TLDR 7-Phloroeckol from brown algae may help hair grow.
The study from 2014 investigated the effects of 7-phloroeckol, a compound from marine brown algae, on hair growth using human hair follicles in vitro. It was found that 7-phloroeckol significantly increased the proliferation of human dermal papilla cells (DPCs) and outer root sheath (ORS) cells, as well as the elongation of the hair shaft. Additionally, the compound boosted insulin-like growth factor (IGF)-1 mRNA expression and protein concentration in DPCs. The treatment with 7-phloroeckol led to a significant increase in IGF-1 mRNA expression (4.98- and 5.37-fold) and IGF-1 secretion (783 and 841 pg/ml) compared to the control (483 pg/ml), while it did not significantly affect the expression of other growth factors such as VEGF, KGF, and HGF mRNA. These results suggest that 7-phloroeckol has potential as a treatment for hair loss and for promoting hair growth, although the exact number of hair follicles tested was not specified. The research was funded by the Marine Bioprocess Research Center of the Marine Biotechnology Program in Korea.
34 citations,
June 2009 in “British journal of dermatology/British journal of dermatology, Supplement” Vitamin C derivative helps hair grow longer by making cells produce a growth factor through a specific cellular pathway.
171 citations,
July 2007 in “Journal of Investigative Dermatology” A substance called DKK-1 increases in balding areas and causes hair cells to die when exposed to DHT.
[object Object] 
13 citations,
June 2007 in “Journal of Dermatological Science” Researchers created a cell line to study hair growth and found specific genes affected by dihydrotestosterone.
190 citations,
October 2002 in “The FASEB journal” Androgens may cause hair loss by increasing TGF-beta1 from scalp cells, which inhibits hair cell growth.
18 citations,
December 2020 in “Frontiers in cell and developmental biology” miR-140-5p in certain cell vesicles helps hair growth by boosting cell proliferation.
[object Object] 
5 citations,
November 2020 in “Frontiers in Cell and Developmental Biology” The "Two-Cell Assemblage" assay is a new, simple method to identify substances that may promote hair growth.
17 citations,
May 2014 in “Naunyn-Schmiedeberg's Archives of Pharmacology” 7-Phloroeckol from brown algae may help hair grow.
61 citations,
October 1996 in “Development” Hair growth can be stimulated by combining certain skin cells, which can rejuvenate old cells and cause them to specialize in hair follicle creation.
94 citations,
February 1994 in “The journal of investigative dermatology/Journal of investigative dermatology” EGF makes hair follicles grow longer but stops hair production.
