Hyaluronan synthesis mediates the fibrotic response of keratocytes to transforming growth factor beta

Corneal Opacity: Cell Biological Determinants of the Transition From Transparency to Transient Haze to Scarring Fibrosis, and Resolution, After Injury

Purpose

To highlight the cellular, matrix, and hydration changes associated with opacity that occurs in the corneal stroma after injury.

Methods

Review of the literature.

Results

The regulated transition of keratocytes to corneal fibroblasts and myofibroblasts, and of bone marrow-derived fibrocytes to myofibroblasts, is in large part modulated by transforming growth factor beta (TGFβ) entry into the stroma after injury to the epithelial basement membrane (EBM) and/or Descemet's membrane. The composition, stoichiometry, and organization of the stromal extracellular matrix components and water is altered by corneal fibroblast and myofibroblast production of large amounts of collagen type I and other extracellular matrix components-resulting in varying levels of stromal opacity, depending on the intensity of the healing response. Regeneration of EBM and/or Descemet's membrane, and stromal cell production of non-EBM collagen type IV, reestablishes control of TGFβ entry and activity, and triggers TGFβ-dependent myofibroblast apoptosis. Eventually, corneal fibroblasts also disappear, and repopulating keratocytes reorganize the disordered extracellular matrix to reestablish transparency.

Conclusions

Injuries to the cornea produce varying amounts of corneal opacity depending on the magnitude of cellular and molecular responses to injury. The EBM and Descemet's membrane are key regulators of stromal cellularity through their modulation of TGFβ. After injury to the cornea, depending on the severity of the insult, and possibly genetic factors, trace opacity to severe scarring fibrosis develops. Stromal cellularity, and the functions of different cell types, are the major determinants of the level of the stromal opacity.

Hyaluronan, Transforming Growth Factor β, and Extra Domain A-Fibronectin: A Fibrotic Triad

Significance: Inflammation is a critical aspect of injury repair. Nonresolving inflammation, however, is perpetuated by the local generation of extracellular matrix-derived damage-associated molecular pattern molecules (DAMPs), such as the extra domain A (EDA) isoform of fibronectin and hyaluronic acid (HA) that promote the eventual acquisition of a fibrotic response. DAMPs contribute to the inflammatory environment by engaging Toll-like, integrin, and CD44 receptors while stimulating transforming growth factor (TGF)-β signaling to activate a fibroinflammatory genomic program leading to the development of chronic disease. Recent Advances: Signaling through TLR4, CD44, and the TGF-β pathways impact the amplitude and duration of the innate immune response to endogenous DAMPs synthesized in the context of tissue injury. New evidence indicates that crosstalk among these three networks regulates phase transitions as well as the repertoire of expressed genes in the wound healing program determining, thereby, repair outcomes. Clarifying the molecular mechanisms underlying pathway integration is necessary for the development of novel therapeutics to address the spectrum of fibroproliferative diseases that result from maladaptive tissue repair. Critical Issues: There is an increasing appreciation for the role of DAMPs as causative factors in human fibroinflammatory disease regardless of organ site. Defining the involved intermediates essential for the development of targeted therapies is a daunting effort, however, since various classes of DAMPs activate different direct and indirect signaling pathways. Cooperation between two matrix-derived DAMPs, HA, and the EDA isoform of fibronectin, is discussed in this review as is their synergy with the TGF-β network. This information may identify nodes of signal intersection amenable to therapeutic intervention. Future Directions: Clarifying mechanisms underlying the DAMP/growth factor signaling nexus may provide opportunities to engineer the fibroinflammatory response to injury and, thereby, wound healing outcomes. The identification of shared and unique DAMP/growth factor-activated pathways is critical to the design of optimized tissue repair therapies while preserving the host response to bacterial pathogens.

