L-carnitine-L-tartrate promotes human hair growth in vitro.
Level 5 - mechanism / opinion, no new human data
In vitro laboratory study on cultured human hair follicles (bench research)
PubMed 17927577 · doi:10.1111/j.1600-0625.2007.00611.x
What was done
Human scalp hair follicles in the anagen VI stage were cultured ex vivo for 9 days in the presence of 0.5 to 50 µM L-carnitine-L-tartrate (CT) or vehicle control. The authors assessed hair shaft elongation, anagen VI duration, hair matrix keratinocyte proliferation (Ki67 immunohistology), apoptosis (TUNEL assay and caspase 3/7 activity), and intrafollicular expression of TGF-beta2 and TGF-beta II receptor.
What was found
At day 9, hair follicles treated with 0.5 µM or 5 µM CT showed statistically significant stimulation of hair shaft elongation compared to vehicle controls (P < 0.05). CT prolonged anagen VI duration, upregulated Ki67 proliferation, and downregulated apoptosis by TUNEL assay (reported as P < 0.5). Immunohistology showed downregulated intrafollicular immunoreactivity for TGF-beta2 in the dermal papilla and TGF-beta II receptor in the outer root sheath and dermal papilla. Caspase 3 and 7 activities were downregulated at days 2 and 4. Exact numerical values and effect sizes were not provided in the abstract.
Why it matters
This work identifies a potential metabolic mechanism by which L-carnitine may promote follicular proliferation and delay catagen entry, offering preclinical rationale for clinical investigation in hair loss disorders.
Limits
The investigation was conducted exclusively in an ex vivo organ culture model, which cannot replicate complex in vivo physiological dynamics, follicular immunology, or tissue delivery. The abstract omits sample size (number of donors and hair follicles), exact elongation measurements, and confidence intervals.
Cited by
- supports L-carnitine supplementation has been shown to promote human hair growth in vitro.