10 provocative stem cell questions: what are your answers?

stem cell contest

heart stem cellsThere’s always debate about stem cells and regenerative medicine, right? There are very strong opinions in our field. Here is a list of 10 current, provocative questions. I have my own ideas about the answers to these. Weigh in with comments with your answers.

I’m going to do a follow up post with some discussion of the questions. I may do another follow up with the top 10 policy questions in our arena.

Here’s today’s list in no particular order.

stem cell contest

  1. Does the adult heart contain clinically meaningful levels of stem cells or stem-like cells? Do the adult kidney or lungs have such cells in meaningful numbers?
  2. Are there important, consistent instances where high-quality, validated human IPS cells are not fully functionally equivalent to top-notch validated human ES cells?
  3. Can SCNT-derived human ES cells (NT-hESC) have clinical impact to warrant the old name “therapeutic cloning” that describes their production, and to justify the difficulty of producing them?
  4. What is the future of direct reprogramming/transdifferentiation? Are there going to be concrete ways that this exciting technology is superior for clinical applications as compared to an intermediate IPS cell or human ES cell step prior to differentiation?
  5. How big a deal clinically are exosomes going to be? Why?
  6. What is the best clinically realistic way to track stem cells post-transplant?
  7. Can adult stem cells from distinct parts of the body be essentially functionally homologous?
  8. Do stem cells have real,concrete promise for anti-aging applications? Does young blood have anti-aging properties in humans and if so, is anybody on the right track for the mechanisms? Can research in this or related areas lead to safe and effective anti-aging products? Can blastemas or other regenerative healing units/processes be induced in people to spur regeneration of large functional units such as digits or limbs or other body parts?
  9. How far can organoid technology takes us and will it have direct clinical impact?
  10. Can normal, functional human gametes be made from pluripotent stem cells and potentially used for reproduction?

11 Comments


  1. 1. Does the adult heart contain clinically meaningful levels of stem cells or stem-like cells? Do the adult kidney or lungs have such cells in meaningful numbers?

    Yes to both questions. However, there is a problem. As an individual ages the extracellular matrix (ECM) surrounding the stem cells becomes denser limiting the ability of the adult stem cells to leave their connective tissue niches and participate in the healing process at distant sites. We performed an experiment to test whether adult stem cell numbers decreased with age of the individual. Long story short, it took 15 min to digest the tissue of newborn (humans) to release the adult stem cells, while it took over 8 hours to release a similar number of adult stem cells from geriatric (80+ year old humans) per unit volume.

    2. Are there important, consistent instances where high-quality, validated human IPS cells are not fully functionally equivalent to top-notch validated human ES cells?
    3. Can SCNT-derived human ES cells (NT-hESC) have clinical impact to warrant the old name “therapeutic cloning” that describes their production, and to justify the difficulty of producing them?
    4. What is the future of direct reprogramming/transdifferentiation? Are there going to be concrete ways that this exciting technology is superior for clinical applications as compared to an intermediate IPS cell or human ES cell step prior to differentiation?

    5. How big a deal clinically are exosomes going to be? Big. Why? Tissues/differentiated cells secrete paracrine factors (inductive exosomes) that can influence the differentiative capabilities of activated stem cells.

    6. What is the best clinically realistic way to track stem cells post-transplant?

    7. Can adult stem cells from distinct parts of the body be essentially functionally homologous? Yes. My group named adult stem cells based on their differentiative functionality rather than tissue of origin, i.e., totipotent stem cells (TSCs), pluripotent stem cells (PSCs), mesodermal stem cells (MesoSCs), ectodermal stem cells (EctoSCs), endodermal stem cells (EndoSCs), etc.. Further experimentation determined their unique cell surface markers, attributes in vitro, attributes in transplant models in vivo, attributes in situ, etc. We have isolated TSCs, PSCs, and MesoSCs from 37 different tissues and organs thus far from 11 different species, including humans. While the ratios of the stem cells differ with respect to the different tissue types, the TSCs, PSCs, and MesoSCs have the same above characteristics no matter from which tissue they are isolated.

