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Mesenchymal stem cells (MSCs) also known as mesenchymal stromal cells or medicinal signaling cells are
multipotent Pluripotency: These are the cells that can generate into any of the three Germ layers which imply Endodermal, Mesodermal, and Ectodermal cells except tissues like the placenta. According to Latin terms, Pluripotentia means the ability for many thin ...
stromal cell Stromal cells, or mesenchymal stromal cells, are differentiating cells found in abundance within bone marrow but can also be seen all around the body. Stromal cells can become connective tissue cells of any organ, for example in the uterine mucosa ...
s that can differentiate into a variety of cell types, including
osteoblast Osteoblasts (from the Greek language, Greek combining forms for "bone", ὀστέο-, ''osteo-'' and βλαστάνω, ''blastanō'' "germinate") are cell (biology), cells with a single Cell nucleus, nucleus that synthesize bone. However, in the p ...
s (bone cells),
chondrocyte Chondrocytes (, from Greek χόνδρος, ''chondros'' = cartilage + κύτος, ''kytos'' = cell) are the only cells found in healthy cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and prote ...
s (cartilage cells), myocytes (muscle cells) and
adipocyte Adipocytes, also known as lipocytes and fat cells, are the cells that primarily compose adipose tissue, specialized in storing energy as fat. Adipocytes are derived from mesenchymal stem cells which give rise to adipocytes through adipogenesis. I ...
s (fat cells which give rise to marrow adipose tissue).


Structure


Definition

While the terms ''mesenchymal stem cell'' (MSC) and ''marrow stromal cell'' have been used interchangeably for many years, neither term is sufficiently descriptive: *
Mesenchyme Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood or bone. The interactions between mesenchyme and epithelium help to form nearly every ...
is
embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
nic
connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...
that is derived from the
mesoderm The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical Emb ...
and that differentiates into
hematopoietic Haematopoiesis (, from Greek , 'blood' and 'to make'; also hematopoiesis in American English; sometimes also h(a)emopoiesis) is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cell ...
and connective tissue, whereas MSCs do not differentiate into hematopoietic cells. *
Stromal cells Stromal cells, or mesenchymal stromal cells, are differentiating cells found in abundance within bone marrow but can also be seen all around the body. Stromal cells can become connective tissue cells of any organ, for example in the uterine mucos ...
are connective tissue cells that form the supportive structure in which the functional cells of the tissue reside. While this is an accurate description for one function of MSCs, the term fails to convey the relatively recently discovered roles of MSCs in the repair of tissue. * The term encompasses multipotent cells derived from other non- marrow tissues, such as
placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mate ...
,
umbilical cord In placental mammals, the umbilical cord (also called the navel string, birth cord or ''funiculus umbilicalis'') is a conduit between the developing embryo or fetus and the placenta. During prenatal development, the umbilical cord is physiologi ...
blood,
adipose tissue Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular ...
, adult
muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of mus ...
,
corneal stroma The stroma of the cornea (or substantia propria) is a fibrous, tough, unyielding, perfectly transparent and the thickest layer of the cornea of the eye. It is between Bowman's membrane anteriorly, and Descemet's membrane posteriorly. At its centr ...
or the dental pulp of
deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, ...
(baby) teeth. The cells do not have the capacity to reconstitute an entire organ.


Morphology

Mesenchymal stem cells are characterized morphologically by a small
cell body The soma (pl. ''somata'' or ''somas''), perikaryon (pl. ''perikarya''), neurocyton, or cell body is the bulbous, non-process portion of a neuron or other brain cell type, containing the cell nucleus. The word 'soma' comes from the Greek '' σῶμ ...
with a few cell processes that are long and thin. The cell body contains a large, round
nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: * Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucl ...
with a prominent
nucleolus The nucleolus (, plural: nucleoli ) is the largest structure in the nucleus of eukaryotic cells. It is best known as the site of ribosome biogenesis, which is the synthesis of ribosomes. The nucleolus also participates in the formation of sign ...
, which is surrounded by finely dispersed
chromatin Chromatin is a complex of DNA and protein found in eukaryote, eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important ...
particles, giving the nucleus a clear appearance. The remainder of the cell body contains a small amount of
Golgi apparatus The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles i ...
,
rough endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...
,
mitochondria A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...
and polyribosomes. The cells, which are long and thin, are widely dispersed and the adjacent
extracellular matrix In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide s ...
is populated by a few
reticular In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...
fibrils but is devoid of the other types of
collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whol ...
fibrils. These distinctive morphological features of mesenchymal stem cells can be visualized label-free using live cell imaging.


