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Expression of growth factors in chicken growth plate with special reference to tibial dyschondroplasia
1Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens 30602-7388, USA.
Insights
Growth factors like TGF-β, IGF-I, and EGF show distinct expression patterns in chick embryonic bone development and tibial dyschondroplasia (TD). Their localization changes with development, offering insights into bone growth and TD pathology.
Area of Science:
- Developmental Biology
- Cell Biology
- Orthopedics
Background:
- Growth factors are crucial for skeletal development.
- Tibial dyschondroplasia (TD) is a developmental bone disorder with unclear etiology.
- Understanding growth factor expression in normal and TD growth plates is essential.
Purpose of the Study:
- To identify and characterize the expression patterns of immunoreactive growth factors in chick embryonic cartilage and bone.
- To compare growth factor expression in normal and TD-affected growth plates.
- To elucidate the role of specific growth factors in skeletal development and TD.
Main Methods:
- Immunohistochemistry was used to detect growth factors in chick embryonic tibiotarsi.
- Analysis focused on normal and TD-affected growth plates at various embryonic and post-hatch stages.
- Specific growth factors investigated include TGF-β, TGF-α, EGF, and IGF-I.
Main Results:
- Transforming growth factor beta (TGF-β) showed consistent distribution in normal and TD growth plates.
- Insulin-like growth factor I (IGF-I) expression varied, appearing in early embryos, disappearing, and reappearing before hatching, with altered localization in TD.
- Epidermal growth factor (EGF) and transforming growth factor alpha (TGF-α) exhibited dynamic expression patterns, with restricted presence in TD growth plates.
Conclusions:
- Growth factors exhibit specific temporal and spatial expression during chick skeletal development.
- Altered expression patterns of IGF-I, EGF, and TGF-α in TD suggest their involvement in the pathogenesis of the condition.
- These findings contribute to understanding the molecular mechanisms underlying bone development and TD.
Abstract:
Immunoreactive growth factors were identified in chick embryonic cartilage and bone, and in the growth plate of normal tibiotarsi and tibiotarsi affected with tibial dyschondroplasia (TD). A specific pattern of temporal and spatial expression was observed for each growth factor. Transforming growth factor beta and alpha (TGF beta and TGF alpha) and epidermal growth factor (EGF) were briefly expressed in chondrocytes of early chick embryos. Immunolabelling for TGF beta then gradually shifted into cartilaginous matrix and was not observed in cytoplasm of hypertrophic chondrocytes until the late embryonic and post-hatch stages. The distribution and intensity of TGF beta labelling was the same in chondrocytes of the TD and normal growth plate. Insulin-like growth factor I (IGF-I) labelling persisted from the early embryonic stage to the end of the mid-stage and then disappeared from chondrocytes. IGF-I appeared again in chondrocytes 1-2 days before hatching. After hatching, the labelling intensified in prehypertrophic and hypertrophic chondrocytes. TD lesions displayed IGF-I in the distal region, mainly in chondrocytes around small blood vessels. EGF reappeared in proliferative and hypertrophic chondrocytes of the mid-embryonic stage. By day 18 after hatching, EGF was present mainly in prehypertrophic and hypertrophic chondrocytes. EGF was demonstrated only in distal proliferative and early prehypertrophic chondrocytes of the dyschondroplastic growth plate. TGF alpha was identified in hypertrophic chondrocytes adjacent to the periosteum and in the distal tip of the mid-embryonic growth plate. With progressing ossification, TGF alpha labeling intensified in the embryonic hypertrophic chondrocytes. In the TD growth plate at day 18 after hatching, TGF alpha expression was limited to 1-3 concentric layers of chondrocytes surrounding blood vessels.