Mesenchymal cell
Mesenchymocytus
Also known as: mesenchyme, mesenchymal stem cell, mesenchymal stromal cell, MSC, ectomesenchyme
An unspecialised, stellate embryonic connective-tissue cell (and its adult descendant, the mesenchymal stem/stromal cell) that gives rise to fibroblasts, chondroblasts, osteoblasts, adipocytes and smooth muscle.
Overview
Mesenchyme is the loosely organised embryonic connective tissue that fills spaces between the germ layers: small, stellate or spindle-shaped cells with large oval nuclei and fine processes that touch one another, in an abundant, watery ground substance with few fine fibres. Most mesenchyme arises from mesoderm; in the head and neck much of it comes from neural crest (ectomesenchyme), forming facial bones, cartilages, dentin and connective tissue. Mesenchymal cells are migratory and highly proliferative, and their transition from epithelial cells (epithelial–mesenchymal transition, EMT) is a key event in gastrulation and neural-crest formation.
Mesenchymal cells differentiate into all connective-tissue cells — fibroblasts, chondroblasts, osteoblasts, adipocytes — as well as smooth muscle, endothelium and blood cells. A related embryonic tissue, mucous connective tissue (Wharton jelly) of the umbilical cord, is rich in hyaluronan.
In adults, mesenchymal stem/stromal cells (MSCs) persist around blood vessels (pericyte-like) in bone marrow, fat, umbilical cord and other tissues. By consensus criteria they adhere to plastic, express CD73, CD90 and CD105 but not haematopoietic markers (CD34, CD45), and can differentiate into bone, cartilage and fat in vitro.
- Location
Embryo (mesenchyme); umbilical cord (Wharton jelly); adult perivascular niches in bone marrow, adipose tissue and other connective tissues.
Anatomy
- Development
Originates largely from paraxial and lateral-plate mesoderm and, in the head, from neural crest via EMT.
Function
- Gives rise to connective tissues, cartilage, bone, fat and smooth muscle.
- Supports haematopoiesis (marrow stroma) and tissue repair; immunomodulation.
Clinical significance
Sarcomas and EMT in cancer
Malignant tumours of mesenchymal origin are sarcomas. Carcinoma cells that undergo EMT gain mesenchymal features (vimentin, motility), enabling invasion and metastasis.
MSC-based therapies
MSCs are being investigated for graft-versus-host disease, cartilage repair and inflammatory disorders, mainly through paracrine and immunomodulatory effects; many unregulated "stem-cell clinic" uses lack evidence.
Compiled from standard anatomy and physiology references — see the Cells & Tissues sources. For education only; not medical advice.