Perianal fistulizing Crohn's disease: Current perspectives on diagnosis, monitoring and management with a focus on emerging therapies.

Crohn's disease (CD), a chronic inflammatory bowel disorder, manifests in various phenotypes, with fistulizing perianal CD (CD-PAF) being one of its most severe phenotypes. Characterized by fistula formation and abscesses, CD-PAF impacts 17% to 34% of all CD cases and with a significantly deleterious impact on patient's quality of life, while increasing the risk for anorectal cancers. The pathogenesis involves a complex interplay of genetic, immunological and environmental factors, with cytokines such as tumor necrosis factor-alpha (TNF-α) and transforming growth factor-beta (TGF-ß) playing pivotal roles. Diagnostic protocols require a multi-disciplinary approach including colonoscopy, examination under anesthesia and magnetic resonance imaging. In terms of treatment, biologics alone often prove inadequate, making surgical interventions such as setons and fistula surgeries essential. Emerging therapies such as mesenchymal stem cells are under study. The South Asian context adds layers of complexity, including diagnostic ambiguities related to high tuberculosis prevalence, healthcare access limitations and cultural stigma toward perianal Crohn's disease and ostomy surgery. Effective management necessitates an integrated, multi-disciplinary approach, especially in resource-constrained settings. Despite advances, there remain significant gaps in understanding the disease's pathophysiology and a dearth of standardized outcome measures, underscoring the urgent need for comprehensive research.

[Clinical characteristics and prognosis of children with perianal fistulizing Crohn's disease]. / å„¿ç«¥è‚›å‘¨ç˜˜ç®¡åž‹å ‹ç½—æ©ç— çš„ä¸´åºŠç‰¹å¾åŠé¢„åŽ.

OBJECTIVES: To investigate the clinical characteristics, treatment, and prognosis of children with perianal fistulizing Crohn's disease (pfCD). METHODS: A retrospective analysis was conducted on the children, aged 6-17 years, who were diagnosed with Crohn's disease (CD) from April 2015 to April 2023. According to the presence or absence of perianal fistulizing lesions, they were divided into two groups: pfCD (n=60) and non-pfCD (n=82). The two groups were compared in terms of clinical characteristics, treatment, and prognosis. RESULTS: The incidence of pfCD was 42.3% (60/142). The proportion of males in the pfCD group was higher than that in the non-pfCD group. Compared with the non-pfCD group, the pfCD group had a significantly higher proportion of children with involvement of the colon and small intestine or those with upper gastrointestinal lesions (P<0.05). Compared with the non-pfCD group, the pfCD group had a significantly higher rate of use of infliximab during both induction and maintenance treatment (P<0.05). In the pfCD group, the children with complex anal fistula accounted for 62% (37/60), among whom the children receiving non-cutting suspended line drainage accounted for 62% (23/37), which was significantly higher than the proportion among the children with simple anal fistula patients (4%, 1/23) (P<0.05). There were no significant differences between the two groups in mucosal healing rate and clinical remission rate at week 54 of treatment (P>0.05). The pfCD group achieved a fistula healing rate of 57% (34/60) at week 54, and the children with simple anal fistula had a significantly higher rate than those with complex anal fistula (P<0.05). CONCLUSIONS: There is a high incidence rate of pfCD in children with CD, and among the children with pfCD, there is a high proportion of children with the use of biological agents. There is a high proportion of children receiving non-cutting suspended line drainage among the children with complex anal fistula. The occurrence of pfCD should be closely monitored during the follow-up in children with CD.

A phase IB/IIA study of ex vivo expanded allogeneic bone marrow-derived mesenchymal stem cells for the treatment of rectovaginal fistulizing Crohn's disease.

