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

STUDY QUESTION Can human umbilical cord platelet-rich plasma (hUC-PRP) efficiently treat endometrial damage and restore fertility in a preclinical murine model? SUMMARY ANSWER Local application of hUC-PRP promotes tissue regeneration and fertility restoration in a murine model of Asherman syndrome and endometrial atrophy (AS/EA). WHAT IS KNOWN ALREADY AS/EA are well-described endometrial pathologies that cause infertility, however, there are currently no gold standard treatments available. Recent reports have described the successful use of human platelet-rich plasma (hPRP) in reproductive medicine, and its regenerative potential is further enhanced using hUC-PRP, due to the ample growth factors and reduced pro-inflammatory cytokines in the latter. STUDY DESIGN, SIZE, DURATION hUC-PRP (n = 3) was processed, characterized, and delivered locally to endometrial damage in a murine model (n = 50). The hUC-PRP was either used alone or loaded into a decellularized porcine endometrium-derived extracellular matrix (EndoECM) hydrogel; endometrial regeneration, fertility outcomes and immunocompatibility were evaluated two weeks following treatment administration. PARTICIPANTS/MATERIALS, SETTING, METHODS Umbilical cord blood was obtained from women in childbirth. Endometrial damage (mimicking AS/EA) was induced using ethanol in eight-week-old C57BL/6 mice, and treated with the most concentrated hUC-PRP sample four days later. Characterization of hUC-PRP and immunotolerance was carried out with multiplex technology, while uterine samples were analyzed by immunohistochemistry and quantitative PCR. The number of embryos and their morphology was determined visually. LARGE SCALE DATA N/A. MAIN RESULTS AND THE ROLE OF CHANCE Platelet density was enhanced three-fold in hUC-PRP compared to that in hUC blood (P < 0.05). hUC-PRP was enriched with growth factors related to tissue regeneration (i.e., hepatocyte growth factor (HGF), platelet-derived growth factor (PDGF-BB), and epidermal growth factor (EGF)), which were released constantly (in vitro) when hUC-PRP was loaded into EndoECM. Both treatments (hUC-PRP alone and hUC-PRP with EndoECM) were immunotolerated and caused significantly regeneration of the damaged endometrium, evidenced by increased endometrial area, neoangiogenesis, cell proliferation and gland density and lower collagen deposition with respect to non-treated uterine horns (P < 0.05). Additionally, we detected augmented gene expression of Akt1, VEGF, and Ang, which are involved in regenerative and proliferation pathways. Finally, hUC-PRP treatment restored pregnancy rates in the mouse model. LIMITATIONS, REASONS FOR CAUTION This proof-of-concept pilot study was based on a murine model of endometrial damage and the use of EndoECM requires further validation prior to clinical implementation for women affected by AS/EA. WIDER IMPLICATIONS OF THE FINDINGS The local administration of hUC-PRP has high impact and is immunotolerated in a murine model of AS/EA, as has been reported in other tissues, making it a promising candidate for heterologous treatment of these endometrial pathologies. STUDY FUNDING/COMPETING INTEREST(S) This study was supported by the Ministerio de Ciencia, Innovación y Universidades; Conselleria de Innovación, Universidades, Ciencia y Sociedad Digital, Generalitat Valenciana; and Instituto de Salud Carlos III. The authors do not have any conflicts of interest to declare.

There are several conditions that lead to female infertility, where traditional or conventional treatments have limited efficacy. In these challenging scenarios, stem cell (SC) therapies have been investigated as alternative treatment strategies. Human umbilical cord (hUC) mesenchymal stem cells (hUC-MSC), along with their secreted paracrine factors, extracts, and biomolecules, have emerged as promising therapeutic alternatives in regenerative medicine, due to their remarkable potential to promote anti-inflammatory and regenerative processes more efficiently than other autologous treatments. Similarly, hUC blood derivatives, such as platelet-rich plasma (PRP), or isolated plasma elements, such as growth factors, have also demonstrated potential. This literature review aims to summarize the recent therapeutic advances based on hUC-MSCs, hUC blood, and/or other plasma derivatives (e.g., extracellular vesicles, hUC-PRP, and growth factors) in the context of female reproductive medicine. We present an in-depth analysis of the principal molecules mediating tissue regeneration, compiling the application of these therapies in preclinical and clinical studies, within the context of the human reproductive tract. Despite the recent advances in bioengineering strategies that sustain delivery and amplify the scope of the therapeutic benefits, further clinical trials are required prior to the wide implementation of these alternative therapies in reproductive medicine.