Location


Bone marrow

Bone marrow was the original source of MSCs, and still is the most frequently utilized. These bone marrow stem cells do not contribute to the formation of blood cells and so do not express the
hematopoietic stem cell Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the very first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within ...
marker CD34. They are sometimes referred to as ''bone marrow stromal stem cells''.


Cord cells

The youngest and most primitive MSCs may be obtained from umbilical cord tissue, namely Wharton's jelly and the umbilical
cord blood Cord blood (umbilical cord blood) is blood that remains in the placenta and in the attached umbilical cord after childbirth. Cord blood is collected because it contains stem cells, which can be used to treat hematopoietic and genetic disorders s ...
. However MSCs are found in much higher concentration in the Wharton's jelly compared to cord blood, which is a rich source of
hematopoietic stem cell Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the very first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within ...
s. The umbilical cord is available after a birth. It is normally discarded and poses no risk for collection. These MSCs may prove to be a useful source of MSCs for clinical applications due to their primitive properties and fast growth rate. and these have several advantages over bone marrow-derived MSCs. Adipose tissue-derived MSCs (AdMSCs), in addition to being easier and safer to isolate than bone marrow-derived MSCs, can be obtained in larger quantities.


Molar cells

The developing tooth bud of the mandibular third molar is a rich source of MSCs. While they are described as multipotent, it is possible that they are pluripotent. They eventually form enamel, dentin, blood vessels, dental pulp and nervous tissues. These stem cells are capable of differentiating into
chondrocyte Chondrocytes (, from Greek χόνδρος, ''chondros'' = cartilage + κύτος, ''kytos'' = cell) are the only cells found in healthy cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and prote ...
s,
cardiomyocyte Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle ...
s,
melanocyte Melanocytes are melanin-producing neural crest-derived cells located in the bottom layer (the stratum basale) of the skin's epidermis, the middle layer of the eye (the uvea), the inner ear, vaginal epithelium, meninges, bones, and hear ...
s, and
hepatocyte A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 80% of the liver's mass. These cells are involved in: * Protein synthesis * Protein storage * Transformation of carbohydrates * Synthesis of cholesterol, ...
‐like cells ''in vitro''.


Amniotic fluid

Stem cells are present in
amniotic fluid The amniotic fluid is the protective liquid contained by the amniotic sac of a gravid amniote. This fluid serves as a cushion for the growing fetus, but also serves to facilitate the exchange of nutrients, water, and biochemical products between ...
. As many as 1 in 100 cells collected during
amniocentesis Amniocentesis is a medical procedure used primarily in the prenatal diagnosis of genetic conditions. It has other uses such as in the assessment of infection and fetal lung maturity. Prenatal diagnostic testing, which includes amniocentesis, is n ...
are pluripotent mesenchymal stem cells.


Function


Differentiation capacity

MSCs have a great capacity for self-renewal while maintaining their multipotency. Recent work suggests that β-catenin, via regulation of EZH2, is a central molecule in maintaining the "stemness" of MSC's. The standard test to confirm multipotency is differentiation of the cells into osteoblasts, adipocytes and chondrocytes as well as myocytes. MSCs have been seen to even differentiate into neuron-like cells, but doubt remains about whether the MSC-derived neurons are functional. The degree to which the culture will differentiate varies among individuals and how differentiation is induced, e.g., chemical vs. mechanical; and it is not clear whether this variation is due to a different amount of "true" progenitor cells in the culture or variable differentiation capacities of individuals' progenitors. The capacity of cells to proliferate and differentiate is known to decrease with the age of the donor, as well as the time in culture. Likewise, whether this is due to a decrease in the number of MSCs or a change to the existing MSCs is not known.


