Research Projects

We thank our funding agencies for supporting us!

NIBIB National Institute of Biomedical Imaging and Bioengineering: R01EB020233

NSF National Science Foundation : NSF CAREER, NSFGRF

The Hartwell Foundation

Overview

Some of the most important properties for a hydrogel to be considered ideal for biomedical applications include cell recognition, biodegradability, elasticity, and biocompatible chemistry in physiological conditions. Historically, fibrin and collagen have been used as “gold standard” scaffolds in regenerative medicine because they possess many of the critical biological functions, such as matrix-to-cell adhesion and biodegradation, but suffer from poor mechanical properties and limited range of chemical and structural modification to fit specific applications. On the other hand, the biological inertness of synthetic polymers, such as poly(ethylene glycol) (PEG), results in minimal cell invasiveness, slow degradation and poor scaffold remodeling. One approach to improve the physico-chemical properties of the biomaterials is designing inter-penetrating network of two or more components, in which one component can contribute biological activity and the other provides physical strength and structural support. Another approach involves multifunctional hydrophilic polymers, such as PEG and alginate. Chemical incorporation of the necessary biological functions, while preserving their initial elastic behavior qualifies these polymers for wide application spectrum.


Design of 3D hydrogel system for ovarian follicle culture

The need for fertility preservation in females facing anticancer therapies provides an opportunity to use biomaterials in the field of reproductive biology. Presently, there are no in vitro technologies that can support the maturation of the immature female germ cell, the oocyte, into the developmental stage that can be used for in vitro fertilization (IVF) and the creation of offspring beyond the laboratory mouse. We synthesize and design biomaterials that can support healthy development of the immature ovarian follicle, while preserving its 3D architecture.



Development of the artificial ovary

Ovarian tissue transplantation is another alternative to in vitro follicle culture for fertility preservation, yet it bears the risk of re-introduction of cancer cells and suffers from inconsistent graft longevity. We aim to engineer an artificial ovary from individually isolated follicles through creative matrix design, incorporating supportive cells, ECM and other biological cues to ensure successful tissue remodeling after transplantation.

peg-implants-jiwon


Transcription factor activity during the development of early-stage ovarian follicles

Ovarian follicles are the functional units of the ovary and are responsible for a woman’s fertility and ovarian endocrine function. Currently, young women and prepubertal girls facing cancer diagnosis have limited options to preserve their fertility, with cryopreservation of ovarian tissue prior to chemotherapy the best available option. The challenge is that the vast majority of the follicles that survive the cryopreservation are early-stage primary and primordial follicles, and the subsequent success rate of their development and maturation in vitro is very low. These low success rates are attributed to the complex and poorly understood paracrine, autocrine and endocrine signaling between the cells in a follicle. Our goal is to identify the key signals and transcription factor activity during early stage follicle development that will  result in a culture system design that maximizes follicle growth, health, and development. The images below demonstrate the Luciferase activity and the quantitative analysis of the normalized activity of the TFs (p53, NF-κB, GL1) in transfected follicles co-cultured in groups on days 2, 4 and 7. 

untitled tracer


In vitro toxicology screening system

The effect of various chemicals is tested in high-throughput screening assays, including cell-free biochemical and cell-based assays measuring direct molecular interactions. We aim to design a test system for the toxic effect of chemicals on folliculogenesis, because of its importance to reproductive ability and the continuous effect on offspring.

HongsPublicationFig1


 

In vitro system mimicking cell–cell and cell–matrix interactions in secondary lymphoid organs (SLOs)

To model T-cell interaction in SLOs in vitro, we encapsulated stromal cells in fibrin, collagen, or fibrin–collagen hydrogels and studied how different mechanical and biological properties affect stromal network formation. Overall, fibrin supplemented with aprotinin was superior to collagen and fibrin-collagen in terms of network formation and promotion of T-cell penetration. After 8 days of culture, stromal networks formed through branching and joining with other adjacent cell populations. T-cells added to the newly formed stromal networks migrated and attached to stromal cells, similar to the T-cell zones of the lymph nodes in vivo. Our results suggest that the constructed three-dimensional lymphoid stromal network can mimic the in vivo environment and allow the modeling of T-cell interaction in SLOs.