TGF-β1 upregulates the expression of hyaluronan synthase 2 and hyaluronan synthesis in culture models of equine articular chondrocytes

We investigated the effect of transforming growth factor beta 1 (TGF-β1) on equine hyaluronan synthase 2 (HAS2) gene expression and hyaluronan (HA) synthesis in culture models of articular chondrocytes. Equine chondrocytes were treated with TGF-β1 at different concentrations and times in monolayer cultures. In three-dimensional cultures, chondrocyte-seeded gelatin scaffolds were cultured in chondrogenic media containing 10 ng/mL of TGF-β1. The amounts of HA in conditioned media and in scaffolds were determined by enzyme-linked immunosorbent assays. HAS2 mRNA expression was analyzed by semi-quantitative reverse transcription polymerase chain reaction. The uronic acid content and DNA content of the scaffolds were measured by using colorimetric and Hoechst 33258 assays, respectively. Cell proliferation was evaluated by using the alamarBlue assay. Scanning electron microscopy (SEM), histology, and immunohistochemistry were used for microscopic analysis of the samples. The upregulation of HAS2 mRNA levels by TGF-β1 stimulation was dose and time dependent. TGF-β1 was shown to enhance HA and uronic acid content in the scaffolds. Cell proliferation and DNA content were significantly lower in TGF-β1 treatments. SEM and histological results revealed the formation of a cartilaginous-like extracellular matrix in the TGF-β1-treated scaffolds. Together, our results suggest that TGF-β1 has a stimulatory effect on equine chondrocytes, enhancing HA synthesis and promoting cartilage matrix generation.

Compressed Collagen Enhances Stem Cell Therapy for Corneal Scarring

Stem cells from human corneal stroma (CSSC) suppress corneal stromal scarring in a mouse wound‐healing model and promote regeneration of native transparent tissue (PMID:25504883). This study investigated efficacy of compressed collagen gel (CCG) as a vehicle to deliver CSSC for corneal therapy. CSSC isolated from limbal stroma of human donor corneas were embedded in soluble rat‐tendon collagen, gelled at 37°C, and partially dehydrated to a thickness of 100 µm by passive absorption. The CCG disks were dimensionally stable, easy to handle, and could be adhered securely to de‐epithelialized mouse cornea with fibrin‐based adhesive. CSSC in CCG maintained >80% viability for >1 week in culture media and could be cryopreserved in 20% fetal bovine serum‐10%DMSO in liquid nitrogen. CCG containing as few as 500 CSSC effectively prevented visible scarring and suppressed expression of fibrotic Col3a1 mRNA. CSSC in CCG were more effective at blocking scarring on a per‐cell basis than CSSC delivered directly in a fibrin gel as previously described. Collagen‐embedded cells retained the ability to suppress corneal scarring after conventional cryopreservation. This study demonstrates use of a common biomaterial that can facilitate storage and handling of stem cells in a manner that may provide off‐the‐shelf delivery of stem cells as a therapy for corneal scarring. stemcellstranslationalmedicine2018;7:487–494

[Influence of TGF-β cytokine and a number of other biochemical factors on regenerative process]

Scarring is one of the main causes of surgical failure in a number of eye diseases, dacryologic conditions in particular. The process of wound healing, including postoperative wound healing, goes through several stages mediated by various biochemical factors, such as growth factors and pro- and anti-inflammatory cytokines. The balance between the latter directly influences the wound healing. However, current data on the effect of these factors on postoperative outcomes are few and contradictory. Thus, in dacryology as well as in other areas of ophthalmology, the role of cytokines and growth factors in healing of surgical wounds is being intensively researched.

Inhibition of NF-kappaB with Dehydroxymethylepoxyquinomicin modifies the function of human peritoneal mesothelial cells