    8. Do stem cells have real, concrete promise for anti-aging applications? Yes. Does young blood have anti-aging properties in humans and if so, is anybody on the right track for the mechanisms? As in #1 above, it is more along the lines of the quantity of adult stem cells circulating in the blood rather than whether the blood is young or old. One can mimic the ability of “young” blood to enhance regeneration/repair in “old” blood by increasing the concentration of adult stem cells in the blood. Increases in stem cell numbers in the blood can be accomplished by trauma, exercise, stem cell infusion, and certain nutraceuticals. Decreases in stem cell numbers can occur with alcohol ingestion.

    Can research in this or related areas lead to safe and effective anti-aging products? I believe so.

    Can blastemas or other regenerative healing units/processes be induced in people to spur regeneration of large functional units such as digits or limbs or other body parts? What is needed are large quantities of the appropriate activated stem cells in the area for regeneration/repair. I would also suggest that to speed up this process, that the stem cells would need to be embedded in tissue-specific ECMs with appropriate inductive factors to support their growth and differentiation.

    9. How far can organoid technology takes us and will it have direct clinical impact? Depends on what you want to do. If you want to replace an entire organ, such as heart, lungs, liver, etc., one needs to be mindful of the histoarchitechture of the organ, various cell populations with their respective ECM, including inductive agents, as well as the unique interplay of their physiologies. If, on the other hand, a portion of an organ will suffice, such as pancreatic islets, that is currently quite doable using decellularized matrices, donor islets, and autologous TSCs and PSCs. We generated pancreatic islet organoids using decellularized porcine pancreatic matrices with embedded donor islets and encased in the recipient’s autologous PSCs and TSCs. Since the outermost cell populations were the recpient’s own cells, the construct would not be rejected by their immune system.

    10. Can normal, functional human gametes be made from pluripotent stem cells and potentially used for reproduction? By definition, pluripotent stem cells will form all somatic cells of the body, but will NOT form gametes, notochord, or the embryonic portion of the placenta. So the answer for PSCs is NO. In contrast, totipotent stem cells will form all the somatic cells of the body, the notochord, and the embryonic portion of the placenta. So for TSCs the answer is YES. We performed an experiment with TSCs in an animal model suggesting that possibility. However, the experiments need to be repeated with human cells to verify. TSCs, derived from the connective tissues surrounding skeletal muscle of adult rats, were cultured in conditioned medium (exosomes) from the disrupted testes of a different species. We had specific antibodies for both species and for spermatogonia. The cells that were formed only co-labeled for rat and spermatogonial antibodies, thus suggesting that rat TSCs could form gametes. Whether the induced spermatogonia were functionally active was not examined at that time.

    The data for the above has been published. Publications can be found on the ResearchGate website under my name.


    • Henry,
      Can you cite some of the key, peer-reviewed publications for readers here? Many are not members of Research Gate, plus we’d like to know which ones you think are the most important and conclusive? Paul


      • By definition, pluripotent stem cells will form all somatic cells of the body, but will NOT form gametes, notochord, or the embryonic portion of the placenta. So the answer for PSCs is NO. In contrast, totipotent stem cells will form all the somatic cells of the body, the notochord, and the embryonic portion of the placenta.

        ??? I was under the understanding that PSCs (derived from the ICM) form the entire embryo (thus also gametes and notochord) except for the extra-embryonic tissues. Are there two competing definitions for PSCs and TSCs ut there?


  2. Asymmetrex weighs in:

    1. Can’t really answer this question without a definition for “clinically meaningful” and “meaningful” in this specific context. But Asymmetrex thinks that the author is biasing for negative responses (whether consciously or unknowingly!).

    2. Another highly weighted question for a negative response. “Fully functional equivalent?” Even different strains for ESCs are not “fully functionally equivalent” to one another. Who decides what are “top-notch validated human ES cells?”

    3. The years have gone by, but the problematic biology and ethics of SCNT-derived human ES cells is just the same as ever.

