Characterization of human iPSC-derived sensory neurons and their functional assessment using multi electrode array … – Nature.com

Characterization of the expression of hiPSC-derived sensory neurons

HiPSC-derived sensory neurons (cat #RCDN004N, Reprocell.Inc) were used in this study. To identify characteristics of human iPSC-derived sensory neurons, we confirmed sensory neuron-related genes and proteins expression by real-time PCR and immunocytochemistry (ICC). Real-time PCR shows an increase in Peripherin, Brn3a, TRPV1, TRPM8, Nav1.7, Nav1.8, Piezo2, TRKA, TRKC, TRKB, P2X3, H1R, MrgprX1, CGRP and TAC1 compared with hiPSC cultured 14days in vitro (DIV) (Fig.1). The nociceptor phenotype consists of A-fibers, and C-fibers. C-fibers respond to both peptidergic and non-peptidergic neurotransmitters. HiPSC-derived sensory neurons expressed TRKA (nociceptor marker), IB4 (A-fibers marker), CGRP and TAC1 (peptidergic neurotransmitters) and P2X3 (ATP (non-peptidergic neurotransmitter) receptor) (Figs. 1i,l,o,p and 2k). Furthermore, TRPV1, TRPM8, Nav1.7 and Nav1.8 which are nociceptors receptors were also expressed (Fig.1c,eg). TRPV1 is known to be activated by capsaicin and noxious heat (43C)14. TRPM8 is known to be activated by menthol, noxious (<15C) and non-noxious (2815C) heat15,16. Nav1.7 and Nav1.8 are known to be subtype of voltage-gated sodium channels which is preferentially expressed in nociceptors17,18,19. The mechanoreceptor phenotype consists of relatively large diameter cells that are A-fibers. HiPSC-derived sensory neurons expressed TRKB (mechanoreceptor marker), NF200 (A-fibers marker), TRPM8 and Piezo2 (mechanoreceptor receptors) (Figs. 1e,h,j and 2j)4. TRKC, a proprioceptor marker was expressed in hiPSC-derived sensory neurons (Fig.1k). Thus, these data suggests that the hiPSC-derived sensory neurons generated constitute a heterogeneous population of sensory neuronal subclasses. The expression of TRPA1 in hiPSC-derived sensory neurons was lower than the one in hiPSC (Fig.1d). The expression levels of Brn3a, TRPM8, TRKB and MrgprX1 in hiPSC-derived sensory neurons were comparable to those in human DRG, whereas the others were lower than in hDRG. The reason some genes of hiPSC-derived sensory neurons showed lower expression than hDRG might be due to the immature nature of the hiPSC-derived sensory neurons20. Although we cultured them for a long time, the expression levels of Peripherin, TRPV1, TRPA1, Nav1.7, Nav1.8, H1R, and CGRP were not comparable to the ones in hDRG (Supplementary Fig. S1). Therefore, we confirmed proteins expression by ICC.

Expression of sensory neuron related genes in hiPSC, hiPSC-derived sensory neurons and human DRG. Real-time PCR showed expression of (a) Peripherin, (b) Brn3a, (c) TRPV1, (d) TRPA1, (e) TRPM8, (f) Nav1.7, (g) Nav1.8, (h) Piezo2, (i) TRKA, (j) TRKB, (k) TRKC, (l) P2X3, (m) H1R, (n) MrgprX1, (o) CGRP, (p)TAC1. The square marker, the circle marker and triangle marker indicate expression of genes in hiPSC, hiPSC-derived sensory neurons and human DRG respectively. Three different lot of hiPSC-derived sensory neurons were examined. The line marker represents the mean expression of genes in hiPSC-derived sensory neurons.

Expression of sensory neuron related proteins in hiPSC-derived sensory neurons and their morphology. The cells are stained for (a) TUBB3, (b) Peripherin, (c) Brn3a, (d) TRPV1, (e) TRPM8, (f) Nav1.7, (g) TRKA, (h) TRKB, (i) TRKC, (j) NF200, (k) IB4. DAPI stain of nuclei is shown in blue. (l) Image of iPSC-derived sensory neurons which exhibit a bipolar (red arrowhead), pseudounipolar (yellow arrowhead), or multipolar morphology (green arrowhead). Scale bar represents 50m.

ICC showed expression of TUBB3 (mature neuron marker), Peripherin (peripheral neuron marker) and Brn3a (sensory neuron marker) at 14 DIV (Fig.2ac). TRPV1, TRPM8, Nav1.7, TRKA, TRKB and TRKC were expressed at the membrane (Fig.2di). Since TRPV1, and TRPM8 are receptors of noxious and non-noxious stimulation and are expressed at the membrane, we expected them to be available for characterizing their function using MEA (Fig.2d,e). NF200, a A-fibers marker, was expressed at a higher-intensity in relatively large diameter cells than small diameter cells (Fig.2j). Although adult human DRG do not bind IB4 which is a non-peptidergic C-fibers marker, it was expressed in hiPSC-derived sensory neurons (Fig.2k)21. The research showed expression of IB4 in prenatal human DRG at 8-month of gestation22. This data suggests that hiPSC-derived sensory neurons might be immature.

