More than 60% of surveyed individuals report willingness to consider stem cell-derived therapies (1), reflecting a growing adaptation to regenerative medicine. Beneath this clinical momentum lies a biological reality: function of numerous cell types and stem cells is deeply influenced by oxygen tension, known to be lower within the body. A controlled shift in oxygen levels, specifically through hypoxia culture, can meaningfully alter proliferation and long-term viability. Understanding this shift is contributory toward the translation of laboratory findings into reliable therapeutic strategies.
Unlike the majority of mature and fully differentiated cells, stem cell lines use mitosis to continuously replenish and repair, exploiting asymmetric division to control cell fate. © Green Elephant Biotech.
Contrary to common assumptions, physiological in vivo environments often expose stem cells to relatively low oxygen (O₂) tensions, with a number of cell types inclusive of stem cells favoring this microenvironment. The cause thereof being the perspective on hypoxic niches as fundamental for maintaining stemness and preventing premature differentiation. In contrast, standard in vitro normoxia (approximately 21% O₂) can induce oxidative stress and sometimes, senescence.
The distinction within hypoxia culture depends on dissolved O₂ concentration. Moderate hypoxia typically refers to O₂ levels between 1–3%, which remain compatible with cellular metabolism. Severe hypoxia — at or below 0.1% O₂ — approaches pathological thresholds associated with irreversible cellular damage (2).
In laboratory settings, moderate hypoxia can be introduced intentionally during expansion or differentiation phases. A common method involves replacing atmospheric air with a controlled gas mixture containing 95% nitrogen (N₂) and 5% carbon dioxide (CO₂) (3). Today, hypoxia-preconditioned stem cells have been evaluated in cardiac, musculoskeletal, neural, along with bone regeneration models and beyond (2).
Despite expanding literature, consensus regarding the definitive effects of hypoxia culture remains elusive. This article therefore examines both regenerative and potentially deleterious outcomes associated with O₂ levels at and below 3%, highlighting the nuanced interplay between hypoxia and stem cells.
From viability to proliferative marker expression, hypoxia and stem cell health intertwine deeply
Given the growing interest in hypoxia culture, numerous studies have investigated optimal oxygen parameters across stem cell types. For example, human mesenchymal stem cells (MSCs) cultured at 5% O₂ demonstrated a modest increase in proliferation compared with normoxic 21% O₂ conditions (3).
Similarly, muscle-derived stem/progenitor cells (MDSPCs) exhibited enhanced self-renewal and pluripotency under 3% O₂. Hypoxic conditioning led to statistically significant increases in mRNA expression of Sox2 (1.5-fold) and Nanog (1.7-fold), typically largely reduced in its expression, indicating transcriptional regulation of stemness-associated pathways (4).
However, duration of exposure appears critical. Short-term hypoxia limited to 12 hours did not yield comparable effects, underscoring the time-sensitive nature of hypoxia culture. Furthermore, O₂ requirements are not universal across cell types. Dental pulp stem cells (DPSCs), while exhibiting altered Sox2 and Nanog expression, showed significantly lower proliferation at both 3% and 20% O₂ when compared to 5% O₂ (5).
When combined, these findings reinforce that hypoxia and stem cells are mechanistically intertwined. Moderate hypoxia can preserve undifferentiated states and promote self-renewal, but the magnitude and direction of effects depend strongly on O₂ concentration, exposure duration, and experimental design evaluating the phenomenon.
There is only one step between benefit and irreversible damage in a hypoxia culture
Hypoxia is also associated with pathological states, including ischemia, where O₂ deprivation brings more harm than good in any cell type. Severe short-term hypoxia has been shown to reduce induced mesenchymal stem cell (iMSC) viability. In this case, expression of Bcl2, a key regulator of apoptosis resistance, was reduced 2-fold under hypoxic conditions, demonstrating increased susceptibility to cell death (6).
Hypoxia-inducible factors (HIFs) further complicate interpretation. While HIF-mediated pathways enable cellular adaptation to low O₂ environments, they also intersect with inflammatory and oncogenic signaling networks. Clinical correlations between higher concentrations of HIF-1α or HIF-2α, and patient mortality in solid tumors highlight the duality of hypoxic regulation (7).
At the transcriptional level, regulators, such as Tfcp2l1, aid in illustrating this delicate balance in more detail. O₂ deprivation can stimulate Tfcp2l1 expression and activate pathways associated with prolonged self-renewal or immortalization. Conversely, its downregulation due to O₂ deprivation too severe may promote senescence (8).
These molecular hypotheses underscore that hypoxia culture operates within a narrow therapeutic window. While adaptive mechanisms may enhance regenerative potential, prolonged or excessive hypoxia can trigger maladaptive or even malignant pathways (2).
Clinical use of hypoxic conditioning does not have to be fiction, although we do not know everything just yet
Hypoxic conditions can be established using dedicated hypoxia chambers or controlled gas mixtures. Chambers allow precise regulation of O₂ and N₂ concentrations, whereas chemical mimetics like cobalt chloride (CoCl₂) can stabilize HIF pathways, when dissolved in culture media and used within standard CO₂ incubators (9).
These approaches have advanced beyond laboratory investigation and into clinical evaluation. Ongoing clinical studies explore hypoxia-preconditioned MSCs in knee osteoarthritis and COVID-19. In Parkinson’s rodent models, for instance, hypoxic conditioning shifted MSC preparations toward an anti-inflammatory phenotype, subsequently improving mitochondrial function in dopaminergic neurons and enhancing motor performance (10).