    4. This question is actually a request for a prediction of the future, which cannot be known. However, there are things we can say within the time frame of a near future that is not so distant that our speculations become meaningless. Lacking the asymmetric self-renewal of distributed stem cells, direct rp/td cells do not have the biological property that is obligatory for providing long-term transplantation therapy for renewing tissues, which are most. It is also possible that the inherent genetic and epigenetic mutations of reprogramming will disqualify the cells for even short-term cell replacement therapies.

    5. Who knows? This is a very intriguing of field of investigation that is rapidly maturing. As a better understanding of the physiological roles of exosomes and related information-bearing cell-produced particulates develops, their potential for medical manipulation will be clearer. A technical advance that would help tremendously is development of better technologies for counting and fractionating them.

    6. First, know how many were transplanted, and Asymmetrex doesn’t mean all the cells in the tube; because no one has tubes that contain 100% tissue stem cells. Thereafter, introduce sensitive biomarker genes expressed from regulatory elements that confer expression highly specific for tissue stem cells. How do you find such regulatory elements? Read Asymmetrex reports and think about it. Or talk to Asymmetrex.

    7. Who knows? Biology has many exceptions to scientists rules. What we do know is that the evidence for tissue-specific stem cells is much more compelling than that for “universal” tissue stem cells in the post-natal mammals that can “plug N play” in several different mature tissues.

    8. Another one of those negative bias qualifers: “concrete promise?” I think these are only offered in some religions. These are not one question, but many that may pose as subliminal pejorative suggestion to readers. From 30,000 feet up, if we allow that changes in stem cells contribute to human aging, than one or more of the many varied studies of their aging properties may provide knowledge that can either improve health during aging and/or increase longevity.

    9. Asymmetrex expects that human tissue organoids will definitely yield knowledge that could not be learned from mono-cell culture systems, 2d co-culture systems, and animal models. The challenge is assessing whether the new information better reflects normal in vivo tissue function or instead is only a new kind of distortion of it. The problem is that many investigators presume relevance instead of diligently searching for means to validate organoid experimental systems before, during, after their analyses.

    10. Given recent progress in mice and human cells, it seems likely. But why do it for reproduction purposes? Solving the inherent genetic and epigenetic mutagenesis of iPSC cell production seems an unlikely prospect for now. Until that problem is solved why would anyone wish to burden offspring with such risk of defects and deficiencies?

    Wait! Asymmetrex now recognizes that the answer to this question is presently a definite “No.” “Normal” does not include increased mutation load, which iPSCs and their derivative cells presently have.

    Thanks for the exercise!

    Asymmetrex, LLC
    http://asymmetrex.com


    • James,
      Since when do words/phrases like “clinically meaningful”, “fully functionally equivalent”, and “concrete” have negative connotations?
      What I was and still am consciously trying to indicate in this post is that there’s a lot of noise out there in the stem cell universe and I’m interested in signal (i.e. evidence-based (is that a bad word too?), data-centric conclusions). Cheers, Paul


      • Hello, Paul:

        Not “negative connotations.” “Biasing for negative responses” [to the question]. If the question is formulated with constraints that are not well defined but could be perceived as arbitrarily idealistic, affirmative answers are more difficult to give. I appreciate your interest in fostering high “signal” discussions. However, in our efforts to maintain rigor in scientific discussions, we have to be careful that we don’t become pejorative in our tone. After all, biology and medicine, even more so, are rather noisy beasts that as scientists and physicians we try to calm to our will for increasing sound knowledge and doing good.

        Cheers!

        James, aka the voice of “Asymmetrex”


  3. If Jim O’Neill gets the nod at FDA, it could mean the end of your old way of thinking Paul, and patients with complete informed consent can take advantage of stem cells in translational medicine for terminal conditions. I know we’ve discussed this in the past and your fear is “that it’s a slippery slope” but in the meantime, many people have suffered and died from conditions where they could have been given symptomatic relief from stem cells that have been proven safe. As Arnold Caplan at Case Western has so eloquently argued, let a safe stem cell or drug get out to people with clear warnings about efficacy, and let the results be gathered from a far bigger cohort and get much better data. The Phase 1-2-3 model has some huge problems because it was developed at another time in technological history.


