Susceptibility of Rat Steatotic Liver to Ischemia-Reperfusion Is Treatable With Liver-Selective Matrix Metalloproteinase Inhibition.

BACKGROUND AND AIMS: This study examined whether enhanced susceptibility of steatotic liver to ischemia-reperfusion (I/R) injury is due to impaired recruitment of bone marrow (BM) progenitors of liver sinusoidal endothelial cells (LSECs, also called sinusoidal endothelial cell progenitor cells [sprocs]) with diminished repair of injured LSECs and whether restoring signaling to recruit BM sprocs reduces I/R injury. APPROACH AND RESULTS: Hepatic vessels were clamped for 1 hour in rats fed a high-fat, high-fructose (HFHF) diet for 5, 10, or 15 weeks. Matrix metalloproteinase 9 (MMP-9) antisense oligonucleotides (ASO) or an MMP inhibitor were used to induce liver-selective MMP-9 inhibition. HFHF rats had mild, moderate, and severe steatosis, respectively, at 5, 10, and 15 weeks. I/R injury was enhanced in HFHF rats; this was accompanied by complete absence of hepatic vascular endothelial growth factor (VEGF)-stromal cell-derived factor 1 (sdf1) signaling, leading to lack of BM sproc recruitment. Liver-selective MMP-9 inhibition to protect against proteolytic cleavage of hepatic VEGF using either MMP-9 ASO or intraportal MMP inhibitor in 5-week and 10-week HFHF rats enhanced hepatic VEGF-sdf1 signaling, increased BM sproc recruitment, and reduced alanine aminotransferase (ALT) by 92% and 77% at 5 weeks and by 80% and 64% at 10 weeks of the HFHF diet, respectively. After I/R injury in 15-week HFHF rats, the MMP inhibitor reduced active MMP-9 expression by 97%, ameliorated histologic evidence of injury, and reduced ALT by 58%, which is comparable to control rats sustaining I/R injury. Rescue therapy with intraportal MMP inhibitor, given after ischemia, in the 5-week HFHF rat reduced ALT by 71% and reduced necrosis. CONCLUSIONS: Lack of signaling to recruit BM sprocs that repair injured LSECs renders steatotic liver more susceptible to I/R injury. Liver-selective MMP-9 inhibition enhances VEGF-sdf1 signaling and recruitment of BM sprocs, which markedly protects against I/R injury, even in severely steatotic rats.

Liver Complications Following Treatment of Hematologic Malignancy With Anti-CD22-Calicheamicin (Inotuzumab Ozogamicin).

Treatment of hematological malignancy with antibody-drug conjugates (ADCs) may cause liver injury. ADCs deliver a toxic moiety into antigen-expressing tumor cells, but may also injure hepatic sinusoids (sinusoidal obstruction syndrome; SOS). We studied patients who received an anti-CD22/calicheamicin conjugate (inotuzumab ozogamicin; InO) to gain insight into mechanisms of sinusoidal injury, given that there are no CD22+ cells in the normal liver, but nonspecific uptake of ADCs by liver sinusoidal endothelial cells (LSECs). Six hundred thirty-eight patients (307 with acute lymphocytic leukemia [ALL], 311 with non-Hodgkin's lymphoma [NHL]) were randomized to either InO or standard chemotherapy (controls). While blinded to treatment assignment, we reviewed all cases with hepatobiliary complications to adjudicate the causes. Frequency of SOS among patients who received InO was 5 of 328 (1.5%), compared to no cases among 310 control patients. Drug-induced liver injury (DILI) developed in 26 (7.9%) InO recipients and 3 (1%) controls. Intrahepatic cholestasis (IHC) was observed in 4.9% of InO recipients and in 5.5% of controls. Subsequent to the randomization study, 113 patients with ALL underwent allogeneic hematopoietic cell transplantation (HCT); frequency of SOS in those previously exposed to InO was 21 of 79 (27%) versus 3 of 34 (9%) in controls. An exploratory multivariate model identified a past history of liver disease and thrombocytopenia before conditioning therapy as dominant risk factors for SOS after transplant. Conclusion: Frequencies of SOS and DILI after inotuzumab ozogamicin treatment were 1.5% and 7.9%, respectively, compared to none and 1% among controls who received standard chemotherapy. These data suggest that ADCs that do not target antigens present in the normal liver have a relatively low frequency of SOS, but a relatively high frequency of DILI.

