What Is Stem Cell Factor and Why Is It Used in Hair Growth Treatments?

When we encounter the term “stem cell factor” in the context of hair growth treatments, what we really need to understand is whether this molecule has a proven, clinically meaningful role in treating hair loss or whether its use is largely based on indirect biological reasoning. Stem Cell Factor, usually abbreviated as SCF, is not a cosmetic invention nor a marketing term. It is a naturally occurring protein that has been studied for decades in immunology, hematology, and developmental biology. However, its translation into hair growth treatments requires careful examination of what the research actually shows and, just as importantly, what it does not show.

Stem Cell Factor Explained in Plain Language

Stem Cell Factor is a signaling protein produced by various cells in the body, including skin cells and connective tissue cells. In biological terms, it is classified as a cytokine and a growth factor. This means it acts as a chemical messenger, allowing cells to communicate with each other. SCF exerts its effects by binding to a specific receptor on the surface of certain cells called c-Kit, also known as CD117. Once SCF binds to c-Kit, it triggers internal cellular processes that support cell survival, movement, and division.

From a technical standpoint, this signaling system is essential for several normal biological processes. SCF–c-Kit signaling is required for the development of blood-forming stem cells in the bone marrow, the survival and migration of melanocytes (the cells that produce pigment in skin and hair), and the maintenance of specific stem cell populations in different tissues. These roles have been well established through laboratory experiments and animal models long before SCF was ever mentioned in aesthetic medicine.

Why Hair Researchers Became Interested in SCF

Hair follicles are complex mini-organs that rely on tightly regulated signaling between multiple cell types. At the base of each follicle are hair follicle stem cells, which are responsible for initiating new hair growth cycles. These stem cells do not function independently. They respond to chemical signals from surrounding cells, including dermal papilla cells and epidermal cells.

Researchers became interested in SCF because the c-Kit receptor is expressed in parts of the hair follicle, particularly in melanocytes and in some progenitor cell populations. Early histological studies of human scalp tissue showed that normal, non-balding hair follicles express SCF and c-Kit, whereas follicles affected by androgenetic alopecia may show altered expression of these signals. This observation raised an important scientific question: is SCF actively driving hair growth, or is it simply one of many background signals present in healthy follicles?

What the Research Actually Shows About SCF and Hair Follicles

One of the most frequently cited human studies examining SCF in hair follicles was published in the Journal of Endocrinology in 2008. In this study, researchers analyzed scalp biopsy samples from individuals with androgenetic alopecia and compared them with samples from non-balding scalp areas. The method involved immunohistochemical staining, which allows researchers to visually detect specific proteins in tissue samples. The population consisted of adult human scalp tissue samples, and the evaluation focused on protein expression rather than hair growth outcomes.

The researchers found that SCF and c-Kit were present in human hair follicles and that their expression appeared reduced in balding follicles. The duration of the study was limited to tissue analysis, and no follow-up was performed to assess hair regrowth. The main criticism of this study is that it was observational. It did not test whether increasing SCF levels would reverse hair loss, nor did it establish a cause-and-effect relationship. Reduced SCF could be a consequence of follicle miniaturization rather than a cause.

Additional insight comes from animal studies. In a well-known experimental study published in the FASEB Journal in 2001, researchers investigated the role of SCF–c-Kit signaling in hair pigmentation using mouse models. The study involved genetically modified mice with disrupted c-Kit signaling. The evaluation method included visual assessment of hair color and microscopic analysis of hair follicles over multiple hair cycles. The study duration covered several hair growth cycles in mice.

The results demonstrated that SCF–c-Kit signaling is essential for maintaining hair pigmentation by supporting melanocyte survival. However, hair shaft production itself was not significantly increased by SCF signaling alone. The critical limitation here is species difference. Mouse hair biology differs from human hair biology, and pigmentation maintenance is not the same as stimulating new hair growth.

