Blocking CCN2 Reduces Established Bone Loss Induced by Prolonged Intense Loading by Increasing Osteoblast Activity in Rats

Abstract

We have an operant model of reaching and grasping in which detrimental bone remodeling is observed rather than beneficial adaptation when rats perform a high‐repetition, high‐force (HRHF) task long term. Here, adult female Sprague–Dawley rats performed an intense HRHF task for 18 weeks, which we have shown induces radial trabecular bone osteopenia. One cohort was euthanized at this point (to assay the bone changes post task; HRHF‐Untreated). Two other cohorts were placed on 6 weeks of rest while being simultaneously treated with either an anti‐CCN2 (FG‐3019, 40 mg/kg body weight, ip; twice per week; HRHF‐Rest/anti‐CCN2), or a control IgG (HRHF‐Rest/IgG), with the purpose of determining which might improve the trabecular bone decline. Results were compared with food‐restricted control rats (FRC). MicroCT analysis of distal metaphysis of radii showed decreased trabecular bone volume fraction (BV/TV) and thickness in HRHF‐Untreated rats compared with FRCs; responses improved with HRHF‐Rest/anti‐CCN2. Rest/IgG also improved trabecular thickness but not BV/TV. Histomorphometry showed that rest with either treatment improved osteoid volume and task‐induced increases in osteoclasts. Only the HRHF‐Rest/anti‐CCN2 treatment improved osteoblast numbers, osteoid width, mineralization, and bone formation rate compared with HRHF‐Untreated rats (as well as the latter three attributes compared with HRHF‐Rest/IgG rats). Serum ELISA results were in support, showing increased osteocalcin and decreased CTX‐1 in HRHF‐Rest/anti‐CCN2 rats compared with both HRHF‐Untreated and HRHF‐Rest/IgG rats. These results are highly encouraging for use of anti‐CCN2 for therapeutic treatment of bone loss, such as that induced by chronic overuse. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Spatial Transcriptomics in Bone Mechanomics: Exploring the Mechanoregulation of Fracture Healing in the Era of Spatial Omics

“…Coincident with this enhanced osteogenic response, Ccn2 (-3.7 fold) – a master regulator of osteogenesis and chondrogenesis ( 21 ), Nbl1 (-2.1 fold) – a BMP-antagonist ( 22 ), and Mgp (-1.4 fold) – a potent mineralization inhibitor ( 23 , 24 ), were downregulated (Figure 5[B]; Supplementary Table 2). Osteoclast markers were less prominent in the results with expression of Ctsk and Acp5 not significantly different between Control and Loaded fracture sites and upregulation of genes associated with osteoclastogenesis ( 25 , 26 ) and osteoclast activity ( 26–29 ): s100a8 (+2.3 fold), Ncf1 (+1.6 fold) and Mmp9 (+0.8 fold) (Figure 4 [H] – [J]; Figure 5[B][C]; Supplementary Table 2).…”

“…Known mechano-responsive genes were also present amongst the top-ranked genes including: Il11 (+17.5 fold) – a cytokine predominantly expressed in bone ( 30 , 31 ), Ccn2 (-3.7 fold) ( 21 , 32 ), Wnt7b (+3.4 fold) ( 33 , 34 ), Sost (+2.2 fold) – a Wnt-antagonist ( 35 , 36 ), Gja1 (+2.0 fold) – which encodes for the gap junction protein connexin 43 ( 37 ), Sfrp4 (-1.4 fold) – a Wnt-antagonist ( 38–40 ), and Cdkn1a (-0.7 fold) – a negative regulator of osteogenesis ( 41 , 42 ) (Figure 5[B][C]; Supplementary Table 2).…”

Blocking CCN2 Reduces Established Palmar Neuromuscular Fibrosis and Improves Function Following Repetitive Overuse Injury

“…Results were compared to age-matched controls that received IgG treatment (Control+IgG). The design of this study has been previously diagrammed [ 33 , 34 , 37 ].…”

“…This is the fourth study of a series examining tissues from the same animals [ 33 , 34 , 37 ]. Unique to this study is the examination of (1) collagen deposition in forepaw muscles and nerves; (2) histopathological changes in entheses through which involved muscles attach to underlying bones; (3) sensorimotor changes (forepaw mechanical allodynia and forelimb reflexive grip strength) reported as percent change from baseline levels by study end (24–30 weeks later), and whether these behavioral changes correlate with forepaw tissue histopathology.…”

“…In nerves, the secondary treatment with anti-CCN2 reduced task-induced increases in CCN2, collagen type 1, and degraded myelin basic protein in the median nerve at the wrist [ 33 ]. Additionally, task-induced losses in forelimb trabecular bone volume were rescued in anti-CCN2-treated animals via enhanced osteoblast numbers and activity [ 37 ].…”