BACKGROUND: Crohn-related rectovaginal fistulas are notoriously difficult to treat. Studies of mesenchymal stem cells for the treatment of perianal Crohn fistulizing disease have largely excluded rectovaginal fistulas. The aim of this study was to determine the safety and efficacy of mesenchymal stem cells for refractory rectovaginal fistulizing Crohn disease. METHODS: A phase IB/IIA randomized control trial was performed in a 3:1, single-blinded study. Patients included were adult women with an anovaginal/rectovaginal fistula in the setting of Crohn disease. Seventy-five million mesenchymal stem cells were administered with a 22G needle after curettage and primary closure of the fistula tract at day 0 and month 3. Adverse and serious adverse events were recorded at post-procedure day 1, week 2, week 6, month 3, month 6, and month 12, along with clinical healing, magnetic resonance imaging, and patient-reported outcomes. RESULTS: A total of 19 patients were enrolled and treated-15 treatment and 4 control. There were no adverse or serious adverse events related to mesenchymal stem cell therapy. At 6 months, 50% of the treatment group and 0% of the control had complete clinical and radiographic healing; 91.7% of the treatment group had improvement at 6 months with only one patient having a lack of response, whereas only 50% of the control group had improvement at 6 months. CONCLUSION: Bone marrow-derived mesenchymal stem cells offer a safe alternative treatment approach for rectovaginal fistulas in the setting of Crohn disease. Complete healing was achieved in half of the patients.

Treatment effect of ex vivo expanded allogeneic bone marrow-derived mesenchymal stem cells for the treatment of fistulizing Crohn's disease are durable at 12 months.

BACKGROUND: Mesenchymal stem cells have been administered via direct injection to treat perianal Crohn's fistulizing disease. We herein sought to determine the safety and durability of treatment response to 12 months with 3 individual phase IB/IIA clinical trials of mesenchymal stem cells for refractory perianal, rectovaginal, and ileal pouch fistulas in the setting of Crohn disease. METHODS: Three phase IB/IIA randomized placebo-controlled single-blinded clinical trials were performed for (1) perianal fistulas, (2) rectovaginal fistula, and (3) ileal pouch in situ with anovaginal and/or perianal fistulas. Bone marrow-derived mesenchymal stem cells (75 million in 7.5 mL) were injected at the time of exam under anesthesia on day 0 and month 3. Outcome measures were adverse events and combined clinical and pelvic magnetic resonance imaging healing at month 6 and month 12. RESULTS: Across all 3 trials, 64 patients were enrolled; 49 were treatment and 15 were control. At 6 months, combined clinical and radiographic healing was achieved in 83.3%, 33.3%, and 30.8% of the perianal, rectovaginal, and pouch fistula treatment cohorts, respectively. At 12 months, the treatment response was durable, with 67.7% of perianal, 37.5% of rectovaginal, and 46.2% of peripouch fistulas maintaining complete clinical and radiographic healing. Two patients in the perianal fistula control cohort achieved combined clinical and radiographic healing at 12 months, whereas 0% of rectovaginal and pouch control patients healed. CONCLUSION: Bone marrow-derived mesenchymal stem cells offer a safe and effective alternative treatment approach for severe perianal, rectovaginal, and peripouch fistulizing Crohn's disease. Treatment results are durable at 12 months.

Local fistula injection of allogeneic human amnion epithelial cells is safe and well tolerated in patients with refractory complex perianal Crohn's disease: a phase I open label study with long-term follow up.

BACKGROUND: Local fistula injection of mesenchymal stromal/stem cells (MSC) is effective for complex perianal Crohn's fistulas but is also expensive and requires specialised facilities for cell revival before administration. Human amnion epithelial cells (hAEC) are non-MSC cells with therapeutic properties. The primary aim of this study was safety of hAEC therapy. Secondary aims included hAEC efficacy, feasibility of the protocol and impact on quality of life. METHODS: A phase I open label study of ten adults with active complex Crohn's perianal fistulas refractory to conventional treatment, including anti-tumour necrosis factor alpha therapy, was undertaken. A single dose of hAEC was injected into the fistula tract(s) after surgical closure of the internal opening(s). Study outcomes were assessed at week 24 with follow up for at least 52 weeks. FINDINGS: Local injection of hAEC was safe, well tolerated and the injection procedure was feasible. Complete response occurred in 4 patients, and a partial response in an additional 4 patients. There was a mean reduction in the Perianal Disease Activity Index of 6.5 points (95% CI -9.0 to -4.0, p = 0.0002, paired t-test), modified Van Assche MRI Index of 2.3 points (95% CI -3.9 to -0.6, p = 0.012, paired t-test) and a mean improvement of 15.8 points (95% CI 4.9 to 26.8, p = 0.010, paired t-test) in quality of life using the Short IBD-Questionnaire in complete responders. INTERPRETATION: Local injection of hAEC therapy for refractory complex perianal fistulising Crohn's disease appears safe, well-tolerated, feasible and demonstrated improvement. Quality of life is improved in those who achieve complete fistula healing. FUNDING: This study was funded by competitive research grant funding from the Gastroenterological Society of Australia Seed Grant 2018.

