Circulating pregnancy hormone relaxin as a first trimester biomarker for preeclampsia.

OBJECTIVE: Preeclampsia, a multi-system hypertensive disorder, is associated with perturbations in the maternal cardiovascular system during early pregnancy. The corpus luteal hormone relaxin, a potent vasodilator, may contribute to physiological circulatory changes especially in early gestation when circulating levels are highest. This study investigated whether first trimester circulating relaxin may be a suitable biomarker for the early prediction of preeclampsia. METHODS: Relaxin was initially measured in first-trimester samples of women who developed late-onset preeclamptic (LO-PE; delivery ≥ 34 weeks; n = 33) and uncomplicated pregnancies (n = 25) in Pittsburgh, USA. Subsequently, to expand the group numbers, relaxin was measured in women who developed LO-PE (n = 95), early-onset preeclamptic (EO-PE; delivery < 34 weeks; n = 57), and uncomplicated pregnancies (n = 469) in Utrecht, the Netherlands. RESULTS: In the Pittsburgh subjects, low relaxin levels (lowest centile:

Commercial immunoassays for human relaxin-2.

Several different immunoassays have been used in the commercial pharmaceutical development of serelaxin. These assays have been well validated for submission of GLP preclinical and clinical studies to the FDA and EU regulatory bodies. The requirements for these assays exceed that of most research assays commonly developed in academic research but have been and are currently available to academic researchers. Additionally, many human relaxin immunoassays are commercially available from a variety of vendors. Validation procedures for immunoassays are well understood and documented, however validation of these assays is often lacking or completely absent. The data derived from these assays must be questioned if the investigator does not supply information on the validation of the assay used, either from the supplier or through their own efforts. Many recent papers on determination of serum relaxin in clinical settings have recently been published. The assay used for this determination varies but generally is one of two commercially available. These manuscripts and the assay used is discussed. Direct comparisons of assays are lacking but some general conclusions can be drawn by comparing results from similar studies using different assays. There is disagreement among the results of the concentrations of serum relaxin from the use of different assays that raise questions on assay reliability. The differences in the quality of immunoassays used for detection of serum relaxin should be part of the decisions making process in choosing an assay. While the end user bears the ultimate responsibility to demonstrate the assay is valid for the stated claims, reviewers and editors also share responsibility for quality of published results.

Primate preimplantation embryo is a target for relaxin during early pregnancy.

OBJECTIVE: To determine whether preimplantation embryos are targets for relaxin secreted from the corpus luteum of the menstrual cycle. DESIGN: Rhesus monkey oocytes obtained from females undergoing controlled ovarian hyperstimulation were inseminated, and the resulting embryos were cultured in medium with or without recombinant human relaxin (20 ng/mL) for 8 days. SETTING: Research laboratory. ANIMAL(S): Rhesus monkey. INTERVENTION(S): Controlled ovarian stimulation to obtain oocytes for in vitro-produced embryos that were cultured with or without human recombinant relaxin. MAIN OUTCOME MEASURE(S): Rate of blastocyst development, percentage of blastocysts, and inner cell mass/trophectoderm cell ratio were measured on day 8 of culture. The presence of relaxin receptor (RXFP1) messenger RNA in eight-cell embryos was observed by array hybridization. RESULT(S): RXFP1 receptor expression was localized to the inner cell mass of blastocysts, as shown by immunohistochemistry. The percentage of embryos that developed to blastocyst and the inner cell mass/trophectoderm cell ratio was unchanged with relaxin supplementation; however, the relaxin-treated embryos developed into blastocysts significantly sooner than untreated embryos. CONCLUSION(S): These results are the first evidence that the preimplantation primate embryo is a target for relaxin and that the addition of relaxin to in vitro culture medium enhances rhesus monkey embryo development.

Trends in serum relaxin concentration among elite collegiate female athletes.

