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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?

Franck Dernoncourt
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user952
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  • "This post is regarding a follow up on my initial post on "Properties and life cycle of chondrocytes and tenocytes". -> could you please add a link to this post? I couldn't find it. Thanks! – Franck Dernoncourt Jun 15 '19 at 20:34

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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).

jonsca
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MCM
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  • 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 09 '12 at 06:56
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    Also, adding some references will improve the quality of the answer. – nico Aug 09 '12 at 06:57
  • @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 05:02
  • 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 02:13
  • Just to clarify, what I disagree on is the term **normal**. For neurons you may want to have a look at the [rostral migratory stream](http://en.wikipedia.org/wiki/Rostral_migratory_stream) – nico Aug 17 '12 at 08:08
  • Then define the most common route of cellular migration in the human body as you see it. I'm not saying you're wrong, but just *repeating* "Neurons do it differently" isn't the same as proving I'm wrong. – MCM Aug 17 '12 at 15:22
  • I just think there are different routes, I do not like the use of the term normal because it implies the others are "anormal". Semantics, probably. Anyway, I would say that, for instance, during development many cells do not migrate through bloodstream, but rather in the extracellular matrix of the tissue. – nico Aug 17 '12 at 17:54
  • Anyway, my point is: you cannot say that tenocytes cannot migrate in the tendons BECAUSE there is no blood vessels. This is obviously false, as there are counterexamples of cells that migrate without needing blood vessels. New cells may as well be born from locally present stem cells, as it is the case in other tissues. – nico Aug 17 '12 at 18:02
  • Allow me a moment to be just as pedantic as you. If you're talking specifically about tenocytes, and you are right above, then the vascular system is the ONLY common path for migration out of the bone marrow from their mesenchymal stem cell progenitors. There aren't any stem cells in the somatic muscle tissue. They just don't exist, otherwise tendons might heal much, much faster. For the rest of your tangent about cellular migratory paths, I don't see how they relate to the original question - much less how they're anything other than your opinion when you can't back up your answers. – MCM Aug 18 '12 at 04:16
  • Come on, do not take it personally. What you are saying is exactly why I am asking for references. Your answer just says: "there is no blood stream hence cell cannot migrate". Sorry, but I consider that a bad explanation. Progenitors could get near the tendon via bloodstream and then migrate through the collagen fiber. Immune cells do that, for instance during tendinitis. I am not being pedantic, but -because I am far from being an expert in tendons- I do need references to decide how to vote on your answer. If you are willing to answer the question the burden of proof is on you, not on me. – nico Aug 18 '12 at 07:39
  • **You** have the burden of proof. You do not contest my initial assessment of whether or not tendons/cartilage are capable of repair, but my use of the word 'normal'. That's a **separate** debate which *you* started. You continued by naming a *single* cell type (Neurons) which use an alternate method, and failed to provide **any** other examples while it's common knowledge that the vascular system ferries Erythrocytes, Leukocytes, and Platelets all the time. Then your example of progenitor migration (which doesn't happen anyways) **still uses the vascular system to migrate to the tendon.** – MCM Aug 18 '12 at 14:54
  • If that's not the definition of pedantic, I don't know what is, and I'm not debating the topic with someone I don't believe has a firm grasp on basic human anatomy and physiology. – MCM Aug 18 '12 at 14:57
  • wow, we are down to personal offense now. How poor. By the way, I have a PhD in physiology so, yes, I have a basic grasp on it. Anyway, I will be happy to remove my downvote when you will add some proper references. Have a good day. – nico Aug 18 '12 at 15:58
  • let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/4556/discussion-between-nico-and-mcm) – nico Aug 18 '12 at 16:00