Roy F. Oliver

Dermal collagen implants

The feasibility of using preparations of cell-free, fibrous dermal collagen, prepared by trypsin-treatment of skin, for the repair of soft body tissues has been examined both as subcutaneous implants and as a replacement for dermis in skin wounds in rats. Increased collagen stability, and suppression or reduction of tissue antigenicity in collagen heterografts, was achieved by crosslinking with weak solutions of aldehydes while still allowing implant recellularization and revascularization. Tritium-labelled collagen turnover studies have shown that maintenance of collagen mass in implants crosslinked with glutaraldehyde occurs primarily by inhibition of loss of original implant collagen. Some of the in vitro growth characteristics of human fibroblasts on animal collagen preparations are also described.

In vivo depletion of CD8+ T cells restores hair growth in the DEBR model for alopecia areata

Summary Alopecia areata (AA) is a putative autoimmune disease in which anagen hair follicles are the target of immune cell attack. While both CD4+ and CD8+ T lymphocytes are prominent in the infiltrate, their respective roles in the pathogenesis of AA remain unknown. Here we directly investigated the activity of CD8+ cells in the inhibition of hair growth using the Dundee experimental bald rat (DEBR) model for AA. Eight lesional DEBRs were fully depleted of their CD8+ cells by intraperitoneal injection of OX‐8 monoclonal antibody (MoAb) specific for these cells over a 15‐day therapy course. A control group of eight lesional rats was injected with the irrelevant MoAb OX‐21. Sequential blood samples were analysed by flow cytometry to observe changes in the CD8+ cell population and macropliotography used to record changes in hair growth activity.

Topical FK506 : A potent immunotherapy for alopecia areata? Studies using the dundee experimental bald rat model

We elected to examine the efficacy of the topically applied immunosuppressive agent FK506 (Prograf®) in the treatment of alopecia areata (AA) using the Dundee experimental bald rat (DEBR) model. Thirty lesional DEBR rats were allocated to five groups of six. Group I rats received 0.1 mL of a 0.25% solution of FK506 within a 2x2 cm marked area on one bald flank twice a week (125μg FK506/cm2 per week) for 8 weeks, while the contralateral flank was left untreated. In group II, 0.05mL of a 0.1% solution of FK506 was applied 5 days per week on one flank (62.5 μg FK506/cm2 per week) and control vehicle to the opposite flank for 8 weeks. Group III rats were treated as in group II except that drug and vehicle were applied twice a week (25 μg FK506/cm2 per week) for 4 weeks. A positive control group received orally administered cyclosporin A (CsA) (10mg/kg daily) for 8 weeks and a further group was left untreated. Rats were regularly examined and photographed with skin biopsies taken from groups II and III. All FK506‐treated rats regrew hair at the site of drug application within 14–21 days. Growth continued for 3 weeks beyond termination of treatment after which gradual hair loss was observed. No hair growth was seen as a result of vehicle application and hair loss continued on untreated areas and in the untreated control group. Immunohistology revealed a drastic reduction in the follicular inflammatory infiltrate at the site of the FK506 application. The oral CsA group responded by simultaneous regrowth of hair over the whole body. Our findings suggest that FK506 may have considerable potential as a topical treatment for AA.

The DEBR rat: an animal model of human alopecia areata

Summary The Dundee experimental bald rat (DEBR) is reported as a model for human alopecia areata. Parallels with human alopecia areata were observed in relation to the gradual and patchy loss of hair and the penetration of both pelage and vibrissa follicles by mononuclear cells. In particular, the apparent disruption of the follicles within the precortical region of the epidermal component and consequent alterations of normal geometrical relationships between dermal and epidermal components relate directly to similar studies on human alopecia areata. In comparison with other previously described hypotrichotic rodent mutants, the DEBR rat exhibits a unique mechanism of hair loss which may provide important information regarding the pathomechanism of human alopecia areata.

Comparison of Alopecia areata in Human and Nonhuman Mammalian Species

Alopecia areata (AA) is a nonscarring form of inflammatory hair loss in humans. AA-like hair loss has also been observed in other species. In recent years the Dundee experimental bald rat and the C3H/HeJ mouse have been put forward as models for human AA. AA in all species presents with a wide range of clinical features from focal, locally extensive, diffuse hair loss, to near universal alopecia. Histologically, all species have dystrophic anagen stage hair follicles associated with a peri- and intrafollicular inflammatory cell infiltrate. Autoantibodies directed against anagen stage hair follicle structures are a consistent finding. Observations on AA pathogenesis suggest nonhuman species can provide excellent models for the human disease. Ultimately, animal models will be used to determine the genetic basis of AA, potential endogenous and/or environmental trigger(s), mechanism(s) of disease initiation and progression, and allow rapid evaluation of new and improved disease treatments.

