Reconstruction of functional uterine tissues through recellularizing the decellularized rat uterine scaffolds by MSCs in vivo and in vitro

Standardizing decellularization protocols for optimized uterine tissue bioengineering

Bioengineering is applied in different areas, including women's infertility management. Among other approaches, decellularized tissues are being used to treat uterine disorders causing infertility. Biomaterials made from decellularized tissue consist of tissue-specific extracellular matrix and, as acellular scaffolds, are thought to be immune inert. Hence, they are good grafting candidates to replace and regenerate excised damaged uterine tissue to cure infertility. However, decellularization approaches differ among species and research groups, posing challenges for comparison and standardization. The diversity in data reporting and studied properties of the resulting decellularized scaffold make it even more difficult, especially when the ultimate goal is clinical translation. Thus, this review aims to critically assess whole uterus decellularization studies, extracting and comparing their main results and conclusions. After carefully evaluating the reviewed studies, we noticed that the vast majority base the uterus decellularization success and resulting scaffold efficacy on the DNA removal efficacy, while other crucial aspects, including the extracellular matrix integrity or immunogenicity, are underestimated. Thus, this review further proposes practical points for what should be considered and how results can be reported in studies involving whole uterus decellularization to facilitate comparison between studies and translational progress.

Advances in Nanomedicine and Biomaterials for Endometrial Regeneration: A Comprehensive Review

The endometrium is an extremely important component of the uterus and is crucial for individual health and human reproduction. However, traditional methods still struggle to ideally repair the structure and function of damaged endometrium and restore fertility. Therefore, seeking and developing innovative technologies and materials has the potential to repair and regenerate damaged or diseased endometrium. The emergence and functionalization of various nanomedicine and biomaterials, as well as the proposal and development of regenerative medicine and tissue engineering techniques, have brought great hope for solving these problems. In this review, we will summarize various nanomedicine, biomaterials, and innovative technologies that contribute to endometrial regeneration, including nanoscale exosomes, nanomaterials, stem cell-based materials, naturally sourced biomaterials, chemically synthesized biomaterials, approaches and methods for functionalizing biomaterials, as well as the application of revolutionary new technologies such as organoids, organ-on-chips, artificial intelligence, etc. The diverse design and modification of new biomaterials endow them with new functionalities, such as microstructure or nanostructure, mechanical properties, biological functions, and cellular microenvironment regulation. It will provide new options for the regeneration of endometrium, bring new hope for the reconstruction and recovery of patients' reproductive abilities.

Transplantation of a bioengineered tissue patch promotes uterine repair in the sheep

Innovative bioengineering strategies utilizing extracellular matrix (ECM) based scaffolds derived from decellularized tissue offer new prospects for restoring damaged uterine tissue. Despite successful fertility restoration in small animal models, the translation to larger and more clinically relevant models have not yet been assessed. Thus, our study investigated the feasibility to use a 6 cm2 graft constructed from decellularized sheep uterine tissue, mimicking a future application to repair a uterine defect in women. Some grafts were also recellularized with fetal sheep bone marrow-derived mesenchymal stem cells (SF-MSCs). The animals were followed for six weeks post-surgery during which blood samples were collected to assess the systemic immune cell activation by fluorescence-activated cell sorting (FACS) analysis. Tissue regeneration was assessed by histology, immunohistochemistry, and gene expression analyses. There was a large intra-group variance which prompted us to implement a novel scoring system to comprehensively evaluate the regenerative outcomes. Based on the regenerative score each graft received, we focused our analysis to map potential differences that may have played a role in the success or failure of tissue repair following the transplantation therapy. Notably, three out of 15 grafts exhibited major regeneration that resembled native uterine tissue, and an additional three grafts showed substantial regenerative outcomes. For the better regenerated grafts, it was observed that the systemic T-cell subgroups were significantly different compared with the failing grafts. Hence, our data suggest that the T-cell response play an important role for determining the uterus tissue regeneration outcomes. The remarkable regeneration seen in the best-performing grafts after just six weeks following transplantation provides compelling evidence that decellularized tissue for uterine bioengineering holds great promise for clinically relevant applications.

Optimizing Decellularization of Bovine Ovarian Tissue: Toward a Transplantable Artificial Ovary Scaffold with Minimized Residual Toxicity and Preserved Extracellular Matrix Morphology

INTRODUCTION

The decellularized extracellular matrix (dECM) from ovarian tissue could be the best scaffold for the development of a transplantable artificial ovary. Typically, dECM from ovarian tissue has been obtained using sodium dodecyl sulfate (SDS), at a concentration of 1% for 24 h. However, SDS can leave residues in the tissue, which may be toxic to the seeded cells. This study aimed to obtain dECM from bovine ovarian tissue using SDS and NaOH at a minimum concentration in the shortest incubation time.

