Synthesis and distribution of cytokeratins in healthy and ulcerated bovine claw epidermis

Abstract

Keratinization of the epidermal cells of the bovine claw generates the horn that gives the tissue its mechanical strength. Disruption of keratinization is likely to have a detrimental effect on the strength and integrity of the horn, and could lead to solar lesions and lameness. As part of a wider investigation of the cell biological causes of lameness in dairy animals, we have compared keratin synthesis and distribution in healthy bovine claw tissue with those in hooves with solar ulcers. Protein synthesis was measured by [35S]-labelled amino acid incorporation in claw tissue explant cultures. [35S]-labelled protein synthesis was higher in tissue from diseased claws than in healthy claws, and highest at the ulcer site. The identity of proteins synthesised in vitro did not differ between healthy and diseased tissue. DNA synthesis indicative of cell proliferation was also elevated in diseased tissue. Immunoblotting after one- or two-dimensional electrophoresis showed cytokeratins (CK) 4, 5/6, 10 and 14 to be amongst those expressed in healthy claw tissue. The relative abundance of these keratins was not altered in healthy regions of ulcerated hooves, nor at the ulcer site, but CK16, not usually found in healthy tissue, was detected in the sole of diseased claws. CK5/6 and CK14 were shown by immunohistochemistry to be present in the basal epidermis of healthy tissue, whereas CK10 was found in supra-basal layers. In healthy tissue from ulcerated claws, this distribution was unaltered, but at the site of solar ulcers, CK5/6 and CK14 were each found in both basal and supra-basal epidermis. The study suggests that solar ulceration of the bovine claw is not associated with gross alteration in the keratin composition of the tissue, but causes abnormal distribution of cytokeratins, perhaps as a result of loss of positional cues from the basement membrane. Ulceration did, however, stimulate cell repair involving epidermal protein synthesis (including keratins), and keratinocyte proliferation.

Structure and functions of keratin proteins in simple, stratified, keratinized and cornified epithelia

“…Proper keratinization and cornification processes are crucial for the health of cornified organs (Bragulla & Mülling, 1997). For example, in the dyskeratotic sole epidermis of the bovine hoof, the suprabasal keratinocytes continue to produce keratins that are characteristic of the basal cells and also produce K16 instead of the usual K1 and K10 (Hendry et al. 2001).…”

Serum protein pattern during cow pregnancy: Acute‐phase proteins increase in the peripartum period

“…Although some work has been devoted to model organisms (Xenopus laevis as an animal model of development [3]) or to pets (cats [4] and dogs (Miller et al, personal communication)), publications in the field have mostly concentrated on farm animals (horses [5], chickens [6,7], pigs (Miller et al, personal communication)). Due to the economic relevance of animal production, special attention is being given to cattle, with investigations on proteins from both bovine tissues/cells [8][9][10][11][12][13][14][15][16][17][18] and biological fluids [12,[19][20][21][22][23]. Several reports address proteomics of bovine reproductive system [24][25][26][27][28][29].…”

Horse hooves and bird feathers: Two model systems for studying the structure and development of highly adapted integumentary accessory organs—the role of the dermo‐epidermal interface for the micro‐architecture of complex epidermal structures

“…Many hoof diseases are characterised by a pathological subdivision of the papillary body (Marks, '84;Hirschberg, 2000), probably initiated by the same driving forces as in the fetal development, i.e., lack of oxygen and nutrients in the misaligned or overloaded hoof regions. Differing keratin expression in the germinative and keratinised epidermal layers of the modified skin of healthy and diseased digital end organs has been described (Wattle, 2000;Hendry et al, 2001), likewise suggesting that keratinocyte activation is involved in physiological as well as pathological adaptation of the digital end organ, particularly in the development and maturation of the dermo-epidermal interface. Keratinocyte activation is also engaged in dermal angiogenesis (Detmar, 2000), and sprouting and intussusceptional, i.e., nonsprouting, remodelling angiogenesis have been reported both in the maturing and pathologically altered bovine pododerma (Hirschberg et al, 2003), indicating a tight regulatory vaso-hormonal association between the dermal microvasculature and the formation of the dermo-epidermal interface.…”