SS-31 10mg Cellular senescence

Cardiolipin is a phospholipid quasi-exclusively localized in the inner mitochondrial membrane, where it occupies approximately 20% of membrane lipids. It plays a critical structural role in the assembly of respiratory chain complexes (I, III, IV, V) and in the stabilization of cytochrome c oxidase. The accumulation of SS-31 in this membrane via cardiolipin binding allows a local concentration 1000 to 5000 times superior to plasma concentrations, conferring to the molecule an unprecedented tissue pharmacokinetic profile among peptides.

Atlas Lab formulates SS-31 10mg as high-purity lyophilizate (≥98% HPLC) for research applications exclusively. Strict RUO — not intended for human, veterinary, diagnostic or therapeutic use. SS-31 has been the subject of more than 300 publications and several phase 2 and 3 clinical trials piloted by Stealth BioTherapeutics, without initial FDA approval for the main indications tested (heart failure, MELAS, Barth syndrome), but the accumulated scientific corpus makes it a reference experimental tool for mitochondrial studies.

Chronic schemes reported in the literature vary according to experimental model: continuous daily administration for aging and mitochondriopathy studies (24-48 weeks), short peri-procedural administration for ischemia-reperfusion models (few hours to few days around the ischemic stimulus), monthly pulse administration for certain maintenance studies. The flexibility of the tissue pharmacokinetic profile allows adapting the scheme to the experimental model.

Before reconstitution, the lyophilized vial of SS-31 10mg must be stored between 2 and 8 degrees Celsius, in its original packaging, away from direct light and any heat source. Under these conditions, the lyophilizate stability is ensured for 24 to 36 months from the manufacturing date. The stability of lyophilized SS-31 is comparable to that of short linear peptides, the tetrapeptide sequence with D-Arg and 2',6'-diMethylTyr modifications being naturally resistant to degradation in the solid state.

Prolonged storage at ambient temperature (>25 degrees Celsius) must remain exceptional and not exceed 72 hours; beyond that, a risk of degradation and potency loss exists, particularly for the modified dimethyl-tyrosine group which presents a thermal sensitivity slightly superior to native residues.

After reconstitution with sterile bacteriostatic water, the aqueous SS-31 solution remains stable for approximately 30-45 days at 2-8 degrees Celsius. This duration is in the upper range of research peptides, due to the short length of the sequence and the structural protection conferred by non-native residues (D-Arg and 2',6'-diMethylTyr) which resist residual contaminating peptidases better. Freezing at -20 degrees Celsius or less extends stability up to 6 months under optimal conditions.

Light protection is recommended due to the presence of the dimethyl-tyrosine group which can undergo photo-oxidation under intense UV radiation. The original opaque packaging or storage in a closed refrigerator drawer suffices in most configurations. Protection against intense mechanical agitation is less critical than for large peptides (such as PEG-MGF), the compact tetrapeptide structure being less subject to denaturation by turbulence. Gentle rotation between palms for 2-3 minutes is sufficient for complete dissolution.

Any solution presenting a color change (normally colorless and clear), a precipitate, or particles in suspension must be immediately discarded. Visual inspection before each sampling is a mandatory practice in research context. Atlas Lab provides detailed recommendations for rigorous experimental traceability. Traceability is particularly important for SS-31 due to the required purity (≥98% HPLC) to avoid any contamination by isomers or degradation products that could affect specific mitochondrial activity.

The mechanism of action of SS-31 rests on three distinct structural properties that confer to it a unique mitochondrial pharmacodynamic. The net positive charge at physiological pH (D-Arg and Lys residues), combined with membrane permeability conferred by alternation of charged and aromatic residues, allows passive crossing of lipid membranes without requiring an active transporter. This characteristic distinguishes SS-31 from classic CPP (Cell Penetrating Peptide) core peptides by making it specifically tropic for the inner mitochondrial membrane.

Affinity for cardiolipin was demonstrated by Zhao and collaborators in 2004 in the Journal of Biological Chemistry via fluorescence spectroscopy and FRET, establishing a submicromolar dissociation constant. This selective binding concentrates SS-31 in the mitochondrial matrix space according to an electrochemical gradient maintained by the mitochondrial membrane potential (delta Psi m, typically -180 mV). Healthy mitochondria with normal potential accumulate more SS-31, creating a form of self-regulation: depolarized (dysfunctional) organelles capture less molecule.

Stabilization of cardiolipin and associated complexes constitutes the main documented biological effect. Birk 2013 studies (Journal of the American Society of Nephrology) showed that SS-31 preserved cytochrome c oxidase activity (complex IV) in renal ischemia-reperfusion models. Szeto 2014 (British Journal of Pharmacology) synthesized observations on reduction of mitochondrial ROS production (reactive oxygen species) without however acting as a classical antioxidant: SS-31 does not neutralize free radicals directly but prevents their excessive generation by electron transport optimization.

Anti-lipid peroxidation action was specifically characterized by Birk 2014 (Kidney International), with reduction of 4-hydroxynonenal and malondialdehyde formation in mitochondria exposed to oxidative stress. Preservation of mitochondrial cristae crystal structure, essential for electron transport efficiency, was visualized by electron microscopy in several preclinical models (cardiac ischemia, neurodegeneration, nephropathy).

A secondary mechanism would involve modulation of the opening of the mitochondrial permeability transition pore (mPTP), structure involved in cell death by necrosis/apoptosis under severe stress conditions. Prevention of mPTP opening by SS-31 was documented in cardiac ischemia-reperfusion models by Kloner 2012 (JACC). This mechanism could explain cardioprotective effects observed in certain clinical studies, even though results of phase 3 EMBRACE-STEMI (post-infarction) trials did not reach primary endpoints.

Unlike GH secretagogues or growth peptides (BPC-157, PEG-MGF), SS-31 does not act via a cell surface receptor. Its purely intramitochondrial action thus distinguishes itself fundamentally from other research peptides, which influences experimental usage models (metabolic studies, mitochondriopathies, oxidative stress, cellular aging).

The scientific corpus of SS-31 covers twenty-five years of publications since the first works of Szeto and Schiller at Cornell. The founding studies of Zhao 2004 (Journal of Biological Chemistry) established cardiolipin binding and preferential mitochondrial localization, opening the way to an entirely new class of therapeutics targeting intracellular organelles via amphiphilic peptides.

Szeto 2008 (Antioxidants & Redox Signaling) published the first complete synthesis of the pharmacological profile including plasma half-life (approximately 4-6 hours in humans), tissue biodistribution (preferential accumulation heart, kidney, brain, skeletal muscle), and the first animal cardiac ischemia-reperfusion model results documenting infarct size reduction of 40-60% in rat and pig.

Birk 2013 (Journal of the American Society of Nephrology) and Birk 2014 (Kidney International) characterized protective effects in renal ischemia-reperfusion with preservation of tubular function and reduction of necrosis. Szeto 2011 (American Journal of Physiology) studied renal aging in aged rats, documenting improvement of glomerular filtration and reduction of oxidative stress markers after chronic treatment by SS-31.