[claytonius]

It seems to me that the main advancement here is that the native extracellular matrix is being re-seeded with differentiated stem cells, as opposed to ordinary tissue engineering which uses a manufactured ECM or tissue transplants, which do not involve making stem cells.

There’s still a long way to go before organs can be engineered, even with this tech. We will need much finer control over the delivery of differentiating signal factors for pluripotent stem cells as well as ECM structure.

[riazrizvi]

I thought we already had processes for taking pig organs to use as ECMs (by chemically flushing them of cells) and then reseeding then with a patient’s stem cells? If so then this discovery is about not requiring stem cells, instead they have found a new reliable process to repurpose stomach cells, which are obviously easier to harvest.

[claytonius]

You're right that we could already re-seed decellularized pig ECMs with human stem cells, but we have also already been able to derive stem cells from the stomach. I think the main claim that they're making is that by deriving both the ECM and the Stem cells from the patient, the resulting tissue engineering scaffold is less immunogenic than other methods.

While this is somewhat interesting, they get into trouble by going on to claim that they've been able to generate "functional cardiac, cortical, spinal cord, and adipogenic tissue implants". From what I can see in the paper they saw increased expression of a few markers associated with those cell types and some minor electrical activity, etc.

The idea that differentiating stem cells into vaguely tissue-like phenotypes is equivalent to being able to manufacture organs brings back memories of the shenanigans that went down at UCL a few years ago [1].

1. https://forbetterscience.com/2016/12/21/birchalls-trachea-tr...

[trhway]

>decellularized pig ECMs

why not 3d print the ECMs? Isn't it just basically collagen with some fibrin/laminin thrown into? Do the decellularized ECMs not have any immunogens left? Definitely isn't an issue with the printed ones.

[claytonius]

Unfortunately even with just collagen we can see an immunogenic response that is annoyingly exacerbated by UV cross-linking of the individual collagen proteins. That's why many of the best manufactured ECMs are cross-linked using a mixture of UV exposure and EDC-NHS. Without photolithography i'm not sure you'd be able to get a resolution high enough to mimic native ECM structures.