Mesenchymal cells

Muscle tissue is unique in its ability to shorten or contract. The human body has three basic types of muscle tissue histologically classified into smooth, striated, and cardiac muscle tissues. Only the striated muscle tissue is found in all skeletal muscles. The type of cells which compose the muscle tissue are known as contractile cells. They originate from mesenchymal cells which differentiate into myoblasts. Myoblasts are embryonic cells which later differentiate into contractile fiber cells. 

At about four months gestation, mesenchymal cells emanating from the central hyaloid vessel at the optic disc invade the inner layers of the retina. These endothelial complexes develop into capillaries as vascularization proceeds anteriorly in all directions towards the ora serrata from the optic nerve. As this progresses, so the embryonic hyaloid vessels in the vitreous undeigo regression. These retinal vessels do not, however, reach the most anterior portion of the retina until 8 months gestation and the anterior temporal retinal periphery, ferthest removed from the optic nerve, is not vascularized until about full term (Flower and Patz, 1971). 

Recently, the notion that the chronicity of inflammation may not actually drive the fibrogenic process has been widely appreciated (Tables 1, 2, and 3). Some propose that it is indeed the alteration of the mesenchymal cell phenotypes that disrupts the balance between collagen synthesis and degradation in the wound-healing process, highlighted by clinical evidence that shows unsuccessful treatment of fibrosis with anti-inflammatory or immunosuppressive drugs (18,19). One scenario is that mesenchymal cells (myofibroblasts and fibroblasts) are phenotypically altered and thus do not undergo apoptosis after resolution. 

The principal cells in bone are the osteoclasts and osteoblasts. Osteoclasts, the cells responsible for resorption of bone, are derived from hematopoietic stem cells. Osteoblasts are derived from local mesenchymal cells. They are the pivotal bone cell, responsible for bone formation. Skeletal tissues are remodelled throughout a lifetime, alternating resorption phases by osteoclasts with periods of intense collagen synthesis. This balance is under the control of mechanical and hormonal stimuli, which ensure the appropriate performance of the bone. Skeletal tissues have three... 

Li X et al (2005) Modulation of chondrocytic properties of fat-derived mesenchymal cells in co-cultures with nucleus pulposus. Connect Tissue Res 46(2) 75-82... 

Caldwell V, Loch-Caruso R. 1992. Chlordecone rapidly and reversibly inhibits gap junctional communication in human embryonic palatal mesenchyme cells. In Vitro Toxicol 5(2) 113-122. 

Zhao F, Mayura K, Hutchinson RW, et al. 1995. Developmental toxicity and structure-activity relationships of chlorophenols using human embryonic palatal mesenchymal cells. Toxicol Lett 78 35-42. 

Endothelial cell interaction with ECM and mesenchymal cells is a prerequisite to form a stable vasculature. Therefore, after endothehal cell proliferation and maturation, and the formation of endothehal tube structures, surrounding vessel layers composed of mural cehs... 

Galmiche MC, Koteliansky VE, Briere J, Herve P, Charbord P. Stromal cells from human long-term marrow cultures are mesenchymal cells that differentiate following a vascular smooth muscle differentiation pathway. Blood 1993 82 66-76. 

The MM test is based upon rat embryonic limb mesenchyme cells containing chondroblasts which, when cultured in small volumes at high density, form foci of chondrocytes (chondrogenesis with extracellular secretion of proteoglycans). 

The implementation of animal test protocols in the 1980s has been accompanied by the development of a host of alternative methods to study adverse effects of chemicals on reproductive and developmental parameters. For example, rat whole embryo culture stems from the seventies (16), as does the rat limb bud organ culture (17) and rat limb bud and brain micromass was developed in the eighties (18). An elegant nonvertebrate alternative model used regeneration of polyps of Hydra atUnuata from dissociated cells (19). Animal-free in vitro alternatives include those employing the proliferation of a human embryonic palatal mesenchymal cell line (20), the attachment of a mouse ovarian tumor cell line (21), and the differentiation of a neuroblastoma cell line (22) and a embryonal carcinoma cell line (23). Various overviews of methods have been published over the years (24). The predictability of... 

Fig. 13. Facial morphology. Normal embryo with facial structures highlighted nasal prominence (np, oval circle), optic placode (op, arroWi and otic placode (otp, arroWi, and mesencephalic flexure light dotted ared). The mesencephalic flexure is surrounded by a central facial region filled with mesenchymal cell populations darkrectangle aredi.

Horwitz, E. M., Gordon, P. L., Koo, W. K., et al. (2002), Isolated allogeneic bone marrow-derived mesenchymal cells engraft and stimulate growth in children with osteogenesis imperfecta Implications for cells therapy of bone, Proc. Natl. Acad. Sci. USA, 99(13), 8932-8937. 

Prior to the 3rd week, embryonic nutrition occurs by diffusion of maternal blood. At that point, development of the primitive blood and blood vessels begins in the extraembryonic mesoderm of the yolk sac. These cells differentiate into angioblasts that form cords and clusters, which in turn canalize. Cells in the peripheiy become flat and form the endothelium, whereas the inner cells give rise to the primitive blood cells. By fusion and continuous budding, the extraembryonic vessels that have contact with maternal circulation establish contact with vessels arising from the embryo proper. The mesenchymal cells surrounding the primitive endothelial cells differentiate to form the muscular and connective tissues of the vessel wall. The primitive heart... 

Pratt RM, Grove Rl, Willis WD (1982) Prescreening for environmental teratogens using cultured mesenchymal cells from the human embryonic palate. Teratog Cardnog Mutagen, 2 313-318. 

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