Incomplete Differentiation of Engrafted Bone Marrow Endothelial Progenitor Cells Initiates Hepatic Fibrosis in the Rat.

Normal liver sinusoidal endothelial cells (LSECs) promote quiescence of hepatic stellate cells (HSCs). Prior to fibrosis, LSECs undergo capillarization, which is permissive for HSC activation, the proximate event in hepatic fibrosis. The aims of this study were to elucidate the nature of and mechanisms leading to capillarization and to determine how LSECs promote HSC quiescence and why "capillarized LSECs" lose control of HSC activation. The contribution of bone marrow (BM) endothelial progenitor cells to capillarization was identified using rats transplanted with transgenic enhanced green fluorescent protein-positive BM. Shotgun proteomics and informatics were used to identify the LSEC mediator that maintains HSC quiescence. The study shows that capillarization is due to repair of injured LSECs by BM endothelial progenitors that engraft but fail to fully mature. Lack of maturation of BM-derived LSECs is due to cell autonomous pathways that inhibit the nitric oxide pathway. We identify heparin binding epidermal growth factor-like growth factor (HB-EGF) as the signal that maintains HSC quiescence and show that immature LSECs are unable to shed HB-EGF from the cytosolic membrane. Conclusion: Chronic liver injury can recruit BM progenitors of LSECs that engraft and fail to fully differentiate, which creates an environment that is permissive for hepatic fibrosis; elucidation of these early events in the fibrotic process will provide targets for treatment of hepatic fibrosis.

Liver-Selective MMP-9 Inhibition in the Rat Eliminates Ischemia-Reperfusion Injury and Accelerates Liver Regeneration.

Recruitment of liver sinusoidal endothelial cell progenitor cells (sprocs) from the bone marrow by vascular endothelial growth factor-stromal cell-derived factor-1 (VEGF-sdf-1) signaling promotes recovery from injury and drives liver regeneration. Matrix metalloproteinases (MMPs) can proteolytically cleave VEGF, which might inhibit progenitor cell recruitment, but systemic matrix metalloproteinase inhibition might prevent efflux of progenitors from the bone marrow. The hypothesis for this study was that liver-selective MMP-9 inhibition would protect the hepatic VEGF-sdf-1 signaling pathway, enhance bone marrow sproc recruitment, and thereby ameliorate liver injury and accelerate liver regeneration, whereas systemic MMP inhibition would impair bone marrow sproc mobilization and therefore have less benefit or be detrimental. We found that liver-selective MMP-9 inhibition accelerated liver regeneration after partial hepatectomy by 40%, whereas systemic MMP inhibition impaired liver regeneration. Liver-selective MMP-9 inhibition largely abolished warm ischemia-reperfusion injury. In the extended hepatectomy model, liver-selective MMP-9 inhibition restored liver sinusoidal endothelial cell integrity, enhanced liver regeneration, and reduced ascites. Liver-selective MMP-9 inhibition markedly increased recruitment and engraftment of bone marrow sprocs, whereas systemic MMP inhibition impaired mobilization of bone marrow sprocs and their hepatic engraftment. Hepatic MMP-9 proteolytically cleaved VEGF after partial hepatectomy. Liver-selective MMP-9 inhibition prevented VEGF cleavage and doubled protein expression of VEGF and its downstream signaling partner sdf-1. In contrast, systemic MMP inhibition enhanced recruitment and engraftment of infused allogeneic progenitors. Conclusion: Liver-selective MMP inhibition prevents proteolytic cleavage of hepatic VEGF, which enhances recruitment and engraftment of bone marrow sprocs after liver injury. This ameliorates injury and accelerates liver regeneration. Liver-selective MMP-9 inhibition may be a therapeutic tool for liver injury that damages the vasculature, whereas systemic MMP inhibition can enhance the benefit of stem cell therapy with endothelial progenitor cells.

