Note: Among cell populations of HF the folloving are the most important:
- Cells of epithelial origin: matrix trichocytes [M] and ORS [outer root sheath] cells.
- Cells of dermal origin: DP fibroblasts and dermal sheath [DS] fibroblasts.
The last play in HF predominantly regulation role, while the former represent mitotically active populations.


We will review studies dealing the system, that include all 4 cells populations: M, ORS, DP and DS to answer the question whether or not it is self sufficient to regenerate functionally active HF.
1. Pioneer in this branch of experimental morphology was J. Cohen. According to his data, vibrissae HF bulb can regenerate in functionally active HF at autotransplantation. HFs bulbs were transplanted in micro-incision of ear pinna. As a result regenerated HFs underwent more that 1 growth cycle and continue to function for more than 2 years. Shafts of some of the vibrissae HFs weren’t able to penetrate healed skin surface and were identified as eminencies. At histology they look like vibrissae HFs.
But, when HFs bulbs were transplanted in micro-incision of hip skin no regeneration of vibrissae HFs was noticed even 24 weeks after transplantation. At histology 12 week after bulbs transplantation they became capsulated and thereafter degenerate. It is interesting, but in this case vascularization of implants was not reestablish.

J. COHEN. The transplantation of individual rat & guinea-pig whisker papillae . // J. Embryol. exp. Morph. Vol. 9 , part 1 , p. 177-127 . 1961.

2. Later, similar experiments were done by R. Oliver. From all vibrissae HF bulbs transplanted in micro-incision of ear pinna, 25% of them produce hair shafts above skin level, 30% - below it.

R. F. OLIVER . Whisker growth after removal of the dermal papilla & lengths of follicle in the rat hooded rat . // J. Embryol. exp. Morph. Vol. . 15< 3< p. 331-347 , 1966.

3. HFs bulbs were transplanted in different places:
Rat stomach wall. HFs bulbs were found to degenerate 14 weeks after operation.
Under spleen capsule. 9 week after at histology HFs bulbs were found to preserve high level of integrity. But, they don’t produce hair shaft. 13 weeks after operation, 3 from 4 transplanted bulbs start to produce shafts. They average length was just 1 mm.

J. COHEN. The transplantation of individual rat & guinea-pig whisker papillae . // J. Embryol. exp. Morph. Vol. 9 , part 1 , p. 177-127 . 1961.

4. In more recent experiments vibrissae HFs segments of different length were transplanted under kidney capsule:
- Distal half [i.e. lower part] of vibrissae HFs. It produce convoluted shaft. Differentiation of IRS [inner root sheath] also took place.
- Distal ( of vibrisae HFs. Long, convoluted shaft was produced.
The most distal part of vibrissae HFs. These implants have weak ORS and some of them produce coarse shaft-like keratinizated structure.

YI KOBAYASHI , PH . D ., & NISHIMURA , B . S . Ectopic growth of mouse whiskers from implanted lengths of plucked vibrissa follicles . // // J. Invest. Dermatol . 1989 . vol . 92 . p. 278 – 282 .

New HFs regenerate in vitro from following cell populations: M, ORS, DP & DS cells. Initially, ORS cells were seeded into vibrissae derived collagen capsule on basal membrane. Few days after mixture of cultured M, DP & DS cells was added inside collagen capsule. Thereafter, received structures were cultured for 2-3 weeks in vertical position in 3-D collagen gel. At histology several highly twisted shaft-like structures were founded.

JAHODA CA., REYNOLDS AJ ., Dermal- epidermal interaction . Follicle derived cell populations in the study of hair growth mechanism . // J. Invest. Dermatol. 1993 vol. 101 p. 33s-38s .