Targeting Macrophages As a Candidate for Tissue Regeneration

Macrophages and Tissue Regeneration Zhang et al.

Curr. Issues Mol. Biol. (2018) 29: 37-48. caister.com/cimb

Snapshot: Targeting Macrophages as a Candidate for Tissue Regeneration

Jing Zhang1,2,3, Yang Yang4, Zhi Yang4,5, Tian Li4,5 and Fulin Chen1,2,3* Introduction Macrophages, also known as "big eaters" due to 1Lab of Tissue Engineering, College of Life their phagocytic capacity, were first annotated by Sciences, Northwest University, 229 Taibai North Mechnikov in the late 18th century (Fraga et al., Road, Xi'an, 710069, P. R. China 2017; Tauber, 2003; Wan et al., 2017). They are a 2Provincial Key Laboratory of Biotechnology of specific mononuclear cell group abundant in almost Shaanxi, 229 Taibai North Road, Xi'an, 710069, P. every organ of higher animals. In mammals, R. China macrophages can derive from the yolk sac, fetal 3Key Laboratory of Resource Biology and liver, and bone marrow (Geissmann et al., 2010; Biotechnology in Western China Ministry of Wynn et al., 2013). Their differentiation is Education, 229 Taibai North Road, Xi'an, 710069, P. orchestrated by multiple growth factors (GFs) R. China. (Gordon, 2003; Sica et al., 2012). Tissue-resident 4College of Life Sciences, Northwest University, 229 macrophages, usually originating from the bone Taibai North Road, Xi'an, 710069, P. R. China marrow hematopoietic progenitors, has the ability of 5Department of Biomedical Engineering, The Fourth self-renewing (Geissmann et al., 2010; Jenkins et Military Medical University, 169 Changle West Road, al., 2011; Schulz et al., 2012; Davies et al., 2013). Xi'an 710032, China Generally, they are divided into two phenotypes, classically activated M1 macrophages and * Correspondence: [email protected] alternatively activated M2 macrophages, which refer to the state activated by Th1 and Th2 lymphocytes DOI: https://dx.doi.org/10.21775/cimb.029.037 or with interferon-gamma (INF-γ) and interleukin 4 (IL-4), respectively (Goerdt et al., 1999; Gordon, Abstract 2003; Sica et al., 2012). This phenomenon is Macrophages are a specific mononuclear cell group described as heterogeneity or polarization. abundant in almost every organ of higher animals. This group is a pivotal part of the immune system Tissue regeneration plays an important role in and is involved in immune responses against cardiovascular diseases (Sengupta et al., 2010; exogenous antigen invasion. Recently, Wang et al., 2013), cerebrovascular diseases accumulating evidence has demonstrated that (Wang et al., 2013), and neoplasms (Jin et al., macrophages participate in wound repair and tissue 2017), three major killers among human across the regeneration. In this review, we will first introduce world (Jiang et al., 2017; Li et al., 2017; Liang et al., the influences of regeneration after injury in various 2017; Lv et al., 2017; Ma et al., 2017; Wu et al., tissues and organs among macrophage-depleted 2018; Xin et al., 2018; Zhang et al., 2018). The animal models. Second, the possible relationship primary function of a macrophage is to serve as the between macrophages and reparation capacities effector of the innate immune system (Saini et al., will be discussed. Finally, we provide a general idea 2016; Jackaman et al., 2017; Liang et al., 2017; about the roles of macrophages in the injury- Rahimifard et al., 2017; Ren et al., 2017). regeneration process and then discuss the current Accompanied by monocytes, macrophages occupy challenges and prospects of their clinical the front line of innate defense against exogenous application. The information compiled here may be antigens. They are highly flexible cells that exhibit useful for regenerative research and may promote dramatic changes in phenotypes in response to macrophages as a therapeutic target in regenerative stimuli from neighboring tissues/cells and/or the medicine. external environment. They promptly infiltrate into