Liver Sinusoidal Endothelial Cell: An Update.

This update focuses on two main topics. First, recent developments in our understanding of liver sinusoidal endothelial cell (LSEC) function will be reviewed, specifically elimination of blood-borne waste, immunological function of LSECs, interaction of LSECs with liver metastases, LSECs and liver regeneration, and LSECs and hepatic fibrosis. Second, given the current emphasis on rigor and transparency in biomedical research, the update discusses the need for standardization of methods to demonstrate identity and purity of isolated LSECs, pitfalls in methods that might lead to a selection bias in the types of LSECs isolated, and questions about long-term culture of LSECs. Various surface markers used for immunomagnetic selection are reviewed.

VEGF-sdf1 recruitment of CXCR7+ bone marrow progenitors of liver sinusoidal endothelial cells promotes rat liver regeneration.

In liver injury, recruitment of bone marrow (BM) progenitors of liver sinusoidal endothelial cells (sprocs) is necessary for normal liver regeneration. Hepatic vascular endothelial growth factor (VEGF) is a central regulator of the recruitment process. We examine whether stromal cell-derived factor 1 [sdf1, or CXC ligand 12 (CXCL12)] acts downstream from VEGF to mediate recruitment of BM sprocs, what the sdf1 receptor type [CXC receptor (CXCR)-4 or CXCR7] is on sprocs, and whether sdf1 signaling is required for normal liver regeneration. Studies were performed in the rat partial hepatectomy model. Tracking studies of BM sprocs were performed in wild-type Lewis rats that had undergone BM transplantation from transgenic enhanced green fluorescent protein-positive Lewis rats. Knockdown studies were performed using antisense oligonucleotides (ASOs). Expression of sdf1 doubles in liver and liver sinusoidal endothelial cells (LSECs) after partial hepatectomy. Upregulation of sdf1 expression increases proliferation of sprocs in the BM, mobilization of CXCR7(+) BM sprocs to the circulation, and engraftment of CXCR7(+) BM sprocs in the liver and promotes liver regeneration. Knockdown of hepatic VEGF with ASOs decreases hepatic sdf1 expression and plasma sdf1 levels. When the effect of VEGF knockdown on sdf1 is offset by infusion of sdf1, VEGF knockdown-induced impairment of BM sproc recruitment after partial hepatectomy is completely attenuated and liver regeneration is normalized. These data demonstrate that the VEGF-sdf1 pathway regulates recruitment of CXCR7(+) BM sprocs to the hepatic sinusoid after partial hepatectomy and is required for normal liver regeneration.

Liver sinusoidal endothelial cells in hepatic fibrosis.

Capillarization, lack of liver sinusoidal endothelial cell (LSEC) fenestration, and formation of an organized basement membrane not only precedes fibrosis, but is also permissive for hepatic stellate cell activation and fibrosis. Thus, dysregulation of the LSEC phenotype is a critical step in the fibrotic process. Both a vascular endothelial growth factor (VEGF)-stimulated, nitric oxide (NO)-independent pathway and a VEGF-stimulated NO-dependent pathway are necessary to maintain the differentiated LSEC phenotype. The NO-dependent pathway is impaired in capillarization and activation of this pathway downstream from NO restores LSEC differentiation in vivo. Restoration of LSEC differentiation in vivo promotes HSC quiescence, enhances regression of fibrosis, and prevents progression of cirrhosis.

Hepatic vascular endothelial growth factor regulates recruitment of rat liver sinusoidal endothelial cell progenitor cells.

