The conjunctival extracellular matrix, related disorders and development of substrates for conjunctival restoration.

The conjunctiva can be damaged by numerous diseases with scarring, loss of tissue and dysfunction. Depending on extent of damage, restoration of function may require a conjunctival graft. A wide variety of biological and synthetic substrates have been tested in the search for optimal conditions for ex vivo culture of conjunctival epithelial cells as a route toward tissue grafts. Each substrate has specific advantages but also disadvantages related to their unique physical and biological characteristics, and identification and development of an improved substrate remains a priority. To achieve the goal of mimicking and restoring a biological material, requires information from the material. Specifically, extracellular matrix (ECM) derived from conjunctival tissue. Knowledge of the composition and structure of native ECM and identifying contributions of individual components to its function would enable using or mimicking those components to develop improved biological substrates. ECM is comprised of two components: basement membrane secreted predominantly by epithelial cells containing laminins and type IV collagens, which directly support epithelial and goblet cell adhesion differentiation and growth and, interstitial matrix secreted by fibroblasts in lamina propria, which provides mechanical and structural support. This review presents current knowledge on anatomy, composition of conjunctival ECM and related conjunctival disorders. Requirements of potential substrates for conjunctival tissue engineering and transplantation are discussed. Biological and synthetic substrates and their components are described in an accompanying review.

Biological tissues and components, and synthetic substrates for conjunctival cell transplantation.

The conjunctiva is the largest component of the ocular surface. It can be damaged by various pathological processes leading to scarring, loss of tissue and dysfunction. Depending on the amount of damage, restoration of function may require a conjunctival graft. Numerous studies have investigated biological and synthetic substrates in the search for optimal conditions for the ex vivo culture of conjunctival epithelial cells that can be used as tissue grafts for transplantation. These substrates have advantages and disadvantages that are specific to the characteristics of each material; the development of an improved material remains a priority. This review is the second of a two-part review in The Ocular Surface. In the first review, the structure and function of the conjunctiva was evaluated with a focus on the extracellular matrix and the basement membrane, and biological and mechanical characteristics of the ideal substrate with recommendations for further studies. In this review the types of biological and synthetic substrates used for conjunctival transplantation are discussed including substrates based on the extracellular matrix. .

Mass Spectrometry Reveals α-2-HS-Glycoprotein as a Key Early Extracellular Matrix Protein for Conjunctival Cells.

Purpose: To determine the composition of extracellular matrix (ECM) proteins secreted by a conjunctival epithelial cell line and to identify components that aid conjunctival epithelial cell culture. Methods: Human conjunctival epithelial cell line (HCjE-Gi) cells were cultured in serum-free media and their ECM isolated using ammonium hydroxide. Growth characteristics were evaluated for fresh HCjE-Gi cells plated onto ECMs obtained from 3- to 28-day cell cultures. Mass spectrometry was used to characterize the ECM composition over 42 culture days. Cell adhesion and growth on pre-adsorbed fibronectin and α-2-HS-glycoprotein (α-2-HS-GP) were investigated. Results: Day 3 ECM provided the best substrate for cell growth compared to ECM obtained from 5- to 28-day cell cultures. Mass spectrometry identified a predominantly laminin 332 matrix throughout the time course, with progressive changes to matrix composition over time: proportional decreases in matrix-bound growth factors and increases in proteases. Fibronectin and α-2-HS-GP were 5- and 200-fold enriched as a proportion of the early ECM relative to the late ECM, respectively. Experiments on these proteins in isolation demonstrated that fibronectin supported rapid cell adhesion, whereas fibronectin and α-2-HS-GP both supported enhanced cell growth compared to tissue culture polystyrene. Conclusions: These data reveal α-2-HS-GP as a candidate protein to enhance the growth of conjunctival epithelial cells and raise the possibility of exploiting these findings for targeted improvement to synthetic tissue engineered conjunctival substrates.