Radiation-induced FAP + fibroblasts are involved in keloid recurrence after radiotherapy

Should We Do Postoperative Radiotherapy After Keloid Excision as Soon as Possible? A Systematic Review and Meta-Analysis

BACKGROUND

There is no consensus on the timing of postoperative radiotherapy for keloid.

OBJECTIVE

We conducted this meta-analysis to investigate the appropriate time of radiotherapy for keloid in the first 24 hours after operation and identify the potential risk factors.

MATERIALS AND METHOD

A systematic review and meta-analysis were conducted on observational studies by searching PubMed, Embase, and the Cochrane Library. The pooled estimate of the keloid recurrence rate was calculated using a random-effects model. Subgroup analyses were conducted based on time, overtime, BED, length, and location of keloid.

RESULTS

Eight observational studies with 507 keloids met the inclusion criteria, and 7 studies were finally included in this study after sensitivity analysis. The recurrence rate was lower in the 2 hours postoperative radiotherapy group (7% CI 2-14%) than in the 6 hours postoperative radiotherapy group (16%, CI 3-36%) (P<0.01). In HDR subgroup analysis, the 2 hours group was better than the 6 hours group ((5%, CI 1-14%) versus (16%, CI 3-36.1%) (P<0.01). Subgroup analysis based on BED indicated that the BED 30 group (5%, CI 1-14%) had a lower recurrence rate than the BED 20 group (6%, CI 0-21%) and the BED 15 group (26%, CI 19-33%) (P<0.01). The keloid length >5 cm subgroup (10.4%, CI 0.4-29%) showed a higher recurrence rate than the keloid length <5 cm group (9.9%, CI 0-41%) (P=0.011).

CONCLUSION

Immediate postoperative radiotherapy within 2 hours significantly decreased recurrence rate than postoperative radiotherapy within 6 hours.

LEVEL OF EVIDENCE I

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Fibroblast Activation Protein Alpha (FAPα) in Fibrosis: Beyond a Perspective Marker for Activated Stromal Cells?

The development of tissue fibrosis is a complex process involving the interaction of multiple cell types, which makes the search for antifibrotic agents rather challenging. So far, myofibroblasts have been considered the key cell type that mediated the development of fibrosis and thus was the main target for therapy. However, current strategies aimed at inhibiting myofibroblast function or eliminating them fail to demonstrate sufficient effectiveness in clinical practice. Therefore, today, there is an unmet need to search for more reliable cellular targets to contribute to fibrosis resolution or the inhibition of its progression. Activated stromal cells, capable of active proliferation and invasive growth into healthy tissue, appear to be such a target population due to their more accessible localization in the tissue and their high susceptibility to various regulatory signals. This subpopulation is marked by fibroblast activation protein alpha (FAPα). For a long time, FAPα was considered exclusively a marker of cancer-associated fibroblasts. However, accumulating data are emerging on the diverse functions of FAPα, which suggests that this protein is not only a marker but also plays an important role in fibrosis development and progression. This review aims to summarize the current data on the expression, regulation, and function of FAPα regarding fibrosis development and identify promising advances in the area.

Tissue RNA Sequencing Reveals Novel Biomarkers Associated with Postoperative Keloid Recurrence

Keloids can be resected through surgery, but they may still recur. The purpose of this study was to explore the biomarkers to predict the postoperative recurrence of keloids. Patients who underwent surgical treatment and postoperative superficial X-ray radiation between January 2019 and December 2020 were recruited with clinical data and keloid samples for RNA-seq. By screening differentially expressed genes (DEGs) between postoperative recurrent and non-recurrent sample groups and constructing a co-expression network via the weighted gene co-expression network analysis (WGCNA), an immunity-related module was chosen for subsequent analysis. By constructing a DEG co-expression network and using the Molecular Complex Detection (MCODE) algorithm, five hub genes were identified in the key module. Receiver Operating Characteristic (ROC) curve analysis showed that the area under the curve (AUC) for the five combined hub genes was 0.776. The result of qRT-PCR showed that CHI3L1, IL1RN, MMP7, TNFAIP3, and TNFAIP6 were upregulated in the recurrent group with statistical significance (p < 0.05). Immune infiltration analysis showed that mast cells, macrophages, and T cells were the major components of the keloid immune microenvironment. This study provides potential biomarkers for predicting keloid recurrence and offers insights into genetic targets for recurrence prevention.