Morphologic and molecular alteration during tibia fracture healing in rat

Area of Science:

• Orthopedics
• Regenerative Medicine
• Biomaterials Science

Background:

• Tibia fracture healing involves complex morphological, osteogenic, and metabolic changes.
• Understanding these changes is crucial for developing effective therapeutic strategies.

Purpose of the Study:

• To monitor morphological features and associated osteogenic and bone metabolic changes during tibia fracture healing in a rat model.
• To correlate these changes with inflammatory and growth factor expression.

Main Methods:

• Evaluated tibia density and trabecular thickness.
• Performed histopathology (HE staining) and quantified inflammatory factors (IL-4, IL-6, TNF-α) and metabolic biomarkers (ALP, β-CTX, P1NP) via ELISA.
• Assessed gene expression of RUNX2, TGF-β1, VEGF-α, BMP-2, BMP-4, and BMP-7 using RT-PCR.

Main Results:

• Bone density decreased until week 4, then increased. Trabeculae thickened, indicating active osteogenesis.
• Inflammation peaked at week 2 (high TNF-α, IL-6; low IL-4), resolving by week 4.
• Bone metabolism showed active osteogenesis and resorption at week 6 (high P1NP, β-CTX). Growth factor expression increased progressively.

Conclusions:

• Rat tibia fracture healing by week 6 showed increasing bone density and trabecular thickening.
• Declining inflammation and peaking bone morphogenetic proteins/growth factors confirmed active osteogenesis consistent with secondary fracture healing.