Passaging Adherent Mammalian Cells

Research will be limited to:
- Cell Type: Adherent Mammalian Cells
- Method: Trypsinization
- Measurement: Hemocytometer Cell Counting
- Cell Lines: HEK293, HeLa
- Parameter Optimization: Trypsinization Time and Split Ratios

Strategy: The user needs a detailed protocol for passaging two specific adherent cell lines (HEK293 and HeLa). While the general process of trypsinization is standard, the specific parameters (incubation time, split ratios, and seeding densities) vary between these two lines. I need to find the specific trypsinization times (HEK293 is typically more loosely adherent than HeLa) and the recommended split ratios for routine maintenance. Additionally, I will gather the standard hemocytometer calculation steps to provide a complete implementation guide.
Queries:
- HEK293 vs HeLa trypsinization time and split ratios protocol
- hemocytometer cell counting calculation formula for adherent cells passage
- standard operating procedure trypsinization HEK293 HeLa cells

🔍 Reading and summarizing 5 new websites...

1. HEK Cell Splitting and Maintenance - Şen Lab
2. [DOC] HEK293 Maintenance
3. [PDF] Sub-culturing (splitting) protocol for HEK293 cells:
4. Manually Counting Cells in a Hemocytomer | Thermo Fisher Scientific
5. How to Count Cells with a Hemocytometer or Automated Cell Counter

Found 4 websites. Summarized content:

HEK Cell Splitting and Maintenance - Şen Lab
Here's a protocol for passaging adherent mammalian cells, specifically HEK293 and HeLa, focusing on trypsinization time, split ratios, and hemocytometer cell counting, based on the provided website content:

Key Considerations (from Şen Lab's HEK Cell Splitting Protocol):

• Cell Types: Primarily addresses HEK293 and HEK293T cells, but suggests the protocol principles are applicable to other HEK cell lines. No specific information about HeLa cells is given.
• Cell Doubling Time (HEK293/T): Doubling time varies. HEK-293 cells: 24-48 hours. HEK-293T cells: 12-20 hours (typically closer to 12 hours in their lab). Important to establish the rate for your specific cells.
• Confluence: Maintaining a good level of confluence is necessary for healthy cells. Cultures that are less than 5% confluent can struggle to grow while cultures near 100% confluence will have many dead cells. Aim for splitting cells before they reach 100% confluence. Figures show cells at 80% and 70% confluence.
• Cell Health Indicators: Healthy cells adhere to the plate. Unhealthy cells float. Dead cells are smaller with a dark "ring." Media color change (DMEM with phenol red turning orange/yellow) indicates dead cells or potential contamination.

Protocol Components (implied but not explicitly detailed – further sections of the protocol, accessed through the listed links, would be required for full details):

1. Preparations: (Details not in provided content, but referenced as part of the protocol)
2. Calculate Split Fraction and Seed Amount: (Details not in provided content, but referenced as part of the protocol) The 1:25 and 1:10 split ratios are mentioned in descriptions of the figures.
3. Splitting the Cells: (Details not in provided content, but referenced as part of the protocol) This section would likely detail the trypsinization process.

Missing Information (requiring further research beyond this document):

• Specific Trypsinization Time: The provided text does not specify an optimal trypsinization time.
• Detailed Splitting Procedure: The user needs more than just "splitting the cells". What tools and equipment are needed? What volumes of reagents are needed?
• Hemocytometer Cell Counting Details: The provided text mentions cell counting indirectly, but not the Hemocytometer.

Summary for Optimizing Trypsinization Time & Split Ratios:

The document focuses on cell health and confluence. Determining optimal trypsinization time and split ratio requires:

1. Following the complete 'Splitting the cells' protocol linked on the webpage and adjusting the protocol based on your cell culture and resources.
2. Empirical Testing: Testing various trypsinization times (starting with standard protocols, perhaps 1-5 minutes) and a range of split ratios (e.g., 1:2, 1:5, 1:10, 1:20).
3. Hemocytometer use: Use a hemocytometer to accurately count cells after trypsinization to determine cell viability and concentration for calculating appropriate seeding densities based on the chosen split ratios.
4. Consider the use of Trypsin-EDTA: This is a common reagent that dissociates adherent cells from the culture vessel (flasks, petri dishes etc).

Since the specific method of hemocytometer cell counting is not mentioned in the document, the user will need to find further resources.

[DOC] HEK293 Maintenance
Here's a summary of the relevant information from the website concerning passaging adherent mammalian cells (HEK293 and HeLa), specifically focusing on trypsinization time, split ratios, and hemocytometer cell counting, as requested:

HEK293 Passaging Protocol (Based on information from the provided Website):

1. Preparation:

   • Use Ca++/Mg++ free Dulbecco's phosphate-buffered saline (D-PBS) to rinse the cell layer and remove serum. Serum contains trypsin inhibitors.

2. Trypsinization:

   • Add 1 ml of 0.05% Trypsin solution to a 10 cm dish.
   • Incubate at 37°C in a 5% CO2 incubator for 3-5 minutes.

3. Neutralization and Detachment:

   • Remove dish from the incubator and add 1 ml complete medium (DMEM + 10% FBS + 1x Pen/Strep).
   • Triturate the cells approximately 30 times until cells are in suspension.

4. Subculturing (Splitting):

   • For seeding a new dish after counting, plate cells at the appropriate density.
   • Alternatively, use a subcultivation ratio of 1:3 to 1:8.

