Changes in the BM cavity of Rs1 mice. (A) Representative photographs of femurs from 6-week-old (6 wk) and 12-week-old (12 wk) control (Ctrl) and ColI(2.3)⁺/Rs1⁺ (Rs1) mice. Scale bar represents 1 cm. (B) Dual-energy x-ray absorptiometry measurements of bone mineral density (BMD) in age-matched Ctrl and Rs1 littermates (n = 6-15 mice per group). (C-F) Hematoxylin and eosin staining of decalcified femurs from 12-weeks-old Ctrl and Rs1 mice. Low magnification (C) showing loss of the normal BM canal and gross morphologic bone changes. Scale bar represents 2 mm. High magnification showing hematopoietic BM cells and cortical bone in Ctrl (D) and Rs1 bone containing fibrous infiltrate and disorganized trabeculae (E) and hematopoietic BM cells (F) intermingled with fibrocellular infiltrate. c indicates cortical bone; bm, BM space; t, trabecular bone; and f, fibrous stromal cells. Scale bar represents 100 μm. (G) Micro-CT analysis on femurs of 15-week-old (15 wk) Ctrl (n = 4) and Rs1 (n = 5) mice. Scale bar represents 1 mm. TV and mineralized BV were determined on 50 mid-femur slices. (H) Enumeration of BM hematopoietic cell numbers released by crushing and extensive washing of bones isolated from 6-week-old and 12-week-old Ctrl and Rs1 mice (n = 6-13 per group). (I) Enumeration of BM Lin⁻/CD45⁻ endosteal stromal cells released by collagenase-digestion from the crushed bones of 12-week-old control and Rs1 mice. Data are mean ± SD. *P ≤ .05. **P ≤ .01. ***P ≤ .001.