3D Bioprinting a human iPSC-derived MSC-loaded scaffold for repair of the uterine endometrium

3D bioprinting technology innovation in female reproductive system

Several diseases affect the female reproductive system, and both disease factors and treatments impact its integrity and function. Consequently, understanding the mechanisms of disease occurrence and exploring treatment methods are key research focuses in obstetrics and gynecology. However, constructing accurate disease models requires a microenvironment closely resembling the human body, and current animal models and 2D in vitro cell models fall short in this regard. Thus, innovative in vitro female reproductive system models are urgently needed. Additionally, female reproductive system diseases often cause tissue loss, yet effective tissue repair and regeneration have long been a bottleneck in the medical field. 3D bioprinting offers a solution by enabling the construction of implants with tissue repair and regeneration capabilities, promoting cell adhesion, extension, and proliferation. This helps maintain the long-term efficacy of bioactive implants and achieves both structural and functional repair of the reproductive system. By combining live cells with biomaterials, 3D bioprinting can create in vitro 3D biomimetic cellular models, facilitating in-depth studies of cell-cell and cell-extracellular microenvironment interactions, which enhances our understanding of reproductive system diseases and supports disease-specific drug screening. This article reviews 3D bioprinting methods and materials applicable to the female reproductive system, discussing their advantages and limitations to aid in selecting optimal 3D bioprinting strategies. We also summarize and critically evaluate recent advancements in 3D bioprinting applications for tissue regeneration and in vitro disease models and address the prospects and challenges for translating 3D bioprinting technology into clinical applications within the female reproductive system.

The application of tissue engineering strategies for uterine regeneration

Uterine injuries, particularly damages to endometrium, are usually associated with abnormal menstruation, recurrent miscarriage, pregnancy complications, and infertility. Tissue engineering using cell-based, biomolecule-based, or biomaterial and scaffold-based strategies has emerged as a novel and promising approach for uterine regeneration. Stem cells, biomolecules, and porous scaffolds used alone or, very often, used in combination as a more effective treatment means have shown great potential in promoting uterine regeneration. The reported preclinical studies have indicated that appropriate tissue engineering strategies could safely and effectively reconstruct not only endometrium but also partial or even the whole uterine structure. However, the progress in the uterine regeneration area is slow in comparison to that of regenerating many other body tissues and hence it still remains a great challenge to apply uterine tissue engineering for clinical applications. In this review, conventional treatments for uterine-related diseases are briefly reviewed and discussed first. Subsequently, tissue engineering strategies (cell-based, biomolecule-based, biomaterial and scaffold-based, or their combinations) for uterine repair in preclinical studies and clinical trials are presented and analyzed. Finally, the challenges and perspectives in uterine regeneration are pointed and discussed. Despite various limitations and obstacles, the tissue engineering approach is viable and holds high promise for uterine regeneration.

Induced Mesenchymal Stem Cells: An Emerging Source for Regenerative Medicine Applications

Regenerative medicine is gaining interest in the medical field due to the limitations of conventional treatments, which often fail to address the underlying cause of disease. In recent years, stem cell-based therapies have evolved as a promising alternative approach to treat those diseases that cannot be cured using conventional medicine. Adult stem cells, particularly the mesenchymal stem cells (MSCs), have attracted a lot of attention due to their ability to regenerate and repair human tissues and organs. MSCs isolated from adult tissues are well characterized and are currently the most common type of cells for use in regenerative medicine. However, their low number in adult donor tissues, donor-age and cell-source related heterogeneity, limited proliferative and differentiation potential, and early senescence in in vitro cultures, negatively affect MSC regenerative potential. These factors restrict MSC use for research as well as for clinical applications. To overcome these problems, MSCs with superior regenerative potential are required. Induced MSCs (iMSCs) are obtained from induced pluripotent stem cells (iPSCs). These cells are patient-specific, readily available, and have relatively superior regenerative potential and, therefore, can overcome the problems associated with the use of primary MSCs. In this review, the authors aim to discuss the characteristics, regenerative potential, and limitations of MSCs for regenerative medicine applications. The main methods to generate iMSCs from iPSCs have been discussed in detail. In addition, the proposed criteria for their molecular characterization, applications of iMSCs for disease modeling and drug discovery, as well as potential use in regenerative medicine have been explored in detail.

Developing and characterising bovine decellularized extracellular matrix hydrogels to biofabricate female reproductive tissues

This study investigated the development and characterization of decellularized extracellular matrix (dECM) hydrogels tailored for the biofabrication of female reproductive tissues, specifically targeting ovarian cortex, endometrium, ovarian medulla, and oviduct tissues. We aimed to evaluate the cytocompatibility, biomechanical properties, and overall efficacy of these dECMs in promoting cell viability, proliferation, and morphology using the bovine model. Bovine species provide a valuable model due to their accessibility from slaughterhouse tissues, offering a practical alternative to human samples, which are often limited in availability. Additionally, bovine tissue closely mirrors certain physiological and biological characteristics of humans, making it a relevant model for translational research. Our findings revealed that these dECMs exhibited high biocompatibility with embryo development and cell viability, supporting micro vascularization and cellular morphology without the need for external growth factors. It is important to note that the addition of alginate was crucial for maintaining the structural integrity of the hydrogel during long-term cultures. These hydrogels displayed biomechanical properties that closely mimicked native tissues, which was vital for maintaining their functional integrity and supporting cellular activities. The printability assessments showed that dECMs, particularly those from cortex tissues, achieved high precision in replicating the intended structures, though challenges such as low porosity remained. The bioprinted constructs demonstrated robust cell growth, with over 97% viability observed by day 7, indicating their suitability for cell culture. This work represented a significant advancement in reproductive tissue biofabrication, demonstrating the potential of dECM-based hydrogels in creating structurally and viable tissue constructs. By tailoring each dECM to match the unique biomechanical properties of different tissues, we paved the way for more effective and reliable applications in reproductive medicine and tissue engineering. STATEMENT OF SIGNIFICANCE: This research explores the use of decellularized extracellular matrix (dECM) hydrogels as bio-inks for creating reproductive tissues. Ovarian cortex and medulla, oviduct and endometrium dECMs demonstrated biomechanical properties that mimicked native tissues, which is essential for maintaining functional integrity and supporting cellular processes. Notably, these hydrogels exhibited high biocompatibility with embryo development and cell viability, promoting microvascularization and cell differentiation without the need for supplemental growth factors. The successful bioprinting of these bio-inks underscores their potential for creating more complex models. This work represents a significant advancement in tissue engineering, offering promising new avenues for reproductive medicine.

Infertility treatment using polysaccharides-based hydrogels: new strategies in tissue engineering and regenerative medicine

Infertility is a primary health issue affecting about 15% of couples of reproductive ages worldwide, leading to physical, mental, and social challenges. Advances in nanobiotechnology and regenerative medicine are opening new therapeutic horizons for infertility by developing polysaccharide-based nanostructured biomaterials. This review explores the role of tissue engineering and regenerative medicine in infertility treatment, explicitly focusing on the promising potential of polysaccharide-based hydrogels. In this context, using these biomaterials offers unique advantages, including biodegradability, biocompatibility, and the ability to mimic the natural endometrial microenvironment, making them highly effective for applications in endometrial regeneration, ovarian tissue engineering, spermatogenesis support, and controlled drug delivery. This review discusses the various properties and uses of polysaccharide-based hydrogels, like alginate, hyaluronic acid, and chitosan, in helping to restore reproductive function. While these materials hold great promise, some notable challenges to their clinical use include issues like rapid degradation, mechanical instability, and potential immune reactions. Future research should focus on developing hybrid hydrogels, investigating advanced fabrication techniques, and testing these materials in clinical settings. By combining findings from recent studies, this review aims to provide a solid foundation for researchers and clinicians looking to discover new and effective strategies for treating infertility, ultimately connecting research efforts with practical applications in healthcare.

Advances in biomaterials-based tissue engineering for regeneration of female reproductive tissues

The anatomical components of the female reproductive system-comprising the ovaries, uterus, cervix, vagina, and fallopian tubes-interact intricately to provide the structural and hormonal support essential for reproduction. However, this system is susceptible to various detrimental factors, both congenital and acquired, that can impair fertility and adversely affect quality of life. Recent advances in bioengineering have led to the development of sophisticated three-dimensional models that mimic the complex architecture and functionality of reproductive organs. These models, incorporating diverse cell types and tissue layers, are crucial for understanding physiological processes within the reproductive tract. They offer insights into decidualization, ovulation, folliculogenesis, and the progression of reproductive cancers, thereby enhancing personalized medical treatments and addressing female infertility. This review highlights the pivotal role of tissue engineering in diagnosing and treating female infertility, emphasizing the importance of considering factors like biocompatibility, biomaterial selection, and mechanical properties in the design of bioengineered systems. The challenge of replicating the functionally specialized and structurally complex organs, such as the uterus and ovary, underscores the need for reliable techniques that improve morphological and functional restoration. Despite substantial progress, the goal of creating a fully artificial female reproductive system is still a challenge. Nonetheless, the recent fabrication of artificial ovaries, uteruses, cervixes, and vaginas marks significant advancements toward this aim. Looking forward, the challenges in bioengineering are expected to spur further innovations in both basic and applied sciences, potentially hastening the clinical adoption of these technologies.

