Since the first in vitro fertilization (IVF) attempts in the mid-1970s, researchers have been working on developmental approaches to improve infertility outcomes. A woman undergoes a decline with age in the number and quality of her oocytes. These aged oocytes also show genetic abnormalities such as aneuploidies [1]. Supportive treatments are recommended to these patients which may include antioxidants, vitamins or coenzyme Q10 [2]. However, clinical data on these supplementation methods are controversial [3]. Thus, new methods are being investigated to address age factor infertility, as well as insufficient endometrial growth or other indications that result in poor outcomes in assisted reproduction treatments (ART).

Platelet rich plasma (PRP), applied as an intrauterine infusion by Chang et al. [4] in 2015, is one of the novel advances for poor endometrial response to standard hormone replacement therapy. Subsequently, many clinical studies on PRP for female infertility have been conducted, most of which are encouraging. It has been performed for premature ovarian failure or insufficiency (POI), poor ovarian response, and poor oocyte and/or embryo quality. These indications represent patients with “poor prognosis” for ART.

PRP is commonly described as the blood plasma which contains high concentrations of platelets [5], approximately 4–5 times greater than in the circulating blood. The physiological processes involved in the platelet-mediated tissue repair comprise both adherence and aggregation around the injured area to form thrombin and fibrin, and the release of substances that promote angiogenesis and inflammation, such as platelet derived growth factor (PDGF), transforming growth factor beta (TGF-$\beta$), vascular endothelial growth factor (VEGF), as well as cytokines like platelet factor 4 (PF4) [6]. These growth factors are essential in fibroblast and leukocyte activation, and in proliferation and/or migration of various cell types to the site of injury. In addition, platelet derived factors have been shown to induce endometrial progenitor cell activity [7] and promote stromal cell proliferation [8].

PRP has given hope to patients with endometrial insufficiency, ovarian insufficiency, perimenopausal or menopausal women, and poor responders to ART. Ovarian rejuvenation following PRP application was introduced by Pantos et al. [9] at the 2016 ESHRE conference. They reported successful ovarian rejuvenation 1–3 months after PRP therapy. In 2018, Sills et al. [6] reported the first data on in vitro fertilization and blastocyst formation after intraovarian injection of autologous platelet rich plasma. This was followed by the case series of Sfakianoudis et al. [10], which included 3 patients with increased levels of anti-mullerian hormone (AMH) and reductions in follicle stimulating hormone (FSH), and achieved pregnancy in all three patients. Current research on the use of PRP in female infertility aims to improve deteriorating hormonal profiles, as well as enabling gamete production and implantation of the embryo into the endometrium. However, this treatment is an “add-on” therapy performed prior to the standard methods of IVF treatment.

The present study focuses on the outcomes of PRP administration into the ovaries or endometrium of women undergoing IVF. The aim of this paper is to review the literature and evaluate the effect of PRP on the outcomes of subsequent ART cycles in infertile women with poor ovarian reserve, ovarian insufficiency or repeated implantation failures due to endometrial problems.

Different methods of PRP preparation have been described in the literature, all of which aim to obtain the highest number and purity of platelets as a layer, following centrifugation steps.

15–50 mL of blood were collected from the antebrachial vein into tubes which were then centrifuged at rotation speeds ranging from 270 g to 1500 g for periods ranging from 5 to 10 minutes. The layers formed were separated according to the method of each laboratory or according to the instructions of the manufacturer whenever ready-to-use kits were used. In various methods, centrifugation was repeated following the separation procedure. In some techniques, calcium including additives were used to activate the mixture. The prepared solution was then infused into the uterine cavity or injected into the cortex of each ovary using aspiration needles or infused into the uterine cavity [4, 6, 10, 11, 12, 13, 14], according to the need of each patient (Fig. 1).

Fig. 1.

Schematic representation of PRP preparation and application.

