Intra-Articular Application of Umbilical Cord-Derived Stem Cells in Patients with Chronic Shoulder Pain

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This retrospective pragmatic observational study investigates the safety and short-term effectiveness of umbilical cord-derived mesenchymal stem cell injections for patients suffering from chronic shoulder pain. The research measured functional outcomes using the ASES score. 

The following points need clarifying prior to publication:

The study is limited by a very small sample of 20 patients selected through non-probability convenience sampling. This significantly reduces the statistical power and the generalizability of the findings to broader populations. 

As a retrospective study without a control arm, it is impossible to determine the extent to which the observed improvements were influenced by the placebo effect, the natural history of the condition, or concurrent lifestyle changes. The authors correctly acknowledge this as a limitation, but should discuss at length.

The three-month follow-up is insufficient to assess the long-term durability of UC-MSC therapy. Chronic musculoskeletal conditions often require longer observation periods to determine if the regenerative effects are sustained or if further intervention is required.

The study relies exclusively on patient-reported functional scores. Without pre- and post-treatment imaging (such as MRI or ultrasound), the authors cannot provide objective evidence of structural tissue repair or regeneration, such as tendon healing or cartilage restoration.

Patients received doses ranging from 5.5 to 38.6 million cells, based on individual needs. While the secondary regression model suggests a positive dose-response relationship, this wide variability makes it difficult to establish a standardized treatment protocol.

Author Response

We thank the reviewer for the careful evaluation of our manuscript and for the constructive comments, which have helped us improve the clarity, transparency, and scientific rigor of the study. Each point is addressed in detail below.

Comment 1: The study is limited by a very small sample of 20 patients selected through non-probability convenience sampling, reducing statistical power and generalizability.

Response:
We agree with the reviewer that the small sample size and the use of non-probability convenience sampling are important limitations of this study. As clarified in the revised Discussion section, this cohort represents the entire population of patients treated for chronic shoulder pain at our institution during the defined study period, rather than a selectively recruited sample. Consequently, the study was not designed to provide population-level estimates or definitive comparative efficacy.

The primary objective was exploratory and pragmatic: to evaluate short-term safety signals and preliminary clinical effectiveness in a real-world clinical setting. While statistical power is inherently limited, we mitigated this constraint by reporting effect sizes, confidence intervals, and clinically meaningful change (MCID), which provide complementary information beyond p-values. These measures suggest a large within-subject effect despite the small sample.

We now explicitly emphasize that the findings should be interpreted as hypothesis-generating and that larger, prospectively powered studies are required before generalizing results to broader patient populations.

Comment 2:  As a retrospective study without a control arm, it is impossible to determine the influence of placebo effects, natural history, or lifestyle changes.

Response:
We fully acknowledge this limitation and have expanded the Discussion to address it more thoroughly. The absence of a control group precludes causal inference and prevents isolation of the treatment effect from placebo responses, regression to the mean, spontaneous symptom fluctuation, or concurrent lifestyle modifications.

We now explicitly state that the observed improvements in ASES scores cannot be attributed solely to UC-MSC therapy. However, we also note that the magnitude of improvement exceeded the established MCID and was accompanied by a large effect size, suggesting that the changes were clinically meaningful. While this does not eliminate placebo effects, it supports the relevance of the observed functional gains.

We emphasize that these findings should be interpreted within the context of a pragmatic observational design and that randomized controlled trials are essential to disentangle treatment-specific effects from non-specific influences.

Comment 3: A three-month follow-up is insufficient to assess long-term durability in chronic musculoskeletal conditions.

Response:
We agree with this assessment and have clarified this limitation in the revised manuscript. The three-month follow-up was selected because it reflects routine clinical follow-up in our setting and allows assessment of early functional response and short-term safety. However, it does not permit conclusions regarding durability, structural remodeling, or the need for repeat interventions.

We now explicitly state that chronic shoulder pathologies often require longer observation periods and that future studies should incorporate extended follow-up intervals (e.g., 6–24 months) to evaluate the persistence of clinical benefits and potential delayed adverse events.

Comment 4: The lack of imaging prevents objective assessment of structural tissue repair.

Response:
We acknowledge this limitation and have expanded the Discussion accordingly. While the ASES score is a validated and widely used patient-reported outcome measure for shoulder function, it does not provide direct evidence of structural tissue regeneration.

Because this was a retrospective study, standardized pre- and post-treatment imaging (MRI or ultrasound) was not consistently available and therefore could not be analyzed systematically. As a result, we cannot correlate functional improvement with objective markers such as tendon healing, cartilage status, or inflammatory changes.

We now clearly state that the observed functional improvements may reflect symptomatic, biomechanical, or neuromodulatory effects rather than confirmed structural repair, and we highlight the need for future studies integrating imaging and biological biomarkers.

Comment 5:  The wide range of administered cell doses complicates protocol standardization.

