P-506 Administration of low molecular weight heparin alleviate immune physiology in recurrent implantation failure modulating CCL2-CCR2 axis during frozen embryo transfer: effort from clinic to bench
Authors: Kalapahar S , Sharma S , Chattopadhyay R , Mitra I , Ghosh S , Dam M , Chaudhury K , Chakraborty P 
Published: June 2023

Abstract

Study question
Does low molecular-weight heparin (LMWH) administration modulate CCL2-CCR2 axis in recurrent implantation failure (RIF) patients undergoing frozen embryo transfer (FET) to improve pregnancy salvage?

Summary answer
LMWH treatment attests beneficial immunological tolerance in vivo and in vitro through modulation of CCL2-CCR2 axis suggesting possible restoration of weak pro-inflammatory response in RIF.

What is known already
Immune imbalance in proportion of activated macrophages (M1) and alternatively activated macrophages (M2) impede endometrial receptivity and contribute to RIF. CCL2 (M2-asscociated) - CCR2 (t-helper-2 associated) axis orders macrophage polarization by influencing expression of functionally relevant and polarization associated genes and down-modulate pro-inflammatory cytokine production. Immunological effects of LMWH regulate pregnancy-promoting processes at foetal-maternal interface to provide an appropriate implantation process; outcomes being controversial. We aim to investigate the potential immunoregulatory properties of LMWH in patients with RIF undergoing FET, with particular regard to effects on macrophages and T-helper (Th) cells; two key players in promoting immune tolerance during pregnancy.

Study design, size, duration
This prospective cohort study constituted 121 women with RIF (≥3 failed embryo transfer) undergoing FET at Institute of Reproductive Medicine between January to October 2022. An incremental dose (4-12mg/day) of estradiol with (Group A; n = 62) or without (Group B; n = 59) LMWH (40 mg/day) from d2 to d12 with sequential ultrasound following intra-muscular progesterone (100mg/day) for 4 days was administered in all participants. Blood samples were collected to isolate plasma and peripheral-blood-mononuclear-cells (PBMCs).

Participants/materials, setting, methods
Monocytes were purified from PBMCs and cultured with GM-CSF or M-CSF to analyze factor/s which control CCL2-CCR2 expression along macrophage polarization by flow cytometry. Influence of CCL2 on GM-CSF-cultured macrophages (GM-MØ) and M-CSF-cultured macrophages (M-MØ) specific gene markers was analysed using quantitative RT-PCR (qRT-PCR). To assess immunological effects of LMWH in-vivo, Th-specific cytokine profile/s and respective chemokines were measured from plasma by Luminex xMAP technology. Statistical significance was set at p &lt; 0.05.

Main results and the role of chance
The clinical pregnancy rate was higher in group A. (A vs B: 37.09% vs. 27.11%, p = 0.24). LMWH exposure significantly decreased the secretion of CCL2 (p &lt; 0.01) and CCL22 (p &lt; 0.001) in GM-CSF-cultured macrophages, while it increased CCL2, CCL20 production (p &lt; 0.001) in both GM-MØ and M-MØ. However, expression of CCL7 was significantly lower (p &lt; 0.01) in M-MØ and GM-MØ generated from CD14+ CD16+ monocytes and CD14 ++ CD16- monocytes respectively under LMWH exposure. qPCR analysis revealed a significant increase (p &lt; 0.01) in the expression of various GM-MØ–specific genes including EGLN3, and SERPINE1 in macrophage supernatant post LMWH treatment. Expression of various M-MØ-specific marker/s such as IGF1, FOLR2, and HTR2B, is significantly up-regulated (p &lt; 0.01) in Group B. Group A, although documented a decreased concentration/s (pg/ml) of Th17-type cytokine/s (IL-6 (1.88 ± 0.65 vs. 0.91 ± 0.43; p &lt; 0.04 and IL-23 (17.94 ± 9.76 vs. 7.78 ± 3.43; p &lt; 0.01)), at end of treatment, concentration of TGF-β was significantly higher (3909.05 ± 1248.35 vs. 2469.83 ± 1058.71; p &lt; 0.01) which cue to probable maintenance in balance of inflammatory response at the time of implantation. No differences were observed in Th1-type cytokine level/s (IFN-γ and TNF-α). CXCL10, CXCL11, CXCL1, CXCL8, CCL17, CCL22 do not differ in vivo.

Limitations, reasons for caution
Beneficial effects of LMWH administration with a good sample size are clearly needed to confirm this hypothesis; hence result/s should be dealt with caution. Further to this, inclusion of other arm/s (corticosteroids, intralipid and/or intravenous immunoglobulin) will make the study much robust and conclusive.

Wider implications of the findings
The identification of atypical Th1-associated pro-inflammatory effects of LMWH drives to evaluate modulation of CCL2 expression to limit or potentiate macrophage activation in RIF; especially where anticoagulant effect is not the primary goal. Further, modification of cytokine expression/s might potentiate novel strategy derived from deregulated macrophage polarization.

Trial registration number
Not Applicable