Page 61 - 2019_09-HaematologicaMondo-web

MAT mediates metabolic stress in HSPC
ABCDE
FGHIJ
KLMNO
Figure 5. Sympathetic nervous system (SNS)-activated hematopoiesis in control and Adipoq-Cre+;Kitlfl/fl mice. (A and B) 12-week old Kitlfl/fl and Adipoq-Cre+;Kitlfl/fl male mice were treated with the saline vehicle or CL 316,243 for one week. (A) Representative images of femur sections. (B) Quantification of adipocyte numbers in the bone marrow (BM) from the growth plate to 4.5 mm away distally. (C) BM cellularity of 12-week old Kitlfl/fl (n=7 for vehicle and n=6 for CL) and Adipoq-Cre+;Kitlfl/fl (n=8 for vehicle and n=6 for CL) male mice were treated with the saline vehicle or CL 316,243 for one week. (D and E) Relative Kitl mRNA levels in the BM (D) or iWAT (E) of wild-type mice treated with vehicle or CL 316,243 (n=6) for one week. (F-M) 12-week old Kitlfl/fl (n=7 for vehicle and n=6 for CL) and Adipoq-Cre+;Kitlfl/fl (n=8 for vehicle and n=6 for CL) male mice were treated with the saline vehicle or CL 316,243 for one week. LSK number (F), MP number (G), CMP number (H), MEP number (I), GMP number (J), CLP number (K), the MEP/GMP ratio (L), and the CLP/CMP ratio (M) were determined by flow cytometry. (N and O) CL 316,243 treat- ment-induced changes in MEP/GMP ratio (N) and CLP/CMP ratio (O) in Kitlfl/fl (n=6) and Adipoq-Cre+;Kitlfl/fl (n=6) male mice. Data are presented as mean±Standard Deviation. *P<0.05; **P<0.01; ***P<0.001 by two-way ANOVA followed by multiple comparison using Sidak correction (F-M) or unpaired, two-tailed Student t-test (D, N, and O).
β-adrenergic agonists.51,52 We then sought to determine whether MAT-secreted SCF mediates the effect of β3- adrenergic signaling on hematopoiesis. Treatment with CL 316,243 to activate the β3-adrenoceptor for seven days did not change body weight, body fat percentage, MAT mass, or BM cellularity in either Kitlfl/fl or Adipoq-Cre+;Kitlfl/fl mice, when compared to saline controls (Figure 5A-C and Online Supplementary Figure S8A and B). Scheller et al. recently showed that MAT, compared to peripheral WAT, relatively resists lipolysis and remodeling in response to CL 316,243.51 We measured Kitl gene expression and found that CL 316,243 strongly induced Kitl mRNA in the BM but not iWAT (Figure 5D and E). Adipoq mRNA in MAT could be also induced by CL 316,243 (Online Supplementary Figure S8C), suggesting that β3-adrenergic activation is able to remodel MAT. CL 316,243 treatment significantly increased the numbers of LSK, MP, MEP, GMP, and CLP in the wild-type bone marrow (Figure 5F- K). Interestingly, the induction of LSK and MP, in particu- lar MEP, by CL 316,243 was diminished in Adipoq- Cre+;Kitlfl/fl mice (Figure 5F, G, and I). The number of CMP was not affected by CL 316,243 in either control or
Adipoq-Cre+;Kitlfl/fl mice (Figure 5H). CL 316,243-induced increase in GMP and CLP was not dependent on adipocyte-derived SCF (Figure 5J and K). As a result of the loss of adipose SCF, the reduction in MEP/GMP ratio was further decreased, while the increase in CLP/CMP ratio was further augmented in Adipoq-Cre+;Kitlfl/fl mice upon CL 316,243 treatment (Figure 5L-O). These data indicate that SCF from MAT mediates some aspects of homeostatic responses in the BM upon the β3-adrenergic activation. Nonetheless, we cannot exclude the possibility that the role of CL 316,243 on hematopoiesis is affected by lipoly- sis in peripheral WAT.
Compared to the standard housing temperature (22°C), thermoneutrality (30°C) suppresses the SNS, promotes HSPC apoptosis, and increases the radiosensitivity of mice.53 Consistent to the previous finding,53 we did not observe any difference in BM cellularity (Online Supplementary Figure S9A) or the frequency of LSK, MP, and CLP (Online Supplementary Figure S9B) between mice housed at 22°C and 30°C. However, thermoneutral- ity increased the ratio of MEP to GMP and the ratio of CLP to CMP (Online Supplementary Figure S9C and D). After
haematologica | 2019; 104(9)
1739