Platelets are the elements of blood which play important role in hemostasis at situations of vascular injury. The process starts with adherence and aggregation of the platelets forming a procoagulant surface at the injury site, and subsequent thrombin and fibrin generation. However, another important role of the platelets is to release substances that promote tissue repair and mediate angiogenesis and inflammation. They secrete cytokines such as platelet-derived growth factor (PDGF), transforming growth factor beta (TGF-$\beta$), vascular endothelial growth factor (VEGF), platelet factor 4 (PF4) and CD40L. These growth factors play an important role in fibroblast and leukocyte activation and proliferation and/or migration of various cell types to the injury site. Furthermore, platelet-derived factors induce endometrial progenitor cell activity [7] and promote stromal cell proliferation [8].

Following the first publication by Kingsley et al. in 1954 [15] and the first therapeutic application by Levin et al. in 1964 [16], PRP has been used in different fields of medicine such as dermatology, neurology, dentistry, plastic surgery and musculoskeletal system disorders. Animal studies were conducted in order to better understand the in vivo outcomes, which have shown significant improvements in leukocyte infiltration, inflammatory response, cell proliferation, and tissue regeneration [17, 18]. As the role of growth factors in tissue regeneration is better understood [19], PRP has gained more interest.

The systematic review of Kaur et al. [20] briefly explained the role of PRP administration in different conditions within the field of gynecology, reproductive endocrinology and infertility. According to the studies involved in that review, PRP was demonstrated to be used in gynecological disorders such as cervical ectopy, vulvar dystrophy, wound healing after caesarian section, in urogenital disorders such as genital fistulas, urinary incontinence, and in reproductive medicine such as premature ovarian failure (POF), ovarian torsion, refractory endometrium and repeated implantation failure (RIP), and was shown to be related to faster wound healing, decreased post-operative pain and reduced fever rate.

The ovaries and endometrium are the two main targets of PRP exposure in the treatment of female infertility, as two important steps in successful conception are the formation of the oocytes and the implantation of the embryo into the uterus.

In assisted reproduction, various methods are used to prepare the endometrium for implantation in both fresh and frozen-thawed embryo transfer cycles. Some embryo transfer procedures may be cancelled or delayed due to poor endometrial thickness, which has generally been defined as less than 7 mm [21, 22]. Extended estrogen treatment and adjuvant therapy such as low dose aspirin or vaginal Sildenafil have been used [23], however, a consensus is not yet agreed.

Studies regarding the effect of PRP application on assisted reproduction are summarized in Table 1 (Ref. [4, 11, 12, 14, 24, 25, 26]). The first application of PRP as an intrauterine infusion in order to improve endometrial thickness was by Chang et al. [4], on women who had insufficient endometrial thickness and showed no response to conventional therapy. PRP induced endometrial growth in all 5 patients involved, and 4 achieved pregnancy.

The study of Zadehmodarres revealed similar outcomes. This study was performed on 10 patients with a history of cancelled cycles due to inadequate endometrial growth (less than 7 mm). Endometrial thickness was shown to increase 48 h after the first PRP and to reach more than 7 mm thickness after the second PRP in all patients. Five patients out of ten were observed to be pregnant, and in four, the pregnancy progressed normally [11].

Likewise, in the randomized clinical study of Eftekhar et al. [12] which included 83 patients with poor endometrial response to standard hormone replacement therapy (endometrial thickness 7 mm), endometrial thickness of the study group was found to be significantly higher compared to the control group following PRP infusion. Implantation and clinical pregnancy rates were significantly higher in the study group as well.

In 2019, Kim et al. [24] enrolled 24 women with 2 or more filed IVF cycles and refractory thin endometrium with a 7 mm thickness. In their prospective interventional study, both endometrial thickness, and pregnancy and implantation rates were found to be significantly increased following intrauterine infusion of autologous PRP. Coksuer et al. [25] performed intrauterine PRP in 34 patients who had suboptimal endometrial lining and unexplained infertility and demonstrated a significant improvement in both endometrial thickness 48 hours after PRP application, and in the clinical pregnancy rate.

A total of 123 patients with a history of more than 2 failed IVF cycles were included in the retrospective cohort study of Mehratza et al. [26], 67 of whom were included in the PRP group, and the remaining 56 were included in the Granulocyte Colony Stimulating Factor (GCSF) group. The clinical pregnancy rate was observed to be significantly higher in the PRP group (p 0.05).

