The uterine lining (endometrium) regenerates repeatedly over the life span as part of its normal physiology. Substantial portions of the endometrium are shed during childbirth (parturition) and, in some species, menstruation, but the tissue is rapidly rebuilt without scarring, rendering it a powerful model of regeneration in mammals. Nonetheless, following some assaults, including medical procedures and infections, the endometrium fails to regenerate and instead forms scars that may interfere with normal endometrial function and contribute to infertility. Thus, the endometrium provides an exceptional platform to answer a central question of regenerative medicine: Why do some systems regenerate while others scar? Here, we review our current understanding of diverse endometrial disruption events in humans, nonhuman primates, and rodents, and the associated mechanisms of regenerative success and failure. Elucidating the determinants of these disparate repair processes promises insights into fundamental mechanisms of mammalian regeneration with substantial implications for reproductive health.

Intrauterine adhesions (IUA), also known as Asherman's syndrome, arise from damage to the basal layer of the endometrium, frequently caused by intrauterine interventions. This damage leads to nonregenerative healing of endometrium resulting in replacement by fibrous connective tissue, which bring about the adherence of opposing endometrium to render the uterine cavity and/or cervical canal partially or completely obliterated. IUA is a common cause of the refractory uterine infertility. Hysteroscopy is the gold standard for diagnosis of IUA. However, the method of accurately predicting the likelihood of achieving a live birth in the future remains established. Classical treatments have shown limited success, particularly in severe cases. Therefore, utilizing new research methods to deepen the understanding of the pathogenesis of IUA will facilitate the new treatment approaches to be found. In this article we briefly described the advances in the pathogenesis of IUA, with focus on inflammation and parenchymal cellular homeostasis disruption, defects in autophagy and the role of ferroptosis, and we also outlined the progress in IUA therapy.© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

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.

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.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.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.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.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.© The Author(s) 2022. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology.

Intrauterine adhesion (IUA), often leading to gynecological complications including amenorrhea, abdominal pain and infertility, is frequently induced by injuries to the endometrium. Hence it would be of great benefit to take efforts to prevent adhesion after intrauterine operations. Orally administration of 17β-estradiol (E2) is commonly used to promote endometrium regeneration, but is limited by low concentrations at the injured sites. We aim at preparing an E2-releasing uterine stent, which could improve the efficiency of E2 therapy and be utilized for IUA prevention.We designed a silicone rubber stent, which could be implanted in the uterine cavity and continuously release E2 in long term. Stents were placed in rodent uterine, and removed at different time points. Remaining E2 in stent was measured by high performance liquid chromatography (HPLC), and organ E2 concentrations were detected by enzyme-linked immuno sorbent assay (ELISA). Endometrium morphology was examined by histological staining of paraffin sections.Our stent showed a controlled release of E2 in rodent uterine for over 60 days, and significantly increased E2 concentration in serum and in situ uterine. After the stent was removed from uterine, E2 rapidly reverted to a normal level. Also, the stent did not induce pathological changes in endometrium.The uterine stent provided abundant local E2 in uterine cavity with satisfactory safety. The silicone rubber based E2-releasing uterine stent could be further advanced by adjusting its shape and E2 load for its clinical application, and might promisingly help lowering the incidence of IUA.© 2022 The Japanese Society for Regenerative Medicine. Production and hosting by Elsevier B.V.

