Decrease of laminin-511 in the basement membrane due to photoaging reduces epidermal stem/progenitor cells

Bioinformatics-based analysis of the relationship between plasminogen regulatory genes and photoaging

BACKGROUND

Ultraviolet radiation causes skin photoaging by producing a variety of enzymes, which impact both skin health and hinder beauty. Currently, the early diagnosis and treatment of photoaging remain a challenge. Bioinformatics analysis has strong advantages in exploring core genes and the biological pathways of photoaging.

AIMS

To screen and validate key risk genes associated with plasminogen in photoaging and to identify potential target genes for photoaging.

METHODS

Two human transcriptome datasets were obtained by searching the Gene Expression Omnibus (GEO) database, and the mRNAs in the GSE131789 dataset were differentially analyzed, and then the weighted gene co-expression network analysis (WGCNA) was performed to find out the strongest correlations. Template genes, interaction analysis of differentially expressed genes (DEGs), modular genes with the most WGCNA correlations, and genecard database genes related to plasminogen were performed, and further Kyoto genes and Genome Encyclopedia (KEGG) pathway analysis. Two different algorithms, least absolute shrinkage and selection operator (LASSO) and support vector machines-recursive feature elimination (SVM-RFE), were used to find key genes. Then the data set (GSE206495) was validated and analyzed. Real-time PCR was performed to validate the expression of key genes through in vitro cellular experiments.

RESULTS

IFI6, IFI44L, HRSP12, and BMP4 were screened from datasets as key genes for photoaging and further analysis showed that these genes have significant diagnostic value for photoaging.

CONCLUSION

IFI6, IFI44L, HRSP12, and BMP4 play a key role in the pathogenesis of photoaging, and serve as promising potential predictive biomarkers for photoaging.

The Tumor Stroma of Squamous Cell Carcinoma: A Complex Environment That Fuels Cancer Progression

The tumor microenvironment (TME), a complex assembly of cellular and extracellular matrix (ECM) components, plays a crucial role in driving tumor progression, shaping treatment responses, and influencing metastasis. This narrative review focuses on the cutaneous squamous cell carcinoma (cSCC) tumor stroma, highlighting its key constituents and their dynamic contributions. We examine how significant changes within the cSCC ECM-specifically, alterations in fibronectin, hyaluronic acid, laminins, proteoglycans, and collagens-promote cancer progression, metastasis, and drug resistance. The cellular composition of the cSCC TME is also explored, detailing the intricate interplay of cancer-associated fibroblasts (CAFs), mesenchymal stem cells (MSCs), endothelial cells, pericytes, adipocytes, and various immune cell populations. These diverse players modulate tumor development, angiogenesis, and immune responses. Finally, we emphasize the TME's potential as a therapeutic target. Emerging strategies discussed in this review include harnessing the immune system (adoptive cell transfer, checkpoint blockade), hindering tumor angiogenesis, disrupting CAF activity, and manipulating ECM components. These approaches underscore the vital role that deciphering TME interactions plays in advancing cSCC therapy. Further research illuminating these complex relationships will uncover new avenues for developing more effective treatments for cSCC.

The role of interface geometry and appendages on the mesoscale mechanics of the skin

The skin is the largest organ in the human body and serves various functions, including mechanical protection and mechanosensation. Yet, even though skin's biomechanics are attributed to two main layers-epidermis and dermis-computational models have often treated this tissue as a thin homogeneous material or, when considering multiple layers, have ignored the most prominent heterogeneities of skin seen at the mesoscale. Here, we create finite element models of representative volume elements (RVEs) of skin, including the three-dimensional variation of the interface between the epidermis and dermis as well as considering the presence of hair follicles. The sinusoidal interface, which approximates the anatomical features known as Rete ridges, does not affect the homogenized mechanical response of the RVE but contributes to stress concentration, particularly at the valleys of the Rete ridges. The stress profile is three-dimensional due to the skin's anisotropy, leading to high-stress bands connecting the valleys of the Rete ridges through one type of saddle point. The peaks of the Rete ridges and the other class of saddle points of the sinusoidal surface form a second set of low-stress bands under equi-biaxial loading. Another prominent feature of the heterogeneous stress pattern is a switch in the stress jump across the interface, which becomes lower with respect to the flat interface at increasing deformations. These features are seen in both tension and shear loading. The RVE with the hair follicle showed strains concentrating at the epidermis adjacent to the hair follicle, the epithelial tissue surrounding the hair right below the epidermis, and the bulb or base region of the hair follicle. The regions of strain concentration near the hair follicle in equi-biaxial and shear loading align with the presence of distinct mechanoreceptors in the skin, except for the bulb or base region. This study highlights the importance of skin heterogeneities, particularly its potential mechanophysiological role in the sense of touch and the prevention of skin delamination.