PURPOSE: This study was designed to investigate the relationship between serum relaxin concentration (SRC) and menstrual history and hormonal contraceptive use among elite collegiate female athletes. Evaluation of SRC in athletes is necessary, because relaxin has been associated with increased knee joint laxity and decreased anterior cruciate ligament (ACL) strength in animal models. METHODS: National Collegiate Athletic Association Division I female athletes participating in sports at high risk for ACL tears - basketball, field hockey, gymnastics, lacrosse, soccer, and volleyball - were invited to participate. All participants completed a questionnaire about their menstrual history and hormonal contraceptive use. Venipuncture was performed to obtain samples of serum progesterone and relaxin. Samples were obtained during the mid-luteal phase from ovulating participants, and between the actual or projected cycle days 21 to 24, from anovulatory participants. Serum concentration of relaxin and progesterone was determined by ELISA and the data were analyzed using SPSS statistical software with significance set at P = 0.05. RESULTS: 169 female athletes participated. The mean SRC among all participants was 3.08 ± 6.66 pg/mL). The mean SRC differed significantly between those participants using hormonal contraceptives (1.41 pg/mL) and those not using hormonal contraceptives (3.08 pg/mL, P = 0.002). Mean SRC was lowest among amenorrheic participants (1.02 pg/mL) and highest among oligomenorrheic participants (3.71 pg/mL) and eumenorrheic participants (3.06 pg/mL); these differences were not significant (P = 0.53). Mean serum progesterone concentration (SPC) differed significantly between those participants using hormonal contraceptives (2.80 ng/mL), and those not using hormonal contraceptives (6.99 ng/mL, P < 0.0001). CONCLUSIONS: There is a positive correlation between serum progesterone and SRC and an attenuation of SRC with hormonal contraceptive use. Our results underscore the significant role that hormonal contraceptives can play in decreasing relaxin levels, if future investigations establish a link between relaxin levels and ligamentous injury among female athletes.

Scar prevention and cosmetically enhanced wound healing using relaxin.

Relaxin has previously been tested in rodent wound healing models and been shown to promote angiogenesis and to speed healing. However, pigs have been shown to be a better model for human skin in dermatology studies, so juvenile pigs were selected for a study of scar reduction and cosmetic appearance. Twelve 20- by 6-mm excisional wounds were created on the backs of all animals. Topical formulations of relaxin with 0, 0.5, or 2.5 mg/mL were applied twice daily for weeks 2-3 and then daily for weeks 3-6 in all animals. In addition, some animals received systemic relaxin, which was administered via infusion pumps at a rate of 125 microg/kg of body weight/day. Assessments of healing and cosmetic appearance were made by a dermatologist at weeks 2, 4, and 6. Wound sites were collected at 6 weeks and evaluated histologically for granulation tissue, inflammation, and collagen organization. Wounds in animals receiving systemic relaxin had an improved appearance with less redness, reduced granulation tissue, and lower amounts of inflammation. They showed a more-well-knit collagen structure compared to controls. Wounds treated with topical formulations did not show improvement over controls. The topical formulation used was found to have a short residence time, which likely limited penetration of relaxin. Reformulated relaxin preparations with improved penetration might be useful as a topical treatment for wounds to prevent or reduce scarring.

Hourly human chorionic gonadotropin secretion profiles during the peri-implantation period of successful pregnancies.

OBJECTIVE: To characterize the hourly profiles of hCG secretion in blood during conceptive cycles that ended in successful pregnancy. DESIGN: Prospective study. SETTING: University fertility clinic and research laboratories. PATIENT(S): Healthy spontaneously ovulating women with regular menses, no history of infertility, and either no male partner or an azospermic partner. INTERVENTION(S): Frequent blood samples were collected daily from 11 spontaneously ovulating women during 11 cycles of artifical insemination with donor semen. The concentrations of hCG, LH, and FSH were measured in the blood by immunoassay. MAIN OUTCOME MEASURE(S): The concentration of hCG in the frequent blood samples and the rate that the concentration of hCG changed during the period of frequent sampling. RESULT(S): For the conceptive cycles resulting in successful pregnancies analyzed, hourly hCG concentrations were observed to increase in a consistent nonpulsatile manner. CONCLUSION(S): These data provide the first characterization of the hourly secretion profile of hCG in early pregnancy as well as provide further evidence that individual daily blood samples are sufficient for the accurate assessment of pregnancy.

