The article is a review of stem cell research and some of the challenges before the technology can become realizable patient therapy.  We tried to make it a general review for individuals from       various backgrounds

Karsy, Michael

Pandey, Varunkumar G

English

The Touro College and University System

Quill & Scope Volume 4 Volume IV Article 22 2011 Challenges in Stem Cell Therapy: Bench-To-Bedside Varunkumar G. Pandey New York Medical College Michael Karsy New York Medical College Follow this and additional works at: https://touroscholar.touro.edu/quill_and_scope  Part of the Arts and Humanities Commons, Higher Education Commons, and the Medicine and Health Sciences Commons Recommended Citation Pandey, V. G., & Karsy, M. (2011). Challenges in Stem Cell Therapy: Bench-To-Bedside. Quill & Scope, 4 (1). Retrieved from This Review is brought to you for free and open access by Touro Scholar. It has been accepted for inclusion in Quill & Scope by an authorized editor of Touro Scholar. For more information, please contact Timothy J Valente timothy.valente@touro.edu. Challenges in Stem Cell Therapy: Bench-To-Bedside Varunkumar G. Pandey & Michael Karsy Since, the isolation of human embryonic stem (hESCs) cells by Thomson et al. in 1998, stem cell research has been recognized as the most promising component of the regenerative medicine.1  Stem cells are capable of differentiating into any cell type of the body and this pluripotency allows for        limitless therapeutic potential.  However, the utility of hESCs is restricted because of pertinent ethical issues, limited availability of human blastocysts, and  possible allograft rejection. Furthermore, our    understanding of cellular differentiation and epigenetic regulation are still in the primitive stages and pose major hurdles in stem cell research.  Before stem cell therapy can become a clinical reality, it is imperative that we address critical issues relating to programming efficiency, tumor susceptibility, and graft survival and rejection.  Nonetheless, commendable milestones have been already achieved in the study of stem cells by a number of research groups, and regenerative medicine is gradually inching    towards a plausible reality of stem cell therapy.  The FDA has recently approved the usage of a hESC-based therapy in 2010 where clinical trials have been initiated by Geron Corporation for patients with spinal cord injury.  In this article, we appreciate the recent advancements in stem cell research and      discuss current challenges faced by various research groups in stem cell  research.   The discovery of induced pluripotent stem cells (iPSCs) has paved a new paradigm in stem cell re-search.  The exemplary ingenuity of Shinya Yamanaka in developing a cellular  reprogramming        technology that facilitates production of iPSCs from somatic cells provided a major breakthrough in stem cell research2.  Yamanaka hypothesize that transcription factors playing important roles in the maintenance of hESC identity also have pivotal roles in the     induction of pluripotency in somatic cells.  The research group identified numerous factors that are differentially expressed in hESCs in comparison to adult stem cells.  By performing detailed comparative analysis, they defined four key transcription factors, namely Oct3/4, Sox2, c-Myc, and Klf4, that are essential to the reprogramming of somatic cells.  This landmark finding lead to the realization of a long awaited scientific dream that adult somatic cells can be reprogrammed into induced stem cells and perhaps be used for therapeutic purposes.   Despite the efforts of Yamanaka in pioneering iPSC technology, several limitations immediately became apparent3.  The transgenes used for reprogramming were based on retroviral vectors with      random insertion into the host genome, allowing for possible interference with the endogenous gene structure that could result in undesirable insertional mutations. Furthermore, the lack of complete control of transgene expression could result in tumorigenesis.  Several solutions have been explored to address these issues including the use of cell-penetrating recombinant proteins for reprogramming cells.4,5   Initial studies exploring cellular reprogramming with Oct3/4, Sox2, c-Myc, and Klf4, have led way to the discovery of a multitude of additional transcription factors that can reprogram iPSCs and in some cases alter the eventual differentiation of cells.6,7  Alterations in chromatin structure affecting epigenetic regulation are important, dynamic regulators of global genetic expression in iPSCs but remain an       uncharted territory8  Disruption of tumor suppressor p53 or cell-cycle checkpoint inhibitors (e.g. p14/ARF, p21) can improve iPSC generation, however are also involved in carcinogenesis.9-12   Human iPSCs have been generated from fibroblasts, keratinocytes and CD34+ human peripheral blood cells13,14.  