was successfully added to your cart.

Cart

Category

Stem Cells

The Pathways of Cell Death: Oncosis, Apoptosis, and Necrosis

By | Stem Cells

The Pathways of Cell Death: Oncosis, Apoptosis, and Necrosis

Benjamin E Trump, Irene K. Berezesky, Seung H. Chang, and Patricia C. Phelps

The pathways and identification of cell injury and cell death are of key importance to the practice of diagnostic and research toxicologic pathology. Following a lethal injury, cellular reactions are initially reversible. Currently, we recognize two patterns, oncosis and apoptosis. Oncosis, derived from the Greek word “swelling,” is the common pattern of change in infarcts and in zonal killing following chemical toxicity, e.g., centrilobular hepatic necrosis after CC14 toxicity. In this common reaction, the earliest changes involve cytoplasmic blebbing, dilatation of the endoplasmic reticulum (ER), swelling of the cytosol, normal or condensed mitochondria, and chromatin clumping in the nucleus. In apoptosis, the early changes involve cell shrinkage, cytosolic shrinkage, more marked chromatin clumping, cytoplasmic blebbing, swollen ER on occasion, and mitochondria that are normal or condensed. Following cell death, both types undergo postmortem changes collectively termed “necrosis.” In the case of oncosis, this typically involves broad zones of cells while, in the case of apoptosis, the cells and/or the fragments are often phagocytized prior to their death by adjacent macrophages or parenchymal cells. In either case, the changes converge to a pattern that involves mitochondrial swelling, mitochondrial flocculent densities and/or calcification, karyolysis, and disruption of plasmalemmal continuity. The biochemical mechanisms of cell death are currently under intense study, particularly concerning the genes involved in the process. Pro-death genes include p53, the ced-3/ICE proteases, and the Bax family. Anti-death genes include ced-9/Bcl-2 and the adenovirus protein E1B. It is clear that ion deregulation, particularly that of [2 1]C+a plays an important role in cell death following either apoptosis or oncosis. Genetic evidence strongly indicates that activation of proteases is an important step, possibly very near to the point where cell death occurs.

Read the full articleRead the full article

Stem Cells and Calcium Signaling

By | Stem Cells

Stem Cells and Calcium Signaling

Fernanda M.P. Tonelli, Anderson K. Santos, Dawidson A. Gomes, Saulo L. da Silva, Katia N. Gomes, Luiz O. Ladeira, Rodrigo R. Resende

The increasing interest in stem cell research is linked to the promise of developing treatments for many lifethreatening, debilitating diseases, and for cell replacement therapies. However, performing these therapeutic innovations with safety will only be possible when an accurate knowledge about the molecular signals that promote the desired cell fate is reached. Among these signals are transient changes in intracellular Ca2+ concentration [Ca2+]i. Acting as an intracellular messenger, Ca2+ has a key role in cell signaling pathways in various differentiation stages of stem cells. The aim of this chapter is to present a broad overview of various moments in which Ca2+- mediated signaling is essential for the maintenance of stem cells and for promoting their development and differentiation, also focusing on their therapeutic potential.

Read the full articleRead the full article

Effects of Repetitive lonomycin Treatment on In Vitro Development of Bovine Somatic Cell Nuclear Transfer Embryos

By | Stem Cells

Effects of Repetitive lonomycin Treatment on In Vitro Development of Bovine Somatic Cell Nuclear Transfer Embryos

Huen Suk KIM, Jong Yun LEV, Eun Ji JEONG, Chi Jeon YANG, Sang Hwan HYUN, Taeyoung SHIN and Woo Suk HWANG

