Stem cells: Definition, characteristics, classification, sources and ethical approaches

Zeynep Konukcu Mehdılı; Özgün Selim Germiyan; Afig Huseyinov Berdeli; Yiğit Uyanıkgil

doi:10.19161/etd.1870790

TR EN

Kök hücreler: Tanım, özellikler, sınıflandırma, kaynaklar ve etik yaklaşımlar

Abstract

Amaç: Kök hücreler, biyolojik sistemlerin gelişiminde kritik öneme sahip; kendi kendilerini yenileyebilen ve uygun ortamlarda farklı hücre tiplerine dönüşebilme (farklılaşma) potansiyeli olan özelleşmemiş öncül hücrelerdir. Embriyonik dokulardan kemik iliğine, göbek kordonundan yetişkin organlarına kadar pek çok dokuda bulunurlar. Bu hücreler, asimetrik bölünme mekanizması sayesinde bir yandan kök hücre havuzunun devamlılığını sağlarken diğer yandan doku onarımı ve yenilenmesi süreçlerinde merkezi rol üstlenirler. Gereç ve Yöntem: Çalışma kapsamında kök hücreler; farklılaşma potansiyellerine göre totipotent, pluripotent, multipotent, oligopotent ve unipotent olarak beş grupta sınıflandırılmıştır. Kaynaklarına göre ise embriyonik ve yetişkin kök hücreler olarak iki ana başlık altında ele alınmıştır. Ayrıca, somatik hücrelerin yeniden programlanmasıyla elde edilen indüklenmiş pluripotent kök hücreler ve tümör oluşumundan sorumlu olan kanser kök hücrelerinin biyolojik özellikleri, yüzey belirteçleri (CD34, CD133, CD44 vb.) ve bölünme türleri literatür verileri ışığında analiz edilmiştir. Sonuç: Kök hücreler; rejeneratif tıp ve doku mühendisliği alanında lösemi, Parkinson, diyabet ve kalp hastalıkları gibi pek çok dejeneratif sürecin tedavisinde devrimsel bir terapötik potansiyel taşımaktadır. İndüklenmiş pluripotent kök hücreler teknolojisi, embriyonik hücre kullanımına bağlı etik sorunları aşma ve hastaya özgü bağışıklık reddi riskini azaltma noktasında büyük avantajlar sunmaktadır. Ancak, özellikle pluripotent hücrelerin teratom oluşturma riski, genetik stabilite sorunları ve bağışıklık sisteminin nakledilen hücreleri reddetme olasılığı klinik uygulamaların önündeki temel engellerdir. Kök hücrelerin tedavideki güvenliğini optimize etmek için daha kapsamlı preklinik çalışmalara ve yeni biyoteknolojik stratejilere ihtiyaç duyulmaktadır.

Keywords

Stem cells: Definition, characteristics, classification, sources and ethical approaches

Abstract

Aim: Stem cells are undifferentiated progenitor cells characterized by their unique capacity for self-renewal and the potential to differentiate into various specialized cell types under appropriate conditions. These cells are distributed across various biological stages and tissues, including embryonic structures, bone marrow, umbilical cord blood, and adult organs. Through mechanisms such as asymmetric division, stem cells play a central role in maintaining the progenitor pool while facilitating tissue repair and homeostatic regeneration. Materials and Methods: This study classifies stem cells based on two primary criteria: differentiation potential (totipotent, pluripotent, multipotent, oligopotent, and unipotent) and biological origin (embryonic, adult, and fetal sources). Furthermore, the biological characteristics of induced pluripotent stem cells and cancer stem cells are analyzed. The study evaluates specific surface markers- such as CD34, CD133, and CD44-used for identification as well as the internal and external regulators governing symmetric and asymmetric division modes. Conclusions: Stem cells offer revolutionary therapeutic potential in regenerative medicine and tissue engineering for treating degenerative conditions, including leukemia, Parkinson's disease, diabetes, and myocardial injury. Induced pluripotent stem cells technology presents a significant advancement by addressing the ethical concerns associated with embryonic stem cells and reducing the risk of immune rejection through patient-specific applications. However, critical challenges such as the risk of teratoma formation, genomic instability, and potential immune responses remain primary hurdles for clinical translation. To optimize the safety and efficacy of these therapies, comprehensive preclinical research and the development of novel biotechnological strategies are essential.

