Cellular and molecular basis for the action of retinoic acid in spermatogenesis

Spermatogenesis is a highly organized and regulated process that requires the constant production of millions of gametes over the reproductive lifetime of the mammalian male. This is possible because of an active stem cell pool and an ordered entry into the germ cell developmental sequence. The ordered entry is a result of the synthesis and action of retinoic acid allowing for the onset of spermatogonial differentiation and an irreversible commitment to spermatogenesis. The periodic appearance and actions of retinoic acid along the seminiferous tubules is a result of the interactions between germ cells and Sertoli cells that result in the generation and maintenance of the cycle of the seminiferous epithelium and is the subject of this review.

Retinoid signaling regulates angiogenesis and blood-retinal barrier integrity in neonatal mouse retina

OBJECTIVE

The neonatal mouse retina is a well-characterized experimental model for investigating factors impacting retinal angiogenesis and inner blood-retinal barrier (BRB) integrity. Retinoic acid (RA) is an essential signaling molecule. RA is needed for vasculogenic development in embryos and endothelial barrier integrity in zebrafish retina and adult mouse brain, however the function of this signaling molecule in developing mammalian retinal vasculature remains unknown. This study aims to investigate the role of RA signaling in angiogenesis and inner BRB integrity in mouse neonatal retina.

METHODS

RA distribution in the developing neurovascular retina was assessed in mice carrying an RA-responsive transgene. RA function in retinal angiogenesis was determined by treating C57BL/6 neonatal pups with a pharmacological inhibitor of RA signaling BMS493 or control vehicle. BRB integrity assessed by monitoring leakage of injected tracer into extravascular retinal tissue.

RESULTS

RA signaling activity is present in peripheral astrocytes in domains corresponding to RA activity of the underlying neural retina. RA inhibition impaired retinal angiogenesis and reduced endothelial cell proliferation. RA inhibition also compromised BRB integrity. Vascular leakage was not associated with altered expression of CLDN5, PLVAP, LEF1 or VEcad.

CONCLUSIONS

RA signaling is needed for angiogenesis and integrity of the BRB in the neonatal mouse retina.

Global Deletion of ALDH1A1 and ALDH1A2 Genes Does Not Affect Viability but Blocks Spermatogenesis

The transition of undifferentiated A spermatogonia to differentiated spermatogonia requires the action of retinoic acid (RA). The synthesis of retinoic acid from retinal in the seminiferous epithelium is a result of the action of aldehyde dehydrogenases termed ALDH1A1, ALDH1A2, and ALDH1A3. We used a mouse with a global deletion of the Aldh1a1 gene that is phenotypically normal and the CRE-loxP approach to eliminate Aldh1a2 genes globally and from Sertoli cells and germ cells. The results show that global elimination of Aldh1a1 and Aldh1a2 genes blocks spermatogenesis but does not appear to affect viability. The cell specific elimination of Aldh1a2 gene showed that retinoic acid synthesis by Sertoli cells is required for the initial round of spermatogonial differentiation but that there is no requirement for retinoic acid synthesis by germ cells. In both the global gene deletion and the cell specific gene deletions the maintenance of Aldh1a3 activity could not compensate.

A single center, pilot, double-blinded, randomized, comparative, prospective clinical study to evaluate improvements in the structure and function of facial skin with tazarotene 0.1% cream alone and in combination with GliSODin(®) Skin Nutrients Advanced Anti-Aging Formula

Background

Superoxide dismutase (SOD) reduces the reactive oxygen species formation associated with oxidative stress. An imbalance between free radicals and antioxidants can lead to accelerated aging. GliSODin^® Skin Nutrients Advanced Anti-Aging Formula (GAAF) is an SOD-containing dietary nutricosmetic formulated with other nutraceuticals that promote improvements in the structure and function of the skin, including hydration, elasticity, structural integrity, and photoaging caused by oxidative stress. Tazarotene cream 0.1% (TAZ) is a United States Food and Drug Administration-approved drug indicated for use in the mitigation of facial fine wrinkling, facial mottled hyper- and hypopigmentation, and benign facial lentigines when taken in conjunction with a comprehensive skin care and sun avoidance program.

Objective

To determine if the antioxidant, anti-aging, hydrating and skin-rejuvenating properties of GAAF complement the retinoic actions of TAZ to improve the structure and function of facial skin.

Method

A 90-day comparative study of ten subjects with facial photodamage; daily topical application of TAZ was used in combination with three capsules of GAAF (780 mg each) or placebo orally, with food, per the randomization allocation.

Results

After 90 days of treatment, TAZ alone and in combination with GAAF improved fine wrinkles (↓1.2 versus 2.0), mottled hyperpigmentation (↓2.2 versus 2.8) and overall photodamage (↓1.0 versus 1.8), as well as patient-reported response to treatment (↓2.0 versus 1.6). At week 12, TAZ/GAAF combination treatment (Group A) versus TAZ treatment alone (Group C) was of significant clinical benefit, with respect to fine wrinkling (14.7%/41.7%), overall photodamage (15.6%/53.0%), skin moisture (19.1%/103.2%), skin elasticity (12.8%/87.7%), and response to treatment (8.8%/21.4%).

Conclusion

The study suggests GAAF in combination with TAZ is safe and provides significant clinical benefit with relative improvement in facial fine wrinkling, overall photodamage, skin moisture and elasticity.