In this study we investigated the capacity of the human hair follicle to regenerate a fiber-forming bulb after its amputation. We removed the bases from terminal follicles from a variety of sites and transplanted the follicles onto athymic mice, either still attached to a skin graft or as subcutaneous implants of individual follicles. External hair growth was observed on the skin grafts, and histology of the follicles revealed restoration of dermal papillae and follicle bulb structures. This result suggests that the capacity of hair follicles to regenerate their lower structures after removal, which was first demonstrated on whisker follicles, may be a general phenomenon. It emphasizes the importance of specific cellular subpopulations within the follicle and the role of dermal-epidermal interactions in adult follicle activities.
A series of experimental bioassays has shown that the dermal papilla of the adult rodent vibrissa hair follicle retains unique inductive properties. In view of the many phenotypic and functional differences between specific hair follicle types, and the growing interest in hair follicle biology and disease, it remains important to establish that the human hair follicle dermal papilla has equivalent capabilities. In this study we tested the ability of human hair follicle papillae to induce hair growth when implanted into transected, athymic mouse vibrissa follicles. The implanted papillae that interacted with mouse follicle epithelium created new fibre-producing follicle end bulbs. The origin of the papillae in the recombinant structures was confirmed using laser capture microdissection and human specific gender determination by PCR. The demonstration that intact adult human dermal papillae can induce hair growth has implications for molecular analysis of basic hair growth mechanisms, particularly since the study involved common epithelial-mesenchymal signalling and recognition properties across species. It also improves the prospects for a cell-based clinical approach to hair follicle disorders.
SUMMARYI . The ability of a wound to resist rupture (energy absorption or 'toughness') is calculated from its tensile strength and extension ('give '). This property of the wound is only half that of normal tissue after 5 months of healing.2. A biomechanical study shows that tape-closed wounds develop greater tensile strength than sutured wounds. However, they are more brittle and have, as a result, no greater ability to resist rupture. Other considerations such as obliteration of dead space, prevention of infection, and cosmetic result may therefore be used in choosing between them.3. The rate of collagen synthesis is the same in both wound types. It reaches its peak between 20 and 40 days and returns to normal by 150 days.4. The scanning electron microscope demonstrates how the structure of the wound evolves from random fibril patterns to large collagen masses. Mechanical behaviour can be related to collagen fibre weave and variations in fibre alinement. Differences in organization are observed between tape-closed and sutured wounds and a hypertrophic scar (keloid). 5.The scanning electron microscope appearance of a hypertrophic scar supports the view that its existence may depend on repeated rupturing and rehealing of small fibrils in a brittle scar. 6. It may be possible to control the structural organization of collagen during healing, thus improving ' scar performance ' and making possible the 'cultivation' of collagen shapes and materials for repair purposes.THIS study was prompted by the observation that the apparently well-healed skin wound was remarkably weak at the end of IOO days (Douglas, Forrester, and Ogilvie, 1969).Since local factors play an important part in determining the quality of repair (Halsted, 1913;Whipple, 1940;Sandblom, 1944;Dunphy and Jackson, 1962) we decided to further our investigations by a comparison of tape-closed and suture-closed wounds healing synchronously in the same animal.We adopted this approach because there are indications that tape-closure produces better healing conditions. Suture-closure causes a local inflammatory response (Howes, 1933; Postlethwaite, Schauble, Dillon, and Morgan, 1959) and immobilizes the wound, whereas careful tape-closure reduces inflammation and improves the cosmetic result (Dunphy and Jackson, 1962; Ordman and Gillman, 1966; Conolly, Hunt, Zederfeldt, Cafferata, and Dunphy, 1969). In addition, the exposure to adjacent soft-tissue forces appears to improve the strength of repair (Brunius and Ahrkn, 1969).A further consideration is that strength measurements, although undoubtedly providing valuable information on the healing process, incompletely describe repair. The extension or 'give' is just as important and the mechanical behaviour before rupture is of considerable theoretical and practical significance.Over 500 wounds were examined between 10 and 150 days using a bio-engineering technique previously reported (Forrester, Zederfeldt, and Hunt, 1969). Standard, die-cut specimens of skin and scar were tested to their breaking points. The specim...
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