Expression of human CSF-1 in the humanized CSF-1 mice. (A) Indicated organs from CSF1^m/m and CSF1^h/h were isolated, RNA was extracted- and reverse transcription (RT)–PCR analysis was performed either using mouse CSF-1 (top) or human CSF-1 (middle) specific primers. HPRT levels (bottom) was used as controls for the input cDNA. Data are representative of 2 independent experiments. (B) Indicated organs from CSF1^h/m were isolated, RNA was extracted and RT-PCR analysis was performed either using mouse CSF-1 (top) or human CSF-1 (bottom) specific primers. RNA extracted either from mouse liver or human fetal liver served as positive controls for mouse and human primer pairs, respectively, no RT, and no template PCR reactions served as negative controls. Data are representative of 2 independent experiments. (C) Bone Associated Stromal Cells from CSF1^m/m, CSF1^h/m, and CSF1^h/h mice were isolated and cultured in vitro for 10 days. Cells were lysed, RNA was extracted, and real-time PCR analysis was performed using either mouse CSF-1 (white) or human CSF-1 (black) specific primers. Shown are the mean values of duplicate samples. Error bars indicate ± SEM. Input cDNA quantity was normalized according to HPRT (hypoxanthine guanine phosphoribosyl transferase) expression levels. Data are representative of 2 independent experiments. (D) Bone Associated Stromal Cells from CSF1^m/m, CSF1^h/m, and CSF1^h/h mice were isolated and cultured in vitro for 10 days. Cell culture supernatants were collected and the secreted levels of mouse (white) and human (black) CSF-1 were quantified using species specific CSF-1 ELISA kits. Shown are the mean values of triplicate samples. Error bars indicate ± SEM. Data are representative of 2 independent experiments. (E) CSF1^m/m, CSF1^h/m, and CSF1^h/h mice were bled and the serum levels of human and mouse CSF-1 were quantified through ELISA. Shown are the mean values of triplicate samples. Error bars indicate ± SEM.