Comments on: "Mesenchymal stem cells transplantation for perianal fistulas: a systematic review and meta-analysis of clinical trials".

The meta-analysis by Wang et al. (Stem Cell Res Ther 14(1):103, 2023) aims to explore whether mesenchymal stem cells are effective for perianal fistulas. The authors indicated that the difference in cell types, cell sources and cell dosages did not influence mesenchymal stem cells' efficacy, which may not be accurate. I think that local treatment with higher dosages of mesenchymal stem cells seems to not result in a higher healing rate. And, future trials should focus on donor characteristics considering past medical history of further autoimmunity, timely and cost-effective treatment to lighten the optimized therapeutic goals. In the future, it will be interesting to assess the safety and feasibility of injection of fibrin glue combined with mesenchymal stem cells in perianal fistulas.

FISTULIZING PERIANAL CROHN'S DISEASE: IS THE PATIENT'S SEX A BURDEN? A SYSTEMATIC REVIEW.

BACKGROUND: Fistulizing perianal Crohn's disease poses a treatment challenge, and researchers postulate that this phenotype in young male patients could have a worst outcome. OBJECTIVE: Thus, the aim of this study was to assess whether sex influences the response to treatment for these patients. METHODS: This systematic review (PROSPERO CRD42022319629) was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol. We selected articles published in English, Spanish, Portuguese, and Italian between 2010 and 2020 in the PubMed and Science Direct databases. According to the PICO acronym, prospective studies in patients older than 18 years with the objective of treating fistulizing perianal Crohn's disease were selected. Studies in pediatric populations, retrospective, without treatment objectives, and that included only rectovaginal fistulas or a single sex were excluded. Study quality was assessed using the Cochrane risk of bias tool and Newcastle-Ottawa scale. RESULTS: Of the 1887 articles found, 33 were included. Most studies used anti-TNF drugs as treatment (n=11). Ten studies had subgroup analyses; of them, the two studies reporting sex differences used infliximab and adalimumab as treatment and showed that women had a longer fistula closure time than men. CONCLUSION: This systematic review showed that few data corroborate the difference between sexes in the treatment of fistulizing perianal Crohn's disease, possibly having a greater relationship with the phenotype. However, considering the lack of results, further studies with this objective and with standardization of fistulas and response assessment methods are needed.

The history of Crohn's perianal fistula treatment with mesenchymal stem cells: the story of darvadstrocel.

INTRODUCTION: This study provides an overview of the development of the first drug authorized for use in cell therapy. AREAS COVERED: We analyze the case of darvadstrocel, an example of a successful cell-therapy drug used worldwide to treat Crohn's perianal fistula. A bibliographic-historical analysis of the first cellular treatment approved by the EMA, including relevant aspects concerning the authors, who were involved in the whole process. We would like to highlight the following messages: Development: The article describes the development process of the drug, from initial concept through the clinical trial phases. Learning from failure: In describing the development of darvadstrocel, the authors highlight the importance of learning from failures, which is crucial to achieving successful outcomes. Collaboration: The article underscores the need for collaboration between public and private institutions to facilitate the advancement of cell-therapy drugs and ensure efficiency while adhering to regulatory guidelines. EXPERT OPINION: Regulatory requirements play a crucial role in the design and development of advanced therapies such as cell-therapy drugs. The findings of this study underscore the significance of appropriate disease application, meticulous donor selection, robust manufacturing processes, and proper therapy administration. Only by adopting these measures can cell-therapy drugs successfully complete all phases of the clinical trial process.