Advancements in 3D skin bioprinting: processes, bioinks, applications and sensor integration

This comprehensive review explores the multifaceted landscape of skin bioprinting, revolutionizing dermatological research. The applications of skin bioprinting utilizing techniques like extrusion-, droplet-, laser- and light-based methods, with specialized bioinks for skin biofabrication have been critically reviewed along with the intricate aspects of bioprinting hair follicles, sweat glands, and achieving skin pigmentation. Challenges remain with the need for vascularization, safety concerns, and the integration of automated processes for effective clinical translation. The review further investigates the incorporation of biosensor technologies, emphasizing their role in monitoring and enhancing the wound healing process. While highlighting the remarkable progress in the field, critical limitations and concerns are critically examined to provide a balanced perspective. This synthesis aims to guide scientists, engineers, and healthcare providers, fostering a deeper understanding of the current state, challenges, and future directions in skin bioprinting for transformative applications in tissue engineering and regenerative medicine.

Uterine Biosynthesis through Tissue Engineering: An Overview of Current Methods and Status

In the last few decades, the rates of infertility among women have been on the rise, usually due to complications with the uterus and related tissue. A wide variety of reasons can cause uterine factor infertility and can be congenital or a result of disease. Uterine transplantation is currently used as a means to enable women with fertility issues to have a natural birth. However, multiple risk factors are involved in uterine transplantation that threaten the lives of the growing fetus and the mother, as a result of which the procedure is not prominently practiced. Uterine tissue engineering provides a potential solution to infertility through the regeneration of replacement of damaged tissue, thus allowing healing and restoration of reproductive capacity. It involves the use of stem cells from the patient incorporated within biocompatible scaffolds to regenerate the entire tissue. This manuscript discusses the need for uterine tissue engineering, giving an overview of the biological and organic material involved in the process. There are numerous existing animal models in which this procedure has been actualized, and the observations from them have been compiled here. These models are used to develop a further understanding of the integration of engineered tissues and the scope of tissue engineering as a treatment for uterine disorders. Additionally, this paper examines the scope and limitations of the procedure.

Understanding the cellular dynamics, engineering perspectives and translation prospects in bioprinting epithelial tissues

The epithelium is one of the important tissues in the body as it plays a crucial barrier role serving as a gateway into and out of the body. Most organs in the body contain an epithelial tissue component, where the tightly connected, organ-specific epithelial cells organize into cysts, invaginations, or tubules, thereby performing distinct to endocrine or exocrine secretory functions. Despite the significance of epithelium, engineering functional epithelium in vitro has remained a challenge due to it is special architecture, heterotypic composition of epithelial tissues, and most importantly, difficulty in attaining the apico-basal and planar polarity of epithelial cells. Bioprinting has brought a paradigm shift in fabricating such apico-basal polarized tissues. In this review, we provide an overview of epithelial tissues and provide insights on recapitulating their cellular arrangement and polarization to achieve epithelial function. We describe the different bioprinting techniques that have been successful in engineering polarized epithelium, which can serve as in vitro models for understanding homeostasis and studying diseased conditions. We also discuss the different attempts that have been investigated to study these 3D bioprinted engineered epithelium for preclinical use. Finally, we highlight the challenges and the opportunities that need to be addressed for translation of 3D bioprinted epithelial tissues towards paving way for personalized healthcare in the future.

Gelatin Methacryloyl/Sodium Alginate/Cellulose Nanocrystal Inks and 3D Printing for Dental Tissue Engineering Applications

In tissue engineering, developing suitable printing inks for fabricating hydrogel scaffolds via 3D printing is of high importance and requires extensive investigation. Currently, gelatin methacryloyl (GelMA)-based inks have been widely used for the construction of 3D-printed hydrogel scaffolds and cell-scaffold constructs for human tissue regeneration. However, many studies have shown that GelMA inks at low polymer concentrations had poor printability, and printed structures exhibited inadequate fidelity. In the current study, new viscoelastic inks composed of gelatin methacryloyl (GelMA), sodium alginate (Alg), and cellulose nanocrystal (CNC) were formulated and investigated, with CNC being used to improve the printability of inks and the fidelity of printed hydrogel structures and Alg being used to form ionically cross-linking polymer networks to enhance the mechanical strength of printed hydrogel structures. Rheological results showed that GelMA/Alg/CNC inks with different Alg-to-CNC ratios possessed good shear-thinning behavior, indicating that GelMA/Alg/CNC inks were suitable for 3D printing. The quantitative evaluation of printability and fidelity showed that a high concentration of CNC improved the printability of GelMA/Alg/CNC inks and concurrently promoted the fidelity of printed GelMA/Alg/CNC hydrogels. On the other hand, compression tests showed that a high concentration of Alg could enhance the mechanical strength of GelMA/Alg/CNC hydrogels due to the increase in cross-link density. Furthermore, GelMA/Alg/CNC hydrogels exhibited good biocompatibility and could promote the proliferation of human dental pulp stem cells (hDPSCs), suggesting their great potential in dental tissue engineering.

Biotechnological progresses in modelling the human endometrium: the evolution of current in vitro techniques and emerging trends

The endometrium plays a fundamental role in the reproductive system yet many etiologies of infertility-related endometrial diseases such as endometriosis, adenomyosis, Asherman's syndrome or endometrial cancer remain unknown. There are currently no treatments that minimize the effects of this devastating disorder. Appropriate model systems that closely mimic the architecture and function of the endometrium in healthy and pathological states are needed to understand the underlying molecular pathways and develop novel or more effective treatments. This review summarizes the key milestones of in vitro culture models of the human endometrium throughout history, as well as the applications of advanced bioengineering techniques in the modelling of both healthy and pathological endometrium. Opportunities for future approaches are also discussed.

Self-Assembled Peptide Hydrogels Loaded with Umbilical Cord-Derived Mesenchymal Stem Cells Repairing Injured Endometrium and Restoring Fertility

Endometrial injury is a major cause of infertility and recurrent miscarriage. However, no clinically available methods currently exist to effectively repair the damaged endometrium. Mesenchymal stem cells (MSCs) have emerged as a promising therapeutic approach for promoting tissue regeneration, yet a biocompatible scaffold capable of delivering MSCs and supporting their growth is needed. Herein, the study reports a peptide hydrogel scaffold, self-assembled from a peptide IVK8-RGD consisting of an ionic complementary peptide sequence IEVEIRVK and a bioactive sequence RGD, to load umbilical cord-derived mesenchymal stem cells (UC-MSCs). This peptide forms a hydrogel under the physiological condition through self-assembly, and the peptide hydrogel exhibits injectability and adhesiveness to uterus, making it suitable for endometrial repair. Importantly, this hydrogel supports the adhesion and proliferation of UC-MSCs in a 3D environment. In vivo experiments using rats with endometrial injury have shown that treatment with IVK8-RGD hydrogel loaded with UC-MSCs effectively restores endometrial thickness, inhibits fibrosis, and facilitates angiogenesis through activating Raf/MEK/ERK pathway, leading to significantly improved fertility and live birth rate. These findings demonstrate the potential of the UC-MSCs-loaded hydrogel in repairing damaged endometrium and may address the unmet clinical needs of treating recurrent miscarriage and infertility induced by endometrial damage.

Harnessing the power of artificial intelligence for human living organoid research

As a powerful paradigm, artificial intelligence (AI) is rapidly impacting every aspect of our day-to-day life and scientific research through interdisciplinary transformations. Living human organoids (LOs) have a great potential for in vitro reshaping many aspects of in vivo true human organs, including organ development, disease occurrence, and drug responses. To date, AI has driven the revolutionary advances of human organoids in life science, precision medicine and pharmaceutical science in an unprecedented way. Herein, we provide a forward-looking review, the frontiers of LOs, covering the engineered construction strategies and multidisciplinary technologies for developing LOs, highlighting the cutting-edge achievements and the prospective applications of AI in LOs, particularly in biological study, disease occurrence, disease diagnosis and prediction and drug screening in preclinical assay. Moreover, we shed light on the new research trends harnessing the power of AI for LO research in the context of multidisciplinary technologies. The aim of this paper is to motivate researchers to explore organ function throughout the human life cycle, narrow the gap between in vitro microphysiological models and the real human body, accurately predict human-related responses to external stimuli (cues and drugs), accelerate the preclinical-to-clinical transformation, and ultimately enhance the health and well-being of patients.

