Co-culture of intestinal epithelial and stromal cells in 3D collagen-based environments

Protective effects of engineered Lactobacillus crispatus strains expressing G-CSF on thin endometrium of mice

STUDY QUESTION

Does recombinant Lactobacillus expressing granulocyte colony-stimulating factor (G-CSF) have a better protective effect than the current treatment of thin endometrium (TE)?

SUMMARY ANSWER

This study suggested that the intrauterine injection of Lactobacillus crispastus (L. crispastus)-pPG612-G-CSF has a positive effect on preventing TE induced by 95% alcohol in mice.

WHAT IS KNOWN ALREADY

TE has a negative impact on the success rate of ART in patients, and is usually caused by intrauterine surgery, endometrial infection, or hormone drugs. Exogenous G-CSF can promote endometrial vascular remodelling and increase endometrial receptivity and the embryo implantation rate. Moreover, Lactobacillus plays a crucial role in maintaining and regulating the local microecological balance of the reproductive tract, and it could be a delivery carrier of the endometrial repair drug G-CSF.

STUDY DESIGN, SIZE, DURATION

We constructed engineered L. crispastus strains expressing G-CSF. The mice were divided into five groups: (i) Control group (C, n = 28), uteri were treated with preheated saline solution via intrauterine injection on the third and sixth day of oestrus; (ii) Model group (M, n = 35), where uteri were treated with 95% alcohol on the third day of oestrus and preheated saline solution on the sixth day of oestrus via intrauterine injection; (iii) L. crispatus-pPG612-treatment group (L, n = 45), where uteri were treated with 95% alcohol on the third day of oestrus and 0.1 ml × 108 CFU/ml L. crispatus-pPG612 on the sixth day of oestrus via intrauterine injection; (iv) L. crispatus-pPG612-treatment group (LG, n = 45), where uteri were treated with 95% alcohol on the third day of oestrus and 0.1 ml × 108 CFU/ml L. crispatus-pPG612-G-CSF on the sixth day of oestrus via intrauterine injection; (v) G-CSF-treatment group (G, n = 52), where uteri were treated with 95% alcohol on the third day of oestrus and 30 µg/kg G-CSF on the sixth day of oestrus via intrauterine injection. Then, we compared the effects of L. crispastus, L. crispatus-pPG612-G-CSF and G-CSF on endometrial thickness, angiogenesis, fibrosis, and inflammation in the TE mouse.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We collected uterine tissues for haematoxylin-eosin staining, immunohistochemical staining, Western blot and RT-PCR, as well as serum for ELISA and uterine flushing solution for high-throughput sequencing.

MAIN RESULTS AND THE ROLE OF CHANCE

Compared with those in the M group (the mice of the group were intrauterine injected 95% alcohol and treated with saline solution), the L. crispatus-pPG612-G-CSF strain increased the thickness of the endometrium (P < 0.001) and the number of blood vessels and glands (both P < 0.001), enhanced the expression of cytokeratin 19 (CK19) (P < 0.001), vimentin (Vim) (P < 0.001), vascular endothelial growth factor-A (P < 0.001), and CD34 (P < 0.001), and decreased fibrosis levels (P = 0.004). In addition, the high-throughput sequencing results indicated that the L. crispatus-pPG612-G-CSF strain could decrease the abundance of Pseudomonas (P = 0.044) and Actinomyces spp. (P = 0.094) in TE mice and increased the average number of embryos (P = 0.036). Finally, the L. crispatus-pPG612-G-CSF strain was preliminarily confirmed to activate the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) signalling pathway and enhance the mRNA expression of hypoxia-inducible factor-1α (P < 0.001), vascular endometrial growth factor (P = 0.003), and endothelial cell nitric oxide synthase (P = 0.003) in mouse uterine tissue.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Therapy with the L. crispatus-pPG612-G-CSF strain has tremendous potential to accelerate the reparative processes of TE. However, we have reported only the expression of genes and proteins related to the PI3K/AKT pathway, and numerous other mechanisms may also be involved in the restoration of the endometrium by L. crispatus-pPG612-G-CSF.

WIDER IMPLICATIONS OF THE FINDINGS

The results from the study provide new ideas and suggest new methods for TE treatment.

