Difference Between Epithelial and Mesenchymal Cells

Main Difference – Epithelial vs Mesenchymal Cells

Epithelial and mesenchymal cells are two types of cells that show a transition between cell types during embryonic development. Epithelial cells belong to the epithelial tissue while mesenchymal cells belong to the connective tissue. During embryogenesis, mesenchymal-epithelial transition (MET) and epithelial-mesenchymal transition (EMT) occur between epithelial and mesenchymal cells. The main difference between epithelial cells and mesenchymal cells is that epithelial cells line organs, vessels, and cavities, providing protection to the body whereas mesenchymal cells are capable of differentiating into any type of smooth muscle, vascular endothelium, connective tissue, supporting tissue or blood cells.

Key Areas Covered

1. What are Epithelial Cells
      – Definition, Types, Characteristics, Function
2. What are Mesenchymal Cells
      – Definition, Characteristics, Function
3. What is the difference between Epithelial and Mesenchymal Cells
      – Comparison of Key Differences

Key Terms: Epithelial Cells, Mesenchymal Cells, Mesenchymal-Epithelial Transition, Epithelial-Mesenchymal Transition, EMT, MET, Endothelium, Epithelium, Epithelial Tissue, Connective Tissue

What are Epithelial Cells

Epithelial cells line organs, vessels (blood and lymph), and cavities by forming a thin cell layer called the endothelium. It is continuous with the inner tissue lining of the body. The upper side of the epithelial cells is exposed to air or fluids while the bottom is attached to the basement membrane. Epithelial cells are involved in absorption of nutrients, secretion of enzymes and hormones, and excretion of waste. They also act as a barrier against microorganisms and protects the body from dehydration and damage. Some epithelial cells found in ear, nose, tongue and skin have a sensory function. Ciliated epithelial cells in respiratory and reproductive tracts propel substances like dust particles and female gametes, respectively.

Types of Epithelial Cells

The three principal shapes of epithelial cells are squamous, columnar, and cuboidal. Squamous epithelial is flat tile-like. Columnar epithelial cells are shaped like bricks, and cuboidal is dice-like. These cells are arranged in three ways: simple, stratified, and pseudostratified. Simple epithelium contains a single layer of cells. Stratified epithelium contains multiple layers of cells, and pseudostratified epithelium contains a single layer of cells where the nuclei are arranged in different levels.

Figure 1: Types of Epithelial Cells

What are Mesenchymal Cells

Mesenchymal cells are fusiform or stellate cells, which are located between the ectoderm and endoderm in young embryos. The shape of the matured and fixed mesenchymal cells indicates that they moved from the site of origination to a different area where they became rearranged and specialized. Most of the mesenchymal cells are derived from the mesoderm. Some of the mesenchymal cells are developed from the neural crest or surface ectoderm. Mesenchymal cells in the embryo are considered as the most strikingly pluripotential cells, developing at different locations, developing into any types of smooth muscle, vascular endothelium, connective tissue, supporting tissue or blood cells.  

Mesenchymal-epithelial transition (MET) is a biological process in which the mesenchymal cells transform to the epithelium. The MET is a reversible process. The reverse process of MET is EMT (epithelial-mesenchymal transition). The MET may occur in normal development as well as in the cancer metastasis. During embryogenesis, MET occurs in nephrogenesis, somitogenesis, cardiogenesis, and hematogenesis. The gene expression profiles are changed during the transition, and a unique signaling pathway is involved in the induction of the pathway.

Figure 2: Epithelial-Mesenchymal Transition

Difference Between Epithelial and Mesenchymal Cells

Definition

Epithelial Cells: Epithelial cells are cells which are arranged in one or more layers, forming part of a lining of the body surface.

Mesenchymal Cells: Mesenchymal cells are fusiform or stellate cells which are located between the ectoderm and endoderm in young embryos.

Belong to

Epithelial Cells: Epithelial cells belong to epithelial tissue.

Mesenchymal Cells: Mesenchymal cells belong to connective tissue.

Origins

Epithelial Cells: Epithelial cells are derived from endoderm (epidermis), ectoderm (the lining of the gastrointestinal tract), and mesoderm (the inner linings of body cavities).

Mesenchymal Cells: Mesenchymal cells are derived from the mesoderm. Some of the mesenchymal cells are developed in the neural crest or surface ectoderm.

Transition

Epithelial Cells: Epithelial cells are capable of transitioning into mesenchymal cells in EMT.

Mesenchymal Cells: Mesenchymal cells are capable of transitioning into epithelial cells in MET.

Levels of Differentiation

Epithelial Cells: Epithelial cells are specialized cells.

Mesenchymal Cells: Mesenchymal cells are unspecialized cells.

Function

Epithelial Cells: Epithelial cells line organs, vessels, and cavities providing protection to the body.

Mesenchymal Cells: Mesenchymal cells are capable of differentiating into any type of smooth muscle, vascular endothelium, connective tissue, supporting tissue or blood cells.

Conclusion

Epithelial cells are specialized cells, which line cavities, organs, and vessels in the body. In contrast, mesenchymal cells are unspecialized cells, which are capable of differentiating into any type of cells in the body at any time. The main difference between epithelial and mesenchymal cells is their levels of differentiation and function in the body. During embryogenesis, epithelial cells are derived from each of the three embryological germ layers. But mesenchymal cells are only derived from mesoderm and ectoderm. The reversible transition of cells between each cell type may occur in EMT and MET processes.

Reference:

1. “Epithelial Cells.” School of Life Sciences | Ask A Biologist. N.p., 15 Feb. 2011. Web. Available here. 01 June 2017. 
2.”Mesenchymal cells.” Mesenchymal Cells – Medical Definition from MediLexicon. N.p., n.d. Web. Available here. 01 June 2017.
3. Kalluri, Raghu, and Robert A. Weinberg. “The basics of epithelial-mesenchymal transition.” The Journal of Clinical Investigation. American Society for Clinical Investigation, 01 June 2009. Web. Available here. 01 June 2017.

Image Courtesy:

1. “Blausen 0356 Epithelium Classification” By Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia
2. “Epithelial-Mesenchymal Transition” By Micalizzi D, Farabaugh SM, Ford HL – (CC BY-SA 3.0) via Commons Wikimedia