The Role of Autophagy and Apoptosis in Affected Skin and Lungs in Patients with Systemic Sclerosis

Systemic sclerosis (SSc) is a complex autoimmune inflammatory disorder with multiple organ involvement. Skin changes present the hallmark of SSc and coincide with poor prognosis. Interstitial lung diseases (ILD) are the most widely reported complications in SSc patients and the primary cause of death. It has been proposed that the processes of autophagy and apoptosis could play a significant role in the pathogenesis and clinical course of different autoimmune diseases, and accordingly in SSc. In this manuscript, we review the current knowledge of autophagy and apoptosis processes in the skin and lungs of patients with SSc. Profiling of markers involved in these processes in skin cells can be useful to recognize the stage of fibrosis and can be used in the clinical stratification of patients. Furthermore, the knowledge of the molecular mechanisms underlying these processes enables the repurposing of already known drugs and the development of new biological therapeutics that aim to reverse fibrosis by promoting apoptosis and regulate autophagy in personalized treatment approach. In SSc-ILD patients, the molecular signature of the lung tissues of each patient could be a distinctive criterion in order to establish the correct lung pattern, which directly impacts the course and prognosis of the disease. In this case, resolving the role of tissue-specific markers, which could be detected in the circulation using sensitive molecular methods, would be an important step toward development of non-invasive diagnostic procedures that enable early and precise diagnosis and preventing the high mortality of this rare disease.

Innovative Human Three-Dimensional Tissue-Engineered Models as an Alternative to Animal Testing

Animal testing has long been used in science to study complex biological phenomena that cannot be investigated using two-dimensional cell cultures in plastic dishes. With time, it appeared that more differences could exist between animal models and even more when translated to human patients. Innovative models became essential to develop more accurate knowledge. Tissue engineering provides some of those models, but it mostly relies on the use of prefabricated scaffolds on which cells are seeded. The self-assembly protocol has recently produced organ-specific human-derived three-dimensional models without the need for exogenous material. This strategy will help to achieve the 3R principles.

Expression of apoptotic and proliferation factors in gastric mucosa of patients with systemic sclerosis correlates with form of the disease

Despite high prevalence of patients with gastric disease in systemic sclerosis (SSc), its pathogenesis is still poorly understood. We immunohistochemically analysed biopsies of gastric mucosa (GM) in 5 controls and 15 patients with different forms of SSc: limited cutaneous (lc), diffuse cutaneous moderate (sys1) and severe (sys2). The number of positive cells was analysed by a Kruskall-Wallis test, P < 0.05 was considered statistically significant. Percentage of proliferating (Ki-67 positive) cells was highest in sys1 (3% in superficial and 4,6% in deeper parts of GM), which dropped to 1% in sys2. Percentage of α-smooth muscle actin (α-SMA) positive cells was 5% in controls, 9% in superficial GM, while in deeper GM rose from 7% to 19% in sys1 and sys2, thus indicating increased myofibroblast population. Caspase-3 positive apoptotic cells characterized 1,5–2% of controls, 8% of superficial and 6% of deeper GM cells in sys1. In sys2, apoptosis affected 50% of surface epithelial and gland cells and 30% of deeper glands, and correlated with increased fibrosis and decreased syndecan-1 expression. Our data demonstrate that sys1 is the most „active” proliferating form of SSc. Sys2 characterize collagen deposition, surface epithelium defects, extensive apoptosis and low proliferation, GM atrophy and loss of function.

Origin of Serum Affects Quality of Engineered Tissues Produced by the Self-Assembly Approach

Despite the emergence of serum-free media for cell culture, the use of serum to supplement the culture media is still essential in order to produce engineered urologic tissues using the self-assembly approach, not only for the stromal compartment but also for the uroepithelium. Effects of sera on thickness of these two compartments were measured and quality of the epithelial differentiation was evaluated. For bladder mucosa substitute reconstruction, the use of postnatal sera failed to produce an adequate uroepithelium whereas the fetal sera supplementation did. Postnatal sera also provided thinner stromal compartments than the one obtained using fetal sera, no matter if the fibroblasts from healthy or psoriatic donors were used to reconstruct human skin substitutes.

Production of a Self-Aligned Scaffold, Free of Exogenous Material, from Dermal Fibroblasts Using the Self-Assembly Technique

Many pathologies of skin, especially ageing and cancer, involve modifications in the matrix alignment. Such tissue reorganization could have impact on cell behaviour and/or more global biological processes. Tissue engineering provides accurate study model by mimicking the skin and it allows the construction of versatile tridimensional models using human cells. It also avoids the use of animals, which gave sometimes nontranslatable results. Among the various techniques existing, the self-assembly method allows production of a near native skin, free of exogenous material. After cultivating human dermal fibroblasts in the presence of ascorbate during two weeks, a reseeding of these cells takes place after elevation of the resulting stroma on a permeable ring and culture pursued for another two weeks. This protocol induces a clear realignment of matrix fibres and cells parallel to the horizon. The thickness of this stretched reconstructed tissue is reduced compared to the stroma produced by the standard technique. Cell count is also reduced. In conclusion, a new, easy, and inexpensive method to produce aligned tissue free of exogenous material could be used for fundamental research applications in dermatology.