!37 Macrophages and Tissue Regeneration Zhang et al. the pathogen invasion site of the organism, clear Scientists have discovered that macrophages are debris, and secrete chemokines and cytokines to involved in the repair of brain vascular rupture and initiate inflammation procedures, drive acquired regeneration of peripheral nerves. Because vascular immune responses and subsequently promote injury endothelial growth factor (VEGF) is one of the key resolution from a morbid status (Gordon et al., 2005; factors in angiogenesis (Pollard, 2009; Fantin et al., Hume, 2006; Hume, 2008; Geissmann et al., 2010; 2010), Cattin and co-researchers (Cattin et al., Hume et al., 2012; Wynn et al., 2013). Additionally, 2015) used the Cre system and created transgenic macrophages fulfill indispensable functions in the mice in which the production of VEGFα in patterning and formatting of tissues during macrophages is inhibited. In the abovementioned developmental and mature stages. They are work, they found that the loss of VEGFα did not involved in erythropoiesis (Kawane et al., 2001), inhibit macrophage recruitment during the early hematopoiesis (Gordy et al., 2011)(Gordy et al., stage of nerve regeneration. However, a reduction 2011), angiogenesis (Rao et al., 2007; Machnik et in vascularization was observed in mutant animals, al., 2009; Fantin et al., 2010; Stefater III et al., leading to the restraint of Schwann cells (SCs) at 2011), osteogenesis (Niida et al., 1999; Pollard, the stump site. Consequently, these cells failed to 2009), and neural homeostasis (Pollard, 2009; form tube-like structures, which are necessary to Erblich et al., 2011). Furthermore, macrophages direct axons back to their original targets. maintain metabolic homeostasis in adult mammalian Meanwhile, by studying transgenic zebrafish models organs, such as adipose tissue, the liver, and the (Liu et al., 2016), another group demonstrated that pancreas (Weisberg et al., 2003; Odegaard et al., in some cases, following cerebrovascular rupture, 2007; Kang et al., 2008; Olefsky et al., 2010; macrophages were recruited by extracellular ATP Nguyen et al., 2011; Odegaard et al., 2013). and formed direct physical adhesions with both However, chronically activated macrophages lead to epithelial ends. With the help of mechanical forces, a prolonged inflammatory reaction, which triggers both the broken ends of cerebral vessels could be substantial adjunctive tissue destruction. Indeed, successfully reconnected, and a functional vessel these unregulated macrophages contribute to was then restored (Figure 1, Table 1). Thus, various chronic inflammatory and autoimmune macrophages promote the migration of SC and diseases, including atherosclerosis, asthma, maintain the homeostasis of peripheral neural rheumatoid arthritis, and fibrosis (Kamada et al., network by secreting cytokines, making physical 2008; Hansson et al., 2011; Libby et al., 2011; ligation, and assisting neovessel formation. Murray et al., 2011). Apart from the disease- promoting effect, clinical and experimental evidence Fracture healing has demonstrated that macrophages participate in Macrophages have also been involved in bone tumor initiation, progression, and metastasis (Marelli healing. Schlundt et al. produced unilateral closed et al., 2017; Yao et al., 2017). fractures in 8-week-old mice (Schlundt et al., 2015). They used a well-developed medical intravenous In this review, we aimed to mainly focus on the injection method to selectively deplete mouse mechanism by which macrophages contribute to macrophages. This fabulous work was performed by tissue/organ injury repair. We will first introduce the Dutch scientists VanRooijen and Van Nieuwmegen influences of regeneration after injury in various in 1984. The approach is to introduce an effector tissues and organs among macrophage-depleted molecule, liposome-carried dichloromethylene animal models. Second, the possible relationship diphosphonate, specifically called clodronate between macrophages and reparation capacities liposome, into the organism (Van Rooijen et al., will be discussed. Finally, we provide a general idea 1984). This compound has been shown to have about the roles of macrophages in the injury- high affinity for calcium and, thus, adheres to the regeneration process. Collectively, this review will mononuclear phagocyte system (MPS). At the serve as a comprehensive reference and hopefully cellular and molecular levels, the accumulated aid in the design of future research and provide a intracellular effectors caused a "liposome-mediated potential therapeutic target in therapeutic methods. macrophage suicide" effect, leading to the death of the macrophages (Figure 2). This novel method is Macrophage depletion and tissue regeneration reversible and less toxic, demonstrating effective elimination of macrophages in various organs, such Blood vessel rupture and/or nerve regeneration as the spleen, lung, and testis (Van Rooijen et al., Physical damage of the brain is usually 1985; Thepen et al., 1989; van Rooijen et al., 1989; accompanied by the rupture of blood vessels. Delemarre et al., 1990; Van Rooijen et al., 1990;

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Fig 2.