Peritoneal mesothelial cells exposed to bioincompatible dialysis fluids contribute to damage of the peritoneum during chronic dialysis. Inflammatory response triggered in the mesothelium leading to neovascularization and fibrosis plays an important role in that process. We studied the effects of Dehydroxymethyepoxyquinmicin (DHMEQ)-an NF-κB inhibitor on function of human peritoneal mesothelial cells (HPMC) in in vitro culture. DHMEQ studied in concentrations of 1-10 µg/ml was not toxic to HPMC. Synthesis of IL-6, MCP-1 and hyaluronan in unstimulated and stimulated with interleukin-1 (100 pg/ml) HPMC was inhibited in the presence of DHMEQ and the effect was proportional to the dose of the drug. DHMEQ (10 µg/ml) reduced in unstimulated HPMC synthesis of IL-6 (-55%), MCP-1 (-58%) and hyaluronan (-41%). Respective values for stimulated HMPC were: -63% for IL-6, -57% for MCP-1 and -67% for hyaluronan. The observed effects were due to the suppression of the expression of genes responsible for the synthesis of these molecules. DHMEQ modified the effects of the effluent dialysates from CAPD patients on the function of HMPC. Dialysate induced accelerated growth of these cells, and synthesis of collagen was inhibited in the presence of DHMEQ 10 µg/ml, by 69% and 40%, respectively. The results of our study show that DHMEQ effectively reduces inflammatory response in HMPC and prevents excessive dialysate induced proliferation and collagen synthesis in these cells. All of these effects may be beneficial during chronic peritoneal dialysis and prevents progressive dialysis-induced damage to the peritoneum.

Provisional matrix: A role for versican and hyaluronan

Hyaluronan and versican are extracellular matrix (ECM) components that are enriched in the provisional matrices that form during the early stages of development and disease. These two molecules interact to create pericellular "coats" and "open space" that facilitate cell sorting, proliferation, migration, and survival. Such complexes also impact the recruitment of leukocytes during development and in the early stages of disease. Once thought to be inert components of the ECM that help hold cells together, it is now quite clear that they play important roles in controlling cell phenotype, shaping tissue response to injury and maintaining tissue homeostasis. Conversion of hyaluronan-/versican-enriched provisional matrix to collagen-rich matrix is a "hallmark" of tissue fibrosis. Targeting the hyaluronan and versican content of provisional matrices in a variety of diseases including, cardiovascular disease and cancer, is becoming an attractive strategy for intervention.

The Effect of Hyaluronic Acid Application on the Perisilicon Capsule Structure

BACKGROUND

Silicon implants constitute a major part of plastic surgery practice. Although materials with high biocompatibility have been used around the implants, capsule formation still develops and progressive nature of this process results in capsule contraction. The aim of this study is to evaluate the effects of hyaluronic acid injected around the silicon block on the capsule structure.

METHODS

Twenty Wistar albino rats were used in the study. Rats were divided into two main groups (group 1 and group 2) and two subgroups. Rats in group 1 were sacrificed in week 4 and rats in group 2 were sacrificed in week 8. A subcutaneous pouch was created in the dorsum of the rats and a silicon block was placed into the pouch in groups 1A and 2A. 0.2 ml of hyaluronic acid was injected around the silicon block in group 1B and group 2B. Rats were sacrificed and capsule structure and thickness were analyzed following macroscopic evaluation. Concentrations of transforming growth factor-β1 (TGF-β1) and heat shock protein-47 (HSP-47) were evaluated immunohistochemically, and statistical comparisons were made.

RESULT

Capsule structure consisted of three layers in all the groups. A more intense collagen structure was observed in the middle layer. The capsule was thinnest in group 1A and thickest in group 2B; the difference between the groups was statistically significant. TGF-β1 was most intense in group 2B and it was correlated with the amount of collagen. Involvement of HSP-47 was observed mainly in collagen and also in fibroblasts and vascular structures, and its concentration was found to be lower in groups 2A and 2B.

CONCLUSION

Exogenously added cross-linked hyaluronic acid increased the capsular thickness and may increase the risk of developing capsular contracture around silicone implants.

LEVEL OF EVIDENCE II

Evidence was obtained from the well-designed controlled trials without randomization.

