Long regarded as mere powerhouses, mitochondria are also turning out to be signalling organelles. One of the most intriguing discoveries of the past decade is that of peptides encoded by the mitochondrial genome, of which Mitochondrial Open (TS-c) is the best-studied member. This article is a documentary overview of what is known about this class of compounds, strictly for laboratory research use only.
What is Mitochondrial Open (TS-c)?
Its name describes its origin. It is a short peptide of 16 amino acids whose distinctive feature is being encoded not by the nucleus, but by an open reading frame located within the 12S ribosomal RNA gene region of the mitochondrial genome — hence "12S" and "type-c".
Its molecular weight is about 2,174 g/mol. Together with the 16-amino-acid length, that is the marker allowing it to be identified on a certificate of analysis and distinguished from other members of the same class, which circulate under similar names and are regularly confused with one another.
Why this class of peptides interests researchers
The remarkable point is not a pharmacological property; it is a question of which way information travels inside the cell.
The classical model describes a nucleus that commands and mitochondria that execute: nuclear DNA encodes nearly all mitochondrial proteins, which are then imported into the organelle. The discovery of peptides encoded by the mitochondrial genome itself reverses part of that picture: the mitochondrion appears able to send its own peptide signals to the rest of the cell.
That reversal is what made this family a subject of basic research, and TS-c is its best-documented member.
What the literature shows, and what it does not
The nature of the available evidence must be stated plainly. Most data come from preclinical studies: in vitro cell cultures and in vivo animal models. The available human data are observational — measurements of circulating levels and correlations — which demonstrates neither causality nor any effect of exogenous administration.
No randomised human clinical trial has been published on this peptide. No therapeutic conclusion can therefore be drawn.
The literature also identifies clear translational obstacles: low bioavailability, limited stability in solution, short half-life, and immunogenicity questions raised but not settled. Added to this are heterogeneous preclinical protocols and a lack of standardisation between teams.
These points underline that TS-c remains an object of scientific study, not a product validated for human use.
Reconstitution & storage
In a research context, TS-c is generally supplied as a lyophilized powder. Good laboratory handling practice calls for storing the lyophilisate cold (typically at -20 °C), protected from light and moisture, to preserve the integrity of the peptide sequence.
Reconstitution is usually carried out with bacteriostatic water, added slowly down the vial wall, without vigorous shaking or vortexing, as shear degrades peptides. Once reconstituted, the peptide in solution is described as poorly stable: aliquoting right after reconstitution is particularly advisable, and repeated freeze-thaw cycles should be avoided.
These steps relate exclusively to the handling of laboratory samples.
Disclaimer: this information is provided for research and scientific documentation purposes only ("research use only"). It does not constitute a protocol, medical advice, or any recommendation for human use.
In summary
TS-c illustrates a frontier of cell biology: mitochondria able to send peptide signals to the rest of the cell. It is on that basis, and because it is the best-characterised member of its class, that it interests basic research. The pharmacological limits and the absence of clinical data, by contrast, call for the greatest caution: it remains, to date, an investigative scientific tool reserved for laboratory use.