3D printed gelatin/PTMC core/shell scaffolds with NIR laser-tuned drug/biomolecule release for cancer therapy and uterine regeneration

Surgical resection is an efficient treatment for cancerous tissues and uterine fibroids in the women uterus. However, the insufficiency of clinical interventions could result in tumor recurrence, and the defective tissues remained would cause intrauterine adhesions (IUAs) and further affect reproduction capacity. In this study, 3D printed hydrogel/poly(l-lactide-co-trimethylene carbonate) (PLLA-co-TMC, "PTMC" in short) core/shell scaffolds with NIR-tuned doxorubicin hydrochloride (DOX) and estradiol (E2) dual release were designed and fabricated for cancer therapy and uterine regeneration. Gelatin (Gel) and DOX were homogeneously mixed and then 3D printed to form Gel-DOX scaffolds. Gel-DOX scaffolds were then immersed in PTMC-PDA@E2 solution to fabricate Gel-DOX/PTMC-PDA@E2 core/shell scaffolds. Consequently, Gel-DOX/PTMC-PDA@E2 scaffolds could release DOX and E2 in a chronological manner, firstly delivering DOX assisted by phototherapy (PTT) to effectively kill Hela cells and then sustainably releasing E2 to promote uterine tissue regeneration. In vitro experiments showed that core/shell scaffolds exhibited excellent anticancer efficiency through the synergy of DOX release and hyperthermia ablation. Moreover, E2 could be sustainably released for over 28 days in vitro to promote the proliferation of bone marrow-derived mesenchymal stem cells (BMSCs). The novel Gel-DOX/PTMC-PDA@E2 core/shell scaffolds have therefore exhibited potential promise for the treatment of cancer therapy and uterine regeneration.

Application of Additive Manufacturing in Assisted Reproductive Techniques: What Is the Evidence? A Clinical and Technical Systematic Review of the Literature

Background and Objectives: This article investigates the transformative impact of 3D and bio 3D printing technologies in assisted reproductive technology (ART), offering a comprehensive review of their applications in improving reproductive outcomes. Materials and Methods: Following PRISMA guidelines, we conducted a thorough literature search focusing on the intersection of ART and additive manufacturing, resulting in the inclusion of 48 research papers. Results: The study highlights bio 3D printing's potential in revolutionizing female infertility treatments, especially in follicle complex culture and ovary printing. We explore the use of decellularized extracellular matrix (dECM) as bioink, demonstrating its efficacy in replicating the ovarian microenvironment for in vitro maturation of primordial oocytes. Furthermore, advancements in endometrial cavity interventions are discussed, including the application of sustained-release systems for growth factors and stem cell integration for endometrial regeneration, showing promise in addressing conditions like Asherman's syndrome and thin endometrium. We also examine the role of conventional 3D printing in reproductive medicine, including its use in educational simulators, personalized IVF instruments, and microfluidic platforms, enhancing training and precision in reproductive procedures. Conclusions: Our review underscores both 3D printing technologies' contribution to the dynamic landscape of reproductive medicine. They offer innovative solutions for individualized patient care, augmenting success rates in fertility treatments. This research not only presents current achievements but also anticipates future advancements in these domains, promising to expand the horizons for individuals and families seeking assistance in their reproductive journeys.

Induced pluripotent stem cell-derived mesenchymal stem cells: whether they can become new stars of cell therapy

Stem cell therapy constitutes a pivotal subject in contemporary discourse, with donor stem cells having been employed in research and clinical treatments for several decades. Primary cell transplantation encompasses diverse stem cell types, including ectomesenchymal stem cells, hematopoietic stem cells, and various stem cell derivatives such as vesicles and extracellular vesicles. Nevertheless, the emergence of cell engineering techniques has heralded a new epoch in stem cell therapy, markedly broadening their therapeutic potential. Induced pluripotent stem cells (iPSCs) epitomize a significant milestone in modern medical biology. This groundbreaking discovery offers significant potential in disciplines such as biology, pathophysiology, and cellular regenerative medicine. As a result, iPSCs derived differentiated cells have become a pioneering avenue for cell therapy research. Induced mesenchymal stem cells (iMSCs), derived from iPSCs, represent a novel frontier in MSCs related research. Empirical evidence suggests that iMSCs demonstrate enhanced proliferative capacities compared to natural MSCs, with diminished age-related variability and heterogeneity. Numerous clinical trials have highlighted the prospective superiority of iMSCs. This article synthesizes current basic research and clinical trials pertaining to iMSCs, aiming to provide a reference point for future research endeavors.

Advancements in three-dimensional bioprinting for reproductive medicine: a systematic review

Reproductive failure due to age, genetics and disease necessitates innovative solutions. While reproductive tissue transplantation has advanced, ongoing research seeks superior approaches. Biomaterials, bioengineering and additive manufacturing, such as three-dimensional (3D) bioprinting, are harnessed to restore reproductive function. 3D bioprinting uses materials, cells and growth factors to mimic natural tissues, proving popular for tissue engineering, notably in complex scaffold creation with cell distribution. The versatility which is brought to reproductive medicine by 3D bioprinting allows more accurate and on-site applicability to various problems that are encountered in the field. However, in the literature, there is a lack of studies encompassing the valuable applications of 3D bioprinting in reproductive medicine. This systematic review aims to improve understanding, and focuses on applications in several branches of reproductive medicine. Advancements span the restoration of ovarian function, endometrial regeneration, vaginal reconstruction, and male germ cell bioengineering. 3D bioprinting holds untapped potential in reproductive medicine.

Biomimicking trilayer scaffolds with controlled estradiol release for uterine tissue regeneration

Scaffold-based tissue engineering provides an efficient approach for repairing uterine tissue defects and restoring fertility. In the current study, a novel trilayer tissue engineering scaffold with high similarity to the uterine tissue in structure was designed and fabricated via 4D printing, electrospinning and 3D bioprinting for uterine regeneration. Highly stretchable poly(l-lactide-co-trimethylene carbonate) (PLLA-co-TMC, "PTMC" in short)/thermoplastic polyurethane (TPU) polymer blend scaffolds were firstly made via 4D printing. To improve the biocompatibility, porous poly(lactic acid-co-glycolic acid) (PLGA)/gelatin methacryloyl (GelMA) fibers incorporated with polydopamine (PDA) particles were produced on PTMC/TPU scaffolds via electrospinning. Importantly, estradiol (E2) was encapsulated in PDA particles. The bilayer scaffolds thus produced could provide controlled and sustained release of E2. Subsequently, bone marrow derived mesenchymal stem cells (BMSCs) were mixed with gelatin methacryloyl (GelMA)-based inks and the formulated bioinks were used to fabricate a cell-laden hydrogel layer on the bilayer scaffolds via 3D bioprinting, forming ultimately biomimicking trilayer scaffolds for uterine tissue regeneration. The trilayer tissue engineering scaffolds thus formed exhibited a shape morphing ability by transforming from the planar shape to tubular structures when immersed in the culture medium at 37°C. The trilayer tissue engineering scaffolds under development would provide new insights for uterine tissue regeneration.

Evolution of biotechnological advances and regenerative therapies for endometrial disorders: a systematic review

BACKGROUND

The establishment and maintenance of pregnancy depend on endometrial competence. Asherman syndrome (AS) and intrauterine adhesions (IUA), or endometrial atrophy (EA) and thin endometrium (TE), can either originate autonomously or arise as a result from conditions (i.e. endometritis or congenital hypoplasia), or medical interventions (e.g. surgeries, hormonal therapies, uterine curettage or radiotherapy). Affected patients may present an altered or inadequate endometrial lining that hinders embryo implantation and increases the risk of poor pregnancy outcomes and miscarriage. In humans, AS/IUA and EA/TE are mainly treated with surgeries or pharmacotherapy, however the reported efficacy of these therapeutic approaches remains unclear. Thus, novel regenerative techniques utilizing stem cells, growth factors, or tissue engineering have emerged to improve reproductive outcomes.

OBJECTIVE AND RATIONALE

This review comprehensively summarizes the methodologies and outcomes of emerging biotechnologies (cellular, acellular, and bioengineering approaches) to treat human endometrial pathologies. Regenerative therapies derived from human tissues or blood which were studied in preclinical models (in vitro and in vivo) and clinical trials are discussed.

