Nephrectomy Induces Severe Bone Loss in Mice Expressing Constitutively Active TGFβ Receptor Type I

Area of Science:

• Nephrology
• Endocrinology
• Bone Biology

Background:

• Transforming growth factor beta (TGF-β) is a key regulator of renal fibrosis and chronic kidney disease (CKD) progression.
• CKD is known to negatively impact bone remodeling, but the specific role of TGF-β signaling dysregulation in this process remains unclear.

Purpose of the Study:

• To investigate the effects of TGF-β receptor I (TβRI) overexpression on bone remodeling in the context of CKD.
• To determine if TβRI overexpression exacerbates renal injury and bone loss in a mouse model of CKD.

Main Methods:

• Utilized a mouse model with TβRI overexpression controlled by Mx1-Cre (Mx1;TβRI-CKD mice) to study CKD and bone remodeling.
• Assessed renal injury through serum urea nitrogen levels and kidney fibrosis.
• Evaluated bone parameters using micro-computed tomography (μCT) and histomorphometry, alongside gene expression analysis of bone remodeling markers and inflammatory cytokines.

Main Results:

• Mx1;TβRI-CKD mice exhibited exacerbated kidney fibrosis and elevated serum urea nitrogen compared to wild-type CKD controls.
• These mice showed decreased serum calcium, enhanced parathyroid hormone (PTH), and severe osteopenia in femurs and mandibles.
• Histomorphometry revealed reduced tibial cancellous bone volume, increased osteoclastogenesis markers, and decreased osteoblast marker gene expression.

Conclusions:

• TβRI overexpression in CKD mice exacerbates renal injury and leads to significant dysregulation of bone remodeling, resulting in severe bone loss.
• The findings highlight the detrimental role of TGF-β signaling in CKD-induced osteoporosis.
• This research provides a foundation for developing targeted therapies for osteoporosis associated with chronic kidney disease.