Hair transplantation in mice: Challenges and solutions.

Hair follicle cells contribute to wound healing, skin circulation, and skin diseases including skin cancer, and hair transplantation is a useful technique to study the participation of hair follicle cells in skin homeostasis and wound healing. Although hair follicle transplantation is a well-established human hair-restoration procedure, follicular transplantation techniques in animals have a number of shortcomings and have not been well described or optimized. To facilitate the study of follicular stem and progenitor cells and their interaction with surrounding skin, we have established a new murine transplantation model, similar to follicular unit transplantation in humans. Vibrissae from GFP transgenic mice were harvested, flip-side microdissected, and implanted individually into needle hole incisions in the back skin of immune-deficient nude mice. Grafts were evaluated histologically and the growth of transplanted vibrissae was observed. Transplanted follicles cycled spontaneously and newly formed hair shafts emerged from the skin after 2 weeks. Ninety percent of grafted vibrissae produced a hair shaft at 6 weeks. After pluck-induced follicle cycling, growth rates were equivalent to ungrafted vibrissae. Transplanted vibrissae with GFP-positive cells were easily identified in histological sections. We established a follicular vibrissa transplantation method that recapitulates human follicular unit transplantation. This method has several advantages over current protocols for animal hair transplantation. The method requires no suturing and minimizes the damage to donor follicles and recipient skin. Vibrissae are easier to microdissect and transplant than pelage follicles and, once transplanted, are readily distinguished from host pelage hair. This facilitates measurement of hair growth. Flip-side hair follicle microdissection precisely separates donor follicular tissue from interfollicular tissue and donor cells remain confined to hair follicles. This makes it possible to differentiate migration of hair follicle cells from interfollicular epidermis in lineage tracing wound experiments using genetically labeled donor follicles.

Chemiluminescence from UVA-exposed skin: separating photo-induced chemiluminescence from photophysical light emission.

Several previous studies have reported luminescence emission from skin following exposure to UVA radiation in air. We show that UVA irradiation of biomaterials and polymers in oxygen, including bovine stratum corneum, followed by photon counting results in a complex emission due to a combination of photophysical processes together with photo-induced chemiluminescence (PICL). The photophysical processes include fluorescence, phosphorescence and charge-recombination luminescence. By irradiating materials in an inert atmosphere such as nitrogen and allowing photophysical light emission to fully decay before admitting oxygen, the weak photo-induced chemiluminescence generated via free radical reactions with oxygen can be separated and analysed. PICL emission from bovine stratum corneum is weaker than for wool keratin and bovine skin collagen, probably due to its higher water content, and the presence of the natural antioxidants ascorbate and tocopherol.

Deficiency of Bid protein reduces sepsis-induced apoptosis and inflammation, while improving septic survival.

Increased apoptotic cell death is believed to play a pathological role in patients with sepsis and experimental animals. Apoptosis can be induced by either a cell death receptor (extrinsic) or a mitochondrial (intrinsic) pathway. Bid, a proapoptotic member of the Bcl-2 family, is thought to mediate the cross talk between the extrinsic and intrinsic pathways of apoptosis; however, little is known about the action of Bid in the development of apoptosis and organ-specific tissue damage/cell death as seen in polymicrobial sepsis. Our results show that after the onset of sepsis, tBid (the active form of Bid) is significantly increased in mitochondrial fractions of the thymus, spleen, Peyer patches, and liver, and that Fas or FasL deficiency blocks Bid activation in various tissues after septic challenge. Increased Bid activation is correlated with increased active caspase-3, caspase-9, and apoptosis during sepsis. Bid-deficient mice exhibit significantly reduced apoptosis in the thymus, spleen, and Peyer patches compared with background mice after sepsis. Furthermore, Bid-deficient mice had significantly reduced systemic and local inflammatory cytokine levels and improved survival after sepsis. These data support not only the contribution of Bid to sepsis-induced apoptosis and the onset of septic morbidity/mortality, but also the existence of a bridge between extrinsic apoptotic signals, e.g., FasL:Fas, TNF:TNFR, and so on, and the intrinsic mitochondrial pathway via Bid-tBid activation during sepsis.

Cryo-electron microscopy of trichocyte (hard alpha-keratin) intermediate filaments reveals a low-density core.

Trichocyte intermediate filaments (IF) are the principal components of epidermal appendages such as hair and nail. Based on studies by a variety of techniques, it has been inferred that trichocyte IF are structurally similar to other kinds of IF. However, some basic structural attributes have yet to be established: in particular, it has remained unclear whether IF are hollow. We have examined trichocyte IF isolated from rat vibrissae and human hair follicles by electron microscopy. Scanning transmission electron microscopy of freeze-dried specimens yielded mass-per-unit-length values of approximately 32 kDa/nm, with the human preparations also containing filaments at half this density, corresponding to two rather than four protofibrils. Radial density profiles calculated from cryo-electron micrographs of vitrified specimens preserved in a near-native state revealed a low-density region of approximately 3 nm diameter around the filament axis. A minor species of filament with the same internal structure was surface-decorated with material arranged with a helical pitch length of 9.3 nm. These filaments appear to represent IF coated with associated proteins-perhaps, "high-sulfur" proteins-readied for incorporation into the filament-matrix biocomposite of the mature hair.