Allogenic stem cells for Crohn's anal fistulas: Treating early improves the deep remission rate.

AIM: The aim of this study was to evaluate the real-life clinical and radiological efficacy of darvadstrocel injection into complex perianal fistulas in Crohn's disease. Secondary endpoints were to assess symptomatic efficacy, adverse effects and factors associated with complete combined clinical-radiological response (deep remission). METHODS: After marketing the product in France, all first patients treated consecutively were included. A complete clinical response was defined by a complete closure of all external openings with no discharge on pressure. A complete radiological response (MRI), evaluated at least after six months of follow-up, was defined by a completely fibrotic sequela without abscess. A deep remission was defined as the association of a complete clinical response with a complete radiological response. RESULTS: A total of 43 patients were included (M/F: 22/21, median age 37 [26-45] years). The fistulas were already drained with seton(s) and were on biologic treatment. After a median follow-up of 383 (359-505) days, 28 (65%) patients showed a clinical response (22 complete and 6 partial) and 16 (37%) achieved a deep remission. The Perineal Disease Activity Index decreased significantly after treatment: 39 (91%) patients reported symptomatic improvement in terms of discharge, pain, and induration, and 28 (65%) no longer had any perineal symptoms. No severe adverse events were reported. A short history of Crohn's disease <3 years was significantly associated with deep remission (OD 4.5 [1.0-19.1], p = 0.04). CONCLUSION: Darvadstrocel injection resulted in a clinical response for two thirds of patients and deep remission for one third. A shorter duration of Crohn's disease was associated with deep remission.

Efficacy and safety of allogeneic umbilical cord-derived mesenchymal stem cells for the treatment of complex perianal fistula in Crohn's disease: a pilot study.

OBJECTIVES: The aim of the study was to evaluate the efficacy and safety of allogeneic umbilical cord-derived mesenchymal stem cells (TH-SC01) for complex perianal fistula in patients with Crohn's disease (CD). METHODS: This was an open-label, single-arm clinical trial conducted at Jinling Hospital. Adult patients with complex treatment-refractory CD perianal fistulas (pfCD) were enrolled and received a single intralesional injection of 120 million TH-SC01 cells. Combined remission was defined as an absence of suppuration through an external orifice, complete re-epithelization, and absence of collections larger than 2 cm measured by magnetic resonance imaging (MRI) at 24 weeks after cell administration. RESULTS: A total of 10 patients were enrolled. Six patients (60.0%) achieved combined remission at 24 weeks. The number of draining fistulas decreased in 9 (90.0%) and 7 (70.0%) patients at weeks 12 and 24, respectively. Significant improvement in Perianal Crohn Disease Activity Index, Pelvic MRI-Based Score, Crohn Disease Activity Index, and quality of life score were observed at 24 weeks. No serious adverse events occurred. The probability of remaining recurrence-free was 70% at week 52. CONCLUSION: The study demonstrated that local injection of TH-SC01 cells might be an effective and safe treatment for complex treatment-refractory pfCD after conventional and/or biological treatments fail (ClinicalTrials.gov ID, NCT04939337). TRIAL REGISTRATION: The study was retrospectively registered on www. CLINICALTRIALS: gov (NCT04939337) on June 25, 2021.

Natural course of perianal abscess in infants: a real-world study.

Natural course of perianal abscess (PA) in infancy remains obscure. This study aimed to investigate the natural course of infants with PA after conservative treatment. A retrospective cohort study was conducted in infants with PA who were treated conservatively (due to the parents' refusal of surgery), for more than 2 months between 2014 and 2020 at a single tertiary center. 153 patients (149 boys and 4 girls) were identified. The median follow-up was 5.3 years (range 3-8.2 years). Initially, 119 patients (77.8%) were completely cured by conservative treatment, and 34 (22.2%) failed. Among the 34 patients, 23 continued conservative treatment (20 cure, 3 fistula formation) and 11 underwent surgery. After conservative treatment, the rate of fistula formation, abscess recurrence, and new-onset abscess were 15.0%, 4.6%, and 6.5%, respectively. Overall, 139 patients (90.8%) were cured conservatively without surgery, and 11 (7.2%) underwent surgical management. In addition, 3 (2.0%) patients developed fistula-in-ano (under observation). PA in infants may be a time-limited and self-limited condition. Conservative management should be the first choice of treatment in most cases. Longer periods of conservative treatment may achieve better clinical outcomes in selected cases. There will be a percentage of patients (about 10%) that would require surgical treatment.