Keywords

Supporting Institution

None

Ethical Statement

This study is a review/literature analysis and does not require ethics committee approval.

References

Tian Z, Yu T, Liu J, Wang T, Higuchi A. Introduction to stem cells. Prog Mol Biol Transl Sci. 2023;199:3–32. doi:10.1016/bs.pmbts.2023.02.012.
Can A. Kök hücre: biyolojisi, türleri ve tedavide kullanımları. 2. baskı. Ankara: Akademisyen Kitabevi; 2021.
Sağsöz H, Ketani MA. Kök hücreler. Dicle Üniv Vet Fak Derg. 2008;1(2):29–33.
Chen C, Fingerhut JM, Yamashita YM. The ins(ide) and outs(ide) of asymmetric stem cell division. Curr Opin Cell Biol. 2016;43:1–6. doi:10.1016/j.ceb.2016.06.001.
Shahriyari L, Komarova NL. Symmetric vs. asymmetric stem cell divisions: an adaptation against cancer? PLoS One. 2013;8(10):e76195. doi:10.1371/journal. pone.0076195.
Mesfin FM, Manohar K, Hunter CE, Shelley WC, Brokaw JP, Liu J, et al. Stem cell–derived therapies to preserve and repair the developing intestine. Semin Perinatol. 2023;47(3):151727. doi:10.1016/j.semperi.2023.151727.
Zakrzewski W, Dobrzyński M, Szymonowicz M, Rybak Z. Stem cells: past, present, and future. Stem Cell Res Ther. 2019;10(1):68. doi:10.1186/s13287-019-1165-5.
Hussen BM, Taheri M, Yashooa RK, Abdullah GH, Abdullah SR, Kheder RK, et al. Revolutionizing medicine: recent developments and future prospects in stem-cell therapy. Int J Surg. 2024;110(12):8002–24. doi:10.1097/JS9.0000000000002109.

