Role of heparan sulfate 6-0 endosulfatases in intervertebral disc homeostasis

Shuhei Otsuki¹, Oscar Alvarez-Garcia², Martin K. Lotz² and Masashi Neo<sup>1

1</sup>Department of Orthopedic Surgery, Osaka Medical College, Japan and ²Department of Molecular Medicine, The Scripps Research Institute, USA

Offprint requests to: Shuhei Otsuki M.D, Ph.D, 2-7 Daigakumachi, Takatsuki, Osaka 569-8686, Japan. e-mail: otsuki.shuhei@gmail.com and ort182@osaka-med.ac.jp

Summary. The expression of heparan sulfate endosulfatases (Sulfs) was investigated in the intervertebral disc (IVD) to clarify their role in IVD homeostasis. Sulf-1 and -2 expression were elucidated in normal and degenerated human IVD. Age-related effects on Sulf expression, type II collagen levels, and structural changes were analyzed in IVDs of wild-type (WT) and Sulf-1 knockout (Sulf-1^-/-) mice. The effect of recombinant Sulf-1 (100 ng/ml) and Sulf-1 knockdown on heparan sulfate proteoglycan and collagen expression in ATDC5 cells were examined. Finally, the effect of Sulf-1 on transforming growth factor (TGF) β1-induced signaling was evaluated. Results show that Sulf-1 and -2 levels were higher in degenerated human IVDs. In WT mice, Sulf-1 and -2 expression generally declined as the animals aged. In particular, Sulf-1 in the nucleus pulposus was higher compared with Sulf-2 at the age of 1 and 6 months and significantly declined with aging. Sulf-1^-/- mice showed more severe IVD pathology than WT mice, with lower type II collagen levels in nucleus pulposus, and degeneration with type I collagen in annulus fibrosus. In vitro, Sulf-1 induced type II collagen expression and significantly increased TGF-β1-induced Smad2/3 phosphorylation in ATDC5 cells. In conclusion, Sulf-1 might play a critical role from development to maintenance of IVD homeostasis by regulating collagen expression. Histol Histopathol 34, 1051-1060 (2019)

Key words: Intervertebral disc, Sulf-1, Type II collagen, Smad2/3

DOI: 10.14670/HH-18-107