A Phase I Study of Ex Vivo Expanded Allogeneic Bone Marrow-Derived Mesenchymal Stem Cells for the Treatment of Pediatric Perianal Fistulizing Crohn's Disease.

BACKGROUND: Perianal fistulizing Crohn's disease is notoriously difficult to treat. Recent studies of mesenchymal stem cells have demonstrated safety and efficacy of this novel treatment approach. However, no studies to date have included pediatric patients. We sought to determine safety and efficacy of mesenchymal stem cells for pediatric perianal fistulizing Crohn's disease. METHODS: This was a phase I clinical trial to evaluate safety and feasibility of mesenchymal stem cells in pediatric perianal Crohn's patients 13 to 17 years of age. At the time of an exam under anesthesia, following curettage of the fistula tract and closure of the internal opening with absorbable suture, 75 million mesenchymal stem cells were administered with a 22-gauge needle. This was repeated at 3 months if complete clinical and radiographic healing were not achieved. Adverse and serious adverse events at were measured at postprocedure day 1, week 2, week 6, month 3, month 6, and month 12. Clinical healing, radiographic healing per magnetic resonance imaging, and patient-reported outcomes were measured at the same time points. RESULTS: Seven pediatric patients were enrolled and treated (6 male; median age of 16.7 years). There were no adverse or serious adverse events related to the investigational product or injection procedure. At 6 months, 83% had complete clinical and radiographic healing. The perianal Crohn's Disease Activity Index, Wexner incontinence score, and Van Assche score had all decreased at 6 months. CONCLUSIONS: Bone marrow-derived mesenchymal stem cells offer a safe, and likely effective, treatment approach for pediatric perianal fistulizing Crohn's disease.

[Management of secondary lesions in ano-perineal Crohn's disease]. / Prise en charge des lésions secondaires de la maladie de Crohn anopérinéale.

MANAGEMENT OF SECONDARY LESIONS IN ANO-PERINEAL CROHN'S DISEASE. Anoperineal involvement in Crohn's disease is common and affects around 1/3 of patients during their disease. It constitutes a pejorative factor with an increased risk of permanent colostomy and proctectomy and is associated with a major deterioration in quality of life. Secondary anal lesions in Crohn's disease are fistulas and abscesses. They are difficult to treat and often recurrent. A multidisciplinary medico-surgical management in several stages is essential. The classic sequence is based on a first phase of drainage of fistulas and abscesses, a second phase of medical treatment based primarily on anti-TNF alpha and finally a third phase of surgical closure of the fistula tract(s). Conventional closure techniques such as biologic glue, plug, advancement flap and intersphincteric ligation of the fistula tract have limited effectiveness, are not always feasible, require technical skills and some have an impact on anal continence. In recent years, we have witnessed a real enthusiasm generated by the arrival of cell therapy. This has not spared proctology since adipose-derived allogeneic mesenchymal stem cells have had Marketing Authorisation and have been reimbursed in France since 2020 in the treatment of complex anal fistulas in Crohn's disease after failure of at least one biologic therapy. This new treatment offers an additional alternative in patients often in a situation of therapeutic impasse. Preliminary results in real life are satisfactory with a good safety profile. However, it will be necessary to confirm these results in the longer term and to work to determine the profile of the patients who could benefit the most from this expensive therapy.

