Diminished Chondrogenesis and Enhanced Osteoclastogenesis in Leptin-Deficient Diabetic Mice (ob/ob) Impair Pathologic, Trauma-Induced Heterotopic Ossification

Abstract

Diabetic trauma patients exhibit delayed postsurgical wound, bony healing, and dysregulated bone development. However, the impact of diabetes on the pathologic development of ectopic bone or heterotopic ossification (HO) following trauma is unknown. In this study, we use leptin-deficient mice as a model for type 2 diabetes to understand how post-traumatic HO development may be affected by this disease process. Male leptin-deficient (ob/ob) or wild-type (C57BL/6 background) mice aged 6-8 weeks underwent 30% total body surface area burn injury with left hind limb Achilles tenotomy. Micro-CT (mCT) imaging showed significantly lower HO volumes in diabetic mice compared with wild-type controls (0.70 vs. 7.02 mm 3 , P < 0.01) 9 weeks after trauma. Ob/ob mice showed evidence of HO resorption between weeks 5 and 9. Quantitative real time PCR (qRT-PCR) demonstrated high Vegfa levels in ob/ob mice, which was followed by disorganized vessel growth at 7 weeks. We noted diminished chondrogenic gene expression (SOX9) and diminished cartilage formation at 5 days and 3 weeks, respectively. Tartrate-resistant acid phosphatase stain showed increased osteoclast presence in normal native bone and pathologic ectopic bone in ob/ob mice. Our findings suggest that early diminished HO in ob/ob mice is related to diminished chondrogenic differentiation, while later bone resorption is related to osteoclast presence.

Impact of hyperglycemia and treatment with metformin on ligature-induced bone loss, bone repair and expression of bone metabolism transcription factors

“…Up to now, no study has evaluated the expression of this transcription factor after extraction, relative to bone repair of fractures. Studies have demonstrated a delay in repair in diabetic animals, which is in agreement with the results obtained in the present study [ 33 – 35 ].…”

Endogenous CCN family member WISP1 inhibits trauma-induced heterotopic ossification

“…CCN family members were first examined in a model of trauma-induced HO. Complete Achilles tenotomy, coupled with cutaneous dorsal burn injury, results in a well-characterized incidence of HO at the tenotomy site, replicating human disease (21)(22)(23)(24)(25). First, bulk RNA sequencing was performed at the tenotomy site and compared with the contralateral tendon site of the same animal (serving as an internal control) at 3 weeks after injury ( Figure 1).…”

Effect of Leptin Deficiency on the Skeletal Response to Hindlimb Unloading in Adult Male Mice

“…Leptin has differential effects on osteoclast number and activity in weight-bearing mice. ob/ob mice have normal or increased osteoclast-lined bone perimeter 25,26 , indicating that the hormone is not required for osteoclastogenesis. Indeed, subcutaneous administration of leptin attenuates ovariectomy- and HU-induced bone loss in rats by reducing osteoclast number 3,27 .…”