2k). 6 sulphate). A region of strong labelling for aggrecan, dermatan sulphate and chondroitin 6 sulphate immediately surrounded the Meibomian glands. The site of labelling corresponded to a layer of acellular and amorphous matrix seen histologically that we have termed the territorial matrix. The results suggested that this tarsal plate is a specialized connective tissue that is neither purely fibrous nor cartilaginous, yet has an aggrecan content that probably contributes to its stiffness. Its unique character highlights the challenge in choosing an ideal mechanical substitute. As patients with rheumatoid arthritis often have problems relating to tear film deficiency, the ability of aggrecan or COMP to act as autoantigens may be significant. An immune reaction directed against these molecules could alter tarsal gland function by interfering with the interaction between the glands and their territorial matrix. strong class=”kwd-title” Keywords: aggrecan, autoimmune response, extracellular matrix, glycosaminoglycans, proteoglycans, Meibomian glands Introduction The superior tarsus is usually a plate of tissue that stiffens the upper eyelid, gives it support and determines its form (Williams et al. 1995). Its curved shape enables it to maintain close contact with the globe during fast blinking movements. Embedded within the plate are the Meibomian (tarsal) glands. These produce an oily secretion that spreads as a surfactant over Rabbit Polyclonal to TNF Receptor I the globe and contributes to an aqueous barrier that remains functional after blinking (McCulley & Sparkle, 2004). The secretion reduces evaporation by adding a hydrophobic layer to the surface of the tear film (Williams et al. 1995; Lozato et al. 2001). It thus follows that any alteration in tarsal gland secretion will change the composition of the film and this could lead to a variety of symptoms including dry vision, keratonconjunctivitis sicca and even Aliskiren D6 Hydrochloride corneal ulcerations (Shimazaki et al. 1998; Jain et al. 2001). In exocrine glands elsewhere in the body, the connective tissue stroma around the glandular epithelium can modulate the activity of the secretory cells and changes in stromal composition can even be associated with disease (Bissell, 1998; Hagios et al. 1998; Goicovich et al. 2003). It is thus of interest to establish the character of the extracellular matrix (ECM) of the tarsal plate and in particular the ECM that immediately surrounds the Meibomian glands. We have subsequently referred to this ECM as the territorial matrix. The composition of the ECM also Aliskiren D6 Hydrochloride determines the Aliskiren D6 Hydrochloride physical properties of the tarsal plate. These properties are an important surgical concern in reconstructing the upper eyelids of patients with tarsal deficiencies (Jordan et al. 1990; Jordan & Anderson, 1997; Yaqub & Leatherbarrow, 1997; Mullner & Langmann, 1999; Kamiya & Kitajima, 2003). The substitute tissue needs to have a similar consistency to the tarsal plate itself and be grafted together with a mucosa that can functionally replace the conjunctiva and its underlying lamina propria. A mechanically stable, superior tarsus is also essential for the insertion of levator palpebrae superioris (Landolt, 1985). Among the graft tissues that have been most frequently used are various forms of cartilage Aliskiren D6 Hydrochloride C notably from the ear and nasal septum (Jordan et al. 1990; Kamiya & Kitajima, 2003). Mucoperiosteum from the hard palate and aortic wall tissue have also been used (Jordan & Anderson, 1997) and a material called chondroplast that is prepared from irradiated bovine cartilage (Mullner & Langmann, 1999). According to Ito et al. (2001), ear cartilage is too stiff, but fascia lata is not stiff enough. Yet the latter is usually a dense fibrous connective tissue C and this is also how the tarsal plate is commonly classified in modern anatomy texts (Williams et al. 1995). It is of interest, however, that there are several statements in the older histological literature that this plate is usually cartilage-like, fibrocartilaginous or that this eyelid contains lid cartilage (B?hm & von Davidoff, 1895; Szymonowicz, 1924; Wallraff, 1960). Such descriptions seem to be largely based on the mechanical properties of the tissue. The purpose of the present study is to promote a better understanding of the physical characteristics of the superior tarsal plate and its local association with the Meibomian glands. We have done this by analysing the immunohistochemical composition of the plate ECM. In order.