Pablo A. Casalis

Pre‐eclampsia is not Associated with Changes in the Levels of Regulatory T Cells in Peripheral Blood

The acceptance of the semi‐allogeneic fetus within the maternal environment requires tolerance mechanisms not fully characterized yet. Normal pregnancy is known to be associated with a Th2 profile. Furthermore, regulatory T cells (Tregs) were proposed to regulate the Th2/Th1 balance at early stages of pregnancy. Treg may avoid the shift to a Th1 profile, thus preventing miscarriage. Accordingly, spontaneous abortion is characterized by a Th1 dominance and diminished levels of Treg. The major aim of the present work was to investigate if pre‐eclampsia, a late immunological complication of pregnancy, is characterized by similar hallmarks.

Haem oxygenase-1 dictates intrauterine fetal survival in mice via carbon monoxide

Pregnancy establishment implies the existence of a highly vascularized and transient organ, the placenta, which ensures oxygen supply to the fetus via haemoproteins. Haem metabolism, including its catabolism by haem oxygenase‐1 (HO‐1), should be of importance in maintaining the homeostasis of haemoproteins and controlling the deleterious effects associated with haem release from maternal or fetal haemoglobins, thus ensuring placental function and fetal development. We demonstrate that HO‐1 expression is essential to promote placental function and fetal development, thus determining the success of pregnancy. Hmox1 deletion in mice has pathological consequences for pregnancy, namely suboptimal placentation followed by intrauterine fetal growth restriction (IUGR) and fetal lethality. These pathological effects can be mimicked by administration of exogenous haem in wild‐type mice. Fetal and maternal HO‐1 is required to prevent post‐implantation fetal loss through a mechanism that acts independently of maternal adaptive immunity and hormones. The protective HO‐1 effects on placentation and fetal growth can be mimicked by the exogenous administration of carbon monoxide (CO), a product of haem catabolism by HO‐1 that restores placentation and fetal growth. In a clinical relevant model of IUGR, CO reduces the levels of free haem in circulation and prevents fetal death. We unravel a novel physiological role for HO‐1/CO in sustaining pregnancy which aids in understanding the biology of pregnancy and reveals a promising therapeutic application in the treatment of pregnancy pathologies. Copyright

Blockage of Heme Oxygenase-1 Abrogates the Protective Effect of Regulatory T Cells on Murine Pregnancy and Promotes the Maturation of Dendritic Cells

Regulatory T cells (Treg) play an important role in fetal protection. They expand during normal pregnancy and protect fetal antigens from maternal effector cells. Their effect is associated with the up-regulation of tolerance-associated molecules at the fetal-maternal interface. Among these, Heme Oxygenase-1 (HO-1, coded by Hmox1) is of special importance as its blockage correlates with increased abortion rates and its up-regulation positively affects pregnancy outcome. Here, we aimed to investigate whether the protective effect of Treg is mediated by HO-1 in a mouse model. HO-1 blockage by Zinc Protoporhyrin (ZnPPIX) abrogated the protective effect of Treg transfer. We found that HO-1 is important in maintaining maternal dendritic cells (DCs) in an immature state, which contributes to the expansion of the peripheral Treg population. This brings to light one essential pathway through which Treg mediates the semi-allogeneic fetus tolerance.

The persistence of paternal antigens in the maternal body is involved in regulatory T-cell expansion and fetal-maternal tolerance in murine pregnancy.

Citation Zenclussen ML, Thuere C, Ahmad N, Wafula PO, Fest S, Teles A, Leber A, Casalis PA, Bechmann I, Priller J, Volk H‐D, Zenclussen AC. The persistence of paternal antigens in the maternal body is involved in regulatory T‐cell expansion and fetal‐maternal tolerance in murine pregnancy. Am J Reprod Immunol 2010; 63: 200–208

Intervertebral disc regeneration after implantation of a cell-free bioresorbable implant in a rabbit disc degeneration model

Degeneration of the intervertebral disc is the most common cause of lower back pain. Interestingly, all available treatments are limited to treat the symptoms and not the underlying biologic alterations of the disc. Freeze-dried resorbable non-woven polyglycolic acid (PGA) - hyaluronan implants were used in a degenerated disc disease (DDD) model in New Zealand white rabbits. The constructs were immersed in allogenic serum and implanted into the disc defect. Animals with discectomy only served as controls. The T2-weighted/fat suppression sequence signal intensity of the operated discs as assessed by magnet resonance imaging decreased in both groups one week after the operation compared to a healthy disc. After 12 months the implanted group showed an increase of 51% in the signal intensity compared to the 1-week results whereas the signal intensity in the sham group remained on the same level from one week to 12 months. Histological and quantitative immunohistochemical examination after 12 months indicated cell migration into the defect and showed formation of disc repair tissue. In controls, repair tissue containing type II collagen was not evident. In conclusion, the implantation of polymer-based constructs after discectomy induces tissue regeneration resulting in improvement of the disc water content.

