Time-dependent regulation of morphological changes and cartilage differentiation markers in the mouse pubic symphysis during pregnancy and postpartum recovery

Multiparity and Aging Impact Chondrogenic and Osteogenic Potential at Symphyseal Enthesis: New Insights into Interpubic Joint Remodeling

Pregnancy and childbirth cause adaptations to the birth canal to allow for delivery and fast recovery. To accommodate delivery through the birth canal, the pubic symphysis undergoes changes that lead to the interpubic ligament (IpL) and enthesis formation in primiparous mice. However, successive deliveries influence joint recovery. We aimed to understand tissue morphology and chondrogenic and osteogenic potential at symphyseal enthesis during pregnancy and postpartum in primiparous and multiparous senescent female mice. Morphological and molecular differences were found at the symphyseal enthesis among the study groups. Despite the apparent incapacity to restore cartilage in multiparous senescent animals, the symphyseal enthesis cells are active. However, these cells have reduced expression of chondrogenic and osteogenic markers and are immersed in densely packed collagen fibers contiguous to the persistent IpL. These findings may indicate alterations of key molecules in the progenitor cell population maintenance of the chondrocytic and osteogenic lineages at the symphyseal enthesis in multiparous senescent animals, possibly compromising the mouse joint histoarchitecture recovery. This sheds light on the distention of the birth canal and the pelvic floor that may play a role in pubic symphysis diastasis (PSD) and pelvic organ prolapse (POP), both in orthopedic and urogynecological practice in women.

Human adipose-derived stromal/stem cells expressing doublecortin improve cartilage repair in rabbits and monkeys

Localized cartilage lesions in early osteoarthritis and acute joint injuries are usually treated surgically to restore function and relieve pain. However, a persistent clinical challenge remains in how to repair the cartilage lesions. We expressed doublecortin (DCX) in human adipose-derived stromal/stem cells (hASCs) and engineered hASCs into cartilage tissues using an in vitro 96-well pellet culture system. The cartilage tissue constructs with and without DCX expression were implanted in the knee cartilage defects of rabbits (n = 42) and monkeys (n = 12). Cohorts of animals were euthanized at 6, 12, and 24 months after surgery to evaluate the cartilage repair outcomes. We found that DCX expression in hASCs increased expression of growth differentiation factor 5 (GDF5) and matrilin 2 in the engineered cartilage tissues. The cartilage tissues with DCX expression significantly enhanced cartilage repair as assessed macroscopically and histologically at 6, 12, and 24 months after implantation in the rabbits and 24 months after implantation in the monkeys, compared to the cartilage tissues without DCX expression. These findings suggest that hASCs expressing DCX may be engineered into cartilage tissues that can be used to treat localized cartilage lesions.

Decreased Incidence of Rib Fractures in Pregnant Patients After Motor Vehicle Collisions

BACKGROUND

Rib fractures are common after motor vehicle collisions. The hormonal changes associated with pregnancy decrease the stiffness and increase the laxity of cartilage and tendons. The effect of these changes on injury mechanics is not completely understood.

OBJECTIVES

To compare the incidences of chest wall injury following blunt thoracic trauma between pregnant and nonpregnant women.

METHODS

The authors conducted a retrospective review of female patients seen at a level I trauma center from 2009 to 2017 after a motor vehicle collision. Patient characteristics were compared to determine if pregnancy affected the incidence of chest wall injury. Statistics were calculated with SPSS version 24 and are presented as mean (SD) or median (interquartile range).

RESULTS

In total, 1618 patients were identified. The incidence of rib/sternal fracture was significantly lower in pregnant patients (7.9% vs 15.2%, P = .047), but the incidence of intrathoracic injury was similar between the groups. Pregnant and nonpregnant patients with rib/sternal fractures had similar Injury Severity Score results (21 [13-27] vs 17 [11-22], P = .36), but pregnant patients without fractures had significantly lower scores (1 [0-5] vs 4 [1-9], P < .001).

CONCLUSIONS

Pregnant patients have a lower rate of rib fracture after a motor vehicle collision than nonpregnant patients. The difference in injury mechanics may be due to hormonal changes that increase elasticity and resistance to bony injury of the ribs. In pregnant trauma patients, intrathoracic injury without rib fracture should raise concerns about injury severity. A multicenter evaluation of these findings is needed.