METHODS

The respective SDS and NaOH concentrations investigated were 1% and 0.2 m; 0.5% and 0.1 m; 0.1% and 0.02 m; and 0.05% and 0.01 m, with 24-, 12-, and 6-h incubation periods. After the incubation time, the tissue was washed in 50 mL of distilled water for 6 h.

RESULTS

Histological analysis confirmed decellularization and showed the conservation of collagen fibers in all samples following treatment. Furthermore, the lowest SDS and NaOH concentrations that showed no DNA remaining during electrophoresis analysis were 0.1% and 0.02 m when incubated for 24 and 12 h. DNA quantification resulted in <0.2 ng DNA/mg ovarian tissue using these protocols. Additionally, the coculture of dECM (obtained by 0.1% SDS and 0.02 m NaOH for 12 h) with ovarian cells showed that there was no toxic effect for the cells for up to 72 h.

CONCLUSION

The protocol involving 0.1% SDS and 0.02 m NaOH for 12-h incubation decellularizes bovine ovarian tissue, generating a dECM that preserves the native ECM morphology and is nontoxic to ovarian cells.

Decellularized extracellular matrix for organoid and engineered organ culture

The repair and regeneration of tissues and organs using engineered biomaterials has attracted great interest in tissue engineering and regenerative medicine. Recent advances in organoids and engineered organs technologies have enabled scientists to generate 3D tissue that recapitulate the structural and functional characteristics of native organs, opening up new avenues in regenerative medicine. The matrix is one of the most important aspects for improving organoids and engineered organs construction. However, the clinical application of these techniques remained a big challenge because current commercial matrix does not represent the complexity of native microenvironment, thereby limiting the optimal regenerative capacity. Decellularized extracellular matrix (dECM) is expected to maintain key native matrix biomolecules and is believed to hold enormous potential for regenerative medicine applications. Thus, it is worth investigating whether the dECM can be used as matrix for improving organoid and engineered organs construction. In this review, the characteristics of dECM and its preparation method were summarized. In addition, the present review highlights the applications of dECM in the fabrication of organoids and engineered organs.

Polydopamine-modified decellularized intestinal scaffolds loaded with adipose-derived stem cells promote intestinal regeneration

Regeneration of gastrointestinal tissues remains a great challenge due to their unique microenvironment. Functional composite decellularized scaffolds have shown great potential in gastrointestinal repair and inducing gastrointestinal tissue-specific proliferation. In this study, polydopamine (PDA)-mediated surface modification of decellularized intestinal scaffolds (DIS), combined with adipose tissue-derived stem cells (ADSC), was used to promote intestinal wound healing while avoiding intestinal resection. The results showed that DIS had good biocompatibility and could maintain the growth and proliferation of ADSC. Moreover, PDA-coated DIS not only had anti-infection ability but could also further promote the secretory activity for the paracrine effects of ADSC. ADSC cultured on PDA-DIS produced significantly higher levels of anti-inflammatory and proangiogenic cytokines than those cultured on plastic plates or DIS. In vivo, ADSC-PDA-DIS significantly promoted intestinal wound closure in rat intestinal defect models. Moreover, ADSC-PDA-DIS was able to induce more neovascularization at 4 weeks postoperatively and promoted macrophage recruitment to accelerate wound healing. Taken together, the results showed that PDA-modified DIS could significantly improve the efficacy of stem cell therapy, and ADSC-PDA-DIS could improve the wound healing process with anti-infection effects, enhancing neovascularization and immunoregulation, which may be of great clinical significance for gastrointestinal regeneration.

Are we ready for the revision of the 14-day rule? Implications from Chinese legislations guiding human embryo and embryoid research