Role of seaweed laminaran from Saccharina longicruris on matrix deposition during dermal tissue-engineered production

Our laboratory has developed a technique to reconstruct in vitro tissue from human cells using the self-assembly tissue-engineering method, which utilizes the ability of fibroblasts to deposit the matrix they secrete. The time necessary for tissue construction, several weeks, is a drawback for many clinical uses. We hypothesized that the addition of laminaran can increase the deposition of matrix, speeding up the production of the tissue. Laminaran was isolated from the brown seaweed Saccharina longicruris harvested in Canada and its structure was evaluated. Laminaran is a small molecular weight polysaccharide composed of linear glucose chains. Monolayer-cultured human skin fibroblasts were cultured in the presence of laminaran with ascorbate for 7 or 35 days to produce a dermis. Treatment did not induce any variation in the growth rate or alpha smooth muscle actin content but it did increase the deposition of collagen I in a dose-dependent manner. After 35 days, the reconstructed dermal thickness was increased when laminaran was added, and collagen I deposition and MMP activity were also significantly increased. Thus, laminaran can be used to increase the rate of production of reconstructed self-assembled dermis and can also potentially be used in cosmetic or therapeutic creams to stimulate matrix production.

Redox signaling as a therapeutic target to inhibit myofibroblast activation in degenerative fibrotic disease

Degenerative fibrotic diseases encompass numerous systemic and organ-specific disorders. Despite their associated significant morbidity and mortality, there is currently no effective antifibrotic treatment. Fibrosis is characterized by the development and persistence of myofibroblasts, whose unregulated deposition of extracellular matrix components disrupts signaling cascades and normal tissue architecture leading to organ failure and death. The profibrotic cytokine transforming growth factor beta (TGFβ) is considered the foremost inducer of fibrosis, driving myofibroblast differentiation in diverse tissues. This review summarizes recent in vitro and in vivo data demonstrating that TGF β-induced myofibroblast differentiation is driven by a prooxidant shift in redox homeostasis. Elevated NADPH oxidase 4 (NOX4)-derived hydrogen peroxide (H2O2) supported by concomitant decreases in nitric oxide (NO) signaling and reactive oxygen species scavengers are central factors in the molecular pathogenesis of fibrosis in numerous tissues and organs. Moreover, complex interplay between NOX4-derived H2O2 and NO signaling regulates myofibroblast differentiation. Restoring redox homeostasis via antioxidants or NOX4 inactivation as well as by enhancing NO signaling via activation of soluble guanylyl cyclases or inhibition of phosphodiesterases can inhibit and reverse myofibroblast differentiation. Thus, dysregulated redox signaling represents a potential therapeutic target for the treatment of wide variety of different degenerative fibrotic disorders.

Updates on morphea: role of vascular injury and advances in treatment

Morphea and systemic sclerosis are fibrosing disorders of the skin that share common inflammatory and immunologic pathways that are responsible for the vascular changes, increased collagen production, and extracellular matrix proliferation seen in both conditions. Recent advances in molecular biology techniques have furthered our knowledge of the potential underlying pathogenic mechanisms and offer new and provocative areas of research for novel diagnostic and therapeutic interventions. This review focuses on the role of vascular injury in the development of morphea, the use of ultrasonography as a diagnostic modality, and well-established and newly proposed treatments.

Reconstitution of skin fibrosis development using a tissue engineering approach

Skin fibrosis is involved in several pathologies as hypertrophic scar or scleroderma. The determination of the mechanisms at the origin of these problems is however difficult due to the low number of in vivo models. To bypass this absence of animal models, studies typically use human pathological cells cultured in a monolayer way on plastic. However, cell behavior is different according to the fact that cells are on plastic or embedded in matrix. Using a tissue engineering method, we have developed new in vitro models to study these pathologies of the skin. Human pathological cells are used to reconstitute a three dimensional fibrotic tissue comprising the dermal and the epidermal parts of the skin. This method is called the self-assembly approach and is based on the cell capacity to reconstitute in vitro their own environment as in vivo. In this chapter, protocols generating reconstructed pathological skin using this approach are detailed. The methods include extraction and culture of human skin keratinocytes and fibroblasts from very small cutaneous biopsies. In addition, a description of the protocols for the production of fibrotic dermal sheets can be found to obtain a model of fibrotic dermis that can be associated or not with a fully differentiated epidermis.