Figure 1. Roles of macrophage in regeneration. Accumulated studies have demonstrated that macrophage participated in regeneration in different organisms. In human, macrophage is able to promote regeneration of bone fracture, vessel rupture, and skin wound. Besides, it can also promote appendage growth of zebrafish and newt. 29

Table 1. Summary of macrophage involvement and function in different regeneration processes.

Organ/tissue/body parts Model Mechanism Macrophage function Reference

Blood vessel/nerve Zebrafish PI3K and Rac1 mediate mechanical Facilitating the ligation of vessel (Cattin et al., 2015; Liu et al., 2016) traction of macrophages. The cords of endothelial rupture. Schwann cells, which interact directly with Secreting VEGF-A to induce polarized blood vessels, are used as scaffolds by blood vessels and drive angiogenesis. axons to cross the rupture ‘bridge’. Appendage Salamander Appropriate TGF-β1 signaling activation Orchestrating the early response to injury (Godwin et al., 2013; Petrie et al., 2014) and zebrafish and cytokine production in limb and activation of subsequent limb regeneration. regeneration.

Wnt/β-catenin signaling partially modulates Impacting the proliferative capacity of the cellular and biochemical events in tail blastema and extent of tail fin regeneration. regeneration in a stage-dependent manner.

Skin/muscle Mouse CX3CR1 enhances phagocytosis and Phagocytosing necrotic muscle fibers and (Zhao et al., 2016) muscle trophic growth factor production. neutrophils. Brain Mouse Recruitment of MOs/MPs via CCR2 and Stabilizing the neurovascular unit in the (Gliem et al., 2012) activating TGF-β1 signaling pathway. subacute stage. Bone Mouse Changing of the macrophage phenotype Improving callus mineralization and (Raggatt et al., 2014; Schlundt et al., 2015) from M1 to M2, thus enhancing the anti- endochondral ossification. inflammatory signaling cascade.

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Bergh et al., 1993; Biewenga et al., 1995; Van et al., specific suicide gene-activating ligand, 1996; Van Rooijen et al., 1996). Using this strategy, macrophages can be temporally depleted at any of researchers have found that an enduring the interested phases. Using this strategy to study macrophage depletion resulted in non-union and femoral fracture mouse models, Raggatt found that impaired callus mineralization, appearing as a lower soft callus formation in mice with ablated callus and bone volume. Both type II and type X macrophages at the initial time of surgery was collagens, which should graduate into mineralized totally blocked because cartilage, and woven bone tissue in the late healing phase, were still detectable formations were absent. When AP20187 was at 21 days in animals from the macrophage- delivered at the initiation of the early anabolic depletion group. This is a clear message that phase, some animals exhibited a small but endochondral ossification was severely disturbed in morphologically normal callus, whereas others had mice without sufficient macrophages. A similar minimal or no soft callus formation. Overall, failure of bone reconstruction was observed by macrophage depletion remarkably impacts Raggatt's research group (Raggatt et al., 2014). endochondral callus formation and normal bone They created transgenic mice, in which mature anabolism, thus influencing subsequent fracture myeloid cells carried a Fas-based suicide gene. healing. For more details on macrophage-depleted When these mice were treated with AP20187, the animal models, please refer to Figure 2.

Fig 1.

Figure 2. Acquisition of macrophage-depleted animal models. Clodronate (dichloromethylene diphosphonate) is artificially encapsulated in liposome, suspended in sterile phosphate buffered saline. After intravenous injection, clodronate liposome will be firstly ingested and digested by macrophage, and further contribute to the release of cytotoxic molecular clodronate. The intracellular release and accumulation of clodronate at a certain concentration may induce apoptosis of the macrophage. By this approach, temporally macrophage-depleted animal models are created, which offers opportunity for re- searching macrophages in vivo.