Putting on the brakes: Bacterial impediment of wound healing

The epithelium provides a crucial barrier to infection, and its integrity requires efficient wound healing. Bacterial cells and secretomes from a subset of tested species of bacteria inhibited human and porcine corneal epithelial cell migration in vitro and ex vivo. Secretomes from 95% of Serratia marcescens, 71% of Pseudomonas aeruginosa, 29% of Staphylococcus aureus strains, and other bacterial species inhibited epithelial cell migration. Migration of human foreskin fibroblasts was also inhibited by S. marcescens secretomes indicating that the effect is not cornea specific. Transposon mutagenesis implicated lipopolysaccharide (LPS) core biosynthetic genes as being required to inhibit corneal epithelial cell migration. LPS depletion of S. marcescens secretomes with polymyxin B agarose rendered secretomes unable to inhibit epithelial cell migration. Purified LPS from S. marcescens, but not from Escherichia coli or S. marcescens strains with mutations in the waaG and waaC genes, inhibited epithelial cell migration in vitro and wound healing ex vivo. Together these data suggest that S. marcescens LPS is sufficient for inhibition of epithelial wound healing. This study presents a novel host-pathogen interaction with implications for infections where bacteria impact wound healing and provides evidence that secreted LPS is a key factor in the inhibitory mechanism.

Myofibroblasts

Myofibroblasts are activated in response to tissue injury with the primary task to repair lost or damaged extracellular matrix. Enhanced collagen secretion and subsequent contraction - scarring - are part of the normal wound healing response and crucial to restore tissue integrity. Due to myofibroblasts ability to repair but not regenerate, accumulation of scar tissue is always associated with reduced organ performance. This is a fair price to pay by the body for not falling apart. Whereas myofibroblasts typically vanish after successful repair, dysregulation of the normal repair process can lead to persistent myofibroblast activation, for instance by chronic inflammation or mechanical stress in the tissue. Excessive repair leads to the accumulation of stiff collagenous ECM contractures - fibrosis - with dramatic consequences for organ function. The clinical need to terminate detrimental myofibroblast activities has stimulated researchers to answer a number of essential questions: where do myofibroblasts come from, what are the factors leading to their activation, how do we discriminate myofibroblasts from other cells, what is the molecular basis for their contractile activity, and how can we stop or at least control them? This article reviews the current state of the myofibroblast literature by emphasizing their role in ocular repair and fibrosis. It appears that although the eye is quite an extraordinary organ, ocular myofibroblasts behave or misbehave just like their siblings in other organs.

Perturbed mechanotransduction by endothelial surface glycocalyx modification greatly impairs the arteriogenic process

The mechanisms that trigger initiation of arteriogenesis in response to pathogenic obstruction of arterial flow are not fully understood. Our objective is to determine whether glycocalyx mediated mechanotransduction of fluid shear stress to the endothelial layer is an essential first step in inducing arteriogenesis. Mice were implanted with an osmotic minipump containing saline or hyaluronan synthase inhibitor 4-methylesculetin (4ME) 2 wk before femoral artery ligation. 4ME was effective in modifying the endothelial glycocalyx as measured by dextran exclusion and perfused boundary region changes. Glycocalyx modification resulted in a 52% (P = 0.002) reduction in perfusion restoration through the 21-day follow-up [area under the curve, 4.9 ± 1.1 (n = 11) vs. 10.2 ± 3.2 (n = 10), 4ME vs. control (Ctrl)]. Upon femoral artery ligation, no change in collateral vessel diameter in 4ME treated mice (49.8 ± 26.3 vs. 47.1 ± 14.0 μm, ligated vs unligated) was observed (Ctrl, 88.5 ± 18.8 vs. 35.1 ± 3.0 μm, ligated vs unligated, P < 0.05). This impaired arteriogenic process was accompanied by lack of local induction of both endothelial and smooth muscle cell activation (Ki67, endothelial nitric oxide synthase, and ICAM-1), as well as a failure to recruit CD11b-positive cells in 4ME-treated collateral vessels (0.012 ± 0.003 vs. 0.010 ± 0.003 cells/μm vessel perimeter, ligated vs. unligated), whereas in Ctrls, the number of CD11b cells was increased (0.024 ± 0.002 vs. 0.010 ± 0.004 cells/μm vessel perimeter, P < 0.05). Modification of the glycocalyx by inhibition of hyaluronan synthesis renders the endothelium unresponsive to altered hemodynamic conditions resulting from femoral artery ligation, which results in a hampered restoration of distal perfusion.

