Just because of the Growth in the name IGF2 do not assume anything about it.

Paternal Insulin-like Growth Factor 2 (Igf2) Regulates Stem Cell Activity During Adulthood.

“Insulin-like Growth Factor 2 (IGF2) belongs to the IGF/Insulin pathway, a highly conserved evolutionarily network that regulates growth, aging and lifespan. Igf2 is highly expressed in the embryo and in cancer cells. During mouse development, Igf2 is expressed in all sites where hematopoietic stem cells (HSC) successively expand, then its expression drops at weaning and becomes undetectable when adult HSC have reached their niches in bones and start to self-renew. In the present study, we aim to discover the role of IGF2 during adulthood. We show that Igf2 is specifically expressed in adult HSC and we analyze HSC from adult mice deficient in Igf2 transcripts. We demonstrate that Igf2 deficiency avoids the age-related attrition of the HSC pool and that Igf2 is necessary for tissue homeostasis and regeneration. Our study reveals that the expression level of Igf2 is critical to maintain the balance between stem cell self-renewal and differentiation, presumably by regulating the interaction between HSC and their niche. Our data have major clinical interest for transplantation: understanding the changes in adult stem cells and their environments will improve the efficacy of regenerative medicine and impact health- and life-span.”<-This is interesting as we would except increasing IGF2 levels to be anti-aging but stimulating existing stem cells with IGF2 could potentially help stimulate new growth plate formation.  Stem cells are supposed to be used so decrementing that pool to use them for functions is not necessarily a bad thing.

“[IGF2] is highly expressed in all sites where hematopoietic stem cells (HSC) successively migrate and expand during development ”

“In adult mice, Igf2 appears to be re-expressed in specific cell types during regeneration ”

“As a potent mitogen, IGF2 has been shown in vivo to promote regeneration of tissue mass by increasing cells numbers, and in vitro to expand fetal and adult stem cell populations. Insulin-like growth factor 2 expressed in a novel foetal liver cell population is a growth factor for hematopoietic stem cells. An increase in IGF2 can lead to organ overgrowth ”

“deleting the main paternal Igf2 transcription unit in mice, results in Igf2 deficiency and growth retardation ”

IGF2-deficient HSC may have deregulated interaction with their bone marrow stem cell niche.

IGF2P2 is an IGF promoter.

IGF2P2 deficiency decreased the mobilization of stem cells and progenitors which resulted in higher anchoring of IGF2B2 cells to the BM stroma so again less stem cells being used.

The scientists found that lower IGF2 levels resulted in lower differentiation.  So maybe you only want high IGF2 levels during short bursts of time to allow HSCs to recover.