Wnt/β‐catenin signaling of cartilage canal and osteochondral junction chondrocytes and full thickness cartilage in early equine osteochondrosis

Abstract

The objective of this study was to elucidate gene and protein expression of Wnt signaling molecules in chondrocytes of foals having early osteochondrosis (OC) versus normal controls. The hypothesis was that increased expression of components of Wnt signaling pathway in osteochondral junction (OCJ) and cartilage canal (CC) chondrocytes would be found in early OC when compared to controls. Paraffin-embedded osteochondral samples (7 OC, 8 normal) and cDNA from whole cartilage (7 OC, 10 normal) and chondrocytes surrounding cartilage canals and osteochondral junctions captured with laser capture microdissection (4 OC, 6 normal) were obtained from femoropatellar joints of 17 immature horses. Equine-specific Wnt signaling molecule mRNA expression levels were evaluated by two-step real-time qPCR. Spatial tissue protein expression of b-catenin, Wnt-11, Wnt-4, and Dkk-1 was determined by immunohistochemistry. There was significantly decreased Wnt-11 and increased b-catenin, Wnt-5b, Dkk-1, Lrp6, Wif-1, Axin1, and SC-PEP gene expression in early OC cartilage canal chondrocytes compared to controls. There was also significantly increased b-catenin gene expression in early OC osteochondral junction chondrocytes compared to controls. Based on this study, abundant gene expression differences in OC chondrocytes surrounding cartilage canals suggest pathways associated with catabolism and inhibition of chondrocyte maturation are targeted in early OC pathogenesis. ß

Differences in expression of Wnt antagonist Dkk1 in healthy versus pathological bone samples

“…On one hand, abnormal Wnt signalling in adult tissues may contribute to pathogenesis of musculoskeletal diseases, on the other, in embryonic tissue the same serves as an important regulator of chondrocyte development (Yates et al, 2005). The findings from this study in healthy rats are also in line with the previous study from Kinsley et al (2015). There were low levels of detection of Dkk1 activity in healthy rat tissues in comparison to the pathological (OVX) and necrotic tissues (inflammatory tissue).…”

“…The findings from this study in healthy rats are also in line with the previous study from Kinsley et al . (). There were low levels of detection of Dkk1 activity in healthy rat tissues in comparison to the pathological (OVX) and necrotic tissues (inflammatory tissue).…”

Genetic risk factors for osteochondrosis in various horse breeds

“…An increasing Wnt inhibitor expression (Wif-1, Axin1, Dkk-1) in femoropatellar joint cartilage of OC-affected foals in comparison to OC-non-affected foals [61] may influence the retonic acid signalling pathway and may have an inhibitory effect on chondrocyte maturation [62]. The role of PTH-rP, Wnt/b-catenin signalling and Ihh pathways was shown in several studies [59,61,63] and genes on these pathways partially correspond with OC-risk loci [54] (Supplementary Item 11).…”

Role of Cartilage and Bone Matrix Regulation in Early Equine Osteochondrosis

“…The information gained from this study thus fills a gap in our knowledge base by providing a description of molecular activity during this critical growth period. Samples used in this study contributed to several previous studies evaluating gene and protein expression in foals with and without osteochondrosis, which when evaluated together paint a much more comprehensive picture of the complex molecular events occurring during this process (Kinsley and Kinsley, 201510;Riddick et al, 2012;Semevolos et al, 2018) (Table 9, 10). To date, there is no current model for studies in endochondral ossification and osteochondrosis in children.…”