Growth Plate Micro-Climate

Much of human height is determined by the micro-climate in the Epiphyseal plates of the long bones in our legs. They are size-relational wonderlands and the specific climatological conditions within these wonderlands decide if, when, and where, growth happens.

The growth plate consist of translucent layers of cartilage. There are several distinct zones in the growth plates, each with ultra-local physical properties and chemicals influencing growth. These properties include mechanical forces, temperature and its own specific composition of the ECM, the extracellular matrix. The ECM is a network, consisting of macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite, that provides structural and biochemical support to surrounding collagen cells and provides a scaffold for the chondrocytes. These chondrocytes will either stay in their current state and become articular cartilage or they ossify and become bone tissue. Linear growth is determined primarily by the formation of cartillage and its polarized mineralization. Various molecular signaling pathways, such as the Hedgehog pathway (e.g., Ihh) and Wnt/β-catenin signaling, play important roles in controlling chondrocyte proliferation, differentiation, and hypertrophy. Ambient and local temperatures can directly influence the growth rate of cartilage by affecting cell proliferation, metabolism, and matrix production. The amount of growth depends a lot on the environmental factors surrounding it. In growth plate cells the plasticity of the microclimate’s response to such external factors allows for adaptive changes in bone growth. As climate becomes more extreme, our extremities become shorter. But we should not confuse our negative association with extreme environmental conditions with the micro-climatical response in our epiphyseal plates. The small body is a beautiful answer and a manifestation of the incredible resilience and intelligence of life.