Figure 3
The development of TPO-induced experimental BM fibrosis in mice requires SPARC. WT and Sparc−/− mice were treated with recombinant TPO to induce myeloproliferation and fibrosis (n = 5 mice per condition, per experiment). Control mice were treated with the medium alone (sterile saline with 1% normal mouse serum). The data represent 1 experiment of the 3 performed. (A) Hematoxylin and eosin and Gomori staining of BM samples from TPO-treated WT and Sparc−/− mice. Hematoxylin and eosin staining shows that TPO administration induced granulocytic and megakaryocytic hyperplasia with MK atypia and cluster formation in both strains (hematoxylin and eosin panels, black arrows), which was not observed in sections from saline-treated mice. A significant degree of stromal fibrosis was observed in WT mice treated with TPO, which is highlighted by the presence of a network of black-stained fibers (Gomori panels, black arrow) and foci of osteosclerosis (Masson trichrome stain, inset). However, BM sections of TPO-treated Sparc−/− mice were completely free of signs of fibrosis similarly to the saline-treated WT and Sparc−/− mice (Gomori panels). Original magnifications ×400. Scale bars represent 50 μm. (B) Histopathologic analysis of the spleen architecture of control and TPO-treated WT and Sparc−/− mice showing that the splenic parenchyma of treated mice is characterized by effacement of the white pulp (WP) because of the expansion of the red pulp (RP) with prominent megakaryocytic hyperplasia and clustering (insets). Original magnifications ×100, insets ×200. Scale bars represent 200 μm. (C) Differential hematopoietic cell counts (mean ± SD) performed on BM sections of WT and Sparc−/− control and treated mice showing the significant increase in BM hematopoietic cells after TPO treatment. In each BM sample, the number of neutrophils, eosinophils, morphologically immature myeloid cells, erythroid cells, MKs, and lymphoid cells was counted of 10 HPFs. *P < .05. (D) Histopathologic grading of BM fibrosis in saline- and TPO-treated WT and Sparc−/− mice performed on Gomori-stained BM sections according to a 4-grade semiquantitative scoring system (see “Methods”). The mean grade of fibrosis is significantly higher in TPO-treated WT mice than in TPO-treated Sparc−/− mice. *P < .05.

The development of TPO-induced experimental BM fibrosis in mice requires SPARC. WT and Sparc−/− mice were treated with recombinant TPO to induce myeloproliferation and fibrosis (n = 5 mice per condition, per experiment). Control mice were treated with the medium alone (sterile saline with 1% normal mouse serum). The data represent 1 experiment of the 3 performed. (A) Hematoxylin and eosin and Gomori staining of BM samples from TPO-treated WT and Sparc−/− mice. Hematoxylin and eosin staining shows that TPO administration induced granulocytic and megakaryocytic hyperplasia with MK atypia and cluster formation in both strains (hematoxylin and eosin panels, black arrows), which was not observed in sections from saline-treated mice. A significant degree of stromal fibrosis was observed in WT mice treated with TPO, which is highlighted by the presence of a network of black-stained fibers (Gomori panels, black arrow) and foci of osteosclerosis (Masson trichrome stain, inset). However, BM sections of TPO-treated Sparc−/− mice were completely free of signs of fibrosis similarly to the saline-treated WT and Sparc−/− mice (Gomori panels). Original magnifications ×400. Scale bars represent 50 μm. (B) Histopathologic analysis of the spleen architecture of control and TPO-treated WT and Sparc−/− mice showing that the splenic parenchyma of treated mice is characterized by effacement of the white pulp (WP) because of the expansion of the red pulp (RP) with prominent megakaryocytic hyperplasia and clustering (insets). Original magnifications ×100, insets ×200. Scale bars represent 200 μm. (C) Differential hematopoietic cell counts (mean ± SD) performed on BM sections of WT and Sparc−/− control and treated mice showing the significant increase in BM hematopoietic cells after TPO treatment. In each BM sample, the number of neutrophils, eosinophils, morphologically immature myeloid cells, erythroid cells, MKs, and lymphoid cells was counted of 10 HPFs. *P < .05. (D) Histopathologic grading of BM fibrosis in saline- and TPO-treated WT and Sparc−/− mice performed on Gomori-stained BM sections according to a 4-grade semiquantitative scoring system (see “Methods”). The mean grade of fibrosis is significantly higher in TPO-treated WT mice than in TPO-treated Sparc−/− mice. *P < .05.

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