The endometrial injury usually results in intrauterine adhesions (IUAs). However, there is no effective treatment to promote the regeneration of the endometrium currently. The decellularized amnion membrane (AM) is a promising material in human tissue repair and regeneration due to its biocompatibility, biodegradability, as well as the preservation of abundant bioactive components. Here, an innovative drug-delivering system based on human amniotic extracellular matrix (HAECM) scaffolds were developed to facilitate endometrium regeneration. The 17β-estradiol (E) loaded PLGA microspheres (E-MS) were well dispersed in the scaffolds without altering their high porosity. E released from E-MS-HAECM scaffolds showed a decreased initial burst release followed with a sustained release for 21 days, which coincided with the female menstrual cycle. Results of cell proliferation suggested E-MS-HAECM scaffolds had good biocompatibility and provided more biologic guidance of endometrial cell proliferation except for mechanical supports. Additionally, the mRNA expression of growth factors in endometrial cells indicated that HAECM scaffolds could upregulate the expression of EGF and IGF-1 to achieve endometrium regeneration. Therefore, these advantages provide the drug-loaded bioactive scaffolds with new choices for the treatments of IUAs.

To study the factors affecting the prognosis of patients with intrauterine adhesions (IUAs) after transcervical resection of adhesions (TCRA), analyze the reproductive outcome, and guide prognostic improvements.Prospective study.Our study included 292 patients diagnosed with intrauterine adhesions who underwent follow-up office hysteroscopy at Shenyang Women's and Children's Hospital between June 2018 and June 2022.Patients were divided into case (52 patients whose hysteroscopy results indicated the presence of intrauterine adhesions) and nocase (240 patients whose uterine cavity had returned to normal shape without obvious adhesion) groups based on the results of a 2-month follow-up hysteroscopy following transcervical resection of adhesions. Clinical data were collected and compared with various influencing factors, and the combined effect of these factors was assessed using multifactorial logistic regression analysis. A nomogram prediction model was constructed and internally validated based on multifactorial analysis.Intrauterine re-adhesion observed at 2-months follow-up after transcervical resection of adhesions.Postoperative re-adhesion occurred in 52 of 292 patients with intrauterine adhesions. Multifactorial binary logistic regression analysis showed that intrauterine adhesion barrier gel reapplication 5 days after transcervical resection of adhesions was a protective factor while the preoperative American Fertility Society scores demonstrated that severe intrauterine adhesions and chronic endometritis were risk factors (P <0.05). The results of the multifactorial analysis were used to build a nomogram model, and the area under the curve value of the nomogram model for predicting postoperative recurrence was 0.914 (95% confidence interval: 0.864-0.956). The bootstrap method was subsequently used to resample 1,000 times for internal validation. The results showed that the internal validation C-index was 0.9135 and that the calibration curve and ideal curve were well-matched.The prognosis of patients with intrauterine adhesions after transcervical resection of adhesions is related to the severity of preoperative intrauterine adhesions, presence of chronic endometritis, and intrauterine adhesion barrier gel reapplication 5 days after transcervical resection of adhesions. Therefore, clinicians should monitor patients using targeted data to reduce recurrence risk after transcervical resection of adhesions and improve the prognosis of patients with intrauterine adhesions.Copyright © 2024. Published by Elsevier Inc.

