Self-assembled human osseous cell sheets as living biopapers for the laser-assisted bioprinting of human endothelial cells.

A major challenge during the engineering of voluminous bone tissues is to maintain cell viability in the central regions of the construct. In vitro prevascularization of bone substitutes relying on endothelial cell bioprinting has the potential to resolve this issue and to replicate the native bone microvasculature. Laser-assisted bioprinting (LAB) commonly uses biological layers of hydrogel, called 'biopapers', to support patterns of printed cells and constitute the basic units of the construct. The self-assembly approach of tissue engineering allows the production of biomimetic cell-derived bone extracellular matrix including living cells. We hypothesized that self-assembled osseous sheets can serve as living biopapers to support the LAB of human endothelial cells and thus guide tubule-like structure formation. Human umbilical vein endothelial cells were bioprinted on the surface of the biopapers following a predefined pattern of lines. The osseous biopapers showed relevant matrix mineralization and pro-angiogenic hallmarks. Our results revealed that formation of tubule-like structures was favored when the cellular orientation within the biopaper was parallel to the printed lines. Altogether, we validated that human osseous cell sheets can be used as biopapers for LAB, allowing the production of human prevascularized cell-based osseous constructs that can be relevant for autologous bone repair applications.

The effect of estradiol, progesterone, and melatonin on estrous cycling and ovarian aromatase expression in intact female mice.

OBJECTIVE: Melatonin and progesterone levels decline during the perimenopause. Both hormones inhibit estrogen action and endometrial cancer, but little is known about how they act in combination. Therefore, the interplay of progesterone (P4) and melatonin was investigated in intact female mice. STUDY DESIGN: Three P4 doses, low (25mg), mid (50mg), and high (100mg), combined with 0.5mg 17ß-estradiol (E), were administered in the diet (per 1800kcal) for 30 days. Hormone therapy (HT) with the low P4 dose (estradiol/low progesterone replacement therapy (EPLRT)) was used to create an excess estrogen environment to mimic perimenopause. Half the mice were treated with melatonin (M) 15mg/L in the drinking water at night. RESULTS: The unbalanced EPLRT treatment increased estrogen-regulated responses. Specifically, mice treated with EPLRT had significantly higher levels of ovarian aromatase mRNA versus control, which was prevented in the presence of higher doses of P4 and/or the addition of melatonin. The number of days in estrus also increased in EPLRT-treated versus control mice with no change in the length or number of complete estrous cycles. Melatonin, combined with all doses of P4, increased the number of days spent in estrus, but not the length or number of estrous cycles compared to melatonin alone; however, two-way ANOVA revealed a significant interaction between melatonin and P4 dose for days in estrus and for number of cycles. Although none of the E2 and P4 combinations significantly affected uterine weight compared to control, melatonin addition to the low or mid P4 HT resulted in slightly higher uterine weights compared to melatonin-treated mice. Melatonin significantly increased uterine estrogen receptor alpha (ERα) and progesterone receptor A levels compared to control animals. HT, added in combination with melatonin, reduced ERα levels back to control levels, but PR levels remained elevated albeit intermediary to those achieved with melatonin alone. CONCLUSION: The findings that melatonin supplementation inhibits ovarian aromatase expression and increases uterine receptors in mice given an HT that mimics perimenopause may have important clinical applications for the improvement of menopause-related conditions, like menorrhagia, associated with high levels of E2 and low levels of P4.