Suzhen Zhang

Immobilized Heavy Chain-Hyaluronic Acid Polarizes Lipopolysaccharide-activated Macrophages toward M2 Phenotype

Background: HC-HA is a unique anti-inflammatory matrix different from hyaluronic acid (HA). Results: Soluble HC-HA induces apoptosis of inflammatory neutrophils and macrophages, and immobilized HC-HA promotes M2 polarization upon LPS/TLR ligation while both enhancing macrophage phagocytosis. Conclusion: HC-HA exerts its anti-inflammatory action using multiple mechanisms. Significance: HC-HA is the first known matrix component to polarize M2b. Despite the known anti-inflammatory effect of amniotic membrane, its action mechanism remains largely unknown. HC-HA complex (HC-HA) purified from human amniotic membrane consists of high molecular weight hyaluronic acid (HA) covalently linked to the heavy chain (HC) 1 of inter-α-trypsin inhibitor. In this study, we show that soluble HC-HA also contained pentraxin 3 and induced the apoptosis of both formyl-Met-Leu-Phe or LPS-activated neutrophils and LPS-activated macrophages while not affecting the resting cells. This enhanced apoptosis was caused by the inhibition of cell adhesion, spreading, and proliferation caused by HC-HA binding of LPS-activated macrophages and preventing adhesion to the plastic surface. Preferentially, soluble HC-HA promoted phagocytosis of apoptotic neutrophils in resting macrophages, whereas immobilized HC-HA promoted phagocytosis in LPS-activated macrophages. Upon concomitant LPS stimulation, immobilized HC-HA but not HA polarized macrophages toward the M2 phenotype by down-regulating IRF5 protein and preventing its nuclear localization and by down-regulating IL-12, TNF-α, and NO synthase 2. Additionally, IL-10, TGF-β1, peroxisome proliferator-activated receptor γ, LIGHT (TNF superfamily 14), and sphingosine kinase-1 were up-regulated, and such M2 polarization was dependent on TLR ligation. Collectively, these data suggest that HC-HA is a unique matrix component different from HA and uses multiple mechanisms to suppress M1 while promoting M2 phenotype. This anti-inflammatory action of HC-HA is highly desirable to promote wound healing in diseases heightened by unsuccessful transition from M1 to M2 phenotypes.

Constitutive expression of inter-α-inhibitor (IαI) family proteins and tumor necrosis factor-stimulated gene-6 (TSG-6) by human amniotic membrane epithelial and stromal cells supporting formation of the heavy chain-hyaluronan (HC-HA) complex

Background: The heavy chain-hyaluronan (HC-HA) complex from amniotic membrane (AM) has anti-inflammatory, anti-scarring, and anti-angiogenic actions. Results: AM epithelial and stromal cells constitutively expressed IαI and TSG-6 supporting the production of HC-HA. Conclusion: AM is an extrahepatic tissue constitutively producing its own IαI and HC-HA complex. Significance: HC-HA endogenously produced by AM may play an important protective role during fetal development. Recently, we reported HC-HA, a covalent complex formed between heavy chains (HCs) of inter-α-inhibitor (IαI) and hyaluronan (HA) by the catalytic action of tumor necrosis factor (TNF)-stimulated gene-6 (TSG-6), is responsible for human amniotic membrane (AM) anti-inflammatory, anti-scarring, and anti-angiogenic actions. At the present time, the only well characterized source of IαI is serum being produced by the liver. This study showed that AM epithelial and stromal cells and stromal matrix all stained positively for HA, HC 1, 2, and 3, bikunin, and TSG-6. TSG-6 mRNA and protein were constitutively expressed by cultured AM epithelial and stromal cells without being up-regulated by TNF. In serum-free conditions, these cells expressed IαI, leading to the formation of HC-HA complex that contained both HC1 and HC2. In contrast, only HC1 was found in the HC-HA complex purified from AM. Local production of IαI, the HC-TSG-6 intermediate complex, and HC-HA were abolished when cells were treated with siRNA to HC1, HC2, bikunin (all of which impair the biosynthesis of IαI), or TSG-6 but not to HC3. Collectively, these results indicate that AM is another tissue in addition to the liver to constitutively produce IαI and that the HC-HA complex made by this tissue is different from that found at inflammatory sites (e.g. in asthma and arthritis) and in the matrix of the cumulus oocyte complex.

Constitutive Expression of Pentraxin 3 (PTX3) Protein by Human Amniotic Membrane Cells Leads to Formation of the Heavy Chain (HC)-Hyaluronan (HA)-PTX3 Complex

Background: HC-HA from the amniotic membrane (AM) is produced by AM cells. Results: Pentraxin 3 tightly binds to purified AM HC-HA and is constitutively secreted by AM cells, leading to HC-HA-PTX3 complex formation. Conclusion: PTX3 is an integral component of AM HC-HA-PTX3 complexes. Significance: HC-HA-PTX3, produced endogenously by the AM, may play an important protective role during fetal development and can be an active therapeutic agent. Heavy chain (HC)-hyaluronan (HA), a complex formed by the covalent linkage between HC1 from the inter-α-trypsin inhibitor (IαI) and HA, purified from the human amniotic membrane (AM), is responsible for the anti-inflammatory, antiscarring, and antiangiogenic actions of the AM. This HC-HA complex is produced by constitutive expression of TNF-stimulated gene 6 and endogenous production of IαI by AM cells. Pentraxin 3 (PTX3), a prototypic long pentraxin that plays a non-redundant role in innate immunity against selected pathogens, also helps stabilize HC-HA to ensure female fertility. Here we noted strong positive PTX3 staining in the AM epithelium and compact stroma. PTX3 was constitutively expressed and secreted by cultured AM epithelial and stromal cells and, further, greatly up-regulated by TNF and IL-1β. Using an agarose overlay to trap the HA-containing matrix, the HC-HA-PTX3 complex was formed, as analyzed by Western blot analysis, by AM cells but not human skin fibroblasts, despite being cultured in the presence of serum and TNF. However, exogenous PTX3 helps human skin fibroblasts form the HC-HA-PTX3 complex with an agarose overlay. Furthermore, PTX3 can be coimmunoprecipitated with the HC-HA complex from agarose-overlaid AM cell extracts by an anti-human IαI antibody. Such a HC-HA-PTX3 complex can be reconstituted in vitro and exhibit similar effects as those reported for AM HC-HA-PTX3 on polarization of M2 macrophages. The tight binding between PTX3 and AM HC-HA withstands four runs of CsCl ultracentrifugation in the presence of 4 m GnHCl. These results indicate that PTX3 is constitutively expressed and secreted by AM cells as an integral component of the AM HC-HA-PTX3 complex and contributes to the biological function of AM HC-HA-PTX3.