SEARCH METHODS

A systematic search of full-text articles available in PubMed and Embase was conducted to identify original peer-reviewed studies published in English between January 2000 and September 2023. The search terms included: human, uterus, endometrium, Asherman syndrome, intrauterine adhesions, endometrial atrophy, thin endometrium, endometritis, congenital hypoplasia, curettage, radiotherapy, regenerative therapy, bioengineering, stem cells, vesicles, platelet-rich plasma, biomaterials, microfluidic, bioprinting, organoids, hydrogel, scaffold, sheet, miRNA, sildenafil, nitroglycerine, aspirin, growth hormone, progesterone, and estrogen. Preclinical and clinical studies on cellular, acellular, and bioengineering strategies to repair or regenerate the human endometrium were included. Additional studies were identified through manual searches.

OUTCOMES

From a total of 4366 records identified, 164 studies (3.8%) were included for systematic review. Due to heterogeneity in the study design and measured outcome parameters in both preclinical and clinical studies, the findings were evaluated qualitatively and quantitatively without meta-analysis. Groups using stem cell-based treatments for endometrial pathologies commonly employed mesenchymal stem cells (MSCs) derived from the human bone marrow or umbilical cord. Alternatively, acellular therapies based on platelet-rich plasma (PRP) or extracellular vesicles are gaining popularity. These are accompanied by the emergence of bioengineering strategies based on extracellular matrix (ECM)-derived hydrogels or synthetic biosimilars that sustain local delivery of cells and growth factors, reporting promising results. Combined therapies that target multiple aspects of tissue repair and regeneration remain in preclinical testing but have shown translational value. This review highlights the myriad of therapeutic material sources, administration methods, and carriers that have been tested.

WIDER IMPLICATIONS

Therapies that promote endometrial proliferation, vascular development, and tissue repair may help restore endometrial function and, ultimately, fertility. Based on the existing evidence, cost, accessibility, and availability of the therapies, we propose the development of triple-hit regenerative strategies, potentially combining high-yield MSCs (e.g. from bone marrow or umbilical cord) with acellular treatments (PRP), possibly integrated in ECM hydrogels. Advances in biotechnologies together with insights from preclinical models will pave the way for developing personalized treatment regimens for patients with infertility-causing endometrial disorders such as AS/IUA, EA/TE, and endometritis.

REGISTRATION NUMBER

https://osf.io/th8yf/.

Hydrogel foam dressings with angiogenic and immunomodulatory factors from mesenchymal stem cells

Stem cell therapy and skin substitutes address the stalled healing of chronic wounds in order to promote wound closure; however, the high cost and regulatory hurdles of these treatments limit patient access. A low-cost method to induce bioactive healing has the potential to substantially improve patient care and prevent wound-induced limb loss. A previous study reported that bioactive factors derived from apoptotic-like mesenchymal stem cells (MSCs) demonstrated anti-inflammatory and proangiogenic effects and improved ischemic muscle regeneration. In this work, these MSC-derived bioactive factors were loaded into a hydrogel foam to harness immunomodulatory and angiogenic properties from MSC components to facilitate chronic wound healing without the high cost and translational challenges of cell therapies. After incorporation of bioactive factors, the hydrogel foam retained high absorbency, moisture retention, and target water vapor transmission rate. High loading efficiency was confirmed and release studies indicated that over 90% of loaded factors were released within 24 h. Ethylene oxide sterilization and 4-week storage did not affect the bioactive factor release profile or physical properties of the hydrogel foam dressing. Bioactivity retention of the released factors was also confirmed for as-sterilized, 4°C-stored, and -20°C-stored bioactive hydrogel foams as determined by relevant gene expression levels in treated pro-inflammatory (M1) macrophages. These results support the use of the bioactive dressings as an off-the-shelf product. Overall, this work reports a new method to achieve a first-line wound dressing with the potential to reduce persistent inflammation and promote angiogenesis in chronic wounds.

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.

Biological behavior of mesenchymal stem cells on two types of commercial dermal scaffolds: An in vitro study

Background

Acellular dermal matrix (ADM) has been introduced as an alternative to autogenous grafts. This study assessed the biological behavior of mesenchymal stem cells (MSCs) on two types of commercial ADM scaffolds.

Methods

The present in vitro study investigated the behavior of MSCs cultured on scaffold type I CenoDerm® (Tissue Regeneration Corporation) and type II Acellular Dermis (Iranian Tissue Product Co.) as the test groups and an empty well plate as the control group (n=78). Cell attachment was assessed after 12 hours of incubation using 6,4-diamidino-2-phenylindole (DAPI) staining and methyl thiazole tetrazolium (MTT) assay. Cell proliferation was assessed using the MTT assay at 24- and 84-hour and 7-day intervals. Cell morphology was also assessed under a scanning electron microscope (SEM) at 24 hours. MTT assay and DAPI staining were repeated for five samples in all the three groups. Mann-Whitney, ANOVA, and post hoc Tukey tests were used for statistical analysis.

Results

The DAPI staining and MTT assay showed similar results concerning cell attachment between all the groups at 12 hours (P=0.4). At 24 hours, cell proliferation was significantly higher in scaffold groups (P<0.001). At seven days, the lowest cell proliferation was noted in the scaffold II group, with a significant difference between the groups (P=0.01). At 24 hours, cell expansion was greater in the control group, followed by the scaffold I group.

Conclusion

Both scaffolds were similar in MSC attachment, but scaffold I appeared superior to scaffold II in terms of MSC proliferation and morphology in vitro.

Bioengineering approaches for the endometrial research and application

The endometrium undergoes a series of precise monthly changes under the regulation of dynamic levels of ovarian hormones that are characterized by repeated shedding and subsequent regeneration without scarring. This provides the potential for wound healing during endometrial injuries. Bioengineering materials highlight the faithful replication of constitutive cells and the extracellular matrix that simulates the physical and biomechanical properties of the endometrium to a larger extent. Significant progress has been made in this field, and functional endometrial tissue bioengineering allows an in-depth investigation of regulatory factors for endometrial and myometrial defects in vitro and provides highly therapeutic methods to alleviate obstetric and gynecological complications. However, much remains to be learned about the latest progress in the application of bioengineering technologies to the human endometrium. Here, we summarize the existing developments in biomaterials and bioengineering models for endometrial regeneration and improving the female reproductive potential.

Validity of stem cell-loaded scaffolds to facilitate endometrial regeneration and restore fertility: a systematic review and meta-analysis

Objective

Various stem cell-loaded scaffolds have demonstrated promising endometrial regeneration and fertility restoration. This study aimed to evaluate the efficacy of stem cell-loaded scaffolds in treating uterine injury in animal models.

Methods

The PubMed, Embase, Scopus, and Web of Science databases were systematically searched. Data were extracted and analyzed using Review Manager version 5.4. Improvements in endometrial thickness, endometrial glands, fibrotic area, and number of gestational sacs/implanted embryos were compared after transplantation in the stem cell-loaded scaffolds and scaffold-only group. The standardized mean difference (SMD) and confidence interval (CI) were calculated using forest plots.

Results

Thirteen studies qualified for meta-analysis. Overall, compared to the scaffold groups, stem cell-loaded scaffolds significantly increased endometrial thickness (SMD = 1.99, 95% CI: 1.54 to 2.44, P < 0.00001; I² = 16%) and the number of endometrial glands (SMD = 1.93, 95% CI: 1.45 to 2.41, P < 0.00001; I² = 0). Moreover, stem cell-loaded scaffolds present a prominent effect on improving fibrosis area (SMD = -2.50, 95% CI: -3.07 to -1.93, P < 0.00001; I² = 36%) and fertility (SMD = 3.34, 95% CI: 1.58 to 5.09, P = 0.0002; I² = 83%). Significant heterogeneity among studies was observed, and further subgroup and sensitivity analyses identified the source of heterogeneity. Moreover, stem cell-loaded scaffolds exhibited lower inflammation levels and higher angiogenesis, and cell proliferation after transplantation.

Conclusion

The evidence indicates that stem cell-loaded scaffolds were more effective in promoting endometrial repair and restoring fertility than the scaffold-only groups. The limitations of the small sample sizes should be considered when interpreting the results. Thus, larger animal studies and clinical trials are needed for further investigation.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO, identifier CRD42024493132.

