Molecular characterisation of idiopathic lumbar kyphosis in pigs

A humpy-backed syndrome of pigs has persisted in the British pork industry and causes of the deformity have been difficult to identify (Penny RHC, 1986). The disease presents challenges in regards to handling the carcass (Holl et al , 2008) and is suspected to slow down growth rate (Straw, Bates, & May, 2009). There is no clear evidence of the biological mechanisms by which kyphosis is induced. Through collecting tissue samples from affected and healthy pigs over 3 age groups, this study aimed to identify molecular mechanisms induced by kyphosis.

A range of tissue samples such as serum, liver, kidney, small intestine, bone and vertebral cartilage were dissected from kyphotic and control pigs at pre-weaning (2 weeks), weaning (5 weeks) and post-weaning (13 weeks). RNA was extracted from tissue samples using the RNeasy lipid tissue mini-kit (Qiagen) and cDNA was synthesised using the Transcriptor first strand cDNA synthesis kit (Roche). Expression levels of BMP7, a marker of bone mineralisation activity, were quantified by qPCR using SYBR green assays (DNA Essential Green Master mix, Roche) and expression levels normalised using the housekeeper gene RPL37.

Preliminary results from qPCR analysis indicated a decrease in BMP7 expression in the vertebral cartilage of pre-weaning kyphotic pigs compared to age matched control pigs. Interestingly, BMP7 expression reduced from pre-weaning to weaning in healthy pigs (P< 0.05) but remained constant for kyphotic pigs in both age groups. The array suggests kyphotic pre-weaners are not achieving sufficient cartilage mineralisation which would otherwise result in normal bone growth and development.

Our initial results indicate reduced bone mineralisation in vertebral cartilage of pre-weaning kyphotic pigs. BMP7 expression was highest in healthy pigs at pre-weaning, most likely to facilitate bone growth in a rapidly growing period of development. Decreased cartilage mineralisation in kyphotic pre-weaners possibly facilitates widening of intervertebral disc space which conforms the spine into the characteristic hump-back. The results suggest that the highest risk of developing kyphosis occurs during the pre-weaning stage. This work was funded by the PROHEALTH project and Newcastle University.

Disclosure of Interest: None Declared.