M. Robinson et al., In vivo induction of hair growth by dermal cells isolated from hair follicles after extended organ culture, J INVES DER, 117(3), 2001, pp. 596-604
Successful hair follicle organ culture has been established for some time,
but hair growth in vitro is limited and generally terminates prematurely in
comparison with in vivo. The reasons why growth stops in culture are as ye
t unknown. In this investigation, adult rat vibrissa follicles for which gr
owth in culture is limited to about 10 d, were maintained in vitro for a mi
nimum of 20 d after the hair shaft stopped growing. The pattern of fiber gr
owth and long-term follicle pathology reflected the initial hair cycle stag
e at the time of isolation. Furthermore, there was evidence that a group of
follicles put into culture when in late anagen were attempting to cycle in
vitro. Microscopy showed that, in spite of widespread pathologic changes t
o the follicle epithelium, dermal cells in the follicle showed remarkable r
esilience. Their viability was confirmed when primary cell cultures were es
tablished from isolated dermal tissue. These cells labeled positively for a
lpha -smooth muscle actin, an established marker of hair follicle dermal ce
ll phenotype in vitro. Moreover, isolated dermal tissue induced hair growth
when implanted into inactivated hair follicles in vivo. These data confirm
that the cessation in hair growth is not due to a loss of the inductive ca
pacity in the dermal component. Long-term organ culture may provide opportu
nities to investigate factors that are expressed or lost during hair growth
cessation. In addition it may be possible to develop this method further t
o obtain a reliable and predictable model of hair follicle cycling in vitro
.