Cytokine loaded biopolymers as a novel strategy to study stem cells during wound-healing processes

HvRNASET2 Regulate Connective Tissue and Collagen I Remodeling During Wound Healing Process

Several studies have recently demonstrated that the correct regeneration of damaged tissues and the maintaining of homeostasis after wounds or injuries are tightly connected to different biological events, involving immune response, fibroplasia, and angiogenetic processes, in both vertebrates and invertebrates. In this context, our previous data demonstrated that the Hirudo verbana recombinant protein rHvRNASET2 not only plays a pivotal role in innate immune modulation, but is also able to activate resident fibroblasts leading to new collagen production, both in vivo and in vitro. Indeed, when injected in the leech body wall, which represents a consolidated invertebrate model for studying both immune response and tissue regeneration, HvRNASET2 induces macrophages recruitment, fibroplasia, and synthesis of new collagen. Based on this evidence, we evaluate the role of HvRNASET2 on muscle tissue regeneration and extracellular matrix (ECM) remodeling in rHvRNASET2-injected wounded leeches, compared to PBS-injected wounded leeches used as control. The results presented here not only confirms our previous evidence, reporting that HvRNASET2 leads to an increased collagen production, but also shows that an overexpression of this protein might influence the correct progress of muscle tissue regeneration. Moreover, due to its inhibitory effect on vasculogenesis and angiogenesis, HvRNASET2 apparently interfere with the recruitment of the myoendothelial vessel-associated precursor cells that in turn are responsible for muscle regeneration during wound healing repair.

Nanomaterials and Annelid Immunity: A Comparative Survey to Reveal the Common Stress and Defense Responses of Two Sentinel Species to Nanomaterials in the Environment

Simple Summary

Nanotechnology is a dynamically developing field producing large amounts of nanocompounds that are applied in industry, daily life, and health care. During production, use, and waste these materials could end up in water or soil. Large scale contaminations of our environment are a threat to public health. Pollution can have harmful effects on the immune system, as revealed by numerous studies in humans and other vertebrates. The relative simplicity of invertebrate immune functions offers potentially sensitive and accessible means of monitoring the effects and complex interactions of nanoparticles which ultimately affect host resistance. Among terrestrial and freshwater invertebrates, earthworms and leeches are the “keystone” species to evaluate the health of our ecosystems. In this review we compare the conserved stress and immune responses of these invertebrate model organisms toward nanoparticles. The obtained knowledge provides exciting insights into the conserved molecular and cellular mechanisms of nanomaterial-related toxicity in invertebrates and vertebrates. Understanding the unique characteristics of engineered nanoproducts and their interactions with biological systems in our environment is essential to the safe realization of these materials in novel biomedical applications.

Abstract

Earthworms and leeches are sentinel animals that represent the annelid phylum within terrestrial and freshwater ecosystems, respectively. One early stress signal in these organisms is related to innate immunity, but how nanomaterials affect it is poorly characterized. In this survey, we compare the latest literature on earthworm and leeches with examples of their molecular/cellular responses to inorganic (silver nanoparticles) and organic (carbon nanotubes) nanomaterials. A special focus is placed on the role of annelid immunocytes in the evolutionarily conserved antioxidant and immune mechanisms and protein corona formation and probable endocytosis pathways involved in nanomaterial uptake. Our summary helps to realize why these environmental sentinels are beneficial to study the potential detrimental effects of nanomaterials.

Use of a biopolymer delivery system to investigate the influence of interleukin-4 on recruitment of neutrophils in equids

OBJECTIVE

To use a biopolymer delivery system to investigate the ability of interleukin (IL)-4 to recruit neutrophils into subcutaneous tissues of equids.

ANIMALS

16 horses and 2 ponies.

PROCEDURES

Animals were assigned to 3 experiments (6/experiment). Effects of recombinant equine (Req) IL-4 (100, 250, or 500 ng/site) versus a positive control (ReqIL-8; 100 ng, 250 ng, or 1 μg/site) and a negative control (Dulbecco PBSS or culture medium) on neutrophil chemotaxis were assessed after SC injection into the neck with an injectable biopolymer used as the vehicle. Tissue samples including the biopolymer plug were collected by biopsy at various time points from 3 hours to 7 days after injection. Neutrophil infiltration was evaluated by histologic scoring (experiments 1, 2, and 3) or flow cytometry (experiment 3).