Recent studies have indicated that cell type and culture environment can affect iPSC generation.  While certain cell types may prove to be easier to extract cells from, such as fibroblasts from a skin biopsy, other cell types may be more effective for tissue development.  Development of iP-SCs from keratinocytes show lower rates of transgene retroviral insertion than fibroblasts thus        al-lowing for more regulated control of cell genetics.13  The low efficacy of iPSC generation in vitro also 30 remains an important challenge for the  generation of significant tissue yields.   Evaluation of generated iPSCs for therapeutic efficacy and tumor formation is necessary prior to implantation in patients.  In this regard, animal models will be important to assess germline transmission of iPSCs and cell incorporation into patient tissue.  Furthermore, animal models prior to clinical         development will be important to screen for the formation of teratoma tumor masses from                   undifferentiated iPSCs and patient immune reaction from iPSCs containing foreign antigens15.           The microenvironment of stem cell plays an important role in the regulation of quiescence and           differentiation.  However, animal models do not fully encompass human microenvironments and   evalu-ation of a biological mechanism for iPSCs engrafted for disease treatment will be important to   deter-mine therapeutic efficacy. Generation and application of iPSCs to human disease  Cellular delivery of iPSCs to patients remains a crucial technical limitation, which has driven inves-tigation into tissue engineering technologies.  While certain therapies will suffice with single, direct im-plantation of iPSCs (e.g. Parkinson’s disease), other approaches may     require multi-site cell delivery (e.g. spinal cord injury).  Ex vivo tissue engineering has emerged as a potential solution for artificial tis-sue formation and organogenesis16.  Extracellular matrices (ECM) composed of biocompatible materials in combination with pluripotent cells and specific culturing conditions have been suggested as scaffolds for organogenesis.  Technologies such as inkjet printing of collagen matrices, individual live cells, or stem cell growth factor have been used to pattern and generate custom 3D tissues.17-19  Decellularization of endogenous cells from tissues in order to leave an ECM template where iPSCs can be added to      regenerate cells has also been pursued in various organs including, heart, liver, kidney, pancreas, and intestine.20,21  The role of hypoxia in regulating stem cells has emerged as an important facet of          pluripotency and is actively being investigated.22  Explanted microvasculature beds serving as scaffolds for large tissue formation have also been explored to overcome hypoxic environments limiting iPSC  engraftment.23 Pandey & Karsy: Challenges in Stem Cell Therapy 31 A plethora of applications for iPSCs has been suggested, including tissue regeneration for a         congenital malformations, degenerative disorders, traumas, and genetic defects.  Therapeutic efficacy of hESCs has been demonstrated experimentally in animal models of spinal cord injury24, retinal disease25, Parkinson’s disease.26  In addition, the first FDA-approved stem cell therapy in humans was recently approved for spinal cord injury.27  Sponsored by Geron, Phase I trials for complete thoracic  injury will be performed using hESCs and have recruited the first patients in October 2010.  Disease-specific iPSCs generated from patient tissues can provide new insights into the pathophysiology of   various complex human diseases that currently lack effective models.  Although extensive literature   supports the devel-opment of stem cell therapies, results should be scrutinized diligently in order to    provide the best qual-ity of patient care.     Despite the remarkable potential for iPSCs, and the emergence of this exciting and rapidly         expanding field, a variety of technical challenges remain.  Historical evidence has suggested that       biotechnology takes approximately 10-15 years until the development of realizable therapies.28  While genetic engineering methods were discovered in the 1970s, FDA approval of insulin came in 1982 and was not widely available until the 1990s.  Advancements in iPSC technologies will continue to develop with effort from a cadre of new researchers, challenge grants, and national initiatives.  