Figure 2. Osteolectin⁺ cells are short-lived osteogenic progenitors.

(a) Percentage of CFU-F colonies that were Tomato⁺ when formed by bone marrow cells from 2 month-old Lepr^cre/+; Rosa26^{loxp-tdTomato/+} or Oln^iCreER/+; Rosa26^{loxp-tdTomato/+} mice, 3 days after tamoxifen administration (4 independent experiments). (b) Percentage of LepR⁺, LepR⁺Oln-mTomato⁺, and LepR⁺Oln-mTomato⁻ bone marrow stromal cells that formed CFU-F colonies. (c and d) Osteogenic (c) and adipogenic (d) differentiation of adherent cells cultured from LepR⁺Oln-mTomato⁺ or LepR⁺Oln-mTomato⁻ stromal cells (6 independent experiments in b-d). (e) The average numbers of perilipin⁺ adipocytes or alkaline phosphatase⁺ (ALP⁺) osteogenic cells that spontaneously differentiated per CFU-F colony after 1 week of culture (4 independent experiments). (f) Percentage of LepR⁺, LepR⁺Oln-mTomato⁺ and LepR⁺Oln-mTomato⁻ bone marrow stromal cells that incorporated a 24-hour pulse of BrdU in vivo (4 independent experiments). (g) Oln^iCreER/mT; Rosa26^loxp-EGFP/+ mice were treated with tamoxifen at 2 months of age and the percentage of Oln-Tomato⁺ cells that were EGFP⁺ was assessed (3 independent experiments). (h and i) Oln^iCreER/+; Rosa26^{loxp-tdTomato/+}; Col1a1*2.3-EGFP mice were treated with tamoxifen at 2 months of age and the percentages of LepR⁺ stromal cells (h) and Col1a1*2.3-EGFP⁺ osteoblasts (i) that were Tomato⁺ was assessed (5 independent experiments). (j) Bone, adipocytes, and hematopoiesis in ossicles formed by CFU-F cultured from LepR⁺Oln-mTomato⁺ or LepR⁺Oln-mTomato⁻ stromal cells (80 ossicles per cell population derived from 20 mice in 5 independent experiments). (k-l) Femurs were fractured 3 days after tamoxifen administration to Oln^iCreER/+; Rosa26^{loxp-tdTomato/+}; Col1a1*2.3-EGFP mice. Two weeks later the number of LepR⁺ cells per femur (k) and the percentage of LepR⁺ cells that were Tomato⁺ (l) were assessed (5 independent experiments). All data represent mean ± SD. Statistical significance was assessed using an unpaired t-test (a), paired t-tests (c, k, l), matched samples one-way ANOVAs followed by Tukey’s multiple comparisons tests (b, f), Wilcoxon test (d), Wilcoxon test followed by Holm-Sidak’s multiple comparisons adjustment (e), or Cochran-Mantel-Haenszel test (j).