Future Directions For Endocrine Induction

It is not yet known whether any of these methods will eventually be successful with hES cells, but for clinical applications, one of the most significant steps will be the ability to generate pure populations of p cells from hES cells. Separation of p cells from heterogeneous hES cell populations by flow cytometry based on cell surface molecules is one option, but is unlikely to be feasible because hES cells need to be in clusters and do not survive well as single cells (16). Our hypothesis is...

Nestin As A Marker Of Islet Progenitor Cells

Identification of a pancreas progenitor cell would be an important step in our ability to isolate large numbers of cells that could be readily differentiated into islets or p cells. Based on expression of many neuronal cell markers, a neuroec-todermal origin of pancreatic endocrine cells has been hypothesized for many years. It was suggested that the intermediate filament protein nestin, which is expressed in neuronal precursors, might be a marker of islet progenitor cells (63). This...

Conclusion

HSCT has the potential to restore self-tolerance and prevent further destruction of islet p cells in patients with recent-onset type 1 diabetes. Autologous HSCT, however, is associated with risk of recurrent autoimmunity, and although allogeneic HSCT may cure autoimmunity to islet p cells in patients with recent-onset type 1 diabetes, the risks associated with allogeneic HSCT outweigh the known potential benefits of this therapy. Nevertheless, hematopoietic stem cell transplantation as...

Development

The mammalian pancreas is a mixed exocrine and endocrine gland that produces digestive enzymes and hormones. The enzymes are produced by cells of the exocrine portion, whereas the hormones are synthesized by cells that are clustered in the islets of Langerhans. The pancreas develops from fusion of dorsal and ventral primordia, which appear as buds from the embryonic gut. Each primordium is formed by an endodermally derived pancreatic duct containing undifferentiated precursor cells that migrate...

Introduction

Stem cells, which have a great capacity for self-renewal and can differentiate into at least one committed cell type, exist in embryonic and adult organisms of many phyla. Although stem cells of various types from mice and other lower organisms have been studied for many years, it was not until the derivation of stem cell lines from human embryos in 1998 (1,2) that the idea of stem cell-based therapies became widespread for the treatment of a range of disorders from Alzheimer's disease to type...

Mesenchymal Stem Cells

The Mesengenic Process

MSCs or marrow stromal cells, as with hematopoietic stem cells, reside in the bone marrow and are critical for repairing injured tissues. MSCs are found to a lesser extent around blood vessels (pericytes), in fat, muscle, skin, and other locations (74). These progenitor cells are not only capable of providing a rich and abundant source of transplant material, but in situ, also give rise to daughter cells with a more restricted developmental path. The lineage committed cells within MSCs can form...

Modalities

Based on our current knowledge, we propose that various therapeutic modalities could be performed using adult autologous, syngeneic, or allogeneic pluri- potent stem cells, germ layer lineage stem cells, or progenitor cells. However, use of the adult-derived pluripotent stem cells or germ layer lineage stem cells would require that they be made to undergo lineage tissue induction to form specific tissue types. We have begun to study the potential advantages for using synge-neic, allogeneic, and...

Of Liver Cells

The liver shares its origin with the pancreas and arises from the foregut endo-derm (1,2). In humans, the embryonic liver appears after 4 weeks of gestation and rapidly assumes the eventual structure of the adult organ, such that by 14 weeks of gestation, the acinar structure becomes established and bile is produced. Studies in mice indicate that the embryonic liver and pancreas develop through discrete phases, including a period in which primitive cells are first specified via the activation...

Pluripotent Stem Cells

The pluripotent stem cell forms the first category of adult precursor cells. These cells are lineage-uncommitted. They are the most undifferentiated of the precursor cells. They have extensive capabilities for self-renewal that far exceed the mitotic clock of 50-70 population doublings characteristic of differentiated cells and progenitor cells that are committed to specific tissue lineages. They are telomerase-positive, which is consistent with their extensive capabilities for self-renewal....

