The purpose of this clinical study is to answer the questions:

1. Is the proposed intervention safe?
2. Is the proposed intervention effective in improving the healthy status of subjects with aging frailty?

Aging frailty is a clinical syndrome, characterized by a decrease of homeostatic reserves and enhanced vulnerability to endogenous or exogenous stressors, exposing individuals to an increased risk of adverse health-related outcomes. The human umbilical cord (HUC) is a promising source of mesenchymal stem cells (MSCs), compared to embryonic stem cells, HUC-MSCs are noncontroversial with a painless collection procedure and faster self-renewal properties. HUC-MSCs can differentiate into the different germ layers and modulate immune responses. One possible mechanism for the onset and development of aging frailty is the depletion of stem cells. Hence, intravenous infusion of HUC-MSCs is attractive therapy against aging frailty.

This is a randomized, double-blind, placebo-controlled clinical trial. The participants (n = 30) will be randomly distributed into two groups. The HUC-MSCs Group (n = 15) will receive intravenous infusion of mesenchymal stem cells twice over a month (30 days interval), the Control Group (n = 15) will receive the same protocolized intervention with normal saline. Follow-up duration is 6 months after first intervention. The reported serious adverse events（SAEs）will be observed within one month post infusion. The short-item from health survey（SF-36), EuroQol five dimensions questionnaire (EQ-5D) and Fried phenotype scale will be evaluated. Short physical performance battery (SPPB) and plasm biomarkers will be assessed.The assessments will be performed at baseline, 1 month, 3 months and 6 months.

The intent of this study is to explore domains of efficacy of HUC-MSCs through the reduction of signs and symptoms of aging frailty and to evaluate the safety of HUC-MSCs in subjects with aging frailty.

Inclusion Criteria:

1. Subjects age ≥60 and ≤80 years at the time of signing the informed consent form.
2. Must show signs of frailty apart from a concomitant condition as assessed by the investigator with a frailty score of 1 to 4 using the Fried Phenotype Scale.
3. Must provide written informed consent.
4. Subjects are expected to live more than 12 months.

Exclusion Criteria:

1. Serious comorbid illness that, in the opinion of the investigator, may compromise the safety or compliance of the patient or preclude successful completion of the study
2. Advanced liver or renal failure, class III/IV congestive heart failure, myocardial infarction, unstable angina, cardiac revascularization, or severe obstructive ventilator defect.
3. Uncontrolled hypertension or hyperglycemia.
4. Have known allergies to biological drugs or antibiotics.
5. Expecting to receive organ transplantation.
6. Have a clinical history of malignancy or active autoimmune diseases.
7. Have a history of drug or alcohol abuse within the past 24 months.
8. Be serum-positive for HIV, hepatitis BsAg or viremic hepatitis C.
9. Be currently participating (or participated within the previous 30 days) in an investigational therapeutic or device trial.
10. Be a female who is pregnant, nursing, or of childbearing potential while not practicing effective contraceptive methods.