The ISSCR recently released new guidelines that relaxed the 14-day rule taking away the tough barrier, and this has rekindled relevant ethical controversies and posed a fresh set of challenges to each nation's legislations and policies directly or indirectly. To understand its broad implications and the variation and impact of China's relevant national policies, we reviewed and evaluated Chinese laws, administrative regulations, departmental rules, and normative documents on fundamental and preclinical research involving human embryos from 1985 to 2022 in this paper. We have historically examined whether these regulations, including a 14-day rule, had restrictions on human embryo research, and whether and how these policies affected human embryo and embryoid research in China. We also discussed and assessed the backdrop in which China has endeavored to handle such as the need for expanding debates among justice practice, academia, and the public, and the shifting external environment influenced by fast-developing science and technology and people's culture and religions. In general, Chinese society commonly opposes giving embryos or fetuses the legal status of humans, presumably due to the Chinese public not seeming to have any strong religious beliefs regarding the embryo. On this basis, they do not strongly oppose the potential expansion of the 14-day rule. After the guidelines to strengthen governance over ethics in science, and technology were released by the Chinese government in 2022, Chinese policymakers have incorporated bioethics into the national strategic goals using a "People-Centered" approach to develop and promote an ecological civilization. Specifically, China follows the "precautionary principle" based on ethical priority as it believes that if scientific research carries any potential technological and moral risks on which no social ethical consensus has been attained, there would be a need to impose oversight for prevention and precaution. At the same time, China has adopted a hybrid legislative model of legislation and ethical regulations with criminal, civil and administrative sanctions and a 14-day limit specified within its national hESCs guidelines. This would certainly be a useful example for other countries to use when considering the possibility of developing a comprehensive, credible and sustainable regulatory framework.

Human Endometrium-Derived Adventitial Cell Spheroid-Loaded Antimicrobial Microneedles for Uterine Regeneration

Asherman's syndrome (AS) occurs as a consequence of severe damage to the endometrial basalis, usually leading to menstrual abnormalities, infertility, and recurrent miscarriage in women. Currently, human endometrium-derived adventitial cells (En-ADVs) are considered ideal seed cells with high pluripotency for regenerative medicine. However, critical issues such as noninvasive repair of tissues, targeting of native stem cells, and continuous action in the injured sites are not well resolved. Herein, En-ADV spheroid-loaded hierarchical microneedles (MN/En-ADV) for in situ intrauterine repair are developed. The flexible microneedles are fabricated with gelatin methacryloyl and lactoferrin, imparting the characteristics of rapid degradation and antimicrobial activity. Benefiting from an array of microwells on microneedles, En-ADVs can rapidly form 3D cell spheroids, which display higher potential for cell proliferation, differentiation, and migration than dissociated cells. With the application of MN/En-ADV, the repaired uteri show well-defined myometrial regeneration, angiogenesis, and an increase of endometrial receptivity in a rat AS model. Notably, embryos are able to implant in the reconstructed sites and remain viable, indicating that this system promotes the restoration of both normal morphology and reproductive function in the injured uterus. It is anticipated that multifunctional MN/En-ADV can be an ideal candidate for versatile in situ tissue regeneration.

Future Challenges and Opportunities of Extracellular Matrix Hydrogels in Female Reproductive Medicine

Bioengineering and reproductive medicine have progressed shoulder to shoulder for several decades. A key point of overlap is the development and clinical translation of technologies to support reproductive health, e.g., scaffold-free constructs, polymeric scaffolds, bioprinting or microfluidics, and hydrogels. Hydrogels are the focus of intense study, and those that are derived from the extracellular matrix (ECM) of reproductive tissues and organs are emerging as promising new players given their results in pre-clinical models. This literature review addresses the recent advances in the use of organ-specific ECM hydrogels in reproductive medicine, considering the entire female reproductive tract. We discuss in-depth papers describing the development of ECM hydrogels, their use in in vitro models, and their in vivo application in preclinical studies. We also summarize the functions of hydrogels, including as grafts, carriers for cell transplantation, or drug depots, and present the potential and possible scope for use of ECM hydrogels in the near future based on recent scientific advances.

Involving Animal Models in Uterine Transplantation

Background

Absolute uterine factor infertility affects 0. 2% women of childbearing age around the world. Uterine transplantation (UTx) is a promising solution for many of them since the first birth from UTx was described by the Swedish team in 2014. The success of Utx in humans has become possible after a systematic and meticulous approach involving years of research on animal models. To date, more than 80 UTx procedures have been performed worldwide and 30 children were born.

Material and Method

This review summarizes the research preparation conducted in animals before beginning UTx in humans. It focuses on the advantages and limits of each animal model, their place in surgical training, and current contribution in research to improve UTx successes in humans. The different steps in the process of UTx have been analyzed, such as imaging, surgery, ischemia-reperfusion effects, rejection markers, immunosuppressive treatment, and pregnancy.

Conclusion

Animal models have played an essential role in the implementation of UTx, which is a highly complex procedure. While respecting the 3R requirements (replacement, refinement, and reduction), the surgical training using large animal models, such as notably ewes remain irreplaceable for teams wishing to initiate a UTx program. Furthermore, animal models are still mandatory in current research to improve the success rates of UTx in humans as well as to reduce the morbidity associated with this experimental infertility treatment.