Dual delivery gene-activated scaffold directs fibroblast activity and keratinocyte epithelization

Fibroblasts are the most abundant cell type in dermal skin and keratinocytes are the most abundant cell type in the epidermis; both play a crucial role in wound remodeling and maturation. We aim to assess the functionality of a novel dual gene activated scaffold (GAS) on human adult dermal fibroblasts (hDFs) and see how the secretome produced could affect human dermal microvascular endothelial cells (HDMVECs) and human epidermal keratinocyte (hEKs) growth and epithelization. Our GAS is a collagen chondroitin sulfate scaffold loaded with pro-angiogenic stromal derived factor (SDF-1α) and/or an anti-aging β-Klotho plasmids. hDFs were grown on GAS for two weeks and compared to gene-free scaffolds. GAS produced a significantly better healing outcome in the fibroblasts than in the gene-free scaffold group. Among the GAS groups, the dual GAS induced the most potent pro-regenerative maturation in fibroblasts with a downregulation in proliferation (twofold, p < 0.05), fibrotic remodeling regulators TGF-β1 (1.43-fold, p < 0.01) and CTGF (1.4-fold, p < 0.05), fibrotic cellular protein α-SMA (twofold, p < 0.05), and fibronectin matrix deposition (twofold, p < 0.05). The dual GAS secretome also showed enhancements of paracrine keratinocyte pro-epithelializing ability (1.3-fold, p < 0.05); basement membrane regeneration through laminin (6.4-fold, p < 0.005) and collagen IV (8.7-fold, p < 0.005) deposition. Our findings demonstrate enhanced responses in dual GAS containing hDFs by proangiogenic SDF-1α and β-Klotho anti-fibrotic rejuvenating activities. This was demonstrated by activating hDFs on dual GAS to become anti-fibrotic in nature while eliciting wound repair basement membrane proteins; enhancing a proangiogenic HDMVECs paracrine signaling and greater epithelisation of hEKs.

Anti-Photoaging Effects of Upcycled Citrus junos Seed Anionic Peptides on Ultraviolet-Radiation-Induced Skin Aging in a Reconstructed Skin Model

Side streams and byproducts of food are established sources of natural ingredients in cosmetics. In the present study, we obtained upcycled low-molecular-weight anionic peptides (LMAPs) using byproducts of the post-yuzu-juicing process by employing an enzyme derived from Bacillus sp. For the first time, we isolated anionic peptides less than 500 Da in molecular weight from Citrus junos TANAKA seeds via hydrolysis using this enzyme. The protective effect of LMAPs against UVR-induced photoaging was evaluated using a reconstructed skin tissue (RST) model and keratinocytes. The LMAPs protected the keratinocytes by scavenging intracellular reactive oxygen species and by reducing the levels of paracrine cytokines (IL-6 and TNF-α) in UVR (UVA 2 J/cm2 and UVB 15 mJ/cm2)-irradiated keratinocytes. Additionally, the increase in melanin synthesis and TRP-2 expression in RST caused by UVR was significantly inhibited by LMAP treatment. This treatment strongly induced the expression of filaggrin and laminin-5 in UVR-irradiated RST. It also increased type I collagen expression in the dermal region and in fibroblasts in vitro. These results suggest that a hydrolytic system using the enzyme derived from Bacillus sp. can be used for the commercial production of LMAPs from food byproducts and that these LMAPs can be effective ingredients for improving photoaging-induced skin diseases.

Recent advances in exosomal non-coding RNA-based therapeutic approaches for photoaging

BACKGROUND

Photoaging is a degenerative biological process that affects the quality of life. It is caused by environmental factors including ultraviolet radiation (UVR), deep skin burns, smoking, active oxygen, chemical substances, and trauma. Among them, UVR plays a vital role in the aging process.

