Suppression of sost/sclerostin and dickkopf-1 augment intervertebral disc structure in mice

Kroon, Tori; Bhadouria, Neharika; Niziolek, Paul; Edwards, III, Daniel; Choi, Roy; Clinkenbeard, Erica L.; Robling, Alexander; Holguin, Nilsson

Affiliations

¹Department of Biomedical Engineering, IUPUI, Indianapolis, IN, USA

²Department of Mechanical Engineering, Purdue University, West Lafayette, IN, USA

³Radiology & Imaging Sciences, IUPUI, Indianapolis, IN, USA

⁴Indiana Center of Musculoskeletal Health, Indianapolis, IN, USA

⁵Department for Anatomy and Cell Biology, IUPUI, Indianapolis, IN, USA

⁶Department of Mechanical and Energy Engineering, IUPUI, Indianapolis, IN, USA

Abstract and keywords

Intervertebral disc (IVD) degeneration is a leading cause of low back pain, characterized by accelerated extracellular matrix breakdown and IVD height loss, but there is no approved pharmacological therapeutic. Deletion of Wnt ligand competitor Lrp5 induces IVD degeneration, suggesting that Wnt signaling is essential for IVD homeostasis. Therefore, the IVD may respond to neutralization of Wnt ligand competitors sost(gene)/sclerostin(protein) and/or dickkopf-1 (dkk1). Anti-sclerostin antibody (scl-Ab) is an FDA-approved bone therapeutic that activates Wnt signaling. We aimed to (i) determine if pharmacological neutralization of sclerostin, dkk1, or their combination would stimulate Wnt signaling and augment IVD structure and (ii) determine the prolonged adaptation of the IVD to global, persistent deletion of sost. Nine-week-old C57Bl/6J female mice (n = 6–7/group) were subcutaneously injected 2×/week for 5.5 weeks with scl-Ab (25 mg/kg), dkk1-Ab (25 mg/kg), 3:1 scl-Ab/dkk1-Ab (18.75:6.25 mg/kg), or vehicle (veh). Separately, IVD of sost KO and wild-type (WT) mice (n = 8/group) were harvested at 16 weeks of age. First, compared with vehicle, injection of scl-Ab, dkk1-Ab, and 3:1 scl-Ab/dkk1-Ab similarly increased lumbar IVD height and β-catenin gene expression. Despite these similarities, only injection of scl-Ab alone strengthened IVD mechanical properties and decreased heat shock protein gene expressions. Genetically and compared with WT, sost KO enlarged IVD height, increased proteoglycan staining, and imbibed IVD hydration. Notably, persistent deletion of sost was compensated by upregulation of dkk1, which consequently reduced the cell nuclear fraction for Wnt signaling co-transcription factor β-catenin in the IVD. Lastly, RNA-sequencing pathway analysis confirmed the compensatory suppression of Wnt signaling and revealed a reduction of cellular stress-related pathways. Together, suppression of sost/sclerostin or dkk1 each augmented IVD structure by stimulating Wnt signaling, but scl-Ab outperformed dkk1-Ab in strengthening the IVD. Ultimately, postmenopausal women prescribed scl-Ab injections to prevent vertebral fracture may also benefit from a restoration of IVD height and health.

Keywords: ANABOLIC THERAPEUTICS; CHONDROCYTE AND CARTILAGE BIOLOGY; GENETIC ANIMAL MODELS; PRECLINICAL STUDIES; WNT/β-CATENIN/LRPs

Links

DOI: 10.1002/jbmr.4546

PubMed: 35278242

WoS: 000784046600001

History

Received: 2021-07-09

Revised: 2022-03-02

Accepted: 2022-03-10

Cited Works (6)

Year	Entry
2016	Holguin N, Brodt MD, Silva MJ. Activation of Wnt signaling by mechanical loading is impaired in the bone of old mice. J Bone Miner Res. December 2016;31(12):2215-2226.
2014	Holguin N, Brodt MD, Sanchez ME, Silva MJ. Aging diminishes lamellar and woven bone formation induced by tibial compression in adult C57BL/6. Bone. August 2014;65:83-91.
2009	Li X, Ominsky MS, Warmington KS, Morony S, Gong J, Cao J, Gao Y, Shalhoub V, Tipton B, Haldankar R, Chen Q, Winters A, Boone T, Geng Z, Niu Q-T, Ke HZ, Kostenuik PJ, Simonet WS, Lacey DL, Paszty C. Sclerostin antibody treatment increases bone formation, bone mass, and bone strength in a rat model of postmenopausal osteoporosis. J Bone Miner Res. April 2009;24(4):578-588.
2008	Li X, Ominsky MS, Niu Q, Sun N, Daugherty B, D'Agostin D, Kurahara C, Gao Y, Cao J, Gong J, Asuncion F, Barrero M, Warmington K, Dwyer D, Stolina M, Morony S, Sarosi I, Kostenuik PJ, Lacey DL, Simonet WS, Ke HZ, Paszty C. Targeted deletion of the sclerostin gene in mice results in increased bone formation and bone strength. J Bone Miner Res. June 2008;23(6):860-869.
2004	van Bezooijen RL, Roelen BAJ, Visser A, van der Wee-Pals L, de Wilt E, Karperien M, Hamersma H, Papapoulos SE, ten Dijke P, Löwik CWGM. Sclerostin is an osteocyte-expressed negative regulator of bone formation, but not a classical BMP antagonist. J Exp Med. March 15, 2004;199(6):805-814.
2016	Cosman F, Crittenden DB, Adachi JD, Binkley N, Czerwinski E, Ferrari S, Hofbauer LC, Lau E, Lewiecki EM, Miyauchi A, Zerbini CAF, Milmont CE, Chen L, Maddox J, Meisner PD, Libanati C, Grauer A. Romosozumab treatment in postmenopausal women with osteoporosis. NEJM. October 20, 2016;375(16):1532-1543.