Adipose Derived Mesenchymal Stem Cell Characteristics in Anal Fistulas

Identification of Molecular Differences of Adipose-derived Mesenchymal Stem Cells Between Non- Responders and Responders in Treatment of Transsphincteric Perianal Fistulas Using Autologous Fat Graft Injection

This study investigated the cellular and molecular characteristics of AT-MSCs obtained from autologous AT therapy in patients with high transphincteric perianal fistulas of crytoglandular origin. Adipose tissue was injected into anal fistulas. Characteristics of adipose tissue mesenchymal stemcells (AT-MSC) was investigated and compared in patients with fistula that healed after the treatment (responders) to patients who failed to heal (non-responders)

Injection with allogene or autologous stem cells has been reported to be efficient treatment of perianal fistulas. An alternative to this treatment could be injection with freshly collected autologous adipose tissue. In this study 27 patients with cryptoglandular anal fistulas were treated with freshly collected autologous adipose tissue.A clinical assessment of the patient prior to inclusion was undertaken and a loose seton placed for at least 6 weeks prior to fat injection. An MRI of the pelvis was performed before inclusion. Fistulas with secondary tracts and/or cavities were excluded. The operation was performed in one procedure including liposuction and injection of adipose tissue. A sample of adipose tissue from all 27 patients was analyzed. AT-MSCs were isolated and characterized using cellular and molecular analyses. Clinical and MRI-scanning evaluation of fistula healing and evaluation of ano-rectal function was performed after 6 months. AT-MSCs phenotype was compared between responders and non-responders with respect to fistula healing. The evaluation of the AT-MSCs was performed in a blinded manner.

Characterisation of adipose tissue (AT-MSCs) was performed blinded to the result of the treatment responder/non-responder

Differentiation potential of AT-MSCs: to differentiate into adipocyte measured by Oil-Red O staining and gene expression of adipogenic markers (PPARg and LPL normalized to housekeeping gene beta actin) presented as a Fold change to undifferentiated cells (arbitrary units)

Differentiation potential of AT-MSCs: to differentiate into osteoblast measured by Alizarin S staining and gene expression of osteogenic markers (BGALP and RUNX2 normalized to housekeeping gene beta actin) presented as a Fold change to undifferentiated cells (arbitrary units)

Gene expression of proinflammatory (NFKB, TNFa, IL1B, IL6) and senescence associated molecules(CDKN2A, TP53, TGFB1, VEGFA, IFNG, IL6) of AT-MSCs in relation to the outcome of fistula treatment (i.e. comparison between responders and non-responders). The data are normalized to housekeeping gene beta actin (arbitrary units)

Clinical healing defined as closure of the internal and external fistula opening and no discharge evaluated as success rate of the healing in (%)

A combination of Clinical and MRI healing defined as closure of the internal and external fistula opening and no discharge and no fluid filled fistula tracts on evaluated as success rate of the healing in (%)

Inclusion Criteria: high trans-sphincteric fistulas fistula confirmed and classified by an MRI. seton (> 6 weeks) prior to fat injection informed, written consent. Exclusion Criteria: Anovaginal fistula Active sepsis IBD, immunodeficiency, prior pelvic irradiation and malignancy Insulin dependent diabetes More than 4 prior attempts of fistula closure Tobacco smoking or nicotine substitution 8 weeks prior to fat injection. Pregnancy Psychiatric disorders BMI ≥ 35 or BMI<20 Active tuberculosis Patient less than 18 years Unable to undergo MRI

Tencerova M, Lundby L, Buntzen S, Norderval S, Hougaard HT, Pedersen BG, Kassem M. Molecular differences of adipose-derived mesenchymal stem cells between non-responders and responders in treatment of transphincteric perianal fistulas. Stem Cell Res Ther. 2021 Nov 24;12(1):586. doi: 10.1186/s13287-021-02644-8.