12/05/2023

U-937 cells

U937 is a pro-monocytic cell line widely used in biomedical research. Mainly, it is an in vitro model to study the potential effects of toxins, drugs, and other molecules. Moreover, the cell line may help to understand molecular mechanisms and signaling pathways in immune cells.

In this article, we will talk about the basics of the U937 cell line. Particularly, you will learn:

Origin and general characteristics of the U937 cells
U937 cell line: Culturing information
Advantages & disadvantages of U937 cells
Applications of U937 cell line in research
U937 cells: Research publications
Resources for U937 cell line: Protocols, Videos, and More

1. Origin and general characteristics of the U937 cells

This section of the article will go over the origin and general characteristics of the acute myeloid leukemia (AML) cell model, U937. You will know: What is U-937 leukemia cell line? What type of cell is U937? Where do U937 cells come from? What are U937 cell line characteristics?

The U937 cell line is pro-monocytic. It was obtained from the pleural effusion of a 37 years old male (Caucasian) with generalized histiocytic lymphoma. The cell line was established by Sundstrom and Nilsson in 1976 [1].
U937 are round-shaped cells and exhibit monocyte-macrophage cell type morphology.
The U937 monocytes have an average diameter of approximately 14 μm.
U937 cell line has capacity to differentiate into immune cells including monocytes, macrophages, or dendritic cells in response to different stimuli.

U937 Vs THP-1 cell line

U937 and THP-1 both are pro-monocytic cell lines. The basic difference between these AML cell models is of origin and maturation stage. U937 cells have been isolated from tissue whereas THP-1 has a blood leukemia origin. On the other hand, U937 is at a more mature stage than THP-1 cells [2].

Erythrocytes and monocytes educated in medical lab.

2. U937 cell line: Culturing information

Knowing the following key point for culturing U937 cells can make your work easy and efficient with it. You will learn: What is the doubling time of U937 cells? Is the U937 cell line adherent or suspension? What is U937 media? How do you culture U937 cells?

Key Points for Culturing U937 Cells

Population Doubling Time:	The average population doubling time of U937 cells is 36 hours. However, it may range between 48 and 72 hours.
Adherent or in Suspension:	U937 macrophages are round in shape and grow in suspension cultures.
Seeding Density:	1 x 10⁵ cells/mL seeding density is recommended for U937 cells. No passaging solution is required for suspended cells. They are diluted with fresh medium and counted. The cells are seeded at the required cell density into a new flask.
Growth Medium:	U937 cell culture is maintained in RPMI 1640 medium. This medium is supplemented with 2.0 mM L-glutamine, 2.0 g/L NaHCO3, 2.0 g/L L-glucose, and 10% FBS for optimum cell growth. Media is replaced 1 to 2 times a week.
Growth Conditions (Temperature, CO2):	U937 cell cultures require a 37°C humidified incubator with a 5% CO2 supply for ideal growth.
Storage:	U937 cells are kept in the vapor phase of liquid nitrogen or at below -150°C temperature to maintain cell viability for longer terms.
Freezing Process and Medium:	CM-1 or CM-ACF freezing media is used for freezing human macrophage cell line U937. A slow freezing method (gradual 1°C drop in temperature) is recommended to protect maximum cell viability.
Thawing Process:	Frozen vials are kept in a 37°C water bath until a small ice clump is left. The cells are added with fresh media and centrifuged. Media is discarded and the cell pellet is resuspended and poured into a new flask. U937 cells exhibit a comparatively fast freezing recovery.
Biosafety Level:	Biosafety level 1 laboratory settings are recommended for U937 cell culturing.

U-937 in suspension culture at different cell densities.

3. Advantages & disadvantages of U937 cells

U937 cells possess a unique mixture of pros and cons that make them an ideal research tool. The prominent advantages and disadvantages of U937 cell culture are discussed below.

Advantages

The main advantages of the U937 cell line include:

Higher stability: U937 cell line exhibits high stability due to its histiocytic origin compared to primary blood leukemia cells. Moreover, these cells can be cultured indefinitely and are genetically homogeneous thus, serve as a convenient model for research studies.
Differentiation: U937 cells have the ability to differentiate into other immune cells such as monocytes, macrophages, or dendritic cells when subjected to a stimulus. This helps in understanding the cellular mechanisms involved in generating immune responses.
East to maintain: U937 cells are easy to culture and maintain in research laboratories. There are no complicated procedures or protocols to follow for culturing U937 cells.

Disadvantages

Here are some disadvantages associated with the U937 cell line.

