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Telocyte

Telocyte is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Telocyte rather than just read about it. In short: Telocytes are a type of interstitial (stromal) cells with very long (tens to hundreds of micrometres) and very thin prolongations (mostly below the resolving power of light microscopy) called telopodes. Rationale for the term telocyte Professor Laurențiu M.

Telocyte — main illustration
Telocyte — illustration

Key takeaways

  • Telocyte belongs to biology; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Telocyte to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Telocyte from memory before moving on to harder problems.

Reference excerpt

Telocytes are a type of interstitial (stromal) cells with very long (tens to hundreds of micrometres) and very thin prolongations (mostly below the resolving power of light microscopy) called telopodes.

Rationale for the term telocyte Professor Laurențiu M. Popescu's group from Bucharest, Romania described a new type of cell. Popescu coined the terms telocytes (TC) for these cells, and telopodes (Tp) for their extremely long but thin prolongations in order to prevent further confusion with other interstitial (stromal) cells (e.g., fibroblast (FB), fibroblast-like cells, myofibroblast, mesenchymal cells). Telopodes present an alternation of thin segments, podomeres (with caliber mostly under 200 nm, below the resolving power of light microscopy) and dilated segments, podoms, which accommodate mitochondria, (rough) endoplasmic reticulum and caveolae - the so-called "Ca2+ uptake/release units". The concept of TC was promptly adopted by other laboratories, as well.

Telocytes and/or fibroblasts? The interstitium (stroma) is in most of the cases seen as a connecting "device" for the specific structures of an organ. Usually, people perceive interstitial cells as being mainly (or even, only) fibroblasts. However, fibroblasts have the function of generating connective tissue matrix, specifically, collagen. The distinction between TC and fibroblasts is obvious since they have different ultrastructure and phenotype. Therefore, their functions should be mostly different: TC - intercellular signaling (connections), but fibroblasts - collagen synthesis. In other words, TC are "more" functionally oriented while fibroblasts are "more" structurally oriented, responsible for fibrosis. There are some clear ultrastructural features that differentiate telocytes from fibroblasts. For instance, the general aspect of TC is of a small oval (piriform/spindle/triangular/stellate)-shaped cellular body, containing a nucleus surrounded by a small amount of cytoplasm. Anyway, the shape of the cell body depends on the number of Tp. TC cellular body average dimensions are, as measured on EM images, 9.3 μm ± 3.2 μm (min. 6.3 μm; max. 16.4 μm). Fibroblast nucleus is typically euchromatic, but TC nucleus is mostly heterochromatic. Mitochondria represent only 2% of cell body volume and the Golgi complex is small in TC. Fibroblasts Golgi complex is prominent and the rough endoplasmic reticulum is very well developed (usually 5-12%) of cell volume. Since telopodes are distinctive for telocytes, here are their main features:

Number: 1–5 (frequently only 2–3 telopodes are observed on a single section, depending on site and angle of section, since their 3D convolutions prevent them to be observed at their full length in a 2D very thin section); Length: tens – up to hundreds of μm, as measured on EM images (e.g. Figs. 2-10). However, under favorable conditions in cell cultures, their entire length can be captured in several successive images (Fig. 1); Thickness: uneven caliber, mostly below 0.2 μm (below the resolving power of light microscopy), visible under electron microscopy; Moniliform aspect: podoms and podomeres; average caliber of podomeres: 0.1 μm ± 0.05 μm, min. = 0.003 μm; max. = 0.24 μm; Podoms accommodate: mitochondria, (rough) endoplasmic reticulum, caveolae, a trio called ‘Ca2+-uptake/release units’. Branching, with a dichotomous pattern; Organization in a labyrinthine system, forming a 3D network anchored by hetero- and homocellular junctions.

Summary Here is shown visual evidence (electron microscopy, electron tomography, phase contrast microscopy) for the existence of Telocytes (TC) in many organs from human and rodents. TC and Tp, and also podoms and podomeres were found in:

cavitary organs: heart (endo-, myo-, and pericardium); stomach and intestine, with mesentery; gall bladder; uterus and fallopian tube; non-cavitary organs: lungs and pleura; pancreas (exocrine gland); mammary gland; placenta; kidneys; Recent evidence shows the involvement of TC in pathology. TC are strategically located in between blood vessels (capillaries), nerve endings and the specific resident cell populations of a given organ. TC establish via Tp homo- and heterocellular junctions and release shed vesicles and exosomes.

Perspectives: regenerative medicine TC and SC (Stem Cells) make a tandem (due to specific intercellular junctions) within the so-called SC niches, at least in heart and lungs. Hence, TC could be key-players in regenerating and repair of some organs. The tandem TC-SC could be a better option for therapy rather than SC alone. Published studies suggest that cardiac TCs could be regarded as a potential cell source for therapeutic use to improve cardiac repair and function after a myocardial infarction, either alone or in tandem with SC. Recent data show that TCs are completely different from FBs, using a quantitative proteomics approach, suggesting that TCs might play specific roles in mechanical sensing and mechanochemical conversion task, tissue homoeostasis and remodelling/renewal.

