Cell Culture

introduction

Cell culture refers to the process of controlled cultivation of prokaryotic or eukaryotic cells in filter or non-filter flasks or cell culture plates using an appropriate growth medium. This term is primarily applicable to the culture of multicellular animal cells. Specific culture media are used for animal cell cultivation, which typically occurs at a temperature of 37 degrees Celsius in equipment such as CO2 incubators.

Animal cell culture must be conducted under completely aseptic conditions, as the growth rate of these cells is significantly slower than that of bacteria and yeast, making them susceptible to contamination. To prevent bacterial growth, antibiotics like penicillin, streptomycin, or gentamicin are sometimes employed.

Specialized culture media exist for the growth of specific cell types. For instance, there are media that support only the growth of hepatocytes or media in which only neurons, which do not divide, can survive. For cells to proliferate effectively in culture, their density must be kept low. This necessitates periodically passaging the cells into fresh culture media.

If cell density becomes too high, contact inhibition can halt cell proliferation, leading cells to enter a differentiation phase, which is one of the stages of cell culture. One of the objectives of cell culture is to study cells in terms of their growth patterns, nutritional requirements, and the causes of their growth cessation, as variations in these factors can significantly impact the morphology of cells observed under a microscope. Therefore, to study the cell cycle, develop methods for controlling cancer cell growth, and modulate gene expression, it is essential to culture these cells in vitro.

Another application of cell culture is the study of organism development. This involves understanding how a fertilized cell can develop into a multicellular organism, where each cell exhibits distinct morphological characteristics under the microscope. To address this question, the fertilized cell can be cultured in a laboratory setting, allowing for the examination of various stages of cell culture based on its evolution and differentiation.

Cell culture enables the generation of cells at different stages of differentiation, which, with the aid of hormones and growth factors, can differentiate into other cell types. Through cell culture, homogeneous cell populations can be produced, facilitating the study of intracellular activities such as DNA replication, transcription, RNA synthesis, and other metabolic details.

Additionally, after the binding of various molecules to the corresponding membrane receptors, subsequent events and intracellular processes, such as the translocation of these complexes, types of intracellular signaling, and the mechanisms of signal transmission can be investigated. Cultured cells can be preserved at very low temperatures in a frozen state.

Such conditions help maintain the growth rate and genetic composition of these cells, allowing for their thawing and subsequent use at an appropriate time. This process prevents cellular aging, whereas currently, preventing aging in animals is not feasible. When working with laboratory animals, one must consider the systemic changes resulting from the impact of the animal's natural homeostasis or stress from experimental procedures on the results. In contrast, using cell culture completely alleviates this issue.

Moreover, standardizing laboratory tests is simpler and more practical compared to tests on living organisms, as controlling physical and chemical factors in the cellular environment, including pH, temperature, osmotic pressure, and gas pressures like oxygen and carbon dioxide, is much easier in laboratory settings.

Cells can be isolated for laboratory culture (ex vivo) using several methods. Cells can be easily extracted and purified from blood; however, only white blood cells are capable of growing in culture. Mononuclear cells can be released from smooth tissues through enzymatic digestion. Important enzymes used in this process include collagenase, trypsin, or pronase, which break down the extracellular matrix.

Another method for cell culture involves placing tissue pieces in a culture medium. In this approach, cells capable of growing in the culture environment develop. This method is also known as explant culture.

Cells obtained directly from the individual are referred to as primary cells and have a limited lifespan. Most cells, except those derived from tumors, have a finite lifespan. An immortal cell line may be established through random or targeted mutations (such as through artificial gene expression), allowing for indefinite proliferation and serving as a representative of specific cell types.