Unilateral Basement Membrane Zone Alteration of the Regenerated Laminar Region in Equine Chronic Laminitis

Abstract

ABSTRACT. Between the laminar epidermis and the laminar dermis of laminar region (LR) in equine foot, it can be observed the basement membrane zone (BMZ), which is composed of a basement membrane and its accompaniments like the hemidesmosome and anchoring fibril. Alteration in the BMZ in equine laminitis is possibly related with not only development but also recovery outcome and recurrence of this disease. However, there is little known about the structure of the BMZ during the recovery phase of this disease. To assess the condition of the BMZ of LR affected by chronic laminitis, the tissue was examined in three cases at two weeks, four weeks and three months after the onset of laminitis, using pathological, immunohistochemical and electron microscopic techniques. Histologically in all laminitis cases, there was a regenerated laminar epidermis with proliferating keratinocytes between the Stratum medium and the dermis, but it included the undeveloped secondary epidermal laminae (ud-SELs) structure in one side of the primary epidermal laminae, especially in the part of the deep area of LR. Immunohistochemical results were positive for the anti-type IV collagen, anti-type VII collagen and anti-laminin 5 antibodies in the most BMZs. However, partial BMZs adjacent to the ud-SELs were negative for the anti-type VII collagen and anti-laminin 5 antibodies. Ultrastructurally, in the BMZ of the ud-SEL, the lamina densa and the lamina lucida were present. In contrast, the anchoring fibrils and the hemidesmosomes were either absent, or present at lower than normal levels. In conclusion, the present study indicated that the part of regenerated LR in chronic laminitis was not able to fully restore to construct the BMZ for a long time, especially in the unilateral side of laminar epidermis. It might be related with recurrence of this disease. KEY WORDS: basement membrane zone, chronic laminitis, collagen, equine, laminin 5.J. Vet. Med. Sci. 67 (7): [685][686][687][688][689][690][691] 2005 The integumental tissues of the foot are important in supporting the horse's entire body weight during static and dynamic loading conditions. If severe intractable hoof disease occurs, the horse may lose not only the ability to run, but also to stand. Laminitis is one such intractable hoof condition and has a recurrent nature. Many horses have suffered from this disease over extended periods, resulting in significant treatment costs, and therefore the equine industry has a great deal of interest in clarifying the pathogenesis and developing treatment methods [5,9,12].Anatomically, the laminar region in foot displays a complex 3-dimensional structure consisting of the primary epidermal lamina (PEL) and the secondary epidermal lamina (SEL) which interdigitate with their dermal counterparts [24]. These dermal and epidermal components are separated by the basement membrane zone (BMZ), which is composed of a basement membrane and its accompaniments like the hemidesmosome and anchoring fibril [23]. The hemidesmosome, anchoring fibril and other c...

Type VII and XVII Collagen mRNA Expressions in Regenerated Epidermal Laminae in Chronic Equine Laminitis

“…It suggested that capability to form the hemidesmosomes in rLE might be lower than normal. This hypothesis is consistent with the previous report [10] in which existence of few hemidesmosomes were recognized in the BMZ. At current, we cannot propose any regulatory mechanism that can promote the type VII collagen and suppress the type XVII collagen, simultaneously in horse’s foot.…”

“…The pathologic evidence at first stage is disconnection between the laminar epidermis (LE) and the laminar dermis (LD) resulted from basement membrane zone (BMZ) degradation [16,17,18]. While the detached epidermis structure loses vascular support and rapidly necrotizes, some keratinocytes attaching to the BMZ subsequently regenerate the LE [10, 16] and produce finally the ectopic white line tissue [9]. In this healing process, the regenerated laminar epidermis (rLE) could re-organize the BMZ in which the type VII and XVII collagens are included [10].…”

“…While the detached epidermis structure loses vascular support and rapidly necrotizes, some keratinocytes attaching to the BMZ subsequently regenerate the LE [10, 16] and produce finally the ectopic white line tissue [9]. In this healing process, the regenerated laminar epidermis (rLE) could re-organize the BMZ in which the type VII and XVII collagens are included [10]. In this pilot study, we tried to confirm whether the rLE could express above these two types of extracellular matrix in two laminitis cases (case 1: two year old filly, two weeks after onset; case 2: three year old female, four weeks after onset) contrasting with one control horse (four year old female).…”

“…For sampling, the laminar interface in proximo-distal 50% hoof wall height of the each right fore-hoof was trimmed by the previously described method [10, 19]. One section was rapidly frozen in liquid nitrogen for northern blot analysis.…”

Glucocorticoid therapy and the risk of equine laminitis

“…2004; Mobasheri et al . 2004) and delayed regeneration of anchoring filaments between keratinocytes and basement membrane (Kuwano et al . 2005) are features of acute and chronic laminitis, respectively, and because regenerations of hemidesmosomes and anchoring filaments must occur during healing, it is possible that glucocorticoids could further contribute to the severity of laminitis or delay remodelling of the hoof during recovery.…”