Intraovarian platelet-rich plasma: current status

The successful use of PRP in regenerative medicine has led investigators to study its effect in the treatment of conditions like decreased ovarian reserve, poor responders, and premature ovarian insufficiency. To review the uses of intraovarian PRP in reproductive medicine. A literature search for English articles related to the uses of intraovarian PRP in reproductive medicine, including articles published in PubMed, from 2000 to April 2021. Seventeen studies: No RCT. Studies were classified according to indication. (1) For diminished ovarian reserve: 6 studies including 369 patients. (2). For poor responders: 3 case series studies including 41 patients with an improvement in ovarian response. (3) For premature ovarian insufficiency: 8 studies including 373 patients. Ovarian reserve markers were the outcome of all studies with conflicting results. LBR was not determined in the majority of studies. Intraovarian PRP for diminished ovarian reserve, poor ovarian response, or POI is still experimental. Well-designed, large RCTS to confirm its efficacy and safety are required.


Background
Preparation of platelet-rich plasma (PRP) is simple and easily performed. PRP contains high concentrations of cytokines and growth factors. Mechanisms of action are attributed to the high concentration of growth factors inducing tissue regeneration and healing. The fibrin frameworks present over platelets support the regenerative matrix leading to the rapid establishment of the proper morphological and molecular configuration for wound healing [1]. Platelet activation by thrombin, calcium chloride, or collagen is required to trigger the release of these growth factors.

Objective
To review the uses of intraovarian PRP in reproductive medicine.

Methods
A literature search for English articles related to the uses of intraovarian PRP in reproductive medicine, including articles published in PubMed, from 2000 to April 2021.

Procedure
Different protocols are available for PRP preparation and different types of kits available in the market by various manufacturers, each claiming theirs' are superior [2]. Generally, all protocols involve the collection of blood, centrifuge the sample (either single or double centrifuge), subjecting it to temperature or not, and activating the platelets with exogenous factors or without it. Procedures differ in the volume of blood collected, force and duration of centrifugation, single step or two steps centrifugation, and the resulting volume of platelets. The concentration of platelets also varies depending upon the protocols used Intraovarian PRP administration was performed at the end of the period. It can be performed vaginally where minimal sedation is required. Injection is done under direct transvaginal ultrasound guidance, using an oocyte pick-up needle (17-gauge), slowly and steadily to ensure uniform distribution of infusion in all layers and the needle is gently retracted while injecting. Three punctures per ovary, intramedullary injection and diffusion in the subcortical layers [3]. The amount injected into each ovary was 2 mL [4], 4 ml [5], 5 mL [6]. After the procedure, the patient was kept in the supine position for 10-15 min and rest for 1 h. The procedure was repeated every month for 2-3 months. Some authors performed intraovarian PRP injection through laparoscopy [7].

Results
Seventeen studies were found; they were classified according to indication. (1) For diminished ovarian reserve ( Table 1): 6 studies, 3 case series, 2 observational, and 1 controlled non-randomized studies. The total number of patients was 369 patients. Improvement in ovarian reserve markers was detected in all studies. (2) For poor responders (  [18] included 2 groups: group 1: POI: amenorrhea and FSH > 40.0 mIU/mL. Affected women may, however, still have sporadic menses and may even occasionally achieve spontaneous pregnancy; and group 2: premature ovarian aging (POA), also called occult primary ovarian insufficiency (oPOI): a milder form of ovarian insufficiency, characterized by abnormally high FSH (≤ 40.0 mIU/mL) and abnormally low age-specific AMH. No changes in E2 or FSH levels were found in group 1. No significant difference in FSH or LH was detected in the study of Aflatoonian et al. [15].