  4. I will take a stab at these and try not to b*tch too much about how you wrote the questions, but I am a grumpy old man.
    1. Yes. More in young people than old people – it’s stochastic. Will we be able to do something with them? Not today, but someday.
    2. No. If your iPS cells aren’t as good as ES cells it’s because you made them wrong, not because ES cells are magic. Get it together.
    3. No, this is stupid, and everyone associated with SCNT is too. It kills me to see how many people we hail as stem cell leaders because they were associated with this nonsense. It’s not practical at any scale, and people have a crap time reproducing it. This will never ever be anything but an academic pursuit.
    4. Nope. Not only will there never be a clinical application, it’s not exciting and I don’t know why you are so excited about it. It’s much better to grow the right type of cells from iPS and transplant them in rather than trying to get the right inhibitors to the right place at the right time. This is horrible and will never see the light of day. It’s fun to write papers about, though.
    5. Exosomes – nope. See #4 about getting them to the right place at the right time. The contents of said exosomes may be interesting, but the idea of clinical exosomes, please.
    6. Somewhat cell-type specific, but through either PET or some kind of cell-type specific molecule that can be tracked. I’m whiffing on this answer, but it really depends.
    7. Yes, under the right conditions.
    8. Yes, No, No, and No. You can’t make someone younger by adding young stuff to an old person. You have to make the old cells into young cells. OSKM.
    9. May have some relevance in some phenotypic screens, but for the most part the stuff that CDI and Axiogenesis sells isn’t worth the culture flask it’s grown in. But I’m a bitter old man.
    10. Yes. If it’s not already happening, it will soon. The question is should we? The people who say we shouldn’t will be far behind the people already working on it.


  5. 1 of 8,315

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    In response to Question 8:

    Noninvasive intranasal stem cells bypass the blood-brain barrier to target the brain to treat Parkinson’s disease, Alzheimer’s, MS, stroke, brain tumors and other brain disorders.

    Together with my collaborators in Germany, especially Lusine Danielyan M.D., we discovered and patented (1) that therapeutic cells, including adult stem cells, immune cells (Treg, CAR-T, etc.) and genetically-engineered cells, can be delivered to the brain using the noninvasive intranasal delivery method that I developed (2). The first of our scientific papers on this new discovery describes this successful method of delivery and proprietary formulations that enhance delivery (3). The second of our papers describes the successful treatment of Parkinson’s disease in an animal model with intranasal adult bone marrow derived mesenchymal stem cells (4). Intranasal stem cells bypass the blood-brain barrier to target the brain by traveling extracellularly along the olfactory neural pathway with minimal delivery to other organs. Once in the brain, adult stem cells target the damaged areas of the brain specifically to treat the underlying disease (4). Researchers at University Medical Center Utrecht in the Netherlands have demonstrated the effectiveness of intranasal stem cell treatment technology in an animal model of neonatal cerebral ischemia (5) and also in animals with neonatal brain damage (6, 6b, 6c, 6d) and subarachnoid hemorrhage (6a). Researchers at Emory University have used our intranasal stem cell treatment successfully in animal models of stroke (7) and neonatal stroke (7a), and researchers at Uppsala University in Sweden have demonstrated that intranasal CAR/FoxP3-engineered T regulatory cells efficiently suppressed ongoing inflammation in an EAE model of multiple sclerosis leading to reduced disease symptoms (8). Intranasal adult neural stem cells have also been shown to improve the EAE model of multiple sclerosis (MS) (9) as have intranasal mesenchymal stromal cells (10). Other researchers have reported that intranasal stem cells target and treat brain tumors (11, 12). This intranasal delivery, targeting and treatment technology can make stem cell treatments practical for brain disorders by eliminating the need for invasive neurosurgical implantation of cells and by eliminating the need for intravenous delivery that disperses cells throughout the body resulting in unwanted systemic exposure. This delivery and treatment method can facilitate the development of stem cell, immune cell and genetically-engineered cell therapies for Parkinson`s, PSP, Huntington’s, Alzheimer`s (13), MS, epilepsy, stroke, neonatal ischemia, brain tumors, traumatic brain injury (TBI) and spinal cord injury (14).
    In humans, Gonadotropin-releasing hormone expressing neurons are known to reach the brain by using this same olfactory neural pathway during development. In addition, pathologic cells, such as the amoeba Naegleria fowleri, are known to enter the brains of humans by this same pathway and cause amoebic infection of the brain. We have discovered how to use this pathway to deliver therapeutic cells to the brain to treat brain disorders.