Glycosaminoglycans in the human cornea: age-related changes

AIM

To investigate possible age-related changes in glycosaminoglycans (GAGs) in the human cornea. The substances today called GAGs were previously referred to as mucopolysaccharides.

METHODS

Samples of human cornea were taken from 12 younger (age 21 ± 1.2) and 12 older (age 72 ± 1.6) male subjects. Samples were weighed, homogenized, and used for biochemical and molecular analyses. All the quantitative results were statistically analyzed.

RESULTS

The human cornea appears to undergo age-related changes, as evidenced by our biochemical and molecular results. The total GAG and hyaluronic acid counts were significantly higher in the younger subjects than in the older subjects. The sulfated heavy GAGs, such as chondroitin, dermatan, keratan, and heparan sulfate, were lower in the younger subjects than in the older subjects.

DISCUSSION

GAGs of the human cornea undergo numerous age-related changes. Their quantity is significantly altered in the elderly in comparison with younger subjects. GAGs play an important role in age-related diseases of the human cornea.

More than just a filler - the role of hyaluronan for skin homeostasis

In recent years, hyaluronan (HA) has become an increasingly attractive substance as a non-immunogenic filler and scaffolding material in cosmetic dermatology. Despite its wide use for skin augmentation and rejuvenation, relatively little is known about the molecular structures and interacting proteins of HA in normal and diseased skin. However, a comprehensive understanding of cutaneous HA homeostasis is required for future the development of HA-based applications for skin regeneration. This review provides an update on HA-based structures, expression, metabolism and its regulation, function and pharmacological targeting of HA in skin.

Inhibition of hyaluronan synthesis protects against central nervous system (CNS) autoimmunity and increases CXCL12 expression in the inflamed CNS

Hyaluronan (HA) may have proinflammatory roles in the context of CNS autoimmunity. It accumulates in demyelinated multiple sclerosis (MS) lesions, promotes antigen presentation, and enhances T-cell activation and proliferation. HA facilitates lymphocyte binding to vessels and CNS infiltration at the CNS vascular endothelium. Furthermore, HA signals through Toll-like receptors 2 and 4 to stimulate inflammatory gene expression. We assessed the role of HA in experimental autoimmune encephalomyelitis (EAE), an animal model of MS by administration of 4-methylumbelliferone (4MU), a well established inhibitor of HA synthesis. 4MU decreased hyaluronan synthesis in vitro and in vivo. It was protective in active EAE of C57Bl/6 mice, decreased spinal inflammatory infiltrates and spinal infiltration of Th1 cells, and increased differentiation of regulatory T-cells. In adoptive transfer EAE, feeding of 4MU to donor mice significantly decreased the encephalitogenicity of lymph node cells. The transfer of proteolipid protein (PLP)-stimulated lymph node cells to 4MU-fed mice resulted in a delayed EAE onset and delayed spinal T-cell infiltration. Expression of CXCL12, an anti-inflammatory chemokine, is reduced in MS patients in CSF cells and in spinal cord tissue during EAE. Hyaluronan suppressed production of CXCL12, whereas 4MU increased spinal CXCL12 in naive animals and during neuroinflammation. Neutralization of CXCR4, the most prominent receptor of CXCL12, by administration of AMD3100 diminished the protective impact of 4MU in adoptive transfer EAE. In conclusion, hyaluronan exacerbates CNS autoimmunity, enhances encephalitogenic T-cell responses, and suppresses the protective chemokine CXCL12 in CNS tissue. Inhibition of hyaluronan synthesis with 4MU protects against an animal model of MS and may represent an important therapeutic option in MS and other neuroinflammatory diseases.