It is known that when observing rat DRG cells in the early stages of development, their morphology changes from bipolar cells to pseudounipolar cells23. Our hiPSC-derived sensory neurons exhibit a bipolar, pseudounipolar and multipolar morphology (Fig.2l). A majority of the hiPSC-derived sensory neurons were bipolar neurons. This image suggests that our hiPSC-derived sensory neurons contained neurons with different degrees of maturity.

Taken together, hiPSC-derived sensory neurons express sensory neuron-related genes and proteins. They constitute a heterogeneous population of nociceptors, mechanoreceptors, and proprioceptors, and they differ in maturity. Thus, we proceeded to characterize their function next.

We confirmed whether hiPSC-derived sensory neurons responded to capsaicin, menthol, noxious heat (4346C), which are noxious stimuli, and bradykinin, and non-noxious heat (3742C), which is a non-noxious stimulus14,15,16,24. Sensory neurons of DRG are used as in vitro model of nociceptive response. DRG responded to 10nM, 100nM, 1M capsaicin25,26. We measured and compared data before and after drug treatment (Fig.3a). We measured the response to treatment with 100nM capsaicin which resulted in increase in Mean Firing Rate (MFR) and Number of Bursts (NOB), whereas vehicle treatment had no effect on them (Fig.3d,e). Capsaicin-evoked activity is known to be rapid in DRG25. This result showed that neural activity was evoked within 10s after treatment with capsaicin in hiPSC-derived sensory neurons as well (Fig.3b). To determine whether capsaicin-evoked neuronal activity is characteristic of hiPSC-derived sensory neuron, we treated with 100nM capsaicin in hiPSC-derived cortical neurons. As a result, hiPSC-derived cortical neurons did not respond to capsaicin (Fig.3ce). Moreover, we added 100nM AMG9810 which is a TRPV1 antagonist for 60min before treating with capsaicin. A response to capsaicin was not observed in the presence of AMG9810 (Fig. S2a,b). These data suggest that capsaicin-evoked activity occurred via TRPV1 in iPSC-derived sensory neurons. Thus, we can conclude that hiPSC-derived sensory neurons specifically respond to noxious stimulus and could be used in functional assays using MEA.

Capsaicin and menthol responsiveness using MEA. (a) Timeline of drug treatment. Baseline and dose response were recorded for 60s when treating with capsaicin or menthol. Capsaicin experiment raster plots of (b) hiPSC-derived sensory neurons and (c) hiPSC-derived cortical neurons. The triangle marker indicates the time of capsaicin addition. (d, h) Mean Firing Rate normalized to the control. Control firing rate is calculated as firing rate before adding vehicle or drug. (e, i) Number of Bursts normalized to the control. Menthol experiment raster plot of (f) hiPSC-derived sensory neurons and (g) hiPSC-derived cortical neurons. n=3 wells.

Menthol activates TRPM8 which is a nociceptive receptor. Since mouse and rat DRG respond to 10M and 100M menthol, we decided to treat with the same concentrations26,27. The high concentration of menthol resulted in suppressing spontaneous neural activity (Supplementary Fig. S3). This may be due in part to the higher expression of TRPM8 in hiPSC-derived sensory neurons than in human DRG (Fig.1e, Supplementary Fig. S1e). Treatment with 100nM menthol resulted in an increase in MFR and NOB in hiPSC-derived sensory neurons whereas hiPSC-derived cortical neurons did not respond to menthol (Fig.3fi). The data show that menthol got a response from nociceptive-like and non-nociceptive-like DRG neurons28. Since our hiPSC-derived sensory neurons responded to menthol, they may also include functionally non-nociceptive like neurons.

Bradykinin activates nociceptors and causes pain,24. Treatment with 100nM bradykinin resulted in significant increase in MFR and NOB compared to vehicle treatment for 60s (n=3, p<0.05) (Fig.4ac). In contrast to capsaicin and menthol, the onset of bradykinin-evoked neural activity was relatively long (Figs. 3b,f and 4a). Bradykinin-evoked activity increased gradually and reached its mean peak at 60s in DRG25. However, hiPSC-derived sensory neurons were able to respond faster than DRG, because they also responded to an additional stimulation which immediately activated them when bradykinin and vehicle were added against the well of the MEA plate. There is expression of TRKB and Piezo2 relevant to touch sensation in hiPSC-derived sensory neurons, explaining why they may have responded to an additional stimulation.

Bradykinin responsiveness. (a) Bradykinin experiment raster plot of hiPSC-derived sensory neurons. The triangle marker indicates the time of bradykinin addition. (b) Mean Firing Rate after addition of Bradykinin normalized to firing rate before addition of Bradykinin. (c) Number of Bursts after addition of Bradykinin normalized to number of bursts before addition of Bradykinin. n=3 wells, *p<0.05.

