The HSC defect is rescued by PTH administration in th3 mice. (A) Experimental design of in vivo administration of rat PTH (1-34). Trabecular BMD values of mouse tibiae after 4 weeks of treatment. WT, n = 6; th3, n = 6; th3+PTH, n = 6. (B) Masson’s trichrome and IHC evaluation of collagen-1 deposition in WT, th3, and th3+PTH mice. IHC on BM sections by staining with anti-mouse collagen-I antibody was performed. Original magnification: top ×100; bottom ×200. Quantitative analysis of collagen-1 staining, calculating the IHC⁺ area with image-analysis software. WT, n = 6; th3, n = 6; th3+PTH, n = 6. (C) IHC analysis of JAG1 in BM stromal niche of WT, th3, and th3+PTH mice. Original magnification ×200. Quantitative analysis of JAG1-stained area by image-analysis software. WT, n = 6; th3, n = 6; th3+PTH, n = 6. IHC on BM sections by staining with anti-mouse JAG1 antibody was performed. (D) Evaluation of soluble OPN in BM extracellular fluid of WT, th3 and th3+PTH mice by enzyme-linked immunosorbent assay. WT, n = 4; th3, n = 4; th3+PTH, n = 5. (E) Absolute number of HSCs WT, th3, and PTH-treated th3 mice. WT, n = 14; th3, n = 10; th3+PTH, n = 6. (F) Frequency of quiescent (G0/G1 phase) HSCs in WT, th3, and PTH-treated th3 animals. WT, n = 9; th3, n = 5; th3+PTH, n = 6. (G) Median fluorescence intensity (MFI) of NICD⁺ HSCs in WT, th3, and th3+PTH mice. WT, n = 5; th3, n = 4; th3+PTH n = 4. (H) Chimerism at 4 months after BMT of WT, th3, and th3+PTH cells injected into lethally irradiated WT recipient animals. WT, n = 5; th3, n = 3; th3+PTH, n = 6. *P < .05; **P < .01; ***P < .001.