Collagen-based materials in reproductive medicine and engineered reproductive tissues

Collagen, the main component of mammal skin, has been traditionally used in leather manufacturing for thousands of years due to its diverse physicochemical properties. Collagen is the most abundant protein in mammals and the main component of the extracellular matrix (ECM). The properties of collagen also make it an ideal building block for the engineering of materials for a range of biomedical applications. Reproductive medicine, especially human fertility preservation strategies and reproductive organ regeneration, has attracted significant attention in recent years as it is key in resolving the growing social concern over aging populations worldwide. Collagen-based biomaterials such as collagen hydrogels, decellularized ECM (dECM), and bioengineering techniques including collagen-based 3D bioprinting have facilitated the engineering of reproductive tissues. This review summarizes the recent progress in applying collagen-based biomaterials in reproductive. Furthermore, we discuss the prospects of collagen-based materials for engineering artificial reproductive tissues, hormone replacement therapy, and reproductive organ reconstruction, aiming to inspire new thoughts and advancements in engineered reproductive tissues research.

Graphical abstract

Mesenchymal stem cells establish a pro-regenerative immune milieu after decellularized rat uterus tissue transplantation

Decellularized tissue is generally considered immune privileged after transplantation and is an attractive scaffold type for tissue regeneration, including applications for infertility treatment. However, the immune response following transplantation of decellularized tissue is insufficiently studied, in particular after they have been recellularized with mesenchymal stem cells (MSCs). Therefore, we replaced a large uterus segment with a bioengineered graft developed from decellularized uterus tissue and analyzed the immune response during the first 4 months in acellular or MSCs-recellularized scaffolds in the rat. Immunohistochemistry-stained infiltrating immune cells and plasma levels for 16 cytokines and chemokines were quantified. Results revealed that MSCs created an advantageous microenvironment by increasing anti-inflammatory interleukin 10 levels, and increasing the population of FOXP3⁺ T_Regs and CD163⁺ M2 macrophages, and by reducing the CD8⁺ cytotoxic T cell population. Hence, MSCs should be considered an immunotherapeutic cell source with the ability to dictate regeneration success after decellularized tissue transplantation.

OUP accepted manuscript

BACKGROUND

To provide the optimal milieu for implantation and fetal development, the female reproductive system must orchestrate uterine dynamics with the appropriate hormones produced by the ovaries. Mature oocytes may be fertilized in the fallopian tubes, and the resulting zygote is transported toward the uterus, where it can implant and continue developing. The cervix acts as a physical barrier to protect the fetus throughout pregnancy, and the vagina acts as a birth canal (involving uterine and cervix mechanisms) and facilitates copulation. Fertility can be compromised by pathologies that affect any of these organs or processes, and therefore, being able to accurately model them or restore their function is of paramount importance in applied and translational research. However, innate differences in human and animal model reproductive tracts, and the static nature of 2D cell/tissue culture techniques, necessitate continued research and development of dynamic and more complex in vitro platforms, ex vivo approaches and in vivo therapies to study and support reproductive biology. To meet this need, bioengineering is propelling the research on female reproduction into a new dimension through a wide range of potential applications and preclinical models, and the burgeoning number and variety of studies makes for a rapidly changing state of the field.

OBJECTIVE AND RATIONALE

This review aims to summarize the mounting evidence on bioengineering strategies, platforms and therapies currently available and under development in the context of female reproductive medicine, in order to further understand female reproductive biology and provide new options for fertility restoration. Specifically, techniques used in, or for, the uterus (endometrium and myometrium), ovary, fallopian tubes, cervix and vagina will be discussed.

SEARCH METHODS

A systematic search of full-text articles available in PubMed and Embase databases was conducted to identify relevant studies published between January 2000 and September 2021. The search terms included: bioengineering, reproduction, artificial, biomaterial, microfluidic, bioprinting, organoid, hydrogel, scaffold, uterus, endometrium, ovary, fallopian tubes, oviduct, cervix, vagina, endometriosis, adenomyosis, uterine fibroids, chlamydia, Asherman’s syndrome, intrauterine adhesions, uterine polyps, polycystic ovary syndrome and primary ovarian insufficiency. Additional studies were identified by manually searching the references of the selected articles and of complementary reviews. Eligibility criteria included original, rigorous and accessible peer-reviewed work, published in English, on female reproductive bioengineering techniques in preclinical (in vitro/in vivo/ex vivo) and/or clinical testing phases.