Bacterial infection: U937 cells are susceptible to bacterial infections if aseptic culture conditions are not maintained. Almost all bacterial infections can be identified via pH change and turbidity of culture media except mycoplasma. They silently grow and spread in cultures and affect cell morphology, behavior, gene expression, etc.
Chromosomal abnormalities: The U937 cells possess chromosomal aberrations including translocations. This may affect the experimental outcomes and reproducibility of results.

4. Applications of U937 cell line in research

The U937 monocytic cell line has plentiful research applications in the biomedical field. Some of the applications of U937 cells include:

Studying the biology of monocytes/macrophages: The U937 cell line is a frequently used cell model to investigate the functions and regulation of monocytes and macrophages, including phagocytosis, antigen presentation, and cytokine production. Such as a study conducted in 2023 used U937 to study the potential effects of Glycomacropeptide on the regulation of inflammatory response in human macrophage cells. The study revealed that glycomacropeptide has anti-inflammatory properties thus, reduces cytokine levels in the cell [3].

Cancer research: U937 cells are used to study cellular mechanisms and signaling pathways involved in cancer. Moreover, they are used to screen anticancer drugs and evaluate new cancer therapies. A recent study used U937 myeloid leukemia cell line to investigate the anti-cancer effect of fresh and steamed Kale juice. The researchers found that the juice exerts pro-apoptotic activities in cancer cells through a caspase-dependent pathway [4].
Toxicology studies: The human monocytic cell line U937 is frequently used to study the toxicity of environmental pollutants and other chemicals. Such as a study used U937 and five other cell lines to assess the potential cytotoxic effects of polyethylene microplastics [5].

5. U937 cells: Research publications

The following are some interesting and prominent research studies featuring U937 cells.

Magnoflorine enhances LPS-activated pro-inflammatory responses via MyD88-dependent pathways in U937 macrophages

This study published in Planta Medica (2018) proposed that a major bioactive metabolite obtained from the Tinospora crispa plant has a high potential on augmenting immune responses in U937 macrophages.

Effect of Peganum harmala seeds extract on nitric oxide in U937 monocytes and macrophages

This research paper was published in the International Journal of Medical Laboratory in 2020. In this study, researchers evaluated the potential effects of Peganum harmala seed extract on nitric oxide production in U937 monocytes and macrophages.

Evaluation of potential toxicity of polyethylene microplastics on human derived cell lines

This study published in Science of the Total Environment (2022) assessed the potential cytotoxic effect of environmental pollutants, i.e., polyethylene microplastics, on U937, THP-1, and other three human cell lines.

Effects of Vitex trifolia L. leaf extracts and phytoconstituents on cytokine production in human U937 macrophages

This research was published in 2020 in BMC Complementary Medicine and Therapies journal. The study explored the effects of different extracts prepared from Vitex trifolia L. plant leaves on the production of cytokines in U937 macrophages.

Low-dose ionizing radiation exposure represses the cell cycle and protein synthesis pathways in in vitro human primary keratinocytes and U937 cell lines

This article published in PLOS One journal (2018) explored the potential effects of low-dose ionizing radiations in U937 cell line and primary keratinocytes.

6. Resources for U937 cell line: Protocols, Videos, and More

U937 cells are extensively used research tools. Some valuable resources explaining the cell culturing and differentiation protocol of U937 cells are mentioned here:

U937 differentiation protocol: This document contains a protocol for differentiating U937 cells. Moreover, it also has a protocol for culturing U937 human myeloid leukemia cells
Subculture of suspension cells: This is a video showing the general protocol for subculturing suspension cell lines like U937.
U937 cell line: This website contains a lot of information on U937 cells. It describes subculturing, freezing, and thawing protocols for U937 monocytes and macrophages.

References

Chanput, W., V. Peters, and H. Wichers, THP-1 and U937 Cells. The Impact of Food Bioactives on Health: in vitro and ex vivo models, 2015: p. 147-159.
Chanput, W., J.J. Mes, and H.J. Wichers, THP-1 cell line: an in vitro cell model for immune modulation approach. International immunopharmacology, 2014. 23(1): p. 37-45.
Córdova-Dávalos, L.E., et al., Protective Effect of Glycomacropeptide on the Inflammatory Response of U937 Macrophages. Foods, 2023. 12(7): p. 1528.
Pungpuag, S., S. Boonpangrak, and Y. Suwanwong, Anti-Leukemic Effects on a U937 Cell Line of Fresh and Steamed Chinese Kale Juice and Their Pro-Apoptotic Effects via a Caspase-Dependent Pathway. Foods, 2023. 12(7): p. 1471.
Gautam, R., et al., Evaluation of potential toxicity of polyethylene microplastics on human derived cell lines. Science of the Total Environment, 2022. 838: p. 156089.