Trans-species hair growth induction by human hair follicle dermal papillae.

Abstract: 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.

Dermal-epidermal interactions.

The dermal papilla is established as a permanent and stable population of specialized fibroblasts that first appear as a cellular aggregate that interacts with the epidermis to ensure follicle development. Our experimental findings strongly suggest that thereafter the papilla, in association with the confluent lower dermal sheath, continues to interact with the follicular epidermis with the papilla cells, which retain their aggregative property, undergoing cyclic changes in size and synthetic activities in phase with the hair cycle. In these activities, the lower follicle dermis appears to act as a functional unit that retains key embryonic characteristics throughout the lifetime of the follicle, re-enacting its inductive influence over follicular epidermis to regulate the profound morphogenetic changes that occur during successive hair cycles and to determine the physical characteristics of the fibers produced. While epidermal mitotic inhibitors have been suggested as a controlling mechanism in the hair cycle, we have argued that the papilla provides potent factors that stimulate epidermal proliferation in the hair germ to initiate, and then sustain, anagen and also follicle morphogenesis. Our recent findings with cocultures of dermal papilla and epidermal cells, which demonstrated that papilla cells enhance epidermal cell attachment and proliferative activity, reinforces this supposition. Thus, it may prove that the intrinsically determined aspect of the hair cycle reflects and is dependent on an intrapapillary cycle of events. Furthermore, we have suggested that at another level of interaction the dermal component of the follicle may mediate the influence of systemic factors, which are known to modify this innately programmed pattern of follicle behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistological study of the development of the cellular infiltrate in the pelage follicles of the DEBR model for alopecia areata

The Dundee experimental bald rat (DEBR) undergoes hair loss associated with perifollicular infiltrates of mononuclear cells (MNC), a pathological characteristic of human alopecia areata (AA). To investigate further the pathogenesis of the disease in this animal model, we have studied the development, composition and extent of the perifollicular MNC infiltration in young (6‐week‐old), prelesional (3‐month‐old), active lesional, and established lesional DEBR rats, using 6‐week‐ and 6‐month‐old Wistar rats as normal controls. The proportions of hair follicles showing infiltration by MNC and their main subsets were determined using immunohistochemical staining of serial cryostat sections of flank skin biopsies.

The Dermal Papilla and Maintenance of Hair Growth

The dermal papula is present as an aggregation of mesodermal cells at the earliest stages of follicle development and persists as an anatomical entity throughout the life-time of the hair follicle. It contrasts with the hair-producing epidermal matrix which is a transitory structure appearing only during the anagen phase of the hair growth cycle. Using the adult rat vibrissa follicle as a model system, cell culture, microsurgical and transplantation techniques have provided direct evidence of a crucial role for follicular dermis and, in particular, the dermal papilla in follicle development, the maintenance of follicles and the control of hair growth through subsequent hair cycles. Hair growth does not occur in the absence of the papilla. In situ wounding of papillae can lead to hairs growing up to 30% longer than normal. Following excision of the entire bulb, in both vibrissa and human follicles, new papillae regenerate from cells from the follicular sheath and hair growth is resumed. Implants of isolated papillae, or cultured papilla cells, into follicles induce hair growth and the formation of new, vibrissa-producing follicles when recombined with skin epidermis. In these interactions papilla cells induce the development of an epidermal matrix, heightened epidermal mitotic activity and the differentiation of hair follicle-type keratin products. Cultured vibrissa papilla cells also stimulate keratinocyte proliferation in vitro. These findings suggest that the behaviour of the epidermal component of the follicle is under the control of the follicular dermis which appears to retain embryonic characteristics.

The DEBR rat, alopecia areata and autoantibodies to the hair follicle

Summary Many attempts have been made to implicate hair follicle‐specific autoantibodies in the pathogenesis of alopecia areata (AA), a suspected autoimmune disease. Using the DEBR rat model for AA, we developed a refined indirect immunofluorescent technique to examine the sera from individual rats for the presence of autoantibodies to the hair follicle and to other tissues. Sera were tested on cryostat sections from normal PVG/Ola rats and DEBR rats.