STUDY FUNDING/COMPETING INTEREST(S)

This work was financially supported by the Project of Science and Technology Development Plan of Jilin Province (grant number 20210101232JC), the Science and Technology Plan Item of Jilin Provincial Education Department (grant number JT53101022010), and the Doctoral Research Start-up Fund of Jilin Medical University (grant numbers JYBS2021014LK and 2022JYBS006KJ). The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as potential conflicts of interest.

Cell Surface Modification-Mediated Primary Intestinal Epithelial Cell Culture Platforms for Assessing Host-Microbiota Interactions

Background: Intestinal epithelial cells (IECs) play a crucial role in regulating the symbiotic relationship between the host and the gut microbiota, thereby allowing them to modulate barrier function, mucus production, and aberrant inflammation. Despite their importance, establishing an effective ex vivo culture method for supporting the prolonged survival and function of primary IECs remains challenging. Here, we aim to develop a novel strategy to support the long-term survival and function of primary IECs in response to gut microbiota by employing mild reduction of disulfides on the IEC surface proteins with tris(2-carboxyethyl)phosphine. Methods: Recognizing the crucial role of fibroblast-IEC crosstalk, we employed a cell surface modification strategy, establishing layer-to-layer contacts between fibroblasts and IECs. This involved combining negatively charged chondroitin sulfate on cell surfaces with a positively charged chitosan thin film between cells, enabling direct intercellular transfer. Validation included assessments of cell viability, efficiency of dye transfer, and IEC function upon lipopolysaccharide (LPS) treatment. Results: Our findings revealed that the layer-by-layer co-culture platform effectively facilitates the transfer of small molecules through gap junctions, providing vital support for the viability and function of primary IECs from both the small intestine and colon for up to 5 days, as evident by the expression of E-cadherin and Villin. Upon LPS treatment, these IECs exhibited a down-regulation of Villin and tight junction genes, such as E-cadherin and Zonula Occludens-1, when compared to their nontreated counterparts. Furthermore, the transcription level of Lysozyme exhibited an increase, while Mucin 2 showed a decrease in response to LPS, indicating responsiveness to bacterial molecules. Conclusions: Our study provides a layer-by-layer-based co-culture platform to support the prolonged survival of primary IECs and their features, which is important for understanding IEC function in response to the gut microbiota.

Multicellular Layered Nanofibrous Poly(Oligo Ethylene Glycol Methacrylate) (POEGMA)-Based Hydrogel Scaffolds via Reactive Cell Electrospinning

While hydrogels are demonstrated to be effective scaffolds for soft tissue engineering, existing fabrication techniques pose limitations in terms of being able to reproduce both the micro/nanofibrous structures of native extracellular matrix as well as the spatial arrangement of different cell types inherent of more complex tissues. Herein, a reactive cell electrospinning strategy is described using hydrazide and aldehyde-functionalized poly(oligoethylene glycol methacrylate) precursor polymers that can create nanofibrous hydrogel scaffolds with controllable local cell gradients using a sequential all-aqueous process that does not require additives or external energy. Cells can be encapsulated directly during the fabrication process in different layers within the scaffold, enabling localized segregation of different cell types within the structures without compromising their capacity to proliferate (≈4-fold increase in cell density over a 14 day incubation period). This sequential reactive electrospinning approach thus offers promise to generate coculture fibrous hydrogel networks in which both the nanoscale architecture and the cell distribution can be controlled, as it is essential to recreate more complex types of tissues.

Pituitary Remodeling Throughout Life: Are Resident Stem Cells Involved?