MFR were observed to increase gradually in DRG, when temperature increases from 37 to 42C via the stage plate heater, part of the recording system25. We increased the temperature from 37 to 46C via MAESTROs system to confirm responsiveness to noxious heat and non-noxious heat. We observed that MFR and NOB increased gradually and reached their mean peak at 45C and 46C respectively, in hiPSC-derived sensory neurons (Fig.5). In the presence of TRPV1 antagonist, AMG9810, MFR were lower than that of vehicle at 4346C (Fig. S2c,d). Because TRPV1 is known to be activated by noxious heat (43C), these results suggest that TRPV1 may contribute to the response to 4346C in iPSC-derived sensory neurons. The relative levels of MFR (1.540.046) and NOB (1.620.01) at 41C, which is non-noxious heat, were significantly higher than those at 37C. However, MFR decreased gradually in hiPSC-derived cortical neurons with an increase in temperature (Fig.5b,c).

Temperature responsiveness. Raster plots of (a) hiPSC-derived sensory neurons and (b) hiPSC-derived cortical neurons when the temperature is gradually increased from 37 to 46C. (c) Mean Firing Rate normalized to the firing rate at 37C. (d) Number of Bursts normalized to the number of bursts at 37C. The data for the number of bursts in hiPSC-derived cortical neurons isnt shown because one of the three wells didnt produce any burst. n=3 wells, *p<0.05, **p<0.01 compared with the corresponding value at 37C. Functional assessment of hiPSC-derived sensory neurons against itching stimuli

These data suggest that the observed and recorded response is specific to sensory neurons and the hiPSC-derived sensory neuron populations generated in this study are likely to include nociceptors that respond to noxious stimuli like capsaicin, menthol, bradykinin, and noxious heat (43C) and to include mechanoreceptors that respond to non-noxious stimuli (41C).

Atopic dermatitis (AD) is the most common chronic skin disease which causes a global disease burden29. AD causes itch (pruritus) and poor non-health-based quality-of-life. It is known that itch occurs via C-fiber in nociceptors30. Recently, investigating itch has been established by using human sensory neurons from stem and other progenitor cells as in vitro model31. Although substances causing itch treat to their cells, their inhibitors effect arent confirmed using hiPSC-derived sensory neurons. Because we demonstrated that our hiPSC-derived sensory neurons expressed nociceptor genes and proteins, and responded to noxious stimuli, we expected that they also responded to an itch stimulus and its inhibitor.

Histamine is one of the substances that cause itching via C-fiber. The histamine receptor is a four G protein-coupled receptor. Histamine H1 receptor (H1R) is involved in the induction of histamine-induced pruritus32. Since we confirmed that the H1R gene is expressed, we examined whether hiPSC-derived sensory neurons respond to histamine, using MEA. Mouse DRG responded to 100M Histamine, as described in the literature33. HiPSC-derived sensory neurons didnt respond to 100M Histamine but responded to 1mM Histamine (Supplementary Fig. S3df and Fig.6a,b). The MFR gradually increased and reached its mean peak at 25min. Pyrilamine is a histamine H1 receptor inverse agonist. We treated the sensory neuron population with 10M Pyrilamine for 60min before adding Histamine. As a result, Pyrilamine inhibited Histamine-evoked activity (Fig.6a,b). These results suggest that Histamine-evoked activity occurred via H1R in iPSC-derived sensory neurons.

Histamine, H1R inhibitor, pyrilamine and chloroquine responsiveness. (a) The left raster plots have been recorded before histamine addition. The right raster plots have been recorded 25min after histamine addition. Upper raster plots are recorded in pyrilamine absence. Lower raster plots are recorded with presence of pyrilamine. (b, e) Mean Firing Rate normalized to firing rate before drug addition. Raster plots of (c) before chloroquine addition and (d) 5min after chloroquine addition. The experiment with histamine and pyrilamine was performed with n=2 wells each. Experiment with chloroquine was performed with n=3 wells. *p<0.05, **p<0.01 compared with the value recorded before addition or with vehicle.

Chloroquine is a drug that has been used in the treatment to prevent malaria. Histamine-independent pruritus is known to be one of the side effects of chloroquine34. Mrgprs are receptors of chloroquine and are activated by it35. Since we confirmed expression of human MrgprX1 by real-time PCR, we investigated the potential response of hiPSC-derived sensory neurons by chloroquine. DRG are reported to respond to 1mM chloroquine, however the MFR gradually decreased at the same concentration in hiPSC-derived sensory neurons (Supplementary Fig. S3g,h)36. 1M chloroquine increased the MFR and reached the mean peak after 5min of incubation (Fig.6ce). The mean peak after stimulation with chloroquine was reached faster than after stimulation with histamine.

These data showed an example of the effect of an itch inhibitor and different responses between itch inducing drugs. HiPSC-derived sensory neurons may be available for drug discovery against AD.

