Senolytics inhibiting the accumulation of senescent cells in the tissues of the elderly, certainly help to counteract the development of age-related pathology.
In theory, by ridding the body of the aged cells, the senolytic, should induce start of the regeneration process “on demand”, the goal of which is to fill in the formed “cleared” space with new cells. However, in practice, especially in the case of the tissues of the old organism, such replenishment usually does not occur.
Thus, for example, it was found that Pax7-expressing satellite cells, which are formed at the embryo stage, are indispensable for the regeneration of skeletal muscles in adults and exhaustion of their pool leads to myopathy [PMID:21828093, PMC4731230]. In the same way, the loss of skin fibroblasts [PMID: 30415836] does not usually accompanied by replenishment with new cells. Moreover, senolytics in some cases can reduce the functionality of tissues. In particular, the use of one of the senolytics, dasatinib caused endothelial dysfunction and pulmonary hypertension [PMC5962749], which was corrected with the help of ROCK inhibitors.
Obviously senolytics should not be used as monotherapy, but in combination with loss replacement methods. One way to compensate such losses may be by cloning basic progenitor cells [PMC5023026, PMC3065488] using a method of “Conditionally reprogrammed (conditionally immortalized) cells (CRC)” [PMC2862604, PMC3523865, PMC5745544, PMC6032561]. This, conditional reprogramming of epithelial cells is mediated by a combination of ROCK inhibitor and a soluble factor(s) released by apoptotic feeder cells [PMC5745544]. And what is important - this induction of CRCs is reversible and removal of ROCK inhibitor and feeders allows the cells to differentiate normally - CRCs retain a normal karyotype and remain nontumorigenic.
So far, this technology has been successfully tested only for in vitro experiments. However, there are prerequisites to use this technology in vivo. For example, Koda et al., have developed Poly Lactic/Glycolic Acid (PLGA) microspheres for controlled prolonged release of ROCK inhibitor [PMC5551544]. Effect of induced cellular proliferation, concomitant with the amelioration of senescent phenotype by ROCK inhibition was observed in vivo as evidenced by the facilitated cutaneous wound healing [PMC196881, PMID: 29474864, PMC4684472].
Since one of the factors contributing to the rejuvenation of cells with the formation of (CRC) is Δ133p53α (a natural p53 isoform), which induces hTERT expression and telomerase activity [PMC6030220] (for maintaining or elongating telomeres, thus extending their Hayflick limit), it would be interesting to test its effect in vivo in combination with ROCK inhibitor.
Since overexpression of Δ133p53 dominantly suppresses the expression of pro-inflammatory cytokines associated with aging (SASP) and also contributes to the repair of DNA damage [PMC5988805, PMC3039296], it was proposed to combat premature aging in children with progeria (Hutchinson-Gilford syndrome) [PMC5954431]. Given the fact that in the process of replicative aging, Δ133p53α is destroyed by autophagy [PMID: 25144556] (the case where selective autophagy promotes aging [PMC6332805]), replenishing the Δ133p53α pool can be useful for replenishing the pool and rejuvenating stem cells.
So far, no one has studied the effect of such ROCK inhibitors like fasudil on the lifespan of old mice. Nobody has investigated combinations of ROCK inhibitors with recombinant Δ133p53α on the lifespan of old mice. A possible obstacle to the successful increase in life expectancy by this method may be an autoimmune disease. But with not very long treatment courses, the likelihood of such an exacerbation is negligible. Unlike Δ133p53β and Δ133p53γ isoforms, which are able to induce cell reprogramming into iPScs even in the absence of Yamanaki factors (and therefore capable of causing teratoma development), the Δ133p53α isoform does not allow inducing iPScs in the absence of exogenous Yamanaki factors and therefore is safer for in vivo use [http://www.freepaten...8/0023056.html]. Moreover, usually non-malignant epithelial cells preferentially proliferate when cultured under conditionally reprogrammed conditions [PMC5727117, PMC5355251].
