Article Commentary: Stem Cell Plasticity and Tissue Replacement

Dynamic scRNA-seq of live human pancreatic slices reveals functional endocrine cell neogenesis through an intermediate ducto-acinar stage

Human pancreatic plasticity is implied from multiple single-cell RNA sequencing (scRNA-seq) studies. However, these have been invariably based on static datasets from which fate trajectories can only be inferred using pseudotemporal estimations. Furthermore, the analysis of isolated islets has resulted in a drastic underrepresentation of other cell types, hindering our ability to interrogate exocrine-endocrine interactions. The long-term culture of human pancreatic slices (HPSs) has presented the field with an opportunity to dynamically track tissue plasticity at the single-cell level. Combining datasets from same-donor HPSs at different time points, with or without a known regenerative stimulus (BMP signaling), led to integrated single-cell datasets storing true temporal or treatment-dependent information. This integration revealed population shifts consistent with ductal progenitor activation, blurring of ductal/acinar boundaries, formation of ducto-acinar-endocrine differentiation axes, and detection of transitional insulin-producing cells. This study provides the first longitudinal scRNA-seq analysis of whole human pancreatic tissue, confirming its plasticity in a dynamic fashion.

Article Commentary: Stem Cell Research in Cell Transplantation: An Analysis of Geopolitical Influence by Publications

One of the fastest growing fields in researching treatments for neurodegenerative and other disorders is the use of stem cells. These cells are naturally occurring and can be obtained from three different stages of an organism's life: embryonic, fetal, and adult. In the US, political doctrine has restricted use of federal funds for stem cells, enhancing research towards an adult source. In order to determine how this legislation may be represented by the stem cell field, a retrospective analysis of stem cell articles published in the journal Cell Transplantation over a 2-year period was performed. Cell Transplantation is considered a translational journal from preclinical to clinical, so it was of interest to determine the publication outcome of stem cell articles 6 years after the US regulations. The distribution of the source of stem cells was found to be biased towards the adult stage, but relatively similar over the embryonic and fetal stages. The fetal stem cell reports were primarily neural in origin, whereas the adult stem cell ones were predominantly mesenchymal and used mainly in neural studies. The majority of stem cell studies published in Cell Transplantation were found to fall under the umbrella of neuroscience research. American scientists published the most articles using stem cells with a bias towards adult stem cells, supporting the effect of the legislation, whereas Europe was the leading continent with a bias towards embryonic and fetal stem cells, where research is “controlled” but not restricted. Japan was also a major player in the use of stem cells. Allogeneic transplants (where donor and recipient are the same species) were the most common transplants recorded, although the transplantation of human-derived stem cells into rodents was the most common specific transplantation performed. This demonstrates that the use of stem cells is an increasingly important field (with a doubling of papers between 2005 and 2006), which is likely to develop into a major therapeutic area over the next few decades and that funding restrictions can affect the type of research being performed.

Allogeneic islet transplantation

Significant progress has been made in the field of beta-cell replacement therapies by islet transplantation in patients with unstable Type 1 diabetes mellitus (T1DM). Recent clinical trials have shown that islet transplantation can reproducibly lead to insulin independence when adequate islet numbers are implanted. Benefits include improvement of glycemic control, prevention of severe hypoglycemia and amelioration of quality of life. Numerous challenges still limit this therapeutic option from becoming the treatment of choice for T1DM. The limitations are primarily associated with the low islet yield of human pancreas isolations and the need for chronic immunosuppressive therapies. Herein the authors present an overview of the historical progress of islet transplantation and outline the recent advances of the field. Cellular therapies offer the potential for a cure for patients with T1DM. The progress in beta-cell replacement treatment by islet transplantation as well as those of emerging immune interventions for the restoration of self tolerance justify great optimism for years to come.

Stem Cells in Cell Transplantation

This commentary documents the increased number of stem cell-related research reports recently published in the cell transplantation field in the journal Cell Transplantation. The journal covers a wide range of issues in cell-based therapy and regenerative medicine and is attracting clinical and preclinical articles from around the world. It thereby complements and extends the basic coverage of stem cell physiology reported in Stem Cells and Development. Sections in Cell Transplantation cover neuroscience, diabetes, hepatocytes, bone, muscle, cartilage, skin, vessels, and other tissues, as well as tissue engineering that employs novel methods with stem cells. Clearly, the continued use of biomedical engineering will depend heavily on stem cells, and these two journals are well positioned to provide comprehensive coverage of these developments.

Endothelial progenitor cells: from bench to bedside

Strong evidence suggests that bone marrow-derived cells play a role in physiological and pathological blood vessel growth in the adult, both by augmenting angiogenesis through the secretion of angiogenic growth factors and by providing a rich source of progenitor cells that can differentiate into mature vascular endothelial cells. This is a true paradigm shift, since adult neovascularization processes were thought to be limited to angiogenesis. The cells that are critical to postnatal blood vessel growth – endothelial progenitor cells – may be analogous to the embryonic angioblast, in that they can circulate, proliferate and participate in the development of vascular networks by differentiating in situ, probably via the formation of cell clusters into mature endothelial cells. Therefore, initial reports have seen analogs to the process of vasculogenesis in the embryo, where the de novo synthesis of vessels occurs through the formation of blood island-like clusters, which subsequently connect and eventually form systemic vasculature. Recent work implicates precursors of endothelial cells in such processes as myocardial ischemia and infarction, limb ischemia, wound healing, atherosclerosis, endogenous endothelial repair and tumor vascularization. These new insights into the vascular biology of endothelial regeneration and repair led to the development of new cell therapeutic strategies to enhance adult neovascularization and re-endothelialization in ischemic cardiovascular diseases.