AIM

With the continuous development of modern medicine, clinical researchers have investigated novel approaches to treat aging. In particular, mesenchymal stem cells (MSCs), non-coding RNAs are involved in various physiological processes have broad clinical application as they have the advantages of convenient samples, abundant sources, and avoidable ethical issues.

METHODS

This article reviews research progress on five types of stem cell, exosomes, non-coding RNA in the context of photoaging treatment: adipose-derived stem cell, human umbilical cord MSCs, epidermal progenitor cells, keratinocyte stem cells, and hair follicle stem cells (HFSCs). It also includes stem cell related exosomes and their non-coding RNA research.

RESULTS

The results have clinical guiding significance for prevention and control of the onset and development of photoaging. It is found that stem cells secrete cytokines, cell growth factors, non-coding RNA, exosomes and proteins to repair aging skin tissues and achieve skin rejuvenation. In particular, stem cell exosomes and non-coding RNA are found to have significant research potential, as they possess the benefits of their source cells without the disadvantages which include immune rejection and granuloma formation.

Effect of red light on epidermal proliferation and mitochondrial activity

BACKGROUND/PURPOSE

We previously demonstrated that irradiation with red light accelerates recovery of the epidermal water-impermeable barrier, whereas blue light delays it, and white and green light have no effect. Here, we aimed to examine in detail the effects of red and blue light in a human epidermal-equivalent model and in human skin.

METHODS

We used light-emitting diodes (red light, 630 nm, 6.2 mW/cm2 ; blue light, 463 nm, 6.2 mW/cm2 ) for irradiation of an epidermal-equivalent model and human skin. Cell proliferation was evaluated by means of BrdU and Ki-67 staining, and mitochondrial activity was quantified with an extracellular flux analyzer.

RESULTS

Irradiation of the epidermal-equivalent model with red light for 2 h (44.64 J/cm2 ) increased both epidermal proliferation in the basal layer and mitochondrial activity. Blue light had no effect on epidermal proliferation. Furthermore, irradiation with red light for 2 h on three consecutive days increased epidermal proliferation in human skin tissue in culture.

CONCLUSION

These results suggest that red light accelerates epidermal proliferation in both an epidermal-equivalent model and human skin, and may promote epidermal homeostasis.

The Role of Interface Geometry and Appendages on the Mesoscale Mechanics of the Skin

The skin is the largest organ in the human body and serves various functions, including mechanical protection and mechanosensation. Yet, even though skin's biomechanics are attributed to two main layers - epidermis and dermis-computational models have often treated this tissue as a thin homogeneous material or, when considering multiple layers, have ignored the most prominent heterogeneities of skin seen at the mesoscale. Here we create finite element models of representative volume elements (RVEs) of skin, including the three-dimensional variation of the interface between the epidermis and dermis as well as considering the presence of hair follicles. The sinusoidal interface, which approximates the anatomical features known as Rete ridges, does not affect the homogenized mechanical response of the RVE but contributes to stress concentration, particularly at the valleys of the Rete ridges. The stress profile is three-dimensional due to the skin's anisotropy, leading to high-stress bands connecting the valleys of the Rete ridges through one type of saddle point. The peaks of the Rete ridges and the other class of saddle points of the sinusoidal surface form a second set of low-stress bands under equi-biaxial loading. Another prominent feature of the heterogeneous stress pattern is a switch in the stress jump across the interface, which becomes lower with respect to the flat interface at increasing deformations. These features are seen in both tension and shear loading. The RVE with the hair follicle showed strains concentrating at the epidermis adjacent to the hair follicle, the epithelial tissue surrounding the hair right below the epidermis, and the bulb or base region of the hair follicle. The regions of strain concentration near the hair follicle in equi-biaxial and shear loading align with the presence of distinct mechanoreceptors in the skin, except for the bulb or base region. This study highlights the importance of skin heterogeneities, particularly its potential mechanophysiological role in the sense of touch and the prevention of skin delamination.

