FORM 4 [X] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).         
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES
                                                                                  
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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940
                      
1. Name and Address of Reporting Person * Spada Alfred P. 2. Issuer Name and Ticker or Trading Symbol Histogen Inc. [ HSTO ] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable)_____ Director                    _____ 10% Owner
__X__ Officer (give title below)    _____ Other (specify below)
EVP, R&D and CSO
(Last)         (First)         (Middle)
C/O HISTOGEN INC., 10655 SORRENTO VALLEY ROAD, SUITE 200
3. Date of Earliest Transaction (MM/DD/YYYY)
5/22/2020
(Street)
SAN DIEGO, CA 92121
(City)       (State)       (Zip)
4. If Amendment, Date Original Filed (MM/DD/YYYY)
 
6. Individual or Joint/Group Filing (Check Applicable Line) _X _ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)
2. Trans. Date 2A. Deemed Execution Date, if any 3. Trans. Code
(Instr. 8)
4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)
5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)
6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V Amount (A) or (D) Price
Common Stock  5/22/2020    M    31343  A $0.00  32555  D   
Common Stock  5/22/2020    F    12960  D $0.56  19595  D   
Common Stock                 24714  I  See footnote (1)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security
(Instr. 3)
2. Conversion or Exercise Price of Derivative Security 3. Trans. Date 3A. Deemed Execution Date, if any 4. Trans. Code
(Instr. 8)
5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)
6. Date Exercisable and Expiration Date 7. Title and Amount of Securities Underlying Derivative Security
(Instr. 3 and 4)
8. Price of Derivative Security
(Instr. 5)
9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Restricted Stock Units   (2) 5/22/2020    M        31343    (3)  (3) Common Stock  31343  $0.00  0  D   

Explanation of Responses:
(1)  Held by a family trust of which Dr. Spada is a trustee.
(2)  Each restricted stock unit represents a contingent right to receive one share of the Issuer's common stock.
(3)  Pursuant to the Agreement and Plan of Merger and Reorganization (the "Merger Agreement") by and among Conatus Pharmaceuticals Inc. ("Conatus"), Chinook Merger Sub, Inc. and Histogen Inc., all outstanding Conatus restricted stock units vested in full and were settled in shares of common stock prior to the closing of the merger contemplated by the Merger Agreement.

Remarks:
All share amounts in this Form 4 reflect the 10 for 1 reverse stock split implemented by Conatus Pharmaceuticals Inc. on May 26, 2020 in connection with the Merger Agreement.

Reporting Owners
Reporting Owner Name / Address
Relationships
Director 10% Owner Officer Other
Spada Alfred P.
C/O HISTOGEN INC.
10655 SORRENTO VALLEY ROAD, SUITE 200
SAN DIEGO, CA 92121


EVP, R&D and CSO

Signatures
/s/ Steven J. Mento, Attorney-in-Fact for Alfred P. Spada 5/27/2020
**Signature of Reporting Person Date
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