Use of relaxin in orthodontics.

BAS Medical is investigating the use of relaxin to improve ortho-dontic treatments. Relaxin is well known for its effects on remodeling soft tissue, and we believe relaxin will be clinically useful in speeding tooth movement and preventing relapse. We investigated the use of relaxin in preventing relapse in a dog model. Dog maxillary second incisors were orthodontically rotated an average of 42 degrees, and then relaxin was administered by gingival injection to relieve the rotational memory in the connective tissues. Teeth were retained for 30 days to allow fibers to reform. Teeth then were released and relapse was measured by a series of impressions. Animals receiving relaxin gingival injections (n = 8) were compared with placebo-treated animals (n = 8) (exhibiting high relapse) and gingival fiberotomies (n = 8) (low relapse). Gingival fiberotomy is a surgical procedure to cut the gingival connective tissues away from the tooth and has been shown to be effective in preventing relapse clinically and in animal models. There was a significant difference in relapse between the fiberotomy and the placebo control groups, and the relaxin-treated group had an intermediate response between the two groups (nonsignificant). Dose and treatment optimization may improve the response in future studies. To study the underlying mechanisms, we have localized relaxin receptors on gingival and periodontal ligament fibroblasts in tissue slices and cell cultures. Relaxin was found to stimulate collagenase production by relaxin in human gingival fibroblast cultures. Taken together, the data support a role for relaxin therapy to speed tooth movement and prevent relapse in orthodontic practice.

Does human relaxin accelerate orthodontic tooth movement in rats?

Human relaxin was administered to young rats through either minipumps (group P) or subcutaneous injections (group I). Control rats received pump implants containing placebo (group C). Day 0 was the day of orthodontic appliance placement and activation to pull bilateral upper first molars forward, and day 14 was the end time point. Cephalometric radiographs (three repeated exposures) were taken at 0, 3, 5, 7, 10, and 14 days. The total length of three maxillary molar segments and the space between the first and second molars were measured under a dissecting microscope postmortem. Both groups P and I showed rapid tooth movement at day 3. Movement slowed, but it still increased gradually in group P while decreasing in group I after that. Concurrent tooth lateral drifts to the buccal side were smaller in both groups P and I. The length and space were larger in both groups P and I. Thus, administration of human relaxin may accelerate the early stages of orthodontic tooth movement in rats.

Secretion and excretion of human chorionic gonadotropin during early pregnancy.

OBJECTIVE: To characterize the profiles of human chorionic gonadotropin (hCG) secretion in blood and its subsequent excretion in urine during conceptive cycles that ended in successful pregnancy and in spontaneous abortion. DESIGN: A prospective study. SETTING: University fertility clinic and research laboratories. PATIENT(S): Healthy, spontaneously ovulating women with regular menses, no history of infertility, and either no male partner or an azoospermic partner. INTERVENTION(S): Blood and urine samples were collected daily from 63 spontaneously ovulating women during 167 cycles of artificial insemination (AI) with donor semen; hCG concentrations were measured in blood and urine, and luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations were measured in blood by immunoassay. MAIN OUTCOME MEASURE(S): Fecundity, the day of ovulation, the day of hCG detection, and the concentration of hCG on the day of detection in blood and urine. RESULT(S): In 62 conceptions detected, 14 resulted in clinical spontaneous abortion (CAB) and 8 resulted in early pregnancy loss (EPL). When successful pregnancies and pregnancy losses were compared, no significant differences existed between the days of hCG appearance in serum or in urine, the concentrations of hCG on the day of detection, or the incremental change in hCG concentration on the day of detection. CONCLUSION(S): These data validate the use of urinary hCG as a biomarker for assessing peri-implantation pregnancy events.