Studying Monocyte-Myofibroblast Immunomodulation in a 3D Co-culture System

Simple and reproducible 3D cell culture systems that mimic biological interactions within physiological tissues (biomimetics) can provide unique insight for scientific inquiries compared to 2D cell cultures. Fibroblast-populated collagen lattices (FPCLs) are commonly used for mimicking physiological collagen matrices, potentiating biomechanical stresses on embedded fibroblasts. Here, we describe a novel 3D co-culture model that incorporates human Tenon's capsule fibroblasts embedded in FPCLs co-cultured with THP-1 monocytes suspended in culture media. This method can be used for the assessment of cell-cell interactions in various stages of the wound healing process and can facilitate various types of immune cells in co-culture. This system can also be used to study pharmacological agents that may eventually improve clinical outcomes in patients affected by inflammatory disorders.

Understanding Inflammation-associated Ophthalmic Pathologies: A Novel 3D Co-culture Model of Monocyte-myofibroblast Immunomodulation

PURPOSE

Inflammation is associated with, and may be causal of, a variety of ophthalmic pathologies. These pathologies are currently difficult to model in vitro because they involve complex interactions between the innate immune system, stromal cells, and other cells that normally maintain ocular tissue homeostasis. Using transscleral drainage channel fibrosis after glaucoma surgery as an example of inflammation-associated ocular fibrosis, we have assessed a simple but novel 3D cell culture system designed to reveal the immunomodulatory impacts of ocular connective tissue cells on monocytes, a major cellular component of the circulating immune system.

METHODS

Primary human Tenon's capsule fibroblasts derived from five unrelated patients were activated into myofibroblasts in 3D collagen matrices under isometric tension, with and without exposure to an inflammatory cytokine-enhanced milieu, and co-cultured with an immortalized human monocyte cell line (THP-1 cells). Quantitative PCR analyses were performed on 8 candidate genes to assess the impacts of inflammatory cytokines on the myofibroblasts and the monocytes in mono-cultures and compared to cells in co-culture to clearly distinguish any co-culture-induced impacts on gene expression.

RESULTS

Our data indicate that both Tenon's capsule myofibroblasts in 3D mono-culture and THP-1 monocytes in suspension mono-culture were responsive to inflammatory cytokine stimuli. Co-culture with Tenon's capsule myofibroblasts significantly modulated the gene expression responses of THP-1 monocytes to inflammatory cytokine stimulation, indicative of an immunomodulatory "feedback" system between these cell types.

CONCLUSION

Our findings provide proof of principle for the use of simple 3D co-culture systems as a means to enhance our understanding of ocular stromal cell interactions with cells of the innate immune system and to provide more informative in vitro models of inflammation-associated ophthalmic pathologies.

The long form of pVHL is artifactually modified by serine protease inhibitor AEBSF

von Hippel-Lindau protein (pVHL) is the tumor suppressor responsible for ubiquitylating the hypoxia-inducible factor (HIF) family of transcription factors for degradation under normoxic conditions. There are two major pVHL isoforms with the shorter isoform (pVHL₁₉ ) lacking the acidic domain present in the N-terminus of the longer isoform (pVHL₃₀ ). Although both isoforms can degrade HIF and suppress tumor formation in experimental systems, previous research suggests that pVHL₃₀ can undergo posttranslational modifications (PTM) and interact with unique proteins. Indeed, pVHL₃₀ has long been observed to migrate as two species on a reducing polyacrylamide gel, indicating the presence of an uncharacterized PTM on the slower-migrating pVHL₃₀ without an identifiable biological consequence. Thus, there has been considerable effort to elucidate the exclusive biological activity of pVHL₃₀ , if any, by first defining the unique features of the slower-migrating species. We show here that the migration of pVHL₃₀ , but not pVHL₁₉ , is retarded by 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride (AEBSF), an irreversible serine protease inhibitor commonly found in protease inhibitor cocktails.