Development dependent collagen gene expression in the rat cranial base growth plate

"Osteo-Organogenesis Niche" Hyaluronic Acid Engineered Materials Directing Re-Osteo-Organogenesis via Manipulating Macrophage CD44-MAPK/ERK-ETV1/5-MRC1 Axis

The strategy of re-organogenesis provides an optimal framework for restoring complex organ structures and functions in adult damage. While the focus has often been on restoring organogenesis stem cells, there is limited investigations of reverting the environmental niche to support this approach. The guiding principle of "Nature selects the fittest to survive" drives the intricate dynamic changes in cellular events within the niche environment, especially through immune surveillance. The extracellular matrix (ECM) serves as the "self-associated molecular patterns" of the niche, containing extensive data on cell-niche reaction data and acting as the active tuner of immune surveillance. In this study, hyaluronic acid (HA) is identified as a unique component of the ECM in cranial osteo-organogenesis. Mechanistically, HA activates the Cluster of Differentiation 44 (CD44)-Mitogen-Activated Protein Kinase (MAPK)/Extracellular Signal-Regulated Kinase (ERK)-Ets Variant 1/5 (ETV1/5)- Mannose Receptor C-Type 1 (MRC1) axis in macrophages, establishing a distinct immune surveillance during osteo-organogenesis. Furthermore, HA is utilized as a novel engineered material for an "Osteo-organogenesis niche", restoring immune surveillance and synergistically regulating stem cells to achieve re-osteo-organogenesis in cranial defects of rats. Taken together, the study unveils a previously unknown strategy for leveraging re-organogenesis by utilizing "organogenesis niche" ECM engineered materials to manipulate immune surveillance, thereby comprehensively regulating stem cells and other tissue cells effectively for re-organogenesis.

Reference genes for valid gene expression studies on rat dental, periodontal and alveolar bone tissue by means of RT-qPCR with a focus on orthodontic tooth movement and periodontitis

OBJECTIVES

To obtain valid results in relative gene/mRNA-expression analyses by RT-qPCR, a careful selection of stable reference genes is required for normalization. Currently there is little information on reference gene stability in dental, periodontal and alveolar bone tissues of the rat, especially regarding orthodontic tooth movement and periodontitis. We therefore aimed to identify the best selection and number of reference genes under these experimental as well as physiological conditions.

MATERIALS AND METHODS

In 7 male Fischer344-rats the upper left first and second molars were moved orthodontically for 2 weeks and in 7 more animals additionally subjected to an experimental periodontitis, whereas 7 animals were left untreated. Tissue samples of defined size containing both molars (without crowns) as well as the adjacent periodontal and alveolar bone tissue were retrieved and RNA extracted for RT-qPCR analyses. Nine candidate reference genes were evaluated and ranked according to their expression stability by 4 different algorithms (geNorm, NormFinder, BestKeeper, comparative ΔCq).

RESULTS

PPIB/YWHAZ were the most stabile reference genes for the combined dental, periodontal and alveolar bone tissue of the rat overall, in untreated animals and rats with additional periodontitis, whereas PPIB/B2M performed best in orthodontically treated rats with YWHAZ ranking third. Gene-stability ranking differed considerably between investigated groups. A combination of two reference genes was found to be sufficient for normalization in all cases.

CONCLUSIONS

The substantial differences in expression stability emphasize the need for valid reference genes, when aiming for meaningful results in relative gene expression analyses. Our results should enable researchers to optimize gene expression analysis in future studies by choosing the most suitable reference genes for normalization.

Expression of glutathione peroxidase 1 in the spheno-occipital synchondrosis and its role in ROS-induced apoptosis

BACKGROUND/OBJECTIVE

Chondrogenesis is an integral part of endochondral bone formation, by which the midline cranial base is developed. Reactive oxygen species (ROS) are required in chondrogenic differentiation and antioxidant enzymes regulate their levels. The aim of this study was to localize the antioxidant enzyme glutathione peroxidase 1 (Gpx1) at the spheno-occipital synchondrosis, as well as its effect on ROS challenge and its expression pattern in the course of differentiation.

MATERIALS AND METHODS

Gpx1 was semiquantified in immunohistochemically stained sections of spheno-occipital synchondroses of rats. The effect of Gpx1 on ROS-induced apoptosis was investigated by manipulating the expression of Gpx1 in ATDC5 cells. The temporal pattern of Gpx1 expression was determined during chondrocyte differentiation for 21 days in vitro.

RESULTS

Proliferating chondrocytes exhibited the greatest Gpx1 immunoreactivity and hypertrophic ones the lowest (P = 0.02). Cells transfected with Gpx1-siRNA had the highest apoptotic rate, while cells overexpressing Gpx1 the lowest one (P < 0.001). Gpx1 was significantly increased on days 10 (P = 0.02) and 14 (P = 0.01).

CONCLUSIONS

Hypertrophic chondrocytes have the lowest Gpx1 activity in the spheno-occipital synchondrosis. Gpx1 is implicated in the ROS-induced apoptosis in chondrocytes. Its expression was not constitutive during chondrogenic differentiation.

Effect of excessive methionine on the development of the cranial growth plate in newborn rats

OBJECTIVE

Methionine is an essential amino acid and pivotal for normal growth and development. However, previous animal studies have shown that excessive maternal intake of methionine causes growth restrictions, organ damages, and abnormal growth of the mandible in newborn animals. However, the effect of excessive methionine on the development of the cranial growth plate is unknown. This study investigated histological alterations of the cranial growth plate induced by high methionine administration in newborn rats.

DESIGN

Twenty pregnant dams were divided into a control and an experimental group. The controls received a diet for rats and the experimental group was fed from the 18th gestational day with a special manufactured high methionine diet for rats. The high methionine diet was maintained until the end of the lactation phase (day 20). The offspring of both groups were killed at day 10 or 20 postnatally and their spheno-occipital synchondroses were collected for histological analysis.

RESULTS

The weight of the high-dose methionine treated experimental group was considerably reduced in comparison to the control group at day 10 and 20 postnatally. The cartilaginous area of the growth plate and the height of the proliferative zone were markedly reduced at postnatal day 10 in the experimental group.

CONCLUSIONS

In summary, the diet-induced hypermethioninemia in rat dams resulted in growth retardations and histomorphological changes of the spheno-occipital synchondrosis, an important craniofacial growth centre in newborns. This finding may elucidate facial dysmorphoses reported in patients suffering from hypermethioninemia.