Take the 2-minute tour ×
Biology Stack Exchange is a question and answer site for biology researchers, academics, and students. It's 100% free, no registration required.

This post is regarding a follow up on my initial post on "Properties and life cycle of chondrocytes and tenocytes".

I am elaborating on my question on the lifespan of tenocytes and chondrocytes.

From what I have read, tenocytes and chondrocytes form from mature stem cells, more specifically Mesenchymal stem cells. These cells can replicate through mitosis, and are present in the body in different tissues like bone marrow. These cells are the key in the regeneration of diverse tissues.

When the cells that inhabit tendons or cartilage die, do new MS cells travel to the tendon or cartilage area and diffentiate into a new tenocyte or chondrocyte? Are tenocytes and chondrocytes continuously replaced?

share|improve this question
add comment

1 Answer 1

Not that I'm aware of. There isn't any blood flow to either tendons or cartilage as an adult, so the pathway for migration doesn't exist.

Tendons and cartilage are tissues composed of dead cells after their formation (the cartilage growth plates cease to exist in your teen and completely ossify, tendons I'm not sure on). Damage to tendons and cartilage is permanent, and can cause arthritis (when the cartilage is completely worn away and bone-on-bone contact occurs at joints).

Unlike living tissue, because tendon cells are dead, they are much, much easier to transplant - they do not produce any signaling molecules or have any surface proteins which would trigger an immune reaction for the vast majority of people. Shoulder surgeries often utilize this to the benefit of the patient, especially acromio-clavicular injuries.

If living cells are brought to the dead tissue, some repair is initiated, as I do recall a technique where surgeons tapped into the marrow of a patient's femur to stimulate cartilage reconstruction, but I also remember reading that the new cartilage formed wasn't the same hyaline cartilage produced by chondrocytes of the growth plate, so the repairs were temporary.

Artificially produced tendons do exist, and many are braided in order to foster interaction with host tissues (when you suffer from tendonitis, the tendon itself isn't repaired - the tissue around the tendon is repaired and strengthened). I'm not aware of any successful attempts to regrow tendons.

Attempts to grow cartilage in vitro have been successful, but re-introducing it into the body to produce a surface to articulate against has presented significant difficulties. Because we cannot (currently) reproduce biological articular surfaces, joint replacement often uses composites or surgical grade metals (both of which present problems of their own, but arthritis is not one as there's no living tissue to feel pain).

share|improve this answer
    
I am a bit puzzled by two of your statements, could you comment on them? 1) "There isn't any blood flow to either tendons or cartilage as an adult, so the pathway for migration doesn't exist.". Since when migration needs blood flow? Plenty of cells (neurons, for instance) migrate using the extracellular matrix as a guide. 2) "Unlike living tissue, because tendon cells are dead [...] they do not produce any signaling molecules or have any surface proteins which would trigger an immune reaction": so... you mean collagen and proteoglycanes are not allergenic? –  nico Aug 9 '12 at 6:56
1  
Also, adding some references will improve the quality of the answer. –  nico Aug 9 '12 at 6:57
    
@nico The normal route for cellular migration is the circulatory system. Collagen almost never produces an allergic reaction. Proteoglycans vary. As an update: I was apparently out of date with tendons. Tenocytes do perform repairs, but it might take a while (as-in, measured over months or years for significant damage). -Riley, G. (2004). "The pathogenesis of tendinopathy. A molecular perspective" Cartilage would be repaired by chondrocytes, which inhabit the lacunae of bones. Cartilage lacks lacunae. Chondrocytes, literally, cannot reach damaged cartilage unless the damage reaches bone. –  MCM Aug 16 '12 at 5:02
    
I beg to differ on the circulatory system being the normal route for cellular migration. It is one of the routes for migration, surely, if you think of the immune system but, again, there are counterexamples, neuronal migration being probably the most obvious. –  nico Aug 16 '12 at 14:52
    
Then you're free to differ. To the limit of my knowledge the normal route for cell migration throughout the body is either the circulatory or lympathic systems, as those systems span the entire body. If the majority of cells use a separate route, then I am not aware of it. Neurons - as much "migration" as occurs with them after adulthood - are special cells to begin with. I'm not saying you're wrong, but I'm unaware of other major routes. –  MCM Aug 17 '12 at 2:13
show 10 more comments

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.