Mesenchymal stem cells (MSCs) are a source of a wide range of soluble factors, including different proteins, growth factors, cytokines, chemokines, and DNA and RNA molecules, in addition to numerous secondary metabolites and byproducts of their metabolism. MSC secretome can be formally divided into secretory and vesicular parts, both of which are very important for intercellular communication and are involved in processes such as angiogenesis, proliferation, and immunomodulation. Exosomes are thought to have the same content and function as the MSCs from which they are derived, but they also have a number of advantages over stem cells, including low immunogenicity, unaltered functional activity during freezing and thawing, and a lack of tumor formation. In addition, MSC pre-treatment with various inflammatory factors or hypoxia can alter their secretomes so that it can be modified into a more effective treatment. Paracrine factors secreted by MSCs improve the survival of other cell populations by several mechanisms, including immunomodulatory (mostly anti-inflammatory) activity and anti-apoptotic activity partly based on Hsp27 upregulation. Reproductive medicine is one of the fields in which this cell-free approach has been extensively researched. This review presents the possible applications and challenges of using MSC secretome in the treatment of infertility. MSCs and their secretions have been shown to have beneficial effects in various models of female and male infertility resulting from toxic damage, endocrine disorders, trauma, infectious agents, and autoimmune origin.

Serum antibodies against the small heat shock protein Hsp27 (HspB1) have been associated with certain diseases but have not been studied in infertility. Sera from 73 infertile patients were tested for antisperm antibodies using agglutination and immobilization tests and ELISA, and for anti-Hsp27 antibodies using ELISA. Of these sera, 31 (42.5%) were positive for anti-Hsp27 antibodies, and 46 (63%) were positive for antisperm antibodies through analysis with at least one method. A total of 17 sera (23.3%) were positive for both anti-Hsp27 and antisperm antibodies. When sera containing both anti-Hsp27 and antisperm antibodies were used for immunofluorescence, the neck and tail of spermatozoa were stained, where the related sperm-specific protein HspB10 (ODF1) is localized. These data suggest that anti-Hsp27 antibodies are elevated in a certain proportion of infertile patients, which, in some of them, could be due to cross-reactivity between Hsp27 and the related sperm cytoskeletal component ODF1.

Background: Thin endometrium is a significant cause of infertility due to impaired regeneration, reduced receptivity, and insufficient angiogenesis. Mesenchymal stem cell-derived secretome (MSCsec) is a promising cell-free therapy because it contains bioactive molecules that promote tissue repair. This study evaluated the effects of Wharton’s jelly-derived MSC secretome (WJ-MSCsec) on human endometrial stromal cells (EnSCs) and endothelial cells in vitro. Methods: WJ-MSCs were isolated from umbilical cord tissue, characterized, and cultured under serum-free conditions. The concentrated secretome was analyzed using a human angiogenesis proteome array. EnSCs were isolated from endometrial biopsies. EnSC proliferation and migration in the presence of WJ-MSCsec were assessed using CCK-8 and scratch wound-healing assays. Pro-angiogenic activity of WJ-MSCsec was evaluated using a Matrigel tube formation assay with human umbilical vein endothelial cells (HUVECs). Results: Proteomic analysis of WJ-MSCsec revealed the presence of angiogenic, mitogenic, immunomodulatory, and chemotactic factors. Treatment with WJ-MSCsec significantly enhanced EnSC proliferation and accelerated wound closure. Furthermore, WJ-MSCsec markedly promoted endothelial tube formation, increasing total tube length, junction number, and mesh formation. Conclusions: WJ-MSCsec stimulates EnSC proliferation and migration while enhancing angiogenesis in vitro. WJ-MSCsec represents a promising cell-free therapeutic strategy for endometrial regeneration and reproductive disorders associated with impaired endometrial function.