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2007; Contreras-Shannon et al., 2007; Sun et al., Viscera damage repair 2009; Lu et al., 2011; Lu et al., 2011). Inspired by Macrophages are also involved in the damage this discovery, instead of using the macrophage- repair of internal organs of the body. Duffield et al. knock-out system, Zhao and colleagues (Zhao et (Duffield et al., 2005) created a carbon tetrachloride al., 2016) generated CX3CR1 mutant transgenic (CCl4) fibrosis model and observed the liver mice as models, in which the function of regeneration status in transgenic mice lacking macrophage was impaired. In barium chloride macrophages. They found that macrophages acted (BaCl2)-injected acute muscle injury mouse models, differently during the injury and repair phases. In both the number of necrotic fibers and percentage progressive inflammatory injury, macrophage of the necrotic area at 7 d were significantly depletion resulted in the amelioration of fibrosis. augmented compared with the WT controls, However, depleting macrophages during the indicating unsuccessful injury repair. In general, recovery stage led to failure of resolution with the macrophages seem to promote wound closure as persistence of cellular and matrix components of the well as dermal healing and are important to skeletal fibrotic response. Duffield et al. also discovered that muscle injury repair by regulating tropic growth two subgroups of macrophages: circulating factor production and the cytokine microenviron- monocytes and hepatic resident cells, plays pivotal ment. roles in tissue injury and regeneration. It was also demonstrated that an insufficient number or Appendage regrowth dysfunction of macrophages is related to delayed In contrast to mammals, some vertebrate and clinical deterioration and hemorrhagic conversion of amphibian species can regenerate scarless tissues infarctions in mouse models of ischemic stroke. (Lévesque et al., 2010) or even whole body parts, Frequent bleeding and dilated neovessels in the such as limbs, fins, the spinal cord, the tail, and infarct border zone were also observed (Gliem et sections of the heart and brain (Brockes et al., 2002; al., 2012). Another group, Vinuesa et al., first treated Ferretti et al., 2003; Brockes et al., 2005; Parish et mice with clodronate liposome and then used the al., 2007; Singh et al., 2010; Jiang et al., 2017; Li et same ischemia/reperfusion surgery approach to al., 2017; Ma et al., 2017; Siegel et al., 2017; Di et study kidney damage in models lacking al., 2018; Li et al., 2018). In salamanders, loss of an macrophages found that the absence of entire limb can be regenerated within weeks. Using macrophages blocked the repair process, while re- the clodronate-liposome-depletion strategy again, injection of RAW 264.7 in macrophage recovered Godwin and colleagues found that early the regeneration ability of the organism, by macrophage engagement is crucial for limb augmenting cell proliferation and secreting anti- regeneration (Godwin et al., 2013). They observed inflammatory cytokines in post-reperfusion period that the deletion of macrophages before and during (Vinuesa et al., 2008). early amputation days in axolotl exacerbated fibroplasia and collagen deposition, inhibiting Repair in skin wound and muscle injury blastema formation at the amputated limb site, thus The skin is the first barrier of animals against repressing limb regrowth. On the other hand, external invaders; therefore, wound healing appears macrophage interference during a later stage after to be particularly important to organisms. A study blastema formation only resulted in delayed limb shows that macrophages are inextricably involved in redevelopment associated with the reduction of skin regeneration. Transgenic mice with depleted vascularization, which appears less harmful to the macrophages demonstrated delayed wound axolotl itself. closure, reduced granulation tissue formation and collagen deposition, impaired angiogenesis and Using the combination of cell tracking and genetic decreased cell proliferation during wound healing cell ablation approaches in zebrafish fin (Mirza et al., 2009). It has been demonstrated that regeneration research, Petrie et al. (Petrie et al., the macrophage subtype was recruited soon at the 2014) found that macrophages responded quickly lesion site after acute skeletal muscle injury via after the blastema formation stage in the tail fin CCR2, a chemokine type 2 receptor expressed on regeneration process. In transgenic zebrafish the surface of monocytes/macrophages, and its lacking macrophages, the extent of new fin tissue ligand monocyte chemoattractant protein-1. Next, growth was decreased compared with that of WT hi these macrophages switched into the CX3CR1 / fish. Moreover, these fish demonstrated scattered Ly-6Clow subtype to produce cytokines to distinct areas of abnormal tissue regeneration along accomplish muscle regeneration (Arnold et al., the fin. Moreover, Petrie et al. identified stage-