The pituitary gland has the primordial ability to dynamically adapt its cell composition to changing hormonal needs of the organism throughout life. During the first weeks after birth, an impressive growth and maturation phase is occurring in the gland during which the distinct hormonal cell populations expand. During pubertal growth and development, growth hormone (GH) levels need to peak which requires an adaptive enterprise in the GH-producing somatotrope population. At aging, pituitary function wanes which is associated with organismal decay including the somatopause in which GH levels drop. In addition to these key time points of life, the pituitary's endocrine cell landscape plastically adapts during specific (patho-)physiological conditions such as lactation (need for PRL) and stress (engagement of ACTH). Particular resilience is witnessed after physical injury in the (murine) gland, culminating in regeneration of destroyed cell populations. In many other tissues, adaptive and regenerative processes involve the local stem cells. Over the last 15 years, evidence has accumulated that the pituitary gland houses a resident stem cell compartment. Recent studies propose their involvement in at least some of the cell remodeling processes that occur in the postnatal pituitary but support is still fragmentary and not unequivocal. Many questions remain unsolved such as whether the stem cells are key players in the vivid neonatal growth phase and whether the decline in pituitary function at old age is associated with decreased stem cell fitness. Furthermore, the underlying molecular mechanisms of pituitary plasticity, in particular the stem cell-linked ones, are still largely unknown. Pituitary research heavily relies on transgenic in vivo mouse models. While having proven their value, answers to pituitary stem cell-focused questions may more diligently come from a novel powerful in vitro research model, termed organoids, which grow from pituitary stem cells and recapitulate stem cell phenotype and activation status. In this review, we describe pituitary plasticity conditions and summarize what is known on the involvement and phenotype of pituitary stem cells during these pituitary remodeling events.

The therapeutic effects and underlying mechanisms of the intrauterine perfusion of granulocyte colony-stimulating factor on a thin-endometrium rat model

AIMS

This study aims to investigate the effects of intrauterine perfusion of granulocyte colony-stimulating factor (G-CSF) on a thin-endometrium rat model.

MAIN METHODS

Twenty rats in two groups of 10 were used. Group I was perfused with normal saline (NS) in the right uterine horn and 95% ethanol in the left one. Group II was bilaterally perfused with 95% ethanol into the uterine horns. After three estrous cycles, Group II was perfused with NS in the right uterine horn and G-CSF (30 μg/kg) in the left one. Hematoxylin-eosin (HE) and immunohistochemistry (IHC) staining were used to detect changes in endometrial thickness and expression of cytokeratin 19 (CK19) and vimentin (Vim). The relative expression levels of vascular endothelial growth factor (Vegf) and leukemia inhibitory factor (Lif) were also tested via reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) and Western-blot analyses.

KEY FINDINGS

G-CSF treatment significantly increased the thickness of the endometrium in the 95% ethanol-induced thin-endometrium rat model. The expression levels of endometrial glandular epithelial cell marker for CK19 and stromal cell marker Vim were augmented in the G-CSF-treated group compared with the control group. Moreover, G-CSF treatment stimulated the expression of VEGF and LIF in the 95% ethanol-induced thin-endometrium rat model.

SIGNIFICANCE

G-CSF intrauterine perfusion improved endometrial receptivity in the thin-endometrium rat model by stimulating endometrial proliferation and angiogenesis.

Repair and regeneration of small intestine: A review of current engineering approaches

The small intestine (SI) is difficult to regenerate or reconstruct due to its complex structure and functions. Recent developments in stem cell research, advanced engineering technologies, and regenerative medicine strategies bring new hope of solving clinical problems of the SI. This review will first summarize the structure, function, development, cell types, and matrix components of the SI. Then, the major cell sources for SI regeneration are introduced, and state-of-the-art biofabrication technologies for generating engineered SI tissues or models are overviewed. Furthermore, in vitro models and in vivo transplantation, based on intestinal organoids and tissue engineering, are highlighted. Finally, current challenges and future perspectives are discussed to help direct future applications for SI repair and regeneration.

Influence of Nitrogen Levels on Nutrient Transporters and Regulators of Protein Synthesis in Small Intestinal Enterocytes of Piglets

To investigate effects of dietary nitrogen level on nutrient absorption and utilization in small intestinal enterocyte of piglets, weaned piglets were fed for 10 days with diets containing 20%, 17%, or 14% crude protein (CP) with supplementation to meet requirements for essential amino acids in vivo, and IPEC-1 cells were cultured with different nitrogen levels (NL) in a culture medium (70%, 85%, and 100%) in vitro by monocultured and cocultured intestinal porcine epithelial cells (IPEC-1) and human gastric epithelial cells (GES-1). The results showed the following: (1) In animal trial, decreased dietary CP reduced transcript abundance of nutrient transporters like CAT1, PepT1, GLUT2, and SGLT-1 in jejunal mucosa (0.09 ± 0.03, P < 0.0001; 0.40 ± 0.04, P = 0.0087; 0.20 ± 0.07, P = 0.0003; 0.35 ± 0.02, P = 0.0001), but 17% CP diet did not affect jejunal protein synthesis. (2) The transcript abundance of nutrient transporters displayed similarly effective tendency in jejunal mucosa and cocultured IPEC-1 rather than that in monocultured IPEC-1. (3) Decreased nitrogen levels reduced expressive abundance of PI3K, Class 3 PI3K, TSC2, and 4E-BP1 in monocultured IPEC-1, but 85% nitrogen level did not affect expressive abundance of PI3K, TSC2, mTORC1, 4E-BP1, and S6K1 in cocultured IPEC-1. In general, decreased 3% CP or 15% nitrogen level reduced relative transcript expression of nutrient transporters, but did not affect protein synthesis in jejunal mucosa and cocultured IPEC-1. Therefore, decreased 3% dietary CP increased utilized and synthetic efficiency of nitrogen resource in small intestine and was beneficial in saving the dietary nitrogen resource.

