Human Skeletal Muscle Cells (HSkMC) Culture Protocol

Storage
Preparation for Culturing
Culturing HSkMC
Subculturing HSkMC
Differentiating HSkMC

I. Storage

A. Cryopreserved Vials (150-05a, 150-05f, S150-05a, S150-05f)

Store the cryovials in a liquid nitrogen storage tank immediately upon arrival.

*Be sure to wear face protection mask and gloves when retrieving cryovials from the liquid nitrogen storage tank. The dramatic temperature change from the tank to the room could cause any trapped liquid nitrogen in the cryovials to burst and cause injury.

II. Preparation for Culturing

1. Ensure the Class II Biological Safety Cabinet, with HEPA filtered laminar airflow, is in proper working condition.
2. Sterilize the Biological Safety Cabinet with 70% alcohol.
3. Turn the Biological Safety Cabinet blower on for 10 minutes before beginning cell culture work.
4. Make sure all serological pipettes, pipette tips and reagent solutions are sterile.
5. Follow the standard sterilization technique and safety rules:
   a.    Do not pipette by mouth.
   b.    Always wear gloves and safety glasses when working with human cells even though all the strains have been
          tested negative for HIV, Hepatitis B and Hepatitis C.
   c.    Handle all cell culture work in a sterile hood.

III. Culturing HSkMC

A. Preparing Cell Culture Flasks for Culturing HSkMC

1. Take the Skeletal Muscle Cell Growth Medium (151-500) from the refrigerator. Decontaminate the bottle with 70% alcohol in a sterile hood.
2. Pipette 15 mL of Skeletal Muscle Cell Growth Medium (151-500)* to a T-75 flask (SIAL0641).
   * Keep the medium to surface area ratio at 1 mL per 5 cm².
   For example:
   -  5 mL for a T-25 flask (SIAL0639) or a 60 mm tissue culture dish (SIAL0166).
   -  15 mL for a T-75 flask (SIAL0641) or a 100 mm tissue culture dish (SIAL0167).

B. Thawing and Plating HSkMC

1. Remove the cryopreserved vial of HSkMC from the liquid nitrogen storage tank using proper protection for your eyes and hands.
2. Turn the vial cap a quarter turn to release any liquid nitrogen that may be trapped in the threads, then re-tighten the cap.
3. Thaw the cells quickly by placing the lower half of the vial in a 37 °C water bath and watch the vial closely during the thawing process.
4. Remove the vial from the water bath when only a small amount of ice is left in the vial. Do not let cells thaw completely.
5. Decontaminate the vial exterior with 70% alcohol in a sterile Biological Safety Cabinet.
6. Remove the vial cap carefully. Do not touch the rim of the cap or the vial with your hands to avoid contamination.
7. Resuspend the cells in the vial by gently pipetting the cells 5 times with a 2 mL pipette. Be careful not to pipette too vigorously as to cause foaming.
8. Pipette the cell suspension (1 mL) from the vial into the T-75 flask (SIAL0641) containing 15 mL of Skeletal Muscle Cell Growth Medium (151-500).
9. Cap the flask and rock gently to evenly distribute the cells.
10. Place the T-75 flask (SIAL0641) in a 37 °C, 5% CO₂ humidified incubator. Loosen the cap to allow gas exchange. For best results, do not disturb the culture for 24 hours after inoculation.
11. Change to fresh Skeletal Muscle Cell Growth Medium (151-500) after 24 hours or overnight to remove all traces of DMSO.
12. Change Skeletal Muscle Cell Growth Medium (151-500) every other day until the cells reach 60% confluency.
13. Double the Skeletal Muscle Cell Growth Medium (151-500) volume when the culture is >60% confluent or for weekend feedings.
14. Subculture the cells when the HSkMC culture reaches 85-95% confluency.

IV. Subculturing HSkMC

A. Preparing Subculture Reagents

1. Remove the Trypsin-EDTA solution (T3924) and Trypsin Inhibitor (T6414) from the -20 °C freezer and thaw overnight in a refrigerator.
2. Make sure all the subculture reagents are thawed. Swirl each bottle gently several times to form homogeneous solutions.
3. Store all the subculture reagents at 4 °C for future use.
4. Aliquot Trypsin/EDTA solution (T3924) and store the unused portion at -20 °C if only a portion of the Trypsin/EDTA (T3924) is needed.