!41 Macrophages and Tissue Regeneration Zhang et al. dependent functional roles of macrophages in nitrogen and oxygen intermediates, which exert appendage outgrowth of adult zebrafish. They microbicidal and tumoricidal activity. In contrast, M2 observed that the lack of macrophages throughout macrophage can secret scavenging molecules that blastema formation during early amputation stage, participate in tissue remodeling and immuno- led to the inhibition of regeneration. On the other regulation (Mills et al., 2000; Sica et al., 2012; Mills hand, depleting macrophages during the later tissue et al., 2014; Zhou et al., 2014). Hence, changes in outgrowth phase did not significantly affect the microenvironmental factors in the first few days of regeneration rate but resulted in an elevated bone fracture led to the switch of M1 macrophage to aberrant growth phenotype (33% compared with M2. This transformation promotes the secretion of 16% in the control group and 9% in the WT group). anti-inflammatory cytokine and bone regeneration. The depletion of macrophages during these two stages caused the failure of wound closure and Signaling pathways aberrant fin patterning. Interestingly, no similar Signaling pathways also participate in the process results were observed in mouse models so far (Dovi of regeneration. After myocardial infarction (MI), the et al., 2003; Martin et al., 2009; Mirza et al., 2009; Wnt pathway is activated in mice. Palevski et al. Evans et al., 2013). (Palevski et al., 2017) demonstrated that macrophages, recruited by MI, contributed to non- Mechanism of macrophages involved in canonical activation because they highly expressed regeneration non-canonical Wnt ligands. Interestingly, the knockout of the Wnt ligand essential transporter Excreted factors Wntless (Wls) in macrophages, which inhibited The primary role of macrophages associated with ligand secretion, blocked the inflammatory autocrine regeneration is their remarkable capacity for loop and resulted in a shift toward the M2-like cytokine secretion. Macrophages have significant phenotype. These Wls-deficient M2-like beneficial improvement in inducing angiogenic macrophages exhibited anti-inflammatory character- activity during blood vessel regeneration. One of the istics and displayed augmented expression of well-known angiogenesis molecules produced by inducible nitric oxide synthase (iNOS), transforming macrophages is the multifunction-factor VEGF growth factor-β1 (TGFβ1), and insulin-like growth (Breen, 2007). During peripheral nerve rupture, factor 1 (IGF1), which are positive factors to macrophages could selectively sense the hypoxic promote ischemic injury protection, infarct healing, environment between the proximal and distal stump and myocardial repair. and then secrete VEGFA to induce the polarized vasculature. Schwann cells can then use these Another report proved that a single macrophage newly generated blood vessels as "tracks" to cross was sufficient to generate mechanical traction the bridge, taking regrowing axons with them and forces to pull the endothelial ends of brain vascular assist the accomplishment of nerve regrowth (Cattin rupture and facilitating their ligation, thus mediating et al., 2015). In the course of wound healing, vessel regeneration (Liu et al., 2016). Transcript- macrophage knockout mice exhibit disorganized ional profile analyses identified the upregulation of cytokine expression at the wound bed, and the phosphatidylinositol-3-kinase (PI3K) and Ras- chaos resulted in disabled injury repair (Mirza et al., related C3 botulinum toxin substrate 1 (Rac1) in 2009). During fracture healing, either Fas- (Raggatt macrophages at the lesion site. PI3K and Rac1 et al., 2014) or clodronate liposome injection- coordinated actin polymerization in microfilaments induced (Schlundt et al., 2015) macrophage to accomplish the filopodia/lamellipodia-dependent depletion led to prolonged union and impaired migration. Notably, this capacity seems much more mineralization. This finding is concurrent with the in efficient during cerebrovascular regeneration than in vitro experiment indicating that the removal of other tissues. A previous study provided evidence macrophages diminished osteoblast mineralization that the existence of neutrophils retarded wound (Chang et al., 2008). This decreased mineralization closure in mice (Dovi et al., 2003), possibly is probably associated with the lack of osteoblasts explaining the magnificent capacity of the macro- originated from macrophage-enhanced osteoblastic phages mentioned above because neutrophils differentiation (Vi et al., 2015). Claudia et al. have cannot pass the blood-brain barrier (BBB). proven that M2 macrophage enhancement driven by IL-4 and IL-13 improved bone remodeling (Schlundt When studying the functions of distinct sub- et al., 2015). The M1 macrophage expresses high populations of monocytes/macrophages (MOs/MPs) levels of pro-inflammatory cytokines and reactive in the subacute stages of brain infarction, Gliem and