To artificially activate embryos in somatic cell nuclear transfer (SCNT), chemical treatment with ionomycin has been used to induce transient levels of Ca2+ and initiate reprogramming of embryos. Ca2+ oscillation occurs naturally several times after fertilization (several times with 15- to 30-min intervals). This indicates how essential additional Ca2+ influx is for successful reprogramming of embryos. Hence, in this report, the experimental design was aimed at improving the developmental efficiency of cloned embryos by repetitive Ca2+ transients rather than the commonly used ionomycin treatment (4 min). To determine optimal Ca2+ inflow conditions, we performed three different repetitive ionomycin (10 pM) treatments in reconstructed embryos: Group 1 (4-min ionomycin treatment, once), Group 2 (30-sec treatment, 4 times, 15-min intervals) and Group 3 (1-min treatment, 4 times, 15-min intervals). Pronuclear formation rates were checked to assess the effects of repetitive ionomycin treatment on reprogramming of cloned embryos. Cleavage rates were investigated on day 2, and the formation rates of blastocysts (BLs) were examined on day 7 to demonstrate the positive effect of repeated ionomycin treatment. In Group 3, a significant increase in BL formation was observed [47/200 (23.50%), 44/197 (22.33%) and 69/195 (35.38%) in Groups 1, 2 and 3, respectively]. Culturing embryos with different ionomycin treatments caused no significant difference among the groups in terms of the total cell number of BLs (164.3, 158.5 and 145.1, respectively). Additionally, expression of the anti-apoptotic Bc1-2 gene and MnSOD increased significantly in Group 3, whereas the expression of the pro-apoptotic Bax decreased statistically. In conclusion, the present study demonstrated that repeated ionomycin treatment is an improved activation method that can increase the developmental competence of SCNT embryos by decreasing the incidence of apoptosis.

Read the full articleRead the full article

Role of NF-kB in p53-mediated programmed cell death

By | Stem Cells

Role of NF-kB in p53-mediated programmed cell death

Kevin M. Ryan, Mary K. Ernst, Nancy R. Rice & Karen H. Vousden

The tumour suppressor p53 inhibits cell growth through activation of cell-cycle arrest and apoptosis1, and most cancers have either mutation within the p53 gene or defects in the ability to induce p53. Activation or re-introduction of p53 induces apoptosis in many tumour cells and may provide effective cancer therapy2. One of the key proteins that modulates the apoptotic response is NF-kB, a transcription factor that can protect or contribute to apoptosis3. Here we show that induction of p53 causes an activation of NF-kB that correlates with the ability of p53 to induce apoptosis. Inhibition or loss of NF-kB activity abrogated p53-induced apoptosis, indicating that NF-kB is essential in p53-mediated cell death. Activation of NF-kB by p53 was distinct from that mediated by tumour-necrosis factor-a and involved MEK1 and the activation of pp90rsk. Inhibition of MEK1 blocked activation of NF-kB by p53 and completely abrogated p53-induced cell death. We conclude that inhibition of NF-kB in tumours that retain wild-type p53 may diminish, rather than augment, a therapeutic response.

Read the full articleRead the full article

Developmental Cell

By | Stem Cells

Developmental Cell

Seongsoo Lee, Kyu-Sun Lee, Sungun Huh, Seung Hyun Hong, Kweon Yu, Bingwei Lu

intracellular Ca2+ transients. While basal mitochondrial Ca2+ (Ca2+ mito) is needed to maintain organellar physiology, Ca2+ mito overload can lead to cell death. How Ca2+ mito homeostasis is regulated is not well understood. Here we show that Miro, a known component of the mitochondrial transport machinery, regulates Drosophila neural stem cell (NSC) development through Ca2+ mito homeostasis control, independent of its role in mitochondrial transport. Miro interacts with Ca2+ transporters at the ER-mitochondria contact site (ERMCS). Its inactivation causes Ca2+ mito depletion and metabolic impairment, whereas its overexpression results in Ca2+ mito overload, mitochondrial morphology change, and apoptotic response. Both conditions impaired NSC lineage progression. Ca2+ mito homeostasis is influenced by Polo-mediated phosphorylation of a conserved residue in Miro, which positively regulates Miro localization to, and the integrity of, ERMCS. Our results elucidate a regulatory mechanism underlying Ca2+ mito homeostasis and how its dysregulation may affect NSC metabolism/development and contribute to disease.