Immunomodulatory effects

MSCs have an effect on innate and specific immune cells, and research has shown an ability to suppress tumor growth. MSCs produce many immunomodulatory molecules including
prostaglandin E2 Prostaglandin E2 (PGE2), also known as dinoprostone, is a naturally occurring prostaglandin with oxytocic properties that is used as a medication. Dinoprostone is used in labor induction, bleeding after delivery, termination of pregnancy, and ...
(PGE2),
nitric oxide Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its ...
, indoleamine 2,3-dioxygenase (IDO),
interleukin 6 Interleukin 6 (IL-6) is an interleukin that acts as both a pro-inflammatory cytokine and an anti-inflammatory myokine. In humans, it is encoded by the ''IL6'' gene. In addition, osteoblasts secrete IL-6 to stimulate osteoclast formation. Smooth ...
(IL-6), and other surface markers such as
FasL Fas ligand (FasL or CD95L or CD178) is a type-II transmembrane protein that belongs to the tumor necrosis factor (TNF) family. Its binding with its receptor induces apoptosis. Fas ligand/receptor interactions play an important role in the regula ...
, PD-L1 and PD-L2. MSCs have an effect on macrophages, neutrophils, NK cells, mast cells and dendritic cells in innate immunity. MSCs are able to migrate to the site of injury, where they polarize through PGE2 macrophages in M2 phenotype which is characterized by an anti-inflammatory effect. Further, PGE2 inhibits the ability of mast cells to degranulate and produce TNF-α. Proliferation and cytotoxic activity of NK cells is inhibited by PGE2 and IDO. MSCs also reduce the expression of NK cell receptors - NKG2D, NKp44 and NKp30. MSCs inhibit respiratory flare and apoptosis of neutrophils by production of cytokines IL-6 and IL-8. Differentiation and expression of dendritic cell surface markers is inhibited by IL-6 and PGE2 of MSCs. The immunosuppressive effects of MSC also depend on IL-10, but it is not certain whether they produce it alone, or only stimulate other cells to produce it. MSC expresses the adhesion molecules VCAM-1 and ICAM-1, which allow T-lymphocytes to adhere to their surface. Then MSC can affect them by molecules which have a short half-life and their effect is in the immediate vicinity of the cell. These include nitric oxide, PGE2, HGF, and activation of receptor PD-1. MSCs reduce T cell proliferation between G0 and G1 cell cycle phases and decrease the expression of IFNγ of Th1 cells while increasing the expression of IL-4 of Th2 cells. MSCs also inhibit the proliferation of B-lymphocytes between G0 and G1 cell cycle phases.


Antimicrobial properties

MSCs produce several
antimicrobial peptides Antimicrobial peptides (AMPs), also called host defence peptides (HDPs) are part of the innate immune response found among all classes of life. Fundamental differences exist between prokaryotic and eukaryotic cells that may represent targets for ...
(AMPs) including human cathelicidin LL-37, β-defensins, lipocalin 2 and
hepcidin Hepcidin is a protein that in humans is encoded by the ''HAMP'' gene. Hepcidin is a key regulator of the entry of iron into the circulation in mammals. During conditions in which the hepcidin level is abnormally high, such as inflammation, s ...
. These peptides, together with the enzyme indoleamine 2,3-dioxygenase (IDO), are responsible for the broad-spectrum antibacterial activity of MSCs.


Clinical significance

Mesenchymal stem cells can be activated and
mobilized Mobilization is the act of assembling and readying military troops and supplies for war. The word ''mobilization'' was first used in a military context in the 1850s to describe the preparation of the Prussian Army. Mobilization theories and t ...
if needed but their efficiency, in the case of muscle repair for example, is currently quite low. Further studies into the mechanisms of MSC action may provide avenues for increasing their capacity for tissue repair.


Autoimmune disease

Clinical studies investigating the efficacy of mesenchymal stem cells in treating diseases are in preliminary development, particularly for understanding
autoimmune disease An autoimmune disease is a condition arising from an abnormal immune response to a functioning body part. At least 80 types of autoimmune diseases have been identified, with some evidence suggesting that there may be more than 100 types. Nearly a ...
s, graft versus host disease,
Crohn's disease Crohn's disease is a type of inflammatory bowel disease (IBD) that may affect any segment of the gastrointestinal tract. Symptoms often include abdominal pain, diarrhea (which may be bloody if inflammation is severe), fever, abdominal distensi ...
,
multiple sclerosis Multiple (cerebral) sclerosis (MS), also known as encephalomyelitis disseminata or disseminated sclerosis, is the most common demyelinating disease, in which the insulating covers of nerve cells in the brain and spinal cord are damaged. This ...
,
systemic lupus erythematosus Lupus, technically known as systemic lupus erythematosus (SLE), is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. Symptoms vary among people and may be mild to severe. Commo ...
and systemic sclerosis. As of 2014, no high-quality clinical research provides evidence of efficacy, and numerous inconsistencies and problems exist in the research methods.