Nav1.7 subtype of voltage-gated sodium channels is expressed in DRG. Mutations in the gene encoding Nav1.7 are associated with either absence of pain or with exacerbation of pain. Recently, Nav1.7 has been an attractive target to pursue treating pain. ProTx-II is a tarantula venom peptide that preferentially inhibits Nav1.7 over other Nav subtypes37. It suppressed spontaneous neural activity in a time dependent manner in hiPSC-derived sensory neurons (Fig.7ae). The MFR and NOB are significantly diminished after 35min of incubation with 1M ProTx-II (Fig.7d,e). After washing out ProTx-II, the suppressed neural activity gradually recovered. Although, responses was completely blocked by 300nM ProTx-II in rodent DRG, the responses in hiPSC-derived sensory neurons were not blocked at the same concentration38. This may be due in part to the lower expression of Nav1.7 in hiPSC-derived sensory neurons than in human DRG.

Nav1.7 channels inhibitor, ProTx-II and Nav1.7 inhibitor responsiveness. Raster plots of (a) before ProTx-II addition (baseline), (b) 35min after adding ProTx-II and (c) 150min after washing ProTx-II, respectively. (d, i) Mean Firing Rate and (e, j) Number of Bursts normalized to mean firing rate and number of bursts before drug addition. Raster plots of (f) before Nav1.7 inhibitor addition (baseline), (b) 50min after adding Nav1.7 inhibitor and (c) 30min after washing Nav1.7 inhibitor, respectively. n=3 wells, *p<0.05, **p<0.01, ***p<0.001 compared to the value recorded before drug addition.

ProTx-II is known to act not only as a Nav1.7 inhibitor but also to act on Nav1.5 channels and on some T-Type Ca2+ channels39,40. Thus we administered a small molecule inhibitor that is more selective for Nav1.741. Although 300nM of a more selective Nav1.7 inhibitor suppressed MFR and NOB in a time dependent manner in hiPSC-derived sensory neurons, the degree of decrease was lower than that of ProTx-II (Fig.7fj). After washing it out, the suppression of the neural activity was lifted.

These results suggested that hiPSC-derived sensory neurons may serve as a drug screening tool for pain.

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Imaging cAMP nanodomains in human iPSC-derived cardiomyocytes – Nature.com

Cardiac activity is regulated by the -adrenergic pathway. The activation of this pathway triggers a cellular signalling cascade that increases the production of cAMP, a cyclic nucleotide that activates the enzyme protein kinase A (PKA). PKA phosphorylates key proteins involved in cellular contraction, but can also phosphorylate a multitude of other proteins with different functions. To achieve specific effects, cAMP is confined in nanoscale subcellular domains (nanodomains) close to PKA and its targets. The maintenance and regulation of these nanodomains are central to functional signal transduction, and their dysregulation can result in diseases such as heart failure.

I use this technique in human induced pluripotent stem cell (iPSC)-derived cardiomyocytes to study how the maturation of these cells is affected by a newly identified cAMP nanodomain found at gap junctions, which regulate the communication between adjacent cardiomyocytes. To understand the role of the gap junction-associated cAMP nanodomain in human iPSC-derived cardiomyocytes, endogenous levels of protein expression must be maintained to avoid interference with their maturation process. This technique can more broadly be used to study cAMP nanodomains in which overexpression of the target protein might impair cell physiology. This tool will provide unique insights into the processes involved in human iPSC-derived cardiomyocyte maturation and can also be used to identify new targets in the -adrenergic pathway that might be relevant for the treatment of diseases, such as heart failure.

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Imaging cAMP nanodomains in human iPSC-derived cardiomyocytes - Nature.com

Colossal Creates Elephant Stem Cells for the First Time in Quest to Revive the Woolly Mammoth – Singularity Hub

The last woolly mammoth roamed the vast arctic tundra 4,000 years ago. Their genes still live on in a majestic animal todaythe Asian elephant.

With 99.6 percent similarity in their genetic makeup, Asian elephants are the perfect starting point for a bold plan to bring the mammothor something close to itback from extinction. The project, launched by biotechnology company Colossal in 2021, raised eyebrows for its moonshot goal.

The overall playbook sounds straightforward.

The first step is to sequence and compare the genomes of mammoth and elephant. Next, scientists will identify the genes behind the physical traitslong hair, fatty depositsthat allowed mammoths to thrive in freezing temperatures and then insert them into elephant cells using gene editing. Finally, the team will transfer the nucleuswhich houses DNAfrom the edited cells into an elephant egg and implant the embryo into a surrogate.

The problem? Asian elephants are endangered, and their cellsespecially eggsare hard to come by.

Last week, the company reported a major workaround. For the first time, they transformed elephant skin cells into stem cells, each with the potential to become any cell or tissue in the body.

The advance makes it easier to validate gene editing results in the lab before committing to a potential pregnancywhich lasts up to 22 months for elephants. Scientists could, for example, coax the engineered elephant stem cells to become hair cells and test for gene edits that give the mammoth its iconic thick, warm coat.