OUTCOMES

Out of the 10 390 records identified, 312 studies were included for systematic review. Owing to inconsistencies in the study measurements and designs, the findings were assessed qualitatively rather than by meta-analysis. Hydrogels and scaffolds were commonly applied in various bioengineering-related studies of the female reproductive tract. Emerging technologies, such as organoids and bioprinting, offered personalized diagnoses and alternative treatment options, respectively. Promising microfluidic systems combining various bioengineering approaches have also shown translational value.

WIDER IMPLICATIONS

The complexity of the molecular, endocrine and tissue-level interactions regulating female reproduction present challenges for bioengineering approaches to replace female reproductive organs. However, interdisciplinary work is providing valuable insight into the physicochemical properties necessary for reproductive biological processes to occur. Defining the landscape of reproductive bioengineering technologies currently available and under development for women can provide alternative models for toxicology/drug testing, ex vivo fertility options, clinical therapies and a basis for future organ regeneration studies.

Functional survey of decellularized tissues transplantation for infertile females

Numbers of women worldwide face infertility, which will have a significant impact on a couple's life. As a result, assisting with the treatment of these individuals is seen as a critical step. Successful births following uterus and ovary donation have been reported in recent. When immunosuppressive drugs are used in patients who receive donated tissues, there are always problems with the drugs' side effects. In recent years, tissue engineering has mainly been successful in treating infertility using decellularization techniques. Engineered uterus and ovary prevent immunological reactions and do not require immunosuppressive drugs. The most important aspect of using decellularized tissue is its proper function after transplantation. These tissues must be able to produce follicles, secrete hormones and cause pregnancy. This study aimed to investigate research on decellularized tissues and transplanted into the female reproductive system. In this study, just tissues that, after transplantation, have the proper function for fertility were investigated.

Bioengineered endometrial hydrogels with growth factors promote tissue regeneration and restore fertility in murine models

Extracellular matrix (ECM) hydrogels obtained from decellularized tissues are promising biocompatible materials for tissue regeneration. These biomaterials may provide important options for endometrial pathologies such as Asherman's syndrome and endometrial atrophy, which lack effective therapies thus far. First, we performed a proteomic analysis of a decellularized endometrial porcine hydrogel (EndoECM) to describe the specific role of ECM proteins related to regenerative processes. Furthermore, we investigated the ability of a bioengineered system-EndoECM alone or supplemented with growth factors (GFs)-to repair the endometrium in a murine model of endometrial damage. For this model, the uterine horns of female C57BL/6 mice were first injected with 70% ethanol, then four days later, they were treated with: saline (negative control); biotin-labeled EndoECM; or biotin-labeled EndoECM plus platelet-derived GF, basic fibroblast GF, and insulin-like GF 1 (EndoECM+GF). Endometrial regeneration and fertility restoration were evaluated by assessing the number of glands, endometrial area, cell proliferation, neaoangiogenesis, reduction of collagen deposition, and fertility restoration. Interestingly, regenerative effects such as an increased number of endometrial glands, increased area, high cell proliferative index, development of new blood vessels, reduction of collagen deposition, and higher pregnancy rate occurred in mice treated with EndoECM+GF. Thus, a bioengineered system based on EndoECM hydrogel supplemented with GFs may be promising for the clinical treatment of endometrial conditions such as Asherman's syndrome and endometrial atrophy. STATEMENT OF SIGNIFICANCE: In the last years, the bioengineering field has developed new and promising approaches to regenerate tissues or replace damaged and diseased tissues. Bioengineered hydrogels offer an ideal option because these materials can be used not only as treatments but also as carriers of drugs and other therapeutics. The present work demonstrates for the first time how hydrogels derived from pig endometrium loaded with growth factors could treat uterine pathologies in a mouse model of endometrial damage. These findings provide scientific evidence about bioengineered hydrogels based on tissue-specific extracellular matrix offering new options to treat human infertility from endometrial causes such as Asherman's syndrome or endometrial atrophy.

Uterine Tissue Engineering: Where We Stand and the Challenges Ahead

Tissue engineering is an innovative approach to develop allogeneic tissues and organs. The uterus is a very sensitive and complex organ, which requires refined techniques to properly regenerate and even, to rebuild itself. Many therapies were developed in 20th century to solve reproductive issues related to uterus failure and, more recently, tissue engineering techniques provided a significant evolution in this issue. Herein we aim to provide a broad overview and highlights of the general concepts involved in bioengineering to reconstruct the uterus and its tissues, focusing on strategies for tissue repair, production of uterine scaffolds, biomaterials and reproductive animal models, highlighting the most recent and effective tissue engineering protocols in literature and their application in regenerative medicine. In addition, we provide a discussion about what was achieved in uterine tissue engineering, the main limitations, the challenges to overcome and future perspectives in this research field.