Advancements of 3D bioprinting in regenerative medicine: Exploring cell sources for organ fabrication

3D bioprinting has unlocked new possibilities for generating complex and functional tissues and organs. However, one of the greatest challenges lies in selecting the appropriate seed cells for constructing fully functional 3D artificial organs. Currently, there are no cell sources available that can fulfill all requirements of 3D bioprinting technologies, and each cell source possesses unique characteristics suitable for specific applications. In this review, we explore the impact of different 3D bioprinting technologies and bioink materials on seed cells, providing a comprehensive overview of the current landscape of cell sources that have been used or hold potential in 3D bioprinting. We also summarized key points to guide the selection of seed cells for 3D bioprinting. Moreover, we offer insights into the prospects of seed cell sources in 3D bioprinted organs, highlighting their potential to revolutionize the fields of tissue engineering and regenerative medicine.

Multilayered Shape-Morphing Scaffolds with a Hierarchical Structure for Uterine Tissue Regeneration

Owing to dysfunction of the uterus, millions of couples around the world suffer from infertility. Different from conventional treatments, tissue engineering provides a new and promising approach to deal with difficult problems such as human tissue or organ failure. Adopting scaffold-based tissue engineering, three-dimensional (3D) porous scaffolds in combination with stem cells and appropriate biomolecules may be constructed for uterine tissue regeneration. In this study, a hierarchical tissue engineering scaffold, which mimicked the uterine tissue structure and functions, was designed, and the biomimicking scaffolds were then successfully fabricated using solvent casting, layer-by-layer assembly, and 3D bioprinting techniques. For the multilayered, hierarchical structured scaffolds, poly(l-lactide-co-trimethylene carbonate) (PLLA-co-TMC, "PLATMC" in short) and poly(lactic acid-co-glycolic acid) (PLGA) blends were first used to fabricate the shape-morphing layer of the scaffolds, which was to mimic the function of myometrium in uterine tissue. The PLATMC/PLGA polymer blend scaffolds were highly stretchable. Subsequently, after etching of the PLATMC/PLGA surface and employing estradiol (E2), polydopamine (PDA), and hyaluronic acid (HA), PDA@E2/HA multilayer films were formed on PLATMC/PLGA scaffolds to build an intelligent delivery platform to enable controlled and sustained release of E2. The PDA@E2/HA multilayer films also improved the biological performance of the scaffold. Finally, a layer of bone marrow-derived mesenchymal stem cell (BMSC)-laden hydrogel [which was a blend of gelatin methacryloyl (GelMA) and gelatin (Gel)] was 3D printed on the PDA@E2/HA multilayer films of the scaffold, thereby completing the construction of the hierarchical scaffold. BMSCs in the GelMA/Gel hydrogel layer exhibited excellent cell viability and could spread and be released eventually upon biodegradation of the GelMA/Gel hydrogel. It was shown that the hierarchically structured scaffolds could evolve from the initial flat shape into the tubular structure completely in an aqueous environment at 37 °C, fulfilling the requirement for curved scaffolds for uterine tissue engineering. The biomimicking scaffolds with a hierarchical structure and curved shape, high stretchability, and controlled and sustained E2 release appear to be very promising for uterine tissue regeneration.

VitroGel-loaded human MenSCs promote endometrial regeneration and fertility restoration

Introduction: Intrauterine adhesions (IUA), also known as Asherman's syndrome, is caused by trauma to the pregnant or non-pregnant uterus, which leads to damaged endometrial basal lining and partial or total occlusion of the uterine chambers, resulting in abnormal menstruation, infertility, or recurrent miscarriage. The essence of this syndrome is endometrial fibrosis. And there is no effective treatment for IUA to stimulate endometrial regeneration currently. Recently, menstrual blood-derived stem cells (MenSCs) have been proved to hold therapeutic promise in various diseases, such as myocardial infarction, stroke, diabetes, and liver cirrhosis. Methods: In this study, we examined the effects of MenSCs on the repair of uterine adhesions in a rat model, and more importantly, promoted such therapeutic effects via a xeno-free VitroGel MMP carrier. Results: This combined treatment reduced the expression of inflammatory factors, increased the expression of anti-inflammatory factors, restricted the area of endometrial fibrosis, diminished uterine adhesions, and partially restored fertility, showing stronger effectiveness than each component alone and almost resembling the sham group. Discussion: Our findings suggest a highly promising strategy for IUA treatment.

Current Biomedical Applications of 3D-Printed Hydrogels

Three-dimensional (3D) printing, also known as additive manufacturing, has revolutionized the production of physical 3D objects by transforming computer-aided design models into layered structures, eliminating the need for traditional molding or machining techniques. In recent years, hydrogels have emerged as an ideal 3D printing feedstock material for the fabrication of hydrated constructs that replicate the extracellular matrix found in endogenous tissues. Hydrogels have seen significant advancements since their first use as contact lenses in the biomedical field. These advancements have led to the development of complex 3D-printed structures that include a wide variety of organic and inorganic materials, cells, and bioactive substances. The most commonly used 3D printing techniques to fabricate hydrogel scaffolds are material extrusion, material jetting, and vat photopolymerization, but novel methods that can enhance the resolution and structural complexity of printed constructs have also emerged. The biomedical applications of hydrogels can be broadly classified into four categories-tissue engineering and regenerative medicine, 3D cell culture and disease modeling, drug screening and toxicity testing, and novel devices and drug delivery systems. Despite the recent advancements in their biomedical applications, a number of challenges still need to be addressed to maximize the use of hydrogels for 3D printing. These challenges include improving resolution and structural complexity, optimizing cell viability and function, improving cost efficiency and accessibility, and addressing ethical and regulatory concerns for clinical translation.

Cyclical endometrial repair and regeneration: Molecular mechanisms, diseases, and therapeutic interventions

The endometrium is a unique human tissue with an extraordinary ability to undergo a hormone-regulated cycle encompassing shedding, bleeding, scarless repair, and regeneration throughout the female reproductive cycle. The cyclical repair and regeneration of the endometrium manifest as changes in endometrial epithelialization, glandular regeneration, and vascularization. The mechanisms encompass inflammation, coagulation, and fibrinolytic system balance. However, specific conditions such as endometriosis or TCRA treatment can disrupt the process of cyclical endometrial repair and regeneration. There is uncertainty about traditional clinical treatments' efficacy and side effects, and finding new therapeutic interventions is essential. Researchers have made substantial progress in the perspective of regenerative medicine toward maintaining cyclical endometrial repair and regeneration in recent years. Such progress encompasses the integration of biomaterials, tissue-engineered scaffolds, stem cell therapies, and 3D printing. This review analyzes the mechanisms, diseases, and interventions associated with cyclical endometrial repair and regeneration. The review discusses the advantages and disadvantages of the regenerative interventions currently employed in clinical practice. Additionally, it highlights the significant advantages of regenerative medicine in this domain. Finally, we review stem cells and biologics among the available interventions in regenerative medicine, providing insights into future therapeutic strategies.

Current status and challenges in uterine myometrial tissue engineering

The uterus undergoes significant modifications throughout pregnancy to support embryo development and fetal growth. However, conditions like fibroids, adenomyosis, cysts, and C-section scarring can cause myometrial damage. The importance of the uterus and the challenges associated with myometrial damage, and the need for alternative approaches are discussed in this review. The review also explores the recent studies in tissue engineering, which involve principles of combining cells, scaffolds, and signaling molecules to create functional uterine tissues. It focuses on two key approaches in uterine tissue engineering: scaffold technique using decellularized, natural, and synthetic polymer and 3D bioprinting. These techniques create supportive structures for cell growth and tissue formation. Current treatment options for myometrial damage have limitations, leading to the exploration of regenerative medicine and integrative therapies. The review emphasizes the potential benefits of tissue engineering, including more effective and less invasive treatment options for myometrial damage. The challenges of developing biocompatible materials and optimizing cell growth and differentiation are discussed. In conclusion, uterine tissue engineering holds promise for myometrial regeneration and the treatment of related conditions. This review highlights the scientific advancements in the field and underscores the potential of tissue engineering as a viable approach. By addressing the limitations of current treatments, tissue engineering offers new possibilities for improving reproductive health and restoring uterine functionality. Future research shall focus on overcoming challenges and refining tissue engineering strategies to advance the field and provide effective solutions for myometrial damage and associated disorders.