BACKGROUND & AIMS: After liver injury, bone marrow-derived liver sinusoidal endothelial cell progenitor cells (BM SPCs) repopulate the sinusoid as liver sinusoidal endothelial cells (LSECs). After partial hepatectomy, BM SPCs provide hepatocyte growth factor, promote hepatocyte proliferation, and are necessary for normal liver regeneration. We examined how hepatic vascular endothelial growth factor (VEGF) regulates recruitment of BM SPCs and their effects on liver injury. METHODS: Rats were given injections of dimethylnitrosamine to induce liver injury, which was assessed by histology and transaminase assays. Recruitment of SPCs was analyzed by examining BM SPC proliferation, mobilization to the circulation, engraftment in liver, and development of fenestration (differentiation). RESULTS: Dimethylnitrosamine caused extensive denudation of LSECs at 24 hours, followed by centrilobular hemorrhagic necrosis at 48 hours. Proliferation of BM SPCs, the number of SPCs in the bone marrow, and mobilization of BM SPCs to the circulation increased 2- to 4-fold by 24 hours after injection of dimethylnitrosamine; within 5 days, 40% of all LSECs came from engrafted BM SPCs. Allogeneic resident SPCs, infused 24 hours after injection of dimethylnitrosamine, repopulated the sinusoid as LSECs and reduced liver injury. Expression of hepatic VEGF messenger RNA and protein increased 5-fold by 24 hours after dimethylnitrosamine injection. Knockdown of hepatic VEGF with antisense oligonucleotides completely prevented dimethylnitrosamine-induced proliferation of BM SPCs and their mobilization to the circulation, reduced their engraftment by 46%, completely prevented formation of fenestration after engraftment as LSECs, and exacerbated dimethylnitrosamine injury. CONCLUSIONS: BM SPC recruitment is a repair response to dimethylnitrosamine liver injury in rats. Hepatic VEGF regulates recruitment of BM SPCs to liver and reduces this form of liver injury.

Role of differentiation of liver sinusoidal endothelial cells in progression and regression of hepatic fibrosis in rats.

BACKGROUND & AIMS: Capillarization, characterized by loss of differentiation of liver sinusoidal endothelial cells (LSECs), precedes the onset of hepatic fibrosis. We investigated whether restoration of LSEC differentiation would normalize crosstalk with activated hepatic stellate cells (HSC) and thereby promote quiescence of HSC and regression of fibrosis. METHODS: Rat LSECs were cultured with inhibitors and/or agonists and examined by scanning electron microscopy for fenestrae in sieve plates. Cirrhosis was induced in rats using thioacetamide, followed by administration of BAY 60-2770, an activator of soluble guanylate cyclase (sGC). Fibrosis was assessed by Sirius red staining; expression of α-smooth muscle actin was measured by immunoblot analysis. RESULTS: Maintenance of LSEC differentiation requires vascular endothelial growth factor-A stimulation of nitric oxide-dependent signaling (via sGC and cyclic guanosine monophosphate) and nitric oxide-independent signaling. In rats with thioacetamide-induced cirrhosis, BAY 60-2770 accelerated the complete reversal of capillarization (restored differentiation of LSECs) without directly affecting activation of HSCs or fibrosis. Restoration of differentiation to LSECs led to quiescence of HSCs and regression of fibrosis in the absence of further exposure to BAY 60-2770. Activation of sGC with BAY 60-2770 prevented progression of cirrhosis, despite continued administration of thioacetamide. CONCLUSIONS: The state of LSEC differentiation plays a pivotal role in HSC activation and the fibrotic process.

15th International Symposium on Cells of the Hepatic Sinusoid, 2010.

This is a meeting report of the presentations given at the 15th International Symposium on Cells of the Hepatic Sinusoid, held in 2010. The areas covered include the contributions of the various liver cell populations to liver disease, molecular and cellular targets involved in steatohepatitis, hepatic fibrosis and cancer and regenerative medicine. In addition to a review of the science presented at the meeting, this report provides references to recent literature on the topics covered at the meeting.