!42 Macrophages and Tissue Regeneration Zhang et al. his colleagues detected co-localization of TGF-β1 activated B cells (NF-κB), and hypoxia-inducible and CD68+ MOs/MPs in the infarct border zone. In factors (HIF) (Sica et al., 2012; Zhou et al., 2014). addition, disruption of infarction repair, down- This balance of the M1/M2 transition is tightly regulation of the TGF-β1 signaling activation associated with physiological and pathological indicator, and phosphorylation of Smad2 were activities. Emerging evidence has proved that M1/ observed in MO/MP-depleted mice. By injecting M2 macrophages exert different even opposite TGF-β1, the deficient mice displayed decreased functions in a stage-dependent manner. Specifically, secondary infarct bleeding and showed preferable M1 type mainly initiates proinflammatory response neurovascular integrity maintenance, suggesting a while M2 type reverses this phenomenon (Gordon critical role of TGF-β1 signaling in stabilizing the et al., 2010; Sica et al., 2012). However, studies neurovascular unit and lesion remodeling (Gliem et have shown that macrophages have negative al., 2012). effects in tissue regeneration. Phenotypes lacking macrophage fractalkine receptor CX3CR1, exhibiting Similar TGF-β1 secretion in macrophages was inefficient phagocytosis and abnormal cytokine found in the injury phase of CCl4-induced liver secretion, has therapeutic actions in arthrosclerosis fibrosis/cirrhosis models. It regulated the deposition (Lesnik et al., 2003), acute spinal cord injury of matrix and supported scar-forming cells, known (Donnelly et al., 2011; Freria et al., 2017) and acute as activated hepatic stellate cells (Duffield et al., colitis (Kostadinova et al., 2010). However, Zhao et 2005). Nevertheless, this TGF-β1 expression was al. (Zhao et al., 2016) and Ishida et al. (Ishida et al., attenuated during the repair phase, and macro- 2008) found that CX3CR1 deficiency mice showed phages assisted in the degradation and absorbency delayed repair of acute skeletal muscle injury. These of redundant matrix components. This finding findings provide another vision to explore the dual provides solid evidence that two phenotypes of function of macrophages in different tissue/organ/ macrophages were independently responsible for species during regeneration process. Thus far, the either the injury or repair phase. field of regeneration is still under study, and investigations to date have not been set forth for the Conclusion and perspective identification of the precise mechanisms underlying Amputation and tissue repair have always been the the repair processes. The advance of genetic hotspot of regenerative medicine. Considering well- modification technique and transcriptome analysis differentiated human cells, human limb regeneration provide new avenues for future research of is often relatively difficult regarding certain tissues macrophages. To sum up, the outstanding roles of and organs, or the ability to regenerate may be lost. macrophage in tissue regeneration may offer an Unlike humans, lower animals such as zebrafish, elaborate picture of tissue injury and regeneration salamanders, etc. have a strong ability to between robust regenerative organisms and less regenerate by repairing and remodeling the limbs regenerative mammals. This might provide a new and large areas of defective tissues. Therefore, therapeutic target that can be manipulated for scientists establish systems in model animals to mammalian tissue/organ regeneration. explore the regeneration mechanism. A wealth of experimental evidence has demonstrated that References macrophages have an irreplaceable role in the Arnold, L., Henry, A., Poron, F., Babaamer, Y., regeneration process. They not only infiltrate the Rooijen, N.V., Plonquet, A., Gherardi, R.K. and damaged targets at the time of body injury and stop Chazaud, B. (2007). Inflammatory monocytes the continued invasion of pathogens but also recruited after skeletal muscle injury switch into coordinate in all post-tissue repair processes and antiinflammatory macrophages to support promote the regeneration of the injured site by myogenesis. Journal of Experimental Medicine switching phenotypes to secrete growth factors and 204, 1057-1069. regulate signaling pathways. Relatively, functional Bergh, A., Damber, J.-E. and Van Rooijen, N. and phenotypical switch of macrophage is controlled (1993). Liposome-mediated macrophage by crosstalk of signaling pathways, such as C-Jun depletion: an experimental approach to study the N-terminal kinase (JNK), PI3K/proterin kinase B role of testicular macrophages in the rat. Journal (PKB), Notch, Janus kinase (JAK)/signal transducer of endocrinology 136, 407-NP. and activator of transcription (STAT), peroxisome Biewenga, J., van der Ende, M.B., Krist, L.F., Borst, proliferator-activated receptor (PPAR), Krüppel-like A., Ghufron, M. and van Rooijen, N. (1995). factor (KLF), interferon regulatory factor (IRF), Macrophage depletion in the rat after nuclear factor kappa-light-chain-enhancer of intraperitoneal administration of liposome-

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