Figures

See also List of human cell types derived from the germ layers Interstitial cell of Cajal, a similar, and potentially equivalent, cell

References

Illustrations

Telocyte: Figure 1. Human non-pregnant myometrium in cell culture; day 3; the first passage. Giemsa staining. One TC establishing contacts with a myocyte by a Tp of about 65 mm long. Photographic composition of 4 serial phase contrast images; original magnification 40x. In red rectangles, a higher magnification clearly shows the moniliform aspect; at least 40 specific dilations (podoms) interconnected by thin segments (podomeres) are visible in a ‘beadlike’ fashion.
Figure 1. Human non-pregnant myometrium in cell culture; day 3; the first passage. Giemsa staining. One TC establishing contacts with a myocyte by a Tp of about 65 mm long. Photographic composition of 4 serial phase contrast images; original magnification 40x. In red rectangles, a higher magnification clearly shows the moniliform aspect; at least 40 specific dilations (podoms) interconnected by thin segments (podomeres) are visible in a ‘beadlike’ fashion.
Telocyte: Figure 2. Digitally coloured TEM image shows TC (blue) in human subepicardium, bordering the peripheral cardiomyocytes (CM, highlighted in brown). The TC has three telopodes, illustrating: a) the distinctive dichotomous pattern of branching (arrows); b) Tp are very thin at the emergence of the cell body; c) alternating podoms and podomeres. Note that some portions of podomeres have the same thickness as collagen fibrills, which make them impossible to be observed under light microscopy. E - elastin Scale bar - 2 mm.
Figure 2. Digitally coloured TEM image shows TC (blue) in human subepicardium, bordering the peripheral cardiomyocytes (CM, highlighted in brown). The TC has three telopodes, illustrating: a) the distinctive dichotomous pattern of branching (arrows); b) Tp are very thin at the emergence of the cell body; c) alternating podoms and podomeres. Note that some portions of podomeres have the same thickness as collagen fibrills, which make them impossible to be observed under light microscopy. E - elastin Scale bar - 2 mm.
Telocyte: Figure 3. Human exocrine pancreas. TC (blue) form with their typical Tp a network around acini. Note the stromal synapse (red arrows) between a mast cell and the Tp of a TC. Courtesy of Dr. M.I. Nicolescu, Department of Cellular and Molecular Medicine, ‘Carol Davila’ University of Medicine and Pharmacy, Bucharest, Romania.
Figure 3. Human exocrine pancreas. TC (blue) form with their typical Tp a network around acini. Note the stromal synapse (red arrows) between a mast cell and the Tp of a TC. Courtesy of Dr. M.I. Nicolescu, Department of Cellular and Molecular Medicine, ‘Carol Davila’ University of Medicine and Pharmacy, Bucharest, Romania.
Telocyte: Figure 4. Human resting mammary gland stroma. One TC hallmark, namely Tp, appears very long and convoluted. Note homocellular junctions marked by red circles, as well as shed vesicles (blue) and an exosome (violet).
Figure 4. Human resting mammary gland stroma. One TC hallmark, namely Tp, appears very long and convoluted. Note homocellular junctions marked by red circles, as well as shed vesicles (blue) and an exosome (violet).
Telocyte: Figure 5. Human term placenta. The TC (blue) has few organelles in the perinuclear area and 3 emerging Tp (red arrows); black arrowheads mark the dichotomic branching points. Note the podoms and podomeres. Black arrow points the junction between a Tp and a smooth muscle cell (SMC, colored in brown). Reproduced with permission from [2].
Figure 5. Human term placenta. The TC (blue) has few organelles in the perinuclear area and 3 emerging Tp (red arrows); black arrowheads mark the dichotomic branching points. Note the podoms and podomeres. Black arrow points the junction between a Tp and a smooth muscle cell (SMC, colored in brown). Reproduced with permission from [2].

Worked examples

Example 1 — a first encounter with Telocyte

Start with the simplest possible case. Write down what Telocyte claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Telocyte before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Telocyte ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Telocyte

In research
Telocyte appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Telocyte in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Telocyte is common in secondary-school and first-year university syllabi. It links to neighbouring topics Human cells, so understanding it makes those chapters shorter.
In everyday life
Look for Telocyte outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Telocyte in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Telocyte means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Telocyte out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Telocyte in simple terms?

Telocytes are a type of interstitial (stromal) cells with very long (tens to hundreds of micrometres) and very thin prolongations (mostly below the resolving power of light microscopy) called telopodes. Rationale for the term telocyte Professor Laurențiu M.

Why does Telocyte matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Telocyte?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Telocyte.

Tags

  • Human cells

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