Foxp3⁺ Regulatory T Cell Expression of Keratinocyte Growth Factor Enhances Lung Epithelial Proliferation

Abstract

Repair of the lung epithelium after injury is a critical component for resolution; however, the processes necessary to drive epithelial resolution are not clearly defined. Published data demonstrate that Foxp3 regulatory T cells (Tregs) enhance alveolar epithelial proliferation after injury, and Tregs in vitro directly promote type II alveolar epithelial cell (AT2) proliferation, in part by a contact-independent mechanism. Therefore, we sought to determine the contribution of Treg-specific expression of a growth factor that is known to be important in lung repair, keratinocyte growth factor (kgf). The data demonstrate that Tregs express kgf and that Treg-specific expression of kgf regulates alveolar epithelial proliferation during the resolution phase of acute lung injury and in a model of regenerative alveologenesis in vivo. In vitro experiments demonstrate that AT2 cells cocultured with Tregs lacking kgf have decreased rates of proliferation compared with AT2 cells cocultured with wild-type Tregs. Moreover, Tregs isolated from lung tissue and grown in culture express higher levels of two growth factors that are important for lung repair (kgf and amphiregulin) compared with Tregs isolated from splenic tissue. Lastly, Tregs isolated from human lung tissue can be stimulated ex vivo to induce kgf expression. This study reveals mechanisms by which Tregs direct tissue-reparative effects during resolution after acute lung injury, further supporting the emerging role of Tregs in tissue repair.

‘Repair’ Treg Cells in Tissue Injury

“…It has been reported that KGF expression on Tregs can be induced by LPS, which suggests that Tregs have the ability to express KGF under stimulated conditions [64]. Lung Tregs express higher levels of KGF than those from the spleen, which could be stimulated by TCR stimulation, and they failed to further augment expression by addition of IL-18 or IL-33 [65].…”

“…Lung Tregs express higher levels of KGF than those from the spleen, which could be stimulated by TCR stimulation, and they failed to further augment expression by addition of IL-18 or IL-33 [65]. In addition, Treg can be regulated by KGF.…”

“…Data have demonstrated that transfer of KGF - Tregs failed to augment epithelial proliferation after acute lung injury in Treg-depleted mice [64]. KGF + Tregs promoted alveolar epithelial proliferation both during the resolution phase in an experimental model of lung injury and during regenerative alveologenesis following pneumonectomy [65].…”

“…KGF + Tregs promoted alveolar epithelial proliferation both during the resolution phase in an experimental model of lung injury and during regenerative alveologenesis following pneumonectomy [65]. Type II alveolar epithelial cells (AT2) co-cultured with KGF - Tregs proliferated less than AT2 cells co-cultured with wild-type Tregs [65].…”

Inhibition of glutamine metabolism accelerates resolution of acute lung injury

“…Lung tissue was processed to form a single cell suspension and immunostained to identify cell types as previously described (Dial et al. ). Antibodies were obtained from Biolegend (San Diego, CA): CD45 FITC (clone 30‐F11), SiglecF PE (clone E50‐2440), Annexin V PerCP‐Cy5.5 (catalog 640936), CD64 PE‐Cy7 (clone X54‐5/7.1), Ly6G APC (clone 1A8), CD3 FITC (clone 145‐2C11), CD45 Alexa Fluor 700 (clone 30‐F11), CD4 PB (clone GK1.5), Foxp3 Alexa Fluor 647 (clone 150D), Zombie Aqua™ (catalog 423102); from BD Horizon (Waltham, MA): Ly6C BV421 (clone AL‐21); and from BD Pharmingen (Waltham, MA): CD16/CD32 Mouse BD Fc block™ (clone 2.462).…”