Low-dose Rapamycin may promote hair regrowth

What is Rapamycin?

Rapamycin is a drug that was originally used to prevent organ transplant rejection. It works by inhibiting a protein complex called mTOR (mechanistic Target of Rapamycin), which plays a major role in cell growth, aging, and metabolism.

How Could Rapamycin Help Hair Growth?

There’s early evidence that mTOR inhibition may stimulate dormant or slow stem cells in hair follicles, helping restart hair growth cycles.
Researchers aimed to create a better way to deliver rapamycin for treating hair loss. Existing treatments (like minoxidil or finasteride) have absorption issues or side effects. So, they made injectable microdepots (RAPMD) using rapamycin and a slow-release material called PLGA.

Slows Aging of Hair Follicles

mTOR signaling is associated with aging. Inhibiting it may help “rejuvenate” aging hair follicles, keeping them in a healthier, more active state longer.

Promotes Autophagy (Cell Cleanup)

By inhibiting mTOR, rapamycin boosts autophagy—a kind of cellular housekeeping. This may help clear out damaged components in hair follicle cells, potentially improving their function.

Reduces Inflammation

Chronic inflammation around hair follicles can contribute to hair thinning. Rapamycin has anti-inflammatory effects, which might help calm down that environment.

Stimulates Hair Follicle Stem Cells

There’s early evidence that mTOR inhibition may stimulate dormant or slow stem cells in hair follicles, helping restart hair growth cycles.

What They Did:

• Made tiny rapamycin-filled particles (~6 μm in size) that release the drug slowly over 35 days.
  
• Injected them into mice with shaved backs.
  
• Compared different doses and checked for hair growth, follicle activation, and genetic changes.
  

What They Found:

1. Sustained low-dose rapamycin (especially 0.2 μg) was most effective at:
   • Triggering hair follicles to enter the growth phase (anagen)
     
   • Activating autophagy (cell cleanup)
     
   • Stimulating the Wnt/β-catenin pathway—important for hair follicle cell growth.
     
2. Higher doses didn’t work as well and might even reduce hair regrowth, possibly due to over-inhibition of cell processes.
   
3. Blocking autophagy canceled out rapamycin’s benefits, proving it’s a key mechanism for hair growth.
   

 Conclusion:

Injecting low-dose, slow-releasing rapamycin microdepots helps stimulate hair regrowth by:

• Activating follicle stem cells
  
• Enhancing autophagy
  
• Boosting the Wnt/β-catenin pathway
  

This method could be a promising new treatment for hair loss with less frequent dosing and better results.