These induced pluripotent stem cells, or iPSCs, have been especially hard to make from elephant cells. The animals are a very special species and we have only just begun to scratch the surface of their fundamental biology, said Dr. Eriona Hysolli, who heads up biosciences at Colossal, in a press release.

Because the approach only needs a skin sample from an Asian elephant, it goes a long way to protecting the endangered species. The technology could also support conservation for living elephants by providing breeding programs with artificial eggs made from skin cells.

Elephants might get the hardest to reprogram prize, said Dr. George Church, a Harvard geneticist and Colossal cofounder, but learning how to do it anyway will help many other studies, especially on endangered species.

Nearly two decades ago, Japanese biologist Dr. Shinya Yamanaka revolutionized biology by restoring mature cells to a stem cell-like state.

First demonstrated in mice, the Nobel Prize-winning technique requires only four proteins, together called the Yamanaka factors. The reprogrammed cells, often derived from skin cells, can develop into a range of tissues with further chemical guidance.

Induced pluripotent stem cells (iPSCs), as theyre called, have transformed biology. Theyre critical to the process of building brain organoidsminiature balls of neurons that spark with activityand can be coaxed into egg cells or models of early human embryos.

The technology is well-established for mice and humans. Not so for elephants. In the past, a multitude of attempts to generate elephant iPSCs have not been fruitful, said Hysolli.

Most elephant cells died when treated with the standard recipe. Others turned into zombie senescent cellsliving but unable to perform their usual biological functionsor had little change from their original identity.

Further sleuthing found the culprit: A protein called TP53. Known for its ability to fight off cancer, the protein is often dubbed the genetic gatekeeper. When the gene for TP53 is turned on, the protein urges pre-cancerous cells to self-destruct without harming their neighbors.

Unfortunately, TP53 also hinders iPSC reprogramming. Some of the Yamanaka factors mimic the first stages of cancer growth which could cause edited cells to self-destruct. Elephants have a hefty 29 copies of the protector gene. Together, they could easily squash cells with mutated DNA, including those that have had their genes edited.

We knew p53 was going to be a big deal, Church told the New York Times.

To get around the gatekeeper, the team devised a chemical cocktail to inhibit TP53 production. With a subsequent dose of the reprogramming factors, they were able to make the first elephant iPSCs out of skin cells.

A series of tests showed the transformed cells looked and behaved as expected. They had genes and protein markers often seen in stem cells. When allowed to further develop into a cluster of cells, they formed a three-layered structure critical for early embryo development.

Weve been really waiting for these things desperately, Church told Nature. The team published their results, which have not yet been peer-reviewed, on the preprint server bioRxiv.

The companys current playbook for bringing back the mammoth relies on cloning technologies, not iPSCs.

But the cells are valuable as proxies for elephant egg cells or even embryos, allowing the scientists to continue their work without harming endangered animals.

They may, for example, transform the new stem cells into egg or sperm cellsa feat so far only achieved in micefor further genetic editing. Another idea is to directly transform them into embryo-like structures equipped with mammoth genes.

The company is also looking into developing artificial wombs to help nurture any edited embryos and potentially bring them to term. In 2017, an artificial womb gave birth to a healthy lamb, and artificial wombs are now moving towards human trials. These systems would lessen the need for elephant surrogates and avoid putting their natural reproductive cycles at risk.

As the study is a preprint, its results havent yet been vetted by other experts in the field. Many questions remain. For example, do the reprogrammed cells maintain their stem cell status? Can they be transformed into multiple tissue types on demand?

Reviving the mammoth is Colossals ultimate goal. But Dr. Vincent Lynch at the University of Buffalo, who has long tried to make iPSCs from elephants, thinks the results could have a broader reach.

Elephants are remarkably resistant to cancer. No one knows why. Because the studys iPSCs are stripped of TP53, a cancer-protective gene, they could help scientists identify the genetic code that allows elephants to fight tumors and potentially inspire new treatments for us as well.

Next, the team hopes to recreate mammoth traitssuch as long hair and fatty depositsin cell and animal models made from gene-edited elephant cells. If all goes well, theyll employ a technique like the one used to clone Dolly the sheep to birth the first calves.

Whether these animals can be called mammoths is still up for debate. Their genome wont exactly match the extinct species. Further, animal biology and behavior strongly depend on interactions with the environment. Our climate has changed dramatically since mammoths went extinct 4,000 years ago. The Arctic tundratheir old homeis rapidly melting. Can the resurrected animals adjust to an environment they werent adapted to roam?

Animals also learn from each other. Without a living mammoth to show a calf how to be a mammoth in its natural habitat, it may adopt a completely different set of behaviors.

Colossal has a general plan to tackle these difficult questions. In the meantime, the work will help the project make headway without putting elephants at risk, according to Church.

This is a momentous step, said Ben Lamm, cofounder and CEO of Colossal. Each step brings us closer to our long-term goals of bringing back this iconic species.