PRISE EN CHARGE DES LÉSIONS SECONDAIRES DE LA MALADIE DE CROHN ANOPÉRINÉALE. L'atteinte anopérinéale de la maladie de Crohn est fréquente ; elle affecte environ un tiers des patients durant leur maladie. Elle constitue un facteur péjoratif responsable d'une majoration du risque de colostomie définitive et de proctectomie, et est associée à une altération majeure de la qualité de vie. Les lésions anales secondaires de la maladie de Crohn sont des fistules et des abcès. Elles sont difficiles à traiter et souvent récidivantes. Une prise en charge multidisciplinaire médico-chirurgicale en plusieurs étapes s'impose. La séquence classique se fonde sur une phase de drainage des fistules et des abcès, une phase de traitement médical fondé en priorité sur les anti-TNF alpha et enfin une phase de fermeture chirurgicale du (ou des) trajet(s) fistuleux. Les techniques de fermeture classiques comme la colle biologique, le plug, le lambeau d'avancement et la ligature intersphinctérienne du trajet fistuleux ont une efficacité limitée, ne sont pas toujours réalisables, nécessitent des compétences techniques et ont, pour certaines, un impact sur la continence anale. Ces dernières années, l'arrivée de la thérapie cellulaire suscite un véritable enthousiasme. Cet engouement n'a pas épargné la proctologie, puisque les cellules souches mésenchymateuses (CSM) allogéniques d'origine adipocytaires ont obtenu une autorisation de mise sur le marché (AMM), sont commercialisées et remboursées en France depuis 2020 dans le traitement des fistules anales complexes de la maladie de Crohn en échec d'au moins une biothérapie. Cette thérapie offre une alternative supplémentaire à des patients souvent en situation d'impasse thérapeutique. Les résultats préliminaires en vraie vie sont satisfaisants, avec un bon profil d'innocuité. Toutefois, il faudra confirmer ces résultats à plus long terme et travailler à identifier le profil des patients qui pourraient bénéficier au mieux de cette thérapie onéreuse.

The efficacy of porcine dermal collagen to treat complex anal fistulae: results of a multicenter cohort

Introduction: The management of complex anal fistulae remains a topical surgical problem. The choice and success of surgical management are based on the balance between healing and continence. Although porcine dermal collagen (Permacol Collagen Paste [PCP]- Covidien plc, Gosport, Hampshire, UK) represents a new generation of non-solid biomaterials, its results in anal fistulae are mixed. Methods: A multicenter observational retrospective analysis of consecutive patients with cryptoglandular anal fistula treated in four colorectal surgery units was performed between 2015 and 2020. Clinical cure of the fistula was the main outcome measure. Adverse events and alterations in anal continence were secondary outcomes. Results: The study included 119 patients (87 males, 71.1%), with a mean age of 53 years (IR 44-65). Most patients had complex (80.6%) and recurrent (91.6%) fistulae. With the first PCP treatment, the overall cure rate was 41.2% (49 patients) and 45.4% with the second treatment (5 out of 17 patients). The mean follow-up period was 17 months (IR 5-25). Healing was not affected by the location and type of fistula, the existence or not of a cavity, the number of tracts, or the administration of prophylactic antibiotics. After the PCP treatment, no patient in the series had worsening of continence. Morbidity affected 22.7% of the patients (27), with postoperative abscesses being the most frequent adverse event. There were no statistical differences between the four hospitals studied. Conclusions: Permacol collagen paste is a safe and easily reproducible therapy for complicated anal fistulae that has moderate efficacy. The overall success rate is slightly over 40%, with no detriment to fecal continence. (AU)

Management of Perianal Crohn's Disease.

Perianal Crohn's disease affects 25%-35% of patients with Crohn's disease and has proven to be one of the most difficult complications of the disease to treat. Patients with perianal Crohn's disease have lower health-related quality of life scores typically related to pain and fecal incontinence. In addition, patients with perianal Crohn's disease have higher rates of hospitalizations, surgeries, and overall healthcare costs. A multidisciplinary approach is necessary for the successful management of Crohn's disease with perianal fistula. Medical management is required to treat the underlying immune dysregulation to heal the luminal inflammation and the inflammation within the fistula tracts. Current options for medical therapy include biologics, dual therapy with thiopurines, therapeutic drug monitoring, and a close follow-up. Surgical management is critical to drain abscesses before immunosuppressive therapy and place setons when appropriate. Once the patient's inflammatory burden is well managed, definitive surgical therapies including fistulotomies, advancement flaps, and ligation of intersphincteric fistula tract procedures can be considered. Most recently, the use of stem cell therapy in the treatment of perianal fistula has given new hope to the cure of perianal fistula in Crohn's disease. This review will outline the most current data in the medical and surgical management of perianal Crohn's disease.