VCAM-1+ hUC-MSCs Exert Considerable Neuroprotection Against Cerebral Infarction in Rats by Suppression of NLRP3-Induced Pyroptosis

Mesenchymal stem/stromal cells (MSCs) are spindle-like heterogeneous cell populations with advantageous bidirectional immunomodulatory and hematopoietic support effects. Vascular cellular adhesion molecule-1 (VCAM-1)+ MSCs have been reported to exhibit immunoregulatory and proangiogenic capacities. Here, we studied the effects of VCAM-1+ human umbilical cord (hUC)-MSCs on neuroprotection against cerebral infarction. Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO), and VCAM-1- and VCAM-1+ hUC-MSCs were intravenously injected into the rat 4 h post-MCAO surgery. Thereafter, modified neurological severity scores (mNSS) were determined, and the Morris water maze test, 2,3,5-triphenyltetrazolium chloride (TTC), hematoxylin and eosin (H&E), Nissl, TUNEL staining, and qRT-PCR were conducted. Following induction of oxygen-glucose deprivation/reoxygenation (OGD/R), SH-SY5Y cells were co-cultured with VCAM-1- and VCAM-1+ hUC-MSCs. CCK-8, flow cytometry, ELISA, and western blot analyses were performed in vitro. Compared with VCAM-1- hUC-MSCs, administration of VCAM-1+ hUC-MSCs revealed improved therapeutic efficacy against cerebral infarction in rats, as confirmed by lower mNSS scores and infarct volumes, as well as improved learning and memory capacities. In addition, VCAM-1+ hUC-MSCs exhibited improved efficacy against neurological defects in rats with cerebral infarction, accompanied by inhibition of the NLRP3-mediated inflammatory response. VCAM-1+ hUC-MSC co-culture improved the viability and diminished NLRP3-mediated inflammatory response in OGD/R-treated SH-SY5Y cells. Moreover, NLRP3 overexpression in SH-SY5Y cells prevented the beneficial effects of VCAM-1+ hUC-MSC co-culture. Overall, our findings demonstrated the relevance of VCAM-1+ hUC-MSC-based cytotherapy for preclinical neuroprotection against cerebral infarction.

Treatment strategies for intrauterine adhesion: focus on the exosomes and hydrogels

Intrauterine adhesion (IUA), also referred to as Asherman Syndrome (AS), results from uterine trauma in both pregnant and nonpregnant women. The IUA damages the endometrial bottom layer, causing partial or complete occlusion of the uterine cavity. This leads to irregular menstruation, infertility, or repeated abortions. Transcervical adhesion electroreception (TCRA) is frequently used to treat IUA, which greatly lowers the prevalence of adhesions and increases pregnancy rates. Although surgery aims to disentangle the adhesive tissue, it can exacerbate the development of IUA when the degree of adhesion is severer. Therefore, it is critical to develop innovative therapeutic approaches for the prevention of IUA. Endometrial fibrosis is the essence of IUA, and studies have found that the use of different types of mesenchymal stem cells (MSCs) can reduce the risk of endometrial fibrosis and increase the possibility of pregnancy. Recent research has suggested that exosomes derived from MSCs can overcome the limitations of MSCs, such as immunogenicity and tumorigenicity risks, thereby providing new directions for IUA treatment. Moreover, the hydrogel drug delivery system can significantly ameliorate the recurrence rate of adhesions and the intrauterine pregnancy rate of patients, and its potential mechanism in the treatment of IUA has also been studied. It has been shown that the combination of two or more therapeutic schemes has broader application prospects; therefore, this article reviews the pathophysiology of IUA and current treatment strategies, focusing on exosomes combined with hydrogels in the treatment of IUA. Although the use of exosomes and hydrogels has certain challenges in treating IUA, they still provide new promising directions in this field.

Preparation strategy of hydrogel microsphere and its application in skin repair

In recent years, hydrogel microsphere has attracted much attention due to its great potential in the field of skin repair. This paper reviewed the recent progress in the preparation strategy of hydrogel microsphere and its application in skin repair. In this review, several preparation methods of hydrogel microsphere were summarized in detail. In addition, the related research progress of hydrogel microspheres for skin repair was reviewed, and focused on the application of bioactive microspheres, antibacterial microspheres, hemostatic microspheres, and hydrogel microspheres as delivery platforms (hydrogel microspheres as a microcarrier of drugs, bioactive factors, or cells) in the field of skin repair. Finally, the limitations and future prospects of the development of hydrogel microspheres and its application in the field of skin repair were presented. It is hoped that this review can provide a valuable reference for the development of the preparation strategy of hydrogel microspheres and promote the application of hydrogel microspheres in skin repair.

Engineering considerations of iPSC-based personalized medicine

Personalized medicine aims to provide tailored medical treatment that considers the clinical, genetic, and environmental characteristics of patients. iPSCs have attracted considerable attention in the field of personalized medicine; however, the inherent limitations of iPSCs prevent their widespread use in clinical applications. That is, it would be important to develop notable engineering strategies to overcome the current limitations of iPSCs. Such engineering approaches could lead to significant advances in iPSC-based personalized therapy by offering innovative solutions to existing challenges, from iPSC preparation to clinical applications. In this review, we summarize how engineering strategies have been used to advance iPSC-based personalized medicine by categorizing the development process into three distinctive steps: 1) the production of therapeutic iPSCs; 2) engineering of therapeutic iPSCs; and 3) clinical applications of engineered iPSCs. Specifically, we focus on engineering strategies and their implications for each step in the development of iPSC-based personalized medicine.

Functionalized Human Umbilical Cord Mesenchymal Stem Cells and Injectable HA/Gel Hydrogel Synergy in Endometrial Repair and Fertility Recovery

Intrauterine adhesions (IUA) caused by endometrial injury are one of the main causes of female infertility. The current treatments for endometrial injury offer limited clinical benefits and cannot improve endometrial receptivity and pregnancy outcomes. Tissue engineering and regenerative medicine are considered potential solutions to address this concern and may offer effective treatment methods for the regeneration of injured human endometrium. Herein, we prepared an injectable hydrogel based on oxidized hyaluronic acid (HA-CHO) and hydrazide-grafted gelatin (Gel-ADH). The injectable hydrogel showed satisfactory biocompatibility when mixed with human umbilical cord mesenchymal stem cells (hUCMSCs). In an endometrial injury rat model, the treatment with hUCMSCs-loaded injectable hydrogel significantly enhanced the thickness of the endometrium and increased the abundance of blood vessels and glands in the injured endometrium compared to the control group. The hUCMSCs-loaded injectable hydrogel treatment significantly reduced endometrial fibrosis, decreased the expression of the pro-inflammatory factors (IL-1β and IL-6) and increased the expression of the anti-inflammatory factor (IL-10). This treatment induced endometrial VEGF expression by activating the MEK/ERK1/2 signaling pathway. Moreover, this treatment improved endometrial receptivity to the embryo and restored the embryo implantation rate similar to the sham group (48% in the sham group vs 46% in the treatment group), and this treatment achieved pregnancy and live birth in rats with endometrial injury. In addition, we also preliminarily validated the safety of this treatment in the maternal rats and fetuses. Collectively, our study showed that the hUCMSCs-loaded injectable hydrogel hold potential as an effective treatment strategy promoting rapid recovery of endometrial injury, and this hydrogel is a promising biomaterial for regenerative medicine applications. STATEMENT OF SIGNIFICANCE: : 1. Oxidized hyaluronic acid (HA-CHO)/hydrazide-grafted gelatin (Gel-ADH) hydrogel combined with human umbilical cord mesenchymal stem cells (hUCMSCs) are effective in improving the regeneration of endometrium in the endometrial injury rat model. 2. The hUCMSCs-loaded hydrogel treatment promotes the expression of endometrial VEGF through MEK/ERK1/2 signaling pathway and regulates the balance of inflammatory factors. 3. The embryo implantation and live birth rates restore to normal level in the endometrial injury rat model, and the hydrogel has no adverse effects on maternal rats, fetuses, and offspring development after the treatments.

Review: Endometrial function in pregnancy establishment in cattle

The endometrium is fundamentally required for successful pregnancy in ruminants and species where the posthatching conceptus undergoes a protracted elongation and peri-implantation phase of pregnancy. Moreover, there are substantial waves of pregnancy loss during this pre- and peri-implantation period of pregnancy the precise source of which has not been clearly defined i.e., the maternal uterine contribution to this loss. Understanding the molecular interactions required for successful pregnancy in cattle will allow us to intervene to support pregnancy success during this vulnerable window. The endometrium contributes to most key developmental milestones of pregnancy establishment, including (1) contributing to the regulation of the oestrus cycle, (2) nourishing the preimplantation conceptus, (3) responding to the conceptus to create a more receptive microenvironment, (4) providing essential biophysical support, and (5) signalling and producing factors which affect the mother systemically. This review will summarise what we currently know about conceptus-maternal interactions as well as identify the gaps in our knowledge that could be filled with newer in vitro model approaches. These include the use of microfluidics, organ-on-a-chip devices, and bioinformatic approaches. This will help maximise food production efficiency (both meat and dairy) and decrease the environmental burden, while enhancing our understanding of the fundamental processes required for successful implantation in cattle.