Dact1 is expressed during chicken and mouse skeletal myogenesis and modulated in human muscle diseases

Vertebrate skeletal muscle development and repair relies on the precise control of Wnt signaling. Dact1 (Dapper/Frodo) is an important modulator of Wnt signaling, interacting with key components of the various Wnt transduction pathways. Here, we characterized Dact1 mRNA and protein expression in chicken and mouse fetal muscles in vivo and during the differentiation of chick primary and mouse C2C12 myoblasts in vitro. We also performed in silico analysis to investigate Dact1 gene expression in human myopathies, and evaluated the Dact1 protein structure to seek an explanation for the accumulation of Dact1 protein aggregates in the nuclei of myogenic cells. Our results show for the first time that in both chicken and mouse, Dact1 is expressed during myogenesis, with a strong upregulation as cells engage in terminal differentiation, cell cycle withdrawal and cell fusion. In humans, Dact1 expression was found to be altered in specific muscle pathologies, including muscular dystrophies. Our bioinformatic analyses of Dact1 proteins revealed long intrinsically disordered regions, which may underpin the ability of Dact1 to interact with its many partners in the various Wnt pathways. In addition, we found that Dact1 has strong propensity for liquid-liquid phase separation, a feature that explains its ability to form nuclear aggregates and points to a possible role as a molecular 'on'-'off' switch. Taken together, our data suggest Dact1 as a candidate, multi-faceted regulator of amniote myogenesis with a possible pathophysiological role in human muscular diseases.

Peripartum Pubic Symphysis Diastasis-Practical Guidelines

Optimal development of a fetus is made possible due to a lot of adaptive changes in the woman’s body. Some of the most important modifications occur in the musculoskeletal system. At the time of childbirth, natural widening of the pubic symphysis and the sacroiliac joints occur. Those changes are often reversible after childbirth. Peripartum pubic symphysis separation is a relatively rare disease and there is no homogeneous approach to treatment. The paper presents the current standards of diagnosis and treatment of pubic diastasis based on orthopedic and gynecological indications.

Recruitment of monocytes and mature macrophages in mouse pubic symphysis relaxation during pregnancy and postpartum recovery†

Appropriate remodeling of the female lower reproductive tract and pelvic floor is essential during normal mammalian pregnancy, labor, and postpartum recovery. During mouse pregnancy, in addition to reproductive tract modifications, the pubic symphysis (PS) is remodeled into a soft interpubic ligament (IpL) to provide safe delivery of the offspring and fast postpartum recovery. Although temporal changes in the phenotypes of myeloid cells, such as mononuclear phagocytes, are crucial to remodeling the lower reproductive tract organs in preparation for a safe delivery, little is known about the involvement of recruited monocytes or macrophages in mouse PS remodeling. We used combined light microscopy, electron microscopy, and qPCR analysis to investigate the profile of recruited monocytes and macrophage polarization markers in C57Bl6 mouse interpubic tissues during pregnancy (D12, D18, and D19) and early days postpartum (1 dpp and 3 dpp) to better identify their presence in proper remodeling of the mouse PS. Our morphological data show that the number of recruited monocytes is increased in interpubic tissues and that recruited monocytes differentiate into proinflammatory or anti-inflammatory macrophage phenotypes from D18 to 3 dpp, which may contribute to dynamic changes in the gene expression of specific inflammatory mediators involved in interpubic tissue remodeling at these time points. Therefore, our morphological and quantitative gene expression data suggest that both differentiated macrophages from recruited monocytes and polarized macrophages may collaborate for IpL relaxation at labor and the appropriate repair of the PS after the first pregnancy.

Evidence of macrophage modulation in the mouse pubic symphysis remodeling during the end of first pregnancy and postpartum

In mouse pregnancy, pubic symphysis (PS) remodels into an elastic interpubic ligament (IpL) in a temporally regulated process to provide safe delivery. It restores at postpartum to assure reproductive tract homeostasis. Recently, macrophage localization in the IpL and dynamic changes in the expression of inflammatory mediators observed from the end of pregnancy (D18, D19) to early days postpartum (1dpp, 3dpp) highlighted the necessity of the identification of the key molecules involved in innate immune processes in PS remodeling. Therefore, this study uses morphological and high-sensitivity molecular techniques to identify both macrophage association with extracellular matrix (ECM) remodeling and the immunological processes involved in PS changes from D18 to 3dpp. Results showed macrophage association with active gelatinases and ECM components and 25 differentially expressed genes (DEGs) related to macrophage activities in interpubic tissues from D18 to 3dpp. Additionally, microarray and proteomic analysis showed a significant association of interpubic tissue DEGs with complement system activation and differentially expressed proteins (DEPs) with phagocytosis, highlighting the involvement of macrophage-related activities in mouse PS remodeling. Therefore, the findings suggest that PS ECM remodeling is associated with evidence of macrophage modulation that ensures both IpL relaxation and fast PS recovery postpartum for first labor.