5. Hemocytometer Cell Counting (Implied, not explicitly detailed):

   • The protocol assumes cell counting is performed "if seeding a new dish". The website DOES NOT provide detailed instructions for hemocytometer cell counting.
   • In their transfection procedure the cell density should be ~ 2x10^6 cells/mL.

Important Considerations related to HEK293 cells:

• HEK293 cells are only semi-adherent.
• The website does not provide specific information for HeLa cells; however the protocol as stated should work.

[PDF] Sub-culturing (splitting) protocol for HEK293 cells:
This protocol provides a detailed procedure for passaging HEK293 cells using trypsinization and includes considerations for cell counting, although cell counting is not explicitly detailed beyond calculating split ratios.

Here's a summary focusing on the relevant parameters:

• Cell Lines: HEK293 (implicitly also suitable for adherent mammalian cells generally as the initial request indicated)
• Method: Trypsinization
• Trypsinization Time: Approximately 2 minutes at 37°C. Monitor cell detachment under a microscope and proceed when ≥90% of cells have detached.
• Split Ratios: The document refers to split ratios implicitly as "dilution" (1:5, 1:8, 1:10 etc.). These are determined when transferring the cell suspension to new culture vessels to achieve the desired seeding density. The specific ratio depends on the cell count and target cell density needed for the next passage.
• Hemocytometer Cell Counting: While not explicitly detailed, the mention of split ratios indicates the use of cell counting to achieve desired seeding densities. Hemocytometer counting is implied here.
• Procedure Highlights:
  • Wash cells with PBS to remove serum.
  • Use 2 mL trypsin per plate
  • Add complete growth medium to neutralize trypsin after detachment.
  • Pipette thoroughly to disperse cells.
  • Label plates with cell line, date, passage number, and dilution (split ratio).

How to Count Cells with a Hemocytometer or Automated Cell Counter

Protocol for Passaging Adherent Mammalian Cells (HEK293, HeLa) using Trypsinization and Hemocytometer Cell Counting

This protocol outlines optimization of trypsinization time and split ratios for passaging adherent mammalian cells, specifically HEK293 and HeLa cell lines, using hemocytometer cell counting.

I. Cell Dissociation (Trypsinization - Optimization Needed)

• Adherent cell lines need to be fully dissociated into a single-cell suspension using trypsin (or other dissociation methods). Optimization of trypsinization time is necessary to achieve a homogenous, single-cell suspension with minimal clumps or doublets.
• Pre-Sampling Verification: Before starting the cell count, "pre-sample" and visualize cells using a microscope to verify a single-cell suspension with minimal clumps or cell doubles. This step is critical for accurate cell counting.

II. Cell Counting using a Hemocytometer

1. Preparation:
   • Clean the hemocytometer and coverglass with lens paper to remove dust and particles.
   • Align the coverslip over the chamber.
2. Loading Cells:
   • Resuspend cells by carefully pipetting the suspension volume up and down before sampling to ensure a representative sample.
   • Load the recommended volume of cell suspension (unlabeled or trypan blue-labeled). Ensure the meniscus of the fluid goes past the grid but do not overfill. Overfilling changes the chamber volume and causes inaccurate counts.
3. Counting:
   • Use a low-magnification microscope (usually 10x objective).
   • Count cells in one or more of the major (1 mm) squares. The Neubauer chamber is the typical grid pattern for eukaryotic cell culture. Each major square is 1 mm x 1 mm, and the height of the chamber is 0.1 mm, so the fluid volume above each square is 0.1 μL.
   • Establish a consistent counting rule (e.g., "count cells touching the right or bottom border, but not those touching the left or top border"). Apply this rule to every square to avoid double-counting.
   • Use a tally counter (mechanical or digital) to count cells. A differential counter with multiple keys is helpful for live/dead cell counts.
   • Count in the corner squares for most cell lines. Smaller cells such as red blood cells may be counted in the center square using a higher magnification.
4. Number of Squares:
   • Count the four corner squares on one side, or eight squares from both sides. Count more squares for low-density samples and fewer for high-density samples to achieve an accurate average. If the count is too high, dilute the suspension and repeat.
5. Cell Viability (Trypan Blue Exclusion):
   • Mix cells with trypan blue. In the example provided, they added 10 μl of 0.4% trypan blue to 10 μl of cell samples. Note the dilution factor. Incubate according to manufacturer's instructions for the dye.
   • Live cells (intact membranes) exclude trypan blue (appear clear). Dead cells (ruptured membranes) take up trypan blue (appear blue).
   • Count live and dead cells separately in each square.
6. Calculations:
   • Cell Density (cells/mL): (Average cell count per major square) x 10^4 x (Dilution factor).
   • Percent Viability: (Number of live cells) / (Total number of cells (live + dead)) x 100%.

III. Seeding Cells (Split Ratio Optimization):

• Use the calculated viable cell density to determine the volume of cell suspension needed to seed new vessels at the desired density. Split ratios should be optimized to promote healthy cell growth and prevent overgrowth. This needs to be determined empirically for each cell line (HEK293, HeLa) under specific culture conditions.
• A cell culture log should be kept to track cell viability and health.

IV. Post-Counting Clean Up:

• Spray hemocytometer and coverglass with 70% ethanol to kill the cells.
• Rinse with DI H2O and wipe dry, then wipe clean with lens paper before storing.