Defining cell culture media for regenerative medicine 

Introduction 

Cell cultures systems continue to optimize and improve as the field of regenerative medicine advances and cell-based therapies and tissue-engineered products become more prevalent. Culturing cells for downstream clinical applications or the production of a therapeutic product requires strict adherence to Current Good Tissue Practice (cGTP) and Current Good Manufacturing Practice (cGMP) guidelines, in addition to the use of a defined culture system. This is critical not only for the cell culture media, but also attachment substrates, dissociation solutions, cryopreservation solutions, culture additives, and differentiation methods.  

This article will review some of the standard terminology in the field used to define the level of purity of components in the culture system that are often misunderstood. 

GMP 

GMP practice and regulations are often misunderstood, and sadly sometimes even mis-represented by many organizations in their marketing of a company, therapy, or product. One common misconception is that a product or reagent can be classified as “GMP”.  GMP refers to the regulations enforced by the FDA around the design, monitoring, and control of manufacturing processes and facilities.  Following cGMP guidelines assures the identity, quality, and purity of a final product, and the formal system of controls put in place helps manufacturers consistently meet quality standards in the products.  While products can be made following cGMP guidelines, the products themselves are technically not classified as “GMP” themselves. 

Another misconception is that an organization or a product is expected to have a “GMP certificate” issued by the FDA. In reality, while the FDA audits manufacturers to ensure they are following cGMP guidelines, they look for deviations and compliance, and do not actually certify the manufacturers or the products themselves.  The FDA monitors the use and practice of the regulations around cGMP in order to ensure that a product made under the organization’s workflow is safe to use.  This compliance to cGMP is only one factor that is considered for new drug or therapy approval. 

More information on the FDA regulations around cGMP can be found in several sections of the Code of Federal Regulations (CFR) Title 21, aka “21 CFR”.   

Ancillary Materials 

Ancillary materials are the raw materials that are used in the manufacture of cell, gene, and other tissue-engineered or cell-based therapies but are not intended to be a part of the final product or therapy.  Ancillary materials (sometimes abbreviated AM or simply called “raw materials”) are most generally the components, reagents, and other ingredients used in cell culture, expansion, production, and processing of a final therapeutic product.  Ancillary materials include the cell culture media, chemical reagents, matrices, additives, culture ware, and many other parts of the cell culture system.  

While ancillary materials are not intended to be a part of the final product, their presence in the manufacturing process may affect the therapeutic product’s safety, efficacy, and consistency.  It is important for cell therapy manufacturers and researchers working toward regenerative medicine to qualify and select appropriate ancillary materials for a product early in the development stage in order to avoid major changes to culture environments, media recipes, and other protocols as product development approaches a stage of clinical regulation.    

Ancillary materials are classified in four general tiers that range from low risk to high risk of inclusion of the reagent in a therapeutic product.  Depending on the risk classification of a specific reagent, different degrees of qualification may be additionally required to determine source, identity, purity, safety, and suitability of the product for use in a regenerative medicine product or therapy.  The qualification guidelines of ancillary materials is outlined in Chapter <1043> of the United States Pharmacopeia (USP). 

Terminology in Component Definition 

Serum-free (SF) media generally means that a media formulation does not contain any serum, plasma, or similar materials in the product.  Serum-free media may contain processed biological materials that are derived from blood, serum, or plasma – including albumin, transferrin, low-density lipids, platelet lysate, carrier proteins, or hormones. 

A chemically defined (CD) medium is one in which all of the chemical components of the medium and their exact concentrations are known. In order to be chemically defined, a medium must contain recombinant versions of required protein factors. A chemically defined medium would use recombinant albumin protein in place of human or bovine serum albumin, for example. 

Xeno-free (XF) media contain no animal-derived components, but may contain human-derived components. The word “xeno” means “alien” or “strange” – or in this case, “non-human”. Xeno-free media can be classified either as defined (if all proteins are known and human-derived) or chemically defined (if all proteins used are human recombinant proteins). 

Animal component-free (ACF) media is one more step forward in improving the definition of cell culture media. Animal component-free media contain only synthetic or recombinant factors, and often this definition encompasses the materials used to produce the media components as well as the media itself. 

Similarly, animal origin-free (AOF) media and reagents are those that do not contain materials derived directly from human or animal tissue, serum, or body fluid in the final product or manufacturing of the product.   

Summary 

Working with a highly pure and defined cell culture medium and culture environment is key for the realization of regenerative medicine applications. Successful cell cultures require both optimized protocols and high-quality reagents. Increasing the chemical definition of cell culture media and choosing ancillary materials and reagents produced following cGMP guidelines will improve consistency and validity of experimental results, and ultimately enable the reproducible generation of quality-assured cells for the development of breakthrough clinical uses. 

Captivate Bio is dedicated to high-quality reagents with a commitment to transparency in our manufacture to ensure that we are effectively driving research toward clinical goals. Captivate Bio’s quality team will work with you to select, source, or manufacture the right tool for your cells, from research to therapy, and everything in between.