Cell-binding peptides on the material surface guide stem cell fate of adhesion, proliferation and differentiation

Human cells, especially stem cells, need to communicate and interact with extracellular matrix (ECM) proteins, which not only serve as structural components but also guide and support cell fate and properties such as cell adhesion, proliferation, survival and differentiation. The binding of the cells with ECM proteins or ECM-derived peptides via cell adhesion receptors such as integrins activates several signaling pathways that determine the cell fate, morphological change, proliferation and differentiation. The development of synthetic ECM protein-derived peptides that mimic the biological and biochemical functions of natural ECM proteins will benefit academic and clinical application. Peptides derived from or inspired by specific ECM proteins can act as agonists of each ECM protein receptor. Given that most ECM proteins function in cell adhesion via integrin receptors, many peptides have been developed that bind to specific integrin receptors. In this review, we discuss the peptide sequence, immobilization design, reaction method, and functions of several ECM protein-derived peptides. Various peptide sequences derived from mainly ECM proteins, which are used for coating or grafting on dishes, scaffolds, hydrogels, implants or nanofibers, have been developed to improve the adhesion, proliferation or differentiation of stem cells and to culture differentiated cells. This review article will help to inform the optimal choice of ECM protein-derived peptides for the development of scaffolds, implants, hydrogels, nanofibers and 2D cell culture dishes to regulate the proliferation and direct the differentiation of stem cells into specific lineages.

Mechanism of action and therapeutic effects of oxidative stress and stem cell-based materials in skin aging: Current evidence and future perspectives

Aging is associated with multiple degenerative diseases, including atherosclerosis, osteoporosis, and Alzheimer's disease. As the most intuitive manifestation of aging, skin aging has received the most significant attention. Skin aging results from various intrinsic and extrinsic factors. Aged skin is characterized by wrinkles, laxity, elastosis, telangiectasia, and aberrant pigmentation. The underlying mechanism is complex and may involve cellular senescence, DNA damage, oxidative stress (OS), inflammation, and genetic mutations, among other factors. Among them, OS plays an important role in skin aging, and multiple antioxidants (e.g., vitamin C, glutathione, and melatonin) are considered to promote skin rejuvenation. In addition, stem cells that exhibit self-replication, multi-directional differentiation, and a strong paracrine function can exert anti-aging effects by inhibiting OS. With the further development of stem cell technology, treatments related to OS mitigation and involving stem cell use may have a promising future in anti-skin aging therapy.

α-Ionone protects against UVB-induced photoaging in epidermal keratinocytes

Objective

To evaluate whether α-ionone, an aromatic compound mainly found in raspberries, carrots, roasted almonds, fruits, and herbs, inhibits UVB-mediated photoaging and barrier dysfunction in a human epidermal keratinocyte cell line (HaCaT cells).

Methods

The anti-photoaging effect of α-ionone was evaluated by detecting the expression of barrier-related genes and matrix metalloproteinases (MMPs) in HaCaT cells. The levels of reactive oxygen species, oxidation product, antioxidant enzyme, and inflammatory factors were further analysed to underline the protective effect of α-ionone on epidermal photoaging.

Results

It was found that α-ionone attenuated UVB-induced barrier dysfunction by reversing keratin 1 and filaggrin in HaCaT cells. α-Ionone also reduced the protein amount of MMP-1 and mRNA expression of MMP-1 and MMP-3 in UVB-irradiated HaCaT cells, implying protective effects on extracellular matrix. Furthermore, HaCaT cells exposed to α-ionone showed significant decreases in interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor-α as compared to UVB-irradiated HaCaT cells. α-Ionone treatment significantly inhibited the UVB-induced intracellular reactive oxygen species increase and malondialdehyde accumulation. Therefore, the beneficial effects of α-ionone on inhibiting MMPs secretion and barrier damage may be related to attenuated inflammation and oxidative stress.

Conclusion

Our results highlight the protective effects of α-ionone on epidermal photoaging and promote its clinic application as a potential natural anti-photodamage agent in future.

Laminin N-terminus (LaNt) proteins, laminins and basement membrane regulation

Basement membranes (BMs) are structured regions of the extracellular matrix that provide multiple functions including physical support and acting as a barrier, as a repository for nutrients and growth factors, and as biophysical signalling hubs. At the core of all BMs is the laminin (LM) family of proteins. These large heterotrimeric glycoproteins are essential for tissue integrity, and differences between LM family members represent a key nexus in dictating context and tissue-specific functions. These variations reflect genetic diversity within the family, which allows for multiple structurally and functionally distinct heterotrimers to be produced, each with different architectures and affinities for other matrix proteins and cell surface receptors. The ratios of these LM isoforms also influence the biophysical properties of a BM owing to differences in their relative ability to form polymers or networks. Intriguingly, the LM superfamily is further diversified through the related netrin family of proteins and through alternative splicing leading to the generation of non-LM short proteins known as the laminin N-terminus (LaNt) domain proteins. Both the netrins and LaNt proteins contain structural domains involved in LM-to-LM interaction and network assembly. Emerging findings indicate that one netrin and at least one LaNt protein can potently influence the structure and function of BMs, disrupting the networks, changing physical properties, and thereby influencing tissue function. These findings are altering the way that we think about LM polymerisation and, in the case of the LaNt proteins, suggest a hitherto unappreciated form of LM self-regulation.