Comparison of polyglycolic acid, polycaprolactone, and collagen as scaffolds for the production of tissue engineered intestine

Cell-seeded scaffolds play critical roles in the production of tissue engineered intestine (TEI), a potential strategy for the treatment of short bowel syndrome. The current study compares polyglycolic acid (PGA), polycaprolactone (PCL), and collagen as scaffolds for TEI production. Tubular PGA scaffolds were prepared from nonwoven BIOFELT^® . Tubular PCL scaffolds were fabricated by electrospinning. Tubular collagen scaffolds were prepared using CollaTape, a wound dressing material. Both PGA and collagen were coated with poly-l-lactic acid (PLLA) to improve scaffold mechanical properties. Pore size, porosity, microstructure, mechanical properties (suture retention strength and ultimate compressive force) were determined. The scaffolds were first seeded with crypt stem cells isolated from 1 to 3 day old rat pups and then implanted into the peritoneal cavity of nude rats. After 4 weeks of in vivo incubation, these cell-seeded scaffolds were harvested for assessment of the TEI produced. Of the three materials compared, PLLA coated tubular PGA scaffolds had the appropriate pore size, mechanical properties and degradation rate leading to the production of TEI with an architecture similar to that of native rat intestine. © 2018 Wiley Periodicals, Inc. J. Biomed. Mater. Res. Part B, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 750-760, 2019.

Comparison of conventional and advanced in vitro models in the toxicity testing of nanoparticles

Humans are exposed to a wide variety of nanoparticles (NPs) present in the environment, in consumer, health and medical products, and in food. Conventional cytotoxicity testing compared to animal testing is less expensive, faster and avoids ethical problems at the expense of a lower predictive value. New cellular models and exposure conditions have been developed to overcome the limitations of conventional cell culture and obtain more predictive data. The use of three-dimensional culture, co-culture and inclusion of mechanical stimulation can provide physiologically more relevant culture conditions. These systems are particularly relevant for oral, respiratory and intravenous exposure to NPs and it may be assumed that physiologically relevant application of the NPs can improve the predictive value of in vitro testing. Various groups have used advanced culture and exposure systems, but few direct comparisons between data from conventional cultures and from advanced systems exist. In silico models may present another option to predict human health risk by NPs without using animal studies. In the absence of validation, the question whether these alternative models provide more predictive data than conventional testing remains elusive.

Use of hydrogel scaffolds to develop an in vitro 3D culture model of human intestinal epithelium

The human intestinal cell lines: Caco-2 and HT29-MTX cells have been used extensively in 2D and 3D cell cultures as simple models of the small intestinal epithelium in vitro. This study aimed to investigate the potential of three hydrogel scaffolds to support the 3D culture of Caco-2 and HT29-MTX cells and critically assess their use as scaffolds to stimulate villi formation to model a small intestinal epithelium in vitro. Here, alginate, l-pNIPAM, and l-pNIPAM-co-DMAc hydrogels were investigated. The cells were suspended within or layered on these hydrogels and maintained under static or dynamic culture conditions for up to 21days. Caco-2 cell viability was increased when layered on the synthetic hydrogel scaffolds, but reduced when suspended within the synthetic hydrogels. In contrast, HT29-MTX cells remained viable when suspended within or layered on all 3D cultures. Interestingly, cells cultured in and on the alginate hydrogel scaffolds formed multilayer spheroid structures, whilst the cells layered on synthetic hydrogels formed villus-like structures. Immunohistochemistry staining demonstrated positive expression of enterocyte differentiation markers and goblet cell marker. In conclusion, l-pNIPAM hydrogel scaffolds supported both cell lines and induced formation of villus-like structures when cells were layered on and cultured under dynamic conditions. The ability of the l-pNIPAM to recapitulate the 3D structure and differentiate main cell types of human intestinal villi may deliver a potential alternative in vitro model for studying intestinal disease and for drug testing.

