Comparative Efficacy of Autologous Hematopoietic and Mesenchymal Stem Cell Transplantation in Patients with Systemic Sclerosis: A Systematic Review

<b>Background/Objectives</b>: Systemic sclerosis (SSc) is a rare and severe autoimmune disease with limited treatment options. Autologous hematopoietic stem cell transplantation (HSCT) and mesenchymal stem cell transplantation (MSCT) have emerged as promising therapeutic strategies, especially for patients with refractory or rapidly progressive forms of the disease. However, no comparative synthesis has yet evaluated the clinical outcomes, safety, and applicability of these two distinct stem-cell-based interventions. This systematic review aimed to perform a comparative qualitative synthesis of clinical outcomes, safety profiles, and evidence quality for HSCT and MSCT in patients with systemic sclerosis, focusing on survival, skin fibrosis, pulmonary function, and adverse events. <b>Methods</b>: A comprehensive search was conducted in PubMed, ScienceDirect, Cochrane Library, and Google Scholar for the period between 2015 and May 2025. Studies were included if they reported on adult patients with a confirmed diagnosis of SSc treated with either autologous HSCT or MSCT and provided clinical outcome data. Risk of bias was assessed using the Newcastle-Ottawa Scale. Due to heterogeneity across studies, results were synthesized qualitatively. <b>Results</b>: Eleven studies met the inclusion criteria, comprising 504 patients (316 HSCT, 188 MSCT). HSCT showed consistent improvement in survival (1-, 5-, and 10-year), reduction in modified Rodnan skin scores (mRSS), and s ilization or improvement in pulmonary function (DLCO, FVC), albeit with a higher incidence of serious adverse events, including transplant-related mortality (up to 10%) and infectious complications. MSCT demonstrated favorable effects on skin fibrosis and lung involvement with a significantly lower toxicity profile. However, long-term survival data and methodological robustness were limited were more limited. HSCT was supported by multiple randomized controlled trials and international guidelines, while MSCT remains under clinical investigation with promising but still preliminary evidence. <b>Conclusions</b>: Both HSCT and MSCT demonstrate potential clinical benefits in systemic sclerosis, but they differ substantially in evidence strength and risk profiles. HSCT provides the most robust evidence for long-term disease modification in carefully selected patients, whereas MSCT represents a promising and safer investigational option, particularly for patients ineligible for intensive therapy. Further well-designed comparative studies are required to define their optimal clinical roles.