Mesenchymal stem cells transplantation for perianal fistulas: a systematic review and meta-analysis of clinical trials.

BACKGROUND: Perianal fistulas, characterised as granulomatous inflammation of fistulas around the anal canal, are associated with significant morbidity resulting in a negative impact on quality of life and a tremendous burden to the healthcare system. Treatment of anal fistulas usually consists of anal surgery; however, results of closure rates are not satisfactory especially with complex perianal fistulas, after which many patients may suffer from anal incontinence. Recently, the administration of mesenchymal stem cells (MSCs) has shown promising efficacy. Herein, we aim to explore whether MSCs are effective for complex perianal fistulas and if they have either short-term, medium-term, long-term or over-long-term efficacy. Additionally, we want to elucidate whether factors such as drug dosage, MSC source, cell type, and disease aetiology influence treatment efficacy. We searched four online databases and analysed data based on information within the clinical trials registry. The outcomes of eligible trials were analysed with Review Manager 5.4.1. Relative risk and related 95% confidence interval were calculated to compare the effect between the MSCs and control groups. In addition, the Cochrane risk of bias tool was applied to evaluate the bias risk of eligible studies. Meta-analyses showed that therapy with MSCs was superior to conventional treatment for complex perianal fistulas in short-, long- and over-long-term follow-up phases. However, there was no statistical difference in treatment efficacy in the medium term between the two methods. Subgroup meta-analyses showed factors including cell type, cell source and cell dosage were superior compared to the control, but there was no significant difference between different experimental groups of those factors. Besides, local MSCs therapy has shown more promising results for fistulas as a result of Crohn's Disease (CD). Although we tend to maintain that MSCs therapy is effective for cryptoglandular fistulas equally, more studies are needed to confirm this conclusion in the future. SHORT CONCLUSION: MSCs Transplantation could be a new therapeutic method for complex perianal fistulas of both cryptoglandular and CD origin showing high efficacy in the short-term to over-long-term phases, as well as high efficacy in sustained healing. The difference in cell types, cell sources and cell dosages did not influence MSCs' efficacy.

Clinical and MRI Evolution After Local Injection of Bone Marrow-Derived Mesenchymal Stem Cells in Perianal Fistulae in Crohn's Disease: Results From a Prospective Monocentric Study.

BACKGROUND: Local injection of adipose tissue-derived mesenchymal stem cells [MSCs] is effective in fistulizing perianal Crohn's disease [CD]. Less is known about bone marrow-derived MSCs and little is known about predictive factors of response and magnetic resonance imaging [MRI] evolution of the fistulae after MSC injection. Our aims were to evaluate the safety and clinical outcome of bone marrow-derived MSC injection for perianal fistulizing CD, to evaluate the MRI evolution of the fistulae and to identify factors associated with fistula closure. PATIENTS AND METHODS: All CD patients with perianal fistula and appropriate drainage with a seton without abscess at MRI were eligible. Clinical examination, biomarkers and pelvic MRI were performed at weeks 0, 12 and 48. The clinical outcome was assessed by closure of the treated external openings at clinical examination and MRI exploration. RESULTS: Sixteen patients with a median age of 49 years and a median duration of perianal CD of 8 months were included. No unexpected safety event occurred. At weeks 12 and 48, 9/16 and 8/16 patients had complete fistula[e] closure, respectively, whereas 11/16 patients had at least partial closure. At MRI, the degree of fibrosis increased significantly after MSC injection. In total, 86% of patients with >80% of fibrosis of the fistula tract at week 48 had fistula closure. Fistula closure at week 12 was predictive of fistula closure at week 48. The MAGNIFI-CD did not change significantly over time. CONCLUSION: Open-label injection of bone marrow-derived MSCs was safe and was effective in half of the patients in fistulizing perianal CD and induced significant MRI changes associated with favourable clinical outcome.