentiation as human MSCs☆

Mesenchymal stromal cells (MSCs) show promise for treatment of a variety of neurological and other disorders. Cat has a high degree of linkage with the human genome and has been used as a model for analysis of neurological disorders such as stroke, Alzheimers disease and motor disorders. The present study was designed to characterize bone marrow-derived MSCs from cats and to investigate the capacity to generate functional peptidergic neurons. MSCs were expanded with cells from the femurs of cats and then characterized by phenotype and function. Phenotypically, feline and human MSCs shared surface markers, and lacked hematopoietic markers, with similar morphology. As compared to a subset of human MSCs, feline MSCs showed no evidence of the major histocompatibility class II. Since the literature suggested Stro-1 as an indicator of pluripotency, we compared early and late passages feline MSCs and found its expression in >90% of the cells. However, the early passage cells showed two distinct populations of Stro-1-expressing cells. At passage 5, the MSCs were more homogeneous with regards to Stro-1 expression. The passage 5 MSCs differentiated to osteogenic and adipogenic cells, and generated neurons with electrophysiological properties. This correlated with the expression of mature neuronal markers with concomitant decrease in stem cell-associated genes. At day 12 induction, the cells were positive for MAP2, Neuronal Nuclei, tubulin βIII, Tau and synaptophysin. This correlated with electrophysiological maturity as presented by excitatory postsynaptic potentials (EPSPs). The findings indicate that the cat may constitute a promising biomedical model for evaluation of novel therapies such as stem cell therapy in such neurological disorders as Alzheimers disease and stroke.

Shift toward Mechanical Isolation of Adipose-derived Stromal Vascular Fraction: Review of Upcoming Techniques

Background: Standard isolation of adipose stromal vascular fraction (SVF) requires the use of collagenase and is considered more than “minimally manipulated” by current good manufacturing practice requirements. Alternatively, nonenzymatic isolation methods have surfaced using physical forces to separate cells from the adipose matrix. The purpose of this study was to review the literature on the use of mechanical isolation protocols and compare the results. The implication for use as a standard procedure in practice is discussed. Methods: A systematic review of the literature was performed on mechanical isolation of SVF with a search of six terms on PubMed and Medline databases. One thousand sixty-six articles were subject to evaluation by predetermined inclusion and exclusion criteria. Results: Two level 2 evidence articles and 7 in vitro studies were selected. SVF was isolated using automated closed systems or by subjecting the lipoaspirate to centrifugation only or by shaking or vortexing followed by centrifugation. Six articles reported isolation in laboratory settings and three inside the operating room. Stromal vascular cells expressed CD34, and CD44, CD73, CD90, and CD105, and differentiated along adipogenic and osteogenic lineages. When compared with enzymatic methods, mechanical isolation required less time but yielded fewer cells. Both case–control studies reported improved volume retention with cell-supplemented fat grafts for breast reconstruction. Conclusions: Mechanical isolation methods are alternatives to circumvent safety issues posed by enzymatic protocols. However, randomized comparative studies with long-term clinical outcomes using mechanically isolated stromal vascular cells are needed to identify their ideal clinical applications.

Enzyme-Free Isolation of Adipose-Derived Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are a population of multipotent cells that can be isolated from various adult and fetal tissues, including adipose tissue. These cells contain enormous clinical and basic research appeal due to their plasticity to differentiate into cells of all germ layers in vitro, cross allogeneic barriers in vivo, and suppress inflammation. Methods to isolate adipose-derived MSCs (ADSCs) primarily rely on enzymatic digestion of the adipose tissue using harsh enzymes such as collagenase. However, these harsh enzymes are expensive and can have detrimental effects on the ADSCs, including risks of using xenograft components in clinical application. This chapter focuses on methods of isolating ADSCs from adipose tissue without enzymatic digestion.

Abstract P1-06-07: Msi1 in maintaining breast cancer stem cell involves the AKT/PI3K pathway

Musashi1 (Msi1) was originally described in neural stem cells in a role influencing neural differentiation in the Numb/Notch pathway. Due to its role in neural stem cells, there has been much interest in the role of Msi1 in the breast cancer (BC) stem cell population. In this vein, with we have demonstrated a possible feedback loop between the stem cell marker OCT4 and Msi1, in addition to other stem cell-associated genes. Flow cytometry analyses demonstrated that the subset of BC cells (BCCs) that we previously identified as those with high Oct4 was also enriched for Msi1. Msi1 knockdown BCCs showed decreased doubling time and with limited ability to be passaged, indicating the loss of the self-renewal subset needed for cell passaging. These in vitro findings were consistent with the inability of the Msi1 knockdown BCCs to undergo serial passages in vivo. We therefore examined the Msi1 knockdown BCCs for intracellular proteins that could explain the reduced cell growth and the reduced initiating cells. We selected the AKT/PI3K pathway due to its recent connection to the maintenance of BC stem cells. Msi1 knockdown repressed several molecules within the AKT/PI3K pathway: PTEN, AKT, and PI3K. There were no significant differences found however, in the apoptotic factors, BCL-2 and Caspase-3. Upon further investigation, we observed increases in molecules that are linked to decreased cell proliferation and senescence, p16, p53 and p21. Since Msi1 is an RNA binding protein, it is possible that its loss could leave RNAs for binding to miRNAs and this might be partly responsible for the decrease in key intracellular molecules needed for the survival and proliferation of the Msi1 knockdown BCCs. Further studies are needed to investigate how miRNAs and Msi1 interact to maintain the survival of BCCs. Finally, Msi1 KD positively affects the expression of the immune checkpoint inhibitor PD-1L, suggesting increased PD-1L expression in cells that are not of the CSC phenotype. The studies may identify Msi1 or its associated molecules as a potential therapeutic intervention for BC. Citation Format: Nahas GR, Sinha GA, Sherman LS, Walker ND, Rameshwar P. Msi1 in maintaining breast cancer stem cell involves the AKT/PI3K pathway. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-06-07.