B. Preparing Culture Flask

1. Take the Skeletal Muscle Cell Growth Medium (151-500) from the refrigerator. Decontaminate the bottle with 70% alcohol in a sterile hood.
2. Pipette 35 mL of Skeletal Muscle Cell Growth Medium (151-500) to a T-175 flask (SIAL1080) (to be used in Section IV C Step 15.)

C. Subculturing HSkMC

Trypsinize Cells at Room Temperature. Do Not Warm Any Reagents to 37 °C.

1. Remove the medium from culture flasks by aspiration.
2. Wash the monolayer of cells with HBSS (H6648) and remove the solution by aspiration.
3. Pipette 5 mL of Trypsin/EDTA Solution (T3924) into the T-75 flask (SIAL0641). Rock the flask gently to ensure the solution covers all the cells.
4. Remove 4 mL of the solution immediately.
5. Re-cap the flask tightly and monitor the trypsinization progress at room temperature under an inverted microscope. It usually takes about 2 to 5 minutes for the cells to become rounded. The cells may not be completely round during trypsinization and some cells may maintain some processes even though they are loosened from the culture surface.
6. Release the rounded cells from the culture surface by hitting the side of the flask against your palm until most of the cells are detached.
7. Pipette 5 mL of Trypsin Inhibitor Solution (T6414) to the flask to inhibit further tryptic activity.
8. Transfer the cell suspension from the flask to a 50 mL sterile conical tube.
9. Rinse the flask with an additional 5 mL of Trypsin Inhibitor Solution (T6414) and transfer the solution into the same conical tube.
10. Examine the T-75 flask (SIAL0641) under a microscope. If there are >20% cells left in the flask, repeat Steps 2-9.
11. Centrifuge the conical tube at 220 x g for 5 minutes to pellet the cells.
12. Aspirate the supernatant from the tube without disturbing the cell pellet.
13. Flick the tip of the conical tube with your finger to loosen the cell pellet.
14. Resuspend the cells in 5 mL of Skeletal Muscle Cell Growth Medium (151-500) by gently pipetting the cells to break up the clumps.
15. Count the cells with a hemocytometer or cell counter. Inoculate at 10,000 cells per cm² for rapid growth, or at 5,000 cells per cm² for regular subculturing.

V. Differentiating HSkMC

A. Preparing Cell Culture Ware

1. Swirl the Collagen Coating Solution (125-50) a few times to form a homogenous solution.
2. Decontaminate the bottle with 70% alcohol in a sterile hood.
3. Determine the appropriate format to seed HSkMC for the experiment e.g., plates or flasks.
4. Add Collagen Coating Solution (125-50) to tissue culture ware at coating concentration of 1 mL per 10cm² surface area of culture ware for 30 minutes at 37 °C or for 2 hours to overnight at room temperature.
5. Remove the Collagen Coating Solution (125-50) by aspiration in a sterile hood.
6. Wash the Collagen coated surface two times with Dulbecco’s Phosphate Buffered Saline (D8537).
7. The coated flask can be used immediately or stored at 4 °C for up to two weeks.

B. Seeding HSkMC For Differentiation

1. Seed HSkMC in the desired format at 32,000 per cm² for adult HSkMC or 20,000 per cm² for fetal HSkMC in Skeletal Muscle Cell Growth Medium (151-500).
2. Place the cells in a 37 °C, 5% CO₂ humidified incubator overnight and to induce differentiation the next day.

C. Differentiating HSkMC to Myotubes

1. Pre-equilibrate the required amount of Skeletal Muscle Cell Differentiation Medium (151D-250) for differentiation in a 37 °C, 5% CO₂ humidified incubator for 2 hours.
2. Remove Skeletal Muscle Cell Growth Medium (151-500) from tissue culture ware by aspiration. Do not allow cells to dry during medium changes.
3. Add the appropriate volume of Skeletal Muscle Cell Differentiation Medium (151D-250), at 1 mL per 5cm².
4. Incubate the cells in a 37 °C, 5% CO₂ humidified incubator in the Skeletal Muscle Cell Differentiation Medium (151D-250).
5. Change to fresh Skeletal Muscle Cell Differentiation Medium (151D-250) every other day.
6. Multinuclear myotubes will typically form within 3-4 days for fetal HSkMC  and 6-7 days for adult HSkMC.