Approximately 15-20% of all clinically confirmed pregnancies end in a miscarriage. Intrauterine adhesions (IUAs) are a possible complication after miscarriage, but their prevalence and the contribution of possible risk factors have not been elucidated yet. In addition, the long-term reproductive outcome in relation to IUAs has to be elucidated.We systematically searched the literature for studies that prospectively assessed the prevalence and extent of IUAs in women who suffered a miscarriage. To be included, women diagnosed with a current miscarriage had to be systematically evaluated within 12 months by hysteroscopy after either spontaneous expulsion or medical or surgical treatment. Studies that included women with a history of recurrent miscarriage only or that evaluated the IUAs after elective abortion or beyond 12 months after the last miscarriage were not included. Subsequently, long-term reproductive outcomes after expectant (conservative), medical or surgical management were assessed in women with and without post-miscarriage IUAs.We included 10 prospective studies reporting on 912 women with hysteroscopic evaluation within 12 months of miscarriage and 8 prospective studies, including 1770 women, reporting long-term reproductive outcome. IUAs were detected in 183 women, resulting in a pooled prevalence of 19.1% [95% confidence interval (CI): 12.8-27.5%]. The extent of IUAs was reported in 124 women (67.8%) and was mild, moderate and severe respectively in 58.1, 28.2 and 13.7% of cases. Relative to women with one miscarriage, women with two or three or more miscarriages showed an increased risk of IUAs by a pooled OR of 1.41 and 2.1, respectively. The number of dilatation and curettage (D&C) procedures seemed to be the main driver behind these associations. A total of 150 congenital and acquired intrauterine abnormalities were encountered in 675 women, resulting in a pooled prevalence of 22.4% (95% CI: 16.3-29.9%). Similar reproductive outcomes were reported subsequent to conservative, medical or surgical management for miscarriage, although the numbers of studies and of included women were limited. No studies reported long-term reproductive outcomes following post-miscarriage IUAs.IUAs are frequently encountered, in one in five women after miscarriage. In more than half of these, the severity and extent of the adhesions was mild, with unknown clinical relevance. Recurrent miscarriages and D&C procedures were identified as risk factors for adhesion formation. Congenital and acquired intrauterine abnormalities such as polyps or fibroids were frequently identified. There were no studies reporting on the link between IUAs and long-term reproductive outcome after miscarriage, while similar pregnancy outcomes were reported subsequent to conservative, medical or surgical management. Although this review does not allow strong clinical conclusions on treatment management, it signals an important clinical problem. Treatment strategies are proposed to minimize the number of D&C in an attempt to reduce IUAs.

Does placing an intrauterine balloon for different durations (7, 14 or 28 days) affect the recurrence of intrauterine adhesions after hysteroscopic adhesiolysis?Prospective randomized control trial involving 138 patients recruited over a 12-month period and followed up post-operatively for 15 months. The primary outcome measure was the rate of adhesion reformation at third-look hysteroscopy.At third-look hysteroscopy, 8 weeks after the initial hysteroscopy, the adhesion recurrence rate in women who had an intrauterine balloon for 28 days (20%) was significantly (P < 0.01) lower than that of women who had the balloon for 14 days (55%) or 7 days (36.8%).Placing an intrauterine balloon for 28 days instead of 7 or 14 days after hysteroscopic adhesiolysis resulted in a greater reduction in the recurrence rate of adhesions. However, the study was underpowered to address whether the ongoing pregnancy rate could be improved by keeping the balloon in the uterine cavity for a longer period of time.Copyright © 2019. Published by Elsevier Ltd.

To compare duration of Cook balloon uterine stent on re-adhesions formation, and observe its effect on serum transforming growth factor β1 (TGF-β1) and plasminogen activator inhibitor-1 (PAI-1) levels in patients with intrauterine adhesions (IUA) undergoing hysteroscopic transcervical resection of adhesion (TCRA).Randomised controlled trial.No. 215 Hospital of Shaanxi Nuclear Industry, Shaanxi Province, China, from January 2018 to January 2019.A total of 98 patients with IUA, who underwent hysteroscopic TCRA with cold scissors, were randomly divided into Group A (n=49) and Group B (n=49). Cook balloon uterine stent was placed for 37 days in Group A and 7 days in Group B. Efficacy of two groups was compared.Total effective rate in Group A was higher than that in Group B (p=0.021). After treatment, levels of serum TGF-β1 and PAI-1 in Group A were lower than those in Group B (p <0.001, and p=0.001, respectively). Recurrence rate of IUA at three months after treatment and total incidence of complications in Group A were lower than those in Group B (p=0.012, and 0.037, respectively). Pregnancy rate in the 2-year follow-up period in Group A was higher than that in Group B (p= 0.043).Placement of Cook balloon uterine stent for 37 days after hysteroscopic TCRA in patients with IUA can effectively prevent postoperative intrauterine re-adhesion, have few complications, low recurrence rate of IUA and high re-pregnancy rate, and reduce levels of serum TGF-β1 and PAI-1. Key Words: Intrauterine adhesions (IUA), Transcervical resection of adhesion (TCRA), Transforming growth factor β1 (TGF-β1), Plasminogen activator inhibitor-1 (PAI-1), Pregnancy.