It is foreseeable that physicians in the near future will utilize stem cell therapies to treat many of the deleterious diseases currently incurable. R E F E R E N C E S   [1]     Thomson JA, Itskovitz-Eldor J, Shapiro SS, Waknitz MA, Swiergiel JJ, Marshall VS, Jones JM: Embryonic stem cell lines derived from human blastocysts. Science 282:1145-1147, 1998 [2]     Takahashi K, Yamanaka S: Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Cell 126:663-676, 2006 [3]     Yamanaka S: A fresh look at iPS cells. Cell 137:13-17, 2009 [4]     Kim D, Kim CH, Moon JI, Chung YG, Chang MY, Han BS, Ko S, Yang E, Cha KY, Lanza R, Kim KS: Generation of human induced pluripotent stem cells by direct delivery of reprogramming proteins. Cell Stem Cell 4:472-476, 2009 [5]     Zhou H, Wu S, Joo JY, Zhu S, Han DW, Lin T, Trauger S, Bien G, Yao S, Zhu Y, Siuzdak G, Scholer HR, Duan L, Ding S: Generation of induced pluripotent stem cells using recombinant proteins. Cell Stem Cell 4:381-384, 2009 [6]     Yamanaka S, Zhang XY, Maeda M, Miura K, Wang S, Farese RV, Jr., Iwao H, Innerarity TL: Essential role of NAT1/p97/DAP5 in embryonic differentiation and the retinoic acid pathway. EMBO J 19:5533-5541, 2000 [7]     Yamanaka S, Blau HM: Nuclear reprogramming to a pluripotent state by three approaches. Nature 465:704-712, 2010 [8]     Hanna JH, Saha K, Jaenisch R: Pluripotency and cellular reprogramming: facts, hypotheses, unresolved is-sues. Cell 143:508-525, 2010 [9]    Kawamura T, Suzuki J, Wang YV, Menendez S, Morera LB, Raya A, Wahl GM, Belmonte JC: Linking the p53 tumour suppressor pathway to somatic cell reprogramming. Nature 460:1140-1144, 2009 [10]  Li H, Collado M, Villasante A, Strati K, Ortega S, Canamero M, Blasco MA, Serrano M: The Ink4/Arf locus is a barrier for iPS cell reprogramming. Nature 460:1136-1139, 2009 [11]  Marion RM, Strati K, Li H, Murga M, Blanco R, Ortega S, Fernandez-Capetillo O, Serrano M, Blasco MA: A p53-mediated DNA damage response limits reprogramming to ensure iPS cell genomic integrity. Nature 460:1149-1153, 2009 Pandey & Karsy: Challenges in Stem Cell Therapy 32 [12] Utikal J, Polo JM, Stadtfeld M, Maherali N, Kulalert W, Walsh RM, Khalil A, Rheinwald JG, Hochedlinger K: Immortalization eliminates a roadblock during cellular reprogramming into iPS cells. Nature 460:1145-1148, 2009 [13]  Aasen T, Raya A, Barrero MJ, Garreta E, Consiglio A, Gonzalez F, Vassena R, Bilic J, Pekarik V, Tiscornia G, Edel M, Boue S, Izpisua Belmonte JC: Efficient and rapid generation of induced pluripotent stem cells from human keratinocytes. Nat Biotechnol 26:1276-1284, 2008 [14]  Loh YH, Agarwal S, Park IH, Urbach A, Huo H, Heffner GC, Kim K, Miller JD, Ng K, Daley GQ: Genera-tion of induced pluripotent stem cells from human blood. Blood 113:5476-5479, 2009 [15]   Li JY, Christophersen NS, Hall V, Soulet D, Brundin P: Critical issues of clinical human embryonic stem cell therapy for brain repair. Trends Neurosci 31:146-153, 2008 [16]  Rustad KC, Sorkin M, Levi B, Longaker MT, Gurtner GC: Strategies for organ level tissue engineering. Organogenesis 6:151-157, 2010 [17]  Boland T, Xu T, Damon B, Cui X: Application of inkjet printing to tissue engineering. Biotechnol J 1:910-917, 2006 [18]  Ilkhanizadeh S, Teixeira AI, Hermanson O: Inkjet printing of macromolecules on hydrogels to steer neural stem cell differentiation. Biomaterials 28:3936-3943, 2007 [19]  Nakamura M, Kobayashi A, Takagi F, Watanabe A, Hiruma Y, Ohuchi K, Iwasaki Y, Horie M, Morita I, Takatani S: Biocompatible inkjet printing technique for designed seeding of individual living cells. Tissue Eng 11:1658-1666, 2005 [20]  Baptista PM, Orlando G, Mirmalek-Sani SH, Siddiqui M, Atala A, Soker S: Whole organ decellularization - a tool for bioscaffold fabrication and organ bioengineering. Conf Proc IEEE Eng Med Biol Soc 2009:6526-6529, 2009 [21]  Ott HC, Matthiesen TS, Goh SK, Black LD, Kren SM, Netoff TI, Taylor DA: Perfusion-decellularized ma-trix: using nature's platform to engineer a bioartificial heart. Nat Med 14:213-221, 2008 [22]  Ma T, Grayson WL, Frohlich M, Vunjak-Novakovic G: Hypoxia and stem cell-based engineering of mesen-chymal tissues. Biotechnol Prog 25:32-42, 2009 [23]  Chang EI, Bonillas RG, El ftesi S, Chang EI, Ceradini DJ, Vial IN, Chan DA, Michaels J, Gurtner GC: Tis-sue engineering using autologous microcirculatory beds as vascularized bioscaffolds. FASEB J 23:906-915, 2009 [24]  Keirstead HS, Nistor G, Bernal G, Totoiu M, Cloutier F, Sharp K, Steward O: Human embryonic stem cell-derived oligodendrocyte progenitor cell transplants remyelinate and restore locomotion after spinal cord in-jury. J Neurosci 25:4694-4705, 2005 [25]  Lamba DA, Gust J, Reh TA: Transplantation of human embryonic stem cell-derived photoreceptors restores some visual function in Crx-deficient mice. Cell Stem Cell 4:73-79, 2009 [26]  Yang D, Zhang ZJ, Oldenburg M, Ayala M, Zhang SC: Human embryonic stem cell-derived dopaminergic neurons reverse functional deficit in parkinsonian rats. Stem Cells 26:55-63, 2008 [27]  Wadman M: Stem cells ready for prime time. Nature 457:516, 2009 [28]  Daley GQ: Stem cells: roadmap to the clinic. J Clin Invest 120:8-10, 2010 Pandey & Karsy: Challenges in Stem Cell Therapy 33 

Challenges in Stem Cell Therapy: Bench-To-Bedside

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Challenges in Stem Cell Therapy: Bench-To-Bedside

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