Isolated Fragments of Intact Microvessels: Tissue Vascularization, Modeling, and Therapeutics

Mature and Juvenile Neuromuscular Plasticity in Response to Unloading

The neuromuscular junction (NMJ) is the synapse that enables the requisite electrical communication between the motor nervous system and the myofibers that respond to such electrical stimulation with movement and force development. Changes in an NMJ's normal activity pattern have been demonstrated to remodel both the synapse and the myofibers that comprise the NMJ. Significant amounts of research have been devoted to the study of aging on the neuromuscular system. Far less, however, has been focused on revealing the effects of reduced activity on the NMJ and myofibers comprising juvenile neuromuscular systems. In the present investigation, the consequences of decreased activity imposed by muscle unloading (UL) via hindlimb suspension for 2 weeks (a period known to induce muscle remodeling) were examined in both young adult, that is, mature (8 mo), and juvenile (3 mo) neuromuscular systems. In total, 4 treatment groups comprised of 10 animals (Juvenile-Control, Juvenile-Unloaded, Mature-Control, and Mature-Unloaded) were studied. Immunofluorescent procedures, coupled with confocal microscopy, were used to quantify remodeling of both the pre- and postsynaptic features of NMJs, as well as assessing the myofiber profiles of the soleus muscles housing the NMJs of interest. Results of ANOVA procedures revealed that there were significant (p < 0.05) main effects for both treatment, whereby UL consistently led to expanded size of the NMJ, and Age where expanded NMJ dimensions were consistently linked with mature compared to juvenile neuromuscular systems. Moreover, only sporadically was interaction between the main effects of Age and Treatment noted. Importantly, one variable that remained impressively resistant to the effects of both Age and Treatment was the critical parameter of pre- to postsynaptic coupling suggesting stability in effective communication at the NMJ throughout the lifespan and despite changes in activity patterns. The data presented here suggest that further inquiry must be performed regarding disuse-related plasticity of the neuromuscular system in adolescent individuals as those individuals regularly suffer injuries resulting in periods of muscle UL.

3D Bioprinted Coaxial Testis Model Using Human Induced Pluripotent Stem Cells:A Step Toward Bicompartmental Cytoarchitecture and Functionalization

Fertility preservation following pediatric cancer therapy programs has become a major avenue of infertility research. In vitro spermatogenesis (IVS) aims to generate sperm from banked prepubertal testicular tissues in a lab setting using specialized culture conditions. While successful using rodent tissues, progress with human tissues is limited by the scarcity of human prepubertal testicular tissues for research. This study posits that human induced pluripotent stem cells (hiPSCs) can model human prepubertal testicular tissue to facilitate the development of human IVS conditions. Testicular cells derived from hiPSCs are characterized for phenotype markers and profiled transcriptionally. HiPSC-derived testicular cells are bioprinted into core-shell constructs representative of testis cytoarchitecture and found to capture functional aspects of prepubertal testicular tissues within 7 days under xeno-free conditions. Moreover, hiPSC-derived Sertoli cells illustrate the capacity to mature under pubertal-like conditions. The utility of the model is tested by comparing 2 methods of supplementing retinoic acid (RA), the vitamin responsible for inducing spermatogenesis. The model reveals a significant gain in activity under microsphere-released RA compared to RA medium supplementation, indicating that the fragility of free RA in vitro may be a contributing factor to the molecular dysfunction observed in human IVS studies to date.

Isolated human adipose microvessels retain native microvessel structure and recapitulate sprouting angiogenesis

With interest growing in modeling more complex aspects of human disease in the laboratory, the need for effectively vascularizing human tissue models is becoming paramount. However, fully recreating human tissue microvasculatures is challenging given the multicellular complexity of the microvessel and microvessel-tissue interplay. Importantly, effective models should capture the dynamic activity of the perivascular cells of the perivascular niche, which are critical to tissue hemostasis and function. Isolated microvessel fragments from rodent adipose have been extensively studied and used in a variety of vascularization models. We have progressed this proven technology by deriving isolated fragments of intact human microvessels harvested from adipose (haMVs) to model human vascularization and advance human vascularized tissue models. Here we show the haMVs retain native microvessel structures, including perivascular cellularity, and recapitulate bona fide sprouting angiogenesis in vitro through distinct sprouting and neovessel elongation phases. As primary isolates, the angiogenic potential varies between donor lots and correlates with the presence of haMV perivascular cells. In an in vitro model of tumor angiogenesis, the addition of anti-tumor agents impacted tumor cell expansion in the presence of the haMVs but not endothelial cells alone demonstrating the importance of the perivascular cells in tissue modeling. The human adipose microvessels offer, in a single reagent, a more complex, dynamic human tissue model vascularization solution.