Therapeutic targeting of redox signaling in myofibroblast differentiation and age-related fibrotic disease

Myofibroblast activation plays a central role during normal wound healing. Whereas insufficient myofibroblast activation impairs wound healing, excessive myofibroblast activation promotes fibrosis in diverse tissues (including benign prostatic hyperplasia, BPH) leading to organ dysfunction and also promotes a stromal response that supports tumor progression. The incidence of impaired wound healing, tissue fibrosis, BPH, and certain cancers strongly increases with age. This paper summarizes findings from in vitro fibroblast-to-myofibroblast differentiation systems that serve as cellular models to study fibrogenesis of diverse tissues. Supported by substantial in vivo data, a large body of evidence indicates that myofibroblast differentiation induced by the profibrotic cytokine transforming growth factor beta is driven by a prooxidant shift in redox homeostasis due to elevated production of NADPH oxidase 4 (NOX4)-derived hydrogen peroxide and supported by concomitant decreases in nitric oxide/cGMP signaling and reactive oxygen species (ROS) scavenging enzymes. Fibroblast-to-myofibroblast differentiation can be inhibited and reversed by restoring redox homeostasis using antioxidants or NOX4 inactivation as well as enhancing nitric oxide/cGMP signaling via activation of soluble guanylyl cyclases or inhibition of phosphodiesterases. Current evidence indicates the therapeutic potential of targeting the prooxidant shift in redox homeostasis for the treatment of age-related diseases associated with myofibroblast dysregulation.

Annexin A2 and A5 serve as new ligands for C1q on apoptotic cells

C1q is the initiator of the classical complement pathway and opsonizes apoptotic cells to facilitate phagocytosis. Deficiency of C1q is the strongest known risk factor for development of systemic lupus erythematosus (SLE), which appears to be related to ensuing impaired clearance of apoptotic material. The objective of the current study was to investigate new ligands for C1q on the surface of apoptotic cells. We revealed that the two phospholipid-binding proteins annexin A2 and A5 are, beside DNA, significant C1q ligands. We furthermore, demonstrated that C1q binds directly to histones exposed on the surface of dying cells but we did not detect significant interaction with phosphatidylserine. The complement inhibitors C4b-binding protein and factor H also interact with dying cells, most likely to decrease complement activation beyond the level of C3 to allow noninflammatory clearance. Despite the fact that C4b-binding protein, factor H, and C1q share some ligands on dying cells, we showed that these three proteins did not compete with one another for binding to apoptotic cells. We additionally demonstrated that the way in which apoptosis is induced influenced both the degree of apoptosis and the binding of C1q. The knowledge, that annexin A2 and A5 act as ligands for C1q on apoptotic cells, sheds new light on the pathophysiology of autoimmune diseases.

Apoptosis modulation as a promising target for treatment of systemic sclerosis

Diffuse systemic sclerosis (SSc) is a fatal autoimmune disease characterized by an excessive ECM deposition inducing a loss of function of skin and internal organs. Apoptosis is a key mechanism involved in all the stages of the disease: vascular damage, immune dysfunction, and fibrosis. The purpose of this paper is to gather new findings in apoptosis related to SSc, to highlight relations between apoptosis and fibrosis, and to identify new therapeutic targets.

Myofibroblast differentiation and survival in fibrotic disease

During wound healing, contractile fibroblasts called myofibroblasts regulate the formation and contraction of granulation tissue; however, pathological and persistent myofibroblast activation, which occurs in hypertrophic scars or tissue fibrosis, results in a loss of function. Many reviews outline the cellular and molecular features of myofibroblasts and their roles in a variety of diseases. This review focuses on the origins of myofibroblasts and the factors that control their differentiation and prolonged survival in fibrotic tissues. Pulmonary fibrosis is used to illustrate many key points, but examples from other tissues and models are also included. Myofibroblasts originate mostly from tissue-resident fibroblasts, and also from epithelial and endothelial cells or other mesenchymal precursors. Their differentiation is influenced by cytokines, growth factors, extracellular matrix composition and stiffness, and cell surface molecules such as proteoglycans and THY1, among other factors. Many of these effects are modulated by cell contraction. Myofibroblasts resist programmed cell death, which promotes their accumulation in fibrotic tissues. The cause of resistance to apoptosis in myofibroblasts is under ongoing investigation, but many of the same stimuli that regulate their differentiation are involved. The contributions of oxidative stress, the WNT-β-catenin pathway and PPARγ to myofibroblast differentiation and survival are increasingly appreciated.