Cells Tissues Organs

Bone marrow-derived mesenchymal stem cells (MSCs) have the potential to differentiate along different mesenchymal lineages including those forming bone, cartilage, tendon, fat, muscle and marrow stroma that supports hematopoiesis. This differentiation potential makes MSCs candidates for cell-based therapeutic strategies for mesenchymal tissue injuries and for hematopoietic disorders by both local and systemic application. In the present study, rat marrow-derived MSCs were ex vivo culture-expanded, labeled with ¹¹¹In-oxine, and infused into syngeneic rats via intra-artery (i.a.), intravenous (i.v.) and intraperitoneal cavity (i.p.) infusions. In addition, for i.a. and i.v. infusions, a vasodilator, sodium nitroprusside, was administered prior to the cell infusion and examined for its effect on MSC circulation. The dynamic distribution of infused MSCs was monitored by real-time imaging using a gamma camera immediately after infusion and at 48 h postinfusion. After 48 h, radioactivity in excised organs, including liver, lungs, kidneys, spleen and long bones, was measured in a gamma well counter and expressed as a percentage of injected doses. After both i.a. and i.v. infusion, radioactivity associated with MSCs was detected primarily in the lungs and then secondarily in the liver and other organs. When sodium nitroprusside was used, more labeled MSCs cleared the lungs resulting in a larger proportion detected in the liver. Most importantly, the homing of labeled MSCs to the marrow of long bones was significantly increased by the pretreatment with vasodilator. These results indicate multiple homing sites for injected MSCs and that the distribution of MSCs can be influenced by administration of vasodilator.

Breast cancer is a highly prevalent disease among women worldwide. While the expression of certain proteins within these tumours is used for prognosis and selection of therapies, there is a continuing need for additional markers to be identified. A considerable amount of current literature, based predominantly on cell culture systems, suggests that a major mechanism responsible for the progression of breast cancer is due to tumour cells losing their epithelial features and gaining mesenchymal properties. These events are proposed to be very similar to the epithelial-mesenchymal transition (EMT) process that has been well characterised in embryonic development. For the developmental and putative cancer EMT, the cell intermediate filament status changes from a keratin-rich network which connects to adherens junctions and hemidesmosomes, to a vimentin-rich network connecting to focal adhesions. This review summarises observations of vimentin expression in breast cancer model systems, and discusses the potential role of EMT in human breast cancer progression, and the prognostic usefulness of vimentin expression.

Questions on the embryonic origin and developmental significance of the epicardium did not receive much recognition for more than a century. It was generally thought that the epicardium was derived from the outermost layer of the primitive myocardium of the early embryonic heart tube. During the past few years, however, there has been an increasing interest in the development of the epicardium. This was caused by a series of new embryological data. The first data showed that the epicardium did not derive from the primitive myocardium but from a primarily extracardiac primordium, called the proepicardial serosa. Subsequent data then suggested that the proepicardial serosa and the newly formed epicardium provided nearly all cellular elements of the subepicardial and intermyocardial connective tissue, and of the coronary vasculature. Recent data even suggest important modulatory roles of the epicardium and of other proepicardium-derived cells in the differentiation of the embryonic myocardium and cardiac conduction system. The present paper reviews our current knowledge on the origin and embryonic development of the epicardium.

Tumor necrosis factor-alpha (TNF-α) is known to mediate bone resorption; however, its role in osteogenesis has not been fully elucidated. In order to investigate the direct role of TNF-α signaling in the recruitment and differentiation of osteoblasts, two separate models of bone repair were used, marrow ablation and simple transverse fractures. These models were carried out in the tibiae of both wild-type and knock-out mice in which both TNF-α receptors (p55^–/–/p75^–/–) had been ablated. Marrow ablation is a unique model in which robust intramembranous bone formation is induced without an endochondral component, followed by remodeling and restoration of the original trabecular architecture of the bone marrow. In contrast, fracture repair proceeds concurrently through both endochondral and intramembranous processes of new bone tissue formation. In both models of bone repair, healing was delayed in the TNF-α receptor (p55^–/–/p75^–/–) deficient mice. In the marrow ablation model, young osteoblasts were recruited into the marrow space by day three in the wild-type mice, while the TNF-α (p55^–/–/p75^–/–) mice had only granulation tissue in the marrow cavity. Type I collagen and osteocalcin mRNA expressions were reduced ∼30 and ∼50%, respectively, of the control values in the TNF-α receptor ablated mice. In the fracture repair model there was almost a complete absence of the initial intramembranous bone formation on the periosteal surface in the TNF-α (p55^–/–/p75^–/–) mice. As healing progressed however, the callus tissues were greatly enlarged, and there was a delay in hypertrophy of the chondrocytes and the resorption of cartilage tissue. While during the initial period of fracture repair there was a marked reduction in the expression of both type I collagen and osteocalcin mRNAs in the TNF-α (p55^–/–/p75^–/–) mice, levels of these mRNAs were elevated by ∼10–20% over the wild type at the later time points in the absence of endochondral resorption of the callus. The lack of inhibition of osteogenesis during endochondral resorption suggests that a different set of signals are involved in the recruitment of osteogenic cells during endochondral repair then during intramembranous bone formation. Co-culture of chondrocytes with a mesenchymal stem cell line was carried out to examine if chondrocytes themselves produced paracrine factors that promote osteogenic differentiation. These experiments demonstrated that chondrocytes do indeed produce factors that promoted osteogenic differentiation. In summary, the results presented here suggest that TNF-α plays a crucial role in promoting postnatal bone repair through the induction of osteoprogenitor cell recruitment or osteogenic cell activation in the context of intramembranous bone formation. These results further suggest that the signals that promote osteogenesis during endochondral bone formation are different from those involved in intramembranous bone formation.

