Intracellular lipids in rabbit ear cartilage during tissue regeneration

Circular holes 10 mm in diameter were punched in the proximal region of rabbit ears, and the intracellular lipid content of the regenerated cartilage and the neighbouring old cartilage was studied histochemically up to the 32nd week after wounding. Chondroblasts appeared in the peripheral zone of the regenerated tissue towards the end of the 3rd week, but no intracellular lipids were observed until the 8th week. In the following weeks chondrocytes and intracellular lipids appeared in the intermediate and central zones of the regenerated tissue, the production of cartilage and intracellular lipid being particularly vigorous in the central zone during the last weeks of the study. In the old cartilage adjoining the wound, intracellular lipid levels declined considerably except in new cells produced by proliferation of the perichondrium after wounding. Phospholipids were only observed in the youngest cartilage cells and disappeared when deposits of neutral lipids began to be formed. The interpretation of these observations and the function of intracellular lipids in cartilage are discussed.