Functional characterization of hematopoiesis in TIMP-1^−/− mice. (A) Clonogenic assay of BM SP^KLS cells isolated from WT and TIMP-1^−/− mice and sorted as single cells in M3434 MethoCult. CFU-Cs were macroscopically scored at 10, 14, and 18 days after seeding. (B) Spleen-colony assay performed by transplanting 200 000 WBM cells (WT or TIMP-1^−/−) into WT recipients. CFI-S formation was assessed by splenectomy 13 days after transplantation. (C) Schematic representation of the MSCV retroviral expression vectors used to transduce Sca-1⁺ hematopoietic progenitors. The control construct (top) only expresses the reporter gene GFP, whereas the TIMP-1 construct (bottom) allows the coordinated expression of both TIMP-1 and GFP. (D) Proliferation of 32D cells in liquid culture after transduction with MSCV constructs (P < .05; left). (E) For CFU-C assessment, 32D cells were transduced with MSCV vectors and sorted as single cells, after 48 hours, into 96-well plates and grown in MethoCult for 14 days. (F) Primary Sca-1⁺ progenitors (50 000) were transduced with control or MSCV–TIMP-1 constructs and transplanted into recipient mice. CFU-S colonies were analyzed by splenectomy on day 13 after transplantation. Results are reported as mean ± SEM of at least triplicate experiments. *P < .05 and ***P < .001.