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Extracellular Matrix Proteins and the Aging Process

aNewDomain — Virtually a century ago, in 1922, Ukrainian pathophysiologist Alexander Bogomolets proposed that the deterioration of the connective tissues trigger getting older.

In his later work [1], he said that “A person has the age of his/her connective tissue.”

Connective tissue consists of fibrous tissues, fat, cartilage, bone, bone marrow, blood, and embedded in a big amount of extracellular supplies.

Assorted varieties of collagens constitute the principal element of the connective tissue of vertebrates and make up about one-third of the body’s protein content.

The impression of extracellular matrix proteins cross-linking on the growing older course of and aging-related illnesses was studied in the early works of Johan Björksten, which date again to 1942. The writer proposed that the formation of intra- and intermolecular covalent cross-links modifications the construction of the macromolecules and results in their dysfunction [2]:

“The aging of living organisms I believe is due to the occasional formation, by tanning, of bridges between protein molecules, which cannot be broken by the cell enzymes. Such irreparable tanning may be caused by tanning agents foreign to the organism, or formed by unusual biological side reactions, or it may be due to the formation of a tanning bridge in some particular position in the protein molecules. In either event, the result is that cumulative tanning of body proteins, which we know as old age.”

Fritz Verzár demonstrated in the 1950s for the first time that the age-dependent modifications of the extracellular matrix exponentially improve the cross-linking of collagen fibers [3].

These modified proteins remain unrepaired, accumulate throughout a person’s lifetime, and cause modifications in mechanical properties of a distinct segment microenvironment, tissues, and organs, which results in a vicious cycle of progressively growing injury, and limits the software of senolytics, the stem cells, and different “anti-aging” therapies.

Want for Analysis

So far, there’s not one trendy technique which discusses the connection between life expectancy and elements corresponding to exosomes of stem cells, donor mitochondria, senolytics, epigenetic rollback (the listing could be continued), is ready to restore the construction of the extracellular matrix, the mechanical properties of which are not any less of an essential function than the chemical signaling elements (by means of ions and molecules) in determining the fate of a cell, tissue, organ and organism as an entire.

Furthermore, molecules of collagen include a considerable amount of proline, an amino acid which may conduct weak electromagnetic waves generated by both the cells and tissues. Subsequently, one can’t exclude the risk that connective tissue, in addition to different mechanic and electric alerts, type an integrated bioelectric signaling system in the physique.

It’s fascinating to notice a number of works during which researchers, by altering the surroundings topography [4, 5] and electromagnetic radiation [6, 7], have been capable of not only control the cell fate but in addition change grownup somatic cells into stem cells without the help of viruses with Yamanaka factor vectors.

Even minor structural modifications in the extracellular medium affect gene expression and cell perform. Each, mechanical alerts transmitted via the cytoskeleton of the cell and the rigidity of the nuclear lamina jointly regulate the dynamics of the nucleus and chromatin [8, 9].

So, “young” fibroblasts age in the previous matrix and vice versa — “old” cells lose the indicators of the secretory phenotype related to growing older in the “young” matrix [10–12].

Additionally, it’s doubtless that the mechanical properties of the extracellular matrix have an effect on the morphology of mitochondria and the synthesis of ATP [13–14].

While some might speculate that if the previous matrix is destroyed, the physique updates the collagen and creates a brand new and more improved version of the earlier matrix. Nevertheless, they might be ignoring the proven fact that based on a number of research, pores and skin collagen molecules have a half-life of 15 years, while cartilage has a half-life of over 100 years [15–17] as well as the restrictions of the process — there are presently no selective enzymes, so all the proteins should be destroyed. Furthermore, upon growing the number of cross-links, collagen fibers develop into denser making the matrix less accessible for the enzymes which take part in the natural circulation of collagen. Consequently, the velocity of protein turnover in the matrix slows down with time resulting in further cross-links.

The process of glycation (the explanation for cross-links) is virtually unregulated. There’s the risk of containing glycation via transglycation [18], throughout which glutathione, polyamines, thiols, free amino acids (e.g., taurine and lysine) are consumed, stopping the formation of latest crosslinks. Additionally, there’s the risk of limiting the injury of the physique’s response to a rise in the rigidity of the matrix — secretion of remodeling progress factor-beta (TGF-beta), Cysteine-rich angiogenic inducer 61 (Cyr61/CCN1) and other signaling molecules. For example, tissue fibrosis may be slowed down by inhibiting matrix metalloproteinases, one in every of which is doxycycline.

Unfortunately, even with the emergence of David Spiegel’s promised answer [19], whose group is working on creating enzymes towards glucosepane (one in every of the most ample crosslinking products in the human body), the drawback continues to be not solved — destruction of one in every of about 20 kinds of recognized crosslinks will most certainly be momentary so won’t significantly change the mechanical properties of the extracellular matrix.

In addition to covalent crosslinking, the long-living proteins are additionally getting older due to spontaneous racemization of aspartic acid residues [20–22].

Upon growing the number of cross-links, collagen fibers turn into denser, making the extracellular matrix much less accessible to enzymes (comparable to L-isoaspartyl methyltransferase [23]) that restore these structurally altered by the racemization of amino acid proteins underneath normal circumstances [24]. This contributes to the accumulation of damaged proteins in collagen, which adversely affects the mechanical power of tissues during ageing [25].

Subsequently, apart from the destruction of extracellular matrix crosslinks, it’s essential to discover a answer to accelerate the restoration of proteins, which are altered by the racemization of amino acids.

Understanding the consequences of the formation of protein crosslinks requires extra attention both from the scientific group and unbiased researchers who’re passionate on the subject of the extension of the human lifespan.

By doing so, it allows us to degree up the enjoying subject where we will create and work on extra critical and impactful options.

Cowl picture rendition of extracellular matrix proteins:  by way of News.Medical.Internet, Vshivkova/


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