Three-dimensional structured illumination microscopy of liver sinusoidal endothelial cell fenestrations.

Fenestrations are pores in liver sinusoidal endothelial cells that filter substrates and debris between the blood and hepatocytes. Fenestrations have significant roles in aging and the regulation of lipoproteins. However their small size (<200 nm) has prohibited any functional analysis by light microscopy. We employed structured illumination light microscopy to observe fenestrations in isolated rat liver sinusoidal endothelial cells with great clarity and spatial resolution. With this method, the three-dimensional structure of fenestrations (diameter 123+/-24 nm) and sieve plates was elucidated and it was shown that fenestrations occur in areas of abrupt cytoplasmic thinning (165+/-54 nm vs. 292+/-103 nm in non-fenestrated regions, P<0.0001). Sieve plates were not preferentially co-localized with fluorescently labeled F-actin stress fibers and endothelial nitric oxide synthase but appeared to occur in primarily attenuated non-raft regions of the cell membrane. Labyrinthine structures were not seen and all fenestrations were short cylindrical pores. In conclusion, three-dimensional structured illumination microscopy has enabled the unlimited power of fluorescent immunostaining and co-localization to reveal new structural and functional information about fenestrations and sieve plates.

Isolation of periportal, midlobular, and centrilobular rat liver sinusoidal endothelial cells enables study of zonated drug toxicity.

Many liver sinusoidal endothelial cell (LSEC)-dependent processes, including drug-induced liver injury, ischemia-reperfusion injury, acute and chronic rejection, fibrosis, and the HELLP (hemolytic anemia, elevated liver enzymes, low platelet count) syndrome, may have a lobular distribution. Studies of the mechanism of this distribution would benefit from a reliable method to isolate LSEC populations from different regions. We established and verified a simple method to isolate periportal, midlobular, and centrilobular LSEC. Three subpopulations of LSEC were isolated by immunomagnetic separation on the basis of CD45 expression. Flow cytometry showed that 78.2 ± 2.3% of LSEC were CD45 positive and that LSEC could be divided into CD45 bright (28.6 ± 2.7% of total population), dim (49.6 ± 1.0%), and negative populations (21.8 ± 2.3%). Immunohistochemistry confirmed that in vivo expression of CD45 in LSEC had a lobular distribution with enhanced CD45 staining in periportal LSEC. Cell diameter, fenestral diameter, number of fenestrae per sieve plate and per cell, porosity, and lectin uptake were significantly different in the subpopulations, consistent with the literature. Endocytosis of low concentrations of the LSEC-specific substrate, formaldehyde-treated serum albumin, was restricted to CD45 bright and dim LSEC. Acetaminophen was more toxic to the CD45 dim and negative populations than to the CD45 bright population. In conclusion, CD45 is highly expressed in periportal LSEC, low in midlobular LSEC, and negative in centrilobular LSEC, and this provides an easy separation method to isolate LSEC from the three different hepatic regions. The LSEC subpopulations obtained by this method are adequate for functional studies and drug toxicity testing.

Bone marrow progenitor cells repair rat hepatic sinusoidal endothelial cells after liver injury.