Activation of RhoA-ROCK-BMP signaling reprograms adult human corneal endothelial cells

Activation of RhoA-ROCK-BMP signaling reprograms adult human corneal endothelial cells into neural crest–like progenitors, which effectively form corneal endothelial monolayers that may eliminate the need for corneal transplantation.

TSG-6 Controls Transcription and Activation of Matrix Metalloproteinase 1 in Conjunctivochalasis

PURPOSE To investigate the role of anti-inflammatory TSG-6 in controlling MMP-1 and MMP-3, which have been shown to be upregulated in conjunctivochalasis (CCh). METHODS Immunostaining of TSG-6 was compared between normal and CCh conjunctiva and Tenons capsule. Second cultures of normal and CCh fibroblasts were transfected with or without TSG-6 siRNA and then with or without the addition of TNF-α or IL-1β. Cell lysates and culture media were collected to assess apoptosis with the use of ELISA and the expression of TSG-6, MMP-1, and MMP-3 transcripts and proteins with the use of qRT-PCR and Western blot analysis, respectively. RESULTS TSG-6 expression was constitutive in the in vivo normal conjunctival epithelium. Significantly more TSG-6-positive cells than normal specimens were noted in CCh subconjunctival tissue and Tenons capsule. TSG-6 was constitutively expressed intracellularly by both resting normal and CCh fibroblasts but was secreted extracellularly only by resting CCh fibroblasts. Intracellular and extracellular TSG-6 proteins were markedly upregulated by TNF-α or IL-1β in normal and CCh fibroblasts. Active MMP-1 was found in CCh fibroblasts intracellularly and extracellularly, whereas only proMMP-1 was found intracellularly in normal fibroblasts. Knockdown by TSG-6 siRNA upregulated more MMP-1 than MMP-3 transcripts in normal and CCh fibroblasts. TSG-6 siRNA led to extracellular MMP-1 expression by normal fibroblasts such as CCh fibroblasts. This activation of MMP-1 was further enhanced by IL-1β. Cell apoptosis was higher in CCh fibroblasts and further aggravated by TSG-6 siRNA knockdown. CONCLUSIONS TSG-6 exerts an anti-inflammatory function by counteracting the transcription of MMP-1 and MMP-3 and the activation of MMP-1. Dysfunction of TSG-6 might play a role in the pathogenesis of CCh.

PTX3 Controls Activation of Matrix Metalloproteinase 1 and Apoptosis in Conjunctivochalasis Fibroblasts

PURPOSE Conjunctivochalasis (CCh) is an age-related inflammatory ocular surface disease manifesting redundant, loose conjunctiva folds. The pathogenic role of Pentraxin 3 (PTX3) in controlling upregulation of matrix metalloproteinase 1 (MMP-1) and MMP-3 in CCh remains undefined. METHODS Cytolocation of PTX3 and apoptosis were compared by immunostaining and terminal deoxyribonucleotidyl transferase-mediated FITC-linked dUTP nick-end DNA labeling (TUNEL) assay between normal and CCh specimens containing the conjunctiva and the Tenon. Second to third cultures of normal and CCh fibroblasts were treated with or without Aprotinin, Batimastat, or N-isobutyl-N-(4-methoxyphenylsulfonyl)-glycylhydroxamic acid (NNGH), followed by transfection with or without PTX3 siRNA, and TNF-α or IL-1β. Cell lysates and culture media were collected to assess apoptosis measured by the Cell Death Detection ELISA and expression of PTX3, MMP-1, and MMP-3 transcripts and proteins by quantitative RT-PCR and Western blot, respectively. RESULTS PTX3 immunostaining was negative in normal specimens, but strongly positive in the subconjunctival stroma of CCh specimens. More apoptotic cells were found in CCh samples than in normal specimens. Expression of PTX3 transcripts and protein was not constitutive in resting normal fibroblasts but was in resting CCh fibroblasts and was upregulated by IL-1β in both cell lysates and culture media of both fibroblasts. PTX3 siRNA further upregulated MMP-1 and MMP-3 transcripts in resting normal fibroblasts, but synergistically with IL-1β upregulated the expression of MMP-1 and MMP-3 transcripts only in CCh fibroblasts, with activation of MMP-1 more so than MMP-3. PTX3 siRNA knockdown also promoted cell death characterized by apoptosis and necrosis, and such cell death could be rescued by inhibitors against serine proteinase, MMP1, or MMP3. CONCLUSIONS Perturbation of PTX3 expression might partake in apoptosis and pathogenesis of CCh by upregulating expression of MMP-1 and MMP-3, and activation of MMP-1 and MMP-3.