The Role of SCF in “Stem Cell” Hair Treatments

When we look at modern hair growth treatments marketed as “stem cell therapies,” it becomes clear that SCF is rarely used in isolation. These treatments typically involve stem cell–derived conditioned media, exosomes, or growth factor cocktails. SCF may be present among dozens of other signaling molecules, including vascular endothelial growth factor (VEGF), fibroblast growth factors (FGFs), and insulin-like growth factors (IGFs).

From a scientific perspective, this makes it difficult to attribute any observed hair-related effects specifically to SCF. In a 2024 preclinical study published in Stem Cell Research & Therapy, researchers investigated the effects of mesenchymal stem cells derived from human umbilical cords on hair growth in mice. The method involved injecting stem cell–derived products into the skin of mice and evaluating hair cycle progression through histological analysis. The population consisted entirely of animal subjects, and the study duration spanned several weeks.

While the study reported increased activation of hair follicle stem cells and earlier entry into the growth phase, SCF was only one of many molecules involved. The authors themselves acknowledged that the complex mixture of signaling factors prevents isolation of SCF’s specific contribution. This represents a major limitation when such findings are later cited to support human cosmetic treatments.

From a regulatory standpoint, this is where caution becomes essential. As of now, neither the U.S.

Food and Drug Administration nor other major health authorities have approved SCF as a standalone treatment for hair loss. The FDA has repeatedly stated that most stem cell–based cosmetic treatments lack sufficient clinical evidence and should be considered experimental unless proven otherwise through controlled human trials.

This matters because many claims surrounding SCF in hair treatments are based on biological plausibility rather than clinical proof. Biological plausibility means that a mechanism exists in theory, not that it has been demonstrated to work in patients. In medicine, these are not equivalent.

What We Need to Know Before Accepting SCF as a Hair Growth Solution

When we evaluate SCF critically, the central issue is not whether it plays a role in hair follicle biology, because it clearly does. The real question is whether manipulating SCF levels in human scalps leads to meaningful, measurable, and lasting hair regrowth. At present, the research does not provide that answer. Most available studies are either tissue-based, animal-based, or involve complex stem cell products where SCF is only one variable among many. There is a lack of long-term, placebo-controlled human trials evaluating SCF specifically for hair loss. Without this level of evidence, any clinical use of SCF remains speculative rather than established.

*Stem Cell Factor is an essential biological molecule with well-documented roles in cell survival, pigmentation, and stem cell maintenance. *

Its presence in hair follicles explains why it appears in discussions about hair regeneration. However, current research does not support SCF as a proven or independent hair growth treatment in humans. Its use in hair therapies is based more on theoretical biology and indirect evidence than on robust clinical trials.

Understanding this distinction allows us to interpret claims about SCF with clarity rather than optimism. In hair loss research, understanding mechanisms is only the first step. Demonstrating real-world clinical benefit is the standard that has not yet been met.

References

Botchkareva, N. V., Khlgatian, M., Longley, B. J., Botchkarev, V. A., & Gilchrest, B. A. (2001). SCF/c-kit signaling is required for cyclic regeneration of the hair pigmentation unit. The FASEB Journal, 15(3), 645–658. https://faseb.onlinelibrary.wiley.com/doi/10.1096/fj.00-0368com

Randall, V. A., Hibberts, N. A., Thornton, M. J., Merrick, A. E., Hamada, K., Kato, S., Jenner, T. J., & de Oliveira, I. O. (2008). Stem cell factor/c-kit signaling in normal and androgenetic alopecia hair follicles. Journal of Endocrinology, 197(1), 11–23. https://joe.bioscientifica.com/view/journals/joe/197/1/11.xml

Li, Y., Zhang, D., Chen, C., Ruan, Z., Li, Y., & Huang, Y. (2024). Human umbilical cord–derived mesenchymal stem cells promote hair regeneration via activation of hair follicle stem cells. Stem Cell Research & Therapy, 15, 89. https://stemcellres.biomedcentral.com/articles/10.1186/s13287-024-03789-6

U.S. Food and Drug Administration. (2023). Consumer alert on regenerative medicine products including stem cell therapies. https://www.fda.gov/vaccines-blood-biologics/cellular-gene-therapy-products/consumer-alert-regenerative-medicine-products-including-stem-cell-therapies