Microneedles for in situ tissue regeneration

Tissue injury is a common clinical problem, which may cause great burden on patients' life. It is important to develop functional scaffolds to promote tissue repair and regeneration. Due to their unique composition and structure, microneedles have attracted extensive attention in various tissues regeneration, including skin wound, corneal injury, myocardial infarction, endometrial injury, and spinal cord injury et al. Microneedles with micro-needle structure can effectively penetrate the barriers of necrotic tissue or biofilm, therefore improving the bioavailability of drugs. The use of microneedles to deliver bioactive molecules, mesenchymal stem cells, and growth factors in situ allows for targeted tissue and better spatial distribution. At the same time, microneedles can also provide mechanical support or directional traction for tissue, thus accelerating tissue repair. This review summarized the research progress of microneedles for in situ tissue regeneration over the past decade. At the same time, the shortcomings of existing researches, future research direction and clinical application prospect were also discussed.

Cell and cell-derivative-based therapy for liver diseases: current approaches and future promises

INTRODUCTION

According to the recent updates from World Health Organization, liver diseases are the 12th most common cause of mortality. Currently, orthotopic liver transplantation (OLT) is the most effective and the only treatment for end-stage liver diseases. Owing to several shortcomings like finite numbers of healthy organ donors, lifelong immunosuppression, and complexity of the procedure, cell and cell-derivatives therapies have emerged as a potential therapeutic alternative for liver diseases. Various cell types and therapies have been proposed and their therapeutic effects evaluated in preclinical or clinical studies, including hepatocytes, hepatocyte-like cells (HLCs) derived from stem cells, human liver stem cells (HLSCs), combination therapies with various types of cells, organoids, and implantable cell-biomaterial constructs with synthetic and natural polymers or even decellularized extracellular matrix (ECM).

AREAS COVERED

In this review, we highlighted the current status of cell and cell-derivative-based therapies for liver diseases. Furthermore, we discussed future prospects of using HLCs, liver organoids, and their combination therapies.

EXPERT OPINION

Promising application of stem cell-based techniques including iPSC technology has been integrated into novel techniques such as gene editing, directed differentiation, and organoid technology. iPSCs offer promising prospects to represent novel therapeutic strategies and modeling liver diseases.

3D bio-printed endometrial construct restores the full-thickness morphology and fertility of injured uterine endometrium

Severe damage to the uterine endometrium, which results in scar formation and endometrial dysfunction, eventually leads to infertility or pregnancy-related complications. No effective therapeutic treatment is currently available for such injuries owing to the structural complexity, internal environment, and function of the uterus. Three-dimensional (3D) bio-printing to engineer biomimetic structural constructs provides a unique opportunity for tissue regeneration. Herein, using 3D extrusion-based bioprinting (EBB), we constructed a bilayer endometrial construct (EC) based on a sodium alginate-hyaluronic acid (Alg-HA) hydrogel for functional regeneration of the endometrium. The upper layer of the 3D bio-printed EC is a monolayer of endometrial epithelial cells (EECs), while the lower layer has a grid-like microstructure loaded with endometrial stromal cells (ESCs). In a partial full-thickness uterine excision rat model, our bilayer EC not only restored the morphology and structure of the endometrial wall (including organized luminal/ glandular epithelium, stroma, vasculature and the smooth muscle layer), but also significantly improved the reproductive outcome in the surgical area after implantation (75%, 12/16, p < 0.01). Therefore, repair of the uterine endometrium using the developed 3D bio-printed bilayer EC may represent an effective regenerative treatment for severe endometrial injury. STATEMENT OF SIGNIFICANCE: Achieving structural and functional recovery of the endometrium following severe injury is still a challenge. Here, we designed a 3D bio-printed endometrial construct (EC) to mimic the native bilayer structure and cellular components of the endometrium. The bio-printed EC consists of a dense upper layer with endometrial epithelial cells and a lower layer with endometrial stromal cells. In particular, the 3D bio-printed EC significantly improved the reproductive outcome in the surgical area (75%, 12/16) compared to that of the cell-loaded non-printed group (12.5%, 2/16). This study demonstrates that a biomimetic bilayer construct can facilitate endometrial repair and regeneration. Therefore, an endometrial cells-loaded 3D-bioprinted EC is a promising therapeutic option for patients suffering from severe endometrial damage.

Mesenchymal Stromal/Stem Cell (MSC)-Based Vector Biomaterials for Clinical Tissue Engineering and Inflammation Research: A Narrative Mini Review

Mesenchymal stromal/stem cells (MSCs) have the ability of self-renewal, the potential of multipotent differentiation, and a strong paracrine capacity, which are mainly used in the field of clinical medicine including dentistry and orthopedics. Therefore, tissue engineering research using MSCs as seed cells is a current trending directions. However, the healing effect of direct cell transplantation is unstable, and the paracrine/autocrine effects of MSCs cannot be effectively elicited. Tumorigenicity and heterogeneity are also concerns. The combination of MSCs as seed cells and appropriate vector materials can form a stable cell growth environment, maximize the secretory features of stem cells, and improve the biocompatibility and mechanical properties of vector materials that facilitate the delivery of drugs and various secretory factors. There are numerous studies on tissue engineering and inflammation of various biomaterials, mainly involving bioceramics, alginate, chitosan, hydrogels, cell sheets, nanoparticles, and three-dimensional printing. The combination of bioceramics, hydrogels and cell sheets with stem cells has demonstrated good therapeutic effects in clinical applications. The application of alginate, chitosan, and nanoparticles in animal models has also shown good prospects for clinical applications. Three-dimensional printing technology can circumvent the shortage of biomaterials, greatly improve the properties of vector materials, and facilitate the transplantation of MSCs. The purpose of this narrative review is to briefly discuss the current use of MSC-based carrier biomaterials to provide a useful resource for future tissue engineering and inflammation research using stem cells as seed cells.

Repairing and Regenerating Injured Endometrium Methods

Good endometrium is the prerequisite and guarantee for reproduction and maternal and child health. Endometrial injury caused by operation or non-operation can lead to menstrual irregularities, amenorrhea, abortion, infertility, and other gynecological diseases to bother women. Intrauterine adhesions (IUA) and thin endometrium are common diseases caused by abnormal repair after endometrium damage. The incidence of IUA is not low after uterine operative surgery, and the recurrence is pretty high after uterine adhesiolysis. At present, there were many methods for endometrial repair in clinic or in the laboratory, but the efficacy was different from methods to methods. They are mainly including estrogen therapy, stem cell therapy, complementary medicine therapy, and some physical barrier therapy. In order to guide the effective repair and regeneration of endometrium in clinic, this paper reviews the merit and demerit of these methods for endometrium regeneration and repair that have been proved to be effective in experiments and clinical in recent years.

An injectable gelatin/sericin hydrogel loaded with human umbilical cord mesenchymal stem cells for the treatment of uterine injury

Abnormal endometrial receptivity is a major cause of the failure of embryo transplantation, which may lead to infertility, adverse pregnancy, and neonatal outcomes. While hormonal treatment has dramatically improved the fertility outcomes in women with endometriosis, a substantial unmet need persists in the treatment. In this study, methacrylate gelatin (GelMA) and methacrylate sericin (SerMA) hydrogel with human umbilical cord mesenchymal stem cells (HUMSC) encapsulation was designed for facilitating endometrial regeneration and fertility restoration through in situ injection. The presented GelMA/10%SerMA hydrogel showed appropriate swelling ratio, good mechanical properties, and degradation stability. In vitro cell experiments showed that the prepared hydrogels had excellent biocompatibility and cell encapsulation ability of HUMSC. Further in vivo experiments demonstrated that GelMA/SerMA@HUMSC hydrogel could increase the thickness of endometrium and improve the endometrial interstitial fibrosis. Moreover, regenerated endometrial tissue was more receptive to transfer embryos. Summary, we believed that GelMA/SerMA@HUMSC hydrogel will hold tremendous promise to repair or regenerate damaged endometrium.

3D Bioprinting of Induced Pluripotent Stem Cells and Disease Modeling

Patient-derived induced pluripotent stem cells (iPSCs), carrying the genetic information of the disease and capable of differentiating into multilineages in vitro, are valuable for disease modeling. 3D bioprinting enables the assembly of the cell-laden hydrogel into hierarchically three-dimensional architectures that recapitulate the natural tissues and organs. Investigation of iPSC-derived physiological and pathological models constructed by 3D bioprinting is a fast-growing field still in its infancy. Distinctly from cell lines and adult stem cells, iPSCs and iPSC-derived cells are more susceptible to external stimuli which can disturb the differentiation, maturation, and organization of iPSCs and their progeny. Here we discuss the fitness of iPSCs and 3D bioprinting from the perspective of bioinks and printing technologies. We provide a timely review of the progress of 3D bioprinting iPSC-derived physiological and pathological models by exemplifying the relatively prosperous cardiac and neurological fields. We also discuss scientific rigors and highlight the remaining issues to offer a guiding framework for bioprinting-assisted personalized medicine.

