The purpose of this study is verify the safety and efficacy of Human Umbilical Cord Mesenchymal Stem Cells (UC-MSC) therapy for patients with Spinocerebellar Ataxia, and in addition, explore the possible mechanisms of UC-MSC therapy in Spinocerebellar Ataxia.

This is a random, open label, and parallel controled experiment. 45 patients are selected and sign consent forms, then divided into three groups. Doctors collect the basic information of patient (including age,height, mental condition, vital sign, history of disease, pharmaco-history, genotype test, and so on.) All patients receive laboratory and image examination as baseline. Then, they will give cell treatment based on the clinical protocol. Doctors have follow-up visit on 1, 2, 3, 6, and 12 months after treatment, and do efficacy evaluation.

Inclusion Criteria:

• Clinical and genomic test diagnoses as spinocerebellar ataxias (SCA) (include SCA 1, SCA 2, SCA 3, SCA 6), SARA (Scale for Assessment and Rating of Ataxia) score is 2-5, can complete 8-meter walking test（8MW）
• Do not receive stem cells treatment in 6 months
• Participants sign the consent form based on the experiment process and statement

Exclusion Criteria:

• Cardiac, renal, hepatic insufficiency; total bilirubin is 1.5 times higher than normal value, aspartate transaminase（AST）or alanine aminotransferase（ALT）is 2.5 times higher than normal value
• Hemogram: total white blood cells <3.0 * 10^9 cells/L, blood platelet <75 * 10^9/L, hemoglobin <100g/L
• pneumonia, or severe infection
• With severe allergic history
• Brain organic disorder, like brain tumor
• Serum with HIV, syphilis antibody positive
• Severe mental disease, cognitive disorder patients
• Other severe system or organ organic disease
• Pregnant, breast feeding, or planning pregnant women
• Participate other clinical experiments in 3 months
• With some other conditions that doctor propose not to participate