Human cell–silk fibroin interactions: relevance to biocompatibility and regeneration

Background:
Exogenous stem cells promote functional recovery after stroke.1 However, improved delivery technologies for these cells are needed to maximise their therapeutic potential.2 Self-assembling silk fibroin hydrogels are particularly promising in improving exogenous stem cell delivery in promoting brain repair due to their ease of application, broad biocompatibility, excellent space conformity and mechanical tuning,3 ultimately maximising regeneration.2To progress silk hydrogels towards clinical trials,2 there is the need to better understand host stroke tissue-hydrogel response.

Aim:
To investigate the biocompatibility and regenerative capacity of silk fibroin (SF) by monitoring the interactions with human mesenchymal stem cells (MSCs) and intrinsic cells (microglia). We aim to:
1. establish cellular viability of microglia and MSCs after exposure to SF;
1) investigate whether SF has anti-inflammatory, regenerative polarising effects on microglia and MSCs.

Method:
1) Human iPSCs-derived MSCs (ACS-7010) and microglia (HMC3) (2 × 104 cells/cm2) were dosed for 72h with 0–5mg/mL SF solution and cell viability was assessed via MTT assays (n = 4 per group).
2) MSCs and microglia (2 × 104 cells/cm2) were dosed for 72h with 0.1mg/mL SF and secreted proteins were assessed using human non-haematopoietic and common analytes proteome profilers (n = 2) to determine impact of SF exposure upon host cells.

Results/Conclusions:
Optimal concentration of silk fibroin (0.1mg/mL) was identified as non-toxic in both cell types (Figure 1). Preliminary proteomic data suggest 0.01mg/mL silk fibroin induced factor sections, including neural cell adhesion molecule L1-like protein and Jagged 1. These factors may aid in reprogramming the stroke cavity to promote stem cell payload survival and recovery after stroke.