Other diseases

Many of the early clinical successes using intravenous transplantation came in systemic diseases such as graft versus host disease and
sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...
. Direct injection or placement of cells into a site in need of repair may be the preferred method of treatment, as vascular delivery suffers from a "pulmonary
first pass effect The first pass effect (also known as first-pass metabolism or presystemic metabolism) is a phenomenon of drug metabolism whereby the concentration of a drug, specifically when administered orally, is greatly reduced before it reaches the system ...
" where intravenous injected cells are sequestered in the lungs.


Detection

The International Society for Cellular Therapy (ISCT) has proposed a set of standards to define MSCs. A cell can be classified as an MSC if it shows plastic adherent properties under normal culture conditions and has a fibroblast-like morphology. In fact, some argue that MSCs and fibroblasts are functionally identical. Furthermore, MSCs can undergo osteogenic, adipogenic and chondrogenic differentiation ''ex vivo''. The cultured MSCs also express on their surface
CD73 5′-nucleotidase (5′-NT), also known as ecto-5′-nucleotidase or CD73 (cluster of differentiation 73), is an enzyme that in humans is encoded by the ''NT5E'' gene. CD73 commonly serves to convert AMP to adenosine. Transcription factor bindi ...
,
CD90 Thy-1 or CD90 (Cluster of Differentiation 90) is a 25–37 k Da heavily N-glycosylated, glycophosphatidylinositol (GPI) anchored conserved cell surface protein with a single V-like immunoglobulin domain, originally discovered as a thymocyte anti ...
and CD105, while lacking the expression of CD11b,
CD14 CD14 (cluster of differentiation 14) is a human protein made mostly by macrophages as part of the innate immune system. It helps to detect bacteria in the body by binding lipopolysaccharide (LPS), a pathogen-associated molecular pattern (PAMP). ...
,
CD19 B-lymphocyte antigen CD19, also known as CD19 molecule ( Cluster of Differentiation 19), B-Lymphocyte Surface Antigen B4, T-Cell Surface Antigen Leu-12 and CVID3 is a transmembrane protein that in humans is encoded by the gene ''CD19''. In humans, ...
, CD34, CD45,
CD79a Cluster of differentiation CD79A also known as B-cell antigen receptor complex-associated protein alpha chain and MB-1 membrane glycoprotein, is a protein that in humans is encoded by the CD79A gene. The CD79a protein together with the related C ...
and
HLA-DR HLA-DR is an MHC class II cell surface receptor encoded by the human leukocyte antigen complex on chromosome 6 region 6p21.31. The complex of HLA-DR (Human Leukocyte Antigen – DR isotype) and peptide, generally between 9 and 30 amino acids in ...
surface markers.


Research

The majority of modern culture techniques still take a colony-forming unit-fibroblasts (CFU-F) approach, where raw unpurified bone marrow or ficoll-purified bone marrow
mononuclear cell In immunology, agranulocytes (also known as nongranulocytes or mononuclear leukocytes) are one of the two types of leukocytes (white blood cells), the other type being granulocytes. Agranular cells are noted by the absence of granules in thei ...
s are plated directly into
cell culture Cell culture or tissue culture is the process by which cells are grown under controlled conditions, generally outside of their natural environment. The term "tissue culture" was coined by American pathologist Montrose Thomas Burrows. This tec ...
plates or flasks. Mesenchymal stem cells, but not red blood cells or haematopoetic progenitors, are adherent to tissue culture plastic within 24 to 48 hours. However, at least one publication has identified a population of non-adherent MSCs that are not obtained by the direct-plating technique. Other
flow cytometry Flow cytometry (FC) is a technique used to detect and measure physical and chemical characteristics of a population of cells or particles. In this process, a sample containing cells or particles is suspended in a fluid and injected into the flow ...
-based methods allow the sorting of bone marrow cells for specific surface markers, such as
STRO-1 STRO-1 (Stro-1 in mouse, rat, etc.) is a gene for a protein marker of mesenchymal stem cells (MSC). Molecular mass of Stro-1 is 75kD. The name STRO-1 is firstly proposed in the 1990s' as the name of an anti-CD34+-mesenchymal-stem-cell monoclonal an ...
. STRO-1+ cells are generally more homogenous and have higher rates of adherence and higher rates of proliferation, but the exact differences between STRO-1+ cells and MSCs are not clear. Methods of immunodepletion using such techniques as MACS have also been used in the negative selection of MSCs. The supplementation of basal media with fetal bovine serum or human platelet lysate is common in MSC culture. Prior to the use of platelet lysates for MSC culture, the pathogen inactivation process is recommended to prevent pathogen transmission. New research titled Transplantation of human ESC-derived mesenchymal stem cell spheroids ameliorates spontaneous osteoarthritis in rhesus macaques Various chemicals and methods including low level laser irradiation have been used to increase proliferation of stem cell.