<i>Background/Aims:</i> Autologous chondrocyte (CC) transplantation has the disadvantages of requiring two surgical interventions and in vitro expansion of cells, implying the risk of cellular dedifferentiation. Our clinical aim is to develop a one-step procedure for autologous CC transplantation, i.e. harvesting, isolation and reimplantation of CC performed in one single surgical procedure. Platelet-rich plasma (PRP) is a source of autologous growth factors reported to have mitogenic effects. The objective of this study was to test the influence of PRP as an autologous scaffold on freshly isolated CC and mesenchymal stem cells (MSC). <i>Methods:</i> CC and MSC were subjected to two- or three-dimensional (3D) growth systems, either with or without PRP. Chondrogenic differentiation was determined via quantification of collagen type II mRNA and immunohistochemical staining. <i>Results:</i> We observed a proliferative effect for MSCs exposed to PRP in monolayer culture and an increase in the expression of chondrogenic markers when cells are exposed to a 3D environment. CCs exposed to PRP show a decrease in the chondrogenic phenotype with increasing proliferative activity. <i>Conclusion:</i> PRP has a proliferative effect on CCs and MSCs. In a one-step procedure for autologous CC transplantation, this might be an advantage over other scaffold materials, but confirmation in in vivo studies is required.

A correspondence between the appearance of vaginal smears and the layers of the epithelium from which the cells had desquamated was established in untreated rats during the estrous cycle, in control ovariectomized rats and in spayed rats injected with either estrogen or progesterone. The technique for preparing and staining the smears (modified Shorr’s staining procedure) is outlined. A simplified.system of classification which allows the accurate identification of the various stages of the reproductive state in the rat is described. Standing estrus, as well as the influence of estrogen on spayed rats, is characterized by marked cornification of the cells and the disappearance of leukocytes. At the end of estrus, the cornified layer is sloughed off and invasion by leukocytes occurs. During diestrus, as well as in untreated ovariectomized rats, the vaginal contents consistently lack cornified cells whereas leukocytes are very plentiful. Proestrus follows diestrus: the vaginal smear is devoid of leukocytes and characterized by nucleated epithelial cells. Pregnancy, as well as the influence of progesterone on ovariectomized rats, is also characterized by epithelial growth and desquamation but at different rates, resulting in the presence of intermediate cells, and polymorphs and mucus forming a noticeable background to the smear. Since vaginal smears display cell pictures characteristic for each hormone after administration of estrogen or progesterone, exfoliate cytology is a good indicator of the stage of the reproductive state in the rat.

Osteoarthritis (OA) is a debilitating, progressive disease of diarthrodial joints associated with aging. At the molecular level, OA is characterized by an imbalance between anabolic (i.e. extracellular matrix biosynthesis) and catabolic (i.e. extracellular matrix degradation) pathways in which articular cartilage is the principal site of tissue injury responses. The pathophysiology of OA also involves the synovium in that ‘nonclassical’ inflammatory synovial processes contribute to OA progression. Chondrocytes are critical to the OA process in that the progression of OA can be judged by the vitality of chondrocytes and their ability to resist apoptosis. Growth factors exemplified by insulin-like growth factor-1, its binding proteins and transforming growth factor-β contribute to anabolic pathways including compensatory biosynthesis of extracellular matrix proteins. Catabolic pathways are altered by cytokine genes such as interleukin-1 (IL-1) and tumor necrosis factor-α (TNF-α) which are upregulated in OA. In addition, IL-1 and TNF-α downregulate extracellular matrix protein biosynthesis while concomitantly upregulating matrix metalloproteinase (MMP) gene expression. When MMPs are activated, cartilage extracellular matrix degradation ensues apparently because levels of endogenous cartilage MMP inhibitors cannot regulate MMP activity. Therapeutic strategies designed to modulate the imbalance between anabolic and catabolic pathways in OA may include neutralizing cytokine activity or MMP gene expression or inhibiting signaling pathways which result in apoptosis dependent on mature caspase activity or mitogen-activated protein kinase (MAPK) activity. MAPK activity appears critical for regulating chondrocyte and synoviocyte apoptosis and MMP genes.

During late follicular development and estrus, the mammalian oviduct undergoes specific physiological and biochemical modifications which contribute to an optimization of the microenvironment for fertilization and early cleavage-stage embryonic development. These changes appear to be hormonally regulated by ovarian steroids, most importantly, estrogen. The hundreds of macromolecules found within the oviductal lumen are contributed by selective serum transudation and active biosynthesis and secretion from nonciliated epithelial cells. Recent studies have indicated temporal and regional (infundibulum, ampulla and isthmus) differences in steady-state levels of specific mRNAs and in de novo protein synthesis and secretion by the oviduct. One protein synthesized de novo, the estrogen-dependent oviductal secretory glycoprotein (OSP), has been shown to be unique to the oviduct and is conserved across a number of mammalian species. This protein associates with the zona pellucida, perivitelline space and vitelline or blastomere membrane of ovulated eggs and preimplantation embryos. OSPs have been shown to enhance sperm binding and penetration in oocytes and may regulate development in early preimplantation embryos. Other regulatory molecules, protease inhibitors, growth factors, cytokines, binding proteins, enzymes and immunoglobulins have been identified in the oviductal microenvironment. The identification and potential roles for oviduct-secreted proteins will be reviewed and discussed. Current research focuses on continued identification and characterization of specific oviductal proteins and a determination of the molecular basis of their interactions with the oocyte, sperm or embryo.