To describe a comprehensive approach to women with severe Asherman syndrome and amenorrhea, including preoperative, operative, and postoperative care and subsequent resumption menses, and pregnancy.Retrospective case series.Tertiary care teaching hospital.Twelve women with severe Asherman syndrome and amenorrhea.Preoperative administration of prolonged preoperative and postoperative oral E(2) to enhance endometrial proliferation, intraoperative abdominal ultrasound-directed hysteroscopic lysis of uterine synechia to ensure that the dissection is performed in the proper tissue plane, placement of a triangular uterine balloon catheter during surgery, and postoperative removal with placement of a copper intrauterine device (IUD) to maintain separation of the cavity and mechanically lyse newly formed adhesions during removal.Resumption of menses, pregnancy, and delivery.All women resumed menses, although 5 of 12 had a preoperative maximal endometrial thickness of 4 mm or less, with follow-up ranging from 6 months to 10 years. Six of nine women less than age 39 years (67%) became pregnant, and four of six achieved a term or near-term delivery.Comprehensive management provides the best possible outcomes in poor-prognosis women with severe Asherman syndrome.Copyright © 2012 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

To compare the efficacy of intrauterine balloon, intrauterine contraceptive device and hyaluronic acid gel in the prevention of the adhesion reformation after hysteroscopic adhesiolysis for Asherman's syndrome.Retrospective cohort study of 107 women with Asherman's syndrome who were treated with hysteroscopic division of intrauterine adhesions. After hysteroscopic adhesiolysis, 20 patients had intrauterine balloon inserted, 28 patients had intrauterine contraceptive device (IUD) fitted, 18 patients had hyaluronic acid gel instilled into the uterine cavity, and 41 control subjects did not have any of the three additional treatment measures. A second-look hysteroscopy was performed in all cases, and the effect of hysteroscopic adhesiolysis was scored by the American Fertility Society classification system.Both the intrauterine balloon group and the IUD group achieved significantly (P<0.001) greater reduction in the adhesion score than that of the hyaluronic acid gel group and control group. The efficacy of the balloon was greater than that of the IUD (P<0.001). There was no significant difference in results between the hyaluronic acid gel group and the control groups.The insertion of an intrauterine balloon or intrauterine device is more effective than the use of hyaluronic acid gel in the prevention of intra-uterine adhesion reformation.Crown Copyright © 2013. Published by Elsevier Ireland Ltd. All rights reserved.

What is the efficacy of platelet-rich plasma (PRP) in reducing adhesion reformation in women with moderate to severe intrauterine adhesions (IUA)?In this randomized controlled trial, women with moderate-to-severe IUA were recruited between November 2019 and June 2021 from a university hospital and randomized into the PRP or control group. The PRP group was treated using an intrauterine-suitable balloon combined with PRP infusion following hysteroscopic adhesiolysis, whereas the control group received only the former intervention. The reductions in adhesion scores from before to after surgery and the adhesion reformation rate were analysed.A total of 123 participants successfully completed the study (PRP group, 63; control group, 60). Age, pregnancy history, menstrual score and American Fertility Society score before surgery were not significantly different between the two groups. At the second-look hysteroscopy, the PRP group had a significantly greater reduction in adhesion score than the control group (7 versus 6, respectively; P = 0.027). The postoperative adhesion reformation rates in the PRP group and the control group were 20.6% and 30.0%, respectively (risk ratio 0.69, 95% confidence interval 0.27-1.38, P = 0.232; number needed to treat 10.6).Intrauterine PRP infusion seems to be beneficial in reducing postoperative adhesion reformation following hysteroscopic adhesiolysis.Copyright © 2022 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.