Image Credit: Colossal Biosciences

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Colossal Creates Elephant Stem Cells for the First Time in Quest to Revive the Woolly Mammoth - Singularity Hub

How stem cells might be used in planned de-extinction of woolly mammoth – Cosmos

Sometimes it takes the smallest thing to undertake a mammoth task.

Thats what researchers behind the attempts to de-extinct the woolly mammoth are hoping as they announced what they believe to be a step forward in their efforts.

One Texas-based company has made de-extinction its business. It is looking at not only de-extinction of the woolly mammoth, but also dodos and Australias thylacine both hunted to extinction within the last 500 years.

The key is an announcement this week from researchers with Colossal Biosciences who say theyve derived induced pluripotent stem cells (iPSCs) from Asian elephants (Elephas maximus).

These iPSCs are reprogrammed to be able to give rise to any cell type in the body.

It means the researchers might be able to investigate the genetic differences between the woolly mammoth (Mammathus primigenius) and their closest living relatives the Asian elephant. They can also test gene edits without needing tissue from living animals.

Woolly mammoths roamed Earth for nearly 800,000 years.

They diversified from the steppe mammoth (Mammuthus trogontherii) at the beginning of the Middle Pleistocene (770,000126,000 years ago). They were closely related to the North American Columbian mammoth (Mammathus columbi) and DNA studies show they occasionally interbred.

Woolly mammoths were up to 3.5 metres tall at the shoulder and could weigh as much as 8 metric tons. (By contrast the Asian elephant is 2-3m and weights up to 5t.)

Mammoths are synonymous with the last Ice Age which ended about 12,000 years ago. Its believed that a combination of a warming climate and human hunting saw woolly mammoth numbers decline.

They died out so recently that some mammoth bodies have been recovered extremely well preserved in ice and snow.

The last stronghold of the woolly mammoth was the Siberian island of Wrangel where they lived until as recently as 4,000 years ago.

When these last mammoths died, the Great Pyramids of Giza were already 600 years old. Stonehenge had been around for 1,000 years and Sumerian poets had begun compiling the works that would over the next 800 years be brought together into the Epic of Gilgamesh.

In the great scheme of geological time, we are tantalisingly close to these remarkable creatures.

The successful formation of Asian elephant iPSCs in the lab is critical to understanding how the woolly mammoths genetic code sets it apart from its modern counterparts.

Which bits of DNA come together to produce features like their shaggy hair, curved tusks, fat deposits and dome skulls? These are the kinds of questions scientists at Colossal now feel they can answer.

It is also possible that the iPSCs can lead to producing elephant sperm and egg cells in the lab. Anyone whos had the birds and the bees chat doesnt need to be told why thats important in de-extinction.

Being able to create these cells in a lab is particularly important given the precariousness of Asian elephant populations.

Fewer than 50,000 Asian elephants remain in the wild according to the World Wildlife Fund. They are listed as endangered on the IUCNs Red List. Attempts to retrieve egg and sperm cells from Asian elephants would be difficult and potentially adverse.

Making elephant iPSCs has been so difficult because of complex gene pathways unique to these animals. Colossals genetic engineers overcame this by suppressing core genes called TP53 which regulate cell growth and halt the duplicating process.

But the work doesnt stop.

Theyre still looking at alternative methods to create iPSCs and maturing the ones theyve already made.

Theres also a lot still to learn about the complex 22-month gestation period of elephants if a healthy woolly mammoth calf is to be produced through in vitro fertilisation of a modern elephant.

Colossals plan is to have a living, breathing woolly mammoth by 2028.

For that to happen, the company is also looking into restoring suitable tundra steppe habitats in Canada and the US where the reborn mammoth population can settle.

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How stem cells might be used in planned de-extinction of woolly mammoth - Cosmos

The long and winding road of reprogramming-induced rejuvenation – Nature.com

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Continued here:
The long and winding road of reprogramming-induced rejuvenation - Nature.com

Looking for the Path to Safe Cell Rejuvenation – Lifespan.io News

In Nature Communications, Ali Ycel and Vadim Gladyshev have published a review of the current state of the art in partial cellular reprogramming, detailing what this technology does and how it might be used safely.

This paper begins by treading familiar ground on the subject, explaining its end goals and purpose. When successful, partial cellular reprogramming induces reprogramming-induced rejuvenation (RIR), a state in which a cell is transformed into an epigenetically younger cell of the same type and fulfilling the same function [1]. This process has had multiple crucial successes in experimental models, including human muscle cells [2] and skin cells [3] along with restoring vision [4] and extending lifespan [5] in mice.

Much of this work has been done in mice that have been genetically modified to express the necessary factors when doxycycline is administered. This has even been accomplished after birth via an adeno-associated virus (AAV) [5]. While there are four Yamanaka factors, OSKM, the fourth, c-Myc, is often omitted because it raises the risk of cancer. OSK administration significantly reduced the frailty of the treated mice.