    Best Regards,

    Bill
    William H. Frey II, Ph.D.
    Center for Memory & Aging (Alzheimer’s Research Center)
    Regions Hospital, 640 Jackson St., St. Paul, MN 55101
    Professor of Pharmaceutics, Neurology and Neuroscience
    University of Minnesota
    [email protected]
    Cell phone: 651-261-1998

    References:

    1. Frey, Danielyan and Gleiter (2012). Methods, pharmaceutical compositions and articles of manufacture for administering therapeutic cells to the animal central nervous system. U.S. Patent 8283160 B2 filed 2009 and issued October 9, 2012.
    2. Frey, W.H. 2nd (1997). Method of administering neurologic agents to the brain. US Patent 5,624,898 filed 1989 and issued April 29, 1997.
    3. Danielyan, L., et al., Intranasal delivery of cells to the brain. Eur J Cell Biol, 2009. 88(6): p. 315-24.
    4. Danielyan, L., et al., Therapeutic efficacy of intranasally delivered mesenchymal stem cells in a rat model of Parkinson disease. Rejuvenation Res, 2011. 14(1): p. 3-16.
    5. van Velthoven, C. et al. Nasal administration of stem cells: a promising novel route to treat neonatal ischemic brain damage. Pediatr Res 2010. 68(5): p. 419-422.
    6. Donega, V., et al., The endogenous regenerative capacity of the damaged newborn brain: boosting neurogenesis with mesenchymal stem cell treatment. J Cereb Blood Flow Metab, 2013. 33(5): p. 625-34.
    6a. Kooijman, E., et al., Intranasal Mesenchymal stem cell transplantation restores brain damage, improves sensori-motor function and reverses depressive-like behavior in a model of subarachnoidal hemorrhage in rats. Brain, Behavior, and Immunity. 2013, 32 (Supplement):e38.
    6b. Donega, V., et al., Intranasally administered mesenchymal stem cells promote a regenerative niche for repair of neonatal ischemic brain injury. Exp Neurol, 2014. 261: p. 53-64.
    6c. Donega, V. et al., Intranasal mesenchymal stem cell treatment for neonatal brain damage: long-term cognitive and sensorimotor improvement. PLoS ONE. 2013;8(1):e51253.
    6d. Donega, V. et al., Intranasal Administration of Human MSC for Ischemic Brain Injury in the Mouse: In Vitro and In Vivo Neuroregenerative Functions PLoS ONE 2014. 9(11): e112339.
    7. Wei N., et al. Delayed intranasal delivery of hypoxic-preconditioned bone marrow mesenchymal stem cells enhanced cell homing and therapeutic benefits after ischemic stroke in mice. Cell Transplantation, 2013. 22(6) p. 977-991.
    7a. Wei Z., et al. Intranasal Delivery of Bone Marrow Mesenchymal Stem Cells Improved Neurovascular Regeneration and Rescued Neuropsychiatric Deficits After Neonatal Stroke in Rats. Cell Transplantation, 2015. 24: 391-402.
    8. Fransson M., et al. CAR/FoxP3-engineered T regulatory cells target the CNS and suppress EAE upon intranasal delivery. J Neuroinflammation, 2012. 9:112.
    9. Wu, S., et al., Intranasal Delivery of Neural Stem Cells: A CNS-specific, Non-invasive Cell-based Therapy for Experimental Autoimmune Encephalomyelitis. J Clin Cell Immunol, 2013. 4:310.
    10. Fransson, M., et al., Intranasal delivery of central nervous system-retargeted human mesenchymal stromal cells prolongs treatment efficacy of experimental autoimmune encephalomyelitis. Immunology, 2014. 142: p. 431–441.;
    11. Reitz, M., et al. Intranasal delivery of neural stem/progenitor cells: A noninvasive passage to target intracerebral glioma. Stem Cells Trans Med, 2012. 1(12): p. 866-73.
    12. Balyasnikova, I., et al., Intranasal Delivery of Mesenchymal Stem Cells Significantly Extends Survival of Irradiated Mice with Experimental Brain Tumors. Molecular Therapy, 2014. p. 22(1):140-8.
    13. Danielyan, L. et al., Intranasal delivery of bone marrow-derived mesenchymal stem cells, macrophages, and microglia to the brain in mouse models of Alzheimer’s and Parkinson’s disease. Cell Transplant. 2014, 23 Suppl 1:S123-39.
    14. Ninomiya, K. et al., Intranasal delivery of bone marrow stromal cells to spinal cord lesions J Neurosurg Spine, 2015, (published online).