Modulating the behaviors of mesenchymal stem cells via the combination of high-frequency vibratory stimulations and fibrous scaffolds

We are interested in the in vitro engineering of artificial vocal fold tissues via the strategic combination of multipotent mesenchymal stem cells (MSCs), physiologically relevant mechanical stimulations, and biomimetic artificial matrices. We have constructed a vocal fold bioreactor that is capable of imposing vibratory stimulations on the cultured cells at human phonation frequencies. Separately, fibrous poly (ɛ-caprolactone) (PCL) scaffolds emulating the ligamentous structure of the vocal fold were prepared by electrospinning, were incorporated in the vocal fold bioreactor, and were driven into a wave-like motion in an axisymmetrical fashion by the oscillating air. MSC-laden PCL scaffolds were subjected to vibrations at 200 Hz with a normal center displacement of ∼40 μm for a total of 7 days. A continuous (CT) or a 1 h-on-1 h-off (OF) regime with a total dynamic culture time of 12 h per day was applied. The dynamic loading did not cause any physiological trauma to the cells. Immunohistotochemical staining revealed the reinforcement of the actin filament and the enhancement of α5β1 integrin expression under selected dynamic culture conditions. Cellular expression of essential vocal fold extracellular matrix components, such as elastin, hyaluronic acid, and matrix metalloproteinase-1, was significantly elevated as compared with the static controls, and the OF regime is more conducive to matrix production than the CT vibration mode. Analyses of genes of typical fibroblast hallmarks (tenascin-C, collagen III, and procollagen I) as well as markers for MSC differentiation into nonfibroblastic lineages confirmed MSCs' adaptation of fibroblastic behaviors. Overall, the high-frequency vibratory stimulation, when combined with a synthetic fibrous scaffold, serves as a potent modulator of MSC functions. The novel bioreactor system presented here, as a versatile, yet well-controlled model, offers an in vitro platform for understanding vibration-induced mechanotransduction and for engineering of functional vocal fold tissues.

Possible mechanical roles of glycosaminoglycans in thoracic aortic dissection and associations with dysregulated transforming growth factor-β

BACKGROUND

Four distinguishing histopathological characteristics of thoracic aortic aneurysms and dissections (TAADs) are the fragmentation or degradation of elastic fibers, loss of smooth muscle, pooling of glycosaminoglycans, and remodeling of fibrillar collagens. Of these, pooling of glycosaminoglycans appears to be unique to these lesions.

METHODS

This review acknowledges the importance of dysregulated transforming growth factor-β (TGF-β) in TAADs and offers a complementary hypothesis that increased TGF-β could contribute to the accumulation of glycosaminoglycans in the media of the proximal thoracic aorta. Regardless, observed pools of glycosaminoglycans could decrease tensile strength, cause stress concentrations, and increase intralamellar swelling pressure, all of which could initiate local delaminations that could subsequently propagate as dissections and result in a false lumen or rupture.

CONCLUSIONS

There is a pressing need to investigate potential mechanical as well as biological consequences of accumulated glycosaminoglycans in TAADs and to elucidate responsible signaling pathways, with particular attention to synthetic cells of nonmesodermal lineage. Such research could provide insight into the mechanisms of dissection and the seemingly paradoxical role of the over-expression of a cytokine that is typically associated with fibrosis but is implicated in a degenerative disease of the aorta that can result in a catastrophic mechanical failure.

The Role of Hyaluronan and CD44 in the Pathogenesis of Lupus Nephritis

Systemic lupus erythematosus (SLE) is a prototype autoimmune disease that affects multiorgan systems. Lupus nephritis is one of the most severe manifestations of SLE whereby immune-mediated inflammation can lead to permanent damage within the glomerular, tubulo-interstitial, and vascular compartments of the kidney, resulting in acute or chronic renal failure. The mechanisms that regulate host inflammatory responses and tissue injury are incompletely understood. Accumulating evidence suggests that hyaluronan and its interaction with its cell surface receptor CD44 plays an important role in mediating pathogenic mechanisms in SLE. This paper discusses the putative mechanisms through which hyaluronan and CD44 contribute to the pathogenesis of SLE, with particular emphasis on lupus nephritis.