As the authors note, applying these sorts of genetic modification techniques directly to human beings is currently infeasible with existing technologies. Partial reprogramming requires carefully determined generation of Yamanaka factors inside cells. To apply this in a clinical setting would require gene therapy that has specific and strong effects on individual tissues, and using the AAV system that works on mice is not yet practical for people [6]. Generating partially reprogrammed cells outside the body, similarly to how induced pluripotent stem cells (iPSCs) are generated, may be feasible for therapeutic purposes.

Administering small molecules to people in order to effect rejuvenation in the form of a drug has been the dream of aging researchers for some time. Previous work has spurred the creation of iPSCs through such chemical means [7]. The authors of this review describe these methods as less powerful than gene therapy and requiring multiple stages of administration. This implies a degree of safety and control that makes them more attractive for human research.

An experiment on mouse cells, which also included Vadim Gladyshev, had revealed that using a 7c cocktail reduced multiple aspects of aging, including epigenetic clock measurements, age-related metabolic changes, and oxidative stress markers [8]. However, it also upregulates the senescence-associated p53 pathway, which is downregulated through normal reprogramming methods and may cause cells to become senescent earlier [9].

Normally, constant expression of the Yamanaka factors in a living organism causes its cells to completely revert to a pluripotent state, in which they forget their roles, become cancerous, and cause the organism to die. For example, inducing OSKM for six days in the hearts of mice was found to be beneficial for them, while extending it for a dozen days proved lethal [10]. However, constantly inducing OSK in neural ganglion cells for a full 10-18 months improved vision without this side effect [4].

The authors note many of the aspects of aging that are improved or possibly improved with RIR, of which the most obvious, epigenetic alterations, is only one. Inflammation and proteostasis are also affected. Telomere attrition, however, occurs only in later reprogramming and is not affected by the partial variety [11]. Direct changes to cellular communication and genomic stability are not yet known.

However, the authors point out that, while full reprogramming does not cells to mutate, creating colonies of iPSCs causes evolutionary pressure: cells with mutations that may not be beneficial for the whole organism may be more prevalent in iPSC colonies [12]. It remains to be seen if this is a concern for partial reprogramming.

The authors also mention a biochemical pluripotency network and the fundamental differences between full and partial rejuvenation. Most critically, they hold that partial reprogramming is caused by factors that are downstream of full reprogramming. If it is possible to directly affect these factors instead of relying on the Yamanaka full-reprogramming factors, it might be possible to cause RIR without risking the dangerous side effects associated with complete reprogramming. However, this area of research remains unexplored.

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[1] Ocampo, A., Reddy, P., Martinez-Redondo, P., Platero-Luengo, A., Hatanaka, F., Hishida, T., & Belmonte, J. C. I. (2016). In vivo amelioration of age-associated hallmarks by partial reprogramming. Cell, 167(7), 1719-1733.

[2] Sarkar, T. J., Quarta, M., Mukherjee, S., Colville, A., Paine, P., Doan, L., & Sebastiano, V. (2020). Transient non-integrative expression of nuclear reprogramming factors promotes multifaceted amelioration of aging in human cells. Nature communications, 11(1), 1545.

[3] Gill, D., Parry, A., Santos, F., Okkenhaug, H., Todd, C. D., Hernando-Herraez, I., & Reik, W. (2022). Multi-omic rejuvenation of human cells by maturation phase transient reprogramming. Elife, 11, e71624.

[4] Lu, Y., Brommer, B., Tian, X., Krishnan, A., Meer, M., Wang, C., & Sinclair, D. A. (2020). Reprogramming to recover youthful epigenetic information and restore vision. Nature, 588(7836), 124-129.

[5] Macip, C. C., Hasan, R., Hoznek, V., Kim, J., Lu, Y. R., Metzger IV, L. E., & Davidsohn, N. (2024). Gene Therapy-Mediated Partial Reprogramming Extends Lifespan and Reverses Age-Related Changes in Aged Mice. Cellular Reprogramming, 26(1), 24-32.

[6] Pupo, A., Fernndez, A., Low, S. H., Franois, A., Surez-Amarn, L., & Samulski, R. J. (2022). AAV vectors: The Rubiks cube of human gene therapy. Molecular Therapy.

[7] Guan, J., Wang, G., Wang, J., Zhang, Z., Fu, Y., Cheng, L., & Deng, H. (2022). Chemical reprogramming of human somatic cells to pluripotent stem cells. Nature, 605(7909), 325-331.

[8] Mitchell, W., Goeminne, L. J., Tyshkovskiy, A., Zhang, S., Chen, J. Y., Paulo, J. A., & Gladyshev, V. N. (2023). Multi-omics characterization of partial chemical reprogramming reveals evidence of cell rejuvenation. bioRxiv, 2023-06.

[9] Tyner, S. D., Venkatachalam, S., Choi, J., Jones, S., Ghebranious, N., Igelmann, H., & Donehower, L. A. (2002). p53 mutant mice that display early ageing-associated phenotypes. Nature, 415(6867), 45-53.