STATEMENT OF SIGNIFICANCE

Forty percent of hospital referrals are linked to disorders of the digestive tract. Current studies have utilised animal models or simple cultures of isolated cells which do not behave in the same manner as human intestine. Thus new models are required which more closely mimic the behaviour of intestinal cells. Here, we tested a number of scaffolds and conditions to develop a cell culture model which closely represents the 3D environment seen within the human small intestine. We successfully created structures seen within the intestine which have not previously been possible with other culture models. These models could be used to investigate tissue engineering, drug discovery, and used asan alternative to in vivo animal models in drug toxicity studies.

Cell Systems to Investigate the Impact of Polyphenols on Cardiovascular Health

Polyphenols are a diverse group of micronutrients from plant origin that may serve as antioxidants and that contribute to human health in general. More specifically, many research groups have investigated their protective effect against cardiovascular diseases in several animal studies and human trials. Yet, because of the excessive processing of the polyphenol structure by human cells and the residing intestinal microbial community, which results in a large variability between the test subjects, the exact mechanisms of their protective effects are still under investigation. To this end, simplified cell culture systems have been used to decrease the inter-individual variability in mechanistic studies. In this review, we will discuss the different cell culture models that have been used so far for polyphenol research in the context of cardiovascular diseases. We will also review the current trends in cell culture research, including co-culture methodologies. Finally, we will discuss the potential of these advanced models to screen for cardiovascular effects of the large pool of bioactive polyphenols present in foods and their metabolites.

Buckling of a growing tissue and the emergence of two-dimensional patterns

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We model the growth of gut epithelial cells cultured upon a deformable substrate.

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Growth generates buckling instabilities, contributing to crypt formation in vivo.

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Variations in mechanical properties have little effect on resulting configurations.

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Configurations are controlled by growth patterns & interactions with strata below.

The process of biological growth and the associated generation of residual stress has previously been considered as a driving mechanism for tissue buckling and pattern selection in numerous areas of biology. Here, we develop a two-dimensional thin plate theory to simulate the growth of cultured intestinal epithelial cells on a deformable substrate, with the goal of elucidating how a tissue engineer might best recreate the regular array of invaginations (crypts of Lieberkühn) found in the wall of the mammalian intestine. We extend the standard von Kármán equations to incorporate inhomogeneity in the plate’s mechanical properties and surface stresses applied to the substrate by cell proliferation. We determine numerically the configurations of a homogeneous plate under uniform cell growth, and show how tethering to an underlying elastic foundation can be used to promote higher-order buckled configurations. We then examine the independent effects of localised softening of the substrate and spatial patterning of cellular growth, demonstrating that (within a two-dimensional framework, and contrary to the predictions of one-dimensional models) growth patterning constitutes a more viable mechanism for control of crypt distribution than does material inhomogeneity.

Are synthetic scaffolds suitable for the development of clinical tissue-engineered tubular organs?

Transplantation of tissues and organs is currently the only available treatment for patients with end-stage diseases. However, its feasibility is limited by the chronic shortage of suitable donors, the need for life-long immunosuppression, and by socioeconomical and religious concerns. Recently, tissue engineering has garnered interest as a means to generate cell-seeded three-dimensional scaffolds that could replace diseased organs without requiring immunosuppression. Using a regenerative approach, scaffolds made by synthetic, nonimmunogenic, and biocompatible materials have been developed and successfully clinically implanted. This strategy, based on a viable and ready-to-use bioengineered scaffold, able to promote novel tissue formation, favoring cell adhesion and proliferation, could become a reliable alternative to allotransplatation in the next future. In this article, tissue-engineered synthetic substitutes for tubular organs (such as trachea, esophagus, bile ducts, and bowel) are reviewed, including a discussion on their morphological and functional properties.