Pathophysiological changes to the peritoneal membrane during PD-related peritonitis: the role of mesothelial cells

The success of peritoneal dialysis (PD) is dependent on the structural and functional integrity of the peritoneal membrane. The mesothelium lines the peritoneal membrane and is the first line of defense against chemical and/or bacterial insult. Peritonitis remains a major complication of PD and is a predominant cause of technique failure, morbidity and mortality amongst PD patients. With appropriate antibiotic treatment, peritonitis resolves without further complications, but in some PD patients excessive peritoneal inflammatory responses lead to mesothelial cell exfoliation and thickening of the submesothelium, resulting in peritoneal fibrosis and sclerosis. The detrimental changes in the peritoneal membrane structure and function correlate with the number and severity of peritonitis episodes and the need for catheter removal. There is evidence that despite clinical resolution of peritonitis, increased levels of inflammatory and fibrotic mediators may persist in the peritoneal cavity, signifying persistent injury to the mesothelial cells. This review will describe the structural and functional changes that occur in the peritoneal membrane during peritonitis and how mesothelial cells contribute to these changes and respond to infection. The latter part of the review discusses the potential of mesothelial cell transplantation and genetic manipulation in the preservation of the peritoneal membrane.

Pathophysiology of the peritoneal membrane during peritoneal dialysis: the role of hyaluronan

During peritoneal dialysis (PD), constant exposure of mesothelial cells to bioincompatible PD solutions results in the denudation of the mesothelial monolayer and impairment of mesothelial cell function. Hyaluronan, a major component of extracellular matrices, is synthesized by mesothelial cells and contributes to remesothelialization, maintenance of cell phenotype, and tissue remodeling and provides structural support to the peritoneal membrane. Chronic peritoneal inflammation is observed in long-term PD patients and is associated with increased hyaluronan synthesis. During inflammation, depolymerization of hyaluronan may occur with the generation of hyaluronan fragments. In contrast to native hyaluronan which offers a protective role to the peritoneum, hyaluronan fragments exacerbate inflammatory and fibrotic processes and therefore assist in the destruction of the tissue. This paper will discuss the contribution of mesothelial cells to peritoneal membrane alterations that are induced by PD and the putative role of hyaluronan in these processes.

Transforming growth factor-beta 1 in adipose derived stem cells conditioned medium is a dominant paracrine mediator determines hyaluronic acid and collagen expression profile

Conditioned medium from adipose derived stem cells (ADSC-CM) stimulates both collagen synthesis and migration of fibroblasts, and accelerates wound healing in vivo. Recently, the production and secretion of growth factors has been identified as an essential function of adipose-derived stem cells (ADSCs). However, the main soluble factor of ADSC-CM which mediates paracrine effects and its underlying mechanism has not been elucidated yet. In this study, we considered transforming growth factor-beta1 (TGF-β1) as a strong candidate for paracrine effect of ADSC-CM and investigated collagen synthesis and hyaluronic acid synthase (HAS) expression. After ADSC-CM addition, collagen type I, type III, HAS and hyaluronic acid (HA) expressions on human dermal fibroblasts (HDFs) were evaluated. Furthermore, to clarify effects of TGF-β1 as a paracrine mediator, TGF-β1 antibody and external supplementary TGF-β1 were treated to HDFs. Collagens type I, type III, HAS-1 and HAS-2 mRNA expressions of HDFs were greatly increased by ADSC-CM treatment, however there was no change in TGF-β1 antibody treated HDFs compared with non-treated control. These results strongly demonstrate that TGF-β1 plays an important role as a paracrine mediator of ECM synthesis. The fact that TGF-β1 contained in ADSC-CM not only accelerates collagen deposition but also increase hyaluronic acid synthesis of HDFs through HAS-1 and HAS-2 expression was also elucidated in this study. Therefore, ADSC-CM shows promise for the treatment of cutaneous wounds and accelerates granulation formation during healing process.