[10] Chen, Y., Lttmann, F. F., Schoger, E., Schler, H. R., Zelarayn, L. C., Kim, K. P., & Braun, T. (2021). Reversible reprogramming of cardiomyocytes to a fetal state drives heart regeneration in mice. Science, 373(6562), 1537-1540.

[11] Takahashi, K., & Yamanaka, S. (2006). Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. cell, 126(4), 663-676.

[12] Kosanke, M., Osetek, K., Haase, A., Wiehlmann, L., Davenport, C., Schwarzer, A., & Martin, U. (2021). Reprogramming enriches for somatic cell clones with small-scale mutations in cancer-associated genes. Molecular Therapy, 29(8), 2535-2553.

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Looking for the Path to Safe Cell Rejuvenation - Lifespan.io News

Company Trying to Resurrect a Mammoth Makes a Stem Cell Breakthrough – Gizmodo

Colossal Biosciences, which calls itself the worlds first de-extinction company, has created stem cells it thinks will hasten the companys marquee goal of resurrecting the woolly mammoth. The teams research describing the accomplishment will be hosted on the preprint server bioRxiv.

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The cells are induced pluripotent stem cells (iPSC), a type of cell that can be reprogrammed to develop into any other type of cell. The cells are especially useful in bioengineering, for their applications in cell development, therapy, and transferring genetic information across species. Colossals new iPSCs are the first engineered elephant cells converted into an embryonic state, a useful development if youre in pursuit of a woolly mammoth. Or rather, an animal that looks like a woolly mammoth.

In the past, a multitude of attempts to generate elephant iPSCs have not been fruitful. Elephants are a very special species and we have only just begun to scratch the surface of their fundamental biology, said Eriona Hysolli, who heads up Colossals biological sciences team, in a statement. The Colossal mammoth team persisted quite successfully as this progress is invaluable for the future of elephant assisted reproductive technologies as well as advanced cellular modeling of mammoth phenotypes.

According to the Colossal release, the new stem cells were able to differentiate into the three germ layers that result in every cell type. It opens the door to establishing connections between genes and traits for both modern and extinct relativesincluding resistance to environmental extremes and pathogens, said George Church, a geneticist and co-founder of Colossal, in a press release.

The animals Colossal hopes to produce will be Asian elephants (E. maximus), genetically engineered to be resistant to the cold and, most notably, covered in shaggy hair la woolly mammoth, their extinct cousin. Colossal also has plans to produce approximate (or proxy) species of the Tasmanian tiger or thylacine, which went extinct around 1936, and the dodo, a flightless bird native to Mauritius, which was gone by 1681. Other companiesnamely Revive & Restorehave similar aims with other species, including the heath hen and passenger pigeon.

A proxy species isnt truly the old creature brought back to life. As described in a 2016 report by the International Union for Conservation of Natures Species Survival Commission, Proxy is used here to mean a substitute that would represent in some sense (e.g. phenotypically, behaviourally, ecologically) another entity the extinct form. The group added that Proxy is preferred to facsimile, which implies creation of an exact copy.

One expert who spoke to Gizmodo previously referred to the end-goals of these companies as something out of Lovecraft and the elephantine effort as a simulacrum that has no phylogenetic relationship with actual mammoths.

Its not just a question of having biological material from an extinct animal. Researchers exploring the possibility of resurrecting the Christmas Island rat found that some genetics were simply lost to time, in spite of the amount that could be gleaned from historic tissues and its nearest extant relatives. One member of the team told Gizmodo that We arent actually planning to do it, as probably the world doesnt need any more rats, and probably the money it would take to do the best job possible could be spent on better things, e.g., conserving living things. (That researcher is now a member of Colossals advisory board.) Nevertheless, the production of elephant iPSCs is a step toward producing these proxy animals, an aim that many scientists see as likely but fewer see as useful.

Once Colossal produces a herd of proxy mammoths, its intention is to decelerate the melting of the permafrost by loosing the animals on a swath of Siberia. Ultimately, Colossal says, the mammoth steppethe ancient ecosystem in which the giant proboscideans roamedcould be restored, helping fight climate change and pushing new technologies in gene editing in the process, helping extant elephants, which face their own survival threats.

But other technological breakthroughs will be necessary to make any of that possible. As noted by Nature, Church intends to use artificial elephant wombs to produce the proxy mammoths, so as to not require Asian elephant surrogates. Asian elephants are an endangered species; to use them as surrogates for proxy mammoths would be the cherry-on-top of an ethical dilemma sundae.

Were still a long way off from Colossals ultimate goals, but this recent achievement is a significant one, and a reminder that these de-extinction efforts involve serious science.

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Company Trying to Resurrect a Mammoth Makes a Stem Cell Breakthrough - Gizmodo

Lessons from inducible pluripotent stem cell models on neuronal senescence in aging and neurodegeneration – Nature.com

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