The basement membrane in epidermal polarity, stemness, and regeneration

The epidermis is a specialized epithelium that constitutes the outermost layer of the skin, and it provides a protective barrier against environmental assaults. Primarily consisting of multilayered keratinocytes, the epidermis is continuously renewed by proliferation of stem cells and the differentiation of their progeny, which undergo terminal differentiation as they leave the basal layer and move upward toward the surface, where they die and slough off. Basal keratinocytes rest on a basement membrane at the dermal-epidermal junction that is composed of specific extracellular matrix proteins organized into interactive and mechanically supportive networks. Firm attachment of basal keratinocytes, and their dynamic regulation via focal adhesions and hemidesmosomes, is essential for maintaining major skin processes, such as self-renewal, barrier function, and resistance to physical and chemical stresses. The adhesive integrin receptors expressed by epidermal cells serve structural, signaling, and mechanosensory roles that are critical for epidermal cell anchorage and tissue homeostasis. More specifically, the basement membrane components play key roles in preserving the stem cell pool, and establishing cell polarity cues enabling asymmetric cell divisions, which result in the transition from a proliferative basal cell layer to suprabasal cells committed to terminal differentiation. Finally, through a well-regulated sequence of synthesis and remodeling, the components of the dermal-epidermal junction play an essential role in regeneration of the epidermis during skin healing. Here too, they provide biological and mechanical signals that are essential to the restoration of barrier function.

Stiffening Matrix Induces Age-Mediated Microvascular Phenotype Through Increased Cell Contractility and Destabilization of Adherens Junctions

Aging is a major risk factor in microvascular dysfunction and disease development, but the underlying mechanism remains largely unknown. As a result, age-mediated changes in the mechanical properties of tissue collagen have gained interest as drivers of endothelial cell (EC) dysfunction. 3D culture models that mimic age-mediated changes in the microvasculature can facilitate mechanistic understanding. A fibrillar hydrogel capable of changing its stiffness after forming microvascular networks is established. This hydrogel model is used to form vascular networks from induced pluripotent stem cells under soft conditions that mimic young tissue mechanics. Then matrix stiffness is gradually increased, thus exposing the vascular networks to the aging-mimicry process in vitro. It is found that upon dynamic matrix stiffening, EC contractility is increased, resulting in the activation of focal adhesion kinase and subsequent dissociation of β-catenin from VE-Cadherin mediated adherens junctions, leading to the abruption of the vascular networks. Inhibiting cell contractility impedes the dissociation of β-catenin, thereby preventing the deconstruction of adherens junctions, thus partially rescuing the age-mediated vascular phenotype. The findings provide the first direct evidence of matrix's dynamic mechano-changes in compromising microvasculature with aging and highlight the importance of hydrogel systems to study tissue-level changes with aging in basic and translational studies.

Age-related decrease in responsiveness of CD271-positive skin stem cells to growth factors

Previous studies have demonstrated that the numbers of interfollicular epidermal stem cells (IFE-SCs) and dermal stem cells (DSCs) decrease with age and that this decrease is attributed to the age-related deterioration of skin homeostatic functions and the delay in wound healing. Meanwhile, functional decline in the stem cells is also considered to be responsible for the deteriorated skin homeostatic functions and the delayed wound healing associated with aging. In the present study, we focused on epidermal growth factor/epidermal growth factor receptor (EGF/EGFR) signaling and fibroblast growth factor-2/fibroblast growth factor receptor (FGF2/FGFR) signaling to analyze the age-related changes. Immunohistological analysis revealed that the expressions of EGFR and FGFR1 declined in IFE-SCs and DSCs with age, respectively. Additionally, IFE-SCs and DSCs isolated from the skin samples of elderly subjects exhibited lowered responsiveness to EGF and FGF2, respectively. These results suggest that the lowered responsiveness of the skin stem cells to growth factors may be a factor involved in the age-related deterioration of skin regenerative functions during wound healing and skin homeostatic functions. We hope that homeostatic and wound healing functions in the skin could be maintained if the decreased expressions of EGFR and FGFR1 in IFE-SCs and DSCs, respectively, can be suppressed.

