| Summary: | The study investigated healthy claw samples from cross-bred heifers aged around 20 months. Histological studies adopted a novel sectioning approach along planes parallel to the wall, identifying dynamics of the keratinisation process, localisation of elastic fibres and anatomical features of cap papillae and horn. Structural molecules were investigated immunohistochemically, including cytokeratins, cytokeratin 14 (CK14) and β-actin. The results showed patterns of suprabasal keratin deposition and loss of signal for CK14 and β-actin markers in differentiating keratinocytes. Localisation of vimentin provided evidence of mesenchymal cells in laminar dermis. Transforming growth factor β1 (TGFβ1) and connective tissue growth factor (CTGF) were investigated immunohistochemically, by <i>in situ</i> hybridisation and RT-PCR. Immunohistochemistry showed signals in the dermis and epidermis, with mRNA presence solely in the dermis and high synthesis rates on comparison with internal control. Mean expression levels were higher in summer than in winter. Collagen I (COL1A2), elastin, estradiol receptor β, cyclin A and B were also investigated by RT-PCR and consistently amplified. Tissue cultures were carried out in order to study TGFβ1, CTGF and COL1A2 expression by RT-PCR in tissue explants incubated in presence of TGFβ1. Results identified a time effect but absence of a concentration effect. Proteomic analysis of fractions extracted from incubated and non-incubated (control) explants showed significant differences for a number of spots, mainly in the keratin region of the electrophoretic gels. In conclusion, the study has provided novel information on molecules of importance in the structure and regulation of epidermal and dermal cells and dermal extracellular matrix in the laminar region of the bovine claw.
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