Shevyrev D, Tereshchenko V, Berezina TN, Rybtsov S. Hematopoietic stem cells and the immune system in development and aging. Int J Mol Sci. 2023;24(6):5862. doi:10.3390/ijms24065862.
Carroll D, St Clair DK. Hematopoietic stem cells: normal versus malignant. Antioxid Redox Signal. 2018;29(16):1612–32. doi:10.1089/ars.2017.7326.
Kwon M, Kim BS, Yoon S, Oh SO, Lee D. Hematopoietic stem cells and their niche in bone marrow. Int J Mol Sci. 2024;25(13):6837. doi:10.3390/ijms25136837.
Kandarakov O, Belyavsky A, Semenova E. Bone marrow niches of hematopoietic stem and progenitor cells. Int J Mol Sci. 2022;23(8):4462. doi:10.3390/ijms23084462.
Lan T, Luo M, Wei X. Mesenchymal stem/stromal cells in cancer therapy. J Hematol Oncol. 2021;14:195. doi:10.1186/s13045-021-01208-w.
Çakar N. Embriyodan erişkine kök hücreler. Bilim ve Teknik. 2010;43(702):42–45.
Beumer J, Clevers H. Hallmarks of stemness in mammalian tissues. Cell Stem Cell. 2024;31(2):147–61. doi:10.1016/j.stem.2023.12.006.
Walia B, Satija N, Tripathi RP, et al. Induced pluripotent stem cells: fundamentals and applications of the reprogramming process and its ramifications on regenerative medicine. Stem Cell Rev Rep. 2012;8:100–15.
Müller LUW, Daley GQ, Williams DA. Upping the ante: recent advances in direct reprogramming. Mol Ther. 2009;17(6):947–53. doi:10.1038/mt.2009.72.
Shamsian A, Sahebnasagh R, Norouzy A, Hussein SH, Ghahremani MH, Azizi Z. Cancer cells as a new source of induced pluripotent stem cells. Stem Cell Res Ther. 2022;13:459. doi:10.1186/s13287-022-03179-w.
Bjerkvig R, Tysnes BB, Aboody KS, Najbauer J, Terzis AJ. The origin of the cancer stem cell: current controversies and new insights. Nat Rev Cancer. 2005;5(11):899–904.
Marotta LL, Polyak K. Cancer stem cells: a model in the making. Curr Opin Genet Dev. 2009;19(1):44–50. doi:10.1016/j.gde.2008.12.003.
Hope KJ, Jin L, Dick JE. Acute myeloid leukemia originates from a hierarchy of leukemic stem cell classes that differ in self-renewal capacity. Nat Immunol. 2004;5(7):738–43.
Kucia M, Ratajczak MZ. Stem cells as a two-edged sword—from regeneration to tumor formation. J Physiol Pharmacol. 2006;57(Suppl 7):5–16.
Bisht S, Nigam M, Kunjwal SS, Mishra AP, Sharifi-Rad J. Cancer stem cells: from an insight into the basics to recent advances and therapeutic targeting. Stem Cells Int. 2022;2022:9653244. doi:10.1155/2022/9653244.
Rahman M, Jamil HM, Akhtar N, Rahman KMT, Islam R, Asaduzzaman SM. Stem Cell and Cancer Stem Cell: A Tale of Two Cells. Progress in Stem Cell, 2016;3:97–108. doi:10.15419/psc.v3i02.124.
Avcı M. Kök hücre: tanımı ve genel özellikleri, kullanım alanları, tarihi, yüzey belirteçleri. Arch Med Rev J. 2022;31(2):87–93. doi:10.17827/aktd.1063647.
Bulut O, Belge A. Kök hücreler ve veteriner hekimlikte kullanım alanları. Harran Üniv Vet Fak Derg. 2020;9:86–89.
Deacon T, Schumacher J, Dinsmore J, Thomas C, Palmer P, Kott S, et al. Histological evidence of fetal pig neural cell survival after transplantation into a patient with Parkinson’s disease. Nat Med. 1997;3:350–3.
Petrus-Reurer S, Romano M, Howlett S, et al. Immunological considerations and challenges for regenerative cellular therapies. Commun Biol. 2021;4:798.
Cieśla J, Tomsia M. Cadaveric stem cells: their research potential and limitations. Front Genet. 2021;12:798161. doi:10.3389/fgene.2021.798161.
Aydın E. Kök hücre çalışmalarında etik. Hacettepe Tıp Derg. 2005;36(4):198–202.
Marks, H., Kalkan, T., Menafra, R., Denissov, S., Jones, K., Hofemeister, H., Stunnenberg, H. G. (2012). The transcriptional and epigenomic foundations of ground state pluripotency. Cell, 149(3), 590-604.
Hasin, Y., Seldin, M., & Lusis, A. (2017). Multi-omics approaches to disease. Genome biology, 18(1), 83.
Lancaster, M. A., & Knoblich, J. A. (2014). Organogenesis in a dish: modeling development and disease using organoid technologies. Science, 345(6194), 1247125.
Sato, T., Vries, R. G., Snippert, H. J., Van De Wetering, M., Barker, N., Stange, D. E.,& Clevers, H. (2009). Single Lgr5 stem cells build crypt-villus structures in vitro without a mesenchymal niche. Nature, 459(7244), 262-265.
Doudna, J. A., & Charpentier, E. (2014). The new frontier of genome engineering with CRISPR-Cas9. Science, 346(6213), 1258096.
Schwank, G., Koo, B. K., Sasselli, V., Dekkers, J. F., Heo, I., Demircan, T., Clevers, H. (2013). Functional repair of CFTR by CRISPR/Cas9 in intestinal stem cell organoids of cystic fibrosis patients. Cell stem cell, 13(6), 653-658.

