TIMP-1 deficiency subverts cell-cycle dynamics in murine long-term HSCs

Abstract

In addition to the well-recognized role in extracellular matrix remodeling, the tissue inhibitor of metalloproteinases-1 (TIMP-1) has been suggested to be involved in the regulation of numerous biologic functions, including cell proliferation and survival. We therefore hypothesized that TIMP-1 might be involved in the homeostatic regulation of HSCs, whose biologic behavior is the synthesis of both microenvironmental and intrinsic cues. We found that TIMP-1 ؊/؊ mice have decreased BM cellularity and, consistent with this finding, TIMP-1 ؊/؊ HSCs display reduced capability of longterm repopulation. Interestingly, the cell cycle distribution of TIMP-1 ؊/؊ stem cells appears distorted, with a dysregulation at the level of the G 1 phase. TIMP-1 ؊/؊ HSCs also display increased levels of p57, p21, and p53, suggesting that TIMP-1 could be intrinsically involved in the regulation of HSC cycling dynamics. Of note, TIMP-1 ؊/؊ HSCs present decreased levels of CD44 glycoprotein, whose expression has been proven to be controlled by p53, the master regulator of the G 1 /S transition. Our findings establish a role for TIMP-1 in regulating HSC function, suggesting a novel mechanism presiding over stem cell quiescence in the framework of the BM milieu. (Blood. 2011;117(24):6479-6488) IntroductionThe capability of HSCs to maintain the homeostasis of the hematopoietic system is the result of a finely tuned balance between self-renewal and differentiation. The mechanisms responsible for this balance comprise both intrinsic and extrinsic factors, whose crosstalk eventually dictates the fate of stem cells in the framework of the BM niche. [1][2][3] Beside the well-established structural function, the dynamic network of interacting macromolecules that constitutes the extracellular matrix (ECM) represents one of the most powerful sources of extrinsic factors generated by the BM microenvironment. 4 The intricate architecture created by these molecules not only guarantees protection and mechanical support to the stem cell pool but also plays an active role in regulating their behavior. By binding growth factors, regulating their bioavailability, and enabling the interaction with cell-surface receptors, ECM components have been shown to modulate a variety of cellular functions, such as proliferation, survival, and differentiation. 5 ECM dynamic remodeling is controlled by metalloproteinases (MMPs), a class of Zn ϩϩ -dependent proteinases, such as collagenases, gelatinases, and stromelysins, that participate in the digestion of many ECM components, under both physiologic and pathologic conditions. 6 The enzymatic activity of MMPs is counterbalanced by several natural inhibitors, including the tissue inhibitors of metalloproteinases (TIMPs). 7 Both MMPs and TIMPs are expressed by hematopoietic and stromal cells 8 and are decisive regulators of the crosstalk between these 2 cellular entities. The mammalian TIMP family comprises 4 highly conserved members that reversibly block MMP-dependent proteolysis by forming noncovalent 1:1 stoichiometric...

The tissue inhibitor of metalloproteinases 1 increases the clonogenic efficiency of human hematopoietic progenitor cells through CD63/PI3K/Akt signaling

“…Moreover, BM transplantation assays revealed a significant decrease in the capability of TIMP-1 KO cells to sustain long-term engraftment, owing to altered cell cycle dynamics in LT-HSCs [21]. In parallel, we found that an overexpression of TIMP-1 would negatively affect CFU-S Q5 generation after transplantation, whereas, in our current study, the stimulation of human CB progenitors by exogenous rhTIMP-1 resulted in increased clonogenic efficiency.…”

“…In a previous study, we found that the engraftment potential of murine TIMP-1 À/À HSCs is impaired, suggesting that TIMP-1 may play a role in hematopoietic homeostasis [21]. To investigate whether TIMP-1 may also influence the human hematopoietic cell compartment, we first analyzed how exogenous TIMP-1 would modulate the clonogenic potential of human HSPCs.…”

“…More recently, we found that TIMP-1 À/À mice present a consistent decrease in BM cellularity (about 25% decrease as compared with wild-type [WT] mice) and, more specifically, in long-term hematopoietic stem cell (LT-HSC) numbers. In addition, BM transplantation assays revealed a significant decrease in the capability of TIMP-1 knockout (KO) cells to sustain long-term engraftment, owing to altered cell cycle dynamics in LT-HSCs [21].…”

TIMP-1 signaling via CD63 triggers granulopoiesis and neutrophilia in mice

“…17 Interestingly, TIMP-1 was concurrently discovered as erythroid potentiating activity (EPA), 46 a factor that stimulated proliferation of human erythroid progenitors, 47 and this effect was found to be independent of protease inhibition. 48 Furthermore, the hematopoietic stem cell (HSC) compartment was shown to be functionally impaired in TIMP-1 knockout mice 49 and engraftment of HSPCs after BM transplantation was promoted by TIMP-1. 50 These studies are in line with our finding that TIMP-1 impacts on the hematopoietic system, particularly via its signaling domain.…”

“…48 Furthermore, the hematopoietic stem cell (HSC) compartment was shown to be functionally impaired in TIMP-1 knockout mice 49 and engraftment of HSPCs after BM transplantation was promoted by TIMP-1. 50 These studies are in line with our finding that TIMP-1 impacts on the hematopoietic system, particularly via its signaling domain.…”