Figure 5.

Transplantation of Prx1^Cre;Fgfr3^Y367C/+ Periosteal Cells Impairs Bone Healing

(A) Experimental design of Prx1^Cre;Rosa^mTmG;Fgfr3^+/+ (control) and Prx1^Cre;Rosa^mTmG;Fgfr3^Y367C/+ (mutant) PC isolation and transplantation at the fracture site of wild-type host.

(B) Lineage tracing of GFP⁺ control and mutant PCs at 10 days post-fracture. SO staining and SOX9 immunofluorescence on longitudinal sections of host calluses showing SOX9/GFP double-positive cells from control and mutant donor in the cartilage (box 1 and 2). Scale bars, 1 mm and 25 μm (high magnification).

(C and D) Lineage tracing of GFP⁺ control and mutant PCs at days 14 (C) and 21 (D) post-transplantation. SO staining and DAPI/GFP/Tomato fluorescence on longitudinal sections of host calluses (black dotted line). (C) Control PCs differentiate into hypertrophic chondrocytes (hc) (box 3, white arrowhead) but mutant PCs form elongated fibrocartilage cells by day 14 (fc, box 4). (D) Control PCs give rise to osteocytes within new bone trabeculae (b, box 5, white arrowhead) in the center of the callus, whereas mutant PCs form fibrotic (fib, box 6) cells by day 21 leading to pseudarthrosis (black arrow) (n = 5 per group). Scale bars: 1 mm, 100 μm (C, high magnification), and 25 μm (D, high magnification).

(E) Histomorphometric quantification of callus, cartilage, bone, and fibrosis volumes at days 14 and 21 post-fracture and PCs transplantation (n = 5 per group). Values represent mean ± SD. ^∗p < 0.05, ^∗∗p < 0.01 using Mann-Whitney test.