Regeneration of collagen fibrils at the papillary dermis by reconstructing basement membrane at the dermal-epidermal junction

The epidermal basement membrane deteriorates with aging. We previously reported that basement membrane reconstruction not only serves to maintain epidermal stem/progenitor cells in the epidermis, but also increases collagen fibrils in the papillary dermis. Here, we investigated the mechanism of the latter action. Collagen fibrils in the papillary dermis were increased in organotypic human skin culture treated with matrix metalloproteinase and heparinase inhibitors. The expression levels of COL5A1 and COL1A1 genes (encoding collagen type V α 1 chain and collagen type I α 1 chain, respectively) were increased in fibroblasts cultured with conditioned medium from a skin equivalent model cultured with the inhibitors and in keratinocytes cultured on laminin-511 E8 fragment-coated plates. We then examined cytokine expression, and found that the inhibitors increased the expression of PDGF-BB (platelet-derived growth factor consisting of two B subunits) in epidermis. Expression of COL5A1 and COL1A1 genes was increased in cultured fibroblasts stimulated with PDGF-BB. Further, the bifunctional inhibitor hydroxyethyl imidazolidinone (HEI) increased skin elasticity and the thickness of the papillary dermis in the skin equivalent. Taken together, our data suggests that reconstructing the basement membrane promotes secretion of PDGF-BB by epidermal keratinocytes, leading to increased collagen expression at the papillary dermis.

A decellularized extracellular matrix derived from keratinocytes can suppress cellular senescence induced by replicative and oxidative stresses

Keratinocyte senescence is suppressed on a keratinocyte-derived decellularized ECM (dECM) through the increase of antioxidant activity. Keratinocyte function is also increased on this dECM, suggesting that this dECM is useful to establish epidermal models.

α2β1 integrins spatially restrict Cdc42 activity to stabilise adherens junctions

Background

Keratinocytes form the main protective barrier in the skin to separate the underlying tissue from the external environment. In order to maintain this barrier, keratinocytes form robust junctions between neighbouring cells as well as with the underlying extracellular matrix. Cell–cell adhesions are mediated primarily through cadherin receptors, whereas the integrin family of transmembrane receptors is predominantly associated with assembly of matrix adhesions. Integrins have been shown to also localise to cell–cell adhesions, but their role at these sites remains unclear.

Results

Here we show that α2β1 integrins are enriched at mature keratinocyte cell–cell adhesions, where they play a crucial role in organising cytoskeletal networks to stabilize adherens junctions. Loss of α2β1 integrin has significant functional phenotypes associated with cell–cell adhesion destabilisation, including increased proliferation, reduced migration and impaired barrier function. Mechanistically, we show that α2β1 integrins suppress activity of Src and Shp2 at cell–cell adhesions leading to enhanced Cdc42–GDI interactions and stabilisation of junctions between neighbouring epithelial cells.

Conclusion

Our data reveals a new role for α2β1 integrins in controlling integrity of epithelial cell–cell adhesions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01054-9.

Gradients in the in vivo intestinal stem cell compartment and their in vitro recapitulation in mimetic platforms

Intestinal tissue, and specifically its mucosal layer, is a complex and gradient-rich environment. Gradients of soluble factor (BMP, Noggin, Notch, Hedgehog, and Wnt), insoluble extracellular matrix proteins (laminins, collagens, fibronectin, and their cognate receptors), stromal stiffness, oxygenation, and sheer stress induced by luminal fluid flow at the crypt-villus axis controls and supports healthy intestinal tissue homeostasis. However, due to current technological challenges, very few of these features have so far been included in in vitro intestinal tissue mimetic platforms. In this review, the tightly defined and dynamic microenvironment of the intestinal tissue is presented in detail. Additionally, the authors introduce the current state-of-the-art intestinal tissue mimetic platforms, as well as the design drawbacks and challenges they face while attempting to capture the complexity of the intestinal tissue's physiology. Finally, the compositions of an "idealized" mimetic system is presented to guide future developmental efforts.