The most interesting part of the experimental NUL-5 hair-growth blend is not that it contains one fashionable signalling molecule. It is that its two components may influence three connected layers of follicle biology at once: the growth instructions sent by hepatocyte growth factor (HGF), the anagen switch controlled by DKK1 and Wnt/beta-catenin, and the physical extracellular matrix that helps the dermal papilla retain its hair-inductive identity.
That combination could matter because a hair follicle is not simply a tube that produces keratin. It is a cycling mini-organ. At its base, dermal-papilla cells exchange signals with rapidly dividing matrix keratinocytes. Above them, the connective-tissue sheath and bulge niche help coordinate stem-cell activation. When these conversations weaken, the follicle can leave anagen, enter catagen and return with a thinner fibre.
In an ex vivo study using living follicles microdissected from three healthy human scalp donors, NUL-5 reportedly prolonged anagen, increased hair-matrix proliferation, strengthened dermal-papilla alkaline-phosphatase activity, increased elastin in key follicular compartments, lowered the catagen promoter TGF-beta2 and reduced secretion of the Wnt inhibitor DKK1. Those observations suggest a coherent mechanism, but they remain laboratory evidence. No published randomized clinical trial has yet shown that NUL-5 regrows hair on a balding human scalp.
The Dermal Papilla Is the Follicle’s Signalling Command Centre
The dermal papilla is a compact cluster of specialised mesenchymal cells enclosed by the hair bulb. It does not become the hair shaft. Instead, it tells neighbouring epithelial cells when to proliferate, what type of fibre to build and how large the growing follicle should become.
Dermal-papilla size is linked to hair-follicle size, and its volume reflects both cell number and extracellular-matrix volume. During androgenetic alopecia, dermal-papilla signalling becomes less supportive of growth. Androgen activity shifts the balance between Wnt agonists and antagonists, while factors such as DKK1 can suppress stem-cell differentiation and promote damaging signals in follicular keratinocytes.
This is why NUL-5’s reported changes in alkaline phosphatase and versican are worth watching. Both are used as markers of a more inductive dermal-papilla phenotype. They do not prove new hair growth in a patient, but they suggest the papilla behaved more like the signalling hub of an actively growing follicle during the short organ-culture experiment.
Mechanism 1: HGF Activates the c-Met Growth Conversation
HGF is a paracrine growth factor. In simple terms, one cell releases it to influence nearby cells carrying its receptor, c-Met. Research on human follicles has found HGF production in follicular papilla cells and c-Met responsiveness in epithelial compartments including the matrix.
Earlier human organ-culture experiments showed that HGF increased hair-follicle elongation and stimulated DNA synthesis in hair-bulb-derived keratinocytes. More recent work has also identified dermal adipose cells as a source of HGF and found c-Met expression in both the hair matrix and dermal papilla. This places HGF at an epithelial-mesenchymal junction where growth instructions can be translated into matrix-cell proliferation and shaft production.
NUL-5 supplied HGF at 1 ng/mL. The working hypothesis is that this signal helped maintain the proliferative matrix population. However, HGF is not automatically better at higher doses, and a concentration that works around a dissected follicle in culture may not reach the correct compartment after topical application. Protein stability, skin penetration and receptor exposure are major unanswered delivery questions.
Mechanism 2: Lower DKK1 May Release the Wnt Anagen Brake
Canonical Wnt/beta-catenin signalling is central to follicle formation, dermal-papilla identity and the transition into active growth. When Wnt ligands activate the pathway, beta-catenin accumulates and enters the nucleus, where it changes the expression of genes that support follicular induction and anagen.
DKK1 is one of the pathway’s most important extracellular brakes. It interferes with Wnt-receptor activation. In balding human dermal-papilla cells, dihydrotestosterone can increase DKK1, and laboratory studies have found more DKK1 in bald scalp than in haired scalp. DKK1 released from these cells can also promote apoptosis in neighbouring follicular keratinocytes.
The NUL-5 experiment reported lower DKK1 secretion. That could allow endogenous Wnt signals to operate with less opposition, helping the papilla maintain anagen-supportive gene expression. The accompanying increase in alkaline phosphatase and trend toward higher versican fit that interpretation because Wnt activity helps preserve the specialised identity of dermal-papilla cells.