RESULTS

Histologic neutrophil infiltration scores did not differ significantly among treatments at most evaluated time points. On flow cytometric analysis, log-transformed neutrophil counts in biopsy specimens were significantly greater for the ReqIL-8 treatment (1 μg/site) than the negative control treatment at 3 but not 6 hours after injection; results did not differ between ReqIL-4 and control treatments at either time point. Negative control treatments induced an inflammatory response in most equids in all experiments.

CONCLUSIONS AND CLINICAL RELEVANCE

Flow cytometry was a more reliable method to estimate neutrophil migration than histologic score analysis. The ReqIL-4 treatment did not induce a detectable neutrophil response, compared with the negative control treatment in this study. Evidence of inflammation in negative control samples suggested the biopolymer is not a suitable vehicle for use in equids.

Antimicrobial Role of RNASET2 Protein During Innate Immune Response in the Medicinal Leech Hirudo verbana

The innate immune response represents a first-line defense against pathogen infection that has been widely conserved throughout evolution. Using the invertebrate Hirudo verbana (Annelida, Hirudinea) as an experimental model, we show here that the RNASET2 ribonuclease is directly involved in the immune response against Gram-positive bacteria. Injection of lipoteichoic acid (LTA), a key component of Gram-positive bacteria cell wall, into the leech body wall induced a massive migration of granulocytes and macrophages expressing TLR2 (the key receptor involved in the response to Gram-positive bacteria) toward the challenged/inoculated area. We hypothesized that the endogenous leech RNASET2 protein (HvRNASET2) might be involved in the antimicrobial response, as already described for other vertebrate ribonucleases, such as RNase3 and RNase7. In support of our hypothesis, HvRNASET2 was mainly localized in the granules of granulocytes, and its release in the extracellular matrix triggered the recruitment of macrophages toward the area stimulated with LTA. The activity of HvRNASET2 was also evaluated on Staphylococcus aureus living cells by means of light, transmission, and scanning electron microscopy analysis. HvRNASET2 injection triggered the formation of S. aureus clumps following a direct interaction with the bacterial cell wall, as demonstrated by immunogold assay. Taken together, our data support the notion that, during the early phase of leech immune response, granulocyte-released HvRNASET2 triggers bacterial clumps formation and, at the same time, actively recruits phagocytic macrophages in order to elicit a rapid and effective eradication of the infecting microorganisms from inoculated area.

The medicinal leech as a valuable model for better understanding the role of a TLR4-like receptor in the inflammatory process

Despite extensive investigation focused on both the molecular characteristics and the expression level of Toll-like receptors (TLRs) during the inflammatory response in vertebrates, few data are available in the literature on the role of these proteins in invertebrate's immune response. Here, we propose the medicinal leech as a valuable model to better elucidate the role of TLR4 and its related products, such as tumor necrosis factor (TNF-α), after activation of the leech peripheral immune system with the endogenous medicinal leech recombinant allograft inflammatory factor-1 (rHmAIF-1) or with an exogenous stimulus, such as lipopolysaccharide (LPS). Our results indicate that activated macrophages (HmAIF-1⁺) and granulocytes (CD11b⁺) express both TLR4 and its coreceptor CD14. Moreover, functional studies performed by injecting a cyanobacterium selective TLR4 antagonist CyP demonstrated that only the TLR4 pathway was blocked, while the immune response caused by lipoteichoic acid (LTA) treatment is not affected. These results are consistent with literature on vertebrates, indicating that TLR4 functions as a LPS receptor while the recognition of LTA may involve other pathways.

AIF-1 and RNASET2 Play Complementary Roles in the Innate Immune Response of Medicinal Leech