Response:
We appreciate this important observation and have clarified the rationale and implications of dose variability. Doses were individualized based on clinical presentation and ultrasonographic findings, reflecting real-world practice rather than a fixed experimental protocol. While this approach increases ecological validity, it also introduces heterogeneity that limits standardization.

We now emphasize that the regression analyses exploring dose–response relationships are exploratory and should not be interpreted as definitive dosing recommendations. Although the secondary model suggested a positive association between higher doses and greater functional improvement, the small sample size and dose variability preclude firm conclusions.

We explicitly state that future prospective studies should employ standardized or stratified dosing regimens to more rigorously define optimal therapeutic ranges.

In response to the reviewer’s comments, we have expanded the Discussion section to more fully address limitations related to sample size, study design, follow-up duration, outcome selection, and dosing variability. We believe these revisions strengthen the manuscript by providing a more balanced interpretation of the findings and clearly positioning the study as preliminary, hypothesis-generating evidence supporting further controlled investigation.

Reviewer 2 Report

Comments and Suggestions for Authors

The intraarticular application of umbilical cord-derived stem cells is a minimally invasive procedure aims to promote tissue repair, reduce inflammation, and alleviate pain using the regenerative and immunomodulatory properties of stem cells. Umbilical cord-derived stem cells are particularly advantageous due to their high proliferative capacity, low immunogenicity, and potential to differentiate into various cell types relevant to joint repair. This therapy is increasingly explored as a promising option for patients suffering from persistent shoulder pain associated with degenerative conditions, traumatic injuries, or inflammatory joint diseases. Therefore? The study of Dr. Soto-Rodriguez et al. is important.

Comments

1. Line 63: Why the authors consider MSC therapy as non-invasive?
2. All the abbreviations should be disclosed on first use. All typos should be corrected.
3. Line 80: The authors should present data on the “quantified doses” for each examined patient.
4. Methods: The authors should describe in detail how the patients received MSC therapy.
5. Section 3.2: As the number of patients was less than 30, the authors should use only non -parametric approach for statistical assessments.
6. Line 227: all the doses used in the study should be disclosed.

Author Response

We thank the reviewer for the detailed and constructive feedback. The comments have helped improve clarity, methodological transparency, and consistency throughout the manuscript. Each point is addressed below.

Comment 1 (Line 63): Why do the authors consider MSC therapy non-invasive?

Response:
We appreciate this observation. The term non-invasive was used to distinguish the procedure from open or arthroscopic surgical interventions rather than to imply the absence of needle-based intervention. To avoid ambiguity, we have revised the wording throughout the manuscript to describe the procedure as minimally invasive instead of non-invasive. This change more accurately reflects the intra-articular injection approach used in this study.

 

Comment 2: All abbreviations should be disclosed on first use; typos should be corrected

Response:
We agree and have carefully reviewed the manuscript to ensure that all abbreviations are fully defined at their first occurrence. Additionally, typographical errors and formatting inconsistencies have been corrected throughout the text.

Comment 3 (Line 80): Presentation of “quantified doses” for each patient

Response:
Thank you for this suggestion. Individualized MSC doses were administered based on clinical and ultrasonographic findings. We have now clarified the dosing range in the Methods section and explicitly reported that administered doses on the results. In addition, dose information has been consistently disclosed and referenced in the Results and regression analyses.

Comment 4 (Methods): Description of how patients received MSC therapy

Response:
We agree that additional procedural detail improves transparency and reproducibility. The Methods section has been expanded to provide a more detailed description of the clinical workflow, including pre-procedure ultrasonographic evaluation, injection planning, sedation preferences, intra-articular administration technique, and post-procedure monitoring. This revision clarifies how MSC therapy was delivered in routine clinical practice.

Comment 5 (Section 3.2): Use of non-parametric statistics due to sample size < 30

Response:
We acknowledge the reviewer’s concern. Prior to analysis, the distribution of ASES change scores was formally assessed using the Shapiro–Wilk test, skewness/kurtosis tests, and visual inspection of histograms and Q–Q plots, all of which supported approximate normality. Based on these results, paired t-tests were deemed appropriate.

Nevertheless, to ensure robustness, we also performed non-parametric Wilcoxon signed-rank tests as sensitivity analyses, which yielded consistent results. This approach is now explicitly described in the Statistical Analysis section to clarify that conclusions do not rely solely on parametric assumptions.

Comment 6 (Line 227): Disclosure of all doses used in the study

Response:
We agree and have ensured that all administered doses are clearly disclosed in the manuscript. The full dosing range (7.8–38.6 million cells per joint) is now consistently reported in the, Results section, and dosing variability is discussed as a study limitation.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I am now satisfied with the manuscript and can support publication. 

Reviewer 2 Report

Comments and Suggestions for Authors

I have no more comments.