Progenitor Cells

A third category of adult precursor cells are the tissue-specific, lineage-committed progenitor cells. Progenitor cells have a finite life-span that begins at birth. Progenitor cells have a mitotic clock of 50-70 population doublings before programmed replicative cell senescence and cell death occurs. A second characteristic of tissue-specific progenitor cells is that they are the immediate precursor cells for adult differentiated cells. They are preprogrammed to commit to particular cell...

SSCs Male Mutation Bias And Genetic Diseases

SSCs are the foundation for the life-long production of sperm that transmit genes to the next generation. Therefore, any abnormality that occurs in the SSC genome can result in germ line mutations and cause inherited diseases in offspring. In this regard, recent clinical studies, including those of endocrine cancers, have shown that a strong sex-dependent bias exists in germ line mutations (84), which, as described in the following sections, suggests the involvement of the regulation of stem...

The Acute Injury Phase

A bone fracture incites an inflammatory response coupled with complement activation, and extravasation secondary to damage to blood vessels. Proximal to the fracture site, an acidotic state ensues with a decrease in pH (4,5). The pro-teolytic degradation of extracellular matrix produces chemotactic remnants that attract monocytes and macrophages to the wound bed (36). Activated macrophages release fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF), stimulating...

Tumorigenicity

The most pressing issue regarding the use of stem cells for cell-based therapies, particularly pluripotent embryonic stem cells, is their capacity to generate tumors after transplantation (8). Thus a characteristic of undifferentiated embryonic stem cells is their ability to give rise to teratoma formation after transplantation (9,10) this capacity must clearly be prevented if they are to be used as therapies. How does one assess the tumorigenic potential of a particular cellular therapy The...

Transdifferentiation Of Adult Stem Cells

Several adult tissues, including blood, epidermis, liver, enterocytes, and spermatogonia, are replenished throughout life by tissue-specific stem cells. Unlike pluripotent stem cells derived from germ cells or the ICM, these somatic stem cells present within organs have not been shown to be capable of differentiating into germ cells. However, somatic stem cells may be multipotent, wherein their progeny can differentiate into multiple discrete cell types, as in the case of hematopoietic stem...

Endocrine Differentiation Of mES

Induction of endocrine differentiation in rodent ES or progenitor cells has been attempted with varying results. Using mES cells, Lumelsky and colleagues have been able to induce insulin-containing cells using an experimental strategy of stepwise selection through changes in culture conditions (43). The levels of insulin may be increased by using growth inhibitors such as phosphatidylinositol 3-kinase inhibitors (44). However, a recent report questions whether the insulin is actually produced...

The Frequency Of Sscs

A common characteristic observed in virtually all stem cell systems is that stem cells are a rare cell population in a cell lineage. For example, definitive HSCs represent only 0.007 of nucleated bone marrow cells in mice (1). Using spermatogonial transplantation as a SSC bioassay, a recent study has demonstrated that adult mouse SSCs represent 0.01 of total testis cells (approximately 3000 SSCs testis, ref. 46). Thus 1 in 10,000 cells in an adult testis is a stem cell, a similar frequency to...

In Vivo Testing

After the functional capacity of cells destined for transplantation have been established with in vitro systems, cell safety and efficacy must be established in vivo. The goal for stem cell-based therapy is to match or improve on current exogenous therapeutic options. To establish this standard, stem cell-based therapies must be tested in appropriate animal models, assessing the animals' physiologic responses and evaluating cell phenotype stability. To improve on current exogenous hormonal...

Life Span

Mammalian Adult Stem Cells

Differentiated cells and lineage-committed cells have a finite life span. These tissue-specific cells have a mitotic clock of50-70 population doublings before programmed replicative cell senescence and cell death occurs. The mitotic clock for these tissue-specific cells begins at birth. From birth to approximately 20 years of age, about the time an individual attains full stature, there is an exponential increase in the mitotic clock of these cells to about 30 population doublings. From this...

Pancreatic Islet A Miniorgan

The mammalian pancreas is composed of the exocrine acini, endocrine islets, and pancreatic ducts. The exocrine pancreas makes digestive enzymes, which are released into the digestive system through pancreatic ductal system. The islets, which constitute about 1-2 of the total pancreatic cell mass, are distributed in the exocrine tissue. They produce endocrine hormones required for utilization of glucose. An islet is not merely an aggregate of cells, but rather a miniorgan containing different...

