Catch connective tissue

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Catch connective tissue [1] [2] [3] (also called mutable collagenous tissue) is a kind of connective tissue found in echinoderms (such as starfish and sea cucumbers) which can change its mechanical properties in a few seconds or minutes through nervous control rather than by muscular means.

Contents

Connective tissue, including dermis, tendons and ligaments, is one of four main animal tissues. Usual connective tissue does not change its stiffness except in the slow process of aging. Catch connective tissue, however, shows rapid, large and reversible stiffness changes in response to stimulation under nervous control. This connective tissue is specific to echinoderms in which it works in posture maintenance and mechanical defense with low energy expenditure, and in body fission and autotomy. The stiffness changes of this tissue are due to the changes in the stiffness of extracellular materials. The small amount of muscle cells that are sometimes found scattered in this tissue has little influence on the stiffness-change mechanisms.

Tissue distribution

Catch connective tissue is found in all the extant classes of echinoderms.

Early echinoderms were sessile organisms that fed on suspended particles carried by water currents. Their body was covered with imbricate small skeletal plates. The arrangement of plates suggests that plates worked as sliding joints so as animals to be able to change their body shape: they could possibly take an extended feeding posture and a flat "hiding" posture. The body plates might be connected with catch connective tissue that allowed early echinoderms such postural changes. [4]

Mechanism of stiffness changes

Detailed mechanical properties and their changes have been studied only in sea-cucumber dermis. Its mechanical properties are determined by the extracellular materials that are made of collagen fibrils embedded in a hydrogel of proteoglycans. The dermis takes three mechanical states: soft (S1), standard (S2) and stiff (S3). [5] Animals without stimulation takes the standard state S2. Different molecular mechanisms of stiffening have been found in the transition S1→S2 and in the transition S2→S3. Three proteins that cause stiffness changes have been isolated from sea cucumbers. Tensilin causes the change S1→S2 increasing cohesive forces between collagens, whereas softening causes the change in the reverse direction; NSF induces S2→S3. [6] [7] [8] There are cross bridges between collagen fibrils. The number of bridges increases in the order S1<S2<S3. [9]

Nervous control

The mechanical states of catch connective tissue are under nervous control and thus we can regard this tissue as one of neurally controlled mechano-effectors such as muscles. It is found in the sea-urchin spine joints that the stiffness of catch connective tissue changes in the coordinated manner with the muscle contractions. [10] One of the characteristic cells found in catch connective tissue is juxtaligamental cells containing secretory granules. [11] These cells are supposed to contain proteins controlling stiffness of extracellular materials. When stained with the antibody specific to echinoderm nerves sea-cucumber body wall is supplied with immunoreactive fine fibers running among the collagen fibrils. Pharmacological experiments suggested the presence of two types of cholinergic systems, one is the nicotinic one involved in the dermal stiffening and the other is the muscarinic one involved in softening. Cholinergic nerves seem to control the secretory activities of juxtaligamental cells. The presence of the cholinergic system was supported by the neuropeptide stichopin that inhibits the action of stiffening cholinergic systems. Stichopin is one of four new peptides in the dermis of sea cucumbers. [12] Other ones are the neuropeptide NGIWYamide that stiffens the dermis and two holokinins that soften the dermis. The nerves containing these neuropeptides possibly control the secretory activities of juxtaligamental cells.

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References

  1. ↑ Motokawa, T (2019). "Skin of sea cucumbers: the smart connective tissue that alters mechanical properties in response to external stimuli". Journal of Aero Aqua Bio-Mechanisms. 8: 2. doi: 10.5226/jabmech.8.2 . S2CID   104468881.
  2. ↑ Wilkie, I.C. (2005). "Mutable collagenous tissue: overview and biotechnological perspective". Prog. Mol. Subcell. Biol. Progress in Molecular and Subcellular Biology. 21: 221–250. doi:10.1007/3-540-27683-1_10. ISBN   3-540-24402-6. PMID   17152700.
  3. ↑ Motokawa, T (1984). "Connective tissue catch in echinoderms". Biol. Rev. 59 (2): 255. doi:10.1111/j.1469-185X.1984.tb00409.x. S2CID   86391676.
  4. ↑ Motokawa, T (1988). "Catch connective tissue: a key character for echinoderms' success". In Burke, R.D.; Mladenov, P.V.; Lambert, P.; Parsley, R.D. (eds.). Echinoderm Biology. Rotterdam: Balkema. p. 1988.
  5. ↑ Motokawa, T.; Tsuchi, A. (2003). "Dynamic mechanical properties of body-wall dermis in various mechanical states and their implications on behavior of sea cucumbers". Biol. Bull. 205 (3): 261–275. doi:10.2307/1543290. JSTOR   1543290. PMID   14672981. S2CID   21759312.
  6. ↑ Yamada, A.; Tamori, M.; Iketani, T.; Oiwa, K.; Motokawa, T. (2010). "A novel stiffening factor inducing the stiffest state of holothurian catch connective tissue". J. Exp. Biol. 213 (Pt 20): 3416–3422. doi:10.1242/jeb.044149. PMID   20889821. S2CID   10401406.
  7. ↑ Takehana, Y.; Yamada, A.; Tamori, M.; Motokawa, T. (2014). "Softenin, a novel protein that softens the connective tissue of sea cucumbers through inhibiting interaction between collagen fibrils". PLOS ONE. 9 (4): e0195836. doi: 10.1371/journal.pone.0195836 . PMC   5897022 . PMID   29649336.
  8. ↑ Tipper, P.; Lyons-Levi, G.; Atkinson, M.A.I.; Trotter, J.A. (2003). "Purification, characterization and cloning of tensilin, the collagen-fibril binding and tissue stiffening factor from Cucumaria frondosa dermis". Matrix Biol. 21 (8): 625–635. doi:10.1016/S0945-053X(02)00090-2. PMID   12524049.
  9. ↑ Tamori, M.; Ishida, K.; Matsuura, E.; Ogasawara, K.; Hanasaka, T.; Takehana, Y.; Motokawa, T.; Osawa, T. (2016). "Ultrastructural changes associated with reversible stiffening in catch connective tissue of sea cucumbers". PLOS ONE. 11 (5): e0155673. Bibcode:2016PLoSO..1155673T. doi: 10.1371/journal.pone.0155673 . PMC   4871580 . PMID   27192546.
  10. ↑ Motokawa, T.; Fuchigami, Y. (2015). "Coordination between catch connective tissue and muscles through nerves in the spine joint of the sea urchin Diadema setosum". J. Exp. Biol. 218 (Pt 5): 703–710. doi: 10.1242/jeb.115972 . PMID   25740901. S2CID   1320567.
  11. ↑ Wilkie, I.C. "The juxtaligamental cells of Ophiocomina nigra (Abildgaard) (Echinodermata: Ophiuroidea) and their possible role in mechano- effector function of collagenous tissue". Cell Tissue Res. 197 (1979): 515.
  12. ↑ Birenheide, R.; Tamori, M.; Motokawa, T.; Ohtani, M.; Iwakoshi, E.; Muneoka, Y.; Fujita, T.; Minakata, H.; Nomoto, K. (1998). "Peptides controlling stiffness of connective tissue in sea cucumbers". Biol. Bull. 194 (3): 253–259. doi:10.2307/1543095. JSTOR   1543095. PMID   9664654.
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