History

In 1924, Russian-born morphologist Alexander A. Maximov (russian: Александр Александрович Максимов); used extensive histological findings to identify a singular type of precursor cell within
mesenchyme Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood or bone. The interactions between mesenchyme and epithelium help to form nearly every ...
that develops into different types of blood cells. Scientists Ernest A. McCulloch and James E. Till first revealed the clonal nature of marrow cells in the 1960s. An '' ex vivo'' assay for examining the clonogenic potential of multipotent marrow cells was later reported in the 1970s by Friedenstein and colleagues. In this assay system, stromal cells were referred to as colony-forming unit-fibroblasts (CFU-f). The first clinical trials of MSCs were completed in 1995 when a group of 15 patients were injected with cultured MSCs to test the safety of the treatment. Since then, more than 200 clinical trials have been started. However, most are still in the safety stage of testing. Subsequent experimentation revealed the plasticity of marrow cells and how their fate is determined by environmental cues. Culturing marrow stromal cells in the presence of osteogenic stimuli such as
ascorbic acid Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits and vegetables, also sold as a dietary supplement and as a topical 'serum' ingredient to treat melasma (dark pigment spots) ...
,
inorganic phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosph ...
and
dexamethasone Dexamethasone is a glucocorticoid medication used to treat rheumatic problems, a number of skin diseases, severe allergies, asthma, chronic obstructive lung disease, croup, brain swelling, eye pain following eye surgery, superior vena ...
could promote their differentiation into
osteoblast Osteoblasts (from the Greek language, Greek combining forms for "bone", ὀστέο-, ''osteo-'' and βλαστάνω, ''blastanō'' "germinate") are cell (biology), cells with a single Cell nucleus, nucleus that synthesize bone. However, in the p ...
s. In contrast, the addition of
transforming growth factor-beta Transforming growth factor beta (TGF-β) is a multifunctional cytokine belonging to the transforming growth factor superfamily that includes three different mammalian isoforms (TGF-β 1 to 3, HGNC symbols TGFB1, TGFB2, TGFB3) and many other sig ...
(TGF-b) could induce chondrogenic markers.


Controversies

More recently, there has been some debate over the use of the term "mesenchymal stem cells" and what constitutes the most scientifically correct meaning for the MSC acronym. Most mesenchymal cell or "MSC" preps only contain a minority fraction of true multipotent stem cells, while most cells are instead stromal in nature. One of the pioneers in the MSC field, Dr. Arnold Caplan, has proposed re-naming MSCs to mean "medicinal signaling cells." Within the stem cell field MSC has most commonly now come to refer to "mesenchymal stromal/stem cells" because of the heterogeneous nature of the cellular preparations. There is also growing concern about the marketing and injection of MSCs and mesenchymal stem cells into patients by for-profit clinics that lack rigorous data to back up these clinical uses.


See also

*
Bone marrow Bone marrow is a semi-solid biological tissue, tissue found within the Spongy bone, spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It i ...
*
Fibroblast A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework ( stroma) for animal tissues, and plays a critical role in wound healing. Fibroblasts are the most common cells ...
*
Intramembranous ossification Intramembranous ossification is one of the two essential processes during fetal development of the gnathostome (excluding chondrichthyans such as sharks) skeletal system by which rudimentary bone tissue is created. Intramembranous ossification i ...
*
Mesenchyme Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood or bone. The interactions between mesenchyme and epithelium help to form nearly every ...
* Multipotency * Cord lining * Marrow Adipose Tissue (MAT) *
List of human cell types derived from the germ layers This is a list of cells in humans derived from the three embryonic germ layers – ectoderm, mesoderm, and endoderm. Cells derived from ectoderm Surface ectoderm Skin * Trichocyte * Keratinocyte Anterior pituitary * Gonadotrope * Corti ...


References


Further reading

*


External links

* scientist-reviewed and not too technical * {{Authority control Stem cells