Read the full articleRead the full article

Mechanisms of p53-dependent apoptosis

By | Stem Cells

Mechanisms of p53-dependent apoptosis

M. Schuler and D. R. Green

Cellular stresses, such as growth factor deprivation, DNA damage or oncogene expression, lead to stabilization and activation of the p53 tumour suppressor protein. Depending on the cellular context, this results in one of two different outcomes: cell cycle arrest or apoptotic cell death. Cell death induced through the p53 pathway is executed by the caspase proteinases, which, by cleaving their substrates, lead to the characteristic apoptotic phenotype. Caspase activation by p53 occurs through the release of apoptogenic factors from the mitochondria, including cytochrome c and Smac/DIABLO. Released cytochrome c allows the formation of a high-molecular weight complex, the apoptosome, which consists of the adapter protein Apaf-1 and caspase 9, which is activated following recruitment into the apoptosome. Active caspase 9 then cleaves and activates the effector caspases, such as caspases-3 and -7, which execute the death program. Released Smac/ DIABLO facilitates caspase activation through repression of the IAP caspase inhibitor proteins. The release of mitochondrial apoptogenic factors is regulated by the pro- and anti-apoptotic Bcl-2 family proteins, which either induce or prevent the permeabilization of the outer mitochondrial membrane. The mechanism by which p53 signals to the Bcl-2 family proteins is unclear. It was shown that some of the pro-apoptotic family members, such as Bax, Noxa or PUMA, are transcriptional targets of p53. In addition, transcription- independent, pro-apoptotic activities of p53 have been described. The elucidation of the p53-dependent pathway, resulting in mitochondrial outer membrane permeabilization through the pro-apoptotic Bcl-2 family proteins, is a key to unveiling the mechanism of stress-induced apoptosis.

Read the full articleRead the full article

Effects of varied ionic calcium and phosphate on the proliferation, osteogenic differentiation and mineralization of human periodontal ligament cells in vitro

By | Stem Cells

Effects of varied ionic calcium and phosphate on the proliferation, osteogenic differentiation and mineralization of human periodontal ligament cells in vitro

Ann Kristin Hansen

Hyaline cartilage is an avascular, aneural and alymphatic tissue covering the ends of long bones facilitating a frictionless movement and absorption of forces in the diarthrodial joint. The thickness of cartilage is related to the congruency of the joint, ranging from 1.2 mm in the congruent ankle joint to 2.17 mm in the incongruent knee joint of adults (1), while in adolescents knee joints the thickness range up to 4 mm (2). Cartilage consists of only 3‐4 % cells, while the bulk of the tissue is the surrounding matrix made up of collagen type II and glycosaminoglycan that provide structural architecture and captures water molecules. The tissue is spatially organised in a superficial, middle, deep and calcified zone. While most reports have named the chondrocyte as the sole cell type in cartilage, newer publications have reported progenitor cells residing in the superficial layer (3). The zonal organisation of the matrix facilitates the highly specialised mechanical properties of hyaline cartilage. The superficial zone is designed to handle the sheer forces of the moving joint with flattened chondrocytes and fibrils arranged parallel to the joint surface. The compressive forces are handled by the obliquely organised middle layer and particularly the deep layer where the cells are arranged in columns and the fibrils run perpendicular to the joint line (4). The tidemark is the basophilic line on histological sections separating the hyaline cartilage from calcified cartilage, while the cement line separates the calcified cartilage from the subchondral bone plate (5). The zonal organization is reflected in the chondrocytes exhibiting different phenotypes in the superficial, middle, deep and calcified zones