Discussion
The successful use of PRP in regenerative medicine has led investigators to study its effect in the treatment of conditions like decreased ovarian reserve, poor responders, and premature ovarian insufficiency [20]. PRP comprises many soluble mediators which coordinate cellular repair after tissue injury [21]. Closely linked to inflammatory signaling, PRP is also involved in tissue regeneration, cell proliferation, extracellular matrix remodeling, apoptosis, differentiation, and angiogenesis. Platelets play an important role in local tissue repair. Intraovarian PRP was performed based on the theory that degenerative processes lead to ovarian insufficiency through molecular pathway dysfunction, which regulates the ovarian vascularization. Some investigators believe that poor ovarian response could be treated by resourcing nutrients and hormonal supply [4,5]. It is supposed that platelet-derived factors may promote ovarian angiogenesis and stimulate follicular development by recovering the ovarian microenvironment [5]. PRP contains a high concentration of cytokines and growth factors such as insulin-like growth factor, vascular endothelial growth factor, a platelet-derived angiogenic factor, and interleukin-8. These factors have an important role in tissue regenerative and healing, which is supposed to restore folliculogenesis and ovarian hormonal profile after intraovarian injection.
The paradigm that the mammalian ovarian reserve is fixed at birth which declines until exhaustion [22]. Oocyte stores are limited, non-renewable and no evidence for neo-oogenesis in adult monkey stem cells. It may be possible to replenish the ovarian follicle pool due to the presence of a population of oogonial stem cells (OSC) in adult ovaries that may be activated under specific circumstances [23]. However, spontaneous reactivation of OSCs is not yet believed to occur naturally in vivo in the adult human ovary. Although data from animal models  (Table 1). No RCT and the total number of patients in all studies is small. Ovarian reserve markers (increase in serum AMH or antral follicle count or decrease in serum FSH) were the outcome in all studies with a beneficial effect in all except Singh et al. 2020 [8,9] who found no benefit. LBR was not determined in all studies. Pregnancy rate was determined in Petryek et al. [8] and Mello et al [10] studies, with significant improvement, but the number of patients was small, 38 patients and 46 patients, respectively. Therefore, intraovarian PRP for improvement of ovarian reserve cannot be recommended due to the absence of robust evidence and well-designed, large RCTS are required to confirm its efficacy and safety. For poor responders (  [16] found that women who did not have an antral follicle at the time of PRP injection were less likely to respond to treatment compared to those who had one or two antral follicles. Similarly, women with the lowest quartile for serum AMH and the highest for serum FSH were less likely to respond. They concluded that PRP may help to activate existing preantral and/or early antral follicles and that the number of remaining follicles in the ovaries of women with POI likely determines the extent of their response. However, currently, we cannot generalize this finding and there is an obvious need for future well-controlled studies to identify the subpopulation that can get the maximum benefit from PRP infusion.  Barad et al. study [18] included 2 groups: group 1: POI: amenorrhea and FSH > 40.0 mIU/mL. Affected women may, however, still have sporadic menses and may even occasionally achieve spontaneous pregnancy and group 2: Premature ovarian aging (POA), also called occult primary ovarian insufficiency (oPOI): a milder form of ovarian insufficiency, characterized by abnormally high FSH (≤ 40.0 mIU/mL) and abnormally low age-specific AMH. No changes in E2 or FSH levels were found in group1. No significant difference in FSH or LH was detected in the study of Aflatoonian et al. on 9 patients with POI [15]. Therefore, we have conflicting results regarding the use of intraovarian PRP for POI. In most of the studies, pregnancy characteristics, such as clinical pregnancy rate, miscarriage rate, chemical pregnancy rate, and live birth rate have not been evaluated. Only a few studies have evaluated the ICSI cycle performance. Lastly, most of the included studies are quasiexperimental studies and not a single RCT is included.

Conclusion
Intraovarian PRP for diminished ovarian reserve, poor ovarian response, or POI is still experimental. There is a need for research on cellular and molecular level to improve our knowledge on PRP mode of action, standardization of PRP preparation methods, and application methods. Well-designed, large RCTS to confirm its efficacy and safety are required. Without strong, unbiased evidence, any intervention is a suspect until proven otherwise.