  6. Dear Paul, to further expand on my post of February 6, 2017.

    1. Does the adult heart contain clinically meaningful levels of stem cells or stem-like cells? Do the adult kidney or lungs have such cells in meaningful numbers?

    Short answer is YES. All three organs, along with all other organs and tissues in the body (hypothesized), contain resident populations of adult pluripotent stem cells and resident populations of totipotent stem cells. Both populations of adult-derived stem cells can be manipulated with exogenous agents to effect repair and replacement of damaged tissues. We have noted this by isolation of adult-derived stem cells from different organs and tissues (37 to date, thus far) as well as cryosectioning and staining for the unique markers of adult-derived stem cells.

    7. Can adult stem cells from distinct parts of the body be essentially functionally homologous?

    Short answer is YES, but depends on the stem cell type examined. For example, adult-derived ectodermal stem cells will only naturally form those cell types of ectodermal embryological origin. Similarly, adult-derived mesodermal stem cells will only naturally form those cell types of mesodermal embryological origin and adult-derived endodermal stem cells will only form those cell types of endodermal embryological origin. Adult-derived pluripotent stem cells will only form cell types of ectodermal, mesodermal, or endodermal embryological origin, but will NOT for the gametes. In contrast, adult-derived totitpotent stem cells will for, cell types of ectodermal, mesodermal, and endodermal embryological origin as well as forming the gametes, sperm and ova. The ectodermal stem cells, mesodermal stem cells, and endodermal stem cells approximate 9% of the cell types in the body; the pluripotent stem cells comprise approximately 0.9% of the cell types of the body; and the totipotent stem cells comprise approximately 0.1% of the cell types of the body.

    8. Do stem cells have real, concrete promise for anti-aging applications?

    YES. Adult-derived ectodermal stem cells, mesodermal stem cells, endodermal stem cells, pluripotent stem cells, and totipotent stem cells have an inherent biological clock of zero as long as they maintain an undifferentiated state. Only when these adult-derived stem cells progress from a stem cell state to a progenitor cell state (induced differentiation of these stem cells) does their biological clock begin. Therefore, by infusing younger-aged stem cells into an older-aged individual can one effectively induce anti-aging properties in the individual.

    10. Can normal, functional human gametes be made from pluripotent stem cells and potentially used for reproduction?

    Short answer is NO, gametes cannot be made from pluripotent stem cells. However, gametes can be made from adult-derived totipotent stem cells (isolated from any organ or tissue).