BACKGROUND & AIMS: Damage to hepatic sinusoidal endothelial cells (SECs) initiates sinusoidal obstruction syndrome (SOS), which is most commonly a consequence of myeloablative chemoirradiation or ingestion of pyrrolizidine alkaloids such as monocrotaline (Mct). This study examines whether SECs are of bone marrow origin, whether bone marrow repair can be a determinant of severity of liver injury, and whether treatment with progenitor cells is beneficial. METHODS: Mct-treated female rats received infusion of male whole bone marrow or CD133(+) cells at the peak of sinusoidal injury. The Y chromosome was identified in isolated SECs by fluorescent in situ hybridization. Bone marrow suppression was induced by irradiation of both lower extremities with shielding of the abdomen. RESULTS: SECs in uninjured liver have both hematopoietic (CD45, CD33) and endothelial (CD31) markers. After Mct-induced SOS, infusion of bone marrow-derived CD133(+) progenitor cells replaces more than one quarter of SECs. All CD133(+) cells recovered from the SEC fraction after injury are CD45(+). CD133(+)/CD45(+) progenitors also repaired central vein endothelium. Mct suppresses CD133(+)/CD45(+) progenitors in bone marrow by 50% and in the circulation by 97%. Irradiation-induced bone marrow suppression elicited SOS from a subtoxic dose of Mct, whereas infusion of bone marrow during the necrotic phase of SOS nearly eradicates histologic features of SOS. CONCLUSIONS: SECs have both hematopoietic and endothelial markers. Bone marrow-derived CD133(+)/CD45(+) progenitors replace SECs and central vein endothelial cells after injury. Toxicity to bone marrow progenitors impairs repair and contributes to the pathogenesis of SOS, whereas timely infusion of bone marrow has therapeutic benefit.

Prevention of hepatic fibrosis in a murine model of metabolic syndrome with nonalcoholic steatohepatitis.

The endocannabinoid pathway plays an important role in the regulation of appetite and body weight, hepatic lipid metabolism, and fibrosis. Blockade of the endocannabinoid receptor CB1 with SR141716 promotes weight loss, reduces hepatocyte fatty acid synthesis, and is antifibrotic. D-4F, an apolipoprotein A-1 mimetic with antioxidant properties, is currently in clinical trials for the treatment of atherosclerosis. C57BL/6J mice were fed a high-fat diet for 7 months, followed by a 2.5-month treatment with either SR141716 or D-4F. SR141716 markedly improved body weight, liver weight, serum transaminases, insulin resistance, hyperglycemia, hypercholesterolemia, hyperleptinemia, and oxidative stress, accompanied by the significant prevention of fibrosis progression. D-4F improved hypercholesterolemia and hyperleptinemia without improvement in body weight, steatohepatitis, insulin resistance, or oxidative stress, and yet, there was significant prevention of fibrosis. D-4F prevented culture-induced activation of stellate cells in vitro. In summary, C57BL/6J mice given a high-fat diet developed features of metabolic syndrome with nonalcoholic steatohepatitis and fibrosis. Both SR141716 and D-4F prevented progression of fibrosis after onset of steatohepatitis, ie, a situation comparable to a common clinical scenario, with D-4F seeming to have a more general antifibrotic effect. Either compound therefore has the potential to be of clinical benefit.

Sinusoidal endothelial cells prevent rat stellate cell activation and promote reversion to quiescence.

UNLABELLED: Capillarization precedes hepatic fibrosis. We hypothesize that capillarization of sinusoidal endothelial cells (SEC) is permissive for hepatic stellate cell (HSC) activation and therefore permissive for fibrosis. We examined whether freshly isolated SECs prevent activation of HSCs and promote reversion to quiescence, and whether this effect was lost in capillarization. HSCs were cultured alone or co-cultured with differentiated or capillarized SECs. RESULTS: Co-culture with freshly isolated SECs markedly decreased HSC activation after 3 days in culture, but co-culture with capillarized SEC had no effect. Inhibition of nitric oxide (NO) synthesis abolished SEC suppression of HSC activation. Activated HSCs reverted to quiescence when co-cultured with SEC plus vascular endothelial growth factor (VEGF) (that is, with SECs that maintained differentiation), but co-culture with capillarized SECs did not. Reversion of activated HSCs to quiescence in the presence of SECs plus VEGF was abolished by inhibition of NO synthesis. To establish whether there was indeed reversion, activated and quiescent HSCs were counted before and 3 days after adding freshly isolated SECs plus VEGF to activated HSCs, and proliferation was quantified in quiescent HSCs; the stoichiometry demonstrated reversion. CONCLUSION: Differentiated SECs prevent HSC activation and promote reversion of activated HSCs to quiescence through VEGF-stimulated NO production. Capillarized SECs do not promote HSC quiescence, because of loss of VEGF-stimulated NO production.