Recent studies demonstrated that allograft inflammatory factor-1 (AIF-1) and RNASET2 act as chemoattractants for macrophages and modulate the inflammatory processes in both vertebrates and invertebrates. The expression of these proteins significantly increases after bacterial infection; however, the mechanisms by which they regulate the innate immune response are still poorly defined. Here, we evaluate the effect of bacterial lipopolysaccharide injection on the expression pattern of these genes and the interrelation between them during innate immune response in the medicinal leech, an invertebrate model with a simple anatomy and a marked similarity with vertebrates in inflammatory processes. Collectively, prokaryotic-eukaryotic co-cultures and in vivo infection assays suggest that RNASET2 and AIF-1 play a crucial role in orchestrating a functional cross-talk between granulocytes and macrophages in leeches, resulting in the activation of an effective response against pathogen infection. RNASET2, firstly released by granulocytes, likely plays an early antibacterial role. Subsequently, AIF-1+ RNASET2-recruited macrophages further recruit other macrophages to potentiate the antibacterial inflammatory response. These experimental data are in keeping with the notion of RNA-SET2 acting as an alarmin-like molecule whose role is to locally transmit a "danger" signal (such as a bacterial infection) to the innate immune system in order to trigger an appropriate host response.

A new cellular type in invertebrates: first evidence of telocytes in leech Hirudo medicinalis

Telocytes, a peculiar cell type, were recently found in vertebrates. Hence this cell system has been reported as ubiquitous in the bodies of mammals and interpreted as an important player in innate immunity and tissue regeneration, it is reasonable to look for it also in invertebrates, that rely their integrity solely by innate immunity. Here we describe, at morphological and functional level, invertebrate telocytes from the body of leech Hirudo medicinalis (Annelida), suggesting how these cells, forming a resident stromal 3D network, can influence or participate in different events. These findings support the concepts that leech telocytes: i) are organized in a cellular dynamic and versatile 3D network likewise the vertebrate counterpart; ii) are an evolutionarily conserved immune-neuroendocrine system; iii) form an immuno-surveillance system of resident cells responding faster than migrating immunocytes recruited in stimulated area; iv) communicate with neighbouring cells directly and indirectly, via cell-cell contacts and soluble molecules secreted by multivesicular bodies; v) present within neo-vessels, share with immunocytes the mesodermal lineage; vi) are involved in regenerative processes. In conclusion, we propose that HmTCs, integrating so different functions, might explain the innate immune memory and can be associated with several aged related diseases.

Cellular responses induced by multi-walled carbon nanotubes: in vivo and in vitro studies on the medicinal leech macrophages

The core characteristics of multi-wall carbon nanotubes (MWCNTs) are impressive and attractive for technology however, since their production and use is steadily increasing, their environmental dispersion could be potentially hazardous to animal and human health. For this reason, the identification of new methods and of reliable models to better understand MWCNT effects is essential. Here we propose the medicinal leech as an alternative model to assess the effects of MWCNTs on immune system. Our previous studies have already demonstrated that in vivo MWCNT treatment induces the activation of leech’s macrophages. Here we will focus on the direct effects of MWCNTs on these cells by isolating and culturing leech's macrophages by means of the consolidated Matrigel technique, followed by MWCNT in vitro treatment. Our results indicate that MWCNT administration causes both the decrease of cell proliferation rate and the increase of the apoptotic rate. Furthermore, since oxidative stress is linked with inflammation, reactive oxygen species has been evaluated confirming that their production rate increases after MWCNT treatment. Our experimental approaches demonstrate the ability of MWCNTs inducing a powerful inflammatory response and confirm that the medicinal leech is a good alternative model to study the possible harmful effects of any nanomaterial.

Human recombinant RNASET2-induced inflammatory response and connective tissue remodeling in the medicinal leech

In recent years, several studies have demonstrated that the RNASET2 gene is involved in the control of tumorigenicity in ovarian cancer cells. Furthermore, a role in establishing a functional cross-talk between cancer cells and the surrounding tumor microenvironment has been unveiled for this gene, based on its ability to act as an inducer of the innate immune response. Although several studies have reported on the molecular features of RNASET2, the details on the mechanisms by which this evolutionarily conserved ribonuclease regulates the immune system are still poorly defined. In the effort to clarify this aspect, we report here the effect of recombinant human RNASET2 injection and its role in regulating the innate immune response after bacterial challenge in an invertebrate model, the medicinal leech. We found that recombinant RNASET2 injection induces fibroplasias, connective tissue remodeling and the recruitment of numerous infiltrating cells expressing the specific macrophage markers CD68 and HmAIF1. The RNASET2-mediated chemotactic activity for macrophages has been further confirmed by using a consolidated experimental approach based on injection of the Matrigel biomatrice (MG) supplemented with recombinant RNASET2 in the leech body wall. One week after injection, a large number of CD68⁺ and HmAIF-1⁺ macrophages massively infiltrated MG sponges. Finally, in leeches challenged with lipopolysaccharides (LPS) or with the environmental bacteria pathogen Micrococcus nishinomiyaensis, numerous macrophages migrating to the site of inoculation expressed high levels of endogenous RNASET2. Taken together, these results suggest that RNASET2 is likely involved in the initial phase of the inflammatory response in leeches.