    Take care,

    Henry
    Henry E. Young, PhD
    Professor of Anatomy, MUSM (Retired)
    Chief Science Officer
    Dragonfly Foundation for Research and Development
    1515 Bass Rd, Suite E (Corporate Office)
    Macon, GA 31210 USA
    [email protected]

    And you requested references for the above work. The most pertinent ones can be found below:

    REFERENCES
    1. Young HE, Wright RP, Mancini ML, Lucas PA, Reagan CR, Black AC Jr. Bioactive factors affect proliferation and phenotypic expression in pluripotent and progenitor mesenchymal stem cells. Wound Repair and Regeneration 6(1):65-75, 1998.
    2. Young HE, Steele T, Bray RA, Detmer K, Blake LW, Lucas PA, Black AC Jr. Human progenitor and pluripotent cells display cell surface cluster differentiation markers CD10, CD13, CD56, CD90 and MHC Class-I. Proc. Soc. Exp. Biol. Med. 221:63-71, 1999.
    3. Young HE. Stem cells and tissue engineering. In: Gene Therapy in Orthopaedic and Sports Medicine, J. Huard and F.H. Fu, eds., Springer-Verlag New York, Inc., Chap. 9, pg. 143-173, 2000.
    4. Young HE, Duplaa C, Young TM, Floyd JA, Reeves ML, Davis KH, Mancini GJ, Eaton ME, Hill JD, Thomas K, Austin T, Edwards C, Cuzzourt J, Parikh A, Groom J, Hudson J, Black AC Jr. Clonogenic analysis reveals reserve stem cells in postnatal mammals. I. Pluripotent mesenchymal stem cells. Anat. Rec. 263:350-360, 2001.
    5. Young HE, Steele T, Bray RA, Hudson J, Floyd JA, Hawkins K, Thomas K, Austin T, Edwards C, Cuzzourt J, Duenzl M, Lucas PA, Black AC Jr. Human reserve pluripotent mesenchymal stem cells are present in the connective tissues of skeletal muscle and dermis derived from fetal, adult, and geriatric donors. Anat. Rec. 264:51-62, 2001.
    6. Romero-Ramos M, Vourc’h P, Young HE, Lucas PA, Wu Y, Chivatakarn O, Zaman R, Dunkelman N, El-Kalay MA, Chesselet M-F Neuronal differentiation of stem cells isolated from adult muscle. J Neurosci Res 69:894-907, 2002.
    7. Young HE. Existence of reserve quiescent stem cells in adults, from amphibians to humans. Curr Top Microbiol Immunol. 280:71-109, 2004.
    8. Young HE, Black Jr AC. Adult stem cells. Anat. Rec. 276A:75-102, 2004.
    9. Young HE, Duplaa C, Romero-Ramos M, Chesselet M-F, Vourc’h P, Yost MJ, et al. Adult reserve stem cells and their potential for tissue engineering. Cell Biochem Biophys, 40(1):1-80, 2004.
    10. Young HE, Duplaa C, Yost MJ, Henson NL, et al. Clonogenic analysis reveals reserve stem cells in postnatal mammals. II. Pluripotent epiblastic-like stem cells. Anat. Rec. 277A:178-203, 2004.
    11. Vourc’h P, Romero-Ramos M, Chivatakarn O, Young HE, Lucas PA, El-Kalay M, Chesselet M-F. Isolation and characterization of cells with neurogenic potential from adult skeletal muscle. Biochemical and Biophysical Research Communications 317:893-901, 2004.
    12. Seruya M, Shah A, Pedrotty D, du Laney T, Melgiri R, McKee JA, Young HE, Niklason LE. Clonal Population of adult stem cells: life span and differentiation potential. Cell Transplant 13:93-101, 2004
    13. Young HE, Black AC Jr. Differentiation potential of adult stem cells. In: Contemporary Endocrinology: Stem Cells in Endocrinology, L.B. Lester, ed., The Humana Press Inc., Totowa, NJ. Chap. 4, p. 67-92, 2005b.
    14. Vourc’h P, Lacar B, Mignon L, Lucas PA, Young HE, Chesselet MF. Effect of neurturin on mulitpotent cells isolated from the adult skeletal muscle. Biochem Biophys Res Commun 332:215-223, 2005.