Autoimmune Type 1 Diabetes Mellitus

Of the endocrine autoimmune diseases, autoimmune type 1 diabetes mellitus (hereafter referred to as type 1 diabetes) is the most extensively studied because of both disease prevalence and severity. In 2002, approximately 13 million people in the United States (6.3 of the population) suffered from diabetes, and approximately 5-10 of these cases were diagnosed as type 1 diabetes (15). Furthermore, in the year 2000, diabetes was the sixth leading cause of death listed on death certificates in the...

Germ Layer Lineage Stem Cells

A second category of adult precursor cells consists of the germ layer lineage ectodermal, mesodermal, and endodermal stem cells. These stem cells demonstrate extensive capabilities for self-renewal, far exceeding the mitotic clock of 50-70 population doublings for differentiated cells and lineage-committed tissue-specific cells. Germ layer lineage stem cells are telomerase-positive. This characteristic is consistent with their extensive capabilities for self-renewal. They retain this capacity...

Development Of Germ Cells And Their Relations To Embryonic Stem Cells

Fetal Mesodermal Progeniter

During embryonic development, germ cells first emerge at a specific location segregated from somatic cell development in both vertebrates and invertebrates (7-9). This physical segregation of germ cells has been hypothesized to allow germ line specification to occur with a minimal influence from somatic cell development (8). In mammals, germ cell development has been best studied in mice. Mouse germ cells are first recognized at the base of allantois in the extraembryonic mesoderm at...

Allogeneic Hsct In Recentonset Autoimmune Type 1 Diabetes Mellitus

In contrast to autologous HSCT, allogeneic HSCT may cure autoimmunity, and consequently preserve remaining pancreatic islets in patients with recent-onset type 1 diabetes. The rationale for allogeneic HSCT for patients with recent-onset type 1 diabetes is based on the following observations (1) allogeneic HSCT will halt autoimmune-mediated destruction of islet p cells (2) preservation of intact islet p cells is beneficial to the patient even in the absence of full metabolic control (3) because...

Autoimmune Endocrine Diseases

The majority of autoimmune endocrine diseases are characterized by immune destruction of endocrine tissue leading to glandular dysfunction and hormonal imbalance. Endocrine autoimmune diseases include hypophysitis, Graves' disease, thyroiditis, autoimmune disease of the adrenal gland (Addison's disease), hypoparathyroidism, autoimmune type 1 diabetes mellitus, and autoimmune polyendocrine syndromes. These diseases have complex etiologies, which are unique to each disease, and, to some extent,...

Liver Directed Cell Therapy for Acute and Chronic Liver Failure

Results of hepatocytes transplantation in animal models of acute liver failure and chronic liver disease have been mixed. These animal models often pose difficulties because of variable susceptibilities of individual animals to disease and the possibility of improved outcomes unrelated to hepatocyte regeneration (89). Nonetheless, more recent studies in better defined genetic animals models have begun to demonstrate that cell therapy could have therapeutic potential in acute liver failure...

Animal Species for the Model

To answer all preclinical questions the model should manifest the human disease process under evaluation and possess immunologic characteristics similar enough to humans to allow an estimation of autoimmune and allogenic rejection. Models for many human endocrine diseases have been established in mice, including type 1 diabetes mellitus DM 64-67 , type 2 DM, thyroiditis 68 , and osteoporosis Table 2 69,70 . But nonhuman primates, who share similar immune systems to humans, do not spontaneously...

References

Shapiro AM, Lakey JR, Ryan EA, et al. Islet transplantation in seven patients with type 1 diabetes mellitus using a glucocorticoid-free immunosuppressive regimen. N Engl J Med 2000 343 230-238. 2. Kanno T, Gopel SO, Rorsman P, Wakui M. Cellular function in multicellular system for hormone-secretion electrophysiological aspect of studies on alpha-, beta- and delta-cells of the pancreatic islet. Neurosci Res 2002 42 79-90. 3. Sunami E, Kanazawa H, Hashizume H, Takeda M, Hatakeyama K, Ushiki T....