**Exhibit 31.2.1**

 

**Certification of Principal Financial Officer**

**Pursuant to Section 302 of the Sarbanes-Oxley Act of2002**

 

I, Philip R.Jacoby, Jr., certify that:

 

1.                  I have reviewed this Quarterly Report on Form 10-Q for the period ended June 30,2010 of Osiris Therapeutics, Inc.;

 

2.                  Based on my knowledge, this report does not contain any untrue statement of amaterial fact or omit to state a material fact necessary to make the statementsmade, in light of the circumstances under which such statements were made, notmisleading with respect to the period covered by this report;

 

3.                  Based on my knowledge, the financial statements, and other financialinformation included in this report, fairly present in all material respectsthe financial condition, results of operations and cash flows of the registrantas of, and for, the periods presented in this report;

 

4.                  The registrant’s other certifying officer(s) and I are responsible forestablishing and maintaining disclosure controls and procedures (as defined inExchange Act Rules 13a-15(e) and 15d-15(e)) and internal control overfinancial reporting (as defined in Exchange Act Rules 13a-15(f) and15d-15(f)) for the registrant and have:

 

(a)              Designed such disclosure controls and procedures, or caused such disclosurecontrols and procedures to be designed under our supervision, to ensure thatmaterial information relating to the registrant, including its consolidatedsubsidiaries, is made known to us by others within those entities, particularlyduring the period in which this report is being prepared;

 

(b)              Designed such internal control over financial reporting, or caused suchinternal control over financial reporting to be designed under our supervision,to provide reasonable assurance regarding the reliability of financialreporting and the preparation of financial statements for external purposes inaccordance with generally accepted accounting principles;

 

(c)              Evaluated the effectiveness of the registrant’s disclosure controls andprocedures and presented in this report our conclusions about the effectivenessof the disclosure controls and procedures, as of the end of the period coveredby this report based on such evaluation; and

 

(d)              Disclosed in this report any change in the registrant’s internal control overfinancial reporting that occurred during the registrant’s most recent fiscalquarter (the registrant’s fourth fiscal quarter in the case of an annualreport) that has materially affected, or is reasonably likely to materiallyaffect, the registrant’s internal control over financial reporting; and

 

5.                  The registrant’s other certifying officer(s) and I have disclosed, basedon our most recent evaluation of internal control over financial reporting, tothe registrant’s auditors and the audit committee of the registrant’s board ofdirectors (or persons performing the equivalent functions):

 

(a)              All significant deficiencies and material weaknesses in the design or operationof internal control over financial reporting which are reasonably likely toadversely affect the registrant’s ability to record, process, summarize andreport financial information; and

 

(b)              Any fraud, whether or not material, that involves management or other employeeswho have a significant role in the registrant’s internal control over financialreporting.

 

Date: August 6, 2010

 
|   | /s/ PHILIP R. JACOBY, JR.  |
|--------|----------------------------|
|   | Philip R. Jacoby, Jr. |
|   | Chief Financial Officer    |

 

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