Sills et al. [6] reported the first data on in vitro fertilization and blastocyst formation after intraovarian injection of autologous platelet rich plasma, which was followed by the case series of Sfakianoudis et al. [10] which included 3 patients with increased levels of anti-mullerian hormone (AMH) and reduced follicle stimulating hormone (FSH), and achieved positive pregnancies in all three patients.

Four pilot studies were conducted in the Genesis Athens Clinic in order to assess the clinical efficacy of PRP [27]. They were designed as prospective observational cohort studies. Patients were classified into four categories according to their diagnosis: premature ovarian response (POR), premature ovarian insufficiency (POI), perimenopause and menopause.

Anti-mullerian hormone (AMH), antral follicle count (AFC) and oocyte yield were addressed as the primary outcome measures in the POR study, restoration of menstrual cycles and follicle stimulating hormone (FSH) levels were main outcomes for the POI perimenopausal and menopausal studies. Among the patients with POR, significant improvement was observed in both the ovarian reserve status, demonstrated by FSH levels which dropped by 33% (p 0.001), and the ICSI outcomes (p = 0.03). Among the patients with POI, menstruation recovery was observed in 18 out of 30, and a statistically significant improvement was observed in the levels of AMH, FSH and AFC, which confirmed the authors’ previous findings. Thirteen out of 30 patients were reported to respond positively to PRP treatment. Menstruation regularity, improved hormonal levels and AFC were reported for 24 out of 30 perimenopausal women. The authors concluded that PRP infusion yielded promising results for treating ovarian insufficiency. The increase in serum AMH levels were statistically highly significant, with p values of less than 0.0001 in all groups. Melo et al. [14] have also found a significant increase in serum AMH with PRP infusion (p value 0.001).

The studies of Cakiroglu et al. and Sills et al. [6, 13] revealed significantly increased levels of AMH following intra-ovarian PRP infusion (p 0.01 and p = 0.0016, respectively).

Melo et al. and Sills et al. [6, 14] have shown significant reductions in serum FSH levels (p = 0.001 and p 0.0001, respectively), while the FSH reduction in the study of Sfakianoudis et al. [27] was observed in all groups except women with poor ovarian reserve. However, the reduction observed in the study of Cakiroglu et al. [13] was not statistically significant (p = 0.87).

The studies of Sfakianoudis et al., Melo et al. and Cakiroglu et al. [13, 14, 27] revealed statistically significant increases in antral follicle count (p 0.01 in all three studies).

These four major studies, which included 663 subfertile women, were systematically reviewed by Panda et al. [28]. Regarding the post-PRP Intracytoplasmic sperm injection (ICSI) outcomes, the total number of retrieved oocytes, mature oocytes, number of fertilized oocytes, number of cleavage stage embryos and cancellation rate were significantly better in the study of Sfakianoudis et al. [27], when compared to the previous ICSI cycle as control. The number of good-quality embryos was also higher, though not significantly so.

In the study of Melo et al. [14], the total number of retrieved oocytes, the fertilization rate and the number of good-quality embryos were significantly higher after PRP, compared to the control group.

Autologous PRP has become a non-surgical option to improve a wide range of medical situations. Current research on the use of PRP in female infertility aims to improve the deteriorating hormonal profile, as well as enable gamete production and implantation of the embryo into the endometrium. According to the reported outcomes of the above-mentioned studies, this method can enhance the pregnancy potential of a patient especially in the subfertile and infertile groups. Moreover, the risks of immunological reaction or transmission of infectious diseases are minimal since PRP is prepared from autologous blood samples. The risks of PRP therapy potentially include infection, bleeding, and nerve damage but appear to be minimal.

As a result, it may be concluded that PRP can be used as an “add-on” therapy in patients with diminished ovarian reserve prior to the IVF cycle. This is a safe and easy-to-apply method although it is still considered an empirical treatment method. Further studies with a randomized design and larger sample size should be conducted in order to better understand the effect on outcomes in female infertility.

PK and SK developed the original idea and wrote the manuscript. OK conducted the literature search and prepared the manuscript. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript.

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This research received no external funding.

The authors declare no conflict of interest. Seda Karabulut is the Guest Editor of this journal, given her role as Guest Editor, had no involvement in the peer-review of this article and has no access to information regarding its peer-review.