June 21, 2024
Cell Processing

Cell Processing: The Journey of Cells from Collection to Application

Collection of Cells

One of the first major steps in cell processing is the collection of cells from the source. For some applications, cells can be collected from donated tissues or organs. For example, stem cells used in transplantation therapies are often collected from bone marrow, peripheral blood, or umbilical cord blood.

The collection method depends on the cell type and source. Bone marrow collection involves aspirating liquid marrow from the bones of the donor. This is typically done under anesthesia in an outpatient procedure. Umbilical cord blood is collected by draining the blood from the placenta and umbilical cord after a baby is delivered. Peripheral blood stem cells are collected through an apheresis machine that circulates the donor’s blood through a machine that separates out the stem cells.

Processing and Isolation of Cells

Once cells are collected, they undergo processing to isolate the desired cell type and prepare them for storage or use. This often involves separating cell types based on differences in physical or chemical properties.

For stem cells, density gradient centrifugation is commonly used. This uses the differences in density between mononuclear cells containing stem cells and other components of blood. Centrifuging a suspension of cells through a special solution isolates the mononuclear fraction.

Other methods like fluorescence activated cell sorting (FACS) and magnetic activated cell sorting (MACS) take advantage of specific cell surface markers. Antibodies targeting markers on the desired Cell Processing type are used to label them before applying a magnetic or fluorescence based method to separate those cells from others.

Cytapheresis further refines stem cell collections obtained through apheresis. It runs the blood through a machine that separates cells based on size into fractions enriched for stem cells versus other blood components.

Cell Expansion and Activation

For some applications, isolated cells need to be expanded or activated in culture before use. Stem cells are commonly expanded in vitro by culturing at high densities in conditions that promote proliferation. Growth factors are often added to culture media to stimulate stem cell division and maintain an undifferentiated state.

T cells collected for adoptive cell therapies are also expanded in vitro. These have typically been activated and stimulated to differentiate and proliferate into cytokine-secreting effector T cells before infusion into patients. Activation involves exposing T cells to anti-CD3/CD28 antibodies attached to beads or artificial antigen presenting cells. The activated T cells are then expanded rapidly in culture over 1-3 weeks.

Cell Cryopreservation and Banking

Many cell processing protocols also involve cryopreserving or banking collected cells for future use. This allows standardized quality tested ‘doses’ of cells to be stored and quickly retrieved when a transplant is needed. It also enables banking of allogeneic cell sources for off-the-shelf therapeutic use.

Cryopreservation is commonly done using methods like slow freezing or vitrification. It involves gradually lowering the temperature of cells suspended in a cryoprotectant solution like dimethyl sulfoxide. This minimizes ice crystal formation that could damage cells during freezing.

Cells are typically stored in the vapor phase of liquid nitrogen at temperatures below -150°C. At these ultra-low temperatures, all metabolic processes essentially stop, allowing long term storage. Cell banks maintain inventory of cryopreserved products and undertake testing to ensure stability and post-thaw viability over time.

Quality Control and Regulation

Stringent quality control measures are essential throughout cell processing to ensure safety, purity, potency and stability. Tests are performed to detect microbial contamination and endotoxin levels. Viability, sterility, and identity testing establishes the cell phenotype matches the expected or desired type.

Regulatory bodies provide oversight and approve standard operating procedures for processing facilities. In the United States, the Food and Drug Administration regulates cell-based products and provides guidelines. Facilities must meet current Good Manufacturing Practice standards and adhere to regulations for donor screening, product characterization and record keeping.

Processing cells from collection to clinical application is a complex multi-step process involving specialized equipment, testing and rigorous quality control. Continued advances in cell isolation, expansion and cryopreservation techniques will help enable wider clinical applications of cell-based therapies. Standardized, high quality cell processing remains critical for establishing the benefits and safety of these emerging therapies

1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it