    15. Henson NL, Heaton ML, Holland BH, Hawkins KC, Rawlings B, Eanes E, Bozof R, Powell S, Grau R, Fortney J, Peebles B, Kumar D, Yoon JI, Godby K, Collins JA, Sood R, Bowyer 3rd FP, Black Jr AC, Young HE. Karyotypic analysis of adult pluripotent stem cells. Histology and Histopathology, 20: 769-784, 2005.
    16. Mignon L, Vourc’h P, Romero-Ramos M, Osztermann P, Young HE, Lucas PA, Chesselet MF. Transplantation of multipotent cells extracted from adult skeletal muscles into the adult subventricular zone of adult rats. J Comp Neurol 491:96-108, 2005.
    17. Young HE, Duplaa C, Katz R, Thompson T, et al. Adult-derived stem cells and their potential for tissue repair and molecular medicine. J Cell Molec Med 9:753-769, 2005.
    18. Young HE, Black AC Jr. Adult-derived stem cells. Minerva Biotechnologica Cancer Gene Mechanisms and Gene Therapy Reviews 17:55-63, 2005.
    19. Stout CL, Ashley DW, Morgan III JH, Long GF; Collins JA, Limnios JI, Lochner F, McCommon G, Hixson D, Black Jr AC, Young HE. Primitive stem cells reside in adult swine skeletal muscle and are mobilized into the peripheral blood following trauma. American Surgeon 73 (11):1106-1110, 2007.
    20. Stout CL, McKenzie J, Long G, Henson N, Hawkins KC, Ashley DW, Collins J, Hixson D, Black Jr AC, Young HE. Discovery of pluripotent and totipotent stem cells in the heart of the adult rat. Amer Surg 73:S63, 2007.
    21. Young HE and Black Jr AC. Naturally occurring adult pluripotent stem cells. In: Stem Cells: From Biology to Therapy, Advances in Molecular Biology and Medicine. 1st Ed, R.A. Meyers, Ed, WILEY-BLACKWELL-VCH Verlag GmbH & Co. KGaA. Chap 3, pp. 63-93, 2013.
    22. Young HE, Hyer L, Black AC Jr, Robinson JS Jr. Adult stem cells: from bench-top to bedside. In: Tissue Regeneration: Where Nanostructure Meets Biology, 3DBiotech, North Brunswick, NJ Chap 1, pp 1-60, 2013.
    23. Young HE, Hyer L, Black AC Jr, Robinson JS Jr. Treating Parkinson disease with adult stem cells. J Neurological Disorders, 2:1, 2013.
    24. McCommon GW, Lochner F, Black Jr AC, Young HE. Primitive adult-derived stem cells are present in the blood of adult equines and can be increased in number with moderate exercise or ingestion of a cyanobacter, Aphanizomenon flos-aquae. Autocoids 2: 103, 2013.
    25. Young HE, Black AC. Pluripotent Stem Cells, Endogenous versus Reprogrammed, a Review. MOJ Orthop Rheumatol 1(4): 00019, 2014.
    26. Young HE, Limnios JI, Lochner F, McCommon G, Cope LA, Black AC Jr. Pancreatic islet composites secrete insulin in response to a glucose challenge. J Stem Cell Res 1(1) 001: 1-12, 2017.
    27. Young HE, Henson NL, Black GF, Hawkins KC, Coleman JA, Black AC Jr. Location and characterization of totipotent stem cells and pluripotent stem cells in the skeletal muscle of the adult rat. J Stem Cell Res 1(1) 002: 1-17, 2017.
    28. Young HE, Speight MO, Black AC Jr. Functional Cells, Maintenance Cells, and Healing Cells. J Stem Cell Res. 1(1): 003: 1-4, 2017.
    29. Young HE, Lochner F, Lochner D, Lochner D, McCommon G, Black AC Jr. Primitive Stem Cells in Adult Feline, Canine, Ovine, Caprine, Bovine, and Equine Peripheral Blood. J Stem Cell Res. 1(1) 004: 1-6, 2017.
    30. Young HE, Lochner F, Lochner D, Lochner D, Black GF, Coleman JA, Young VE, McCommon G, Black Jr AC. Primitive stem cells in adult human peripheral blood. J Stem Cell Res. 1(2) 001:1-6, 2017.

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