Although the mechanistic framework linking hypoxia and stem cells remains incomplete, biotechnological advances — including CRISPR-Cas9 and increasingly affordable next-generation sequencing — are expected to clarify O₂-dependent regulatory networks. There is a chance that hypoxic preconditioning may help in mitigating persistent clinical challenges associated with the real-world stem cell use, including but not limited to tumorigenesis and immune rejection (11).
Hypoxia culture has emerged as a powerful, but a relatively complex to apply tool in regenerative medicine. Moderate O₂ reduction can indeed enhance stemness markers and differentiation, while prolonged hypoxia can compromise these benefits by driving undesirable pathways.
The interplay between hypoxia and stem cells is governed by finely tuned molecular regulators: HIF signaling networks and hundreds of downstream transcription factors. These mechanisms represent the foundation of both the therapeutic promise and biological risk inherent to hypoxia culture. Importantly, data from various studies are difficult to compare due to wide variations in O₂ tension, duration of conditioning, the use of MSCs from different species, and differences in media composition.
Lastly, distinct cell types vary in their capacity to tolerate hypoxia over extended periods and their adaptive potential reflects the gaseous microenvironments of their native tissues. For hypoxic conditioning to become a standardized practice, harmonization of experimental parameters and deeper mechanistic understanding will remain crucial. Among several factors, this success will depend on the availability of stable and scalable cell cultivation systems, able to consistently sustain relevant growth conditions from the bench to commercialization.
CellScrew® in stem cell cultivation?
Discover how the CellScrew® series can readily enhance and scale adherent cell cultivation in your research-to-clinical journey and beyond on our resource page.
References:
- Aboalola, D, Badraiq, H, Alsiary, R, Zakri, S, Aboulola, N, Haneef, L, Malibari, D, Baadhaim, M, Alsayegh, K, An Infodemic of Misinformation on Stem Cell Therapy Among the Population of Saudi Arabia: A Cross-Sectional Study (2022), Front Med (Lausanne) 9, pp. 1-7. doi: 10.3389/fmed.2022.789695.
- Vásquez Vélez, IC, Charris Domínguez, CM, Fernández Sánchez, MJ, Garavito-Aguilar, ZV, Hypoxia and Tissue Regeneration: Adaptive Mechanisms and Therapeutic Opportunities (2025), MDPI 26, pp. 1-43. doi: 10.3390/ijms26199272.
- Ito, A, Aoyama, T, Yoshizawa, M, Nagai, M, Tajino, J, Yamaguchi, S, Iijima, H, Zhang, X, Kuroki, H, The effects of short-term hypoxia on human mesenchymal stem cell proliferation, viability and p16INK4A mRNA expression: Investigation using a simple hypoxic culture system with a deoxidizing agent (2015), J Stem cell Regen Med 11, pp. 25-31. doi: 10.46582/jsrm.1101005.
- He, X, An, W, Liu, J, Effects of hypoxia on stemness, survival and angiogenic capacity of muscle-derived stem/progenitor cells (2021), Biochem Cell Biol 14, pp. 855-68. doi: 10.1080/26895293.2021.1977725.
- Ahmed, NM, Murakami, M, Kaneko, S, Nakashima, M, The effects of hypoxia on the stemness properties of human dental pulp stem cells (DPSCs) (2016), Sci Rep 6, pp. 1-10. doi: 10.1038/srep35476.
- Alwohoush, E, Ismail, MA, Al-Kurdi, B, Barham, R, Al Hadidi, S, Awidi, A, Ababneh, N, Effect of hypoxia on proliferation and differentiation of induced pluripotent stem cell-derived mesenchymal stem cells (2024), Heliyon 10, pp. 1-13. doi: 10.1016/j.heliyon.2024.e38857.
- Carnero, A, Lleonart, M, The hypoxic microenvironment: A determinant of cancer stem cell evolution (2015), Inside the Cell 1, pp. 96-105. doi: 10.1002/icl3.1039.
- Otero-Albiol, D, Santos-Pereira, JM, Lucena-Cacace, A, Clemente-González, Muñoz-Galvan, S, Yoshida, Y, Carnero, A, Hypoxia-induced immortalization of primary cells depends on Tfcp2L1 expression (2024), Cell Death Dis 15, pp. 1-14. doi: 10.1038/s41419-024-06567-z.
- Rana, NK, Singh, P, Koch, B, CoCl₂ simulated hypoxia induce cell proliferation and alter the expression pattern of hypoxia associated genes involved in angiogenesis and apoptosis (2019), Biol Res 52, pp. 1-13. doi: 10.1186/s40659-019-0221-z.
- Jaraba-Álvarez, WV, Uscanga-Palomeque, AC, Sanchez-Giraldo, V, Madrid, C, Ortega-Arellano, H, Halpert, K, Quintero-Gil, C, Hypoxia-induced metabolic reprogramming in mesenchymal stem cells: unlocking the regenerative potential of secreted factors (2025), Front Cell Dev Biol 13, pp. 1-7. doi: 10.3389/fcell.2025.1609082.
- Hussen, BM, Taheri, M, Yashooa, RK, Abdullah, GH, Abdullah, SR, Kheder, RK, Mustafa, SA, Revolutionizing medicine: recent developments and future prospects in stem-cell therapy (2024), Int J Surg 110, pp. 8002-24. doi: 10.1097/JS9.0000000000002109.