Homolog of allograft inflammatory factor-1 induces macrophage migration during innate immune response in leech

Allograft inflammatory factor-1 (AIF-1) is a 17-kDa cytokine-inducible calcium-binding protein that, in vertebrates, plays an important role in the allograft immune response. Its expression is mostly limited to the monocyte/macrophage lineage. Until recently, AIF-1 was assumed to be a novel molecule involved in inflammatory responses. To clarify this aspect, we have investigated the expression of AIF-1 after bacterial challenge and its potential role in regulating the innate immune response in an invertebrate model, the medicinal leech (Hirudo medicinalis). Analysis of an expressed sequence tag library from the central nervous system of Hirudo revealed the presence of the gene Hmaif-1/alias Hmiba1, showing high homology with vertebrate aif-1. Immunohistochemistry with an anti-HmAIF-1 polyclonal antibody revealed the constitutive presence of this protein in spread CD68(+) macrophage-like cells. A few hours after pathogen (bacterial) injection into the body wall, the amount of these immunopositive cells co-expressing HmAIF-1 and the common leucocyte marker CD45 increased at the injected site. Moreover, the recombinant protein HmAIF-1 induced massive angiogenesis and was a potent chemoattractant for macrophages. Following rHmAIF-1 stimulation, macrophage-like cells co-expressed the macrophage marker CD68 and the surface glycoprotein CD45, which, in vertebrates, seems to have a role in the integrin-mediated adhesion of macrophages and in the regulation of the functional responsiveness of cells to chemoattractants. CD45 is therefore probably involved in leech macrophage-like cell activation and migration towards an inflammation site. We have also examined its potential effect on HmAIF-1-induced signalling.

Early events in annelid regeneration: a cellular perspective

The ability to regenerate extensive portions of the body is widespread among the phylum Annelida and this group includes some of the most highly regenerative animals known. Knowledge of the cellular and molecular basis of regeneration in this group is thus important for understanding how regenerative processes have evolved both within the group and across animal phyla. Here, the cellular basis of annelid regeneration is reviewed, with a focus on the earliest steps of regeneration, namely wound-healing and formation of the blastema. Information from a wide range of annelids is compiled in order to identify common and variable elements. There is a large body of valuable older literature on the cellular basis of regeneration in annelids and an effort is made to review this literature in addition to more recent studies. Annelids typically seal the wound through muscular contraction and undergo some autolysis of tissue at the site of the wound. Bodily injury elicits extensive cell migration toward the wound, involving several different types of cells. Some migrating cells form a tissue-clot and phagocytize damaged tissues, whereas others are inferred to contribute to regenerated tissue, specifically mesodermal tissue. In one annelid subgroup, the clitellates, a group of mesodermal cells, sometimes referred to as neoblasts, is inferred to migrate over considerable distances, with cells moving to the wound from several segments away. Epidermis and gut epithelia severed upon amputation typically heal by fusing with like tissue, although not always. After amputation, cellular contacts with the extracellular matrix are disrupted and major changes in cell morphology and adhesion occur within tissues near the wound. Interactions of tissues at the wound appear key for initiating a blastema, with a particularly important role suggested for the ventral nerve cord, although species are variable in this regard; longer-distance effects mediated by the brain are also reported. The anterior-posterior polarity of the blastema can be mis-assigned, leading most commonly to double-headed worms, and the dorsal-ventral polarity of the blastema appears to be induced by the ventral nerve cord. The blastema is thought to arise from contributions of all three tissue layers, with each layer replacing itself in a tissue-specific manner. Blastemal cells originate mostly locally, although some long-distance migration of source-cells is suggested in clitellates. A number of important questions remain about the cellular basis of regeneration in annelids and addressing many of these would be greatly aided by developing approaches to identify and isolate specific cell types and techniques to image and trace cells in vivo.