PROTOCOL FOR OBTAINING URINARY-DERIVED STEM CELLS (USCs)
NECESSARY MATERIALS
Type Specific Element
Biological: Fresh sterile urine (50–200 ml)
Equipment: Centrifuge (capable of 400–500 g)
Incubator (37°C, 5% CO₂)
Biosafety cabinet (type II)
Inverted microscope
Culture: T25 flasks or 6–12-well plates
Sterile pipettes and tips
50 ml Falcon tubes
Media and reagents: DMEM/F12 medium (1:1)
10% Fetal bovine serum (FBS, filtered)
1% Penicillin/Streptomycin
1% L-Glutamine
PBS (buffered saline)
CULTURE MEDIUM PREPARATION
In a sterile flask, mix:
• 90 ml DMEM/F12 (1:1)
• 10 ml FBS (warmed to 37°C and filtered)
• 1 ml Penicillin/E
• 1 ml L-Glutamine
Filter the prepared medium (0.22 μm) and store at 4°C.
STEP-BY-STEP PROCEDURE
1. Urine Collection
• Collect 50–200 ml of sterile urine, ideally from the first urination of the day.
• Process urine within the first 2 hours of collection.
2. Centrifugation
• Centrifuge the sample at 400–500 g for 10 minutes at room temperature (2,000 rpm or more).
• Carefully remove the supernatant, leaving the cell pellet at the bottom.
3. Washing
• Add 10 ml of sterile PBS to the pellet and resuspend gently.
• Centrifuge again at 400 g for 10 minutes.
• Remove the supernatant.
4. Cell Seeding
• Resuspend the pellet in 1–2 ml of culture medium.
• Seed in a T25 flask or 6-well plate.
• Incubate at 37°C, 5% CO₂, with controlled humidity.
5. Medium Change
• After 24 h, change the medium to remove non-adherent cells.
• Then change the medium every 2–3 days.
6. Monitoring
• Colonies of USCs will begin to appear between 5 and 10 days.
• Upon reaching 70–80% confluence, perform the first subculture (passage 1).
7. Subculture (Passage)
• Wash with PBS, then use 0.05% trypsin for 3–5 min to detach cells.
• Resuspend in fresh medium and seed in a clean flask (T75 or T25).
• USCs can be passaged up to passages 5–7 before losing potency.
CELL IDENTITY VERIFICATION
By flow cytometry (optional):
Positive markers: CD44+, CD73+, CD90+, CD105+
Negative markers: CD34-, CD45-
By differentiation (optional):
• In specific media, they can differentiate into:
o Osteoblasts (bone)
o Adipocytes (fat)
o Chondrocytes (cartilage)
STEPS TO PREPARE USCs FOR INTRAVENOUS INJECTION
1. Detachment with trypsin (as already done)
• Use 0.05% trypsin-EDTA, incubating for 3–5 minutes at 37°C.
• When cells round up and detach, neutralize immediately with complete medium (containing FBS).
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2. Cell Washing
⚠It is essential to completely remove fetal bovine serum (FBS) and trypsin to avoid adverse reactions.
• Centrifuge at 400 g for 5 minutes.
• Discard the supernatant (containing trypsin and FBS).
• Wash with sterile PBS without Ca²⁺/Mg²⁺.
• Centrifuge and repeat the wash at least twice.
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3. Resuspension for Injection
IMPORTANT:
The vehicle must be:
• Sterile
• Non-pyrogenic
• Compatible with human intravenous infusion
• Non-toxic to cells
SAFE AND STANDARD OPTION:
Sterile PBS (Ca²⁺/Mg²⁺ free) or
Sterile physiological saline (0.9% NaCl) for injection
Many protocols also use Plasmalyte A or Lactated Ringer's, but PBS and 0.9% NaCl are the most common and readily available.
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How to resuspend them?
• Cell count (optional, but recommended).
• Resuspend the CSUs in the chosen vehicle, to a final concentration of:
o 1–10 million cells/ml
• Keep the suspension refrigerated (4°C) if you will use it within 2 hours.
• Inject slowly into a vein or by infusion (according to the clinical/experimental protocol).
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CRITICAL CONSIDERATIONS
Aspect Recommendation
Route of administration: IV (peripheral vein or tail in animals)
Maximum time between preparation and injection: ≤2 hours
Compatible vehicle: PBS or 0.9% sterile NaCl
What to avoid: FBS, antibiotics, and trypsin residue
Optional: Filter through a sterile 40 μm mesh to avoid aggregates