Bioprinted Hydrogels for Fibrosis and Wound Healing: Treatment and Modeling

Three-dimensional (3D) printing has been used to fabricate biomaterial scaffolds with finely controlled physical architecture and user-defined patterning of biological ligands. Excitingly, recent advances in bioprinting have enabled the development of highly biomimetic hydrogels for the treatment of fibrosis and the promotion of wound healing. Bioprinted hydrogels offer more accurate spatial recapitulation of the biochemical and biophysical cues that inhibit fibrosis and promote tissue regeneration, augmenting the therapeutic potential of hydrogel-based therapies. Accordingly, bioprinted hydrogels have been used for the treatment of fibrosis in a diverse array of tissues and organs, including the skin, heart, and endometrium. Furthermore, bioprinted hydrogels have been utilized for the healing of both acute and chronic wounds, which present unique biological microenvironments. In addition to these therapeutic applications, hydrogel bioprinting has been used to generate in vitro models of fibrosis in a variety of soft tissues such as the skin, heart, and liver, enabling high-throughput drug screening and tissue analysis at relatively low cost. As biological research begins to uncover the spatial biological features that underlie fibrosis and wound healing, bioprinting offers a powerful toolkit to recapitulate spatially defined pro-regenerative and anti-fibrotic cues for an array of translational applications.

Research progress of stem cell therapy for endometrial injury

Endometrial damage is an important factor leading to infertility and traditional conventional treatments have limited efficacy. As an emerging technology in recent years, stem cell therapy has provided new hope for the treatment of this disease. By comparing the advantages of stem cells from different sources, it is believed that menstrual blood endometrial stem cells have a good application prospect as a new source of stem cells. However, the clinical utility of stem cells is still limited by issues such as colonization rates, long-term efficacy, tumor formation, and storage and transportation. This paper summarizes the mechanism by which stem cells repair endometrial damage and clarifies the material basis of their effects from four aspects: replacement of damaged sites, paracrine effects, interaction with growth factors, and other new targets. According to the pathological characteristics and treatment requirements of intrauterine adhesion (IUA), the research work to solve the above problems from the aspects of functional bioscaffold preparation and multi-functional platform construction is also summarized. From the perspective of scaffold materials and component functions, this review will provide a reference for comprehensively optimizing the clinical application of stem cells.

Biohybrid materials: Structure design and biomedical applications

Biohybrid materials are proceeded by integrating living cells and non-living materials to endow materials with biomimetic properties and functionalities by supporting cell proliferation and even enhancing cell functions. Due to the outstanding biocompatibility and programmability, biohybrid materials provide some promising strategies to overcome current problems in the biomedical field. Here, we review the concept and unique features of biohybrid materials by comparing them with conventional materials. We emphasize the structure design of biohybrid materials and discuss the structure-function relationships. We also enumerate the application aspects of biohybrid materials in biomedical frontiers. We believe this review will bring various opportunities to promote the communication between cell biology, material sciences, and medical engineering.

Bi-potential hPSC-derived Müllerian duct-like cells for full-thickness and functional endometrium regeneration

Stem cell-based tissue regeneration strategies are promising treatments for severe endometrial injuries. However, there are few appropriate seed cells for regenerating a full-thickness endometrium, which mainly consists of epithelia and stroma. Müllerian ducts in female embryonic development develop into endometrial epithelia and stroma. Hence, we first generated human pluripotent stem cells (hPSC)-derived Müllerian duct-like cells (MDLCs) using a defined and effective protocol. The MDLCs are bi-potent, can gradually differentiate into endometrial epithelial and stromal cells, and reconstitute full-thickness endometrium in vitro and in vivo. Furthermore, MDLCs showed the in situ repair capabilities of reconstructing endometrial structure and recovering pregnancy function in full-thickness endometrial injury rats, and their differentiation fate was revealed by single-cell RNA sequencing (scRNA-seq). Our study provides a strategy for hPSC differentiation into endometrial lineages and an alternative seed cell for injured endometrial regeneration.

Systematic comparation of the biological and transcriptomic landscapes of human amniotic mesenchymal stem cells under serum-containing and serum-free conditions

Background

Human amniotic mesenchymal stem cells (hAMSCs) are splendid cell sources for clinical application in the administration of numerous refractory and relapse diseases. Despite the preferable prospect of serum-free (SF) condition for cell product standardization and pathogenic contamination remission, yet the systematic and detailed impact upon hAMSCs at both cellular and transcriptomic levels is largely obscure.

Methods

For the purpose, we preconditioned hAMSCs under serum-containing (SC) and SF medium for 48 h and compared the biological signatures and biofunctions from the view of cell morphology, immunophenotypes, multi-lineage differentiation in vitro, cell vitality, cytokine expression, and immunosuppressive effect upon the subpopulations of T lymphocytes, together with the PI3K-AKT-mTOR signaling reactivation upon cell vitality. Meanwhile, we took advantage of RNA-SEQ and bioinformatic analyses to verify the gene expression profiling and genetic variation spectrum in the indicated hAMSCs.

Results

Compared with those maintained in SC medium, hAMSCs pretreated in SF conditions manifested conservation in cell morphology, immunophenotypes, adipogenic differentiation, and immunosuppressive effect upon the proliferation and activation of most of the T cell subpopulations, but with evaluated cytokine expression (e.g., TGF-β1, IDO1, NOS2) and declined osteogenic differentiation and cell proliferation as well as proapoptotic and apoptotic cells. The declined proliferation in the SF group was efficiently rescued by PI3K-AKT-mTOR signaling reactivation. Notably, hAMSCs cultured in SF and SC conditions revealed similarities in gene expression profiling and variations in genetic mutation at the transcriptome level. Instead, based on the differentially expressed genes and variable shear event analyses, we found those genes were mainly involved in DNA synthesis-, protein metabolism-, and cell vitality-associated biological processes and signaling pathways (e.g., P53, KRAS, PI3K-Akt-mTOR).

Conclusions

Collectively, our data revealed the multifaceted cellular and molecular properties of hAMSCs under SC and SF conditions, which suggested the feasibility of serum-free culture for the preferable preparation of standardized cell products for hAMSC drug development and clinical application.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03179-2.

Hyaluronic acid methacrylate/pancreatic extracellular matrix as a potential 3D printing bioink for constructing islet organoids

Islet transplantation has poor long-term efficacy because of the lack of extracellular matrix support and neovascularization; this limits its wide application in diabetes research. In this study, we develop a 3D-printed islet organoid by combining a pancreatic extracellular matrix (pECM) and hyaluronic acid methacrylate (HAMA) as specific bioinks. The HAMA/pECM hydrogel was validated in vitro to maintain islet cell adhesion and morphology through the Rac1/ROCK/MLCK signaling pathway, which helps improve islet function and activity. Further, in vivo experiments confirmed that the 3D-printed islet-encapsulated HAMA/pECM hydrogel increases insulin levels in diabetic mice, maintains blood glucose levels within a normal range for 90 days, and rapidly secretes insulin in response to blood glucose stimulation. In addition, the HAMA/pECM hydrogel can facilitate the attachment and growth of new blood vessels and increase the density of new vessels. Meanwhile, the designed 3D-printed structure was conducive to the formation of vascular networks and it promoted the construction of 3D-printed islet organoids. In conclusion, our experiments optimized the HAMA/pECM bioink composition and 3D-printed structure of islet organoids with promising therapeutic effects compared with the HAMA hydrogel group that can be potentially used in clinical applications to improve the effectiveness and safety of islet transplantation in vivo. STATEMENT OF SIGNIFICANCE: The extraction process of pancreatic islets can easily cause damage to the extracellular matrix and vascular system, resulting in poor islet transplantation efficiency. We developed a new tissue-specific bioink by combining pancreatic extracellular matrix (pECM) and hyaluronic acid methacrylate (HAMA). The islet organoids constructed by 3D printing can mimic the microenvironment of the pancreas and maintain islet cell adhesion and morphology through the Rac1/ROCK/MLCK signaling pathway, thereby improving islet function and activity. In addition, the 3D-printed structures we designed are favorable for the formation of new blood vessel networks, bringing hope for the long-term efficacy of islet transplantation.