But this remains an inference from correlated markers. The abstract did not establish that blocking Wnt signalling erased NUL-5’s effect, which would provide stronger evidence that Wnt activation is necessary rather than merely associated with the response.
Mechanism 3: Tropoelastin May Repair the Mechanical Niche
Tropoelastin is the soluble precursor from which elastic fibres are assembled. Elastic tissue is not distributed uniformly around a follicle. Histological work has described an elastic coat near the follicular isthmus and an elastin-like structure at the neck of the dermal papilla that is rebuilt during each hair cycle.
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In the NUL-5 study, elastin was concentrated around the bulge connective-tissue sheath, dermal cup and dermal-papilla stalk. Treatment increased elastin expression in the dermal papilla and the connective-tissue sheath around the bulge. This could improve the physical scaffold that maintains cell position, tension and communication between epithelial and mesenchymal compartments.
That possibility has become more plausible as hair research has moved beyond chemical signals alone. Recent work describes fibroblast populations that sense extracellular-matrix viscoelasticity and remodel the mechanical niche beneath the dermal papilla to support stem-cell activation. The broader lesson is that a follicle’s matrix is active biological infrastructure, not inert packaging.
Still, increased elastin staining does not prove that the new material formed mature, correctly organised elastic fibres or that it improved follicle mechanics. Those questions require structural imaging, biomechanical testing and longer experiments.
Mechanism 4: Reduced TGF-Beta2 May Delay Catagen
TGF-beta2 helps initiate catagen in human hair follicles. In organ culture, increasing this signal produces regression-like changes, while antagonising TGF-beta can delay catagen and support elongation. NUL-5 reduced TGF-beta2 expression in the outer root sheath, providing a second route by which treated follicles may have remained in anagen.
This matters because growth and regression are not controlled by one on/off molecule. A follicle can receive simultaneous pro-growth and pro-catagen instructions. HGF-driven matrix proliferation would be less useful if TGF-beta2 were still pushing the organ into programmed regression. The reported combination of stronger growth signalling and weaker catagen signalling is therefore more persuasive than either marker alone.
How the Three Mechanisms May Work Together
The most reasonable integrated model is a feedback loop:
- HGF activates c-Met-responsive matrix and papilla cells, supporting proliferation and epithelial-mesenchymal communication.
- Reduced DKK1 permits stronger endogenous Wnt/beta-catenin activity, helping the dermal papilla retain its inductive state.
- Added tropoelastin supports an extracellular environment in which papilla, sheath and bulge cells can maintain their spatial relationships.
- Lower TGF-beta2 reduces pressure toward catagen, giving the pro-growth program more time to operate.
- A healthier papilla then produces more supportive signals for matrix cells, potentially reinforcing anagen.
This is a biologically plausible interpretation of the reported markers, not a demonstrated chain of causation. The experiment was short, used healthy donor follicles and did not model scalp-level delivery, androgen exposure or progressive miniaturisation.
What Is Proven, Plausible and Still Unknown?
- Proven in this experiment: Under the reported ex vivo conditions, treated human follicles remained in anagen longer and showed significant changes in matrix proliferation, alkaline-phosphatase activity, elastin expression, DKK1 secretion and TGF-beta2 expression.
- Biologically plausible: HGF/c-Met signalling, reduced Wnt inhibition, improved dermal-papilla identity and extracellular-matrix support could cooperate to maintain growth.
- Not proven: Topical scalp penetration, regrowth in androgenetic alopecia, an effective human dose, durability after treatment stops, superiority to minoxidil or safety during long-term use.
Practical Takeaways
Do not inject, microneedle or compound research-grade HGF. Growth factors require controlled manufacturing and safety evaluation. A cosmetic that mentions elastin or HGF is also not automatically equivalent to the laboratory formulation.
For now, the useful action is to watch for a registered randomized trial that measures terminal-hair density, shaft diameter, standardized photographs and adverse events for at least six months. The strongest design would also collect scalp biomarkers to test whether clinical responders actually show the DKK1, Wnt, TGF-beta2 and extracellular-matrix changes proposed here.
Sources: NUL-5 human follicle conference abstract; HGF and human hair growth in vitro; dermal adipose HGF and c-Met in human follicles; DHT-inducible DKK1 in balding dermal papilla; 2026 review of endogenous Wnt antagonists in androgenetic alopecia; TGF-beta2 and human catagen induction; 2026 extracellular-matrix mechanosensing and hair regeneration research.