Pregnancy: Tolerance and Suppression of Immune Responses

Presence of foreign tissue in a hosts body would immediately lead to a strong immune response directed to destroy the alloantigens present in fetus and placenta. However, during pregnancy, the semiallogeneic fetus is allowed to grow within the maternal uterus due to multiple mechanisms of immune tolerance, which are discussed in this chapter.

Exploring the potential of low doses carbon monoxide as therapy in pregnancy complications

Heme Oxygenase-1 (HO-1) has been shown to play a pivotal role in pregnancy outcome and its ablation leads to abnormal placentation, intrauterine fetal growth restriction (IUGR) and subsequent intrauterine fetal death. Carbon monoxide (CO) has been found to mimic the protective effects of HO-1 activity, rescuing HO-1-deficient fetuses. This gasotransmitter arises in biological systems during the oxidative catabolism of heme by HO. Here, we explored the potential of CO in preventing IUGR and established the optimal doses and therapeutic time window in a clinically relevant mouse model. We additionally investigated the pathways activated upon CO application in vivo. We established 50 ppmas the best lowest dose of CO necessary to prevent growth restriction being the optimal time frame during days 3 to 8 of mouse pregnancy. CO lead to higher fetal and placental weights and avoided fetal death without showing any pathologic effects. CO breathing further suppressed inflammatory responses, diminished placenta apoptosis and complement deposition and regulated placental angiogenesis. Our results confirm the protective role of the HO-1/CO axis and point this gas as an emerging therapeutic possibility which is worth to further explore.

ORIGINAL ARTICLE: The Persistence of Paternal Antigens in the Maternal Body is Involved in Regulatory T-Cell Expansion and Fetal-Maternal Tolerance in Murine Pregnancy

Citation Zenclussen ML, Thuere C, Ahmad N, Wafula PO, Fest S, Teles A, Leber A, Casalis PA, Bechmann I, Priller J, Volk H‐D, Zenclussen AC. The persistence of paternal antigens in the maternal body is involved in regulatory T‐cell expansion and fetal‐maternal tolerance in murine pregnancy. Am J Reprod Immunol 2010; 63: 200–208

Supporting the hypothesis of pregnancy as a tumor: survivin is upregulated in normal pregnant mice and participates in human trophoblast proliferation.

Problem  Survivin, a tumor‐promoting antiapoptotic molecule, is expressed in the human placenta. Here, we analyzed its expression during normal and pathological murine pregnancy and investigated its participation in human first trimester trophoblast cell survival and proliferation.

Regeneration of nucleus pulposus tissue in an ovine intervertebral disc degeneration model by cell-free resorbable polymer scaffolds.

Degeneration of intervertebral discs (IVDs) occurs frequently and is often associated with lower back pain. Recent treatment options are limited and treat the symptoms rather than regenerate the degenerated disc. Cell‐free, freeze‐dried resorbable polyglycolic acid (PGA)–hyaluronan implants were used in an ovine IVD degeneration model. The nucleus pulposus of the IVD was partially removed, endoscopically. PGA–hyaluronan implants were immersed in autologous sheep serum and implanted into the disc defect. Animals with nucleotomy only served as controls. The T2‐weighted/fat suppression sequence signal intensity index of the operated discs, as assessed by magnetic resonance imaging (MRI), showed that implantation of the PGA–hyaluronan implant improved (p = 0.0066) the MRI signal compared to controls at 6 months after surgery. Histological analysis by haematoxylin and eosin and safranin O staining showed the ingrowth of cells with typical chondrocytic morphology, even cell distribution, and extracellular matrix rich in proteoglycan. Histomorphometric analyses confirmed that the implantation of the PGA–hyaluronan scaffolds improved (p = 0.027) the formation of regenerated tissue after nucleotomy. Disc heights remained stable in discs with nucleotomy only as well as after implantation of the implant. In conclusion, implantation of cell‐free polymer‐based implants after nucleotomy induces nucleus pulposus tissue regeneration and improves disc water content in the ovine model. Copyright