Human heart muscle cells from stem cells

Who it is for

• Pharma and CRO cardiac safety teams that already run hiPSC-CM assays (the FDA-backed CiPA approach checks its predictions in these cells)
• Makers of hiPSC-derived cardiomyocytes and heart-on-a-chip systems who want to show how their models perform in space
• Academic cardiology, cardiac aging and stem-cell labs
• Space agencies and commercial crew programmes studying the cardiovascular risks of spaceflight

What earlier flights found

How LELP-1 runs it

Sample. Commercial or customer hiPSC-derived cardiomyocytes, plated as beating 2D monolayers in a 24-well glass-bottom plate. Optionally, a line that carries a genetically encoded calcium reporter (customer's choice). A 3D engineered-heart-tissue chip is possible only if the customer supplies flight-qualified post-and-sensor hardware. Container. Sealed 24-well glass-bottom cassette (large bay) with gas-permeable lids, connected to the bay fluidics. Reservoirs hold HEPES-buffered maintenance medium, test compound and vehicle, 4% paraformaldehyde and RNA stabilizer, and there is a waste bag. The bay microscope views the cassette from below. Launch. Live, attached and beating at 37 C (late load). Thawing frozen cells in orbit is not recommended. One major supplier (Takara Cellartis) specifies storage at -150 C, the thaw includes a centrifuge step, and cells are ready for use only from day 3 after thawing. Light and gas. Dark except during imaging, when the microscope LED is on for seconds per well. There is no CO2 supply, so the cells use HEPES-buffered medium and gas-permeable lids, with the sealed bay's air headspace supplying oxygen. Medium changes every 2 days keep oxygen and nutrients up and remove lactate.

1. day -10

   Ground: thaw cells and plate them into the flight cassette. Plate the ground-control cassette from the same lot at the same time. Change medium every 2-3 days.

2. day -4

   Ground: switch both cassettes to HEPES-buffered medium. Check that every well beats and record baseline video. Seal the cassettes and close the triple containment.

3. day -1

   Late load into a large bay that is already powered at 37 C. Hold at 37 C through launch.

4. day 0

   Launch. The bay logs temperature, acceleration and dose.

5. day 1

   In orbit: first medium exchange. Record baseline brightfield video of all 24 wells (about 10-20 s each), with no arm motion during recording.

6. day 2

   Daily video of all wells, plus calcium-reporter fluorescence video if a reporter line flies. Repeat every day to day 10.

7. day 3

   Medium exchange (repeat on days 5, 7 and 9).

8. day 5

   Mid-mission preservation: 2 wells into 4% PFA and 2 wells into RNA stabilizer. The bay cools these wells only if they sit in a separate cassette zone. Otherwise they stay at 37 C (see limitations).

9. day 8

   Drug challenge: add the customer's test compound at 2 concentrations, 4 wells each, and vehicle to 4 wells. Record video before dosing and at about 30 min and 2 h after.

10. day 9

    Medium exchange and final full video set. Optionally, the arm carries the bay to the central 40x microscope for close-up images of reporter cells.

11. day 10

    End of lab operations: preserve 6 wells in PFA and 6 wells in RNA stabilizer. Keep the remaining 8 wells live at 37 C.

12. day 11

    Re-entry and splashdown. The bay holds 37 C until handover to the courier on the recovery ship.

The payload module, in CAD

Every item in the module sheet, drawn and packed into the large bay deck by deck. The back face mates with the bay: blind-mate connector, and a cold wall against the bay's thermoelectric block. The front face carries Dexter-L's grapple fixture, and the fluid lines run down a channel just behind it. What you load before launch is marked blue in the configurator's payload guide.

CAD generated by cad/build_modules.py (CadQuery, OpenCascade kernel) from the catalog's module items: concept geometry, not a released design. Standard parts keep their real formats; the rest are sized from their catalog mass. The front panel and grapple fixture are left off in the 3-D view and are in the STEP.