Read the full articleRead the full article

Biology of signalling receptors in human articular chondrocytes

By | Stem Cells

Biology of signalling receptors in human
articular chondrocytes

Ann Kristin Hansen

Hyaline cartilage is an avascular, aneural and alymphatic tissue covering the ends of long bones facilitating a frictionless movement and absorption of forces in the diarthrodial joint. The thickness of cartilage is related to the congruency of the joint, ranging from 1.2 mm in the congruent ankle joint to 2.17 mm in the incongruent knee joint of adults, while in adolescents knee joints the thickness range up to 4 mm. Cartilage consists of only 3‑4 % cells, while the bulk of the tissue is the surrounding matrix made up of collagen type II and glycosaminoglycan that provide structural architecture and captures water molecules. The tissue is spatially organised in a superficial, middle, deep and calcified zone. While most reports have named the chondrocyte as the sole cell type in cartilage, newer publications have reported progenitor cells residing in the superficial layer. The zonal organisation of the matrix facilitates the highly specialised mechanical properties of hyaline cartilage. The superficial zone is designed to handle the sheer forces of the moving joint with flattened chondrocytes and fibrils arranged parallel to the joint surface. The compressive forces are handled by the obliquely organised middle layer and particularly the deep layer where the cells are arranged in columns and the fibrils run perpendicular to the joint line. The tidemark is the basophilic line on histological sections separating the hyaline cartilage from calcified cartilage, while the cement line separates the calcified cartilage from the subchondral bone plate. The zonal organization is reflected in the chondrocytes exhibiting different phenotypes in the superficial, middle, deep and calcified zones.

Read the full articleRead the full article

Calcium signalling in chondrogenesis: Implications for cartilage repair

By | Stem Cells

Calcium signalling in chondrogenesis:
Implications for cartilage repair

Csaba Matta, Róza Zákány

Undifferentiated mesenchymal stem cells (MSCs) represent an important source for cell-based tissue regeneration techniques that require differentiation towards specific lineages, including chondrocytes. Chondrogenesis, the process by which committed mesenchymal cells differentiate into chondrocytes, is controlled by complex but not yet completely understood signalling mechanisms that involve many components, including intracellular signalling pathways, as well as plasma membrane receptors and ion channels. Some of these signalling components are Ca2+ sensitive. Although the Ca2+-signalling toolkit of undifferentiated MSCs and mature chondrocytes are extensively studied, the adaptation of these components during differentiation and their role in chondrogenesis is not adequately established. In this review, various aspects of Ca2+ signalling are discussed in MSCs and in mature chondrocytes including spatial and temporal aspects, as well as Ca2+ entry and elimination processes, with implications for their involvement in chondrogenesis. A better understanding of these pathways is envisaged to provide a more efficient differentiation of MSCs towards chondrocytes that may lead to the development of better cartilage tissue engineering techniques.

Read the full articleRead the full article

Purinergic signalling-evoked intracellular Ca2+ concentration changes in the regulation of chondrogenesis and skeletal muscle formation

By | Stem Cells

Purinergic signalling-evoked intracellular Ca2+ concentration changes
in the regulation of chondrogenesis and skeletal muscle formation

Csaba Matta, János Fodor, László Csernoch, Róza Zákány

It is now widely recognised that changes of the intracellular calcium concentration have deep impact on the differentiation of various non-excitable cells including the elements of the vertebrate skeleton. It has become evident that purinergic signalling is one of the most ancient cellular mechanisms that can cause such alterations in the intracellular Ca2+-homeostasis, which are precisely set either spatially or temporally. Purinergic signalling is believed to regulate intracellular Ca2+-concentration of developing cartilage and skeletal muscle cells and suggested to play roles in the modulation of various cellular functions. This idea is supported by the fact that pluripotent mesenchymal cells, chondroprogenitors or muscle precursors, as well as mature chondrocytes all are capable of releasing ectonucleotides, and express various types of purinoreceptors and ectonucleotidases. The presence of the basic components of purinergic signalling proves that cells of the chondrogenic lineage can utilise this mechanism for modulating their intracellular Ca2+ concentration independently from the surrounding skeletal muscle and bone tissues, which are well known to release ectopurines during development and mechanical stress. In this review, we summarize accumulating experimental evidence supporting the importance of purinergic signalling in the regulation of chondrogenesis and during skeletal muscle formation.

Read the full articleRead the full article