* Perform every step in the biosafety cabinet
Generation of normal mouse bladder assembloids
* This protocol is standardized to a preparation of culture in 2 wells of 12-well plate (= 10 assembloids).
* A day before, thaw 60 µl of Matrigel overnight at 4 °C.
* Prepare long-term (> 6 months) bladder organoids, mouse embryonic fibroblasts (MEF), HULEC, bladder smooth muscle cells (BSMC) cultures in advance.
1. Prepare two sheets of Parafilm at the size of 1.5 cm x 1.5 cm, put them in a 100 mm petri dish.
* Spray your gloves and the Parafilm with 70 % (vol/vol) ethanol.
2. Prepare long-term bladder organoids.
a. Release the bladder organoids from Matrigel drop by physically pipetting the organoid medium and collect them in a new 15 ml tube.
b. Centrifuge at 1,500 rpm, 4 °C, for 5 min.
c. Remove the supernatant, wash the organoid pellets with 1 ml of Advanced DMEM/F12 medium.
d. Centrifuge at 1,500 rpm, 4 °C, for 5 min.
e. Remove the supernatant, add 1-2 ml of DMEM containing 10 % FBS and 1 % penicillin/streptomycin.
f. Transfer the organoids with medium to the 35 mm petri dish, plate the dish on ice.
3. Prepare MEF and HULEC mixture.
a. Prepare 1.5 x 106 MEF and 2 x 105 HULEC, put together in one microcentrifuge tube.
b. Centrifuge at 1,500 rpm, 4 °C, for 3 min.
c. Remove the supernatant, add 40 μl Matrigel to cell pellets (perform on ice), plate on ice
4. Set 20p pipette at 4 μl, take one organoid only.
* Take < 1 μl of organoid (+ medium that follows when picking the organoid) while holding it.
5. Take up to 4 μl of MEF and HULEC mixture.
* Mix the MEF and HULEC mixture well before taking the mixture.
6. Make the Matrigel droplet (containing an organoid, MEF, and HULEC) on a sheet of Parafilm.
7. Place the organoid in the center of the droplet by gently pipetting the Matrigel droplet.
8. Repeat the procedure 6-7 to generate 10 droplets.
* Make 5 droplets on each sheet. This generates 10 droplets on 2 sheets.
9. Incubate at 37 °C for 5-10 min to solidify the gel.
10. Remove the droplets from the Parafilm using a fine forceps, put them in a 12-well version of spinning bioreactor containing 2 ml of pre-warmed assembloid medium.
* Put 5-7 droplets in each well of 12-well plate.
11. Culture the droplets (= organoid with stroma) in a spinning bioreactor in 37 °C incubator with 5.0 % CO2 for two days.
* If you don't have a 12-well version of spinning bioreactor, orbital shaker (95 rpm) can be alternatively used.
12. Prepare two sheets of Parafilm at the size of 1.5 cm x 1.5 cm, put them in a 100 mm petri dish.
* Spray your gloves and the Parafilm with 70 % (vol/vol) ethanol.
13. Prepare BSMC and HULEC mixture.
a. Prepare 6 x 105 BSMC and 6 x 105 HULEC, put together in one microcentrifuge tube.
b. Centrifuge at 1,500 rpm, 4 °C, for 3 min.
c. Remove the supernatant, add 20 μl Matrigel to cell pellets (perform on ice), plate on ice
14. Take out the cultures of bladder organoid with stroma from the incubator, take each of them (+ medium that follows when picking the organoid with stroma) using 20p pipette, and put on a sheet of Parafilm.
15. After removing the residual medium from the Parafilm, take 2 μl of BSMC and HULEC mixture using 20p pipette, put it on each of organoid with stroma to make the layered Matrigel droplet.
* Place the organoid with stroma in the center of the droplet by genetly pipetting the Matrigel droplet.
16. Repeat the procedure 14-15 to generate 10 droplets.
* Make 5 droplets on each sheet. This generates 10 droplets on 2 sheets.
17. Incubate at 37 °C for 5-10 min to solidify the gel.
18. Remove the droplets from the Parafilm using a fine forceps, put them in a 12-well version of spinning bioreactor containing 2 ml of pre-warmed assembloid medium.
* Put 5-7 droplets in each well of 12-well plate.
19. Culture the droplets (= assembloids) in a spinning bioreactor in 37 °C incubator with 5.0 % CO2 for seven days
* Medium change: every other day
Generation of human bladder tumour assembloids
* This protocol is standardized to a preparation of culture in 6 wells of 12-well plate (= 30 assembloids)
* A day before, thaw 150 µl of Matrigel overnight at 4 °C.
* Prepare human bladder tumour organoids (~ 1000 organoids at day 10), patient-derived cancer-associated fibroblasts (CAF), HULEC cultures in advance.
1. Prepare six sheets of Parafilm at the size of 1.5 cm x 1.5 cm, put them in a 100 mm petri dish.
* Spray your gloves and the Parafilm with 70 % (vol/vol) ethanol.
2. Prepare patient-derived human bladder tumour organoids.
a. Release the tumour organoids at day 10 from a Matrigel drop (generally contains 1,000 organoids) by physically pipetting the organoid medium and collect them in a new 15 ml tube.
b. Centrifuge at 1,500 rpm, 4 °C, for 5 min.
c. Remove the supernatant, add 1 ml of Advanced DMEM/F12 medium and transfer to a new microcentrifuge tube.
d. Centrifuge at 1,500 rpm, 4 °C, for 5 min.
e. Remove the supernatant, add 200 μl of Advanced DMEM/F12 medium, place on ice.
3. Prepare CAF and HULEC.
a. Prepare 7.5 x 106 CAF and 6 x 105 HULEC.
4. Put CAF and HULEC together in the microcentrifuge tube containing tumour organoids prepared above.
5. Centrifuge at 1,500 rpm, 4 °C, for 3 min.
6. Remove the supernatant, add 150 μl Matrigel and mix well (perform on ice)
7. Take 5 μl of mixture containing tumour organoids, CAF, and HULEC and make the Matrigel droplets on a sheet of Parafilm.
8. Repeat the procedure 7 to generate 30 droplets.
* Make 5 droplets on each sheet. This generates 30 droplets on 6 sheets.
9. Incubate at 37 °C for 5-10 min to solidify the gel.
10. Remove the droplets from the Parafilm using a fine forceps, put them in a 12-well version of spinning bioreactor containing 2 ml of pre-warmed assembloid medium.
* Put 5-7 droplets in each well of 12-well plate.
11. Culture the droplets (= tumour assembloids) in a spinning bioreactor in 37 °C incubator with 5.0 % CO2 for seven days.
* If you don't have a 12-well version of spinning bioreactor, orbital shaker (95 rpm) can be alternatively used.
* Medium change: every other day