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Israeli scientists develop tissue implants that won't be rejected

israel21c.org

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Re: Israeli scientists develop tissue implants that won't be rejected

#11

Post by vibrio »

biot wrote: post #7

How does the immune system distinguish between native tissue and foreign tissue?

Many ways you could a semester of immunology on this. High a level there are molecules called MHC (Major Histocompatability Complex), or HLA (Human Leukocyte Antigen). They are very important to the immune system in a number of ways. Any individual has a few sets of these, and there are many different genetic types of these molecules so the differences between any two people can be many. The immune system is even sensitive to their absence, since their down regulation is a strategy for some pathogens such as virus. Anyway, as the name MHC suggests, this is one way that the immune system detects foreign tissue.

Re: Israeli scientists develop tissue implants that won't be rejected

#12

Post by weberc2 »

vibrio wrote: post #11
biot wrote: post #7

How does the immune system distinguish between native tissue and foreign tissue?

Many ways you could a semester of immunology on this. High a level there are molecules called MHC (Major Histocompatability Complex), or HLA (Human Leukocyte Antigen). They are very important to the immune system in a number of ways. Any individual has a few sets of these, and there are many different genetic types of these molecules so the differences between any two people can be many. The immune system is even sen…

Apologies for an unsubstantial comment, but biology blows my mind.

Do we know when these features in our immune system evolved? I assume something this foundational is shared with fish or maybe earlier?

Re: Israeli scientists develop tissue implants that won't be rejected

#15

Post by kmm »

biot wrote: post #7

How does the immune system distinguish between native tissue and foreign tissue?

There are enzymes in cells called proteasomes that degrade intracellular proteins that are damaged, not needed anymore or just old and ready to be replaced. The rest products are peptides, short chains of amino acids, some of which become bound to molecule called the Major Histocompatibility Complex 1, which is then transported to and presented on the surface of the cell. It functions more or less as an ID badge of the cell. Foreign cells, cancerous cells or cells infested by bacteria or viruses will present unknown proteins, which will trigger an immune response.

An obvious solution would be to deactivate the MHC 1 in transplanted foreign tissue, but sadly that wouldn't work because the Natural killer cells in our immune system destroy cells without MHC 1. This is probably an adaption that evolved as bacteria evolved the capability to downregulate MHC 1 molecules to evade detection by other parts of the immune system.

Re: Israeli scientists develop tissue implants that won't be rejected

#16

Post by riazrizvi »

claytonius wrote: post #9

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 differenti…

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.

Re: Israeli scientists develop tissue implants that won't be rejected

#17

Post by claytonius »

riazrizvi wrote: post #16
claytonius wrote: post #9

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 differenti…

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.

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...

Re: Israeli scientists develop tissue implants that won't be rejected

#18

Post by andy-fillebrown »

This is interesting stuff but I don't think the article describes anything groundbreaking. The cells used by the scientists in the article are called adipose-derived stem cells and their applications are already well known in the regenerative medicine industry. See https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3668445

The biologists I develop software with have been talking about adipose-derived stem cells for over a year, so I was hoping the article was going to announce a technological leap in organ manufacturing. It did not.

Re: Israeli scientists develop tissue implants that won't be rejected

#20

Post by azernik »

andy-fillebrown wrote: post #18

This is interesting stuff but I don't think the article describes anything groundbreaking. The cells used by the scientists in the article are called adipose-derived stem cells and their applications are already well known in the regenerative medicine industry. See https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3668445 The biologists I develop software with have been talking about adipose-derived stem cells for over a…

The joys of press releases vs. actual scientific papers.
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