• The XY stage travels 96.5 x 57.9 mm, so every one of the 24 wells reaches the objective; with the stage the imaging stack is 232 x 151 mm, which sets the module's depth budget.
• Reagent volumes the catalog does not state are split evenly from 75 % of the reservoir item's mass. The waste bag holds the spent medium and washes; fixatives and stabilisers stay in the wells and come home.
• Fluid pack: 5 reagent bags in 2 layers (170 x 105 x 45 mm), every port on a front edge.
• The waste bag lies under the reagent bags and fills the room they free: they hold 338 mL, it needs 130 mL.
• The catalog gives 0.98 kg for structure and containment; as an aluminium box that is a 0.48 mm skin on 0.30 kg of posts and shelves. Thin: the bay rails have to carry the launch loads, or the module needs more structure mass.
• The grapple fixture stands 26 mm proud of the front panel, into the bay opening; everything else is inside the bay envelope.

Ground control

Plate a second cassette from the same cell lot on the same day, with the same HEPES medium, reservoirs, gas-permeable lids and fluidics schedule. Run it in an identical bay on the ground, replaying the flight temperature log and the timing of every medium change, image, drug addition and preservation. If possible, also replay the launch and re-entry vibration and acceleration profiles. Give the live ground wells the same courier hold and the same post-flight analysis. Both heritage studies used matched ground controls. This design has no in-flight 1 g centrifuge control.

Coming home

Live wells must stay at 37 C from the bay to the customer's lab. In CRS-20, live tissues were retrieved two days after splashdown and then hand-carried at 37 C and 5% CO2 to the lab, and they were still usable. LELP-1's plan (handover about 20 min after splashdown, then 1-2 days to the lab) is about 25-49 h, which is close to that heritage. It needs a portable 37 C incubator in the courier chain, and we set a target of 48 h or less. PFA-fixed wells should travel at 4 C. RNA-stabilized wells should travel at 4 C and be frozen at -80 C on arrival.

Limits of this flight

• Short exposure. The heritage flights lasted about 30 days (CRS-20) and 5.5 weeks (CRS-9), but a LELP-1 mission lasts 2-14 days and sees only early changes. Force loss and mitochondrial damage may not have time to develop. On CRS-9, the beat rate was similar to ground even after 2.5 weeks.
• No absolute force. Video of 2D monolayers gives beat rate, timing and relative motion, not twitch force. Measuring force needs post-based engineered heart tissues with sensors, which the customer would have to supply and qualify.
• No CO2. The heritage cultures ran at 5% CO2. LELP-1 uses HEPES-buffered medium, so ground controls must use the same medium, and results are not directly comparable with ISS data.
• Cells cannot practically launch frozen. One major supplier specifies storage at -150 C (colder than the -80 C passive cassette), the thaw includes centrifugation, and cells are ready only from day 3. A live late load is therefore needed, which adds work in a lab at the launch site.
• Culture length. The same supplier states cells can be kept for at least 14 days after thawing. This plan needs about 21 days from thaw to splashdown, plus post-flight work. The heritage cultures ran for more than 5 weeks, but the customer must confirm that their line stays stable for that long.
• Beating and calcium kinetics depend strongly on temperature, so any thermal drift in the bay will confound the results.
• All live-return samples carry launch and re-entry loads and 1-2 days at 1 g before reaching the lab. Cells readapt early (on CRS-9, gene expression reverted toward ground-like levels after return), so live-return results are partly recovery data.
• The orbit is 550 km sun-synchronous, so the radiation dose differs from the ISS. Dosimeter data are logged, but radiation and microgravity effects cannot be separated without a 1 g centrifuge control in flight.
• Few replicates per arm (4-8 wells) and possibly only one cell line per bay. Studying donor-to-donor variability, as in the 3-donor CRS-9 design, needs several bays.
• No crew. Nobody can fix a well that stops beating, a bubble or a failed medium exchange.