Hepatic circulatory diseases associated with chronic myeloid disorders.

These liver diseases are diseases of the hepatic circulation. Myeloproliferative disorders are among the most common prothrombotic disorders that lead to Budd-Chiari syndrome and PVT. SOS, previously known as hepatic veno-occlusive disease, is mainly seen in North America and Western Europe as a complication of the conditioning regimen for hematopoietic stem cell transplantation. SOS is caused by damage to SECs, and the initiating circulatory blockage occurs because of the embolism of sinusoidal lining cells. Myeloproliferative disorders are an uncommon cause of NRH, which is believed to be caused by uneven perfusion of the liver at the venous or sinusoidal level. Peliosis hepatis is believed to result from damage to SECs and is seen mainly in immunosuppressed patients, patients with a wasting illness, or patients with a drug toxicity.

Hepatic veno-occlusive disease (sinusoidal obstruction syndrome) after hematopoietic stem cell transplantation.

Hepatic veno-occlusive disease (VOD), increasingly referred to as sinusoidal obstruction syndrome, is a well-recognized complication of hematopoietic stem cell transplantation and contributes to considerable morbidity and mortality. In the Western Hemisphere, VOD, classified as a conditioning-related toxicity, is most commonly caused by stem cell transplantation. VOD has been described after all types of stem cell transplantation, irrespective of the stem cell source, type of conditioning therapy, or underlying disease. Recognition of this disease in the posttransplantation setting remains a challenge in the absence of specific diagnostic features because many other more common conditions can mimic it. Limited therapeutic or preventive strategies are currently available for the management of VOD. In this review, we provide a comprehensive account of the pathophysiology of this disease as we understand it today, risk factors for its development, and the current state of knowledge regarding preventive and therapeutic options.

An amphipathic alpha-helical peptide from apolipoprotein A1 stabilizes protein polymer vesicles.

L4F, an alpha helical peptide inspired by the lipid-binding domain of the ApoA1 protein, has potential applications in the reduction of inflammation involved with cardiovascular disease as well as an antioxidant effect that inhibits liver fibrosis. In addition to its biological activity, amphipathic peptides such as L4F are likely candidates to direct the molecular assembly of peptide nanostructures. Here we describe the stabilization of the amphipathic L4F peptide through fusion to a high molecular weight protein polymer. Comprised of multiple pentameric repeats, elastin-like polypeptides (ELPs) are biodegradable protein polymers inspired from the human gene for tropoelastin. Dynamic light scattering confirmed that the fusion peptide forms nanoparticles with a hydrodynamic radius of approximately 50nm, which is unexpectedly above that observed for the free ELP (~5.1nm). To further investigate their morphology, conventional and cryogenic transmission electron microscopy were used to reveal that they are unilamellar vesicles. On average, these vesicles are 49nm in radius with lamellae 8nm in thickness. To evaluate their therapeutic potential, the L4F nanoparticles were incubated with hepatic stellate cells. Stellate cell activation leads to hepatic fibrosis; furthermore, their activation is suppressed by anti-oxidant activity of ApoA1 mimetic peptides. Consistent with this observation, L4F nanoparticles were found to suppress hepatic stellate cell activation in vitro. To evaluate the in vivo potential for these nanostructures, their plasma pharmacokinetics were evaluated in rats. Despite the assembly of nanostructures, both free L4F and L4F nanoparticles exhibited similar half-lives of approximately 1h in plasma. This is the first study reporting the stabilization of peptide-based vesicles using ApoA1 mimetic peptides fused to a protein polymer; furthermore, this platform for peptide-vesicle assembly may have utility in the design of biodegradable nanostructures.