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Biomedical subjects

R F Oliver

Publications and source records attributed to R F Oliver.

53 records · Page 3Linked to original sources
PubMed1977

Incorporation of stored cell-free dermal collagen allografts into skin wounds: a short term study.

Allogeneic dermal collagen has been evaluated as an alternative to skin autografts for the permanent replacement of lost or damaged skin in the rat. All non-collagenous structures were removed from full-thickness back skin by treatment with a solution of crystalline trypsin. Such dermal collagen preparations were grafted into skin wounds, examined up to 8 1/2 weeks after operation, and compared with excised wounds and skin isografts and allografts of the same initial size. The dermal collagen grafts, particularly when dressed with a sheet of dermal collagen, become recellularised, revascularised and re-epidermalised. Unlike the skin allografts, there was no evidence of cellular rejection. Whereas contracture of the excised wounds was delayed, but not suppressed, by applying a conventional dressing, collagen grafts maintained from 60 to 100 per cent of their original size. In contrast, equivalent skin isografts shrank to 50-60 per cent and showed persistent epidermal hyperplasia.

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PubMed1976

Morphological changes associated with the growth cycle of vibrissal follicles in the rat.

Morphological changes which occur in the growth cycle of the rat vibrissal follicle during the transitional period between consecutive anagen phases are described. In contrast with pelage hair follicles, there is no shortening of the follicle, no formation of a papilla 'rest' and no close synchrony between club differentiation and follicle regression. Telogen is therefore considered to occur after loss of the matrix of the hair bulb and maximal diminution of the dermal papilla to a small aggregation of cells. These difference are discussed in relation to current nomenclature of the hair cycle and the function of the vibrissal follicle.

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PubMedDate not supplied

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)

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PubMedDate not supplied

Induction of hair growth by implantation of cultured dermal papilla cells.

Mammalian hairs are formed by differentiation and keratinization of cells produced in the epidermal matrix (Figs 3, 4). Using the rodent vibrissa follicle as a model, transplantation studies have shown that the dermal papilla, a discrete population of specialized fibroblasts, is of prime importance in the growth of hair. Papillae induce hair growth when implanted into follicles and can interact with skin epidermis to form new hair follicles. When grown in culture, papilla cells display singular morphological and behavioural characteristics compared with connective tissue cells from other skin sources. We report here that serially cultured adult papilla cells can induce the growth of hair when implanted into follicles which otherwise would not grow hairs. This finding presents an opportunity to characterize properties distinguishing the papilla cell population from other skin fibroblasts, and, more specifically, those which control hair growth. The eventual application of this work to human hair replacement techniques can also be envisaged.

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PubMedDate not supplied

Histological studies of subcutaneous and intraperitoneal implants of trypsin-prepared dermal collagen allografts in the rat.

The possibility of using allograft collagen for the permanent replacement of lost or damaged connective tissues has been examined in the rat. The cellular components of skin, which are known to be of major importance in allograft rejection, were removed by treating skin with a solution of crystalline trypsin at 15 degrees C. Non-collagenous structures were largely removed by 7 days, but the purification process continued up to 28 days without damage to the collagen fibrils. Dermal collagen allografts, which were implanted intraperitoneally or subcutaneously and biopsied 3-83 days after operation, became recellularized and revascularized without being being resorbed. In contrast to skin allografts, there was no evidence of cellular rejection of the collagen grafts, even when recipient animals had been sensitized to allogeneic skin from the same donor. Densensitization of collagen to collagenase, by treating dermal collagen with solutions of glutaraldehyde at concentrations ranging from 0.001-1.0 per cent, was also investigated in vitro and by implantation. The best results, in terms of preservation of the collagen bundle architecture and graft recellularization without persisting inflammation, were achieved with collaged pre-treated with a solution of 0.01% glutaraldehyde.

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