Details

Primary Language

English

Subjects

Clinical Sciences (Other)

Journal Section

Review

Authors

Zeynep Konukcu Mehdılı
0000-0002-7854-3131
Türkiye

Özgün Selim Germiyan
0000-0001-7077-0965
Türkiye

Afig Huseyinov Berdeli
0000-0001-5627-6100
Türkiye

Yiğit Uyanıkgil ^*
0000-0002-4016-0522
Türkiye

Publication Date

June 10, 2026

Submission Date

January 24, 2026

Acceptance Date

March 13, 2026

Published in Issue

Year 2026 Volume: 65 Number: 2

DOI

https://doi.org/10.19161/etd.1870790

IZ

https://izlik.org/JA89ST66GW

Cite

RIS / Bibtex

APA

Konukcu Mehdılı, Z., Germiyan, Ö. S., Berdeli, A. H., & Uyanıkgil, Y. (2026). Stem cells: Definition, characteristics, classification, sources and ethical approaches. Ege Tıp Dergisi, 65(2), 357-368. https://doi.org/10.19161/etd.1870790

AMA

1.Konukcu Mehdılı Z, Germiyan ÖS, Berdeli AH, Uyanıkgil Y. Stem cells: Definition, characteristics, classification, sources and ethical approaches. EJM. 2026;65(2):357-368. doi:10.19161/etd.1870790

Chicago

Konukcu Mehdılı, Zeynep, Özgün Selim Germiyan, Afig Huseyinov Berdeli, and Yiğit Uyanıkgil. 2026. “Stem Cells: Definition, Characteristics, Classification, Sources and Ethical Approaches”. Ege Tıp Dergisi 65 (2): 357-68. https://doi.org/10.19161/etd.1870790.

EndNote

Konukcu Mehdılı Z, Germiyan ÖS, Berdeli AH, Uyanıkgil Y (June 1, 2026) Stem cells: Definition, characteristics, classification, sources and ethical approaches. Ege Tıp Dergisi 65 2 357–368.

IEEE

[1]Z. Konukcu Mehdılı, Ö. S. Germiyan, A. H. Berdeli, and Y. Uyanıkgil, “Stem cells: Definition, characteristics, classification, sources and ethical approaches”, EJM, vol. 65, no. 2, pp. 357–368, June 2026, doi: 10.19161/etd.1870790.

ISNAD

Konukcu Mehdılı, Zeynep - Germiyan, Özgün Selim - Berdeli, Afig Huseyinov - Uyanıkgil, Yiğit. “Stem Cells: Definition, Characteristics, Classification, Sources and Ethical Approaches”. Ege Tıp Dergisi 65/2 (June 1, 2026): 357-368. https://doi.org/10.19161/etd.1870790.

JAMA

1.Konukcu Mehdılı Z, Germiyan ÖS, Berdeli AH, Uyanıkgil Y. Stem cells: Definition, characteristics, classification, sources and ethical approaches. EJM. 2026;65:357–368.

MLA

Konukcu Mehdılı, Zeynep, et al. “Stem Cells: Definition, Characteristics, Classification, Sources and Ethical Approaches”. Ege Tıp Dergisi, vol. 65, no. 2, June 2026, pp. 357-68, doi:10.19161/etd.1870790.

Vancouver

1.Zeynep Konukcu Mehdılı, Özgün Selim Germiyan, Afig Huseyinov Berdeli, Yiğit Uyanıkgil. Stem cells: Definition, characteristics, classification, sources and ethical approaches. EJM. 2026 Jun. 1;65(2):357-68. doi:10.19161/etd.1870790